Prosthetic component relationship of the reverse Delta III total shoulder prosthesis in the transverse plane of the body.

The Delta III (DePuy International Ltd, Leeds, UK) reverse total shoulder prosthesis has provided a successful functional outcome in cuff tear arthropathy (CTA); however, internal and external rotation remain compromised. Positioning of the prosthetic components in the transverse plane has theoretically been suggested to affect rotation. Twenty-seven patients who received a Delta III reversed total shoulder prosthesis for CTA were analyzed (mean follow-up, 43 months) using standard radiographs and computed tomography. The position of the prosthetic components and the possible influence of scapular rotation was analyzed using a uniform spatial reference system using axes in reference to the sagittal or coronal plane. We assessed impingement of the humeral component on the glenoid neck in neutral and internal rotation. An increase in the anterior divergence of the glenoid and humeral prosthetic components correlates with an increase in radiologically measured internal rotation (r = 0.932, P < .001). The uniformity of the reference system used seems to allow accurate positioning of the components intraoperatively and can be useful for analysis of the prosthetic component relationship postoperatively.