Reverse Total Shoulder Arthroplasty—Biomechanics and Rationale

Reverse total shoulder arthroplasty (RTSA) was designed to provide pain relief, improve functional results, and reduce the risk of implant failure in patients with a painful rotator cuff-deficient shoulder. Understanding the biomechanics and rationale behind the surgical technique and its relationship to implant design is essential. The design and biomechanics of RTSA is based upon principles put forth by Grammont. These are inherent prosthetic stability, convexity of the glenoid components with complementing concavity of the humeral component, glenosphere center placement at or within the glenoid neck, and a medialized and distalized center of rotation. In addition, patient selection, surgical technique, and postoperative management all factor in the functional success of RTSA. Component sizing, version, glenoid baseplate fixation and placement, humeral neck-shaft angle and distalization, and surgical approach are all choices made by the informed surgeon. Each factor plays a role in the functional outcome of an RTSA and its potential complications.