Patellar Component Research Articles

Long-term results of a cementless knee prosthesis with a metal-backed patellar component: clinical and radiological follow-up with histology from retrieved components.

Aseptic loosening of cemented knee arthroplasties has encouraged development of uncemented fixation. The Miller-Galante I (MG I) prosthesis was designed to achieve permanent stability through ingrowth into a titanium fiber mesh. Thirty-five knees in 30 patients with MG I knee replacements have been followed clinically and radiologically with a mean follow-up of 12 years. Twenty knees were revised with a mean follow-up of 5 years. Patellofemoral problems, especially avulsion of the polyethylene from the metal-backed patella and in some cases severe metallosis, have been the main reason for revision. Metal-backed patellar component should be avoided. In addition, instability has been a problem. However, the fixation of the components has been excellent, with a high degree of osseous ingrowth displayed at histological analysis of retrieved components. The clinical and radiological results after revision are in most cases good, despite the femoral component having been left in situ.

モーバイルベアリングインサートの摩耗，破損を生じたＬＣＳ人工膝関節の２例

From December 1991 to April 1995, 70 consecutive New Jersey low-contact stress (LCS) total knee arthroplasties (TKAs) were performed. Twenty two TKAs were done using rotating platform tibial component, and 48 were done using meniscal bearing tibial component. Two patients sustained bearing insert failure at eight years after primary TKA. Subluxation of tibiofemoral articulation occurred in one case, secondary to increased polyethylene wear and ligamentous instability. It was corrected easily by the insertion of a thicker bearing. The other case had patellar bearing breakage with delamination, but patellofemoral maltracking was not seen. The polyethylene of the patellar component was changed, improving the condition of both patients with relief of pain. Component failure, especially polyethylene wear and breakage were found to occur frequently.

Posterior cruciate–retaining modular total knee arthroplasty: A 9- to 12-year follow-up investigation

Between November 1988 and January 1991, 101 press-fit condylar (PFC; Johnson & Johnson, Raynham, MA) posterior cruciate–retaining total knee arthroplasties were performed in 75 patients. All tibial components were modular metal-backed, and all patellar components were all-polyethylene. All living patients were evaluated at an average 10.5 years (range, 9.5–11.8 years). Only 1 knee required revision (at 11.1 years after the procedure), and only 1 other knee had evidence of radiographic failure. The average range of motion was 1° (range, 0° –10°) to 110° (range, 86°–130°). At 10 years of follow-up, the probability of prosthesis survival was 100%, and at 12 years, the probability of prosthesis survival was 93.3% (endpoint defined as revision for any reason). Copyright 2002, Elsevier Science (USA). All rights reserved.

Treatment of an intraoperative patellar fracture during revision total knee arthroplasty

An intraoperative vertical patellar fracture occurred through a central osteolytic defect during removal of a metal-backed patellar component. The fracture was treated successfully with cerclage wire fixation and implantation of a cemented patellar component. Copyright 2002, Elsevier Science (USA). All rights reserved.

Gull-Wing Sagittal Patellar Osteotomy in Total Knee Arthroplasty

Compromised patellar bone stock poses significant technical challenges in knee revision surgery. The alternatives that have been proposed include reinsertion of a biconvex patellar component, patellar bone grafting, patellectomy, and leaving the unresurfaced patellar bone remnant in place. Various results have been reported with these methods, but not one of them has yet been widely accepted. A novel sagittal osteotomy that was used in four patients is described. This osteotomy leaves the extensor mechanism intact and allows the medial and lateral halves of the residual patella to hinge open in the shape of a “gull wing.” This conforms to the femoral trochlear groove and when combined with particulate bone grafts, it consolidates as a mass resembling a patella. The procedure has been limited to severe cases and obviates the need for patellectomy.

