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Instructional Course Lectures, The American Academy of Orthopaedic Surgeons - Common Complications of Total Knee Arthroplasty*

DAVID C. AYERS, M.D., SYRACUSE, NEW YORK, DOUGLAS A. DENNIS, M.D., DENVER, COLORADO, NORMAN A. JOHANSON, M.D.¶, PHILADELPHIA and VINCENT D. PELLEGRINI, JR., M.D.,#, HERSHEY, PENNSYLVANIA

An Instructional Course Lecture, The American Academy of Orthopaedic Surgeons

	Introduction

Top Introduction Wound Complications Neurovascular Complications Infection Thromboembolic Disease Problems Related to the... Stiffness Supracondylar Fracture of the... References

 
The success of a total joint arthroplasty is contingent on a clear understanding of the potential complications of the procedure. This Instructional Course Lecture presents a review of specific problems related to wound-healing, neurovascular injuries, infections, thromboembolic disease, the extensor mechanism, stiffness, and periprosthetic fractures to provide the reader with a clear understanding of ways to avoid and treat these common complications.

	Wound Complications

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Primary wound-healing is critical for the success of any total knee arthroplasty. Any delay in wound-healing increases the risk of infection and failure of the arthroplasty^214,216. The prevention of soft-tissue problems through the selection of the proper skin incision, an understanding of the vascular anatomy and patient-related risk factors, and prompt treatment of wound problems (should they arise) are imperative if a good result is to be achieved.

Vascular Anatomy
The blood supply to the soft tissues of the anterior aspect of the knee is completely random, with contributions from multiple vessels^{2,23,43,161,203,258,295}. This blood supply arises predominantly from the terminal branches of the peripatellar anastomotic arterial ring, which has numerous contributing arterial branches, including the medial and lateral superior genicular arteries, the medial and lateral inferior genicular arteries, the supreme genicular artery, the anterior tibial recurrent artery, and a branch of the profunda femoris artery. In contrast to the skin circulation of the thigh proximal to the knee, there is no underlying muscle or intermuscular septum directly anterior to the knee to provide a direct pathway for arterial perforators^43,161. Skin circulation in this area is dependent on the dermal plexus, which originates directly from arterioles traveling within the subcutaneous fascia. Any operative dissection performed superficial to this subcutaneous fascia disrupts the arterial supply to the skin and increases the possibility of skin necrosis. Elevation of skin flaps about the anterior aspect of the knee requires dissection deep to the subcutaneous fascia to preserve the perforating arteriolar network between the subcutaneous fascia and the dermal plexus¹⁶¹.

Choice of Skin Incision
An analysis of the vascular anatomy about the knee suggests that the choice of a midline skin incision is less disruptive to the arterial network¹⁶¹. A medial peripatellar skin incision is undesirable as it creates a large, laterally based skin flap, which has been associated with higher rates of wound complications¹⁶¹. Measurements of transcutaneous oxygen, performed both before and after skin incisions about the knee, have demonstrated reduced oxygenation of the skin in the lateral region^146,150. The farther medially the skin incision is made, the larger the lateral skin flap and the greater the risk of wound complications. Placement of the skin incision slightly lateral to the midline assists in eversion of the patella, particularly in obese patients in whom a large and bulky lateral skin flap resists patellar eversion.

Use of a pre-existing skin incision generally is recommended. Although it usually is safe to ignore previous short medial or lateral peripatellar incisions^64,308, one should be wary of wide scars with thin or absent subcutaneous tissue as damage to the underlying dermal plexus is likely and the risk of wound necrosis therefore is increased¹⁶¹.

If there are long, parallel scars, the lateralmost incision should be used to avoid the creation of a large lateral skin flap containing an operative scar. In complex situations—for example, when there are multiple incisions or areas of previously burned or irradiated skin—it is wise to consult with a plastic surgeon, both with regard to the design of the impending skin incision and for consideration of preoperative muscle-flap procedures if the risk of skin necrosis is substantial. In selected complex situations, the risk of wound problems can be reduced with use of a staged technique. Before the total knee arthroplasty, a skin incision is made to the depth of the subcutaneous fascia and then is closed. If this incision heals without difficulty, the surgeon can proceed with the total knee replacement through this incision with much greater confidence²⁵⁰.

Soft-tissue expansion has been used successfully to treat soft tissues that are contracted because of previous skin incisions, irradiation, or burns^{7,83,186,188,189,220,241}. This procedure involves implantation, usually subcutaneously, of an expandable reservoir into which saline solution is injected intermittently to expand the surface area. Studies have shown that epidermal thickness is maintained when this technique is used^6,298. While some dermal thinning occurs, the synthesis of dermal collagen actually increases. Complications associated with soft-tissue expansion have been minimum but have included hematoma formation, deflation of the reservoir, infection, and skin necrosis due to overly vigorous soft-tissue expansion.

Technical Factors
A thorough preoperative vascular examination of the limb is necessary to minimize the risk of difficulties related to wound-healing. The skin incision should be of adequate length to avoid excessive tension on the wound edges, particularly when the knee is fully flexed. Gentle retraction of the skin edges is necessary to avoid disruption of perforating arterioles originating in the subcutaneous fascia. It is best to avoid undermining large areas of skin. If a flap is to be used, it must be created in the subfascial plane to preserve the blood supply to the skin that originates in the dermal plexus^43,161. Numerous studies have demonstrated that a lateral retinacular release decreases oxygenation of the skin in the lateral region and increases the subsequent risk of wound complications^{37,149,158,270}. If a lateral retinacular release is to be performed, an attempt should be made to preserve the lateral superior genicular artery. Meticulous wound hemostasis is required to avoid the creation of a postoperative hematoma. Routine use of suction drainage in total knee arthroplasty has been questioned^12,238. We have found that increased pain, postoperative ecchymosis, and drainage occur without a drain; therefore, we recommend the routine use of such a device. Finally, a layered wound closure without tension is imperative to minimize the risk of skin necrosis.

Patient-Related Risk Factors
Numerous reports have suggested that chronic use of corticosteroids increases the prevalence of difficulties related to wound-healing^{42,102,161,185,206,213,271,294,301}. Use of corticosteroids has been shown to decrease fibroblast proliferation, which is necessary for proper wound-healing¹⁰², and to reduce collagenase clearance from the healing wound^294,301. This results in diminished accumulation of collagen, and a subsequent decrease in tensile strength, at the site of wound-healing^42,294,301. An increased prevalence of wound complications among patients who have rheumatoid arthritis has been well documented. Although the specific cause of this association is not known, it may be related to the increased long-term use of corticosteroids by many of these patients^{48,90,104,216,284,306,311}.

An increased prevalence of wound complications also has been noted among obese patients^{45,63,206,306}. Extreme obesity can create difficulties with exposure during total knee arthroplasty, thereby necessitating more vigorous retraction of skin flaps. Additionally, in heavier patients, who have a thick layer of adipose tissue, the skin is less adherent to its underlying vascular supply, and this increases the chances that the dermis will separate from the subcutaneous layer during skin retraction¹⁶¹.

Malnutrition, represented by an albumin level of less than 3.5 grams per deciliter (thirty-five grams per liter) and a total lymphocyte count of less than 1500 cells per cubic millimeter, has been associated with poor healing of the stump after a Syme amputation and may play a role in wound-healing after a total knee arthroplasty^54,63. The damaging effects of cigarette-smoking have been well documented and probably are related to systemic vasoconstriction resulting from the use of nicotine^{17,44,157,202,236}. While the exact relationship is unclear, the increased frequency of wound problems in patients who have diabetes mellitus may be secondary to delayed collagen synthesis and decreased tensile strength at the site of the wound. Early capillary growth into the healing wound also is reduced^{63,97,98,161,184}. High-dose non-steroidal anti-inflammatory drugs inhibit the acute inflammatory response, which is an important step in the early phases of wound-healing¹⁸⁰. Patients managed with chemotherapy similarly may be at risk for delayed wound-healing. The routine need to discontinue methotrexate preoperatively for patients who have rheumatoid arthritis is unclear. Bridges et al.²⁹ found a slight increase in the prevalence of infection in ten patients managed with methotrexate perioperatively compared with the prevalence in patients who had stopped using methotrexate more than one month preoperatively. Other, larger comparison studies have demonstrated no increase in the prevalence of complications related to wound-healing in association with the continued perioperative administration of methotrexate in patients who have rheumatoid arthritis^154,213.

Normovolemic vascular status is necessary for satisfactory wound-healing. Hypovolemia can delay wound-healing because of reduced delivery of oxygen to the healing soft tissues^42,44,161. Reduction in the level of transcutaneous oxygen has been found to increase the prevalence of wound-healing complications in patients managed with lateral retinacular release during total knee arthroplasty¹⁴⁹ and to decrease the rate of wound-healing after soft-tissue-flap transfers³. With use of continuous passive motion, flexion of the knee to 40 degrees or more reduces oxygen tension in the healing wound edges, especially during the initial three days after a total knee arthroplasty. Continuous passive motion should be limited to less than 40 degrees in the early postoperative period^95,147.

Treatment of Wound Complications
Various types of wound complications can occur, including prolonged postoperative drainage; superficial soft-tissue necrosis; and full-thickness soft-tissue necrosis, which usually results in exposure of the prosthetic components. All three types of wound problems require immediate attention, as any delay in treatment increases the risk of deep infection and subsequent failure of the total knee arthroplasty.

Prolonged Serous Drainage
If the wound is chronically draining but does not exhibit substantial erythema or purulence, immobilization and local wound care can be attempted. In our experience, drainage that persists for more than five to seven days despite immobilization and local wound care is unlikely to cease spontaneously and is an indication for open débridement. Subcutaneous hematomas or large intra-articular hemarthroses commonly are encountered in association with such persistent wound drainage. Hematomas threaten the wound because they increase soft-tissue tension, release toxic products of hemoglobin breakdown, and serve as a favorable medium for bacterial growth¹⁶¹. We are aware of no scientific data that clearly support open drainage rather than observation of a non-draining hematoma; therefore, we recommend that a non-draining hematoma be treated non-operatively with close observation as long as there are no signs of impending skin necrosis due to excessive soft-tissue tension. An additional indication for open drainage is a large hematoma that is contributing to a substantial limitation of the range of motion of the knee. Drainage procedures should be performed in the operating theater with perioperative antibiotic prophylaxis.

The prevalence of prolonged drainage among patients in whom a culture-proved infection eventually developed at the site of a total knee arthroplasty has ranged from 17 to 50 per cent^{15,104,110,136,172,299}; in the study by Bengtson et al.¹⁵, for example, persistent drainage was noted in twenty-six (51 per cent) of fifty-one knees. Weiss and Krackow²⁹⁹, in a retrospective review of the results of 597 total knee arthroplasties, reported that eight (1.3 per cent) were followed by persistent wound drainage. All eight patients were managed with open irrigation and débridement and parenteral administration of antibiotics, and all had healing without infection despite the fact that two had a positive culture at the time of irrigation and débridement. Bengtson et al.¹⁵ suggested that prompt operative intervention may prevent chronic drainage from becoming an established infection.

Superficial Soft-Tissue Necrosis
Although small necrotic areas that are less than three centimeters in diameter may heal with local wound care or delayed secondary closure²⁷¹, necrotic tissue generally necessitates operative débridement. Larger areas of superficial necrosis should be debrided and covered with a split-thickness skin graft or a fasciocutaneous flap^110,172.

