Unicompartmental knee arthroplasty is effective: ten year results

Unicompartmental knee arthroplasty (UKA) presents low morbidity and complication risk and provides excellent outcomes and fast recovery. Despite these facts, knee-replacement registries have shown high failure rates for UKA, especially when compared with traditional TKA. The purpose of this study was therefore to report outcomes, complications, and ten year survivorship rate of medial ZUK unicompartmental knee prosthesis.

We retrospectively analysed 136 medial UKAs in 124 patients, with a maximum follow-up of ten years. Patients were assessed through the International Knee Society (IKS) scores and range of motion (ROM). A complete X-ray study was performed in all patients. Limb alignment was assessed by measuring the femorotibial mechanical alignment. At surgery, bone resections were performed according to proximal tibial epiphyseal axis.

Mean IKS knee score improved from 45.7 (range 35-63) points preoperatively to 87.2 (range 71-100) points at the latest follow-up. Mean IKS function score improved from 50.9 (range 40-70) points to 89.1 (range 75-100) points (p < 0.05). Mean ROM increased from 106.1° (range 98-123°) to 128.6° (range 116-139°) (p < 0.01). Four cases (2.9 %) were revised due to failure for any cause, so that survivorship was 97.1 % at the latest follow-up.

This study demonstrates excellent outcomes and survivorship for the ZUK unicompartmental knee prosthesis. Based on our findings, we believe that the ZUK prosthesis offers an effective and durable solution for treating medial degeneration of the knee. Level of Evidence IV - Retrospective case series study.