Summary

Decreased glenoid retroversion is associated with failure after anterior shoulder stabilization in the setting of subcritical bone loss.

Abstract

Introduction

Several factors, including bone loss, age, and ligamentous laxity predict failure after anterior shoulder stabilization for anterior labral tears. Decreased glenoid retroversion has been shown to be an important factor for the development of anterior shoulder instability and increased bone loss after dislocation. However, its role in predicting outcome after surgery has not been previously investigated. We hypothesized that decreased retroversion would be associated with failure of anterior stabilization in the setting of subcritical bone loss.

Methods

37 individuals who underwent primary anterior shoulder stabilization between 2007-2015 were included in the study. Subjects were excluded based on prior shoulder surgery, multidirectional instability, presence of connective tissue disorder, concomitant rotator cuff pathology, no bone loss, and greater than 20% bone loss as measured on MRI. Glenoid version was estimated by measuring the angle created between the scapular axis and the glenoid line using T1 axial MRI sequences. Cases were defined as individuals who sustained either a subluxation or dislocation event after the index procedure, while controls were defined as individuals who did not. Student t-test was used to determine differences in version, and bone loss between cases and controls. Logistic regression was used to determine independent predictors of failure after surgery.

Results

There were 18 cases and 19 controls. There were no differences in baseline demographics between groups. There was significantly more bone loss among cases (14.4%) compared to controls (9.2%, p < .001). Cases (4.8? ? 4.3?) were associated with significantly less mean retroversion compared to controls (7.6? ? 5.2?). There was weak correlation between bone loss and glenoid version (r = 0.079). Decreased retroversion was not a significant independent predictor of failure (OR = 1.22, 95% CI 0.97-1.55, p = .096). However, addition of glenoid version to glenoid bone loss significantly increased the predictivity of the logistic regression model (R2 = .34 versus .41).

Discussion

Decreased glenoid retroversion was associated with failure after anterior stabilization and was only weakly correlated with bone loss. Glenoid bone loss was strongly associated with failure. These results suggest presence of decreased retroversion may be an important determinant in predicting failure of anterior stabilization. While glenoid bone loss is often the predominant factor in predicting failure after surgery, relative anteversion may be a subtle factor that becomes important in the setting of subcritical bone loss.

Conclusion

In individuals with a Bankart lesion in the setting of subcritical bone loss, the presence of decreased glenoid retroversion may indicate higher risk for failure after anterior stabilization.