Full-Thickness Soft-Tissue Necrosis
Full-thickness soft-tissue necrosis usually is associated with the exposure of prosthetic components and necessitates immediate, extensive débridement. Simple secondary closure often is unsuccessful, and reconstruction with some type of flap usually is necessary. Various types of flaps—including cutaneous¹⁷³, fasciocutaneous^110,172, and myocutaneous flaps^{16,62,91,103,114,173,253,255}—have been used. Bengtson et al.¹⁶ reported on the treatment of full-thickness skin loss that had resulted in exposure of the prosthetic components after ten total knee arthroplasties. Delayed closure failed in all six knees in which it was attempted, and split-thickness skin-grafting failed in both of the knees in which it was utilized. In contrast, coverage with a gastrocnemius myocutaneous flap proved to be successful and was recommended as the treatment of choice. Gerwin et al.⁹¹ reviewed the records of twelve patients who had had full-thickness skin necrosis and an exposed prosthesis, six of whom had had a positive culture of deep tissue. All twelve patients were managed with extensive débridement and closure with a medial gastrocnemius myocutaneous flap. Eleven patients had an excellent result, and ten of them retained the prosthetic components or had a successful reimplantation.

The medial gastrocnemius muscle flap is often the preferred type of flap. It is larger and two to three centimeters longer than the lateral gastrocnemius flap. Furthermore, it does not have to traverse the fibula and, therefore, it has a larger arc of rotation. It provides excellent soft-tissue coverage in the region of the patella and the tibial tubercle, where skin necrosis occurs most commonly. A free myocutaneous flap also may be used^99,161, but it should be reserved for patients who have full-thickness necrosis that cannot be covered with a local flap.

Parenterally administered antibiotics often are necessary for patients who have persistent drainage and wound necrosis, but they should not be used indiscriminately. Unnecessary use of antibiotics increases the risk of altering the bacterial flora of a deep infection¹⁶¹. Aspiration of the joint should be done before antibiotic therapy is initiated in order to maximize the results of the culture. Cultures of superficial drainage often are spurious, with little relationship between the organisms grown and those causing deep infection^139,161,271.

In summary, wound problems are a dreaded complication of total knee arthroplasty and ideally are avoided. Preventive measures include the proper choice of the skin incision, gentle handling of the soft tissues, meticulous hemostasis, and wound closure without excessive tension. Should persistent wound drainage or soft-tissue necrosis occur, early intervention is imperative as delay increases the risk of deep infection and failure of the arthroplasty. Full-thickness soft-tissue necrosis often necessitates the transfer of well vascularized tissue such as a medial gastrocnemius myocutaneous flap.

	Neurovascular Complications

Top Introduction Wound Complications Neurovascular Complications Infection Thromboembolic Disease Problems Related to the... Stiffness Supracondylar Fracture of the... References

 
Total knee replacement generally is considered to be a safe and effective procedure. Although neurovascular complications are rare, they are serious, particularly for patients who have complex deformities or who have multiple scars around the knee from previous operative procedures. An awareness of the risk of various neurovascular injuries facilitates the development of preventive strategies and also allows the physician to provide the patient with valuable information regarding this elective procedure before it is performed.

Peroneal Nerve Palsy
Mont et al.¹⁹⁸ found that the cumulative prevalence of peroneal nerve palsy after total knee arthroplasty was 0.58 per cent (seventy-four of 12,784 procedures) as reported in the literature. Variations in prevalence probably are related to the case mix for a given surgeon or institution^132,164,248. Possible mechanisms of nerve injury include traction during correction of a deformity, ischemia when stretching of the surrounding soft tissue causes occlusion of small vessels, and compression by a tight dressing or splint²⁴⁸.

Conditions that have been associated with an increased prevalence of peroneal nerve injury have included a valgus deformity or flexion contracture of more than 20 degrees and a complex biplanar (flexion and valgus) deformity^164,248. Factors that have been found not to be associated with peroneal nerve palsy have included age, type of arthritis, gender, and duration that a tourniquet was used²⁴⁸.

Peroneal nerve palsy most commonly is diagnosed within two days after the total knee replacement. In a study of twenty-two patients (twenty-three knees) who had a peroneal nerve palsy, all were found to have a motor deficit in both the extensor hallucis longus and the tibialis anterior; nine knees (39 per cent) were in patients who had weakness of the peroneus longus and twenty (87 per cent), in patients who had a sensory deficit in the first web space between the great and second toes²⁴⁸. While the prognostic effectiveness of electromyograms and nerve-conduction studies remains unclear¹⁶⁴, confirmatory electrophysiological tests should be done at least three weeks after the operation. The primary purpose of these tests is to document the extent and location of the nerve lesion.

Early treatment of peroneal nerve injury is directed primarily at preventing additional injury. As soon as the injury is diagnosed, all dressings should be loosened and the knee should be allowed to flex to 20 to 30 degrees²⁴⁸. In the study by Rose et al.²⁴⁸, these measures resulted in partial recovery of sensory and motor function in two of eight patients in whom the injury had been recognized early. The role of early open exploration and decompression of the peroneal nerve has not been established; therefore, patients should be managed only with observation unless there is clear evidence of a compressive hematoma, which should be drained operatively.

The chronic treatment of peroneal nerve palsy consists of the use of a dropfoot brace and passive stretching exercises to prevent an equinus deformity. Complete recovery from this injury is rare^164,248. If a dense neurological deficit persists for three months postoperatively, operative decompression of the peroneal nerve may be of some benefit. Krackow et al.¹⁶⁴ reported complete or nearly complete resolution of neurological deficits in five patients who had been managed with decompression five to forty-five months after total knee replacement. In a later study, after twelve to seventy-two months of additional follow-up, thirty of thirty-one patients who had been managed with operative decompression of the peroneal nerve had some degree of functional and neurological recovery, compared with only three of nine patients who had been managed non-operatively¹⁹⁸. The latter study underscores the need for close postoperative follow-up of patients who have peroneal nerve palsy and strongly suggests that operative intervention should be considered if no improvement is noted after three months of non-operative treatment.

A number of strategies can be used in an attempt to prevent peroneal nerve injury in patients who are at high risk. Specifically, an adequate amount of bone should be resected, especially when flexion or valgus deformities are treated, to prevent excessive bow-stringing of the peroneal nerve; tight dressings and plaster splints should be avoided; and flexion of the knee should be allowed in the recovery room. There has been no demonstrated advantage to exploring and prophylactically releasing the peroneal nerve at the time of the total knee arthroplasty in high-risk patients²⁴⁸.

Direct Injury of Vascular Structures about the Knee
Direct injury of vascular structures about the knee can be prevented when a thorough knowledge of the anatomy of the knee is combined with careful operative technique²⁵¹. The locations of the critical vascular structures can be likened to the points on the face of a clock. In the left knee, at the level of the joint line, the popliteal vein is directly posterior (twelve o'clock), with the tibial nerve lying medial to the vein (eleven o'clock) and the popliteal artery lying lateral to the vein (one o'clock). All three of these structures are vulnerable to penetrating injury through the posterior portion of the capsule during meniscal resection, removal of the posterior cruciate ligament, or capsular release. Distal to the joint line, the popliteal artery bifurcates to form the posterior and anterior tibial arteries at the two o'clock position. The common peroneal nerve lies against the fibula, distal to the joint line, at the three o'clock position. Damage of any of these structures between the eleven o'clock and three o'clock positions may occur when excessively long screws are used in this zone for fixation of tibial components inserted without cement²⁵¹.

Any suspicion of intraoperative vascular injury should be evaluated after deflation of the tourniquet and before implantation of the components. The joint and the popliteal region should be inspected carefully, and the return of distal arterial pulses should be confirmed. An expanding popliteal mass, copious posterior bleeding into the joint, and the loss of distal pulses are indications for intraoperative arteriography and an immediate vascular surgery consultation. A small vascular perforation may be treated with simple sutures. Transection of a vessel may be repaired directly if there is no tension on the anastomosis with the knee in full extension¹⁹⁰. Vascular grafting may be necessary when there is tension at the site of the direct repair or extensive vessel damage.

During the resection of the medial and lateral menisci, there is a risk of penetrating injury of the popliteal vessels. Therefore, it is helpful to perform as much of the resection as possible with the scalpel blade parallel to the posterior part of the tibia, pulling the meniscus anteriorly during this procedure. Laterally, the popliteal artery is protected by the belly of the popliteus muscle. The lateral meniscus is more mobile and usually is easily retracted anteriorly.

When the notch for a cruciate-substituting prosthesis is cut, extensive resection of the posterior cruciate ligament may result in entry into the popliteal fossa, where the popliteal vein lies directly behind the capsule in the midline. Leaving a stump of posterior cruciate ligament behind reduces the risk of vascular injury in this situation.

The division of the posterior portion of the capsule at the joint line during the correction of a flexion contracture requires special care to avoid injury of the popliteal vessels and the tibial nerve. A safer approach is to elevate the capsule from the posterior aspect of the tibia and the distal part of the femur while making sure that the scalpel or the elevator stays on the bone.

As pointed out earlier, wound-healing can be affected by the blood supply to the area. The preoperative vascular evaluation should include a thorough inspection of the skin of the lower extremity. The location of operative or traumatic scars, skin color, temperature variations, capillary refill, and the presence of ulcerations should be noted. The strength of the dorsalis pedis and posterior tibial pulses should be documented by palpation or, if necessary, with use of Doppler ultrasound. The ankle-brachial pressure index has been a valuable indicator of the extent of peripheral vascular disease²⁹¹. The measurement of transcutaneous oxygen tension has been reported to be an objective indicator of skin viability and has been used clinically to select the level of amputation for patients who have ischemic disease⁵⁹. Normal volunteers were found to have oxygen pressures of between forty-five and ninety-three millimeters of mercury (6.00 and 12.40 kilopascals) while patients who had peripheral vascular disease were found to have decreasing levels, depending on the severity of the disease⁵⁹.

Preoperative arteriography should be reserved for patients who may be candidates for vascular bypass before total knee replacement or who are having the reconstruction because of a severe post-traumatic condition or a tumor.

Absolute vascular contraindications to total knee replacement include verified vascular claudication with slight or no activity, active skin ulcerations secondary to arterial insufficiency or venous stasis, and ischemia or frank necrosis of the toes¹⁸⁷. If the peripheral pulses are not palpable and there is no potential for vascular bypass, the total knee arthroplasty should be done without use of a tourniquet as a tourniquet may cause thrombosis of the atherosclerotic femoral artery²⁵².

	Infection

Top Introduction Wound Complications Neurovascular Complications Infection Thromboembolic Disease Problems Related to the... Stiffness Supracondylar Fracture of the... References

 
While successful total joint replacement offers dramatic and lasting improvement in the quality of life, deep infection is the most feared complication of this procedure as it threatens the function of the joint, the preservation of the limb, and occasionally even the life of the patient. Since the inception of prosthetic joint replacement, total knee arthroplasty has been associated with a greater rate of infection than total hip replacement. The reason for this difference may be related to the fact that the knee lies superficially beneath the skin and the fascial envelope and is covered by only a limited amount of well vascularized muscle as well as by a watershed area of vascular supply to the skin, which lies directly anteriorly in the position of the typical skin incision. While many advances (such as the routine use of antibiotics perioperatively) have led to a decrease in the rate of infection, anatomical risk factors inherent to the knee contribute to a rate of infection that probably always will be higher than the rate associated with total hip arthroplasty.

Prevalence
The reported rate of deep infection after contemporary total knee replacement has been about 2 per cent (sixty-seven infections were noted after 4171 procedures in one study³⁰⁶ ), with a greater risk of infection associated with implants that have more mechanical constraint between the components^214,304,306. In contrast, no meaningful difference in the rate of infection has been noted between implants inserted with cement and those inserted without it³⁰⁶. The most prevalent organisms, as reported in two series of sixty-seven and twenty-seven knees, were gram-positive: Staphylococcus aureus accounted for 50 to 65 per cent of the infections; Staphylococcus epidermidis, for 25 to 30 per cent; and other bacteria, fungi, and mycobacteria, for 10 to 15 per cent^261,306. Other authors have observed a trend toward an increasing prevalence of Staphylococcus epidermidis as the pathogenic organism for infections about prosthetic joints^14,230.

