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The Journal of Bone and Joint Surgery (American). 2009;91:3008-3018. doi:10.2106/JBJS.I.01062 © 2009 The Journal of Bone and Joint Surgery, Inc. What's New in Adult Reconstructive Knee Surgery
1 Department of Orthopaedic Surgery, 3B Orthopaedics, Lankenau Hospital, 100 Lancaster Avenue, Suite 250, Wynnewood, PA 19096
Specialty Update has been developed in collaboration with the Council of Musculoskeletal Specialty Societies (COMSS) of the American Academy of Orthopaedic Surgeons.
The purpose of this review is to discuss the research presented on selected topics related to adult knee reconstruction during the year 2008. The articles referenced in this update were selected from both The Journal of Bone and Joint Surgery (American Volume) and The Journal of Arthroplasty, as well as select articles from Clinical Orthopaedics and Related Research. All prospective randomized studies related to total knee arthroplasty that were published in these journals in 2008 were reviewed. Other studies were included on the basis of their relevance to the topics that were chosen to be discussed.
Several studies in 2008 focused on economic considerations related to total knee arthroplasty. In response to potential changes in the Medicare payment policy, Bozic et al.1 analyzed the influence of patient and procedure characteristics on resource utilization during joint arthroplasty. Economic, demographic, and surgical data on 6483 patients who were managed with primary and revision arthroplasty at four high-volume arthroplasty centers were used to identify the predictors of resource utilization. The authors found that, in addition to the patient's severity of illness, surgical complexity was a predictor of resource utilization during joint arthroplasty procedures. These data are critical for guiding the Medicare payment policy, for more accurately matching reimbursement rates to resource utilization, and for reducing the incentive to selectively manage patients who utilize fewer resources. Bhattacharyya et al.2, in a report on the results of a trial pay-for-performance program, identified hospital characteristics that were associated with success in such programs. The Centers for Medicare and Medicaid Services (CMS)/Premier Hospital Quality Incentive Demonstration project includes 257 hospitals that participate in the hip and knee modules of the program. Performance in the care of primary total hip and knee arthroplasties was judged according to three process measures (preoperative antibiotic start time within one hour, postoperative antibiotic discontinuation time within twenty-four hours, and antibiotic choice) and also three risk-adjusted index outcome measures (hematoma or hemorrhage, avoidance of metabolic derangement, and avoidance of readmission). The authors found that status as a teaching hospital, high arthroplasty volumes, and location in the Midwestern United States are independent factors that are associated with success in a pay-for-performance system. These hospitals also were more specialized in orthopaedic surgery and exhibited a higher case-mix index. Bozic and Chiu3 also studied pay-for-performance programs and quality reporting. They reviewed claims data from a commercially insured population over a two-year period and searched for an association between adherence to payer-defined guidelines and patient outcomes. Guidelines included measures such as the timing of preoperative radiographs, the timing from referral to surgery, the use of injections and physical therapy, and the one-year reoperation rates. Interestingly, the authors found a wide variation of adherence to guidelines among surgeons and found no significant correlation between adherence to guidelines and costs or patient outcomes. We can conclude from these studies that quality reporting and pay-for-performance programs are expected to reduce costs and to improve patient outcomes. It is critical that the chosen measures are evidence-based guidelines that will foster true improvements so that they actually improve care and not just increase the documentation and consistency of practices that are not clinically effective. Optimally, leaders in orthopaedics with an interest in evidence-based medicine will work together with payers and policy-makers to generate guidelines that will result in true improvements in care. Rosenberg et al.4 reported on improvement in the timing of antibiotic prophylaxis at their institution by implementation of an antibiotic "time-out" protocol. Over a seven-week study period, patients undergoing an arthroplasty or spine procedure did not have the surgical incision until a "time-out" process, including the verification of antibiotic timing, had been completed. Use of this antibiotic "time-out" protocol improved the adherence to antibiotic timing guidelines from 65% in the three months before the study to 97% in the eighteen months after completion of the study. The study was not designed to reveal actual differences in patient outcomes or complications, but it revealed methods by which a hospital can adhere more consistently to guidelines.