Periprosthetic fracture of the tibia associated with osteolysis caused by failure of rotating patella in low-contact–stress total knee arthroplasty

Periprosthetic fracture of the tibial plateau associated with osteolysis resulting from mechanical failure of the rotating patellar component after total knee arthroplasty with the New Jersey Low-Contact-Stress (LCS) knee (DePuy, Warsaw, IN) has not been reported previously. A 67-year-old woman with rheumatoid arthritis of the left knee had a LCS prosthesis implanted without cement, using a rotating patellar component. Seven years later, a fracture of the lateral tibial plateau occurred owing to an osteolytic defect with no traumatic accident. The rotating patellar bearing over-rotated and locked; consequently, wear occurred between the patellar metal tray and the femoral component. Immunohistochemistry revealed CD68-positive macrophages in the osteolytic region and phagocytosis of metal particles. The osteolytic region was filled with autogenous bone, and all components were exchanged and cemented. The patient's condition became satisfactory with relief of pain. Copyright 2002, Elsevier Science (USA). All rights reserved.

Clinical outcome and patient satisfaction in aseptic and septic revision total knee arthroplasty

This study compares clinical outcome and patient satisfaction in 33 aseptic and 15 septic revision total knee arthroplasties across a 30–130-month follow-up. Aseptic revisions included only knees in which the femoral, tibial and patellar components had been exchanged, and excluded knees in which only isolated patellar components had been revised or only the tibial insert exchanged. Septic revisions included only knees in which there had been successful revision for chronic infection without recurrence of infection for at least 2 years from the index revision. The evaluation included pain scores, knee scores, functional scores, SF-12 functional surveys and radiographs of the knee. The results for the aseptic group were excellent in 26 (78.8%), good in 3 (9.0%), fair in 2 (6.1%) and poor in 2 (6.1%); those for the septic group were excellent in 5 (33.3%), good in 7 (46.7%), fair in 2 (13.3%) and poor in 1 (6.7%). The overall results of septic revision were less satisfactory than for aseptic revision. Aseptic revisions achieved significantly better knee scores and ranges of motion than septic revisions, but their pain and functional scores were similar. Despite the difference in knee scores, 85% of the patients from both groups were equally satisfied with the results of treatment. There was no discernible radiographic difference between the two groups, including radiolucency.

Factors affecting patellar tracking after total knee arthroplasty

This study examined factors that influence patellar tracking after total knee arthroplasty. A total of 62 knees were evaluated radiographically for postoperative patellar tracking. Six factors were examined regarding their influence on postoperative patellar tracking. This study showed the effects of patellar component position, patellar resection angle, and lateral retinacular release on postoperative patellar tracking. There was no significant effect of the remaining 3 factors: the thickness of the patellar resection, preoperative patellar tilt, and rotational alignment of the femoral component. A medialized patellar component and obliquity of resection of the patella are effective for obtaining proper patellar tracking, whereas the evaluation of the influence of the external rotation of the femoral component requires more clinical studies. Copyright 2002, Elsevier Science (USA). All rights reserved.

Press-fit metal-backed rotating patella: seven- to 14-year followup.

A consecutive series of 80 patients with 110 press-fit metal-backed rotating platform patella resurfacing surgeries were reviewed at an average of 107 months followup (range, 84-167 months). Twenty-eight patients died before followup. Fifty-two patients (70 patellae) were available for clinical and radiographic followups. One patella was revised for failure of the patella component. Four patellae were revised along with revision of the knee replacement. One patella realignment procedure was done for recurrent subluxation of the patella. There were no patellar dislocations in this series, no patella fractures, and no disruption of the quadriceps tendon or infrapatellar ligament. Six patellae had subluxation seen on postoperative radiographs. The incidence of patellar tilt greater than 5 degrees was 13%. No patellae were considered radiographically loose. The incidence of radiolucencies was 37%. Subsidence of the component superiorly was identified in 39% of the patellae, and inferiorly in 36% of the patellae. Of the 49 patients (67 knees) returning for followup, 70% of the knees were rated as excellent, 10% were rated good, 15% were rated fair, and 5% were rated poor. Press-fit metal-backed patella provided good component durability with only one revision because of component failure. Radiographic analyses showed a high incidence of subsidence associated with good clinical results.