Several steps can be taken to minimize the risk of infection. Chief among these is the prophylactic use of antibiotics. The most important dose appears to be that administered immediately preoperatively so that adequate levels of antibiotics are present in the hematoma that accumulates after the operation. There are good data only to support the use of prophylactic antibiotics for twenty-four hours after the operation, beginning with an immediate preoperative dose of a first-generation cephalosporin that provides excellent coverage against staphylococcal organisms^89,117,193. There is some additional evidence that the use of adjunctive measures, such as ultraviolet light^18,19 and closed-air exhaust suits^36,174, may substantially reduce the rate of infection even more. The use of clean-air systems remains controversial. There is increasing evidence that horizontal laminar airflow systems actually increase the rate of infection in patients managed with total knee replacement because of the frequent interposition of operating-room personnel between the source of air and the open operative wound^80,254; therefore, vertical laminar airflow systems are preferable.

Various factors increase the risk of infection after total knee replacement; some are inherent to the host and cannot be altered while others may be reduced or eliminated by meticulous preoperative screening of the patient. Rheumatoid disease (independent of the associated use of steroids) (p <0.001), open skin lesions on the affected extremity (p = 0.002), a previous operation about the knee (p < 0.007), and a history of infection (p < 0.01) all have been associated with a significant increase in the rate of deep infection^228,306,307. While three of these factors cannot be altered by the surgeon, open skin lesions should be noted and treated before the elective operation is performed. We prefer a three-month interval of intact dermis over a previous ulceration, such as a venous stasis ulcer, before an elective total knee replacement is performed. The greatest risk of infection is associated with a previous infection of the knee. Wilson et al.³⁰⁶ reported a rate of infection of 3.1 per cent in a study of 1857 osteoarthrotic knees that had had a revision total knee arthroplasty because of an infection around the previous implant. Wilson et al.³⁰⁶ also reported that recurrent urinary-tract infection, diabetes mellitus, systemic use of steroids, and obesity appeared to be associated with an increased rate of infection after total knee replacement but noted that the relationships were not significant. A recurrent urinary-tract infection certainly can be identified and treated preoperatively. When a structural cause of recurrent urinary-tract infection is identified, it should be corrected before a total knee replacement is performed; patients who have chronic, uncorrectable urinary-tract infection should be managed with lifelong antibiotic suppression to minimize the risk of immediate postoperative infection as well as late hematogenous seeding of the site of the prosthesis. Rheumatoid disease, in addition to being associated with the risk of acute infection, also is associated with a risk of late infection secondary to hematogenous bacterial seeding of the site of the prosthesis. The risk of late infection is high; late infections accounted for forty-five (67 per cent) of the sixty-seven infections in the series of 4171 total knee arthroplasties reported by Wilson et al.³⁰⁶.

Routine dental cleaning and extraction produces bacteremia in nearly all patients. Conventional wisdom suggests that antibiotic prophylaxis is appropriate at the time of dental manipulation, but the topic remains controversial³⁴. We believe that the guidelines developed by the American Heart Association¹³³ for prophylaxis against infection around prosthetic heart valves are both sound and sensible and that they may reasonably be extended to prophylaxis against infection in patients who have a prosthetic joint replacement.

Diagnosis
A patient who has an infection at the site of a prosthetic device in the knee usually has a painful, warm, stiff, swollen, and tender joint. The differential diagnosis of pain at the site of a knee replacement in the absence of mechanical loosening includes reflex sympathetic dystrophy, heterotopic ossification, and arthrofibrosis. A patient in whom such an infection is suspected should be evaluated with a physical examination as well as plain radiographs; the latter often demonstrate no abnormal findings initially but later reveal evidence of marginal osseous resorption, erosion, and loosening of the prosthetic components. The keystone of diagnosis, however, is aspiration of the joint and analysis of the fluid with gram-staining as well as complete and differential cell counts. The joint should be aspirated under meticulously sterile conditions with operative preparation of the skin to minimize the risk of contamination of the specimen with skin flora. An erythrocyte sedimentation rate provides a baseline for serial follow-up analysis of the response to treatment. Various nuclear-medicine techniques, ranging from the traditional technetium bone scan to the indium-labeled white-blood-cell scan, have received a great deal of attention. Sequential and differential application of these two techniques reportedly yielded an 84 per cent rate of accuracy in a series of thirty-eight patients²²⁹, but accuracy remains highly dependent on both the technique and the institution in which it is used. Occasionally, all efforts at definitive identification of an infecting organism are fruitless despite a very suspicious and often convincing clinical course characterized by pain as well as loosening of the components. In this situation, staged reconstruction commonly is performed, and it is only with direct culture of the tissue membrane beneath the implant, material obtained by swabbing of the device, or cement fragments that an organism is identified.

Management
Once the presence of a deep-seated infection has been established, the greatest challenge to the physician is related to the conflict between management of the patient and treatment of the infection at the site of the prosthesis. It is important to manage the patient rather than an isolated knee joint, and the physician must balance the anticipated quality and longevity of life and function against the desire to eradicate the infection. Important factors to consider include the chronological and physiological ages of the patient, the concurrent medical illnesses (particularly insulin-dependent diabetes mellitus and rheumatoid arthritis), and the functional demands of the patient. Local conditions that influence the decision are the nature of the infecting organism and its sensitivity to available antibiotics, the integrity of the extensor mechanism, the adequacy and integrity of the skin and the soft-tissue envelope, and the adequacy of adjacent bone stock. It is clear that if eradication of the infection is the primary goal of treatment the entire prosthetic joint should be removed to optimize the chance of the infection resolving^230,310. In an elderly and infirm patient who has a mechanically secure knee replacement, however, the morbidity associated with removal of the prosthesis is often considerably greater than that associated with chronic antibiotic suppression with preservation of the knee joint. Therefore, in placing the priority of management of the patient above that of intensive treatment of the knee infection, retention of a secure prosthesis in conjunction with chronic antibiotic suppression often offers greater function to the elderly patient. When an infection contributes to mechanical loosening and symptoms in the knee joint, operative removal is a more practical and functional, and a less destructive, treatment course.

Retention of the Prosthesis
In the setting of acute infection (onset, within ten to twenty-one days after the operation) with susceptible gram-positive bacteria and no evidence of mechanical loosening of the components, antibiotic therapy instituted within forty-eight hours of onset has been associated with a success rate of 6 to 10 per cent in several large studies^{14,148,228,261,307}. The likelihood of successful retention of the prosthesis in a patient who has an acute infection may be increased by open débridement and radical synovectomy. Success rates of 18 per cent (seven of thirty-nine knees³² ) to 23 per cent (seven of thirty-one knees²⁶¹ ) have been reported with this approach, which necessitates lifelong antibiotic suppression in an effort to contain the infection indefinitely. In the setting of late infection (onset, more than twenty-one days after the initial implantation), this approach has been associated with a lower rate of success^32,228,261. Operative débridement followed by short-term parenteral administration of antibiotics and then indefinite oral antibiotic suppression led to successful retention of the implant at five years in thirty (26 per cent) of 114 patients in three studies^32,261,306. Recent reports concerning the use of rifampin in combination with a fluorquinone antibiotic for suppression of infection around a prosthetic joint have been encouraging⁶⁰, and this technique may be useful when removal of the prosthesis is not thought to be in the over-all best interest of the patient.

Removal of the Prosthesis
It is widely accepted that removal of the prosthesis is a mandatory part of the over-all treatment plan when eradication of the infection is the primary goal. Although resection arthroplasty infrequently is selected as the definitive treatment, it remains a viable option for patients who have involvement of multiple joints (such as those who have rheumatoid disease), limited functional goals and a prospect for walking only with assistance of a walker, or local risk factors precluding a reoperation about the knee⁷³. In such patients, modest motion, often in the range of 45 degrees, is preserved for activities of daily living. Usually, a brace is needed for walking. In the study by Falahee et al.⁷³, over-all patient satisfaction approached 80 per cent and most patients had good or excellent relief of pain despite the persistence of a draining sinus in three (11 per cent) of twenty-eight knees.

Alternatively, arthrodesis of the knee provides a more durable lower extremity. After an arthrodesis, the ability to walk independently depends on good function of the neighboring joints of the lower extremity. This procedure, however, has been complicated by a rate of non-union of as low as two of eighteen knees⁶⁷ and as high as 30 per cent^228,307. Intramedullary nailing has become the preferred method of knee arthrodesis; when this procedure was performed in a staged fashion, with removal of the prosthesis and débridement of the infected area followed at a later date by placement of an intramedullary nail, solid fusion was achieved in seventy-four (89 per cent) of eighty-three patients^{55,67,218,304}. Staging of the débridement and reconstruction portions of the procedure reduces but does not eliminate the risk of spreading the infection into the medullary canals. The mean time to osseous union is six months, but the rate of complications associated with this technique has been as high as ten complications in eighteen patients⁶⁷. Alternatively, Rand et al.²³² reported that arthrodesis with use of an external fixation technique led to a successful fusion in nineteen (68 per cent) of twenty-eight patients. This method is indicated in the setting of a particularly virulent organism, in which the risk of intramedullary metastasis of the infection is considerable, or when there is an osteoarthrotic hip or an ipsilateral total hip replacement proximal to the infected knee that precludes the use of the intramedullary device. Arthrodesis with the external fixator can be accomplished in a single operative setting and permits delayed skin coverage for the treatment of a deficient soft-tissue envelope. Rand et al.²³² reported that ten (36 per cent) of twenty-eight patients who were managed with this technique had a total of seventeen different complications, largely consisting of pin-track infections that resolved with removal and replacement of the offending pin.

In the setting of a particularly virulent or resistant organism, amputation may be considered. While fortunately it is only infrequently required to treat a life-threatening infection that is refractory to antibiotic therapy, gross bone deficiency, or an irretrievably incompetent soft-tissue envelope, amputation may provide the most expeditious resolution of a very difficult problem. Unfortunately, a poor functional result is the rule, with only one-third of patients retaining the ability to walk (even with assistive devices) and the other two-thirds remaining confined to a wheelchair²¹⁷.

Exchange of the Prosthesis
Single-stage exchange currently is done only rarely. Historically, the success rate of this procedure has ranged from 50 to 75 per cent^{228,230,307,310}, with a good or excellent result noted in twenty-four of thirty-eight knees in one series³¹⁰ and successful reimplantation with clearing of infection observed in eight of fourteen patients in another series²³⁰. It is now commonly accepted that if the treatment goal is a durable and functional prosthetic knee joint that is free of infection, débridement followed at a later date by reimplantation is the preferred treatment plan^230,307,310. Several conditions must be met in order for such a staged reimplantation to be successful. Skin coverage must be adequate as the presence of multiple old incisions or myofascial flaps increases the risk of subsequent failure of the soft-tissue envelope. An intact extensor mechanism-patellar ligament complex is essential for independent function of the knee. Adequate bone stock to support the revision implant also is required, and the use of allografts to reconstruct osseous defects is associated with an increased risk of infection and failure. The antibiotic sensitivity of the infecting organism must be such that several antibiotics are therapeutic options. Finally, the patient must have a competent immune system that is not compromised by the presence of diabetes mellitus, rheumatoid disease, or any other such disorder. We have found that problems in any two of these five critical areas considerably increase the likelihood of failure of reimplantation of a prosthetic knee joint, and we do not perform prosthetic reimplantation in patients who have deficiencies in three of these critical areas.

