Effect of retroversion of the humeral component on functional outcomes in reverse total shoulder arthroplasty

The recommended humeral stem retroversion angle (HSRA) is 0 to 30 for reverse shoulder arthroplasty (RSA). The literature contains few clinical studies on this topic. We aim to assess the effect of the HSRA determined by computerized tomography (CT) on the range of motion (ROM) of the joint, the functional score, and the activities of daily living (ADL) in patients who have undergone RSA. Patients who underwent RSA surgery were retrospectively analyzed. Patients implanted with a HSRA less than 25° on CT scan were categorized in Group I, and patients with a greater angle in Group II. ROM, the Constant Murley score (CMS), American Shoulder and Elbow Scores (ASES), and ADL were used for the functional evaluation at the final follow-up control. Our study comprised 40 patients; Group I comprised 21, and Group II of 19 patients. The mean age was 70.5 years in Group I and 68.9 years in Group II. The mean follow-up time was 14.9 months in Group I and 13.8 months in Group II. At the last follow-up, the external rotation was 39.6±6 in Group I and 46.4±5.7 in Group II, while the internal rotation was Lumbar vertebra 1 in Group I and Lumbar vertebrae 3 in Group II (p=0.028 and <0.001). After surgery, functional scores and ADL significantly increased in all patients. When the groups were compared, the results of the patients in Group I were significantly higher. While ROM increased significantly after RSA in both groups, internal rotation and related ADL were better in the patients implanted with less retroversion. In view of our results, implantation at 20° retroversion would be suitable for better results and higher satisfaction.