Predictive factors of scapular notching in patients with reverse shoulder arthroplasty

IntroductionThe main complication of reverse shoulder arthroplasty is the development of notches in the scapular pillar, which occurs in 44% to 100% of cases. Furthermore the functional score has been shown to be poorer in patients with high-grade notches. Many options have been proposed to reduce this risk. The purpose of this study was to evaluate the predictive factors of the development of scapular notches.Materials and methodsWe retrospectively evaluated 133 shoulders in 121 patients with reverse shoulder arthroplasty. We performed a radiographic assessment of the effect of positioning the glenoid component with inferior overhang of the glenosphere and the glenometaphyseal angle. All patients were reviewed after 2 years follow-up, including a clinical assessment based on the Constant score and X-rays to assess the presence of notches.ResultsNineteen complications were reported, and 14 required revision surgery. We excluded patients in whom prosthetic components were changed. The quality of the X-rays was not satisfactory enough to be analyzed in over 15 patients so they were excluded. One hundred five patients were reviewed. At 2 years follow-up, 50.4% of shoulders presented with notches. The Constant score was 69.3 points (54–83) in shoulders without notches, and 66.4 points (38–82) in shoulders with notches. The average glenosphere overhang was 3.5 mm (−1 – 8 mm). Notches were present in 65.5% if it was less than 3 mm and 39.6% if it was more than 2 mm (P < 0. 05). The average glenometaphyseal angle was 27.3° (4–59°), and notches developed in 72.2% if it was more than 28° and 26.5% if it was less than 28° (P < 0.05).ConclusionThe position of the metaglene influences the development of notches. The risk decreases if the glenosphere overhangs the glenoid. The degree of adduction of the arm influences the development of notches and can be correlated with the patient's BMI.Level of evidenceLevel IV retrospective study.