Unicompartmental knee arthroplasty continues to play a major role in the treatment of patients with unicompartmental arthritis. Riddle et al.5 examined data from three implant manufacturers and also reviewed the procedure database from forty-four hospitals to estimate the relative rate of unicompartmental replacements implanted per year in the United States. From 1998 to 2005, the rate increased an average of 32.5% annually over the study period (from 6570 to 44,990 implants), which was significantly greater than the 9.4% average increase in the number of total knee arthroplasties over the same time period. The authors went on to point out that, despite the rapid increase in the number of unicompartmental procedures, they still account for <8% of all knee arthroplasty procedures performed annually in the United States. Robertsson and Lidgren6 analyzed the short-term results of three different unicompartmental knee arthroplasty implants in the Swedish registry over four different time periods. They not only examined the cumulative revision rates of the implants over the time periods but also considered the introduction of minimally invasive approaches and instrumentation in the context of outcomes. During the most recent time period examined (1999 to 2004), all implants had a cumulative revision risk of <10% at five years after unicompartmental knee arthroplasty. While the introduction of minimally invasive techniques did not affect the cumulative revision rates of two types of implants, another manufacturer's implant appeared to have an increased revision rate when minimally invasive approaches were introduced without adequate instrumentation. The authors interpreted the results as indicating the importance of having proper instrumentation and surgeon education when beginning to utilize minimally invasive approaches. Emerson and Higgins7 retrospectively reviewed the twelve-year results for fifty-five knees that were treated with a mobile-bearing unicompartmental knee arthroplasty. At the time of the ten-year follow-up, they reported an 85% survival rate, with six patients requiring a revision to a total knee arthroplasty. Four knees were revised because of progressive lateral arthritis over an average of ten years, but there was no correlation with alignment or tibial component thickness and the development of lateral compartment osteoarthritis. Only one femoral component loosened over the time period. The authors observed no failures due to tibial loosening, wear, or subsidence. Sah and Scott8 reported the intermediate-term results of forty-nine fixed-bearing lateral unicompartmental knee arthroplasties that were performed through a standard medial parapatellar approach over a thirteen-year period. After an average of five years of follow-up, the Knee Society knee score improved from 39 to 89 and the functional score improved from 45 to 80. Preoperative alignment was corrected from an average of 10° of valgus to an average of 6° of valgus. There were no revisions or soft-tissue complications. Knee Society scores were significantly worse for the ten patients with posttraumatic arthritis that had developed after a lateral tibial plateau fracture. Both medial and lateral unicompartmental knee arthroplasties appear to provide excellent results with good survival rates at ten years. Although excellent long-term results after unicompartmental knee arthroplasty have been described in the literature, there also have been reports of early failures due to a variety of mechanisms. Aleto et al.9 retrospectively reviewed their experience with thirty-two consecutive revisions of a medial unicompartmental knee arthroplasty to a total knee arthroplasty. The average age of the patients at the time of revision was sixty-six years, and the average body mass index was 33.6 kg/m2. The implants that were reviewed included ten metal-backed tibial components and twenty-two all-polyethylene tibial implants of various designs. The average time to revision was 5.7 years, and, in fifteen of the thirty-two cases, the mechanism of failure was collapse of the medial tibial plateau. Other causes of failure included progressive tricompartmental arthritis (six cases), aseptic loosening (six cases), component failure (four cases), and polyethylene wear (one case). The authors found significantly more tibial defects when the mechanism of failure involved collapse of the medial tibial plateau, more often necessitating the use of screws, augments, or stems during the revision total knee arthroplasty. Although there was no significant correlation between body mass index and the mode of failure, patients with medial tibial collapse had a significantly higher average age (seventy-one compared with sixty-one years; p = 0.01). Furthermore, it was significantly more likely for an all-polyethylene tibial component to fail as a result of collapse of the tibial plateau as compared with a metal-backed tibial component (87% compared with 53%; p = 0.04). When revising a failed unicompartmental knee arthroplasty because of collapse of the medial tibial plateau, the surgeon should anticipate the need for augments and stems. Masri et al.10 examined the early outcomes of unicompartmental knee arthroplasty in a select group of patients receiving Workers' Compensation. In this retrospective study, the authors measured the Knee Society score and determined the unicompartmental knee arthroplasty revision rate for nineteen patients receiving Workers' Compensation and twenty patients not receiving Workers' Compensation. The minimum duration of follow-up was two years, and the average duration of follow-up was approximately forty months in each group. Two patients in each group had a revision during the study period, for a total revision rate of 10%. Three revisions were performed because of a loose tibial component, and one revision was performed because of patellofemoral arthritis. There were no cases of femoral loosening. Despite the similar revision rates, patients receiving Workers' Compensation had significantly less improvement in Knee Society scores at the time of the most recent follow-up. Patients receiving Workers' Compensation had improvement in the average score from 47 preoperatively to 77 postoperatively, whereas those not receiving Workers' Compensation had improvement from 43 to 91 (p = 0.008). These were significant differences that could not be accounted for by other preoperative patient characteristics.
A variety of approaches to the knee have been successfully utilized for total knee arthroplasty. There has been recent interest in improving these approaches to limit soft-tissue disruption, to reduce pain, and to avoid some of the functional delays in recovery observed after total knee arthroplasty, but without paradoxically causing more local tissue trauma resulting from excessive traction due to limited exposure. Although certain early functional benefits appear to be derived from less-invasive approaches to total knee arthroplasty, it is not clear whether there will be long-term benefit or detriment. The midvastus approach involves an arthrotomy that is performed by dissecting diagonally away from the superomedial aspect of the patella into the vastus medialis muscle. Dalury et al.11 conducted a prospective randomized study to compare the electromyographic evaluation of the vastus muscle, radiographs, range-of-motion tests, and Knee Society scores for twenty patients undergoing bilateral total knee arthroplasty (with one arthroplasty being performed through a midvastus approach and one being performed through a medial parapatellar approach). At six weeks and at the time of the latest follow-up at twelve weeks, there were no significant differences in any of the measured parameters and there were no electromyographic or nerve-conduction abnormalities in the knees that had the midvastus approach. However, at the six-week follow-up, six of the twenty patients expressed a preference for the total knee implant that had been inserted through the midvastus approach, one had a preference for the implant that had been inserted through the parapatellar approach, and the remainder had no preference. It appears that the midvastus approach is a safe alternative to the parapatellar approach and may offer some early benefits. The authors suggested that sharp dissection of the vastus, with a closure that includes the capsule but excludes the muscle, may explain the avoidance of electromyographic abnormalities after the midvastus approach. The mini-subvastus approach, in which the arthrotomy is extended medially under the vastus medialis muscle, avoids incision of the quadriceps muscle and tendon. Schroer et al.12 