The unicompartmental knee implant UniSpacer™: Ten-year outcomes after treatment for medial tibio-femoral osteoarthritis.

Background: UniSpacer™ type implants were part of the therapeutic armamentarium for medial tibio-femoral osteoarthritis before they were taken off the market in 2011. UniSpacer™ is a mobile interpositional self-centring implant that replicates the shape of the meniscus. It requires no bone cuts or component fixation. The objective of this follow-up note is to provide data on the 10-year outcomes in a cohort investigated previously in a study published in 2011. This study provides a re-evaluation of implant survival 5 years after the first analysis, as well as information on patient satisfaction and functional outcomes.

Hypothesis: UniSpacer™ survival remains stable after 5 additional years and provides satisfactory functional outcomes.

Material And Methods: We included the same patients operated on from 2003 to 2009, namely, with 17 UniSpacer™ implants in 16 patients. The operative technique was the same in all patients. At last follow-up, the patients attended a visit designed specifically to allow a clinical evaluation (IKS score, revision, forgotten implant) and new radiographic imaging of the treated knee.

Results: Mean follow-up of this retrospective study of a prospective database was 118±25 months. Of the 17 implants, 9 (53%), in 8 patients, were still in place. Six (37.5%) patients underwent early revision arthroplasty (between 6 months and 4 years). One patient was lost to follow-up and another had died. The mean global IKS knee score was 76±15 and the mean IKS function score was 80±25. The global IKS score at last follow-up was 157±39. Mean range of flexion was 119±20°. Of the 8 patients (9 implants) who still had their implants at last follow-up, 5 (56%) reported forgetting their implant. No revisions were performed between 4 and 10 years of follow-up.

Discussion: The ten-year survival was limited (53%). Clinical outcomes were satisfactory in the patients who still had their implants. The low cost and simplicity of insertion may make this implant a reasonable alternative for patients with contraindications to very major surgery.

Level Of Evidence: IV.