Biomechanical investigation of arm position on deforming muscular forces in proximal humerus fractures
Background Muscular forces drive proximal humeral fracture deformity, yet it is unknown if arm position can help mitigate such forces. Our hypothesis was that glenohumeral abduction and humeral internal rotation decrease the pull of the supraspinatus and subscapularis muscles, minimizing varus fract...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
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Korean Shoulder and Elbow Society
2022-12-01
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| Series: | Clinics in Shoulder and Elbow |
| Subjects: | |
| Online Access: | http://www.cisejournal.org/upload/pdf/cise-2022-00885.pdf |
| _version_ | 1797330884356997120 |
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| author | Christen E. Chalmers David J. Wright Nilay A. Patel Hunter Hitchens Michelle McGarry Thay Q. Lee John A. Scolaro |
| author_facet | Christen E. Chalmers David J. Wright Nilay A. Patel Hunter Hitchens Michelle McGarry Thay Q. Lee John A. Scolaro |
| author_sort | Christen E. Chalmers |
| collection | DOAJ |
| description | Background Muscular forces drive proximal humeral fracture deformity, yet it is unknown if arm position can help mitigate such forces. Our hypothesis was that glenohumeral abduction and humeral internal rotation decrease the pull of the supraspinatus and subscapularis muscles, minimizing varus fracture deformity. Methods A medial wedge osteotomy was performed in eight cadaveric shoulders to simulate a two-part fracture. The specimens were tested on a custom shoulder testing system. Humeral head varus was measured following physiologic muscle loading at neutral and 20° humeral internal rotation at both 0° and 20° glenohumeral abduction. Results There was a significant decrease in varus deformity caused by the subscapularis (p<0.05) at 20° abduction. Significantly increasing humeral internal rotation decreased varus deformity caused by the subscapularis (p<0.05) at both abduction angles and that caused by the supraspinatus (p<0.05) and infraspinatus (p<0.05) at 0° abduction only. Conclusions Postoperative shoulder abduction and internal rotation can be protective against varus failure following proximal humeral fracture fixation as these positions decrease tension on the supraspinatus and subscapularis muscles. Use of a resting sling that places the shoulder in this position should be considered. |
| first_indexed | 2024-03-08T07:26:44Z |
| format | Article |
| id | doaj.art-f420dde98126473e9b9dd159ce80377e |
| institution | Directory Open Access Journal |
| issn | 2288-8721 |
| language | English |
| last_indexed | 2024-03-08T07:26:44Z |
| publishDate | 2022-12-01 |
| publisher | Korean Shoulder and Elbow Society |
| record_format | Article |
| series | Clinics in Shoulder and Elbow |
| spelling | doaj.art-f420dde98126473e9b9dd159ce80377e2024-02-02T21:53:07ZengKorean Shoulder and Elbow SocietyClinics in Shoulder and Elbow2288-87212022-12-0125428228710.5397/cise.2022.00885879Biomechanical investigation of arm position on deforming muscular forces in proximal humerus fracturesChristen E. Chalmers0David J. Wright1Nilay A. Patel2Hunter Hitchens3Michelle McGarry4Thay Q. Lee5John A. Scolaro6 Department of Orthopedic Surgery, University of California Irvine, Irvine, CA, USA Department of Orthopedic Surgery, University of California Irvine, Irvine, CA, USA Department of Orthopedic Surgery, University of California Irvine, Irvine, CA, USA Cornell University, Ithaca, NY, USA Orthopaedic Biomechanics Laboratory, Congress Medical Foundation, Pasadena, CA, USA Orthopaedic Biomechanics Laboratory, Congress Medical Foundation, Pasadena, CA, USA Department of Orthopedic Surgery, University of California Irvine, Irvine, CA, USABackground Muscular forces drive proximal humeral fracture deformity, yet it is unknown if arm position can help mitigate such forces. Our hypothesis was that glenohumeral abduction and humeral internal rotation decrease the pull of the supraspinatus and subscapularis muscles, minimizing varus fracture deformity. Methods A medial wedge osteotomy was performed in eight cadaveric shoulders to simulate a two-part fracture. The specimens were tested on a custom shoulder testing system. Humeral head varus was measured following physiologic muscle loading at neutral and 20° humeral internal rotation at both 0° and 20° glenohumeral abduction. Results There was a significant decrease in varus deformity caused by the subscapularis (p<0.05) at 20° abduction. Significantly increasing humeral internal rotation decreased varus deformity caused by the subscapularis (p<0.05) at both abduction angles and that caused by the supraspinatus (p<0.05) and infraspinatus (p<0.05) at 0° abduction only. Conclusions Postoperative shoulder abduction and internal rotation can be protective against varus failure following proximal humeral fracture fixation as these positions decrease tension on the supraspinatus and subscapularis muscles. Use of a resting sling that places the shoulder in this position should be considered.http://www.cisejournal.org/upload/pdf/cise-2022-00885.pdfproximal humeral fracturebiomechanicsrotator cuffshoulder joint |
| spellingShingle | Christen E. Chalmers David J. Wright Nilay A. Patel Hunter Hitchens Michelle McGarry Thay Q. Lee John A. Scolaro Biomechanical investigation of arm position on deforming muscular forces in proximal humerus fractures Clinics in Shoulder and Elbow proximal humeral fracture biomechanics rotator cuff shoulder joint |
| title | Biomechanical investigation of arm position on deforming muscular forces in proximal humerus fractures |
| title_full | Biomechanical investigation of arm position on deforming muscular forces in proximal humerus fractures |
| title_fullStr | Biomechanical investigation of arm position on deforming muscular forces in proximal humerus fractures |
| title_full_unstemmed | Biomechanical investigation of arm position on deforming muscular forces in proximal humerus fractures |
| title_short | Biomechanical investigation of arm position on deforming muscular forces in proximal humerus fractures |
| title_sort | biomechanical investigation of arm position on deforming muscular forces in proximal humerus fractures |
| topic | proximal humeral fracture biomechanics rotator cuff shoulder joint |
| url | http://www.cisejournal.org/upload/pdf/cise-2022-00885.pdf |
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