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Open Access Research article

Reverse shoulder arthroplasty leads to significant biomechanical changes in the remaining rotator cuff

Sebastian Herrmann1*, Christian König2, Markus Heller2, Carsten Perka1 and Stefan Greiner1

Author Affiliations

1 Center for Musculosceletal Surgery, Charité-Universitätsmedizin Berlin, Charitéplatz 1, D-10117 Berlin, Germany

2 Julius Wolff Institute, Charité - Universitätsmedizin Berlin, Center for Sports Science and Sports Medicine Berlin (CSSB) Philippstr. 13, 10115 Berlin, Germany

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Journal of Orthopaedic Surgery and Research 2011, 6:42  doi:10.1186/1749-799X-6-42

Published: 16 August 2011

Abstract

Objective

After reverse shoulder arthroplasty (RSA) external and internal rotation will often remain restricted. A postoperative alteration of the biomechanics in the remaining cuff is discussed as a contributing factor to these functional deficits.

Methods

In this study, muscle moment arms as well as origin-to-insertion distance (OID) were calculated using three-dimensional models of the shoulder derived from CT scans of seven cadaveric specimens.

Results

Moment arms for humeral rotation are significantly smaller for the cranial segments of SSC and all segments of TMIN in abduction angles of 30 degrees and above (p ≤ 0.05). Abduction moment arms were significantly decreased for all segments (p ≤ 0.002). OID was significantly smaller for all muscles at the 15 degree position (p ≤ 0.005), apart from the cranial SSC segment.

Conclusions

Reduced rotational moment arms in conjunction with the decrease of OID may be a possible explanation for the clinically observed impaired external and internal rotation.

Keywords:
shoulder arthroplasty; cuff tear arthropathy; reverse shoulder prosthesis; biomechanics shoulder; moment arms; rotator cuff