retrospectively compared 150 total knee arthroplasties that had been performed through the mini-subvastus approach with 150 total knee arthroplasties that had been performed through the traditional medial parapatellar approach. Both groups of patients had similar characteristics and an identical perioperative management protocol. The authors found that patients who had been managed with the mini-subvastus approach were discharged earlier (3.4 compared with 4.1 days; p < 0.05), exhibited a more rapid recovery of quadriceps strength, were less likely to require inpatient rehabilitation, and had improved knee flexion over a two-year period. Comparison of the groups also showed no differences in terms of the number or severity of complications. In a subsequent study, Schroer et al.13 compared implant positioning in patients who underwent total knee arthroplasty with either a traditional medial parapatellar or a mini-subvastus approach, with use of computed tomography scans to determine alignment. Interestingly, there was a trend for increased accuracy in tibial alignment in the mini-subvastus group, perhaps resulting from improved tibial exposure. However, the mini-subvastus approach was also associated with a higher variance in average coronal femoral alignment (1.71° compared with 1.04°). The authors postulated that the increased variation in femoral alignment was due to shortcomings of the instrumentation and not to a lack of exposure. McAllister and Stepanian14 reported data from a retrospective study in which the early results of 100 consecutive minimally invasive total knee arthroplasties were compared with those of 100 consecutive conventional total knee arthroplasties. The minimally invasive group was defined by avoidance of patellar eversion and tibial dislocation, and the extremity was ideally positioned throughout surgery to maximize visualization and minimize retraction. A medial parapatellar arthrotomy was used in both groups, as was a standardized perioperative protocol of pain management, patient education, and hospital discharge. Patients who had a total knee arthroplasty without patellar eversion or tibial dislocation had a shorter inpatient stay (3.6 compared with 6.4 days; p < 0.01), less pain at the time of discharge as measured with a visual analog scale (3.2 compared with 3.8; p < 0.01), improved flexion for six months postoperatively (122° compared with 113°; p < 0.0001), and a lower rate of manipulation (2% compared with 14%; p < 0.001). By one year after surgery, there were no differences between the groups in terms of range of motion or functional outcome. There were no significant differences between the groups in terms of the complication rate or component positioning. It appears that the avoidance of patellar eversion and tibial dislocation improves the early results of total knee arthroplasty and reduces the need for manipulation in most patients. It must be emphasized that this technique requires specific technical considerations and is safe only when used by a properly educated surgeon.
The discussion about the role of computer navigation in total knee arthroplasty focuses on two primary issues. One is whether navigation improves the accuracy of implant positioning and extremity alignment; the other is whether improvements in the accuracy of implant positioning and alignment enhance clinical results and durability. Several studies that were published in 2008 addressed both of these issues. Lionberger et al.15 performed forty-six total knee arthroplasties with use of either an electromagnetic or an infrared navigation system. Postoperatively, component and limb alignment were assessed with both computed tomography and full-length radiographs. The authors found that the navigation systems resulted in comparable accuracy in terms of implant positioning, attaining <1° accuracy of the coronal and sagittal component positioning in 95% of the knees. The desired mechanical limb alignment was achieved in 93% of the procedures involving the use of electromagnetic navigation and 90% of the procedures involving the use of infrared navigation. The authors found that the femoral epicondylar axis was difficult to determine, leading them to suggest additional studies on establishing proper femoral rotation. Siston et al.16 similarly identified the difficulty of establishing the rotational axis of the distal part of the femur. They conducted a cadaver study in which they tested a variety of techniques (two kinematic and three anatomic) to establish femoral rotation. The anatomic techniques involved the use of the digitized epicondyles, the Whiteside line, and the posterior condylar line. Computed tomography of each cadaver knee was performed to determine the femoral rotational axis. The authors found that the kinematic methods of defining femoral rotation were neither more accurate nor more precise than the anatomic methods. Overall, the combined methods of attaining the femoral axis of rotation were more accurate than each individual method alone. For example, averaging the results of the epicondylar axis and the Whiteside line (mean error, 1.5°) was more accurate than each individual technique alone (mean error, 5.4° and –2.3°, respectively). The authors recommended the use of combined techniques to improve the accuracy of femoral component implantation when using navigation. Catani et al.17 measured the alignment deviation between osseous resection and final implant positioning with use of computer-navigation techniques. When bone resection was completed, the instrumented probe was used to measure the alignment of the tibial and femoral surfaces in three planes. After the final implants were cemented, the same measurements were repeated to allow the final implant positioning to be compared with that intended by the bone resection. The authors found that cementation and impaction of the components can result in further alteration in the final implant positions. This variation was >1° in the frontal plane of the femur in 20% of the cases, in the frontal plane of the tibia in 11%, and in the sagittal plane of the tibia in 33%. The deviation was found to be >2° in the sagittal plane of the tibia in 9% of the cases. Even with emerging technologies that provide for more accurate tibial and femoral bone resection, it must be kept in mind that there is still some error in alignment during component implantation when performing a total knee arthroplasty. Dutton et al.18 conducted a prospective randomized study that included 180 consecutive patients undergoing either a minimally invasive computer-assisted total knee arthroplasty or a traditional total knee arthroplasty. The minimally invasive group had an abbreviated parapatellar arthrotomy with patellar subluxation instead of eversion. All patients received the same perioperative pain-management protocol and adhered to the same discharge guidelines. Despite having a longer operative time (by an average of twenty-four minutes), the patients in the minimally invasive group were discharged from the hospital an average of one day earlier than those in the traditional total knee arthroplasty group (3.3 compared with 4.5 days; p < 0.001) and were more likely to walk independently for thirty minutes by one month after surgery (p = 0.04). The mechanical axis was within 3° of neutral in 92% of the patients in the study group, compared with only 68% of those in the traditional total knee arthroplasty group. The authors observed no complications related to minimally invasive computer-assisted total knee arthroplasty. Carter et al.19, in a retrospective study, described their initial experience with computer-assisted navigation and total knee arthroplasty in a community setting. Implant alignment was determined with computed tomography after 100 total knee arthroplasties performed with navigation and 100 conventional total knee arthroplasties. The authors found that more total knee replacements that had been performed with navigation demonstrated implant positioning within 3° of the surgical goal when compared with conventional total knee replacements, with the largest improvements being observed in the sagittal alignment of the implants. These studies demonstrated greater consistency in the achievement of neutral bone resection during total knee arthroplasties performed with use of computer navigation as compared with those performed with conventional techniques. However, whether the accuracy in bone resection corresponds with the alignment achieved at the time of implantation is in question17. Additionally, it remains to be seen whether these improvements in bone resection will impact functional outcomes and implant durability.
