Metal-backed Patellar Component Research Articles

Cementless metal-backed patellar components in primary total knee arthroplasty using an implant of modern design.

The use of cementless total knee arthroplasty (TKA) components has increased during the past decade. The initial design of cementless metal-backed patellar components had shown high failure rates due to many factors. The aim of this study was to evaluate the clinical results of a second-generation cementless, metal-backed patellar component of a modern design. This was a retrospective review of 707 primary TKAs in 590 patients from a single institution, using a cementless, metal-backed patellar component with a mean follow-up of 6.9 years (2 to 12). A total of 409 TKAs were performed in 338 females and 298 TKAs in 252 males. The mean age of the patients was 63 years (34 to 87) and their mean BMI was 34.3 kg/m2 (18.8 to 64.5). The patients were chosen to undergo a cementless procedure based on age and preoperative radiological and intraoperative bone quality. Outcome was assessed using the Knee Society knee and function scores and range of motion (ROM), complications, and revisions. A total of 24 TKAs (3.4%) in 24 patients failed and required revision surgery, of which five were due to patellar complications (0.71%): one for aseptic patellar loosening (0.14%) and four for polyethylene dissociation (0.57%). A total of 19 revisions (2.7%) were undertaken in 19 patients for indications which did not relate to the patella: four for aseptic tibial loosening (0.57%), one for aseptic femoral loosening (0.14%), nine for periprosthetic infection (1.3%), one for popliteus impingement (0.14%), and four for instability (0.57%). Knee Society knee and function scores, and ROM, improved significantly when comparing pre- and postoperative values. Survival of the metal-backed patellar component for all-cause failure was 97.5% (95% confidence interval 94.9% to 100%) at 12 years. The second-generation cementless TKA design of metal-backed patellar components showed a 97.5% survival at 12 years, with polyethylene dissociation from the metal-backing being the most common cause of patellar failure. In view of the increased use of TKA, especially in younger, more active, or obese patients, these findings are encouraging at mean follow-up of seven years.

Cementless and Cemented Total Knee Arthroplasties Have Similar Outcomes but Cementless Patellar Component Migration was Observed in a Paired Randomized Control Trial

BackgroundCementless total knee arthroplasty (TKA) has become increasingly popular. Some surgeons are concerned about pain, implant stability, and metal-backed patellar component survivorship. This study investigated the outcomes of cementless compared with cemented TKA in bilateral cases. MethodsWe randomized 80 knees in 40 osteoarthritic knee patients who underwent bilateral TKA with patellar resurfacing under one anesthesia. All participants received cementless prostheses in one knee and cemented prostheses in the other. The outcomes were knee function measured by the forgotten joint scores, modified Western Ontario and McMaster Universities Osteoarthritis Index, knee ranges of motion, pain levels, operative times, radiographic outcomes, and complications. All knees were followed for a minimum of 2 years (2 to 3 years). ResultsCementless and cemented TKA had similar functional outcomes in forgotten joint score (97 ± 5 versus 98 ± 3 points, P = .52), modified Western Ontario and McMaster Universities Osteoarthritis Index score (3 ± 4 versus 3 ± 2 points, P = .96), and ranges of motion (134 ± 7° versus 134 ± 7°, P = .16). The postoperative pain was also similar (P > .05). There were 4 cementless patellar components had superior migration for an average of 3.5 mm (range, 1.77 to 4.16) without loosening. The mean time of migration was 4 (range, 2 to 6) weeks. ConclusionsCementless TKA had similar functional outcomes and recovery patterns compared with cemented TKA. However, there was concern of cementless component migration at patellae.

Results of a Highly Porous Metal-Backed Cementless Patella Implant: A Minimum 5-Year Follow-Up.

