Posterior bone block procedure for posterior shoulder instability.

The posterior bone block procedure is an uncommon surgical procedure used in the treatment of posterior shoulder instability. The purpose of this study is to report the results of the posterior bone block procedure in the treatment of posterior shoulder instability. We retrospectively reviewed 21 shoulders that had undergone a posterior bone block procedure in the treatment of recurrent posterior shoulder instability between 1984 and 2001. Fifteen patients (16 shoulders) had a prior traumatic posterior glenohumeral dislocation and 5 patients (5 shoulders) had a prior traumatic posterior glenohumeral subluxation. The mean age at surgery was 24.8 years (range 17-40 years). Patients were evaluated with the Constant score, the Duplay score, a subjective result, and radiography. Preoperatively, ten shoulders had glenoid fractures, two shoulders had loss of the normal contour of the posterior osseous glenoid, and ten shoulders had humeral head impaction fractures (reverse Hill-Sachs lesion). Seventeen shoulders underwent preoperative computed tomography and had average glenoid retroversion of 9.6 degrees (range 0-21 degrees ). At an average follow-up of 6 years, all patients reported their subjective results as good or excellent. At follow-up the mean Constant score was 93.3 points (range 80-103 points), and the mean Duplay score was 85.6 points (range 40-100 points). Fifteen patients returned to sports at their pre-injury level. Three patients were considered clinical failures; one with a recurrent posterior dislocation and two with substantial posterior apprehension on follow-up examination. Two shoulders had glenohumeral arthritis on radiographs at the latest follow-up. The posterior bone block is a good treatment option for posterior dislocation. The risk of recurrent dislocation is low following this procedure.