Improvements in the perioperative management of patients, including pain-management protocols and patient education, have significantly improved the early outcomes after total knee arthroplasty. There has been a trend toward the use of multimodal pain protocols, the avoidance of parenteral narcotics, and the encouragement of early walking in an effort to reduce postoperative pain, the length of inpatient stay, and the prevalence of medical complications such as ileus and deep-vein thrombosis. Dorr et al.20 reported the results of a prospective study involving thirty-five patients who were managed postoperatively with an epidural anesthetic and thirty-five patients who were managed with a femoral nerve block. These methods were augmented by an oral pain-management protocol that avoided parenteral narcotics, involved the use of preemptive oral analgesics, and included an intraoperative injection of the pericapsular tissues. The authors found that the average daily pain score after surgery was 4 of 10. Postoperative nausea occurred in eight patients (11%) on the first postoperative day. There were no cases of ileus or urinary retention. The authors emphasized the safety, efficacy, and decrease in narcotic side effects when avoiding parenteral narcotics after total knee arthroplasty. Lavernia et al.21 also reported the results of a multimodal pain-management protocol after total knee arthroplasty. In a retrospective study, 778 procedures in which the patient was managed with traditional pain control were compared with 358 procedures in which the patient received a multimodal pain-management protocol. The pain-management protocol included preemptive treatment with celecoxib, controlled-release oxycodone, acetaminophen, and ondansetron. The patients also received a femoral nerve block and spinal anesthesia. Intraoperatively, the pericapsular tissues were injected with a mixture of Duramorph (morphine sulfate) (Wyeth-Ayerst Laboratories, Philadelphia, Pennsylvania) (10 mg/2 mL), Toradol (ketoralac tromethamine) (Roche Pharmaceuticals, Nutley, New Jersey) (30 mg/3 mL), and bupivacaine (0.25%/10 mL). Postoperatively, pain was treated with oral medications, with the avoidance of parenteral narcotics. The authors reported a significantly decreased rate of knee manipulation in patients receiving the multimodal pain-management protocol (2.24% compared with 4.75%; p = 0.0001). It is clear from a number of studies, including those by Dorr et al.20 and Lavernia et al.21, that multimodal pain management and the avoidance of parenteral narcotics results in improved postoperative pain control and better outcomes without an increase in complications. Wood et al.22, in a prospective randomized study, addressed the use of autologous reinfusion drains after total knee arthroplasty. Eighty patients who underwent a hip or knee replacement were randomized to have removal of a reinfusion drain at six or twenty-four hours after surgery. Autologous blood was only reinfused if >200 mL was collected from the drain at six hours after surgery. The authors monitored the postoperative drop in hemoglobin level, hospital stay, transfusion rates, complications, wound-healing, and rehabilitation in both groups. They found no significant differences between the groups and noted that postoperative hemoglobin levels and transfusion rates appeared to have no association with the timing of reinfusion drain removal. Therefore, early drain removal seems prudent.