All foreign material, including the implant and all methylmethacrylate, must be removed at the time of the initial débridement. The bone is cleaned meticulously, and an antibiotic-impregnated methylmethacrylate spacer-block is interposed between the femur and the tibia, both to preserve the joint space for later reimplantation and to permit stability with weight-bearing across the resected knee joint. Vancomycin (500 milligrams) and tobramycin powder (1.2 grams) usually are added to each forty-gram bag of methylmethacrylate. Often, two to three packs of cement are necessary to create a block of sufficient size to fill a large defect. Parenteral administration of appropriate antibiotics is continued for six weeks, and then we prefer to continue oral administration of antibiotics for an additional six weeks, for a total of three months of systemic antimicrobial therapy. The administration of antibiotics is discontinued at least six weeks before the pseudarthrosis is reaspirated. Reimplantation can be considered if the culture of aspirate is negative. It is critically important to assess the readiness of the soft-tissue envelope to undergo an additional operative procedure; continued induration and dermal edema are relative contraindications to the reimplantation of a knee prosthesis. It is best to perform the delayed reimplantation when the wound is soft, supple, and free of edema and induration. Reimplantation is therefore carried out between twelve weeks and one year after the initial débridement. While a negative culture of fluid aspirated from the pseudarthrosis does not guarantee that the infection will not recur after reimplantation, a confirmed positive culture is a contraindication to reimplantation of a prosthetic device. A posterior-cruciate-replacing implant always is used in this setting, and patellectomy occasionally is helpful to obtain skin closure in difficult situations in which the soft-tissue envelope is marginal. Antibiotic-impregnated methylmethacrylate (prepared as described) is routinely used for prosthetic fixation, with the antibiotic agents selected according to the sensitivity profile of the organism or organisms previously grown on culture. Antibiotics generally are not used chronically but rather such treatment is discontinued after all cultures are negative. While staged reimplantation is fraught with numerous potential problems and is dependent on meticulous management of the patient and operative technique, the reported rate of success (defined as freedom from the original infection and a functioning prosthetic knee joint) has been as high as 97 per cent (sixty-one of sixty-three knees)^26,310.

	Thromboembolic Disease

Top Introduction Wound Complications Neurovascular Complications Infection Thromboembolic Disease Problems Related to the... Stiffness Supracondylar Fracture of the... References

 
Historical data from large series of patients managed with a total of 638 total knee replacements have demonstrated a prevalence of deep-vein thrombosis of 70 to 80 per cent in the absence of prophylaxis²⁸². Additionally, while the prevalence of subsequent pulmonary embolism following total knee replacement is considerably less than that following total hip replacement, the risk is real; moreover, this complication often escapes the attention of the surgeon as it most frequently occurs weeks after discharge^{178,209,211,273,282}. Thromboembolic disease following total knee arthroplasty has been studied less systematically than that following total hip arthroplasty and remains an important area for organized prospective clinical investigation.

Thromboembolic disease following total knee replacement has a considerably different profile than that following total hip arthroplasty. There is a strong propensity for deep-vein thrombosis in the vessels of the calf, with 85 to 90 per cent of thrombi after total knee replacement occurring distal to the trifurcation of the popliteal vein^84,178,282. In contrast to the situation after total hip replacement, only 10 to 15 per cent of patients have thrombosis of the femoral or popliteal vein after knee arthroplasty, and when proximal thrombosis is present it is most frequently a continuous extension of concurrent thrombosis in the calf^{84,101,178,209}. Segmental, discontinuous femoral thrombosis rarely is noted after total knee replacement, which again is quite distinct from the situation after total hip arthroplasty. Bilateral deep-vein thrombosis is noted in 10 to 15 per cent of patients who have had a total knee replacement; more specifically, deep-vein thrombosis has been identified in the normal, contralateral lower extremity of 10 to 15 per cent of patients who have had unilateral total knee arthroplasty^84,282.

The effect of the use of a pneumatic tourniquet on the development of deep-vein thrombosis has been difficult to characterize definitively. Previous authors have identified both beneficial and detrimental effects of this device^72,165,167. Beyond the obvious detrimental effect of the promotion of venous stasis distal to the tourniquet, stimulation of the fibrinolytic system by the vascular endothelium has been observed following release of the tourniquet^72,167. This latter effect may contribute to a reduction in the risk of venous thrombosis, but it clearly is not the predominant effect in view of the high prevalence of thrombi in patients managed without prophylaxis.

The benefit of adjunctive non-pharmacological measures is supported by circumstantial evidence. Perhaps most interesting among these measures is the use of regional anesthesia, specifically continuous epidural anesthesia, which has been associated with a decreased frequency of deep-vein thrombosis⁴⁷. The effects of regional anesthesia on the hemodynamics of the lower extremity are better understood than is the direct impact of such anesthesia on thromboembolic disease. Most evident is an increase in venous flow and blood return to the central circulation secondary to a sympathectomy effect and decreased resistance in the capacitance vessels of the lower extremity following the epidural administration of an anesthetic. Additionally, there is evidence of increased fibrinolysis secondary to activity of the vascular endothelium as well as of decreased platelet adhesiveness as a possible direct effect of the local anesthetic agent. The net clinical effect of a regional anesthetic has been reported to be a decrease in the frequency of deep-vein thrombosis^{47,152,208,286}. Additional analysis has suggested that regional anesthesia has a selective effect in that it reduces thrombosis in the veins of the calf but has relatively little impact on thrombosis in the larger, more proximal (femoral and popliteal) vessels⁴⁷. Unfortunately, the true effect of regional anesthesia on deep-vein thrombosis is not entirely clear because of differences in the literature with regard to the exact type of anesthetic used (spinal or epidural), whether the anesthetic was used for the operation only or whether epidural analgesia was maintained postoperatively for pain control, the patient population, the presence or absence of hip fracture, the type of operation (hip or knee replacement), and whether the local anesthetic was used alone or in combination with narcotics or even general anesthesia. Therefore, the true beneficial effect of regional anesthesia with regard to reducing the frequency of deep-vein thrombosis remains to be identified.

Continuous-passive-motion machines offer the theoretical advantage of reducing stasis in the veins of the calf^108,179. However, we are not aware of any documented evidence that the use of such a device reduces the prevalence of deep-vein thrombosis following total knee arthroplasty.

In general, the effect of anticoagulant prophylaxis on the prevalence of deep-vein thrombosis after total knee replacement has been considerably less profound than that after total hip replacement. The reasons for this difference remain to be elucidated. Warfarin is currently the most commonly used agent for prophylaxis against deep-vein thrombosis among orthopaedic surgeons who routinely use prophylaxis. It has, however, lacked popularity in the past because of the historical recommendation to maintain the prothrombin time at two times the control value (international normalized ratio, 3.0 to 4.0), which has resulted in prothrombin times in excess of twenty seconds and rates of bleeding complications of 8 to 10 per cent after joint replacement^119-121 and as high as 22 per cent (eleven of forty-nine patients) after treatment of proximal deep-vein thrombosis¹²⁹. More recently, authors have recognized that anticoagulation with warfarin, either as prophylaxis or as specific treatment for identifiable venous thrombosis, is quite effective when the prothrombin time is maintained between 1.3 and 1.5 times the control value (international normalized ratio, 2.0 to 2.5), resulting in prothrombin times of fifteen to eighteen seconds and considerably lower rates of bleeding complications (in the range of less than 2 per cent)^{82,84,119-121}. Routine use of warfarin for prophylaxis after total knee replacement has decreased the over-all prevalence of deep-vein thrombosis to 30 to 40 per cent but has not changed the distribution of thrombi from proximal to distal^84,178,282. Although the prevalence of deep-vein thrombosis has been reduced considerably, these rates still are unacceptably high and the search for better methods of prevention continues.

Low-molecular-weight dextran was popular for a period of time but, more recently, it was shown to be no more effective than a placebo^83,86. Moreover, dextran is associated with a considerable risk of volume overload and congestive heart failure in elderly patients and occasionally leads to an allergic reaction. Aspirin, in contrast, has relatively few adverse effects and decreases platelet adhesiveness. Numerous studies have compared aspirin with other agents and placebos, but none has definitively demonstrated that aspirin is more effective than a placebo for prophylaxis against deep-vein thrombosis after total knee replacement^108,181,282. Meta-analyses have suggested a possible beneficial effect, but the National Institutes of Health Consensus Conference on thromboembolic disease in 1986 considered aspirin to be ineffective for this purpose²⁰⁵. Even so, aspirin continues to be used frequently after total knee arthroplasty, largely because it is associated with few complications^108,178,282.

Pneumatic compression devices have become popular recently and indeed are intuitively attractive for use with total knee replacement as the calf is the prevalent location for thrombi, which are likely to form secondary to stasis^85,108,128. Thigh-high sleeves are awkward to use after knee arthroplasty as they cover the operative incision. Calf-high sleeves are more practical and have been shown to reduce the prevalence of thrombosis in the veins of the calf after knee arthroplasty¹⁰⁸. More recently, plantar impulse pads have become popular. These devices are more convenient to use, and they work by means of a slightly different mechanism; specifically, they deliver high-impact compression to the sole of the foot, resulting in a high-velocity pulsatile flow in the femoral vein. Early results from a single study suggested that plantar impulse pads were more effective than aspirin for prophylaxis against deep-vein thrombosis after total knee replacement³⁰². Because these devices do not increase the risk of bleeding complications, it is hoped that they will be definitively proved to be effective for the prevention of deep-vein thrombosis.

Fractionated heparin also has been popular recently. This smaller, more homogeneous heparin molecule is characterized by a more favorable binding affinity profile to activated factors X and II, resulting in an antithrombotic effect that is exerted earlier in the clotting cascade and theoretically decreasing the risk of concurrent bleeding complications as compared with the risk with unfractionated heparin. Coagulation times do not need to be monitored, but parenteral subcutaneous administration is required. Fractionated heparin has been shown to be extremely effective for reducing the over-all prevalence of deep-vein thrombosis following total hip replacement^39,290; in the study by Colwell et al.³⁹, for example, deep-vein thrombosis was noted in only eight (6 per cent) of 136 patients who had received fractionated heparin. Like warfarin, however, fractionated heparin has been considerably less effective for prophylaxis against deep-vein thrombosis following total knee arthroplasty^170,235. The over-all rate of deep-vein thrombosis following total knee replacement among patients managed with fractionated heparin reportedly has ranged from 20 to 30 per cent, but the over-all rate of bleeding complications has ranged from 8 to 10 per cent, which is significantly greater than that associated with low-dose warfarin as reported in a number of prospective, controlled studies^{39,170,235,290}. Bleeding complications are more common with use of fractionated heparin, both at the operative wound and at the injection site, but bleeding from the wound may be reduced by beginning the medication no sooner than twelve hours postoperatively.

In summary, the best approach to the prevention of deep-vein thrombosis and fatal pulmonary embolism following total knee arthroplasty has yet to be defined. Augmentation of blood flow by any one of a number of means is an intuitively appealing method for the reduction of stasis. Compression devices, such as calf-high sleeves and plantar impulse pads, are promising but remain to be proved effective. Regional anesthesia also is associated with a decrease in the prevalence of thrombosis in the veins of the calf, but the specifics regarding the type and duration of such anesthesia have yet to be delineated. Finally, a plan of early mobilization, frequently the byproduct of a shorter length of stay in the hospital, probably also contributes to a reduction in the prevalence of thrombosis in the veins of the calf in a way that is difficult to define and quantitate precisely.

The ideal pharmacological agent has not been identified. Clearly, this agent should be associated with a low frequency of bleeding complications, particularly after knee replacement, because the wound tolerates a hematoma quite poorly. Warfarin, aspirin, and fractionated heparin all are somewhat popular at the present time, and each has advantages and disadvantages. While the use of fractionated heparin must be investigated further, warfarin has been shown to be reasonably effective and to be associated with a very low risk of concomitant bleeding complications.

