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© 2001 The Journal of Bone and Joint Surgery, Inc.
What’s New in Adult Reconstructive Knee Surgery
Michael J. Archibeck, MD The purpose of this update on adult reconstructive knee surgery is to discuss, in summary fashion, topics presented at selected orthopaedic meetings and in articles published in the American volume of The Journal of Bone and Joint Surgery and the Journal of Arthroplasty during the year 2000. Presentations mentioned in this article include those given at the annual meeting of the American Academy of Orthopaedic Surgeons and on Specialty Day at the meeting of the Knee Society, both held in Orlando, Florida, in March 2000; at the Interim Meeting of the Knee Society, held in Boston, Massachusetts, in September 2000; and at the annual meeting of the American Association of Hip and Knee Surgeons, held in Dallas, Texas, in November 2000. Nonoperative Treatment of Arthritis Nonoperative modalities, including nonsteroidal anti-inflammatory medications, intra-articular injections of steroids, viscosupplementation, physical therapy, nutritional supplements, weight loss, and the use of assistive devices, remain the mainstays of the initial treatment of patients with mild-to-moderate osteoarthritis of the knee. A meta-analysis of the effectiveness of glucosamine and chondroitin in patients with osteoarthritis, which was originally published in the Journal of the American Medical Association, was recently reviewed in the Evidence-Based Orthopaedics section of the American volume of The Journal of Bone and Joint Surgery (2000;82:1323). Both glucosamine and chondroitin were found to be effective for improving outcomes as measured with the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), the Lequesne Index, and global pain and mobility scores and as indicated by the need for medication. However, the magnitude of this improvement was unclear because of inconsistencies in the study designs. In another article, which originally was published in the Annals of Internal Medicine and was subsequently reviewed in The Journal’s Evidence-Based Orthopaedics section (2000;82:1324), manual physical therapy and exercise were found to decrease both pain and stiffness, as measured with the WOMAC scores, in the knees of patients with osteoarthritis. High Tibial Osteotomy Given the encouraging results of modern total knee replacements, the role of osteotomy about the knee for the treatment of osteoarthritis remains controversial. Billings et al. reported the long-term results of high tibial osteotomy, performed with use of a calibrated osteotomy guide and rigid internal fixation and followed by early motion, in fifty-six patients (sixty-four knees) who had varus gonarthrosis1. With conversion to knee replacement as the end point, the expected rate of survival was 85% at five years and 53% at ten years, indicating that osteotomy can be an effective alternative for young patients who have the appropriate indications. The issue of total knee arthroplasty following high tibial osteotomy was addressed in two papers. Meding et al. compared the results of bilateral total knee replacement in patients who had had a prior high tibial osteotomy on one side and found that the previous procedure had no adverse effect on the outcome of the subsequent knee replacement2. Haddad et al. found a twenty-three-minute increase in the operative time, slightly less flexion (8°), and more frequent patellar subluxation in patients who had had a knee replacement following a high tibial osteotomy; however, no significant differences in the Knee Society score, the Hospital for Special Surgery score, or the revision rate were noted. Unicompartmental Knee Arthroplasty The recent introduction of minimally invasive techniques has led to renewed interest in unicompartmental knee replacement. While the clinical results have improved dramatically with use of refined indications, modern instrumentation, improved implant designs, and a better understanding of the importance of avoiding overcorrection, very little new information about clinical outcome or implant survival was reported in the last year. Lindstrand, in a multicenter study emphasizing the important role of surgical technique in unicompartmental knee replacement, reported wide variability in the prevalence of early failure due to subsidence, loosening, and fracture. Argenson et al. performed videofluoroscopy in patients who had had a unicompartmental knee arthroplasty and found kinematic patterns that were more similar to those in patients who had had a total knee arthroplasty than to those in patients who had a normal knee. Posterior contact in full extension and paradoxical anterior femoral translation were common, suggesting inconsistent function of the anterior cruciate ligament following unicompartmental knee arthroplasty. Revision following