Biomechanical comparisons of screw fixation vs. suture button fixation for managing anterior shoulder instability with distal clavicle bone graft

Background: Screws and metal suture buttons are commonly used for graft fixation in glenoid reconstruction procedures. The distal clavicle has been proposed as an alternative autograft option. The aim of the present study was to compare the biomechanical characteristics of 2 fixation devices for securing distal clavicle graft in glenoid reconstruction surgery. Methods: Eight matched-pair, fresh-frozen human cadaveric shoulders were randomly assigned to undergo the reconstruction surgery with either screw fixation or suture button fixation. Morphometric data, including the graft dimension, glenoid surface dimension and area, and amount of restoration, were obtained. After fixation, a biomechanical test was conducted in a direct-loading scenario. The construct stiffness, cyclic displacement, and ultimate failure and displacement of each specimen were collected. Results: After reconstruction, the glenoid articular surface was restored to approximately 126 ± 10% of native status. Therefore, the distal clavicle graft was able to reconstruct 47 ± 9 % of the glenoid articular area. In terms of biomechanical results, the screw group exhibited significantly greater construct stiffness (165.0 ± 38.1 N/mm) than the button group (118.2 ± 33.9 N/mm, P = .027). Cyclic displacement was significantly greater in the button group (2.6 ± 1.0 mm) as compared with the screw group (0.8 ± 0.3 mm; P = .001). No significant difference in failure load and displacement were observed between the 2 groups. Conclusion: In a cadaveric 20%-25% anterior glenoid bone loss scenario, the distal clavicle graft is sufficient in glenoid reconstruction surgery. At time zero, the screw fixation appears to offer superior construct stiffness and greater resistance to the cyclic displacement, although these biomechanical differences may not be clinically relevant.