Perhaps the most provocative question concerns the duration of chemoprophylaxis in the setting of a mean hospital stay of four or five days after knee replacement. Two strategies have been proposed. The first, treatment of all patients with extended prophylaxis consisting of administration of warfarin or fractionated heparin for six to twelve weeks after the operation, has the advantage of not requiring routine surveillance for identification of deep-vein thrombosis. Unfortunately, given the 30 to 40 per cent prevalence of deep-vein thrombosis after knee replacement, such extended exposure to anticoagulants is unnecessary for 60 to 70 per cent of patients. Furthermore, exposure of the entire postoperative population to outpatient use of anticoagulants increases the likelihood of bleeding complications. The second strategy involves routine surveillance for deep-vein thrombosis followed by treatment of identified venous disease. Unfortunately, non-invasive screening, such as color flow Doppler and duplex ultrasound, are relatively ineffective for identifying disease in the calf, which is the most common location for deep-vein thrombosis after total knee arthroplasty^101,300. Contrast venography remains quite sensitive for the identification of thrombi in the calf^84,219,300, but it is invasive and is accompanied by some morbidity. Although these screening studies add to hospital costs, the reduced outpatient exposure to anticoagulant agents considerably decreases the risk of bleeding and associated rehospitalization and suggests that routine surveillance may be more cost-effective than extended prophylaxis for all patients^211,212. We believe that, with the advent of better non-invasive studies for identification of deep-vein thrombosis, the most promising of which is magnetic resonance venography¹⁶⁶, the strategy of routine surveillance and selective treatment will be the favored approach in the future.

	Problems Related to the Extensor Mechanism

Top Introduction Wound Complications Neurovascular Complications Infection Thromboembolic Disease Problems Related to the... Stiffness Supracondylar Fracture of the... References

 
Long-term evaluations have demonstrated that total knee arthroplasty provides excellent relief of pain, improved function, and superior durability^{52,92,142,247}. Improvements in prosthetic design have resulted in increased function and a better range of motion, but there have been persistent problems involving the patellofemoral joint^{8,30,41,49,52,56,75,87,105-107,109,123,141,143,162,200,263,265,277,287}. Many early total knee prostheses failed to provide for resurfacing of the patellofemoral joint. Anterior knee pain has been reported in as many as one-half of patients for whom a patellar resurfacing procedure was not done^{37,66,69-71,88,138,139,156,169,192,197,200,204,215,221,222,264,277,278,292}. Design modifications that allow for resurfacing of the patella have produced superior functional results as well as a reduction in patellofemoral pain^{88,138-140,169,171,221,222,224,225,268,276}, but an additional set of complications has emerged: patellofemoral instability, patellar fracture, loosening or failure of the patellar component, patellar clunk syndrome, and tendon rupture^{37,56,88,125,131,141,194,196,234,274,293,297}. The rate of complications resulting from patellofemoral resurfacing has ranged from seventeen (5 per cent) of 350 knees⁵⁶ to seven of fourteen knees^{33,37,88,109,112,131,169,196,197,200,222,265,274,277,285}, and such complications have accounted for as many as one-half of the total knee revisions performed^10,28,285. Patellofemoral complications have been attributed to errors in operative technique, inferior prosthetic design, and excessive patellofemoral loads. Numerous studies of patellofemoral joint-reaction forces have demonstrated compressive loads of one-half to one times body weight during walking on a level surface, increasing to three to four times body weight with stair-climbing and to as much as seven to eight times body weight during squatting^{130,201,237,264}.

Patellofemoral Instability
The prevalence of patellar subluxation following total kne arthroplasty was as high as four of fourteen knees in one series³³. Failure to obtain satisfactory patellofemoral tracking may result in patellofemoral pain and crepitus as well as wear, failure, loosening, or fracture of the component (or a combination of these problems), which may jeopardize an otherwise successful functional result of a total knee-replacement procedure^{28,37,52,56,176,192,196,197,200,222,231,249,264,283}.

Patellofemoral instability most commonly results from imbalance in the extensor mechanism characterized by excessive tightness of the lateral retinaculum and associated weakness of the vastus medialis muscle^56,200,222. Placement of prosthetic components in an excessively valgus position increases the Q angle and results in an increased lateral force-vector on the patella^{59,173,200,238}. Disruption of the capsular repair, by hemarthrosis, overly intensive physiotherapy, or injury, also may result in patellofemoral instability.

Asymmetrical patellar resection can lead to patellofemoral instability as well. The normal patella is asymmetrical in contour as the thickness of the medial facet is greater than that of the lateral facet; therefore, resection of equal amounts of bone from the medial and lateral facets retains the asymmetry of the patella. Asymmetrical patellar resection (typically, resection of too much bone from the lateral facet) can lead to problems with patellar tracking^96,176,231. Minimum resection of the lateral facet, usually to the level of the subchondral bone, is recommended for optimum function (Fig. 1).

View larger version (35K): [in this window] [in a new window]   Fig. 1 The top diagram demonstrates the asymmetrical thickness of the facets of the normal patella. Resection of an equal amount of bone from the medial and lateral facets retains the asymmetry of the patella. The lower diagram demonstrates the recommended level of resection; little bone is removed from the lateral facet.

View larger version (41K): [in this window] [in a new window]   Fig. 2 Diagram demonstrating internal rotation of the femoral component, which moves the trochlear groove medially in relation to the patella.

View larger version (41K): [in this window] [in a new window]   Fig. 3 Diagram demonstrating the correct alignment of the tibia (left) and lateralization of the tibial tubercle due to internal rotation of the tibial component on the proximal part of the tibia (right).

An intraoperative assessment of patellar tracking is critical in order to minimize patellofemoral instability. True patellofemoral alignment can be assessed only after tourniquet release, which eliminates the tourniquet's binding effect on the extensor mechanism⁵². Should the patella subluxate laterally when the knee is flexed (before closure of the capsule) without additional, medially directed stabilization by the surgeon's thumb (the no-thumb technique), a lateral retinacular release should be performed^134,264.

Patellofemoral instability is treated on the basis of its etiology. Non-operative measures include intensive quadriceps rehabilitation; external patellofemoral bracing; and avoidance of activities, such as squatting or stair-climbing, that involve heavy loading of the patellofemoral joint. When an extensor mechanism imbalance does not respond to these non-operative measures, a lateral retinacular release, often combined with advancement of the vastus medialis muscle (proximal realignment), is indicated¹³⁴. Capsular repair is necessary when initial central patellar tracking reverts to immediate lateral subluxation following a traumatic event. In some patients, a capsular defect is palpable and helps to confirm the diagnosis. Medial transfer of the tibial tubercle, in conjunction with osteotomy of the tibial tubercle, should be considered in instances of severe malalignment that cannot be corrected with soft-tissue procedures alone because of the inherent risk of non-union at the osteotomy site with osteotomy alone. Should non-union at the site of a tibial tubercle osteotomy occur with disruption of the extensor mechanism, salvage options often are complex and include repeat attempts at fixation of the osteotomy site with bone-grafting as opposed to extensor-mechanism allografting¹⁶⁰. Prosthetic revision is performed for patients who have substantial malpositioning of the components that is not amenable to simpler realignment procedures.

Patellar Fracture
Although patellar fracture is a rare complication of total knee arthroplasty^93,126,289, a prevalence of as high as three of fourteen knees was reported in one study³³. Various causes of patellar fracture have been proposed, including trauma, patellar subluxation, improper patellar resection, vascular compromise, component design, component malpositioning, increased flexion, thermal necrosis, and revision arthroplasty^{4,33,37,56,61,93,126,169,176,222,227,244,265,285}. Biomechanical studies have demonstrated that contact forces substantially increase with patellofemoral malalignment, which perhaps explains why there is an increased prevalence of patellar fractures in patients who have such malalignment¹⁵⁵. Both the eccentricity and the magnitude of patellofemoral loads increase with patellar subluxation¹²⁷, and this increases the risk of patellar fracture.

Excessive patellar resection predisposes to patellar fracture, especially if subchondral bone is removed¹⁵³. Reuben et al.²³⁹ demonstrated that patellar resection that results in an osseous thickness of less than fifteen millimeters substantially increases anterior patellar strain. Conversely, too little patellar resection creates a thick patella-patellar component composite and increases patellofemoral joint-reaction forces as well as tension within the quadriceps tendon. Use of a femoral component with an excessive anteroposterior diameter or implantation of the femoral component in a flexed position increases patellofemoral joint-reaction forces and the probability of fracture^222,283. Asymmetrical resection also can result in impaired mechanical strength of the patella, particularly if too much bone is resected from the lateral facet. Finally, it has been shown that, when the patella is prepared for component fixation, the creation of a large central peg-hole increases anterior patellar strain more than the creation of smaller peripheral peg-holes; the former technique, therefore, is associated with an increased risk of fracture^94,231.

Operative disruption of the patellar blood supply resulting in avascular necrosis also has been associated with patellar fracture^{28,126,169,231,265}. Analyses of the patellar blood supply have demonstrated both extraosseous and intraosseous vascular systems^{23,158,257,258}. The extraosseous system comprises a peripatellar anastomotic ring that is supplied by six main arteries (Fig. 4-A). The superior portion of the vascular ring passes anterior to the quadriceps tendon, while the inferior portion passes posterior to the patellar ligament through the fat pad. The intraosseous system comprises the mid-patellar, polar, and quadriceps-tendon blood supplies (Fig. 4-B). The mid-patellar vessels penetrate anteriorly through the middle one-third of the patella and branch into both the proximal and the distal pole. The polar vasculature passes through the proximal fat pad, posterior to the patellar ligament, and then enters and supplies the inferior pole of the patella. Scapinelli^257,258 observed minimum vascular penetration into the superior pole and periphery of the patella, while Bjorkstrom and Goldie²³ demonstrated a superior vascular supply through the quadriceps tendon.

View larger version (44K): [in this window] [in a new window]   Figs. 4-A and 4-B: Diagrams demonstrating the peripatellar vascular supply. Fig. 4-A: The extraosseous peripatellar anastomotic ring, which is supplied by six main arteries. LSG = lateral superior genicular, MSG = medial superior genicular, MIG = medial inferior genicular, LIG = lateral inferior genicular, SG = supreme genicular, and ATR = anterior tibial recurrent.

View larger version (36K): [in this window] [in a new window]   Fig. 4-B The intraosseous vascular system. QT = quadriceps tendon, MP = mid-patellar, and P = polar.

Malpositioning of components can affect the prevalence, type, severity, and prognosis of patellar fractures^76,93. Errors in joint-line position, the alignment of the lower extremity, or patellar coverage by the prosthesis may increase the risk of fracture. Severe malalignment has been associated with more complex fracture patterns and a worse prognosis^76,93.

Additional risk factors for patellar fracture include increased flexion following total knee arthroplasty, thermal necrosis, and revision total knee arthroplasty. Windsor et al.³⁰⁹ reported that patients who have knee flexion greater than 95 degrees generate increased patellofemoral compression forces and frequently have higher activity levels. The heat of polymerization of the polymethylmethacrylate (reported to be as high as 80 to 90 degrees Celsius in total hip arthroplasty) may exceed the coagulation temperature of tissue proteins, resulting in thermal necrosis of bone^{20,53,100,124,183,305}. Grace and Sim¹⁰⁰ reported that the prevalence of patellar fracture following primary total knee arthroplasty (0.12 per cent; nine of 7754 procedures) was lower than that following revision total knee arthroplasty (0.61 per cent; three of 495 procedures).

Loosening of the Patellar Component
Loosening of a patellar component that was inserted with cement during a total knee arthroplasty has been uncommon, with a reported prevalence of less than 2 per cent in most studies^{37,56,176,221,222}. Rae et al.²²¹, for example, reported such loosening after only two of 132 procedures. The prevalence of loosening following patellar resurfacing without cement has been higher yet variable^{37,56,79,176,221,222}. Firestone et al.⁷⁹, in a study of several different components that were designed to be inserted without cement, reported loosening rates of 0.6 per cent (one of 165 procedures) to 11.1 per cent (thirty-seven of 334 procedures). Factors associated with loosening of the patellar component include insertion of the prosthesis with cement into worn, sclerotic bone; malpositioning of the patellar component; subluxation, fracture, or avascular necrosis of the patella; osteoporosis; asymmetrical resection; loosening of other prosthetic components; and a lack of osseous growth into the porous coating^28,231. A reduction in the rate of loosening of the patellar component requires improved bone preparation and cementing techniques²²¹, proper patellar resection, avoidance of asymmetrical or excessive bone removal, and central patellar tracking.

