Summary

In patients that underwent a minimum of 6-months of nonoperative management for isolated posterior glenohumeral instability, failure occurred approximately 47% of the time and was associated with a greater posterior humeral head subluxation, less posterior acromial coverage, greater posterior acromial height, and greater amounts of glenoid retroversion on index MRI than those who did not fail.

Abstract

Background

Nonoperative management of posterior shoulder instability is common, however there is limited data available to assess the pathomorphologic factors associated with failure of nonoperative treatment. Having a better understanding of the natural history of posterior glenohumeral instability as well as insight into specific morphology that is associated with poor survivorship of nonoperative management can play a key role in patient counseling and guide management.

Purpose

The purpose of this study is to determine what, if any, glenohumeral pathomorphology may predispose patients to fail nonoperative management.

Study Design: Retrospective Cohort Study

Methods

We conducted a retrospective review of a consecutive series of patient with isolated posterior shoulder instability, defined as isolated posterior labral tear on MRI with corresponding physical exam findings (Kim and Jerk tests), had undergone nonoperative management for a period of 6 months and did not have any past surgical history with respect to the affected shoulder. Our primary outcome was risk factors for failure of non-operative management including posterior glenoid bone loss (pGBL), glenoid version, acromial morphology and posterior humeral head subluxation. Cox proportional hazard analysis was used to evaluate risk factors for failure.

Results

42/90 (46.7%) patients failed a 6-month trial of nonoperative management and went onto receive an arthroscopic stabilization procedure. The failure group demonstrated a significantly greater humeral head subluxation ratio than the cohort of patients who survived nonoperative management (0.65 +/- 0.2 vs 0.62 +/- 0.2; p = 0.0375). Cox proportional haxard analysis identified glenoid bone loss, greater posterior acromial height, less posterior acromial coverage, and posterior humeral subluxation as significant risk factors for failure of nonoperative management. Of those who failed nonoperative management 17 had repeat MRI’s for comparison, demonstrating a statistically significant progression of pGBL (index MRI 2.68% +/- 1.71 verses after nonoperative treatment 6.54 % +/- 1.59 vs; p = 0.00274).

Conclusion

In patients that underwent 6-months of nonoperative management for isolated posterior glenohumeral instability, failure occurred approximately 47% of the time and was associated with a greater posterior humeral head subluxation, less posterior acromial coverage, greater posterior acromial height, and greater amounts of glenoid retroversion on index MRI than those who did not fail. Additionally, those who had repeat MRI on average 1.3 years later demonstrated greater glenoid bone loss when compared to the index MRI. The findings of this study suggest that a trial of nonoperative management as a first line treatment for all isolated posterior instability patients might not be as conservative or risk free as once thought.