Is limited external rotation after reverse shoulder arthroplasty associated with glenoidal notching? An observational study

Background Reverse shoulder arthroplasty (RSA) is a valuable solution for patients with shoulder pain or injury primarily due to a rotator cuff tear or secondary to traumatic events. Nevertheless, several complications are known to appear, with the most frequent being scapular notching (SN) on the inferior and posterior scapular neck. Controversial data exist about the clinical relevance of SN. Since further consequences are still not clearly understood, we aimed to provide more clarity on which factors, especially external rotation (ER), contribute to the appearance and progress of notching. Methods Constant Score (CS), Subjective Shoulder Value (SSV), flexion, abduction, and ER were evaluated retrospectively in 153 shoulders of 147 patients (mean age 79 +/- 7.7 years; 62% women) who underwent RSA between 2005 and 2010. Anteroposterior radiographs were evaluated before and 1, 2, 3, and 5 years after RSA for SN according to the Sirveaux classification. The evaluation was performed by two independent surgeons. Spearman's coefficient and t-test were used. Results CS, SSV, flexion, and abduction increased significantly 1 year after RSA compared to before (all p < 0.0001). No improvement was shown for ER between the same timepoints. Between 2 and 5 years of follow-up, only flexion decreased by 5 degrees(p = 0.02) while CS, SSV, abduction, and ER remained constant. After RSA, notching increases over time. There was no association between SN and CS, SSV, flexion, abduction or ER at any of the measured timepoints. Higher flexion correlated with higher abduction after RSA at every follow-up (1 year r = 0.88, 2 years r = 0.89, 3 years r = 0.86, 5 years r = 0.86). The interrater correlation test showed a strong correlation (r = 0.7). Conclusion We verified the functional benefits of RSA for patients. Additionally, our findings show that despite radiographic progression of notching and unchanged limited ER, the postoperative improvements in CS, SSV, flexion, and abduction are preserved over 5 years.