The relationship between scapular notching and reverse shoulder arthroplasty prosthesis design

Background: Inferior scapular notching is a common radiographic complication of reverse shoulder arthroplasty. The purpose of this study is to determine the impact of prosthesis design on the incidence and severity of notching. Materials and methods: Eighty-eight patients (mean age, 72 years) who underwent reverse shoulder arthroplasty with a minimum of 12 months' follow-up (mean, 31 months) were retrospectively reviewed. Patients were grouped based on prosthesis design: Tornier (Stafford, TX, USA) (45%), Zimmer (Warsaw, IN, USA) with a nonretentive liner (35%), and Zimmer with a retentive liner (19%). Notching on final radiographs was graded by use of the Sirveaux classification system and a novel classification system. Results: The incidence of notching was significantly higher with the Tornier prosthesis (92%) compared with the Zimmer prosthesis with nonretentive liners (58%) and retentive liners (71%) (P < .05). The incidence of high-grade notching and the median grade were significantly higher with the Tornier prosthesis compared with the Zimmer prosthesis (P < .05). By use of the novel grading system, there was a higher incidence of notching involving the baseplate with the Tornier prosthesis (68%) compared with the Zimmer prosthesis (33%) (P < .05). The addition of a retentive liner was not associated with greater notching than a nonretentive liner for the Zimmer implant. Diagnosis had no significant influence on notching. Conclusions: A higher incidence and severity of notching were observed with the Tornier reverse arthroplasty compared with the Zimmer reverse arthroplasty at short-term follow-up. These findings may be because of the different morphology of the polyethylene component and/or differences in glenosphere offset between the prosthetic systems. In addition to surgical technique, consideration should be given to prosthesis design in mitigating the risk of scapular notching.