Review Question - QID 219936

The patient has symptomatic posterior shoulder instability with evidence of posterior glenoid bone loss. Recent literature has shown that even "sub-critical" bone loss of the posterior glenoid increases the risk for failure of isolated arthroscopic capsulolabral repair when it is not addressed at the time of the index procedure (Answer 4).

Posterior labral tears are referred to as reverse Bankart lesions and represent attenuation of the posterior capsulolabral complex, which most commonly occurs due to repetitive microtrauma in "blocking" athletes such as football linemen or weightlifters. The diagnosis can be made clinically with positive posterior labral provocative tests such as the Jerk and Kim tests, and is confirmed with MRI imaging of the shoulder. Although arthroscopic capsulolabral repair has traditionally been associated with high rates of success, increased attention has been given to risk factors for failure of arthroscopic repair, which has increasingly been shown to be associated with reduced posterior glenoid bone width. As little as 11% posterior glenoid bone loss has been associated with a 10.4 times higher surgical failure rate when treated with isolated arthroscopic capsulolabral repair alone.

Bradley et al. reviewed the risk factors for and outcomes of revision arthroscopic posterior shoulder capsulolabral repair in contact athletes. The authors included a total of 149 contact athletes and found that the only significant risk factor for requiring revision surgery was decreased glenoid bone width. They concluded that contact athletes underwent revision arthroscopic posterior capsulolabral repair at an incidence of 5.4% at an average of 13.0-year follow-up, with the only significant risk factors for requiring revision surgery being smaller glenoid bone width and higher preoperative instability, and that return to play after their subsequent surgery was significantly worse.

Arner et al. attempted to define critical bone loss in posterior shoulder capsulolabral repair. The authors compared MRI measurements from 19 patients with failed arthroscopic posterior shoulder capsulolabral repair with those from 56 patients whose surgery was successful. They found that smaller glenoid width and greater percentage of glenoid bone loss were seen in those patients with failed surgery. They concluded that a cutoff of 11% glenoid bone loss resulted in a 10.4 times statistically higher surgical failure rate, while a 15% bone loss resulted in a 24.4 times statistically higher failure rate.

Hines et al. reviewed the prevalence and outcomes of glenoid bone loss in the arthroscopic treatment of posterior shoulder instability. The authors included 43 patients with a mean follow-up of 53.7 months and found that those with >13.5%, subcritical glenoid bone loss, were statistically less likely to return to full duty, but outcomes scores, complications, and revision rates were otherwise not different in those with no or minimal bone loss versus those with more significant amounts.

Figures A and B are axial and sagittal T1-weighted MRI images showing a posterior labral tear and posterior glenoid bone loss exceeding 15%, respectively.

Incorrect Answers:
Answer 1: Though the theory of obligate translation does dictate that tightening the posterior tissues will result in obligate anterior translation of the humeral head, this would be therapeutic in this particular patient and would be unlikely to result in anterior instability.
Answer 2: Though this number could technically be defined as "sub-critical" bone loss if it were being assessed for anterior instability, posterior glenoid bone loss as little as 11 % of the glenoid width has been associated with in excess of 10x risk for surgical failure of isolated posterior capsulolabral repair.
Answer 3: Glenoid width is more predictive than the glenoid version for recurrence risk in the setting of isolated capsulolabral repair for posterior shoulder instability.
Answer 5: Corrective osteotomy may be indicated in cases of excessive glenoid retroversion, but this does not obviate the need for a bony augmentation procedure in the setting of posterior glenoid bone loss.