Posterior shoulder instability is a rare condition, representing only 4% of all shoulder-joint instabilities. Numerous surgical techniques are used to treat it when conservative functional treatment proves to be insufficient. This retrospective study relates to 8 patients, presenting recurrent posterior shoulder instability, all treated with a posterior iliac bone-block procedure. The results were assessed both clinically and with contemporary imaging techniques.

A unique identical surgical technique was used in all these cases including a posterior deltoid head detachment, an infraspinatus muscle dissociation and a bone-block positioning intended to extend and enlarge the glenoid cavity rather than to act as an actual block. Seven of these 8 cases were posttraumatic (including 2 with a concomitant congenital hyperlaxity past history) and the non-traumatic 1 was secondary to an epileptic seizure episode. All the patients had a typical posterior shoulder instability clinical presentation in the form of recurrent true dislocation incidents. In 6 cases, imaging revealed lesions of the humeral head or the glenoid cavity. These lesions were displacement-related anterior impaction defects of the humeral head (McLaughlin lesion) and/or a fracture (or erosion) of the posterior glenoid rim. Mean postoperative follow-up was 34 months.

No cases of postoperative suprascapular nerve deficit were observed. All patients recovered normal joint range of motion in abduction and anterior elevation; in 3 patients, however, external rotation ended up being limited by an average 20̊ compared to the opposite side. The mean Constant score was 96.25 points and the mean Duplay score 90. Only 4 patients were able to return to their preoperative sports activity level. Three required an additional procedure, 2 for hardware removal and 1 for posterior deltoid repair, which all lead to an uneventful evolution. Imaging at follow-up (X-ray or CT) did not show any instance of bone-block pseudoarthrosis or osteolysis nor did it exhibit glenohumeral early degenerative changes. In all, at a mean 3years’ follow-up, the present series showed satisfactory results in 80% of cases. A literature review found comparable results for bone-block stabilization procedures. No recurrences of instability are reported with this technique, the main difficulty of which residing in the correct positioning of the bone-block. The stabilizing efficacy and low subsequent arthritic changes of the iliac posterior bone-block graft procedure seem thus confirmed by these encouraging results.

The iliac posterior shoulder bone-block is effective in managing instances of involuntary posterior shoulder instability. A review of the literature confirmed these satisfactory results in terms of non-recurrence, pain relief and function recovery with this technique; the main difficulties of this technique remains in the correct positioning of the bone-block and the proper orientation of the fixation screws.