Does posterior half-wedge augmented glenoid restore version and alignment in total shoulder arthroplasty for the B2 glenoid?

INTRODUCTION: Walch type B2 has biconcave glenoid with posterior erosion, bone loss and humeral head subluxation. This leads to decreased glenohumeral contact area and increased contact pressure. During total shoulder arthroplasty(TSA), uncorrected retroversion causes eccentric loading and failure of glenoid component. It also leads to humeral head decentring with posterior rim loading, early glenoid wear and component loosening. This study aims to review anatomical restoration of glenoid version and humeral head centring in TSA with B2 glenoid using CT scans.
METHODS: This is a retrospective review of TSA for glenohumeral osteoarthritis with B2 Glenoid morphology. All polyethylene posterior wedge augmented glenoid component was used. All patients underwent pre and post surgery CT Scans. Glenoid version was calculated using neoglenoid line and medial scapular border as reference point. Post-operative humeral head centering was calculated using offset of centre of rotation of humeral head with plane of scapula on axial CT-Scan.
RESULTS: Study had 10 patients with 11 TSA between June 2017 and July 2018. Mean age was 59(45-80)years. Mean preoperative retroversion was 16(13-23)degrees. This was corrected to a mean of 0° retroversion postoperatively. 63% had good radiological correction (0-5° retroversion). Humeral head was well centered post-operatively with mean humeral scapula alignment offset of 2.1(0.8-4.5) mm posteriorly. All cases had well-centered humeral head postoperatively with offset less than 5 mm.
CONCLUSIONS: Total shoulder replacement in B2 glenoid is technically demanding. Our radiological results show favourable outcome in terms of correction of gelenoid retroversion and eliminating posterior instability using wedge glenoid component. LEVEL OF EVIDENCE: IV.