Comparison of Poly-L-Lactide and Polylactide Carbonate Interference Screws in an Ovine Anterior Cruciate Ligament Reconstruction Model

Purpose: The purpose of this study was to compare polylactide carbonate (PLC) interference screws with poly-L-lactide (PLLA) screws in an ovine anterior cruciate ligament reconstruction model. Methods: A PLC screw or PLLA screw was placed in the center of a 4-strand soft-tissue autograft fixating the graft within the tibial tunnel. Assessments were made at 6 and 12 weeks for fixation strength and at time points of 6, 12, 26, and 52 weeks via computed tomography and histology. Results: No adverse or inflammatory reactions were noted for either material at any time point. Mechanical fixation strength increased from 6 to 12 weeks for both the PLC and PLLA screws, with no significant differences in fixation strength being found between the 2 groups. By 26 weeks, the PLC screw was partially replaced by new bone, a process that was completed by 52 weeks. The PLLA screws were intact and surrounded by a fibrous layer at 52 weeks with no obvious resorption. New bone formation within the tendon construct located in the bone tunnel proximal to the interference screw was also noted in the PLC screw group but was not observed in the PLLA group. Conclusions: This study has supported the hypothesis that this bioabsorbable composite has sufficient mechanical properties and strength retention to function successfully as an interference screw but also stimulates a biologic healing response, enabling replacement by bone and tunnel healing. Clinical Relevance: This study shows both the satisfactory mechanical characteristics and osteoconductive nature of PLC used in an interference screw in an ovine anterior cruciate ligament reconstruction model.