Options for the treatment of loosening of the patellar component include revision of the component, removal of the component and patellar arthroplasty (smoothing of the remaining patella without resurfacing) if the remaining bone stock is unsatisfactory, and patellectomy. Some patients are asymptomatic and need no treatment, although Brick and Scott²⁸ noted that twelve of sixteen knees eventually were symptomatic enough to need a revision arthroplasty. It should be noted that total dislodgment of the component, most commonly inferiorly, may lead to erosion of the posterior surface of the overlying patellar ligament and an increased risk of disruption of that ligament.

Failure of the Patellar Component
Although failure of polyethylene patellar components has been reported^40,296, this complication primarily has been associated with metal-backed designs^9,10,249,283. The proposed advantages of metal-backed designs were that they would decrease patellar surface strain⁹⁴, support the overlying polyethylene to decrease deformation, and allow for fixation of the patellar component without cement. These designs have failed because of wear and fracture of the polyethylene, dissociation of the polyethylene from the metal plate, dissociation of the pegs from the metal plate, and fracture of the metal plate^9,10,249.

Wear of the polyethylene of a patellar component is not unexpected. Cepulo et al.³⁵ observed that peak patellofemoral contact pressures far exceed the yield strength of polyethylene. Wright and Bartel³¹² reported increased degradation of the polyethylene of retrieved tibial components that had less polyethylene thickness. The addition of a metal backing to a patellar component reduces the polyethylene thickness, which may predispose to increased wear. Also, with metal-backed designs, less wear is required before catastrophic failure occurs because of wear-through of the polyethylene to the underlying metal plate. In most designs, the metal backing does not extend to the edge of the polyethylene. Therefore, as the peripheral polyethylene is loaded, it deforms over the rim of the metal plate and may be severed by the sharp, non-deforming edge of the plate²⁸³.

Dissociation of the polyethylene from the metal plate may result from excessive polyethylene wear or fracture. In most designs, the polyethylene is attached to the metal backing by means of a mechanical gripping of the periphery of the plate by the polyethylene without a chemical bond between the two materials. With advanced wear of the peripheral polyethylene, the integrity of this polyethylene-plate attachment may be disrupted, allowing the polyethylene to dissociate²⁸³.

The fixation pegs of the patellar component may fracture at the site of attachment to the metal plate because of high shear stresses. Substantial shear stresses can occur at the peg-plate junction because of the eccentric loads normally placed on the patella²⁴⁹. These shear stresses are increased when there is patellofemoral malalignment¹⁹². Retrieval analyses of patellar components that had been inserted without cement have shown that osseous growth into the anchoring pegs does occur⁵¹. If the growth into the fixation pegs occurs without accompanying growth into the metal plate itself, a high shear load occurs at the peg-plate junction and increases the risk of peg fracture (Figs. 5-A and 5-B). Rosenberg et al.²⁴⁹ reviewed the results of 122 total knee arthroplasties that had been performed with metal-backed patellar components inserted without cement and noted twelve fatigue fractures at the peg-plate junction. In all twelve knees, there was good osseous growth into the fixation pegs without growth into the porous plate.

View larger version (120K): [in this window] [in a new window]   Figs. 5-A and 5-B: Lateral radiographs of a knee that was treated with a metal-backed patellar component. Fig. 5-A: Radiograph demonstrating early angulation of the pegs of the patellar component.

View larger version (127K): [in this window] [in a new window]   Fig. 5-B: Subsequent radiograph demonstrating a peg-plate fracture.

Clinical signs of failure of the patellar component include effusion as well as crepitus, which occasionally is audible. Clinical symptoms often appear suddenly following activities associated with increased patellofemoral loading, such as climbing stairs, squatting, or rising from a seated position. Intraoperative findings frequently include black staining of the synovial membrane with metal debris and wear or fragmentation of the polyethylene. The femoral component also may be worn, as it was in eleven of twenty-five patients who had failure of a metal-backed patellar component in the study by Bayley et al.¹⁰. Loose porous-coated beads or titanium-fiber-mesh fragments may be found embedded in the polyethylene of the patellar and tibial components. Therefore, if revision is necessary because of failure of a metal-backed patellar component, the surgeon always must be prepared to revise all three components⁵⁰.

Patellar Clunk Syndrome
Patellar clunk syndrome results from the development of a fibrous nodule at the junction of the posterior aspect of the quadriceps tendon and the proximal pole of the patella. With flexion of the knee, this nodule enters the intercondylar notch of the femoral prosthesis. As the knee is extended, the nodule becomes entrapped within the notch as the quadriceps tendon and the patella migrate proximally. At 30 to 45 degrees from full extension, enough tension is placed on the fibrous nodule to cause it to clunk out of the intercondylar notch (Figs. 6-A, 6-B, and 6-C)^13,125.

View larger version (43K): [in this window] [in a new window]   Figs. 6-A, 6-B, and 6-C: Patellar clunk syndrome. Fig. 6-A: Diagram demonstrating a suprapatellar fibrous nodule entrapped within the intercondylar notch during flexion of the knee.

View larger version (36K): [in this window] [in a new window]   Fig. 6-B Diagram demonstrating how the fibrous nodule clunks out of the intercondylar notch with extension of the knee.

View larger version (151K): [in this window] [in a new window]   Fig. 6-C Intraoperative photograph demonstrating the suprapatellar fibrous nodule.

The recommended treatment includes open or arthroscopic²⁹³ débridement of the fibrous nodule, with or without revision of the patellar component if it is malpositioned superiorly.

Rupture of the Extensor Mechanism
Rupture of the quadriceps tendon or the patellar ligament is an infrequent complication of total knee arthroplasty, with a reported prevalence of 0.17 per cent (fourteen of 8288 procedures)²³⁴ to 2.5 per cent (seven of 281 procedures)¹⁷⁶. The quadriceps tendon ruptures more frequently in patients who have had a lateral retinacular release, perhaps because of devascularization of the tendon or extension of the release too far anteriorly and disruption of the tendinous fibers of the quadriceps²²⁷. The results of operative repair are often suboptimum because of an extensor lag, weakness, or a limited range of motion.

The risk of a rupture of the patellar ligament is increased in patients who have had a previous operation involving the knee and in those who have had a partial release of the patellar ligament to enhance exposure at the time of an arthroplasty. Additional risk factors include closed manipulation of the knee and osteotomy of the tibial tubercle for realignment of the extensor mechanism²³⁴. Numerous methods of treatment have been used, including application of a cast; ligament suture; fixation with wires, staples, or screws; ligament augmentation; and reconstruction of the ligament with use of an extensor mechanism allograft⁶⁸. No single reconstructive procedure has provided consistently satisfactory results. Persistent rupture of the ligament after treatment is common and was noted in eleven of eighteen knees in the study by Rand et al.²³⁴. Ligament rupture remains one of the most dreaded complications of total knee arthroplasty, with difficult and often unsatisfactory options for salvage. Prevention with meticulous operative technique is imperative⁵⁰.

Principles of Operative Technique
If the accuracy of techniques of preparation for insertion of femoral and tibial components is compared with that for insertion of patellar components, it is logical to attribute current patellar problems, in some part, to operative technique. Appropriate operative goals should include accurate patellar resection, maintenance of patellar vascularity, proper positioning of prosthetic components, avoidance of soft-tissue impingement, and central patellar tracking.

The amount of patellar bone excised should ideally be equal to the thickness of the patellar component to be inserted (usually about ten millimeters), thereby restoring the preoperative patellar thickness^{57,96,222,231}. Patellar resection must result in a symmetrical patellar remnant with medial and lateral facets of equal thickness.

Efforts to preserve the vascularity of the patella have included maintenance of the fat pad^{37,52,158,280}, preservation of the lateral superior genicular artery during lateral retinacular release^{37,52,231,280}, and performance of the lateral release two centimeters posterior to the patella in order to maintain penetration of the patella by peripheral vessels^227,231. Avoiding the use of a patellar component with a large central fixation peg helps to preserve the intraosseous blood supply³⁷.

Accurate positioning of all three total knee components is critical. Medial shift and internal rotation of both the femoral and the tibial component and lateral positioning of the patellar component must be avoided to prevent patellar maltracking^78,197. After release of the tourniquet, central patellar tracking must be obtained with use of the no-thumb technique^134,196,264. If patellar subluxation is present, realignment procedures should be done to obtain a balanced extensor mechanism.

Isolated revision of the patellar component has been associated with a higher-than-expected rate of complications, which have included patellar fracture, instability, polyethylene wear-through, infection, peroneal nerve palsy, and extensor lag²². Removal of a well fixed metal-backed patellar component with osseous growth into the anchoring pegs can be difficult but is facilitated by disruption of the peg-plate junction with a diamond-edge saw to gain direct access to the bone-peg interface⁵¹.

Because of the numerous complications that have been associated with patellar resurfacing, many surgeons currently avoid the procedure. Although most surgeons agree that, in order to minimize the antigenic response of retained articular cartilage, it is necessary to resurface the patella in a patient who has rheumatoid arthritis^265,280, controversy remains with regard to the need to resurface a healthy-looking patella in a patient who has osteoarthrosis. Some authors²⁷⁶ have reported similar results with and without patellar resurfacing. Others have reported an increased prevalence of patellofemoral problems, particularly anterior knee pain, after total knee arthroplasty performed without patellofemoral resurfacing^{27,138,222,224,225,247}. Boyd et al.²⁷, in a review of the results of 891 arthroplasties performed with and without patellar resurfacing, reported complication rates of 4 per cent (sixteen of 396 procedures) and 12 per cent (fifty-eight of 495 procedures), respectively. Better results were achieved when patellar resurfacing was performed at the time of the primary arthroplasty than when it was performed as a secondary procedure. If the surgeon chooses not to resurface the patella, the ideal patient is one who has osteoarthrosis and excellent remaining articular cartilage and in whom central patellar tracking can be ensured at the time of the arthroplasty.

In our opinion, the best results of total knee arthroplasty are obtained when maximum attention is paid to accurate patellar resection, patellar vascularity is maintained, central patellar tracking is ensured, and metal-backed patellar components are avoided.

	Stiffness

Top Introduction Wound Complications Neurovascular Complications Infection Thromboembolic Disease Problems Related to the... Stiffness Supracondylar Fracture of the... References

 
The term stiffness as it relates to total knee replacement has several different meanings that are essentially observer-dependent. From the perspective of the surgeon, stiffness means an inadequate or smaller-than-expected range of motion as measured in a standardized fashion with the patient on an examination table. Active or active-assisted ranges of motion routinely are measured under optimum conditions during the recovery period, and the norms for motion following total knee replacement have been generated on the basis of these data^{81,210,242,262}. Functional capacity also is evaluated to confirm that the clinically derived value for range of motion corresponds with an appropriate level of function (walking, sitting, climbing stairs, and so on)^199,242. A patient who has a range of motion of 90 degrees of flexion to within 10 degrees of full extension on clinical examination and has no pain or functional difficulties is not said to have a stiff knee. However, a patient who, at one year after the arthroplasty, has clinically acceptable motion but also has knee stiffness, difficulty getting out of a chair, pain when climbing stairs, and an observable stiff-knee gait should be evaluated further for underlying problems involving the knee.

From the perspective of the patient, the problem of stiffness has different dimensions that should be integrated into the over-all clinical picture. Although stiffness is closely related to pain, it has a wider application to the patient's experience in attempting to move the knee, particularly during the early postoperative period. Stiffness therefore is closely related to the patient's motivation to achieve a functional range of motion and his or her willingness to endure pain to achieve that goal. For example, a patient who has minimum supportive care at home and must get out of bed for every need probably complains of more stiffness in the knee than one who is receiving total support from family members or nursing-facility staff even though the reported levels of pain may be similar. This little-studied phenomenon may have strong implications for the patient's ultimate assessment of range of motion and functional capacity.

