Relationship of scapular neck length to scapular notching after reverse total shoulder arthroplasty by use of plain radiographs

Abstract

Scapular notching in reverse shoulder arthroplasty appears to be a multifactorial problem related to both implant and patient factors. There are well-established guidelines for implant position. Recent cadaveric studies have illustrated anatomic factors that need further consideration. Scapular neck length and inferior glenoid tubercle morphology may be major factors predicting scapular notching. From 2 institutions, we reviewed 3 years of patient radiographs for reverse shoulder arthroplasty, including all reverse shoulder arthroplasties at least 12 months from surgery. We used true anterior-posterior radiographs, both preoperatively and postoperatively, and focused on the "ideal" positioning of the glenosphere: at or below the inferior margin of the glenoid, and neutral or slight inferior tilt. Radiographs were reviewed by 2 independent surgeons. Glenoid articular surface height was measured along with scapular neck length and notching presence. Of 64 sets of radiographs reviewed, 50 met inclusion criteria. Notching was present in only 25 (50%) of the sets. The mean scapular neck length was 8.9 mm with a neck:surface ratio of 0.23 in the notching present group and 12.1 mm with a neck:surface ratio of 0.32 in the notching absent group. Significance was reached with both scapular neck length and neck:surface ratio (P = .0012 and P = .0006, respectively). There is a high degree of significance that patient anatomy does play a role in the occurrence of notching. Surgeons may consider lateralizing the glenosphere in patients with a scapular neck length of less than 9 mm measured on a true anteroposterior radiograph. Anatomy study, imaging.