Good functional outcome but high rates of instability recurrence after posterior open-wedge glenoid osteotomy for the treatment of posterior shoulder instability with increased glenoid retroversion at mid-term follow-up

Purpose: To evaluate clinical, functional and radiological mid-term outcomes following posterior open-wedge glenoid osteotomy (POWGO) for the treatment of posterior shoulder instability (PSI) associated with increased glenoid retroversion. Methods: Patients who underwent POWGO for the treatment of symptomatic PSI with glenoid retroversion >10° and participated in a previous study assessing short-term outcomes were included after a minimum follow-up of 5 years. Clinical (Rowe score and physical examination) and functional outcomes (Oxford Shoulder Instability Score [OSIS] and visual analogue scale [VAS] for pain) were assessed. Preoperative versus follow-up magnetic resonance imaging (MRI) assessments were compared for changes in posterior humeral head subluxation (PHHS) and progression of osteoarthritis (shoulder osteoarthritis severity [SOAS] score). Results: Eight patients (nine shoulders) were included 92.0 months (88.0–109.5 months) post-operatively, of which seven patients (eight shoulders) underwent MRI. Shoulder function was good (Rowe score: 80.0 [76.3–91.3], OSIS: 41.0 [31.0–41.5]) and pain levels were low (VAS for pain: 3.0 [1.0–3.0]) at follow-up. Overall, the degree of PHHS did not change between preoperatively and follow-up (p > 0.05). Four shoulders demonstrated PHHS preoperatively, of which two had a centred humeral head at follow-up. Shoulder osteoarthritis progressed significantly (SOAS score: 17.0 [11.0–24.5] to 33.0 [31.0–45.0], p = 0.018). Residual PSI was evident in 75.0% of shoulders. Conclusion: At mid-term follow-up, POWGO for PSI associated with increased glenoid retroversion led to good functional outcomes but failed to reliably restore posterior shoulder stability and prevent osteoarthritis progression. Level of Evidence: Level IV.