failed unicompartmental knee arthroplasty was described in two papers. Bohm and Landsiedl, in a review of thirty-five such revisions, found that the most common mode of failure, in knees with a variety of unicompartmental prosthetic designs, was aseptic loosening followed by polyethylene wear. Sixty-six percent of the revisions were performed within the first five years after the index procedure. At four years after the revision, 69% of the knees had a good or excellent result. Engh and McAuley found the predominant mechanism of failure of unicompartmental knee replacement to be polyethylene wear, followed by loosening. They were encouraged by the simplicity of unicompartmental revision. No allograft was used in any knee. A primary femoral component was used in all of the thirty-nine knees, and 64% (twenty-five) of these components were cruciate-retaining devices. A stemmed tibial component was inserted in 36% (fourteen) of the knees and a wedged tibial component, in 21% (eight). Hanssen et al., reporting on surgical options for middle-aged patients with osteoarthritis of the knee, found the results of unicompartmental knee replacement in appropriately selected patients to be comparable with those of total knee arthroplasty in the first ten years after surgery. They emphasized that slight undercorrection and an adequate thickness of the polyethylene were important for ensuring a successful outcome. Blood Conservation in Total Knee Arthroplasty While many algorithms for blood conservation have been proposed, the methods vary widely from institution to institution. Hatzidakis et al. found a 50% rate of wastage in the autologous blood-donation protocol used at their institution. They also noted a 0% rate of allogeneic transfusion in patients undergoing primary joint replacement who had had an initial hemoglobin level of at least 15.0 g/L. The same was true for patients who were less than sixty-five years of age and had had an initial hemoglobin level of 13.0 to 15.0 g/L. Hatzidakis et al. recommended decreasing the rate of autologous donation by informing these patients of the low likelihood that an allogeneic transfusion would be needed. Nazarian et al. compared the use of preoperative autologous blood donation (fifty-seven patients), recombinant erythropoietin (fifty patients), and normovolemic hemodilution (forty-three patients) and reported allogeneic transfusion rates of 28%, 23%, and 19%, respectively. Each of these measures reduced the need for allogeneic transfusion without creating a substantial difference in cardiovascular complications. Cushner et al. prospectively studied the use of human recombinant erythropoietin (epoetin alfa) in patients having a two-stage exchange because of infection at the site of a total knee arthroplasty. The mean number of units of allogeneic blood required following reimplantation was significantly lower in the erythropoietin-treated group than in an untreated (control) group (0.6 compared with 1.8 units per patient; p < 0.001). Alignment of the Femoral and Tibial Components in Total Knee Arthroplasty Advances in our understanding of the proper rotational alignment of the femoral and tibial components have reduced the prevalence of patellofemoral complications. Miura et al. studied the transepicondylar axis in normal, varus, and valgus knees. They found no hypoplasia of the posterior aspect of the medial condyle in varus knees, but there was substantial distortion of the posterior aspect of the lateral condyle in valgus knees. Olcott and Scott compared four intraoperative methods of determining femoral component rotation during primary knee arthroplasty. They found that use of the transepicondylar line was the most accurate technique and that use of 3° of external rotation from the posterior aspect of the condyles was the least accurate, especially in valgus knees. Using computed tomographic scanning of total knee prostheses, Barrack found that relative internal rotation of the femoral and/or tibial component was significantly associated with anterior knee pain (p < 0.01). Hanssen and Pagnano found that at least 4° of preoperative varus obliquity of the proximal part of the tibia was associated with a higher posterior condylar angle. They recommended use of the transepicondylar axis or the anteroposterior axis (but not the posterior parts of the condyles) in varus knees to avoid malrotation of the femoral component. Fehring found that the classic flexion-extension gap technique was more accurate in producing a rectangular flexion gap than was the use of osseous landmarks. When osseous landmarks were used, rotational errors of at least 3° occurred in 45% of patients. This finding may have implications regarding polyethylene wear, range of motion, and long-term clinical results. Kaper et al. reported improved patellar tracking and a reduced rate of lateral retinacular release in association