Dissecting popliteal cyst resulting from a fragmented, dislodged metal part of the patellar component after total knee arthroplasty

Dissecting popliteal cyst is an uncommon complication after total knee arthroplasty, occurring mainly as a result of either rheumatoid arthritis or a malfunctioning knee prosthesis. Its association with a failed metal-backed patellar component has not been reported since the introduction of the resurfacing of the patella with this kind of design in 1980. We present a case of a late fracture-dislocation of the metal part of the patellar component that migrated to the posterior popliteal fossa, resulting in a cystic mass formation caused by a foreign body granuloma. The patient was treated successfully with a 2-stage operation: first, revision of the total knee arthroplasty and, second, excision of the cyst. The patient had a pain-free functional knee 7 years after surgery, with no recurrence of the symptoms or the popliteal cyst. Copyright 2002, Elsevier Science (USA). All rights reserved.

Sonographic appearance of fibrous nodules in patellar clunk syndrome: a case report

AbstractPatellar clunk syndrome is a rare complication causing pain after total knee arthroplasty. However, it is important to differentiate it from the other causes of patellofemoral pain. In this article, we apply ultrasonography for the first time to demonstrate the suprapatellar fibrous tissue causing this condition. A 50-year-old woman with rheumatoid arthritis had left total knee arthroplasty. The patient had excellent results until 2 years after surgery, when she complained of anterior knee pain. On physical examination, a patellar“catch” and “pop” were noted from 45° flexion to full extension. Roentgenograms showed a radiolucent line at the upper pole of the patella and no subluxation of the patella on skyline view. Sagittal and transverse gray-scale sonographic images revealed an echogenic area attached to the quadriceps tendon. Corresponding color Doppler sonographic images showed marked vascularity in this echogenic area. The patient was treated with removal of the suprapatellar tissue and a patellar component revision. Intraoperatively, the suprapatellar tissue, which measured 4 × 4 × 2 cm, entered the notch area of the femoral component on flexion and caused the patellar “pop” on knee extension. Pain relief was obtained immediately after the operation when smooth gliding motion of the patella was restored.

Patellar component resection arthroplasty for the severely compromised patella.

When severe bone loss precludes reimplantation of a new patellar component during revision knee arthroplasty, the treatment options include patellar bone grafting, patellar component resection arthroplasty, and patellectomy. The purpose of this study was to evaluate the clinical and functional results of patellar component resection arthroplasty for the severely compromised patella for which insertion of another patellar component was not possible. Thirty-five knees (31 patients) were treated with patellar component resection arthroplasty for aseptic patellar component failure associated with severely compromised patellar bone stock. Followup averaged 7.9 years (range, 2-18 years). There was a significant improvement in Knee Society pain and function scores. Pain relief was more dramatic than functional improvement. The range of motion also improved significantly and in particular preoperative extensor lag was resolved in the majority of patients. Patients treated with isolated patellar resection arthroplasty were more likely to have continuing pain and require reoperation compared with patients who had concomitant revision of the tibial and femoral components. Correct positioning and the stability of tibial and femoral components should be tested carefully at the time of patellar resection arthroplasty and considered for revision if malpositioned either axially or rotationally.

Patellar fracture after total knee arthroplasty.

Patellar fracture can occur as a complication following total knee arthroplasty. The purpose of this study was to evaluate a large series of patellar fractures to determine the results of different forms of treatment of specific fracture types. A retrospective review identified eighty-five fractures (in seventy-seven patients) following 12,464 consecutive total knee arthroplasties performed between 1985 and 1998. Seventy-eight fractures occurred after primary total knee arthroplasty and seven, after revision total knee arthroplasty. Five fractures were treated elsewhere, and two others were lost to follow-up. The results of treatment of the remaining seventy-eight fractures were reviewed. Fractures were classified according to three main criteria: integrity of the extensor mechanism, fixation status of the patellar implant, and quality of the remaining bone stock. The mean duration of follow-up was 3.6 years. The prevalence of patellar fracture after total knee arthroplasty was 0.68%; fractures were significantly more prevalent among men (1.01%) than among women (0.40%) (p = 0.0004). Thirty-eight fractured patellae had a stable implant and an intact extensor mechanism (Type I). All but one were treated nonoperatively, and there was only one late failure of nonoperative treatment, which required operative intervention. Twelve fractures were associated with disruption of the extensor mechanism (Type II). Eleven were treated operatively; six knees had complications and five had a reoperation. Twenty-eight fractures occurred in association with a loose patellar component (Type III). Twenty were treated operatively; nine knees had complications, and four had a reoperation. Patellar fractures after total knee arthroplasty are infrequent. Treatment can be guided by three main criteria: integrity of the extensor mechanism, fixation status of the patellar implant, and quality of the remaining bone. Fractures associated with a stable implant and an intact extensor mechanism were usually treated successfully with nonoperative means, with minimal complications. When operative treatment was required, it was associated with a high rate of complications and reoperations.