Initial design cementless metal-backed patellar implants failed due to multiple reasons including implant design, use of first-generation polyethylene, and surgical technique. This study evaluates clinical outcomes and survivorship of total knee arthroplasty (TKA) using a current generation highly porous metal-backed patellar component. One-hundred twenty-five consecutive primary cementless TKAs with a compression molded highly porous metal-backed patella were reviewed. One-hundred three TKAs (82.4%) with 5-year clinical and radiographic follow-up were available for review. These were matched with 103 consecutive TKAs using a cemented patella of the same implant design. The cementless cohort had a mean age of 65.5 years, body mass index (BMI) of 33.0, and follow-up of 64.4 months. Indications for cementless TKA were based on multiple factors including age, BMI, and bone quality. There were no revisions for loosening or mechanical failure of the cementless patella compared with two cemented patellae revised for aseptic loosening. Eight patients required revisions in the cementless cohort: three for prosthetic joint infection (PJI), two for instability, one periprosthetic femur fracture, one for patella instability, and one for extensor mechanism rupture. Five patients required revisions in the cemented cohort: two for aseptic patellar loosening, one for aseptic femoral loosening, one for PJI, and one for instability. All-cause survivorship at 5 years was 92.2 and 95.1% for the cementless metal-backed implant and cemented implant cohorts, respectively. Use of a compression molded highly porous metal-backed patella component demonstrated excellent clinical and radiographic results at 5-year follow-up. Longer follow-up is required to evaluate the ability of highly porous cementless patella implants to provide durable long-term fixation.

Cementless Metal-Backed Patellar Components in Primary Total Knee Arthroplasty: An Average 10-Year Follow-Up

BackgroundHistorically, 1st generation metal-backed cementless patellar implants demonstrated high failure rates due to multiple factors. The 2nd generation cementless implants were developed with purported improvements in component design and polyethylene wear characteristics. This study evaluated clinical results of a current generation cementless metal-backed patellar implant with a minimum 5-year follow-up. MethodsOne hundred and thirty-six primary total knee arthroplasties (TKAs) with metal-backed cementless patellae were compared to 183 cemented patellae with the same implant design. The cementless group mean age was 61 years (range, 40 to 81), mean body mass index (BMI) of 34.9 (range, 22.6 to 64.5), and mean follow-up of 10 years (range, 5 to 13). The cemented group mean age was 65 years (range, 32 to 89), mean BMI of 32.5 (range, 18.2 to 56.6), and mean follow-up of 10 years (range, 5 to 12). Significant demographic differences of age (P < .001), BMI (P < .01), and sex (P < .001) were found, with cementless patients being younger, heavier, and with more men. ResultsThere were no statistical differences in non-revision procedures (P = .214), TKA revisions (P = .639), patellar revisions (P = .151), and patellar aseptic loosening (P = .737). The 10-year survivorship of the cementless metal-backed patella was 95.9% with all-cause failure as the endpoint. The 10-year survivorship of the cemented patellar component was 98.9%. ConclusionThis study demonstrated noninferiority of a 2nd generation HA-coated cementless metal-backed patellar implant in primary TKA compared to cemented patellae with 10-year survivorship of 95.9%. Advances in implant design and polyethylene wear properties have led to improved clinical results with metal-backed patellar components in primary TKA.

Radiographic evaluation of patellofemoral alignment in kinematically aligned total knee arthroplasty: A comparative study with mechanically aligned total knee arthroplasty

BackgroundKinematically aligned total knee arthroplasty (KA-TKA), in which femoral component is placed 3–5° of internal rotation relative to mechanically aligned (MA)-TKA, may have a potential risk of patellofemoral malalignment. This study aimed to assess patellofemoral alignment and compare the data between KA-TKA and MA-TKA, and the relationship with patellofemoral radiographic parameters and patient reported outcomes. MethodsAmong patients who underwent TKA in 2015 and 2016 in our institute, 28 KA-TKAs with a metal-backed patellar component were retrospectively assessed for patellofemoral alignment, and 28 MA-TKAs with a metal-backed patellar component served as controls. A year postoperatively, patellar tilt and shift at 30°, 60°, and 90° knee flexion were measured on Merchant views and compared between the two TKAs. Implant positioning in each patient was assessed based on preoperative CT images and correlations of femoral component positioning with patellar tilt/shift were assessed. ResultsPatellar shift at 30° flexion was significantly greater in KA-TKA than in MA-TKA (p = 0.04), whereas patellar tilt angle was comparable between the two TKAs. No statistical correlation was evident between femoral component positioning and patellar shift/tilt, regardless of knee flexion angle in the two TKAs. Knee Society Score 2011 at 1 year follow-up was comparable in all subcategories between the two TKAs. ConclusionRadiographic analysis of KA-TKA revealed lateral shift of the patella at 30° knee flexion at 1 year postoperatively, however patients with patellar shift were asymptomatic. Further long-term observation is required to examine the impact of KA-TKA on the patellofemoral complication.

