Does using a low-profile inlay in a Grammont-style shoulder prosthesis decrease the risk of scapular notching?

Purpose: Scapular notching after reverse shoulder arthroplasty (RSA) is a common complication associated with impingement from excessive contact between the humeral implant and the scapula. While low-profile inlays (high mobility) were designed to reduce inferior notching, their clinical impact remains unclear. We investigated the effects of a low-profile inlay on range of motion and the incidence of scapular notching and shoulder dislocation.

Methods: 120 patients with 123 prostheses [low-profile (n = 88) or standard (n = 35) inlay] who underwent elective RSA for a rotator cuff tear or primary omarthritis (June 2016-August 2021) were included in this single-centre study. Follow-up continued for two years postoperatively, including radiological and clinical exams. Comparisons among the three groups in the primary analyses were based on postoperative glenosphere overhang [low 0-3 mm (n = 13), medium > 3-6 mm [n = 53) high > 6 mm (n = 57)].

Results: No significant difference in notching occurred between inlay types. Furthermore, none of the variables in the logistic regression model were associated with notching (inlay type, overhang, age, gender, indication, body mass index). Notching rates among the overhang groups were similarly distributed (46% low, 55% medium, and 39% high; p = 0.261). Only one dislocation occurred in the cohort. Low-profile inlays resulted in better median postoperative external rotation (40°, IQR 30-45) than the standard inlays (20°, IQR 10-40; p = 0.0002).

Conclusion: A low-profile inlay was not associated with decreased incidence of scapular notching within two years postoperatively. However, external rotation improved significantly and no increased risk of dislocation was detected. The extent of glenosphere overhang was not associated with scapular notching, regardless of the inlay type.