Anterior Cruciate Ligament Reconstruction in a Translational Model in Sheep Using Bio- Integrative Mineral Fiber-Reinforced Screws

Abstract

Anterior cruciate ligament reconstruction (ACLR) is one of the more common procedures performed worldwide and perhaps the most widely studied construct in orthopedic literature. Interference screws are reliable and frequently used for ligament reconstruction, providing rigid fixation and facilitates graft incorporation allowing for the physiologic loads of early rehabilitation. The purpose of this study was to determine the bio-integration profile of mineral fiber-reinforced screws and evaluate the quality of soft tissue fixation. Nine sheep underwent ACLR using harvested autologous tendon graft fixated with 4.75mm screws made of continuous mineral fibers. Histopathology and imaging evaluation at 28, 52, 104, 132-weeks (W) demonstrated mesenchymal tissue ingrowth into the implant wall at 28W, which increased at 52W and peaked at 104W. At 132W, implants were fully replaced by newly remodeled bone. Graft cellularity was evident at 28W and continued to increase through 132W as the tendon ossified sites of bone contact. Pro-healing M2 macrophages and giant cells remained infrequent, with minor increases between 52W and 104W, attributed to expected phagocytic response. Pro-inflammatory cells (i.e., M1 macrophages, polymorphonuclears) were absent through the entire study course. In conclusion, bio-integrative screws provide secure soft tissue fixation with replacement by bone demonstrating graft cellularization over time.