Review Question - QID 219823

The patient has evidence of posterior glenohumeral instability with subcritical bone loss by anterior instability standards. Isolated posterior labral repair in a contact athlete with such bone loss is likely to have a higher recurrence rate without a bony augmentation procedure.

Posterior shoulder instability and dislocations are less common than anterior shoulder instability and dislocations but are much more commonly missed. Chronic instability can be diagnosed with the presence of positive posterior instability provocative tests (i.e., the jerk and Kim tests) and confirmed with MRI studies showing posterior labral pathology. In isolation, posterior labral tears can often be successfully treated with physical therapy and conservative measures; however, in contact athletes with recurrent pain with loading of the arm in a forward-flexed position (i.e. bench press, football blocking, etc.), arthroscopic Bankart repair may be indicated. It is essential to note that studies have shown that posterior glenoid bone loss has a lower critical value than anterior glenoid bone loss, meaning that isolated posterior labral repairs in this population with sub-critical bone loss is likely to have a high recurrence rate without the addition of a bony augmentation procedure.

Bradley et al. reviewed the risk factors and outcomes of revision arthroscopic posterior shoulder capsulolabral repairs in contact athletes. The authors looked at a total of 149 contact athletes' shoulders 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 minimum 4-year and average 13.0-year follow-up, with smaller glenoid bone width being a risk factor and predictor for worse return to play.

Arner et al. attempted to define critical glenoid bone loss in posterior shoulder capsulolabral repair. The authors note that although critical bone loss for anterior instability is well-defined, a clinically significant threshold of posterior bone loss has not been elucidated. They reviewed 75 patients and found 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. They concluded that risk factors for failure of arthroscopic posterior shoulder capsulolabral repair include smaller glenoid bone width and a greater percentage of glenoid bone loss.

Figures A and B are post-operative AP and axillary lateral radiographs of the shoulder showing posterior glenoid bone loss treated with a bony augmentation procedure.

Incorrect Answers:
Answer 1: A modified McLaughlin procedure involves lesser tuberosity transfer into a reverse Hill-Sachs defect and is indicated in the setting of chronic posterior dislocations, which this patient does not have.
Answer 2: There is no literature to show that isolated labral repair results in improved outcomes scores, and there is literature to suggest higher recurrence rates as the amount of posterior glenoid bone loss increases beyond 11% of the glenoid diameter.
Answer 3: A large reverse Hill-Sachs in the setting of a chronic posterior dislocation would be an indication for a lesser tuberosity transfer.
Answer 4: Recurrence rates of posterior instability increase as the amount of posterior glenoid bone loss increases, and this is likely to a higher degree even with subcritical bone loss by anterior instability standards.