UniCAP offers a long term treatment for middle-aged patients, who are not revised within the first 9 years.

PURPOSE: The aim of this study was to investigate the long-term outcome of the unicompartmental knee resurfacing prosthesis (UniCAP) using clinical and radiographic assessments, and to evaluate the revision and survival rates.

METHODS: This was a prospective cohort study of patients with UniCAP prostheses with 6-9 years of follow-up. The clinical examination included the Knee Society Score (KSS) and Visual Analogue Scale (VAS) score. The radiographic examination included the Kellgren-Lawrence (KL) grading scale. A comparison analysis of the clinical preoperative and follow-up data and a Kaplan-Meier survival analysis were performed.

RESULTS: Of the 64 UniCAP patients, 36 (56%) were revised and one died. Examinations were performed on 23 (85%) of them. When compared with the preoperative data, the examinations showed a significant increase in the KSS objective [mean = 47.4, standard deviation (SD) = 5.8 vs. mean = 90.0, SD = 6.9] and function (mean = 46.7, SD = 6.8 vs. mean = 91.1, SD = 6.9) scores, a decrease in the VAS-score (mean = 7.3, SD = 0.5 vs. mean = 3.4, SD = 1.4) and a significant increase in the KL medial score (mean = 1.7, SD = 0.6 vs. mean = 2.1, SD = 0.5). The Kaplan-Meier survival rate after 5 years indicated good long-term outcomes.

CONCLUSIONS: There was a survival rate of approximately 40% after 9 years of follow-up, but in the group of patients (35-65 years old) not eligible for a final total arthroplasty. These patients were often left with pain and disability. This implant can be a temporary or even long-term treatment because it improved the disability and function over the long-term without a major progression in the osteoarthritis, function or pain. Long term results of this mini-prosthesis have not been previously reported.

LEVEL OF EVIDENCE: IV.