Long-Term Survivorship and Clinical Outcomes of a Single Radius Total Knee Arthroplasty.

INTRODUCTION: To ensure the continued success of total knee arthroplasties (TKAs), we must employ ever-evolving modifications to our techniques and implant designs. As part of this process, a knee prosthesis with a single radius (SR) has been developed to more precisely emulate the anatomy and biomechanics of the native knee, but there is little data on long-term outcomes. Therefore, the purpose of this study was to evaluate (1) the long-term (10-year) survivorship; (2) clinical and patient-reported outcomes; (3) radiographic outcomes; and (4) incidence of complications in patients who underwent TKA with this SR prosthesis.

MATERIALS AND METHODS: We evaluated 54 patients (67 TKAs) (24% men, 76% women) who had a mean age of 62 years at the time of surgery (range, 30 to 82 years). The mean follow-up was 10 years (minimum 9 years). All patients underwent a primary TKA using a newly developed single radius implant with posterior condylar flare. Kaplan-Meier analysis was performed to determine implant survivorship. The Knee Society Score (KSS), University of California Los Angeles (UCLA) activity scale, and Short Form-36 (SF-36) mental and physical component scores were used to evaluate clinical and patient-reported outcomes. Anteroposterior and lateral radiographs were reviewed for evidence of component loosening. Complications were identified through a comprehensive chart review and were classified as either surgical or medical.

RESULTS: Assessment of aseptic loosening revealed that survivorship of the tibial and femoral components was 100%. Evaluation of revisions for any reason showed that Kaplan-Meier aseptic and all-cause survivorship of the femoral and tibial components was 99%. When only polyethylene exchanges were included, the all-cause overall and aseptic survivorships were 94% and 96% respectively. Additionally, the mean KSS and UCLA activity scores were 64 (range, 5 to 100 points) and 5 points (range, 1 to 9 points) at final follow-up. The mean SF-36 mental and physical component scores were 53 (range, 23 to 66 points) and 39 points (range, 15 to 61 points). Surgical complications included arthrofibrosis, extensor mechanism disruption, patellar component revision, and peroneal nerve palsy. No medical complications were reported.

CONCLUSION: Single radius total knee arthroplasties have demonstrated excellent long-term survivorship and functional outcomes, as demonstrated by this preliminary report.