Contribution of osseous and muscular stabilizing effects with the Latarjet procedure for anterior instability without glenoid bone loss.

BACKGROUND: The Latarjet procedure is used to treat anterior shoulder instability. Authors contend that the main concept of the operation is using the conjoined tendon as a sling to lower the subscapularis, reinforcing the anteroinferior capsule. The effects of the "sling," as well as stability and range of motion (ROM), after the Latarjet procedure have not been documented. In this study, we test the Latarjet procedure, attempting to account for the effect of the conjoined tendon. We also use the model to characterize the kinematic effects and stabilizing mechanism of the Latarjet procedure. MATERIALS AND METHODS: Six cadaveric shoulders were tested in the intact state, after anterior capsulotomy, and after the Latarjet procedure. An apparatus was designed that allowed for loading of the conjoined tendon. ROM and translation were quantified. After conclusion of testing in the Latarjet group, the conjoined tendon was released and specimens were retested to determine stability attributable to the sling effect versus the osseous effect alone. RESULTS: We found no statistically significant differences with regard to ROM after the Latarjet procedure. The Latarjet procedure did significantly decrease anteroinferior translation. However, when the conjoined tendon was unloaded, there was a significantly decreased resistance to anterior translation. After conjoined tendon release, there was no effect on inferior translation. CONCLUSION: This study confirmed that the Latarjet procedure successfully decreases anteroinferior translation while maintaining ROM. It did not support the belief that inferior stability is provided by the sling effect. The model developed can serve as the basis for future testing. LEVEL OF EVIDENCE: basic science study, biomechanics.