Physical activity levels after characterized chondrocyte implantation versus microfracture in the knee and the relationship to objective functional outcome with 2-year follow-up.

Abstract

Characterized chondrocyte implantation results in superior structural repair compared with microfracture, but may be associated with a slower recovery of physical activity levels due to the arthrotomy. Our hypotheses were that (1) microfracture results in increased activity levels over 2 years after surgery compared with characterized chondrocyte implantation, (2) patients with high preinjury activity levels have a better functional outcome, and (3) high levels of low-load activities after surgery improve functional outcome. Cohort study; Level of evidence, 2. Sixty-seven patients with local cartilage defects (mean size, 2.4 cm(2); standard deviation, 1.5 cm(2)) of the femoral condyle underwent characterized chondrocyte implantation (n = 33) or microfracture (n = 34), followed by an identical rehabilitation protocol. Activity levels (assessed using the Activity Rating Scale) and functional outcome were determined at baseline, and 1 and 2 years after surgery. Functional outcome was based on the pooled symmetry index (derived from isokinetic knee extension strength and 3 one-legged hop tests). Patients' participation in low-load activities during the first 3 months after surgery was assessed using rehabilitation data. Mixed linear model analyses and Wilcoxon rank sum tests were used. Activity levels in patients treated with characterized chondrocyte implantation and microfracture were comparable at 1 and 2 years after surgery. Preinjury activity levels showed no relationship to functional outcome. Lack of postoperative low-load activities resulted in a significantly worse functional outcome (mean pooled symmetry index 78.2%) compared with high levels of postoperative surgery low-load activities (mean pooled symmetry index 92.4%). Despite differences between the characterized chondrocyte implantation and microfracture procedures, patients' activity levels were comparable at 2 years after surgery. Lack of low-load activities after surgery adversely affected functional outcome.