Metallosis after knee replacement: a review.

Although metallosis is a well-known complication after total hip arthroplasty, little is known about this phenomenon after total (TKA) or unicompartmental knee arthroplasty (UKA). The aim of the present work was to review the current knowledge about the reasons and the diagnostic as well as therapeutic management of metallosis after knee arthroplasty. A literature search was performed through PubMed until April 2019. Search terms were "metallosis" in combination with "knee", "knee prosthesis", "knee arthroplasty" and "knee replacement", respectively. All publications were analyzed regarding publication year, level of evidence, number of knees/patients treated, type of prosthesis, metallosis cause, time period between primary implantation and metallosis emergence, laboratory examination, treatment, complications and follow up. A total of 38 studies reporting on a total of 97 knees were identified. 29 studies reported on metallosis after TKA, 8 after UKA, and one study after both procedures. The time period between the primary implantation and metallosis emergence ranged between 6weeks and 26years. The most common reason was the failure of a metal-backed patellar component in 40%, followed by implant/structural- and PE failure (wear/dislocation) in 27% and 18% of the cases, respectively. Complete blood cell count, serum chemistry, erythrocyte sedimentation rate or C-reactive protein serum values were not indicative to diagnose metallosis. The diagnosis was confirmed by histopathological analyses and macroscopic evaluation during surgery. Depending on the particular cause various surgical procedures have been performed. Complete prosthesis exchange was the most common one showing no complications in 89.4% of the cases. Metallosis after knee arthroplasty is a rare and perhaps underestimated or under published complication. A systematic diagnostic approach is necessary for the timely and correct diagnosis. A thorough debridement as well as a (sub)total synovectomy should be always performed. In cases with a damaged component, a partial/complete prosthesis exchange leads to the best results. Should a malalignment be the cause of the metallosis, then it should be corrected within the revision surgery.

Evaluation of a 3D-printed total knee arthroplasty using radiostereometric analysis: assessment of highly porous biological fixation of the tibial baseplate and metal-backed patellar component.

Our intention was to investigate if the highly porous biological fixation surfaces of a new 3D-printed total knee arthroplasty (TKA) achieved adequate fixation of the tibial and patellar components to the underlying bone. A total of 29 patients undergoing primary TKA consented to participate in this prospective cohort study. All patients received a highly porous tibial baseplate and metal-backed patella. Patient-reported outcomes measures were recorded and implant migration was assessed using radiostereometric analysis. Patient function significantly improved by three months postoperatively (p < 0.001). Mean difference in maximum total point motion between 12 and 24 months was 0.021 mm (-0.265 to 0.572) for the tibial implant and 0.089 mm (-0.337 to 0.758) for the patellar implant. The rate of tibial and patellar migration was largest over the first six postoperative weeks, with no changes in mean tibia migration occurring after six months, and no changes in mean patellar migration occurring after six weeks. One patellar component showed a rapid rate of migration between 12 and 24 months. Biological fixation appears to occur reliably on the highly porous implant surface of the tibial baseplate and metal-backed patellar component. Rapid migration after 12 months was measured for one patellar component. Further investigation is required to assess the long-term stability of the 3D-printed components and to determine if the high-migrating components achieve fixation. Cite this article: Bone Joint J 2019;101-B(7 Supple C):40-47.

Evaluating the progression of osteolysis after total knee arthroplasty.

