Reverse total shoulder arthroplasty: radiological and clinical result using an eccentric glenosphere

Abstract

In reverse shoulder arthroplasty, an eccentric glenosphere has been developed with the aim of lowering the centre of rotation, in order to prevent inferior scapular notching as occurs with concentric designs. The objective of this retrospective study was to evaluate clinical and radiographic outcomes using the eccentric glenosphere and to determine whether this design might prevent inferior scapular notching. Between 2006 and 2010, 40 patients affected by cuff tear arthropathy underwent reverse shoulder arthroplasty with an eccentric 36-mm glenoid component. Patients with less than 2 years' follow-up were excluded. The results for 25 patients with a minimum of 24 months' follow-up are reported. Clinical and radiographic evaluation was performed preoperatively and at 1, 3, 6 months, 1 year and annually thereafter. All patients were evaluated with MRI or CT scan preoperatively and with X-ray examinations postoperatively to evaluate the presence of inferior scapular notching and to measure the prosthesis-scapular neck angle (PSNA), the peg-glenoid rim distance (PGRD) and the distance between the scapula neck and the glenosphere. At last follow-up (average 27.5 months, range 24-46), the Constant Score, the VAS score and range of motion had improved significantly. The average PSNA was 92° + 29°, the average PGRD was 21.2 mm + 9 mm and the average distance between the inferior bony glenoid rim and the inferior edge of the glenosphere was 4.3 mm + 0.8 mm. No inferior scapular notching and no implant-related complications were seen. The data suggest that use of an eccentric glenosphere lowers the centre of rotation, reducing the risk of inferior scapular notching. Level of evidence IV.