There is ongoing controversy about prophylaxis against venous thromboembolism after total knee arthroplasty. In recent years, prophylaxis against venous thromboembolism has become a performance measure that has been used to evaluate hospitals and surgeons, resulting in an increased use of potent anticoagulants after total knee arthroplasty, some of which are associated with a substantial risk of bleeding that must be weighed against the risk of venous thromboembolism and its sequelae. Novicoff et al.23 conducted a retrospective review of their experience with anticoagulation after hip and knee arthroplasty in a hospital in which >500 arthroplasties are performed per year. In response to the American College of Chest Physicians (ACCP) guidelines, their hospital mandated prophylaxis against venous thromboembolism starting in July 2005. Patients undergoing a total knee arthroplasty were given warfarin (with a target international normalized ratio of 2.0) on the night of surgery, and those at high risk of venous thromboembolism were also given 40 mg of a low-molecular-weight heparin starting twelve hours after surgery. All patients having a total hip replacement received both warfarin and low-molecular-weight heparin. In order to comply with the ACCP guidelines, the target international normalized ratio was changed to 2.5 in January 2006. The authors found that the rate of complications, including hematoma, seroma, and hemorrhage, increased from 1.4% before the mandated changes to 9.6% after the mandated prophylaxis was initiated. In addition, the rate of readmission increased from 2.2% to 4.4% after the mandate. The rate of venous thromboembolism remained unchanged throughout the study period. After elimination of the use of the low-molecular-weight heparin, except in high-risk patients, and setting of the target international normalized ratio at or below 2.0, a marked decrease in the rate of complications was once again attained. The use of a multimodal anticoagulation protocol in standard or lower-risk patients was studied by Callaghan et al.24. In that study, 312 consecutive total knee arthroplasties were performed for patients who were considered to have a low risk for venous thromboembolism. Patients were excluded if they had a personal or family history of venous thromboembolism, had a hypercoagulability disorder, had severe venous insufficiency, or were receiving hormonal supplementation. A multimodal approach involving the use of aspirin as the primary mode of chemoprophylaxis was found to be successful, with no deaths for any reason, no readmissions, and no reoperations due to bleeding within ninety days of follow-up. The authors reported that 73% of the patients in the study period had qualified as having a low risk for venous thromboembolism and recommended consideration of this strategy for such patients. These studies illustrate the disparity between agents with regard to the balance between efficacy in preventing venous thromboembolism and safety in minimizing hemorrhagic complications, which is a very important consideration in the decision regarding the selection of thromboprophylaxis. Galat et al.25 retrospectively reviewed the results for forty-two patients (forty-two knees), seen over a twenty-three-year period, who had a reoperation for the evacuation of a hematoma within thirty days after primary total knee arthroplasty. The study was conducted with matched case controls in order to compare potential risk factors and outcomes. In patients who underwent a reoperation for the treatment of a hematoma after total knee arthroplasty, the subsequent two-year probabilities of requiring another major operation (amputation, muscle flap coverage, or implant removal) or having development of a deep infection were 12% and 11%, respectively. In knees that did not have a reoperation because of bleeding, the rates of subsequent major surgery and infection were only 0.6% and 0.8%, respectively. There is clearly a large penalty associated with increasing bleeding rates after total knee arthroplasty. Although the importance of prophylaxis against venous thromboembolism cannot be overstated, there is also a duty to balance benefits with risks. Chelly and Schilling26, in a retrospective study of 3588 patients managed with arthroplasty, assessed the risk of hematoma associated with the use of peripheral nerve blocks when combined with thromboprophylaxis. The blocks included continuous lumbar plexus, continuous femoral, and single sciatic block. A total of 6935 blocks were performed in patients who were managed with warfarin (50.0%), fondaparinux (12.8%), dalteparin (11.6%), enoxaparin (1.8%), or aspirin (23.8%). Perineural catheters were removed on the second or third postoperative day, and no perineural hematomas were identified. The authors concluded that perineural catheters can be inserted before the start of anticoagulation and can be safely removed while the patient is receiving prophylaxis against venous thromboembolism.
A large number of studies that were published in 2008 evaluated the outcomes after total knee arthroplasty. Attar et al.27 retrospectively reviewed the results associated with 354 cemented press-fit condylar total knee replacements after a mean duration of follow-up of 8.8 years (range, 0.3 to 16.9 years). The fifteen patients who were alive at fifteen years after surgery were included in the analysis. Survivorship analysis with revision as the end point revealed an 81.7% survival rate at fifteen years. Revisions were performed because of aseptic loosening (4.5%), infection (2.3%), and polyethylene insert exchange (1.1%). Dalury et al.28 retrospectively reviewed the results associated with 284 consecutive press-fit condylar total knee replacements, with 96% of the knees having cruciate-retaining implants. At a median of approximately seven years, there had been one revision, which had been performed because of a ligament disruption that occurred when the patient fell. At the time of the most recent radiographic follow-up, there were no loose implants and no radiolucent lines measuring >2 mm. The authors found that the press-fit condylar knee had excellent intermediate-term durability. In a prospective series of 219 uncemented hydroxyapatite-coated total knee implants, Chana et al.29 reported an estimated 98.6% survival rate at eight years after surgery. There were only three revisions: two were performed because of deep infection, and one was performed because of tibial tray subsidence. The authors found that any gaps that were visible at the implant-bone interface immediately after surgery had healed within one year. These results appear to match the intermediate-term results of comparable total knee arthroplasties performed with cement. Ong et al.30 conducted an analysis of Medicare claims data in order to search for any associations between the duration of the arthroplasty procedure and the ultimate survival rate. They found that implant survival at eight years after total knee arthroplasty had a significant association with the duration of the index procedure (with use of anesthesia time as a proxy for the duration of the procedure). Total knee arthroplasties with a duration of between 120 and 150 minutes were associated with significantly better implant survival rate than those with a duration of less than ninety minutes or more than 150 minutes. The authors concluded that a longer duration of surgery is associated with a higher complication rate. Several outcome studies have focused on the results of partial revision knee arthroplasty. Berend et al.31 studied the fate of fifty-four total knee replacements in patients who had an isolated revision of a nonmodular tibial component, with retention of the femoral component. Thirty-two of these patients had an all-polyethylene tibial implant, and none had evidence of femoral component loosening. At an average of 6.6 years of follow-up, the survival rate for the revised tibial and retained femoral components was 100%, with aseptic loosening as the end point. Garcia et al.32 studied the results of femoral component retention at the time of revision of a metal-backed patellar component that had caused femoral component scratching. The femoral component was only retained if it was well fixed and well aligned and had only superficial defects without palpable irregularities. Despite the retention of a superficially damaged femoral component, the authors reported a 96% implant survival rate at an average of eighty months of follow-up. Although there is certainly a tendency to move ahead with femoral revision when a surgeon observes damage resulting from a failed metal-backed