Patellofemoral Joint Chondral Defects Treated With Third-Generation Matrix-Induced Autologous Chondrocyte Implantation on Porcine Collagen Membrane: Minimum 2-Year Follow-up

Background: Third-generation autologous chondrocyte implantation (ACI), also known as matrix-induced ACI (MACI), was approved for clinical practice in December 2016. Studies specifically investigating outcomes of MACI for complex patellofemoral chondral lesions are limited. Purpose: To report patient-reported outcome measures (PROMs), complications, and failure rates after MACI for patellofemoral chondral defects at a minimum follow-up of 2 years. Study Design: Case series; Level of evidence, 4. Methods: For this retrospective review of prospectively collected data, the authors identified patients who underwent treatment with MACI for focal chondral defects in the knee between August 2017 and September 2020. PROMs, including International Knee Documentation Committee (IKDC) score, Kujala score for patellofemoral disorders, and the Veterans RAND 12-item Health Survey (VR-12) score, were obtained preoperatively and a minimum of 2 years postoperatively. The percentage of patients who met the minimal clinically important difference (MCID) for each PROM was reported. Failure was defined as (1) graft failure on follow-up magnetic resonance imaging or second-look arthroscopy, (2) revision MACI or other chondral procedure, or (3) conversion to unicompartmental or total knee arthroplasty. Results: A total of 50 patients (34 female; mean age, 32.43 +/- 7.33 years; mean follow-up, 2.71 +/- 0.79 years) remained after application of the exclusion criteria. There was a significant increase in all PROMs from preoperatively to postoperatively, including the IKDC (43.39 vs 68.58; P < .001), Kujala (58.93 vs 77.07; P < .001), VR-12 Mental (53.12 vs 57.90; P = .002), and VR-12 Physical (40.40 vs 49.89; P < .001) scores, with 5 (10%) failures. The MCID was achieved by 77.8% of patients in IKDC score and 69.0% in the Kujala score. Kaplan-Meier survival analysis showed survival probabilities of 98.0%, 96.0%, and 85.7% at 1, 2, and 4 years, respectively. MACI for patellofemoral bipolar lesions (n = 11) showed significant improvement in IKDC (50.06 vs 74.07; P = .008) and Kujala (69.33 vs 84.33; P = .046) scores, and 2 (18.2%) failures. Kaplan-Meier survival analysis with log-rank test demonstrated no significant differences in survival distributions between unipolar and bipolar patellofemoral lesions (P = .387). Conclusions: Third-generation ACI (MACI) is a successful and effective treatment method for difficult-to-treat patellar, trochlear, and bipolar patellofemoral chondral defects.