As stiffness is nearly always present during the early postoperative period and gradually decreases over time, it is a valuable marker of improvement throughout the recovery period. Postoperative pain is the most important early cause of knee stiffness. It results in both quadriceps and hamstring guarding and makes passive flexion and extension difficult to perform. This factor was the theoretical basis for the implementation of in-hospital continuous passive motion^38,246. The continuous-passive-motion device cradles the leg and slowly moves it through a prescribed range in order to minimize the guarding response. Regardless of whether it actually minimizes the guarding response, continuous passive motion has not been conclusively shown either to shorten the hospital stay or to increase the range of motion substantially after total knee replacement; therefore, its value in the early postoperative period is questionable when the added cost of this modality is considered. Nevertheless, continuous passive motion within the hospital environment has been generally well accepted, even to the point of its being expected as standard treatment by many patients. It should not be viewed as a substitute for the persistence and encouragement of an experienced physical therapist^199,262. In addition to their role in helping the patient to obtain the desired motion and functional capacity, physical therapists serve in an educational capacity and are well positioned to note early problems with motivation and compliance. This latter contribution is particularly important as the lengths of hospital stays continuously decrease. The lack of direct supervision and the unpredictable quality of home or outpatient physical therapy within the managed-care environment demand that patients who are at high risk for the development of knee stiffness be identified before they leave the hospital.

Postoperative stiffness of the knee usually subsides within six to eight weeks. Range of motion generally improves steadily during the first three months, after which less rapid progress may be seen for an additional nine months or more^242,262. A limited or decreasing range of motion may be indicative of a number of complications, including infection, mechanical complications related to the implant or the soft tissue, impending arthrofibrosis, and reflex sympathetic dystrophy (if the symptoms include severe pain and vasomotor skin changes)¹⁹⁹.

The late onset of knee stiffness after a relatively symptom-free period also may suggest one of several conditions, including infection; overuse synovitis or tendinitis (particularly in a younger, more active patient); synovitis secondary to rheumatoid arthritis, particulate wear debris, or recurrent hemarthrosis; or loosening or breakage of the implant⁷⁴.

Infection
Early infection (within the first six weeks after the operation) is characterized by increasing swelling, erythema, and generalized pain, with or without wound drainage. All of these findings also may be present in a non-infected knee during the immediate postoperative period. The progressive nature of the signs and symptoms, especially after two to three days of rest and immobilization, should lead to early recognition of infection. Late infection is recognized more easily because it develops after a relatively asymptomatic period, although aspiration and culture may be necessary to distinguish an indolent infection from the other causes of synovitis listed previously.

Mechanical Problems Related to the Implant or the Soft Tissue
Dorr et al.⁵⁸ found that patients who had an excellent clinical result after total knee replacement with either a posterior-cruciate-retaining or a posterior-cruciate-sacrificing design continued to walk with a stiff-knee gait two years postoperatively. These findings suggest that total knee replacement rarely produces a completely normal gait and that some degree of stiffness is associated with even an excellent result. The proper balance of motion, strength, and stability is the goal for a good functional result. Inadequate bone resection combined with persistent ligamentous imbalance or tightness may result in knee stiffness⁶⁵. If symmetrical or asymmetrical tightness is recognized during trial reduction, it can be corrected by revision of the bone cuts or release of the ligaments, or both. If a flexion contracture is present, additional resection of bone from the distal part of the femur or a posterior capsular release, or both, should be performed. If the residual contracture is severe (more than 15 degrees), some additional bone may be removed from the proximal part of the tibia, provided that doing so does not make the flexion gap too wide.

The approach to bone resection in total knee arthroplasty is highly dependent on whether the posterior cruciate ligament is to be preserved or sacrificed^118,135,199. When the ligament is to be preserved, the femur usually is cut first in order to preserve the level of the joint line and to approximate more closely the normal kinematics of the knee. Variable amounts of tibial bone must be resected to provide the proper alignment and stability while preserving and balancing the tension of the posterior cruciate ligament in both flexion and extension. A potential pitfall during this procedure is reversal of the tilt of the tibia in the sagittal plane, which causes tightening of the posterior cruciate ligament in flexion if the rollback mechanism functions according to design. Alternatively, the tibia actually may drop back, thereby altering the patellofemoral mechanics¹³⁵. The problem of tightness in flexion is most important from the standpoint of postoperative stiffness of the knee. If tightness is recognized intraoperatively, recession of the posterior cruciate ligament can be considered or the tibia can be cut again in neutral or with a 5-degree posterior slope. If there is excessive posterior instability due to laxity of the posterior cruciate ligament, a cruciate-substituting design may be selected. Hirsch et al.¹¹⁸ reported that the clinical results achieved with use of a posterior-cruciate-sacrificing device were no different than those achieved with use of a posterior-cruciate-retaining device.

Use of an oversized femoral component or posterior placement of the femoral component may lead to a disproportionately narrow flexion gap. It is difficult to treat this problem by resecting more tibial bone, especially if the extension gap is adequate, because doing so may lead to an unacceptable amount of laxity in extension. Use of a smaller femoral component and resection of more bone from the posterior aspect of the femur expands the flexion gap without affecting stability in extension.

Inadequate release of tight capsular and ligamentous structures is an important cause of stiffness after total knee arthroplasty but is difficult to measure. Poor flexion and extension may result from inadequate release or recession of a tight posterior cruciate ligament. Flexion contractures most commonly result from inadequate posterior capsular release in conjunction with insufficient bone resection. In varus deformities, the medial collateral ligament and, in valgus deformities, the lateral collateral ligament and the iliotibial band often must be released in order to prevent asymmetrical wear of the implant and to promote an optimum range of motion of the knee. External rotation of the femoral component has been found to enhance ligament-balancing in flexion and to facilitate optimum patellar tracking^{5,168,240,269}.

Patellofemoral dysfunction may cause pain that promotes stiffness because of disuse^74,176,269. Conversely, patellofemoral pain may result from knee stiffness, particularly with flexion contractures. A number of possibilities related to the patella should be considered during the evaluation of stiffness after a total knee arthroplasty: a patella that was not resurfaced, inadequate lateral release, asymmetrical cutting of the patella, excessive elevation of the joint line, internal rotation of the femoral component, formation of intra-articular adhesions that tether the patella to surrounding structures (thereby altering the normal tracking mechanism)^175,288, patellar fracture, and loosening of the patellar component.

Finally, the generation of an excessive volume of wear debris over time may cause synovitis, with pain, stiffness, and swelling being the usual clinical result.

Patient-Related Factors
The patient's preferences, expectations, and satisfaction with elective procedures such as total knee replacement recently have received attention as being important indicators of the likelihood of obtaining a good outcome. Preoperative education is important to provide the patient with an understanding of his or her own goals in light of the actual risks and benefits of an operation. The educational process gives the surgeon an opportunity to recognize patients who have unrealistic expectations or inadequate motivation to comply with the postoperative regimen. Patients who have potential problems that may require additional services should be identified as soon as possible so that hospital utilization-review panels and insurers can be notified of the additional needs that may arise.

Host factors that promote arthrofibrosis around the replaced knee joint are not well understood. They should be studied further because it is apparent that certain patients are predisposed to early knee stiffness and unusual amounts of pain and swelling in the absence of infection, bleeding, or mechanical complications²⁷⁹.

Diagnostic Considerations

Physical Examination
The physical examination is the most important diagnostic tool in the evaluation of a patient who has stiffness after a total knee replacement. At least two examinations should be done within the first six weeks to ensure acceptable progress with regard to range of motion and function. Patients who are having problems in these areas should be seen more frequently. Unexpected restriction of the range of motion should be assessed in light of other findings such as swelling, effusion, erythema, skin viability, and drainage.

Radiographic Evaluation
Plain anteroposterior, lateral, and tangential patellar radiographs should be made within the first six weeks and repeated if stiffness and pain increase. Findings associated with stiffness of the knee may include inadequate bone resection, an oversized femoral implant, gross maltracking or subluxation of the patella, or a combination of these.

Bone-scanning is indicated when late stiffness develops after an asymptomatic period. This technique is less useful during the early recovery period and throughout the first postoperative year, when it normally can be expected to demonstrate increased uptake around the implants. Implants inserted without cement tend to be associated with increased bone-scan activity for an even longer period of time²¹.

Aspiration and Culture
When a patient has early progressive stiffness, pain, and swelling, aspiration and culture of the joint fluid should be performed in order to rule out infection. A negative culture, however, does not absolutely rule out infection. If an infection is highly suspected, an arthrotomy may be necessary to obtain tissue for a positive culture. If symptoms develop after a relatively asymptomatic period of one year or more, the joint aspirate also should be examined with polarized light microscopy for evidence of polyethylene wear debris²¹.

Treatment Alternatives

Physical Therapy
The most important initial treatment of a stiff, non-infected knee that appears radiographically satisfactory after a total knee arthroplasty is an adequately supervised course of sustained, intensive physical therapy. This therapy may last from three to six months, depending on the initial results. If some progress is being made and the patient can tolerate the discomfort, the treatment program should be continued.

Manipulation
If range of motion reaches a plateau during the first three months, manipulation of the knee with the patient under regional or general anesthesia should be considered. Manipulation is not necessary within the first postoperative month. In an assessment of the range of motion one year after a total knee replacement, Fox and Poss⁸¹ found that knees that had been manipulated two weeks postoperatively could not be distinguished from those that had not. Moreover, there was a substantial loss of motion during the week after the manipulation. The preoperative range of motion is an important predictor of the range after total knee arthroplasty^210,262. Parsley et al.²¹⁰ reported that seventeen knees that had less than 75 degrees of preoperative flexion gained a mean of 16 degrees (from 61 to 77 degrees), while 257 knees that had more than 95 degrees of preoperative flexion lost a mean of 6 degrees (from 115 to 109 degrees). Knowledge of the preoperative flexion helps the surgeon and the patient to formulate goals for motion and to identify a reasonable threshold for postoperative manipulation.

Débridement
If manipulation of the knee does not lead to a sustained, acceptable improvement in the range of motion, exploration and débridement of the knee may be performed with either open or arthroscopic technique. Good results have been achieved when arthroscopic débridement has been performed for localized tethering of the patella or for fibrous nodules that cause clunking of the patella over the anterior flange of the femoral component^175,288. These conditions, however, usually are not associated with substantial loss of motion. The results of arthroscopic treatment of generalized arthrofibrosis after total knee replacement have not been as good^24,279; in one report²⁴, two of seven patients subsequently had an arthrodesis of the knee and two others were scheduled to have this salvage operation. The results of either open or arthroscopic débridement of a stiff knee after a total knee replacement probably are related most closely to the extent of the intra-articular fibrosis.

Revision
Revision with a modular tibial polyethylene spacer in conjunction with a capsular or ligamentous release may improve the range of motion of the knee, particularly when the procedure is performed to correct a flexion contracture. Intraoperatively, the deformity should be corrected completely with a new, trial spacer in place. If complete correction cannot be achieved, the tibial or the femoral component, or both, should be revised after new cuts are made in the bone to provide optimum flexion and extension gaps. A posterior-cruciate-substituting design should be used whenever both components are revised. This design more readily accommodates alterations in the joint line caused by the new cuts in the bone, and it has the inherent stability to allow generous flexion and extension gaps as well as ligamentous release^11,199,281.

During the revision, it is very important to release fully all structures that may have contributed to stiffness of the knee, including the quadriceps tendon and the vastus intermedius adhesion to the femur and the suprapatellar pouch, the medial and lateral gutters, the collateral ligaments, and the lateral patellar retinaculum²²³. In severe cases, the integrity of the extensor mechanism must be guarded carefully. Avulsion of the patellar ligament from the tibial tubercle is a potentially devastating complication. It can be prevented with use of a systematic approach in which the releases noted previously are utilized and the tendon insertion is sutured and reinforced when appropriate^145,176.

