Clinical and Radiological Comparison between Asian-Type and Conventional Reverse Shoulder Arthroplasty: A Multicenter Randomized Controlled Trial.

Background: In patients with reverse shoulder arthroplasty (RSA), the relationship between the patient's body size and implant size is important for postoperative shoulder function. Asian patients, who have a short stature, could find the conventional RSA implant too big and tight. This study aimed to evaluate the clinical and radiological outcomes after RSA in Asian patients using a new implant designed to fit the body size of Asian patients. We also aimed to compare these outcomes with those who received a conventional implant.

Methods: This prospective study enrolled 120 patients who underwent RSA for a symptomatic irreparable massive rotator cuff tear, cuff tear arthropathy, or primary osteoarthritis with a full-thickness rotator cuff tear. Patients were randomly allocated 2:1 to receive an Asian-type RSA implant (group I) or conventional RSA implant (group II). All patients underwent plain radiography to evaluate acromiohumeral distance, acromion-deltoid tuberosity distance, lateral humeral offset, and center of rotation distance. Postoperative 1-year computed tomography (CT) scans were obtained for all patients to evaluate the position of peg screws and baseplates and the presence of scapular notching. Clinical outcomes were evaluated using American Shoulder Elbow Surgeons (ASES) score, Constant score, and active range of motion.

Results: Finally, 112 patients (80 in group I and 32 in group II) were included in this study. The mean patient age was 74.0 ± 5.5 years, and the mean patient height was 154.6 ± 8.1 cm. At the last visit, clinical scores and active range of motion significantly improved in both groups; however, the improvements did not differ significantly between the 2 groups. On the postoperative 1-year CT scan, the glenoid baseplate was more anteriorly placed in group II than in group I. The supero-inferior position of the glenoid baseplate did not significantly differ between the 2 groups. Other radiological parameters obtained through plain radiography showed no significant differences between the 2 groups. No differences were found in scapular notching (p = 0.999) and acromial stress fracture (p = 0.872) between the 2 groups.

Conclusions: Asian-type RSA implants showed comparable clinical and radiological outcomes with conventional RSA implants. Asian-type RSA implants allowed more accurate positioning of the glenoid baseplate, although that did not translate into superior clinical and radiological outcomes.