ObjectivesThe aim of this study is to evaluate the relationship between the achievement of clinically significant improvement in patient-reported outcome measures (PROMs) and the postoperative magnetic resonance image (MRI) appearance of matrix-associated chondrocyte implantation (MACI), in conjunction with patellofemoral realignment procedures, for the treatment of grade IV chondral defects about the patellofemoral joint. MethodsA retrospective review of patients undergoing MACI for grade IV chondral defects of the patella or trochlea by a single sports medicine fellowship-trained surgeon from 2017-2020 was performed. Concomitant realignment procedures, including tibial tubercle osteotomy and medial patellofemoral ligament reconstruction, were also performed as needed. Patients with preoperative and minimum 1-year postoperative PROMs and postoperative knee MRI were included. MRI were obtained at 6.3 [Interquartile range (IQR): 5.8, 7.5] months postoperatively. A fellowship-trained musculoskeletal radiologist assigned a Magnetic Resonance Observation of Cartilage Repair Tissue (MOCART) score (range: 0-100, with 100 equating to complete graft healing) to each MRI. Achievement of the minimal clinically important difference (MCID) for International Knee Documentation Committee (IKDC), Knee Injury and Osteoarthritis Score–Quality of Life (KOOS-QoL), and Kujala scores were determined for each patient. Paired t-tests or Wilcoxon Rank-Sum tests were used to evaluate for an association between achievement of the MCID for each PROM and MOCART scores. The average follow-up time and time from surgery to PROMs were 2.7±1.5 years and 1.7±0.66 years, respectively. ResultsThirty patients were included. There was a significant improvement in all PROMs from pre- to postoperative (p<0.001). More than two thirds of patients achieved the MCID for each PROM. Patients who achieved the MCID for IKDC had significantly higher MOCART scores (66.5±16.2) compared to those who did not meet the MCID for IKDC (50.6±23.6, p=0.043). ConclusionMACI for the treatment of patellofemoral chondral injuries is associated with clinically significant improvement in PROMs at short-term follow up. Clinically significant improvements in IKDC scores are associated with a more mature MRI appearance of the ACI graft on postoperative MRI, as indicated by higher MOCART scores. Level of EvidenceIV – Case Series