Chondral Defect Repair after the Microfracture Procedure

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Abstract
Background: The extent and time course of chondral defect healing after microfracture in humans are not well described. Although most physicians recommend a period of activity and weightbearing restriction to protect the healing cartilage, there are limited data on which to base decisions regarding the duration of such restrictions. Hypothesis: Evaluation of the status of chondral defect repair at different time points after microfracture in a primate model may provide a rationale for postoperative activity recommendations. Study Design: Descriptive laboratory study. Methods: Full-thickness chondral defects created on the femoral condyles and trochlea of 12 cynomolgus macaques were treated with microfracture and evaluated by gross and histologic examination at 6 and 12 weeks. Results: At 6 weeks, there was limited chondral repair and ongoing resorption of subchondral bone. By 12 weeks, the defects were completely filled and showed more mature cartilage and bone repair. Conclusion: In the primate animal model, significant improvements in the extent and quality of cartilage repair were observed from the 6- to 12-week time points after microfracture. Clinical Relevance: The poor status of the defect repair at 6 weeks and the ongoing healing observed from the 6- to 12-week time points may indicate that the repair is vulnerable during this initial postoperative period. Assuming the goal of postoperative weightbearing and activity restriction in patients after microfracture is to protect immature repair tissue, this study lends support to extending such recommendations longer than 6 weeks.