patellar component, it appears that a more conservative approach of femoral retention may be reasonable when damage to the femoral component is superficial. A number of studies evaluated the results of total knee arthroplasty in specific groups of patients. Rajgopal et al.33 retrospectively reviewed the one-year outcome data for 555 patients managed with total knee arthroplasty who were stratified into categories according to body mass index. Patients were then split into two groups: those classified as having class-III morbid obesity (average body mass index, 46 kg/m2) and those classified as having non-morbid obesity (average body mass index, 30 kg/m2). At the time of the one-year follow-up, overall outcomes were worse for the patients in the morbidly obese group; however, the morbidly obese patients also exhibited a greater improvement in function as compared with the non-morbidly obese patients. It appears that, on the average, patients who are morbidly obese can be expected to have a good outcome after uncomplicated total knee arthroplasty. The year 2008 was marked by debate over whether there are differences between the sexes in terms of the results of total knee arthroplasty. Data have been contradictory with regard to whether outcomes, function, and pain are impacted by the sex of the patient. Lonner et al.34 reported anthropomorphic differences between the distal parts of the femora of men and women. The authors measured the distal parts of the femora of 100 women and 100 men at the time of total knee arthroplasty and found that the aspect ratio (anteroposterior dimension/mediolateral dimension), a measure of femoral shape, was a mean of 0.84 (range, 0.57 to 1.03) in women as compared with 0.81 (range, 0.66 to 1.34) in men, with variability being noted both within and between the sexes. Singh et al.35 investigated the impact of sex and age on the prevalence of moderate or severe pain after primary or revision total knee arthroplasty. The authors studied 5290 and 2602 patients who responded to a query at two and five years after primary total knee arthroplasty, respectively, and another 1109 and 505 patients who responded at two and five years after revision total knee arthroplasty, respectively. They found that the prevalence of moderate to severe pain was higher in women than men at two and five years after primary total knee arthroplasty (9% compared with 6.6% and 7.9% compared with 6.5%, respectively) and also at two and five years after revision total knee arthroplasty (28.6% compared with 22% and 28.9% compared with 18.3%, respectively). After adjustment for age and preoperative pain severity, more women than men had moderate to severe pain at two years after primary total knee arthroplasty (p = 0.04) but not at five years after primary total knee arthroplasty (p = 0.42). MacDonald et al.36 reported on a consecutive cohort of 3100 women and 2179 men who were followed for a minimum of two years after primary total knee arthroplasty. Although men had greater improvement than women did in terms of the Knee Society function and total scores (p < 0.0001), there were no differences between the sexes in terms of the physical component of the SF-12 (Short Form-12) score and women had greater improvement than men did in terms of the WOMAC (Western Ontario and McMaster Universities) domains of pain (p = 0.008), joint stiffness (p = 0.019), and function (p < 0.0001). Ritter et al.37 retrospectively reviewed the results of 7326 cruciate-retaining total knee arthroplasties over a seventeen-year period, examining outcome and survival in association with the sex of the patient. Preoperative clinical scores for all parameters were lower for female patients. Postoperatively, female patients had greater improvement in terms of the Knee Society score and flexion. Improvements in terms of walking ability and pain were equal between the sexes. Male patients had greater improvements in terms of stair-climbing and the function score. The rate of implant survival was 98% for both sexes at fifteen years. Quality of life and functional outcomes after total knee arthroplasty are of great importance to both patients and surgeons, and questions regarding these subjects formed the basis of several studies in 2008. Mockford et al.38 conducted a randomized prospective study of 150 patients to determine the effect of outpatient postoperative physical therapy on range of motion after total knee arthroplasty. Patients in one group received no outpatient physical therapy after total knee arthroplasty, whereas patients in the study group received six weeks of directed outpatient therapy. At one year, the group that had received physical therapy had a trend toward better motion; however, there were no significant differences between the groups in terms of knee scores or range of motion. Mahomed et al.39, in another study addressing physical therapy, reported on 234 patients who were randomized to receive either inpatient rehabilitation or home-based rehabilitation after hip or knee arthroplasty. Patients who received inpatient rehabilitation had a mean stay of eighteen days at a rehabilitation facility, whereas patients who received home-based physical therapy received eight visits. At twelve months after the arthroplasty, there were no significant differences between the groups with regard to complications, clinical improvement, or functional outcome scores. With regard to cost, it appears that home-based postoperative programs are better than inpatient rehabilitation, without any sacrifice in terms of outcome after joint arthroplasty. Range of motion after total knee arthroplasty continues to interest surgeons attempting to improve long-term function. Chaudhary et al.40 performed a prospective randomized study of 100 total knee arthroplasties in which the range of motion of knees with posterior cruciate ligament-substituting and posterior cruciate ligament-retaining designs were compared for as long as two years after surgery. Patients were evaluated at standardized time intervals for two years with regard to range of motion and various self-reported and measured scores. At two years, there were no significant differences between the groups. Both designs were associated with excellent two-year results. Both groups had also achieved their eventual range of motion in a similar time period after surgery. Ritter et al.41 examined the importance of range of motion to function after cruciate-retaining total knee arthroplasty. A retrospective review of 5556 primary total knee arthroplasties revealed optimum functional scores, pain scores, and Knee Society scores in patients with 128° to 132° of motion. Patients with >133° of motion had the best stair-climbing scores, and patients with <118° of motion were substantially compromised. A postoperative flexion contracture and hyperextension of >10° were also associated with poor outcomes. Patient-reported activities often reveal noncompliant behaviors after total knee arthroplasty. Although surgeons generally recommend avoiding heavy manual labor and high-impact sports, there are few data regarding the influence of these activities on outcomes after total knee arthroplasty. Dahm et al.42 surveyed 1206 patients who had an unrevised primary total knee replacement with regard to clinical outcome, activity level, and participation in high-level activities. The average age at the time of total knee arthroplasty was sixty-seven years, and the mean duration of follow-up for the patients who were surveyed was 5.7 years. Although patients who were more than seventy years of age had lower Knee Society scores than average, they exhibited a higher self-assessment of activities in comparison with their peers. Men had higher self-assessment scores in comparison with their peers and had higher function scores and University of California at Los Angeles scores than female patients did. Overall, 16% of the patients reported being involved in heavy manual labor or sports that are not recommended after arthroplasty. Mont et al.43 reported on thirty-one patients who had been managed with total knee arthroplasty and who participated in high-impact sports, including jogging, singles tennis, racquetball, squash, and basketball, an average of four times per week. After an average duration of follow-up of four years, thirty-two of thirty-three knees had a successful clinical and radiographic outcome. It is clear from these studies that patients with a total knee arthroplasty often participate in activities that are considered to be risky by surgeons. At least in the short term, doing so does not appear to affect the success of total knee arthroplasty.