Osteolysis around the knee following total knee arthroplasty continues to be a leading cause for revision total knee arthroplasty. Risk factors for periprosthetic knee osteolysis are associated with excessive polyethylene wear and include, but may not be limited to, malalignment of the mechanical axis, early-generation polyethylene sterilization techniques, excessive backside polyethylene wear, metal-backed patellar components, patient age, and an elevated body mass index. The initial diagnosis of osteolysis is frequently discovered on routine surveillance radiographs. The location, size, progressive nature, and associated symptomatology of the defect guides treatment. Surgical indications and timing are predicated on the risk of failure with continued observation. Advanced imaging helps to quantitate the size and location of osteolytic lesions as accurately as possible and aids in preoperative planning. When deciding whether surgery or management with continued radiographic surveillance is indicated, a global assessment of the character and progression of the osteolysis must be weighed with the risk factors associated with the patient.

Long-Term Follow-Up of Anatomic Graduated Component Total Knee Arthroplasty: A 15- to 20-Year Survival Analysis

The aims of this study were to determine survival rate, the clinical performance, and radiologic results of an Anatomic Graduated Component (AGC) total knee arthroplasty (TKA). Survival analysis was assessed by analyzing all hospital records of 211 AGC TKAs in 177 patients after 15 to 20 years. The survival rate was 87%, with failure defined as revision for any reason including infection. The main reasons for failure were infection and failure of the metal-backed patellar component. Clinical evaluation of 30 patients (33 TKAs) and questionnaires of 20 patients (23 TKAs) were taken, showing moderate to good results (mean Knee Society Score, 51; mean Western Ontario and McMaster Universities Osteoarthritis index, 82; mean University of California Los Angeles score, 4). Radiologic evaluation of 13 TKAs in 12 patients showed that none was suspect for loosening. Three knees showed significant medial wear but no clinical complaints. In conclusion, this is one of the first studies showing that AGC total knee prosthesis has good results 15 to 20 years after surgery.

Dissociation of mobile-bearing patellar component in low contact stress patellofemoral arthroplasty, its mechanism and management: two case reports

IntroductionIsolated patellofemoral osteoarthritis can be treated with patellofemoral arthroplasty.Case presentationWe present two cases of isolated patellofemoral osteoarthritis treated with Low Contact Stress patellofemoral arthroplasty; in both cases the polyethylene mobile-bearing of the patellar component dissociated from the metal backing. One patient had a revision to a Richards patellofemoral prosthesis, and in the second patient the arthroplasty was converted to a total knee prosthesis because of clinically important femorotibial osteoarthritis.ConclusionThe possible failure mechanisms are described. We suggest avoiding the use of a metal-backed mobile-bearing patellar component due to the risk of dissociation.

Isolated All-polyethylene Patellar Revisions for Metal-backed Patellar Failure

The outcome of isolated patellar component revisions after metal-backed patellar failure is variable with satisfactory results reported from 78% to 100%. To supplement information in the literature we determined the failure rate and the functional outcome based on the Knee Society clinical and roentgenographic evaluation systems of isolated patellar component revisions after metal-backed patellar component failure. We retrospectively reviewed 27 patients with 28 isolated patellar component revisions for metal-backed patellar component failure performed between 1988 and 2005. Twenty-five knees in 24 patients were available for review with a minimum followup of 24 months (mean, 90 months; range, 24-210 months). All knees were revised with a cemented all-polyethylene patellar component and all tibial polyethylene components were routinely exchanged. One failure (4%) occurred 122.6 months after the isolated patellar component revision secondary to femoral and tibial component loosening. The average Knee Society knee score improved from 73 to 89 points, whereas the average Knee Society function score improved from 56 to 65. Our data confirm those in the literature suggesting a successful outcome can be achieved with an isolated patellar component revision for metal-backed patellar component failure. Level IV, retrospective case series. See the Guidelines for Authors for a complete description of levels of evidence.

Retention of Superficially Damaged Femoral Components After Metal-Backed Patella Component Failure

Metal-backed patellar components have been associated with high rates of failure often causing surface damage to the femoral component. Retention of a superficially damaged femoral component may be an alternative to a more extensive patellar and femoral component revision. Twenty-three metal-backed patellar components were revised. Superficially damaged femoral components were retained when a described set of criteria were met. At an average follow-up of 80.3 months, evidence of only 1 failure (4%) was observed. The Knee Society knee score improved from 69 to 88 ( P < .001), whereas the Knee Society knee function score improved from 52 to 63 ( P < .003). The findings from this study indicate that retaining a superficially damaged femoral component after metal-backed patella revision is a reasonable surgical option.

