Reoperative characteristics after microfracture of knee cartilage lesions in 454 patients.

PURPOSE: There is only limited information on those patients who fail following microfracture treatment at the knee joint. Evaluation was made of factors associated with treatment failure and clinical outcome assessment among this collective.
METHODS: The study included a total of 560 patients who had previously undergone microfracture for the treatment of symptomatic knee joint cartilage lesions. For the remainder of this study, inclusion criteria were patients that underwent reoperation at the initially operated knee joint (index knee) due to symptoms related to the primary site of microfracture intervention (failure patients) with a minimum postoperative follow-up of 2 years. The remaining cohort of patients served as internal control (non-failure patients). Chart reviews were performed to identify patient and defect characteristics. Patients were evaluated for postoperative Lysholm knee scores, Tegner activity scale, as well as preoperative and postoperative numeric analogue scales (NAS) for function and pain (10 = highest possible function, no pain).
RESULTS: A total of 454/560 (81.1 %) subjects were completely evaluated. Overall, 123/454 patients (26.9 %) (age at operation 43.9 ± 14.1 years, 56 female, BMI 25.8 ± 3.6, 30 smokers, 61.1 ± 68.3 month symptom duration, postoperative follow-up 5.0 ± 2.1) met the inclusion criteria. The postoperative Lysholm score was 63.0 ± 24.6 and the Tegner score was 4.0; NAS function improved from 2.8 ± 1.8 to 4.8 ± 2.2 (P < 0.001), and NAS pain improved from 3.2 ± 2.1 to 5.0 ± 2.4 (P < 0.001). Exclusively, the overall defect size/knee joint was smaller (P = 0.006), postoperative follow-up was longer (P = 0.002), and existense of previous surgery (77.2 vs. 51.6 %, P < 0.001) was more frequent in failure subjects when comparing to non-failure patients (n = 331). The overall clinical outcome among failure subjects was significantly worse when comparing to non-failure subjects. Regression analysis identified that lower preoperative NAS values, being a smoker, and patello-femoral lesions were associated with a higher probability of reoperation.
CONCLUSION: Within the collective presented here, microfracturing was associated with a high frequency of reoperation. Clinical outcome is worse when compared with that of patients without reoperation. Specific parameters can be identified that increase the eventuality of failure following microfracture treatment. LEVEL OF EVIDENCE: IV.