Comprehensive safety profile of polymer based matrix-associated autologous cartilage repair in the knee – A retrospective study

Introduction: Autologous Chondrocyte Implantation (ACI) has a 30-year history of treating cartilage defects >2 cm2 that extend to the underlying bone or exceed 50 % of the cartilage depth. Matrix-induced Autologous Chondrocyte Implantation (M-ACI) is now widely used to treat cartilage injuries, overcoming the limitations of standard ACI. Despite numerous studies on M-ACI efficacy, a comprehensive evaluation of its safety profile is lacking. Methods: A retrospective study was conducted on 138 patients selected from a total of 168 patients, who were administrated with a polymer-based M-ACI (BioSeed®-C; BioTissue Technologies GmbH, Germany) with a mean follow-up of 3 years (7–112 months) for safety. Results: The study revealed a 24.6 % rate of complications. Complications after biopsy were vein thrombosis in one patient and hemarthrosis in three patients. Complications related to M-ACI (4.3 %) included incomplete horizontal defect filling (n = 2), surface inhomogeneity (n = 1), partial delamination (n = 1), mild hypertrophy (n = 1) or problems with the fixation material (n = 1). Hemarthrosis and arthrofibrosis incidents have the highest rates (5.1–5.8 %). Re-operation rate after biopsy/implantation was 17.4 % with a failure rate of 1.4 % due to joint infection. Effectiveness was assessed in 19 patients using KOOS (Knee injury and Osteoarthritis Outcome Score). At 18 months, KOOS scores significantly improved and 77.7 % of the patients were responders, defined by an improvement of >10 points on KOOS. MRI scans showed complete defect filling and full integration into adjacent cartilage in 82.4 % of patients, with an average MOCART 2.0 score of 76.2. Conclusion: Complication and re-operation rates were lower compared to those of first and second-generation ACI and were comparable to other M-ACI procedures. Notable complications, such as arthrofibrosis and hemarthrosis, are most likely the result of concurrent treatments in patients. However, hemarthrosis, as a post-op MACI complication, cannot be excluded.