with the use of a prosthesis with 3° of built-in external rotation. With regard to femoral rotational alignment, there appears to be a trend away from using the posterior aspect of the condyles and toward using the epicondylar or anteroposterior axis. Perillo-Marcone used finite-element analysis to determine the effect of tibial component positioning on cancellous bone stresses and found that positioning the tibial component in valgus resulted in the lowest stresses and the lowest risk of cancellous bone failure. Increased posterior slope produced a marginal (9%) increase in the risk of cancellous bone failure. Bai et al. demonstrated, with use of a sawbones model, that increasing amounts of posterior slope decreased anterior compressive strains and increased posterior compressive strains. A posterior slope of 0° to 3° provided the greatest stability of the tibial component. Technical Issues in Primary Total Knee Arthroplasty Techniques of soft-tissue balancing were addressed in three studies. Whiteside evaluated the function of the anterior and posterior oblique portions of the medial collateral ligament and the posterior capsule in flexion and extension in cadaveric knees. He found that release of the posterior oblique portion of the medial collateral ligament and the posterior capsule produced laxity in extension. Release of the anterior portion of the medial collateral ligament produced laxity in higher degrees of flexion (60° to 90°). Griffin et al. examined the accuracy of soft-tissue balancing in total knee replacement and found that they were able to obtain rectangular flexion and extension gaps in more than 80% of knees. Equality of the flexion and extension gaps was more difficult to achieve, with only 50% being within 1 mm of each other. Milhalko and Krackow, in a cadaveric study, evaluated the use of so-called pie-crusting of posterolateral structures for the treatment of valgus deformity and found that the correction obtained with this technique occurs through effective release of the lateral collateral ligament. Those authors cautioned that the peroneal nerve may be within 16 mm of these structures and therefore may be at risk during the procedure. Fixation techniques were addressed in several studies. Berger et al. reported the results of 113 cementless total knee arthroplasties after eleven years of follow-up. They found that cementless fixation was very successful for the femoral component but that it led to a 30% rate of revision of the metal-backed patellar component and to a 6% rate of revision of the tibial component, with a substantial amount of tibial radiolucencies and osteolysis. As a result of these findings, Berger et al. abandoned the use of cementless fixation. Norton and Eyres, in a report on a new bone-preparation technique that included bone suction and pressure-lavage irrigation, noted improved cement penetration as seen on plain radiographs. Li found no relationship between preoperative bone-mineral density and subsidence, lift-off, or maximum migration, indicating that bone cement can compensate for variations in bone quality in the early follow-up period. Mahoney et al., in a series of 102 bilateral total knee replacements, one-half of which included implantation of an uncemented keel, reported a 6% revision rate on the side with the uncemented keel compared with no revisions on the side with the cemented keel. On the basis of this finding, Mahoney et al. recommended cementing the keel and plateau of the tibial component. Clinical Results of Primary Total Knee Arthroplasty The role of the posterior cruciate ligament in knee replacement remains controversial. The results of several long-term studies on cruciate-retaining prosthetic designs were presented or published last year. Berry et al. reported on 1000 consecutive cemented cruciate-retaining knee prostheses that had the same modern design3. At a mean follow-up of ten years, the rate of survival was 97.3% with revision of any component as the end point and 98.8% with aseptic loosening as the end point. Emerson et al. reported the eleven-year results of another "flat on flat" cruciate-retaining design and found a 95% rate of survival with any revision as the end point. They noted no osteolysis, femoral or tibial loosening, or failure of the compression-molded polyethylene insert. Ritter reported on 4581 knees that had a prosthesis with the same design and found a survival rate of more than 98% at fifteen years. Buehler reported on the press-fit condylar total knee system, which has a cruciate-retaining design and is implanted using cement. At a mean of nine years, there was a 98.7% rate of survival with aseptic loosening as the end point and the mean Knee Society score was 96 points. Berger studied the eight to fourteen-year results for 172 cemented cruciate-retaining prostheses that had a pegged tibial component and found no