The clinical history of mobile-bearing patella components in total knee arthroplasty.

Two hundred fifty-six primary cementless meniscal-bearing total knee arthroplasties were performed between May 1985 and January 1989. All knees were replaced with a low contact stress metal-backed anatomic mobile patella. The average patient follow-up was 11.5 years. No patellae were revised for failure of fixation and no dislocations or subluxations were reported. One patella was revised for polyethylene wear, and one well-functioning component was removed at the time of revision to facilitate range of motion and wound closure. The survival estimate at 12 years was 99.5%. Compared to the high incidence of failure of metal-backed fixed-bearing patellae components, the anatomic rotating patella provides durable long-term results with a low incidence of complications.

Ten to fourteen year survival and functional analysis of the AGC total knee replacement system

A study of 562 Anatomic Graduated Component (AGC) total knee arthroplasties that were performed in 402 patients between November 1986 and September 1990 is reported. All patients had implantation with a cemented posterior cruciate-retaining design, with resurfacing of the patella using all polyethylene patella components. Mean age at surgery was 71 years (range 41–92 years). Patients were followed for a minimum of 10 years (range 10–14 years). Nine knees were lost to follow-up (1.4%). The mean Knee Society Score for pain and function were analyzed by Charnley categories: Category A — 97 (pain) and 89 (function); Category B — 91 (pain) and 84 (function); and Category C — 89 (pain) and 62 (function). The survival analysis at 14 years was 97% with revision for any reason as the endpoint and the authors continue to utilize this implant system.

Press-fit versus cemented all-polyethylene patellar component: Midterm results

This study compared the midterm results between press-fit and cemented implantation of a highly congruent, all-polyethylene patellar component. We followed prospectively 172 implants (cemented, n = 133; press-fit, n = 39). Average follow up was 6 years (range, 5[ndash ]8 years). Patellofemoral complications occurred in 4 cemented patellae (2.3%). Two of these patellae required revision. Cemented implants had a significantly higher incidence of patellar maltracking (30% vs 8%; P=.005). No significant differences in the overall Knee Society scores (mean, 165; SD, 27) or any of its components relevant to patellofemoral function were detected between fixation methods. A retrieved specimen showed an intervening fibrous membrane at the implant[ndash ]bone interface. The potential for macrophage-mediated osteolysis at this site is unknown. No other adverse outcome was associated with press-fit implantation. These results suggest that at midterm follow-up, press-fit implantation of this all-polyethylene patellar component may improve tracking and represents a viable alternative to cement fixation.

Six cases of patellar component failure in Miller-Galante total knee arthroplasty

Six cases of patellar component failure in Miller-Galante total knee arthroplasty

Early failures among 7,174 primary total knee replacements: a follow-up study from the Norwegian Arthroplasty Register 1994-2000.

