Metal-backed Tibia Research Articles

Minimalinvasiv implantierte unikondyläre Knieendoprothese Typ Stryker-Osteonics mit metal-backed Tibiakomponente: Ein 5-Jahres-Follow-up

The aim of this study was to evaluate the medium-term results of minimally invasive unicompartmental knee joint arthroplasty with a metal-backed tibia component. Ninety-one unicompartmental knee replacements with a metal-backed tibia component, type SCR-Stryker Osteonics, were implanted in a minimally invasive technique in 91 patients between 1997 and 1999. The evaluation of medium-term results was based on The Knee Society Clinical Rating System by Insall and Scott and was done at 6 weeks, 1, 3 and 5 years after surgery. This rating system is based on the clinical and symptoms of the patient (maximum score 100). Preoperatively, the average knee score was 57.6 (44-66), the function score 63.3 (48-71). Throughout the period of investigation all patients had an increased knee and function score. One year after surgery the knee and function scores increased to 94.8 (39-100) and 93.6 (75-100). Five years post-implantation only 64 patients could be re-evaluated but they also had a knee and function score corresponding to the 3-year results [knee score: 98.2 (94-100); function score: 98.9 (85-100)]. Revision surgery using a total knee prosthesis was performed in 3 cases. The unicompartmental knee arthroplasty was a good surgical method for managing medial, unicompartmental arthritis of the knee joint. The results presented by the authors and corroborated by many literature data provide evidence that unicompartmental arthroplasty is of great importance in the treatment of unicompartmental knee arthritis. The results achieved by the minimally invasive technique of a unicompartmental knee arthroplasty with a metal-backed tibia component of the type Stryker-Osteonics were equal to the conventional surgical technique in literature. Good indications were patients older than 60 years with normal weight and normal sports activity. Well-functioning collateral and cruciate ligaments were mandatory. Moreover, the minimally invasive technique may lead to a shorter time of rehabilitation because of the reduced soft tissue damage.

Why Are Total Knee Replacements Revised?

Since 1991, 5760 knee arthroplasty procedures done by 53 surgeons have been registered in a community joint implant registry and were reviewed regarding initial revision done within the healthcare system. The 168 revisions done represented 2.9% of the knee arthroplasties between September 1991 and December 2002. Survival was defined as the absence of revision surgery. Death was considered a censored event. Cumulative survival rates for the different total knee arthroplasty configurations were: cemented total knee arthroplasty with all-polyethylene tibia, 99.2%; cemented total knee arthroplasty with metal-backed tibia, 96.3%; hybrid total knee arthroplasty, 89.3%; and unicondylar knee arthroplasty, 87.2%. Cemented total knee arthroplasty with metal-backed tibia had better survival than hybrid total knee arthroplasty, ingrowth total knee arthroplasty, and unicondylar knee arthroplasty. Cemented total knee arthroplasty with a metal-backed tibia did not have better survival than cemented total knee arthroplasty with an all-polyethylene tibia. Gender was not related to survival. Age was related to survival, with older patients' knees surviving longer. Aseptic loosening or wear was the cause of revision in 40.8% of patients having total knee arthroplasty and 46.6% of patients having unicondylar knee arthroplasty, whereas progression of arthritis necessitated unicondylar knee revision in 51.2% of patients having that procedure. This study presents further evidence of the value of and ongoing need for total joint registries. Cemented total knee arthroplasty with all-polyethylene tibia and with metal-backed tibia showed more than 95% 10-year cumulative survival. Hybrid total knee arthroplasty, ingrowth total knee arthroplasty, and unicondylar knee arthroplasties did not show such good results.

Total knee arthroplasty using cruciate-retaining kinematic condylar prosthesis.

The purpose of the current study was to evaluate the long-term results of the Kinematic I condylar prosthesis with retention of the posterior cruciate ligament. One hundred sixty-eight total knee arthroplasties in 118 patients (mean age, 65.2 years; range, 21-88 years) were inserted with cement, an all-polyethylene patella, metal-backed tibia, and posterior cruciate ligament retention. Sixty-one patients (86 knees) died, one patient had an above-knee amputation, and three patients (five knees) were lost to followup; therefore, 66 knees (excluding revisions) in 50 patients were available for followup at a mean of 15.7 +/- 1.1 years (range, 14-20 years). Of the entire cohort of 168 knees, 13 have been revised: one for medial femoral condyle fracture, one for tibiofemoral instability, one for femoral and two for tibial component aseptic loosening, four for tibial polyethylene wear, and four for patellar component aseptic loosening. The 15-year survivorship free of any component revision excluding infections was 88.7% (confidence interval, 82%-95%). The 15-year survivorship free of radiographic loosening and/or revision of any component was 85.1% (confidence interval, 78%-92%). The current study shows good function and survivorship of the posterior cruciate-sparing Kinematic I condylar prosthesis at a mean of 15.7 +/- 1.1 years.

