Lateralized Center of Rotation and Lower Neck-Shaft Angle Are Associated With Lower Rates of Scapular Notching and Heterotopic Ossification and Improved Pain for Reverse Shoulder Arthroplasty at 1 Year

Heterotopic ossification and scapular notching are common following reverse total shoulder arthroplasty. Compared with the original Grammont-style prosthesis with a medialized center of rotation (COR) and a 155 degrees neck-shaft angle, lateralization of COR and reduction of neck-shaft angle have been associated with decreased incidence of scapular notching. The authors hypothesized that these design features may also be effective in reducing heterotopic ossification after reverse total shoulder arthroplasty. Ninety-seven consecutive patients who underwent reverse total shoulder arthroplasty performed by a single surgeon were included in the study. Forty-eight patients received a Grammont-style prosthesis, and 49 received a prosthesis with either 6 mm or 10 mm of lateral COR offset and a 13 degrees neck-shaft angle. Radiographs at 1-year follow-up were reviewed by 2 surgeons for notching and heterotopic ossification. Patient-reported outcome scores and range of motion were also compared between the groups. More patients in the Grammont-style group showed scapular notching (Grammont, 35.4%; lateral COR, 12.2%; P=.018) and heterotopic ossification (Grammont, 47.9%; lateral COR, 22.4%; P=.009). The lateralized COR group reported lower pain on the visual analog scale (Grammont mean, 1.1; lateral COR mean, 0.5; P=.01) and trended toward better American Shoulder and Elbow Surgeons scores (Grammont mean, 77.2; lateral COR mean, 83.4; P=.05). However, range of motion was similar between the 2 groups. Compared with the Grammont-style prosthesis, the lateralized COR prosthesis with a decreased neck-shaft angle resulted in a lower incidence of both scapular notching and heterotopic ossification as well as better pain scores and a trend toward improved function at 1 year after reverse total shoulder arthroplasty.