aseptic loosening of the tibial or femoral component and no osteolysis. The most common source of failure was the metal-backed patellar component, which accounted for 64% of the reoperations in this series. One of us (M.J.A.) reported excellent clinical and radiographic results, with a low (2%) rate of late posterior instability, for seventy-two cruciate-retaining total knee prostheses in patients with rheumatoid arthritis. Whiteside, in a cadaveric model, found that varus knees that had undergone a cruciate-substituting arthroplasty were susceptible to valgus and rotational instability in flexion. This finding suggests that the posterior cruciate ligament acts as a secondary stabilizer to varus and valgus stresses. Lombardi et al. described an algorithmic approach to posterior-cruciate-ligament retention in which the status of the ligament and the extent of the deformity are used to decide whether a cruciate-retaining or a posterior stabilized design should be employed. The posterior cruciate ligament was retained in 63% of the 213 knees and a cruciate-substituting replacement was performed in the remainder, with excellent results in both groups. Clark reported on a randomized, controlled, multicenter clinical trial in which the outcomes of posterior stabilized knee replacement were compared with those of posterior-cruciate-retaining knee replacement. Two years postoperatively, there was no significant difference between the groups on the basis of the Knee Society total clinical rating score, the range of motion, or the scores on the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the Short Form-12. The results of several studies comparing cruciate-sacrificing with cruciate-substituting designs have been reported. Thadani et al. received the Insall Award for their ten to twelve-year review of 100 knees treated with the Insall-Burstein-I total knee prosthesis. They found a 1% prevalence of loosening of the tibial component, a 7% prevalence of patellar fracture, and no aseptic loosening of the femoral component. No clinically important polyethylene wear was identified in association with this nonmodular, molded tibial component. Laskin et al., in a randomized, prospective study comparing a cruciate-substituting with a cruciate-sacrificing (deep-dish tibial component) design, found no difference in range of motion, ability to ascend or descend stairs, Knee Society scores, stability, or anterior knee pain. Hofmann compared the use of a cruciate-sacrificing ultracongruent polyethylene insert with that of a cruciate-retaining design and found similar clinical results; however, the knees with the ultracongruent insert had decreased anteroposterior instability. Rodriguez reported a 6% rate of revision and no substantial osteolysis after a twenty-year follow-up of 164 patients with 220 total condylar knee prostheses. There was a 2% rate of aseptic loosening for both the tibial and the femoral component. Ranawat, in a study of 243 knees, compared metal-backed tibial components with all-polyethylene tibial components; both types of components had a cruciate-substituting design. At seven years, there was a higher rate of osteolysis in the group with metal-backed components (8% compared with 0%) and a higher rate of survival in the group with the all-polyethylene components (96% compared with 75%). Ranawat’s findings call into question the superiority of metal-backed tibial components. Kinematic studies of cruciate-retaining and cruciate-substituting designs have demonstrated that both designs have abnormal kinematics, with paradoxical anterior translation in flexion and posterior contact in extension; these findings are consistent with an anterior-cruciate-ligament-deficient knee. Stiehl et al., using fluoroscopic analysis, found that cruciate-retaining designs had a more abnormal kinematic performance than bicruciate-sparing designs. Siliski, using gait analysis, found a minimal difference between knees that had a cruciate-retaining prosthesis and those that had a cruciate-substituting implant. Total knee replacement in younger patients was addressed in two studies. Taylor et al. reviewed the minimum five-year results for fifty-two patients (seventy-one knees) who were less than fifty years old. The ten-year survival rate was 78% with any revision as the end point, and the mean Knee Society score was 84 points. These results are clearly inferior to those in more elderly patients. Lonner et al. reported a 12.5% rate of aseptic failure at eight years in a study of thirty-two patients who were forty years old or less. Both groups of investigators recommended that knee replacement be used with caution in younger, more active patients. The Mobile-Bearing Knee Prosthesis Interest in total knee arthroplasty with use of mobile-bearing prostheses has continued, as these designs provide increased conformity of the polyethylene while