Artikel
Anterior and posterior scapular impingement associated with two different reverse shoulder designs
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Autoren
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R. Jones
- Southeastern Sports Medicine, Asheville, United States
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C. Roche
- Exactech Inc., Gainsville. Florida, United States
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P.-H. Flurin
- Clinique du Sport de Bordeaux-Mérignac, Mérignac, France
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T. Wright
- University of Florida, Gainsville, Florida, United States
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L. Crosby
- Wright State, Orthopaedic Surgery, Dayton Ohio, United States
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J. D. Zuckermann
- NYU Hospital for Joint Diseases, New York, United States
| Veröffentlicht: | 21. Oktober 2010 |
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Gliederung
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Objective: Concerns of scapular notching with reverse shoulders have driven design and surgical technique modifications that improve range of motion (ROM) and stability: most commonly, inferiorly offsetting the glenosphere. The purpose of this study is to quantify the effect of inferior glenosphere offset alone to prevent scapular impingement for the Grammont reverse shoulder. The Grammont is then compared to the Equinoxe reverse shoulder because it utilizes additional design modifications (not just inferior glenosphere offset) to improve ROM.
Methods: Two reverse shoulder prostheses (36 mm Grammont and the 38, 42, and 46 mm Equinoxe; Exactech, Inc.) were modeled and assembled to a 3-D digitized scapula. To quantify the effect of inferior glenosphere offset on ROM, the Grammont glenosphere was implanted 1 mm inferior to the center of the glenoid and inferiorly offset by 2–4 mm. The Equinoxe glenospheres were implanted in the center of the glenoid. A computer analysis then quantified scapular impingement as the humerus was internally/externally rotated during humeral abduction.
Results and conclusions: A motion profile was generated for each design; the enclosed area of each plot quantified the total motion associated with each design. The 38, 42, and 46 mm Equinoxe were associated with 45%, 69%, 82% greater motion than the 1mm inferiorly offset Grammont and 13%, 32%, and 43% greater motion than the 4 mm inferiorly offset Grammont.
At higher levels of abduction, both designs impinge at the base of the coracoid/acromion in internal/external rotation, respectively. At mid-levels of abduction, the possible motion associated with each design exceeds the physiologic range. At lower levels of abduction, the humeral liner impinges on the scapular neck in internal/external rotation in the physiologic range of motion. While inferiorly offsetting the glenosphere reduces inferior scapular impingement and increases overall motion, the significant improvements in ROM associated with the Equinoxe demonstrate that inferiorly offsetting the glenosphere alone is insufficient to eliminate inferior scapular impingement.
