Clinical and Radiological Outcomes in Lateralized versus Non-lateralized and Distalized Glenospheres in Reverse Total Shoulder Arthroplasty: A Randomized Control Trial.

Abstract

Lateralization in reverse total shoulder arthroplasty (RTSA) has been used to theoretically offer the potential benefits of reduced scapular notching rates and improved stability and range of motion (ROM), particularly external rotation. The aim of this study was to compare ROM, clinical and radiographic outcomes between patients who underwent RTSA with a lateralized versus a non-lateralized and distalized glenosphere. A single surgeon randomized control trial was conducted comparing 27 patients with a lateralized glenosphere and 26 patients with a non-lateralized and distalized glenosphere. 66 patients were enrolled, two patients died prior to two-year follow-up, four patients withdrew from the study and seven patients were lost to follow-up. All patients in the lateralized group received 6 mm of lateralization through the glenosphere. Participants represented a population presenting to an orthopedics sports medicine clinic with any indication for RTSA including revision arthroplasty. Patients completed preoperative and routine postoperative functional outcome measures 3, 6, 12, and a minimum of 24 months postoperatively including American Shoulder and Elbow Surgeons (ASES), Patient-Reported Outcomes Measurement Information System Physical Function Upper Extremity (PROMIS PF UE) and Activities of Daily Living Requiring Active External and Internal Rotation (ADLEIR) assessments. Patients were also evaluated with ROM and radiographic measurements. The primary outcome of interest in this study was ROM, particularly external rotation. At two-year follow-up, both groups had significant improvement in their ASES, PROMIS PF UE and ADLEIR scores with no significant difference observed between groups. There were no statistically significant differences in incidence of scapular notching or acromial stress fractures. ROM in both groups improved significantly at their two-year assessment with the only exception to this being external rotation at 90° of abduction in the non-lateralized and distalized group (39° ± 31° versus 48° ± 24°, p=0.379). Regardless of glenosphere lateralization status, patients in both groups had significant improvement in functional outcome scores and ROM and there were no significant differences observed between groups at two-year follow-up. Longer follow-up is needed to determine the effect of implant design on late complications, long-term outcomes and implant retention.