allowing for rotational and/or anterior and posterior movement of the articulating surface. Callaghan et al., after nine to twelve years of follow-up, reported that the clinical and radiographic results associated with cemented mobile-bearing knee prostheses were comparable with those associated with fixed-bearing prostheses, with no aseptic loosening or osteolysis4. Jordan, in a study of 256 knees (232 patients), reported a 95% rate of survival of a cruciate-retaining cementless meniscal-bearing knee design at twelve years, with no aseptic loosening. D’Lima studied the kinematics of fixed and mobile-bearing knee implants in a cadaveric model and found no substantial differences. The Difficult Primary Total Knee Arthroplasty Lonner et al. reported that simultaneous femoral osteotomy and total knee arthroplasty, while difficult to perform, was effective for the treatment of osteoarthritis associated with severe extra-articular deformity. They recommended the use of a plate, a locked intramedullary nail, or a long-stemmed femoral component for fixation. Nazarian used similar techniques (osteotomy and insertion of a press-fit stem) for the treatment of fifteen tibial and femoral deformities and achieved excellent clinical results and a 100% rate of union. Parvizi reported the results of total knee arthroplasty following a prior fracture of the distal part of the femur. He found that, despite substantial improvements in function, these patients are at increased risk for perioperative complications and substandard outcomes. Easley et al. reported excellent clinical results and a high rate of survival, at a mean of 7.8 years, in a study of forty-four primary constrained total condylar knee prostheses in elderly patients with valgus arthritic knees. These implants had a tibial post, which provides stability against varus and valgus stresses. Meding examined recurvatum of the knee (range, 5° to 20°) in a study of fifty-six patients (sixty knees) managed with a cruciate-retaining implant and found that only two knees (3.3%) had a hyperextension deformity postoperatively. Trousdale reported on nineteen patients who were managed with a gastrocnemius flap because of problems related to wound-healing at the site of a total knee prosthesis; only seven patients had an uneventful course following flap coverage. While this technique remains a viable option in these difficult cases, the complication rate is high. Kim et al. reported the results of arthroplasty following spontaneous osseous ankylosis (sixteen knees) or formal arthrodesis (fourteen knees); despite improvements in function, there were relatively high rates of wound complications (53%) and infection (7%). Infection in Association with Total Knee Arthroplasty The diagnosis of infection in a patient who has had a total knee arthroplasty can be difficult to make. Two studies focused on the use of white blood-cell counts to facilitate diagnosis. Mason et al. found the synovial cell count differential analysis to be a statistically relevant indicator of the presence of infection (p < 0.001)5. A synovial aspirate with a white blood-cell count of at least 25,000 cells/mm3 and at least 60% polymorphonuclear cells was determined to be highly suggestive of infection (specificity, 95; sensitivity, 98%)5. Similarly, Kersey found that, in osteoarthritic patients with a total knee replacement, a synovial white blood-cell count of <2000 cells/mm3 and a differential of <50% polymorphonuclear cells had a 98% predictive value for the absence of infection. The role of indium scans in the diagnosis of infection at the site of a total joint arthroplasty has remained limited. Scher et al. found that indium scans had a sensitivity of 77%, a specificity of 86%, positive and negative predictive values of 54% and 95%, and an accuracy of 84% for the prediction of infection. The treatment of infection after total knee arthroplasty was addressed in four studies. Waldman et al., in a study on the role of arthroscopic irrigation and débridement in the treatment of acute postoperative and acute late hematogenous infections, found this method to be successful in only six of sixteen patients and therefore recommended open treatment. Fehring et al. received the Ranawat Award for their report on articulating compared with static spacers in two-stage revision for sepsis6. They found a similar rate of recurrent sepsis and range of motion, less bone loss, and a reduced operative time in the patients who had been treated with an articulating spacer. In a similar study, Emerson found an increased range of motion (108° compared with 94°) and a slightly lower rate of reinfection (7.6% compared with 9%) when comparing the use of twenty-two articulating spacers with the use of twenty-six static spacer blocks. Nazarian reviewed the results of two-stage reimplantation with use of a static spacer and found a 10% rate of