Background
Scapular notching is a well-known postoperative complication of reverse total shoulder arthroplasty (RTSA). However, abduction notching (AbN), a subacromial erosion caused by repeated abduction impingement after RTSA, has not been previously reported in a clinical setting. Therefore, this study aimed to assess the risk factors and functional outcomes of AbN after RTSA.
Methods
We retrospectively reviewed the medical records of 125 patients who underwent RTSA with the same design and had at least two years of follow-up between March 2014 and May 2017. AbN was defined as subacromial erosion observed at the final follow-up but not on the X-ray three months after surgery. Radiologic parameters representing the patient's native anatomy and degrees of lateralisation and/or distalisation during surgery were evaluated using preoperative and three months postoperative X-rays. The visual analogue scale of pain (pVAS), active range of motion (ROM), and American Shoulder and Elbow Surgeons (ASES) score were assessed preoperatively and at the final follow-up to evaluate the functional outcomes of AbN.
Results
AbN occurred in 12.8% (16/125) of enrolled patients during the study period. Preoperative centre of rotation-acromion distance (CAD) (p = 0.009) and postoperative humerus lateralisation offset (HL), which evaluated the degree of lateralisation after RTSA (p = 0.003), were risk factors for AbN. The preoperative CAD and postoperative HL cutoff values were 14.0 mm and 19.0 mm, respectively. The pVAS (p = 0.01) and ASES score (p = 0.04) at the final follow-up were significantly worse in patients with AbN.
Conclusions
Abduction notching correlated with patients’ anatomical characteristics and the degree of lateralisation during RTSA. To prevent abduction notching, surgeons should adjust the implant’s degree of lateralisation according to patients’ anatomical characteristics.