A Randomized Comparison of All-Polyethylene and Metal-Backed Tibial Components

Clinical failures of all-polyethylene tibial components in total knee arthroplasty generally have been failures of design, not materials. The current study was designed to compare a modern congruent all-polyethylene tibial component with a metal-backed tibial component with the same articular design and geometry. All patients older than 60 years of age requiring total knee arthroplasty were randomized prospectively to receive either a cemented posterior cruciate ligament-retaining all-polyethylene component or a metal-backed tibial component with identical articular surfaces. All patients received identical cemented femoral and all-polyethylene patellar implants. The mean age of the patients was 69 years, and the mean American Society of Anesthesiology score was 3. The diagnosis was osteoarthritis in 92% of this population. Three hundred twenty-four total knee arthroplasties in 296 patients were performed; 213 joints (111 all-polyethylene tibias and 102 metal-backed tibias) with a minimum of 3 years followup (mean, 49 months) are reported. The preoperative Knee Society knee score in the group of patients who received an all-polyethylene tibial component was 38 points, improving to 84 points at latest followup, whereas in the group of patients who received a metal-backed tibial component, the score improved from 35 to 85 points. Functional scores increased from preoperative values of 56 to 74 points in the patients who received all-polyethylene tibial components, and 57 to 72 points in the patients who received metal-backed tibial components. Range of motion measured at latest followup averaged 106 degrees in patients who received an all-polyethylene tibial component and 107 degrees in the patients who received a metal-backed component, and postoperative tibiofemoral alignment averaged 6 degrees valgus for both groups. There were 13 reoperations for instability, patellofemoral problems, or deep infection, but none for aseptic loosening or wear in either group. These differences were not statistically significant, nor were any measures of patient satisfaction or clinical outcome between the two groups in this period. Total knee arthroplasty with a well-designed, contemporary congruent all-polyethylene tibial component functions equivalently to its metal-backed tibial counterpart at 3- to 5-year followup in this patient population, and is less costly ($675).

Mechanisms of failure of the femoral and tibial components in total knee arthroplasty.

From 1974 to 1986, 1430 cemented primary total knee arthroplasties were available for analysis. These included 224 total condylar prostheses with a polyethylene tibial component, 289 posterior stabilized prostheses with a polyethylene tibial component, and 917 posterior stabilized prostheses with a metal-backed tibial component. There were 12 failures in the total condylar series including three infections (one early and two late), five loose tibial components, two loose femoral and tibial components, and two unstable arthroplasties. The posterior stabilized prosthesis with the polyethylene tibia demonstrated six failures including two loose tibial components, two loose femoral components, and one supracondylar femur fracture. The posterior stabilized prosthesis with the metal-backed tibial component was associated with seven failures including six infections (three early and three late) and one femoral loosening. No metal-backed tibial components have been revised for loosening. The overall failure rate in this series was 1.7% for all prostheses. The incidence of tibial loosening was 0.53% with an average time to failure of 4.7 years. The incidence of femoral loosening was 0.35% with an average time to failure of 2.0 years. Tibial loosening was related to error in technique: postoperative varus tibiofemoral alignment, varus tibial component position, and excessive tibial resection. The overall infection rate was 0.63% for all total knee arthroplasties, and all were secondary to gram-positive organisms. Presently, the posterior stabilized prosthesis with a metal-backed tibia is the authors' implant of choice. Technical error and infection are the major causes of failure.

Failure analysis of PCA revision total knee replacement tibial component. A preliminary study using the finite element method.

This report documents the results of a finite element method (FEM) "worst-case" failure analysis of a stemmed, porous-coated tibial revision component that was designed with "slots" to aid in removal. A three-dimensional FEM model of a metal-backed tibial component was subjected to expected peak loads while being restrained at the stem and unsupported under the plateaus. Stresses in the prosthesis plateau adjacent to the stem were found to exceed yield stress in many areas, and to exceed the expected endurance limit in large areas. We conclude that a stemmed prosthesis with slots is flawed and may be expected to fail if implanted without adequate support for the prosthesis plateau. The long-term effects of bone remodeling may further jeopardize the integrity of this prosthesis. We recommend that this prosthesis not be used in its present design.