Combined glenoid and humeral bone loss has been identified as an important factor in predicting recurrence after arthroscopic shoulder stabilisation. The “glenoid track” concept is proposed to predict recurrent instability by comparing the relative size of the glenoid to the humeral bone defect. The aim of this study was to investigate whether assessment of the glenoid track on a pre-operative MR arthrogram could be used to predict subsequent instability in a typical UK population.

A retrospective study was undertaken of 175 primary arthroscopic stabilisation procedures of which 82% (n=143) were men. The median age was 26 years (IQR 22 to 32, range 16 to 77). The median follow-up was 76 months (range 21 to 125). A pre-operative MR arthrogram was used to determine if the shoulder was on-track or off-track. The endpoint of recurrent dislocation was examined.

The prevalence of “off-track” bone loss in this group was 14.2% (n=25). There were 6 (24%) dislocations in the off-track group compared with 5 (3.33%) dislocations in the on-track group (RR 7.2, 95% CI 2.45 to 20.5, p=0.001). At 5 years, the cumulative redislocation rate was 26.1% in the off-track group compared with 8.7% in on-track group. The rate of any recurrent instability was 60% (n=15) v 18% (n=27) (RR 3.33, 95% CI 2.02 to 5.20, p<0.0001). Glenoid track (on v off) was not predicted by gender (p=0.411).

In a typical UK population assessment of the glenoid track on an MR arthrogram can be used to risk stratify patients with shoulder instability.