Biomechanical Evaluation of Collagen Membrane Fixation Techniques in Autologous Chondrocyte Implantation: A Comparative In Vitro Study

Background Matrix-induced autologous chondrocyte implantation (MACI) relies on secure collagen membrane fixation for successful cartilage repair. However, comparative biomechanical data on fixation techniques remain limited. Objective To evaluate and compare the fixation strength of various collagen membrane fixation techniques used in autologous chondrocyte implantation (ACI) using an in vitro porcine model. Design Fifty porcine knees were used to test 17 different fixation methods for securing collagen membranes (Chondro-Gide®). Fixation techniques included various combinations of absorbable and non-absorbable anchors, different suture materials, knotted and knotless techniques, and absorbable pins. Membrane thickness was measured using digital micrometry. Tensile testing was performed using a digital force gauge until failure. Peak fixation strength and failure modes were recorded. Results. Mean collagen membrane thickness was 0.492 ± 0.151 mm with moderate correlation to tensile strength (r = 0.554, P < 0.001). Among tested methods, the 2.0-mm absorbable pin demonstrated significantly superior fixation strength compared to all other techniques (16.67 ± 4.17 N vs. 5.54-10.01 N, P < 0.01). No significant differences were observed among various anchor-suture combinations. Failure occurred predominantly through membrane tearing at anchor insertion sites (47.1%) and suture fixation points (35.9%), rather than anchor pull-out or suture breakage. Conclusions Most conventional fixation methods showed comparable mechanical performance, limited by the inherent properties of the collagen membrane. The 2.0-mm absorbable pin achieved superior fixation through a compression-embedding mechanism rather than simple surface fixation. These findings suggest that fixation strategies incorporating membrane compression into the subchondral bone may provide enhanced mechanical stability for ACI procedures.