NexGen® LPS mobile bearing total knee arthroplasty: 10-year results

PURPOSE: Mobile bearing (MB) knee prostheses were designed to improve the performances of the total knee arthroplasties (TKA). The clinical superiority of MB prosthesis compared to its fixed bearing counterpart has remained elusive. This study prospectively evaluates the cumulative survivorship, clinical, radiographic results, and complications of a large series of MB TKAs in relation to patient age, sex, severity of arthritis, and patellar resurfacing. METHODS: This study evaluates the 5- to 10-year cumulative survival rate of the NexGen® LPS MB. Between 2000 and 2005, we performed a consecutive series of 332 MB, posterior-stabilized TKA in 249 patients (mean age 71.2 years, SD 6.9). The implants were clinically evaluated with the Hospital Special Surgery Knee Score (HSS-KS) and radiographically with the Knee Society Roentgenographic Evaluation System (KS-RES). The mean follow-up was 76.3 months (minimum 5 years). RESULTS: The HSS-KS improved from 55 pre-operatively to 86 at the end of follow-up. According to the KS-RES, the implants were anatomically aligned and progressive radiolucent lines appeared in four knees (1.2 %). The patella was selectively resurfaced in 162 of 332 knees. Patients with the patella resurfaced had better clinical results compared to those not resurfaced, but there was no difference in terms of survival. The cumulative survival rate was 98.4 % at 10 years (Kaplan-Meier's analysis). CONCLUSIONS: This MB implant provided reliable and durable clinical results with a survivorship of over 98 % at 10 years, in unselected patients regardless of age, sex, severity of disease, and patellar treatment. LEVEL OF EVIDENCE: Therapeutic study, retrospective study (data collected prospectively), case series with no comparison group, Level IV.