Microfracture Versus Autologous Chondrocyte Implantation for Articular Cartilage Lesions in the Knee A Systematic Review of 5-Year Outcomes

Background: Microfracture (MFx) and autologous chondrocyte implantation (ACI) are 2 surgical treatment options used to treat articular cartilage injuries of the knee joint. Purpose: To compare the midterm to long-term clinical outcomes of MFx versus ACI for focal chondral defects of the knee. Study Design: Systematic review. Methods: A systematic review was performed by searching PubMed, the Cochrane Library, and Embase to locate studies (level of evidence I-III) comparing the minimum average 5-year clinical outcomes of patients undergoing MFx versus ACI. Search terms used were "knee,'' "microfracture,'' "autologous chondrocyte implantation,'' and "autologous chondrocyte transplantation.'' Patients were evaluated based on treatment failure rates, magnetic resonance imaging, and patient-reported outcome scores (Lysholm, Knee Injury and Osteoarthritis Outcome Score [KOOS], and Tegner scores). Results: Five studies (3 level I evidence, 2 level II evidence) were identified that met the inclusion criteria, including a total of 210 patients (211 lesions) undergoing MFx and 189 patients (189 lesions) undergoing ACI. The average follow-up among all studies was 7.0 years. Four studies utilized first-generation, periosteum-based ACI (P-ACI), and 1 study utilized third-generation, matrix-associated ACI (M-ACI). Treatment failure occurred in 18.5% of patients undergoing ACI and 17.1% of patients undergoing MFx (P=.70). Lysholm and KOOS scores were found to improve for both groups across studies, without a significant difference in improvement between the groups. The only significant difference in patient-reported outcome scores was found in the 1 study using M-ACI in which Tegner scores improved to a significantly greater extent in the ACI group compared with the MFx group (P=.003). Conclusion: Patients undergoing MFx or first/third-generation ACI for articular cartilage lesions in the knee can be expected to experience improvement in clinical outcomes at midterm to long-term follow-up without any significant difference between the groups.