Cementless Fixation in Total Knee Arthroplasty –Past, Present, and Future

Cementless fixation in total knee arthroplasty (TKA) has had limited use in recent decades due to past failures in the early generation of cementless designs. Screw track osteolysis, poor polyethylene, and metal-backed patellar component failures contributed to a controversial track record and created a reluctance to embrace cementless fixation in TKA; however, these failure mechanisms are correctable. In addition, there is renewed interest in cementless fixation due to the recent development of improved biomaterials, particularly highly porous metals and highly crosslinked polyethylene, as well as time-saving advantages and long-term osseointegration of cementless fixation. There are long-term reports of successful designs of cementless knee arthroplasty that are nearly equal to the results of cemented designs. This article discusses the past history, current long-term results, and future of cementless fixation in TKA.

Isolated Revision of Failed Metal-Backed Patellar Components: Outcome With Minimum 4-Year Follow-Up

Several reports document high failure rates of metal-backed patellar components, but few report the outcome of revising these components to all-polyethylene, cemented implants. At a mean 87.2-month follow-up, we describe a series of 36 patients (40 knees) who underwent isolated metal-backed patellar revision to a cemented, all-polyethylene patellar component. After the patellar revision, 5 patients (6 knees) underwent additional surgery, but no patellar components required revision. The additional surgeries were performed at an average of 77.6 months after patellar revision and included 3 tibial insert exchanges for polyethylene wear, 2 revisions of femoral and tibial components for osteolysis, and 1 realignment procedure for recurrent subluxation of the patella. We conclude that revision of a failed metal-backed patellar component to a cemented, all-polyethylene patella is a durable, successful procedure.

Metal-backed patellar component failure in total knee arthroplasty presenting as a giant calf mass

Failure of total knee arthroplasty (TKA) caused by wear of the polyethylene-bearing surface of a metal-backed tibial platform or a metal-backed patellar component is a recognized complication. We present a case of a 78-year-old woman with a cystic mass in the left calf caused by metal wear debris from the failure of a Miller-Galante I TKA. The patient received a left TKA to treat advanced osteoarthritis in July 1990 and was lost to follow-up immediately after the operation. In December 1998, she presented at our clinic 2 days before admission, when an originally silent mass over the calf turned intolerably painful. A series of examinations revealed a calf mass caused by wear debris of total knee prosthesis and subsequent inflammation of the knee joint. Curettage of the cyst and simultaneous revision TKA were successful in relieving her symptoms. Copyright 2003, Elsevier Science (USA). All rights reserved.

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.

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.

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.

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.

Problems with cementless total knee arthroplasty at 11 years followup.

One hundred two patients with 131 consecutive cementless total knee arthroplasties that retained the posterior cruciate ligament were followed up prospectively. The average age of the patients was 58 years (range, 32-75 years). The mean followup on the surviving knee arthroplasties was 11 years (range, 7-16 years). The patellar component was metal-backed in the first 112 (85%) knees, cementless all-polyethylene in the last 17 (13%) knees, and two knees had a prior patellectomy. Forty-four metal-backed patellar components (48%) were revised; nine were loose, and 35 had polyethylene wear through. Thirteen femoral components (12%) were revised because of femoral abrasion from a failed metal-backed patellar component. No other femoral component was revised, loose, or had osteolysis develop. Nine (8%) tibial components had failure of ingrowth; eight have been revised. Partial radiolucencies occurred in 53% of the tibias. Thirteen (12%) small osteolytic lesions developed, all around screws or screw holes in the tibial components. At an average of 11 years followup, cementless fixation yielded mixed results: cementless femoral fixation was excellent and metal-backed patellar components had a 48% patellar revision rate. Cementless tibial components had an 8% aseptic loosening rate and a 12% incidence of small osteolytic lesions. Based on these results, the authors have abandoned cementless fixation in total knee arthroplasty.