Glenosphere disengagement in a reverse total shoulder arthroplasty with a non-Morse taper design

In modern modular reverse total shoulder arthroplasty designs, glenosphere disengagement has recently been described in systems that use a locking screw and Morse taper for fixation between the glenosphere and baseplate. This complication is unreported in modern systems that do not use a Morse taper design. The purpose of this paper is to report cases of glenosphere disengagement and its incidence in a previously unreported design.

This study is a retrospective review of 40 patients who underwent reverse total shoulder arthroplasty for rotator cuff arthropathy using the Equinoxe® reverse total shoulder system, which uses a non-Morse taper design. Two patients were diagnosed with glenosphere disengagement postoperatively.

In this series two of 40 patients were retrospectively diagnosed with glenosphere disengagement. One patient had complete and one partial disengagement. Both patients were revised and subsequently did well. This represents an overall incidence of glenosphere disengagement of 5 % in this design.

This series demonstrates an overall incidence of glenosphere disengagement of 5 % in reverse total shoulder arthroplasty with a non-Morse taper design. The incidence of overall and complete disengagement is higher in this series than previously published in modern designs with Morse tapers. Features unique to this design, include the non-Morse taper interface, offset screw placement and unique bone graft cage, may explain its higher incidence of disengagement. Surgeons who use this system should be aware of this potential complication.