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Updated: Sep 26, 2026
Reverse Total Shoulder Arthroplasty
Published on: July 5, 2011
Relationship between implant positioning and post-operative scapulohumeral rhythm following reverse total shoulder
Itaru Kawashima1,2, Norimasa Takahashi3, Keisuke Matsuki3
1Department of Orthopaedic Surgery and Sports Medicine, University of Florida, Gainesville, FL, USA.
Background:
Scapulohumeral rhythm (SHR) after reverse total shoulder arthroplasty (rTSA) is typically reduced, with shoulder elevation relying predominantly on scapulothoracic motion. Previous studies have shown that higher post-operative SHR is associated with improved shoulder elevation and superior patient-reported outcome measures. Therefore, despite the non-anatomic design of rTSA, achieving a favorable SHR is desirable. Although implant positioning is believed to influence post-operative shoulder kinematics, the specific implant-related factors contributing to improved SHR remain unclear. This study aimed to investigate the relationship between post-operative SHR and changes in humeral lateralization or distalization, as well as medialization or distalization of the center of rotation.
Methods:
Forty-six shoulders from 45 patients who underwent rTSA at a single institution and achieved more than 90° of humeral abduction were included. The cohort comprised 27 men and 18 women with a mean age of 75 years. Three implant configurations were used as follows: medialized glenoid-medialized humerus, medialized glenoid-lateralized humerus, and medialized glenoid-mildly lateralized humerus. At a mean of 14 months post-operatively, computed tomography and fluoroscopy were performed during active scapular plane abduction. Three-dimensional implant and scapular motions were analyzed using model-image registration. SHR was calculated from 20° to 90° of humeral abduction. Implant positioning parameters were measured from post-operative radiographs, and changes from pre-operative values were calculated. Correlations between SHR and each parameter were assessed using Pearson correlation coefficient.
Results:
The mean SHR was 1.39 ± 0.64. A significant positive correlation was identified between post-operative SHR and the change in humeral distalization (r = 0.321, P = .030). No significant correlations were observed between SHR and other implant positioning parameters.
Conclusion:
The increase in humeral distalization from the pre-operative to the post-operative state following rTSA showed a significant but weak positive correlation with post-operative SHR, whereas no other implant positioning parameters were significantly correlated with post-operative SHR.
