Third‐Generation Autologous Chondrocyte Implantation (Cells Cultured Within Collagen Membrane) Is Superior to Microfracture for Focal Chondral Defects of the Knee Joint: Systematic Review and Meta‐analysis

Purpose To systematically review randomized controlled trials to compare clinical outcomes of microfracture (MFx) versus third‐generation autologous chondrocyte implantation (ACI) for the treatment of focal chondral defects (FCDs) of the knee joint. Methods A systematic review was performed by searching PubMed, Cochrane Library, and EMBASE to locate randomized controlled trials comparing minimum 2‐year clinical outcomes of patients undergoing MFx versus third‐generation ACI for FCDs of the knee joint. The search terms used were: “knee” AND “microfracture” AND “autologous chondrocyte” AND “randomized.” Patients were evaluated based on treatment failure rates, magnetic resonance imaging, International Cartilage Repair Society scores, and patient‐reported outcome scores (Lysholm, Tegner, Knee Injury and Osteoarthritis Outcome Score, modified Cincinnati Knee Rating System, 12‐item Short Form Health Survey Physical and Mental, and the EuroQol 5 Dimensions Visual Analog Scale score). Results Six studies (5 Level I, 1 Level II) met inclusion criteria, including a total of 238 patients undergoing MFx and 274 undergoing ACI. Two studies had an overlapping cohort of patients and therefore the study with longer follow‐up was used in all analyses. The average follow‐up among patients ranged from 2.0 years to 6.0 years. Average lesion size ranged from 1.8 cm 2 to 5.0 cm 2 . Treatment failure ranged from 0% to 1.8% in the ACI group and 2.5% to 8.3% in the MFx group. In 4 studies, ACI patients demonstrated significantly greater improvement in multiple Knee Injury and Osteoarthritis Outcome Score subscores compared with MFx. In 2 studies, patients who received ACI demonstrated significantly greater improvement in the Tegner score compared to MFx, and 1 study showed significantly greater improvement in the Lysholm and ICRS scores for ACI compared with MFx. Conclusions At short‐term follow‐up, third‐generation ACI demonstrates a lower failure rate and greater improvement in patient‐reported outcomes compared with MFx for FCDs of the knee joint. Level of Evidence II, systematic review of Levels I‐II studies.