Suspensory fixation for bone transfer procedures in shoulder instability is superior to screws in an angled construct: a biomechanical analysis.

BACKGROUND

The Latarjet procedure is a common bony augmentation procedure for anterior shoulder instability. Historically, screw fixation is used to secure the coracoid graft to the anterior glenoid surface; however, malpositioning of the graft leads to oblique screw insertion that contributes to complications. Suture buttons (SBs) are a more recent fixation technique that have not been studied alongside standard screw fixation in the context of biomechanical models of angulated fixation. This study aims to compare the biomechanical strength of single and double, screw and SB fixation at various levels of angulation.

METHODS

Testing was performed using polyurethane models from Sawbones. The graft piece was secured with screw fixation (Arthrex, Naples, FL, USA) or suspensory button (ABS Tightrope, Arthrex, Naples, FL, USA). Single or double constructs of screws and SBs were affixed at 0°, 15°, and 30° angles to the face of the glenoid component. An aluminum testing jig held the samples securely while a materials testing system applied loads. Five constructs were used for each condition and assessed load to failure testing.

RESULTS

For single fixation constructs, suspensory buttons were 60% stronger than screws at 0° ( < .001), and 52% stronger at 15° ( = .004); however, at 30°, both were comparable ( = .180). Interestingly, single suspensory button at 15° was equivalent to a single screw at 0° ( = .310). For double fixation, suspensory buttons (DT) were 32% stronger than screws at 0° ( < .001) and 35% stronger than screws at 15° ( < .001). Both double fixation methods were comparable at 30° ( = .061). Suspensory buttons at 15° and 30° were equivalent to double screws at 0 ( = .280) and 15° ( = .772), respectively.

CONCLUSION

These measurements indicate that the suspensory button has a significantly higher load to failure capacity over the screw fixation technique, perpendicularly and with up to 15° of angulation. These analyses also indicate that the suspensory button fixation offers superior strength even when positioned more obliquely than the screw fixation. Therefore, suspensory button fixation may confer more strength while offering greater margin for error when positioning the graft.