Mid-term performance of a unicompartmental knee prosthesis

The objective of this study was to report midterm patient-reported outcomes (PROs) and survivorship of the Medacta MOTO Medial® Unicompartmental prosthesis (Medacta International, Castel San Petro, Switzerland) and surgical technique.

This prospective, multicentre study included 207 adults aged 43-85. Of these, 170 reached 2-year and 90 reached 5-year follow-up. PROs included the forgotten joint score (FJS), Oxford knee score (OKS) and knee injury and osteoarthritis outcome score (KOOS) subscales: Pain, Symptoms, ADL, Sport and QOL. Stress radiographs were divided into three types, quantifying the amount of medial space opening and deformity correction. Data were collected at preoperative, intraoperative, 4 weeks, 6 months, 1-year, 2-year and 5-year. Complications, revisions and Kaplan-Meier survivorship were analysed.

All PROs showed statistically significant improvements starting at 6 months and maintained through 5-year. Pre-operative standing full-length x-rays, averaged 6.5° varus. The average change in mechanical axis was less than 1° at 5-year. No difference in PROs was found between patients with (N = 63) and without (N = 27) radiolucencies. Only two cases with radiolucencies progressed to revision. There was one superficial infection and four revisions to the total knee arthroplasty. No thromboembolic, instability or arthrofibrosis complications occurred. Kaplan-Meier survivorship was 98.5% at 2-year and 98.1% at 5-year.

Unicompartmental knee replacement with implant system that allows surgical flexibility and independent balancing is a surgical option with promise of excellent functional outcomes, low complication rates and high survivorship (98.1% at 5-year). These results challenge previous studies indicating high revision rates and support the utilisation of unicompartmental arthroplasty for properly indicated patients.

Level II, prognostic studies.