Biomechanical evaluation of suture buttons versus cortical screws in the Latarjet-Bristow procedure: a fresh-frozen cadavers study.

Abstract

A commonly used method of fixation of the transferred coracoid in the traditional Latarjet-Bristow procedure (open or arthroscopic) is by two bicortical screws. Although mechanically effective, screw fixation is also a major source of hardware and neurologic complications. This study aimed to compare the biomechanical performances of traditional metal screws and endobuttons as fixators of the Latarjet-Bristow procedure. Nine fresh-frozen cadaveric human scapulae with the conjoined tendon attached to the coracoid process were used for the Latarjet-Bristow procedure. The specimens were randomly assigned one of two groups: fixation using two 4.5-mm cannulated partially threaded Latarjet-Bristow experience screws or fixation using a suture-button construct. Specimens were secured in a material testing machine and cyclically preconditioned from 2 to 10N at 0.1Hz for ten cycles. They were then pulled to failure at a normalized displacement rate of 400% of the measured gauge length per minute. The maximal load-to-failure, stiffness and stress were calculated using a custom script. The failure mechanism and site were recorded for each specimen. There were no significant differences in the maximal load-to-failure or other biomechanical properties of the two fixation techniques, but the failure mechanisms were unique to each one. Four specimens fixated with screws underwent graft failures (fracture) through the proximal or distal drill hole. Five specimens fixated with endobuttons underwent failure due to glenoid bone fractures. A single endobutton fixation appears to be biomechanically comparable to screw fixation in the Latarjet-Bristow procedure and provides a lower risk for graft fracture. Further studies with more numerous specimens are warranted to conclusively validate these findings.