Scapular (glenoid and acromion) osteotomies for the treatment of posterior shoulder instability: technique and preliminary results.

Background: Static and dynamic posterior shoulder instability (PSI) are associated with a higher, more horizontal acromion providing poor posterior humeral head (HH) coverage. The current surgical treatment yields unsatisfactory long-term outcomes with high recurrence rates in dynamic and failure to restore joint concentricity in static PSI. We hypothesized that restoring physiological acromio-glenoid relations would prevent recurrence of dynamic and positively influence static PSI. Methods: This study reports the outcome after a "scapular (acromion and glenoid) corrective osteotomy for posterior escape procedure in 9 consecutive patients at a minimum 2-year follow-up. One patient had static, 2 had dynamic and 6 had combined PSI. Osteotomies to restore normal scapular bony anatomy were three-dimensionally planned and executed with three-dimensional printed cutting and reduction guides. Preoperatively and postoperatively the absolute Constant Scores (CS), relative CS, subjective shoulder value and glenohumeral subluxation indices (GHSIs) and scapulohumeral subluxation indices (SHSIs) were measured. Results: The mean age at surgery was 37 years (±9.3; 23-47) and mean follow-up was 29 months (±8). In 6 patients, the operation was a revision. In 1 case, we operatively failed to achieve the planned correction resulting in clinical failure, persistent subluxation, and osteoarthritis progression. For the other 8 patients, the median subjective shoulder value increased by 42.5%, absolute CS by 18 points, relative CS by 18%, pain score by 3.5 points. The SHSI was ≥61% in 7/7 patients, GHSI was ≥55% in 4/7 patients. In 5/7 patients with pathological SHSI, the HH was recentered; in 2/7, it was improved but remained ≥61%. In 2/4 patients with the pathological GHSI, the HH was recentered, and improved but remained ≥55% in the other 2. All patients had subjectively stable shoulders. Conclusion: At a minimum of 2 years successful correction of scapular anatomy can improve static subluxation and restore subjective and objective shoulder stability.