Understanding the prevalence and causes of complications after total knee arthroplasty is critical for developing diagnostic tools and treatment algorithms. Pulido et al.44 presented their prospective data on in-hospital complications after hip and knee arthroplasty. From a database of 15,383 total joint arthroplasties, they identified a 0.16% in-hospital mortality rate. Systemic complications included 152 pulmonary emboli, ninety-two tachyarrhythmias, and thirty-six myocardial infarctions. Joint-related morbidities included twenty-nine peripheral nerve injuries, twenty-five periprosthetic fractures, eighteen dislocations, and sixteen vascular injuries. Parvizi et al.45 identified a 0.1% rate of vascular injury among 13,517 patients who were managed with total joint arthroplasty. While the vascular injuries in eleven patients who were managed with total knee arthroplasty usually resulted from indirect injury, the vascular injuries in five patients who were managed with total hip arthroplasty more likely resulted from a direct injury to the vessels. Parvizi et al.46 also identified a 0.7% rate of postoperative ileus among 4567 patients who had undergone joint arthroplasty with regional anesthesia and multimodal pain management. Patients who were at risk for postoperative ileus were older, male, and had a history of abdominal surgery. In that study, narcotic type and dosage appeared to be unrelated to the occurrence of postoperative ileus. Austin et al.47 conducted a prospective study of 1971 patients in which they examined the prevalence and causes of hypoxemia after total joint arthroplasty. An acute episode of hypoxemia occurred in seventy-eight patients (4%) during hospitalization. Hypoxemia was the initial sign in 32% of these patients and predicted major complications such as pulmonary embolism, pulmonary edema, and pneumonia. It is clear that acute episodes of hypoxemia after joint arthroplasty should be regarded as a sign of a serious complication and should be treated appropriately. Bolognesi et al.48 examined the Nationwide Inpatient Sample and found that 8.55% of 751,340 patients who were managed with a total knee arthroplasty or total hip arthroplasty had diabetes. This group of patients had fewer routine discharges and required the utilization of more resources in comparison with the nondiabetic patients. It was also found that patients with diabetes had a higher likelihood of perioperative stroke or pneumonia as well as a higher likelihood of requiring transfusion. This study is one of several recent studies that have identified the increased resource utilization and complication rate among patients with diabetes who are managed with arthroplasty. Several studies have focused on the epidemiology, diagnosis, and treatment of infection after total knee arthroplasty. Kurtz et al.49 used the Nationwide Inpatient Sample to study periprosthetic infections. The authors identified a greater infection rate after total knee arthroplasty than after total hip arthroplasty (0.92% compared with 0.88%). The rate of infection was lower at rural and urban teaching hospitals than it was at urban nonteaching hospitals. In addition, the hospital stay for patients with an infection at the site of an arthroplasty was approximately double that for patients without an infection. Ghanem et al.50, in a multicenter study, analyzed the synovial fluid, C-reactive protein level, and erythrocyte sedimentation rate for 429 knees that had had a revision arthroplasty and identified patients who had a diagnosis of infection. The authors identified the optimum diagnostic cutoff values for infection as a synovial fluid leukocyte count of >1100 cells per cubic millimeter (1.1 x 109/L), a neutrophil percentage of >64%, a C-reactive protein level of >10 mg/L (>1 mg/dL), and an erythrocyte sedimentation rate of >30 mm/hr. The combination of a synovial fluid leukocyte count and neutrophil percentage below the cutoff values had a negative predictive value of 98.2%. When the results of these tests were both above the cutoff values, 98.6% of the cases were infected. Similarly, when the neutrophil percentage and C-reactive protein level were below the cutoff values, infection was extremely rare. In an effort to advance the field of molecular diagnostics, Birmingham et al.51 reported on their success with the use of real-time reverse transcription polymerase chain reaction to detect viable bacteria. Because bacterial mRNA is broken down more quickly after death than DNA is, the detection of mRNA is more likely to be specific for live bacteria. The authors found that while their mRNA detection method was able to identify both culturable and unculturable bacteria in an in vitro model of septic arthritis, it also minimized the false-positive results associated with traditional polymerase chain reaction. This technology offers a very exciting new diagnostic tool for the identification of infection at the site of a joint arthroplasty. Oussedik and Haddad52, in a study of fourteen patients, reported on the success of oral linezolid along with a one or two-stage revision for the treatment of infection at the site of joint arthroplasty. They found that although linezolid was given orally, it resulted in the eradication of infection when combined with appropriate surgical intervention. Although that was a small study with an average thirty-two-month follow-up, it appears that oral linezolid is a reasonable option when faced with drug-resistant strains of bacteria at periprosthetic sites. The development of stiffness after total knee arthroplasty limits function and predisposes to pain. Some believe that there is a genetic predisposition to abundant scar formation after surgery that causes certain patients to have a stiff knee. Others believe that pain after total knee arthroplasty may restrict the motion that is necessary to prevent scar formation. It is also held by some that the wrong combination of component positioning can lead to pathologic kinematics and stiffness after total knee arthroplasty. Two interesting reports shed light on this topic. Pereira et al.53 studied the kinematics of ten total knee replacements with <90° of flexion and compared them