An Animal Model of Bone Grafting Procedure for Anterior Shoulder Instability and Strategies for Accelerating Graft Healing

BACKGROUND: Bone grafting is a common and effective treatment for anterior shoulder instability. Graft healing is critical for the success of this procedure; however, few studies have investigated methods to enhance the healing process. Furthermore, suitable animal models are scarce for this type of surgery. PURPOSE: To (1) establish an animal model of anterior shoulder instability, and (2) evaluate whether a surgical modification based on an inlay structure (creating a groove on the glenoid and shaping the graft to match it) along with postoperative administration of the bone anabolic agent parathyroid hormone 1-34 (PTH1-34) could accelerate graft healing. STUDY DESIGN: Controlled laboratory study. METHODS: A rabbit model of anterior shoulder instability was established, and autologous iliac bone grafting was performed. Gross morphological observation, micro-computed tomography imaging and analysis, and histological staining and evaluation were employed to assess whether the inlay-based surgical modification and postoperative intermittent subcutaneous injection of PTH1-34 could enhance graft healing. RESULTS: The modified inlay technique increased the expression of Runx2 and type I collagen within the graft, accelerated graft integration with the glenoid, promoted more rapid callus remodeling and maturation, and reduced graft resorption. Additionally, for both the modified inlay and classic onlay bone grafting procedures, postoperative intermittent subcutaneous injection of PTH1-34 enhanced osteogenic capacity of the autograft and glenoid, increased new bone volume, and shortened the graft healing time. CONCLUSION: We successfully developed an animal model of autologous bone grafting for anterior shoulder instability. Using this model, we demonstrated that the modified inlay bone grafting procedure improves osteogenic ability, shortens healing time, and promotes callus maturation. Intermittent subcutaneous administration of PTH1-34 after surgery further enhanced graft-glenoid healing. CLINICAL RELEVANCE: The modified inlay technique and postoperative intermittent PTH1-34 administration may improve graft healing rates after bone grafting procedures for anterior shoulder instability.