Prevention of Stiffness following Total Knee Replacement
The most fundamental consideration in the prevention of complications of total knee replacement in general and of stiffness in particular is the selection of an implant and an instrumentation system that are complex enough to allow flexibility yet simple enough to minimize the chances of technical error. The selection should be based on a published track record of satisfactory performance over a period of five to ten years, and the technical difficulty should be compatible with the proficiency and experience of the surgeon. Like a normal knee, a total knee prosthesis tolerates tightness (stability) and laxity (flexibility) throughout a given range of motion. In general, a design with less inherent stability or constraint requires more exacting bone cuts and ligament-balancing to deliver an acceptable result. This applies to many posterior-cruciate-sparing designs, particularly those intended to be inserted without cement. Cruciate-substituting designs that are inserted with cement have more inherent stability and better tolerate the extensive ligamentous releases that are necessary for correction of severe varus or valgus deformities. Elevation of the joint line is also better tolerated by posterior-cruciate-substituting implants^11,269. Therefore, posterior-cruciate-substituting designs offer at least a theoretically wider margin of safety. The definitive answer to the problem of selection of implants can be provided only through the implementation of a broad-based outcome database for total knee replacement.

Knowledge of a patient's expectations, goals, and motivation is essential for early detection of potential problems associated with stiffness following total knee replacement. Poor motivation on the part of the patient, little or no preoperative education regarding the procedure, a short hospital stay, and a marginally delivered program of home or outpatient physical therapy constitute a dangerous mix that may result in a less-than-optimum result. A strategy of early identification of problems should be formulated, and appropriate treatment pathways for these outliers should be constructed and tested with the goal of ultimately preventing the harmful and costly long-term effects of stiffness following total knee replacement.

	Supracondylar Fracture of the Distal Part of the Femur

Top Introduction Wound Complications Neurovascular Complications Infection Thromboembolic Disease Problems Related to the... Stiffness Supracondylar Fracture of the... References

 
A fracture of the distal part of the femur proximal to a total knee-replacement presents a challenging problem, as indicated by the reported results of treatment^{1,25,46,77,122,137,177,195,207,243,256,275}. In thirteen studies that appeared in the orthopaedic literature from 1981 to 1989, a good or excellent result was achieved for fifty-four (69 per cent) of seventy-eight patients in whom such a fracture had been treated operatively compared with sixty-five (68 per cent) of ninety-five patients who had been managed non-operatively. Complications of treatment included malalignment, loss of motion, non-union, infection, and a number of problems associated with prolonged immobilization. Proponents of internal fixation believe that operative treatment best restores mechanical alignment to the limb, permits early mobilization to avoid the complications of prolonged bed rest, and may maximize the healing potential through stable fixation in a region in which the blood supply is already compromised^259,313. Current recommendations include both operative and non-operative treatment of appropriately selected supracondylar fractures proximal to a total knee replacement.

The prevalence of supracondylar fractures after total knee arthroplasty is approximately 1 per cent, with reported rates ranging from 0.5 per cent (twenty-eight of 5233 patients) to 2 per cent (five of 250 patients)^{1,25,46,195,275}. These fractures have been associated with rheumatoid arthritis, chronic steroid therapy, and other conditions that result in osteopenia of the distal part of the femur (Fig. 7). Other, less common contributing factors have included medication-induced osteopenia or an unsteady gait in patients who have a neurological disorder^46,275. Also, arthrofibrosis after a total knee replacement may predispose to fracture by increasing stress in the distal femoral metaphysis, particularly at the time of manipulation^46,111. The association between notching of the anterior aspect of the distal part of the femur during total knee replacement and subsequent supracondylar fracture has been debated. Aaron and Scott¹, in a retrospective review of the results of 250 total knee arthroplasties, reported that five of twelve patients in whom notching of the anterior cortex of the distal part of the femur had occurred at the time of the operation subsequently sustained a supracondylar fracture. They concluded that notching of the distal part of the femur predisposes the patient to subsequent supracondylar fracture. In contrast, Ritter et al.²⁴³ reviewed the records of 180 patients who had anterior femoral notching in association with total knee arthroplasty and found that only one patient subsequently had a supracondylar fracture. Most authors have agreed, however, that notching of the anterior part of the femur during total knee replacement is to be avoided and probably is of more clinical importance in osteopenic bone^1,46,77,243.

View larger version (104K): [in this window] [in a new window]   Fig. 7 Anteroposterior and lateral radiographs of a supracondylar fracture in a patient who had osteopenic bone.

Non-operative treatment is recommended for non-displaced fractures as well as for minimally displaced fractures when alignment of the fracture and the mechanical axis of the limb are easily achieved and maintained with closed reduction (Figs. 8-A, 8-B, 8-C through 8-D)^113,245. The patient wears an above-the-knee cast for three weeks and is allowed to bear weight on the affected limb as tolerated during this period. Three weeks after the fracture, a cast-brace is applied and range-of-motion exercises are begun. The cast-brace is worn until there is radiographic evidence of callus and the fracture has healed clinically.

View larger version (125K): [in this window] [in a new window]   Figs. 8-A through 8-D: Anteroposterior and lateral radiographs of an impacted supracondylar fracture proximal to a total knee replacement in a patient who had rheumatoid arthritis.

View larger version (132K): [in this window] [in a new window]   Figs. 8-A and 8-B: Before treatment. The normal alignment of the limb has been maintained.

View larger version (89K): [in this window] [in a new window]   Fig. 8-C After closed treatment, which led to an excellent result.

View larger version (113K): [in this window] [in a new window]   Fig. 8-D After closed treatment, which led to an excellent result.

View larger version (115K): [in this window] [in a new window]   Figs. 9-A through 9-D: Anteroposterior and lateral radiographs of a sixty-eight-year-old patient who sustained a displaced supracondylar fracture of the distal part of the femur two years after a total knee replacement.

View larger version (132K): [in this window] [in a new window]   Figs. 9-A and 9-B: Before treatment.

View larger version (76K): [in this window] [in a new window]   Fig. 9-C Six months after operative stabilization with a locked supracondylar nail.

View larger version (69K): [in this window] [in a new window]   Fig. 9-D Six months after operative stabilization with a locked supracondylar nail.

The intramedullary nail inserted in a retrograde manner through the knee joint is a new device that has been used successfully to treat supracondylar fractures proximal to knee replacements^{115,116,144,182,245}. Intramedullary fixation provides an attractive alternative to lateral plate fixation because of the simplicity of both the instrumentation system and the technique used for insertion of the nail. In addition, intramedullary fixation is biomechanically stronger and less prone to failure than lateral plate fixation^115,116,245. Intramedullary nails are load-sharing devices that may have some inherent advantages, particularly when used to manage patients who have a supracondylar fracture proximal to a knee replacement as they typically have osteopenia of the distal femoral metaphysis.

The operative technique for successful internal fixation of a supracondylar fracture with use of a lateral plate and screws is exacting. High-quality anteroposterior and lateral radiographs must be available preoperatively. The surgeon should carefully assess the level of the fracture, the degree of comminution, and the quality of the cortical bone before choosing the type of lateral plate-and-screw system to be used. The patient is placed in the supine position on a radiolucent operating table to allow for use of the c-arm image-intensifier intraoperatively. A hip roll is placed beneath the ipsilateral hip to rotate the lower extremity internally, and a sterile tourniquet can be used. The fracture should be approached through the previous anterior midline incision, which can be extended laterally and proximally and continued in the midline off the tibial crest distally to provide exposure. The creation of a separate lateral incision, as is typically done for patients who have not had a previous knee replacement, places the soft tissue at risk. This is especially true in the region of the tibial tubercle, where the lateral incision comes close to the anterior scar from the previous knee replacement.

An indirect reduction technique should be used to reduce these fractures intraoperatively¹⁹¹. Dissection of the soft tissues medially should be avoided to prevent disruption of the important blood supply from this area^191,260. The use of a femoral distractor or a simple external fixation frame helps the surgeon to achieve a satisfactory preliminary indirect reduction¹⁶³. A Steinmann pin can be inserted and used as a joystick to manipulate the distal fragment. Once reduction is achieved, the Steinmann pin can be driven across the fracture to provide preliminary fixation until the plate and screws are applied (Figs. 10-A and 10-B). Autogenous iliac-crest cancellous-bone graft should be added if there is marked comminution of the fracture.

View larger version (115K): [in this window] [in a new window]   Fig. 10-A Anteroposterior and lateral radiographs made six months after open reduction and internal fixation of a supracondylar fracture of the distal part of the femur with use of a condylar buttress-plate.

View larger version (58K): [in this window] [in a new window]   Fig. 10-B Anteroposterior and lateral radiographs made six months after open reduction and internal fixation of a supracondylar fracture of the distal part of the femur with use of a condylar buttress-plate.

Revision total knee replacement with use of a long-stem femoral component is recommended for all patients who have loosening of the femoral component in association with the supracondylar fracture. As stability of the femoral component may be difficult to determine on the basis of preoperative radiographs, it is recommended that instruments and prosthetic components necessary for revision total knee replacement be available at the time that internal fixation is undertaken. During the revision, the collateral ligaments must be retained and extrusion of cement into the fracture must be avoided. Whenever there is comminution in the region of the origin of the collateral ligaments, a modular metaphyseal femoral replacement (the type of prosthesis used after the resection of tumors) or a combination of a distal femoral allograft and a revision femoral component with an intramedullary stem may be used¹⁶³.

The results obtained with the operative techniques and devices described here that were developed during the 1990's have been markedly better than those of methods described earlier in this section^{113,115,116,182}. Healy et al.¹¹³ reported the results for twenty patients who had been managed with open reduction and internal fixation with use of a condylar blade-plate (seven patients), a condylar compression plate (seven patients), or a condylar buttress-plate (six patients); in addition, fifteen of the twenty patients had been managed with bone-grafting. Union was achieved, without the need for an additional operation, in eighteen of the twenty patients by a mean of sixteen weeks (range, six to twenty-six weeks). In the remaining two patients, union was achieved after a second procedure involving autologous bone-grafting. Ten of the twenty patients had a delayed union (radiographic signs of union were not evident until more than four months after the operation). McLaren et al.¹⁸² reported on seven patients in whom a supracondylar fracture proximal to a total knee replacement had been treated with a supracondylar nail. Radiographic evidence of union was noted in six patients by six weeks, and complete union was achieved in all seven patients by twelve weeks. In a large, multicenter study¹¹⁶ of forty-one such fractures that were treated with internal fixation with a locked intramedullary nail, delayed union occurred in three patients and a non-union, in one. The mean time to union for the remaining thirty-seven patients was thirteen weeks.

	Footnotes

 
*Printed with permission of The American Academy of Orthopaedic Surgeons. This article will appear in Instructional Course Lectures, Volume 46, The American Academy of Orthopaedic Surgeons, Rosemont, Illinois, March 1997.

No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.

Department of Orthopaedic Surgery, State University of New York Health Science Center at Syracuse, 550 Harrison Center, Suite 100, Syracuse, New York 13202. E-mail address for Dr. Ayers: ayersd@vax.cs.hscyr.edu.

Denver Orthopaedic Specialists, 1601 East 19th Avenue, Suite 5000, Denver, Colorado 80218.

¶Department of Orthopaedic Surgery, Temple University Hospital, 3401 North Broad Street, Philadelphia, Pennsylvania 19140.

#Department of Orthopaedics and Rehabilitation, The Milton S. Hershey Medical Center, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, Pennsylvania 17033-0850.

	References

Top Introduction Wound Complications Neurovascular Complications Infection Thromboembolic Disease Problems Related to the... Stiffness Supracondylar Fracture of the... References

 

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