We studied primary total knee replacements (TKRs), reported to the Norwegian Arthroplasty Register, operated on between 1994 and 2000. A Cox multiple regression model was used to evaluate differences in survival among the prosthesis brands, their types of fixation, and whether or not the patella was resurfaced. In Norway in 1999, the incidence of knee prosthesis operations was 35 per 100,000 inhabitants. Cement was used as fixation in 87% of the knees, 10% were hybrid and 2% uncemented implants. Bicompartmental (not resurfaced patella) prostheses were used in 65% of the knees. With all revisions as endpoint, no statistically significant differences in the 5-year survival were found among the cemented tricompartmental prostheses brands: AGC 97% (n 279), Duracon 99% (n 101), Genesis I 95% (n 654), Kinemax 98% (n 213) and Tricon 96% (n 454). The bicompartmental LCS prostheses had a 5-year survival of 97% (n 476). The type of meniscal bearing in LCS knees had no effect on survival. Survival with revision for all causes as endpoint showed no differences among types of fixation, or bi- or tricompartmental prostheses. Pain alone was the commonest reason for revision of cemented bicompartmental prostheses. The risk of revision because of pain was 5.7 times higher (p < 0.001) in cemented bicompartmental prostheses than cemented tricompartmental ones, but the revisions mainly involved insertion of a patellar component. In tricompartmental prostheses the risk of revision because of infection was 2.5 times higher than in bicompartmental ones (p = 0.03). Young age (< 60) and the sequelae after a fracture increased the risk of revision. The 5-year survival of the 6 most used cemented tricompartmental knee prostheses brands varied between 95% and 99%, but the differences were not statistically significant. There were more revisions because of pain in bicompartmental than in tricompartmental knees. In tricompartmental knees, however, there were more revisions because of an infection. The relatively few patients with uncemented and hybrid implants showed no improvements in results compared to cemented knee prostheses.

Outcome of metal-backed cementless patellar components: the effect of implant design.

Failure of metal-backed cementless patellar components frequently has been observed clinically. To determine the effect of component design on clinical outcome, the authors reviewed the results of total knee arthroplasty with metal-backed patellar components of two different designs. The results of 168 total knee arthroplasties (Miller-Galante) with dome-shaped metal-backed patellar components and 93 total knee arthroplasties Miller-Galante II with modified dome-shaped metal-backed patellar components were reviewed. Kaplan-Meier survivorship was determined for both groups. Revision for patellar wear or failure was done or recommended in 36 Miller-Galante total knee arthroplasties. The cumulative survival rates at 3, 5, 7, and 9 years postoperatively were 99%, 92%, 81%, and 73%, respectively for this group. In contrast, only three of 93 Miller-Galante II patellar components required revision. Catastrophic patellar component failure, typically seen with the Miller-Galante metal-backed patellar components, was not observed with the Miller-Galante II components. Cumulative survival of the Miller-Galante II patella at 3, 5, 7, and 9 years postoperatively was 100%, 100%, 98.7%, and 93.2% respectively. The results of the current study show a dramatic reduction in metal-backed component failure by design changes incorporated into the modified dome-shaped Miller-Galante II patellar component and highlights the importance of design on the survival of cementless metal-backed patellar components.

Quadriceps moment arm and quadriceps forces after total knee arthroplasty.

Knee prosthetic designs that increase quadriceps moment arm can reduce quadriceps tension and patellofemoral compressive forces. Six knees from cadavers were tested on the Oxford knee rig, which simulates closed chain knee extension under load. Three conditions were tested sequentially for each knee: Normal, Control (implanted with the Osteonics 7000 knee design), and Scorpio (implanted with the Osteonics Scorpio design). The center of flexion-extension of the Scorpio design was 10 mm posterior to that of Control that served to lengthen the quadriceps moment arm. An electromagnetic tracking system measured dynamic knee kinematics, and a uniaxial load cell measured quadriceps tension. The Scorpio design reduced quadriceps tension when compared with the Normal or Control knee ranging from 5% to 20%. This was statistically significant at flexion angles greater than 50 degrees. In three knees, the patellar component was instrumented with a triaxial load cell that measured patellofemoral forces. Patellofemoral forces were lower with the Scorpio design compared with the Control. Increasing quadriceps lever arm reduces quadriceps forces and can facilitate activities of daily living and enhance patient rehabilitation. Reduced quadriceps forces may result in reduced patellofemoral forces that can have a beneficial effect on anterior knee pain, patellar component wear, and loosening.