with those of eleven total knee replacements with >110° of flexion with use of optical calibration with shape-matching techniques. The authors found no significant differences between the two groups and could not identify a pathologic kinematic characteristic in the knees that were stiff. They concluded that pathologic kinematics are not the underlying cause of stiffness after total knee arthroplasty in the setting of well-positioned components. Lang et al.54 retrospectively studied the preoperative and postoperative ranges of motion of a second total knee arthroplasty in patients who had a first total knee arthroplasty that was complicated by stiffness. Subjects were identified from a database of patients with a history of manipulation or revision after total knee arthroplasty who had a range of motion of <85° after the index procedure. Fifteen patients who went on to have a contralateral total knee arthroplasty were identified, and they were compared with an age-matched control group of 109 patients. Although range of motion was not significantly different at the time of the two-year follow-up, the rate of manipulation was 26% in the study group, compared with 2.8% in the control group. This study shows that good results can be attained in a patient with stiffness at the site of a previous contralateral total knee arthroplasty; however, there is a clear predisposition for stiffness and the need for manipulation in these patients. It is possible that genetic characteristics affecting scar formation55 or the pain response21 are responsible for this effect.
The editorial staff of The Journal reviewed a large number of recently published research studies related to the musculoskeletal system that received a Level-of-Evidence grade of I. Over 100 medical journals were reviewed to identify these articles, all of which have high-quality study design. In addition to articles already cited in this update, three additional level-I articles were identified that were relevant to this specific review. A list of those articles is appended to this review following the standard bibliography. We have provided a brief commentary about each of the articles to help guide your further reading, in an evidence-based fashion, in this subspecialty area.
Wylde V, Learmonth I, Potter A, Bettinson K, Lingard E. Patient-reported outcomes after fixed- versus mobile-bearing total knee replacement: a multi-centre randomised controlled trial using the Kinemax total knee replacement. J Bone Joint Surg Br. 2008;90:1172-9. Erratum in: J Bone Joint Surg Br. 2008;90:1534. This multicenter randomized controlled study of 250 knees from four centers compared the two-year outcomes of mobile-bearing and fixed-bearing total knee arthroplasties. Patients were evaluated at intervals of eight weeks, twelve weeks, one year, and two years after the index procedure with regard to a variety of measures, including mental health scores, knee outcome scores, quality-of-life scores, and a validated scale of postoperative satisfaction. The patients had a mean age of sixty-eight years, and 55% of the patients were female. There were no significant differences at any time interval between patients with mobile and fixed-bearing knees. This large study suggests that, at least in the short term, there is no observable difference in outcomes between mobile and fixed-bearing knees. We await the longer-term results for these two patient groups. Amin A, Watson A, Mangwani J, Nawabi D, Ahluwalia R, Loeffler M. A prospective randomised controlled trial of autologous retransfusion in total knee replacement. J Bone Joint Surg Br. 2008;90:451-4. The authors conducted a prospective randomized controlled trial to investigate the efficacy of autologous blood retransfusion after total knee arthroplasty. Ninety-two patients who received an autologous retransfusion after surgery were compared with eighty-six patients who were managed with a standard vacuum drain. Hemoglobin levels were measured at twenty-four, forty-eight, and seventy-two hours postoperatively, and the need for allogeneic blood transfusion was monitored. The clinical trigger for transfusion was based on hemoglobin levels and clinical symptoms. The authors found no significant difference in mean hemoglobin levels after surgery and found no difference in the need for allogeneic transfusion after total knee arthroplasty. On the basis of this study, it appears that the retransfusion of drainage blood after total knee arthroplasty does not augment the hemoglobin level or prevent allogeneic transfusion. The technique of autologous retransfusion may be more useful in the setting of revision joint arthroplasty, when larger volumes of blood may be retransfused. Karachalios T, Giotikas D, Roidis N, Poultsides L, Bargiotas K, Malizos KN. Total knee replacement performed with either a mini-midvastus or a standard approach: a prospective randomised clinical and radiographic trial. J Bone Joint Surg Br. 2008;90:584-91. The difference between standard and minimally invasive approaches to total knee arthroplasty has been the subject of many studies. This prospective randomized study compared the early results of a standard total knee arthroplasty technique with those of a midvastus technique. Over a three-year period, 100 patients were randomized to one of the two procedures and were followed clinically and radiographically for an average of twenty-three months. The patients who were randomized to the midvastus approach demonstrated significantly better mean functional scores, mean Oxford knee scores, and mean total scores for nine months after the index procedure. However, the authors also noted that more patients who were randomized to the midvastus approach had a malpositioned component. These results generally agree with those of most studies that have compared minimally invasive and standard approaches to total knee arthroplasty. Although the early recovery after total knee arthroplasty appears to be improved for about three to nine months in patients who are managed with a midvastus approach, there may be a simultaneous increase in the overall number of malpositioned implants.
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