reinfection and a 90% rate of good and excellent results following the second stage; these findings confirm the high clinical success rate associated with this more traditional method. Mont et al., in a study on the role of preoperative aspiration of the joint and culture of the specimen before second-stage reimplantation, found that this method was useful for identifying patients who had recurrent infection and that it led to improved clinical outcomes7. Patients with positive cultures were treated with repeat two-stage revision, with a high success rate. Barrack et al. compared the outcomes of revision in patients who did and did not have an infection and found that the Knee Society scores, range of motion, and ability to return to normal activities were significantly worse in the group that had had revision for infection (p < 0.05 for all). However, patients in both groups expressed an equal degree of satisfaction with the results. Issues Related to the Patellofemoral Articulation The patellofemoral articulation has been reported to be the most common source of complications in total knee arthroplasty, and a large amount of data were presented on this topic last year. Mont et al. reported a good or excellent result following 96% (twenty-three) of twenty-four total knee arthroplasties in patients with isolated patellofemoral osteoarthritis who were followed for a mean of seven years. Stuart et al., in a study of thirty-one knees in twenty-four patients with isolated patellofemoral osteoarthritis, reported very good clinical results as indicated by Knee Society scores but found that a high rate of lateral release (67%) was required at the time of primary knee replacement. They also noted persistent anterior pain in 19% of the knees. Patellar resurfacing was addressed by Barrack et al. in a prospective, randomized study. No significant difference was detected between patients who had had patellar resurfacing and those who had not, with regard to anterior knee pain or Knee Society scores. Patients who had a bilateral total knee replacement with resurfacing of the patella in one knee and retention of the patella in the other expressed no preference for either knee. However, there was a high rate of subsequent resurfacing of previously nonresurfaced patellae, with all but one patient having a substantial decrease in symptoms. Kulkarni et al. found no difference in revision rates between resurfaced and nonresurfaced patellae at ten years and suggested that the trochlear design of the prosthesis rather than patellar resurfacing is the main determinant of the patellofemoral outcome. Laskin, in a report on 178 patients treated with use of modern total knee instrumentation and avoidance of patellofemoral overstuffing, found a low rate of lateral release (7%; twelve knees), with excellent clinical and radiographic results. The design of the patellar component was addressed in a number of studies. Ranawat found no difference between the short-term results associated with an oval three-peg patellar component and those associated with a dome-shaped single-peg patellar component. Jordan, in a study of 232 patients (256 knees) managed with the Low Contact Stress knee prosthesis, reported a 99% rate of survival of themetal-backed rotating anatomic patellar component at twelve years. Goldberg et al. reviewed the results for 261 metal-backed cementless patellar components and reported a marked reduction in the failure of the modified dome-shaped Miller-Galante-II design, which had a 96% rate of survival at nine years. These findings highlighted the importance of design in the survival of metal-backed components. Berry et al., in a review of the Mayo Clinic experience with seventy-eight patellar fractures after total knee arthroplasty, reported a 39% rate of complications following operative intervention, with 26% of the knees requiring reoperation. They recommended nonoperative treatment of patellar fractures in knees with an intact extensor mechanism and a stable implant. Keating et al. reviewed 177 patellar fractures in 135 patients and reported a high rate of complications (a 100% rate of nonunion and a 50% rate of infection) following operative treatment of patellar fractures in patients who had had a total knee replacement and recommended that most of these fractures should be treated nonoperatively8. Wulff and Incavo, in a cadaveric study in which patellar surface strain was measured as a predictor of patellar fracture, found inset patellar components and thicker patellar components (the latter of which are used in patients with a thinner patellar remnant) to be detrimental. Polyethylene Wear Polyethylene wear after total knee replacement remains a topic of great interest. The role of highly cross-linked polyethylene, with its altered mechanical properties, remains uncertain. Direct-compression-molded polyethylene continues to