Morphometric and Biomechanical Comparison of the Scapular Spine and Coracoid Graft in Anterior Shoulder Instability

Abstract

Background: The scapular spine has been described as a relatively new bone graft alternative used in glenoid augmentation. The classic Latarjet procedure, which transfers the coracoid as a graft, is regarded as the gold standard. The comparison of these 2 techniques has not been fully reported. Purpose: To compare the anatomic and biomechanical properties of glenoid augmentation using scapular spine graft or coracoid graft. Study Design: Controlled laboratory study. Methods: The study used 20 fresh-frozen human cadaveric shoulders. A 25% anterior glenoid defect was created, and the specimens were divided randomly to receive glenoid augmentation by scapular spine or coracoid grafts. For both procedures, the grafts were secured to the glenoid defect with 2 screws. Morphometric data, including the glenoid articular area, amount of restoration, and graft dimensions, were obtained. A biomechanical test was conducted in a direct-loading scenario. The construct stiffness, cyclic displacement, and ultimate failure of each specimen were collected. Results: No significant difference was found in glenoid articular restoration between the scapular spine group and the coracoid group (31% vs 33%, respectively; P = .311). Morphometric analysis indicated that coracoid grafts exhibited significantly greater thickness and height than scapular spine grafts. In biomechanical results, the scapular spine group exhibited significantly greater construct stiffness than the coracoid group (206.3 ± 58.8 vs 148.3 ± 76.0 N/mm, respectively; P = .023). The average failure load in the scapular spine group was not significantly higher than that in the coracoid group. No significant differences in cyclic displacement were found between the 2 techniques. Conclusion: In a simulated 25% anterior glenoid bony defect, a scapular spine graft was comparable with the classic Latarjet procedure in restoring the glenoid articular dimension and exhibited superior construct stiffness in a cadaveric model. Clinical Relevance: The scapular spine may serve as an alternative graft choice in glenoid augmentation surgery considering the amount of articular restoration and initial fixation stability.