The Effect of Glenoid Version and Width on Outcomes of Arthroscopic Posterior Shoulder Stabilization

Abstract

Objectives:Posterior shoulder instability has become more widely recognized and recent studies have demonstrated improved outcomes with arthroscopic treatment. Chondrolabral version has been postulated to be an important contributor to posterior shoulder stability. Further, while glenoid bone loss has been shown to be an important predictor of the outcomes of anterior shoulder stabilizations, the effect of glenoid shape and size is less clear in the setting of posterior instability. We hypothesized that anatomical variations of the glenoid, specifically in its size and version, affect the patient outcomes following arthroscopic posterior shoulder stabilization.Methods:Two-hundred athletes were prospectively followed after undergoing an arthroscopic repair of unidirectional posterior instability by a single surgeon. They were followed for a mean of 24 months post-operatively, and outcome measures included the ASES and standardized pain, function, and stability scores. MRI arthrogram measurements of the glenoid were performed on an axial image at the inferior one-third level. They included measurements of labral, chondral, and glenoid bone version and glenoid and labral width. Simple linear regressions were performed to determine relationships between MRI measurements and outcome scores.Results:One-hundred eighteen MRI arthrograms were performed at our institution and were available for review. Glenoid bone width and bone version both predicted pre-operative pain and ASES scores, with patients with wider (slope 1.3, p<.05) and more retroverted glenoids (slope.94, p<.05) having better average pre-operative pain and ASES scores than subjects with smaller and more anteverted glenoids. At final post-operative follow-up, no significant differences in outcome scores were detected among subjects with regard to glenoid bone version. However, patients with wider glenoids continued to have better pain and ASES scores (slope 1.0, p<.05). There was no correlation between chondral and labral version and any outcome measure pre-operatively or post-operatively.Conclusion:Glenoid anatomy may play an important role in the outcomes of patients undergoing arthroscopic stabilization of posterior capsulolabral injuries. While decreased glenoid retroversion and bony width both portended lower shoulder function pre-operatively, only decreased bony width was predictive of poorer outcomes postoperatively. Patients with posterior shoulder instability and a smaller glenoid width identified on MRI may warrant further investigation of glenoid bone morphology by CT scan. Further investigation of the effect of glenoid, chondral, and labral version and glenoid width on posterior shoulder stability and outcomes following posterior shoulder stabilization is warranted.