demonstrate very good clinical results. Meding, in a report on knees that had a 4.4-mm-thick, flat-on-flat, metal-backed, nonmodular, compression-molded polyethylene liner, found no radiographic evidence of polyethylene wear or osteolysis at a mean of ten years of follow-up. Jacobs presented the results of a retrieval study that also demonstrated the superiority of compression-molded liners compared with machined liners in knees with a cruciate-retaining prosthesis. The issue of polyethylene conformity and wear was addressed in two studies. Jacobs compared surface damage in prostheses with conforming and nonconforming geometries and found similar modes of damage governed by kinematic factors. Colwell, using a finite-element model, found that increased conformity substantially reduced stresses in a well-aligned knee. Increased conformity appears to be detrimental in the presence of rotational or coronal plane malalignment, suggesting that mobile-bearing knee inserts may have an advantage in this regard. Backside wear remains a concerning finding associated with modular tibial components. Rodriguez found backside wear in fourteen of fourteen posterior stabilized knee prostheses in patients who were undergoing revision for synovitis or osteolysis. Conditt et al. reported backside wear in more than 90% of eighty-four retrieved polyethylene inserts of twelve different implant designs with different locking mechanisms. The wear was more severe on the medial side. Engh found that the stability of the locking mechanism deteriorated in vivo with increasing backside wear. These reports raise the question of the role of modularity in the design of the tibial component. Revision Total Knee Arthroplasty Engh et al. investigated the results of isolated exchange of sixty-three polyethylene inserts in fifty-six patients who had had a total knee arthroplasty and found a high rate of early failure (27% within five years) secondary to accelerated wear of the new insert9. They recommended that isolated exchange of the polyethylene component not be performed in the presence of accelerated wear within ten years after the primary procedure. Trousdale also found a high rate of revision (25%) at a mean of five years after isolated revision of the polyethylene component in fifty-six knees. Silverton found a 35% rate of complications (all of which were related to the patellofemoral articulation) in association with isolated revision of the patellar component in forty knees. Barrack reported similar clinical results in patients treated either with retention of a well-fixed patellar component at the time of revision or with patellar revision to an all-polyethylene component. Technical controversies center around the use of, and the fixation techniques for, stemmed components in revision knee arthroplasty. With regard to the necessity for revision components, Bugbee reviewed 139 revisions and found a 26% rate of failure after revisions performed with primary knee components and only a 3% rate after revisions with implants designed for revision arthroplasty, which suggests that primary implants should be used very cautiously in the revision setting. Nazarian found comparable rates of loosening in association with Insall-Burstein constrained condylar knee implants with and without stems, which suggests that a semiconstrained device does not necessarily require a stem. Jazrawi found that use of long (150-mm) press-fit stems resulted in stability of the tibial component similar to that obtained with short (75-mm) cemented stems, provided that a good press-fit was obtained. Trousdale reported excellent clinical results and durable fixation (a 94% rate of revision-free survival) at a mean of ten years after revision with a long-stem cemented component in forty knees. Bone defects that are present at the time of revision total knee arthroplasty can be difficult to manage. Benjamin found that use of morselized bone graft in femoral and tibial defects in which structural support was provided by host bone was very successful. In a group of fourteen knees with more extensive bone loss, Nazarian found that use of massive structural allografts for extensive distal femoral defects led to an 86% rate of clinical success and allograft-hostunion at a mean of 3.6 years. The only failures were in patients who had recurrent infection. Barrack reported on the use of modular rotating hinges in patients who had had revision for a variety of indications; at a mean of fifty-one months, the clinical and radiographic results were similar tothose in a cohort that had had revision with a standard condylar implant. Tribute The orthopaedic community suffered a great loss with the passing of John Insall this year. Dr. Insall had an unparallelled influence on the field of adult knee reconstruction, and he will be sorely missed.
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