Multimodal evaluation of periosteal versus collagen membrane coverage in atelocollagen-associated autologous chondrocyte implantation for large knee cartilage defects.

Purpose: Atelocollagen-associated autologous chondrocyte implantation (A-ACI) with periosteal coverage shows favourable outcomes for large knee cartilage defects but is associated with complications such as graft hypertrophy. Collagen membrane coverage remains under-investigated in this technique. This study aimed to evaluate periosteal versus collagen membrane coverage using clinical, radiological, arthroscopic and histological assessments. Methods: Between 2014 and 2022, patients with ≥4.0 cm Results: Both groups demonstrated significant clinical improvement at 24 months without significant between-group differences. MOCART 2.0 scores were significantly higher in the collagen membrane group at 12 and 24 months (83 vs. 60 at 24 months, Conclusions: The primary clinical outcomes improved similarly in both groups at two years without meaningful between-group superiority. While collagen membrane coverage was associated with higher MOCART 2.0 scores after adjustment for concomitant osteotomy, all structural evaluations should be regarded strictly as secondary and exploratory. Level of Evidence: Level III.