Effect of supraspinatus deficiency on humerus translation and glenohumeral contact force during abduction.
- Terrier A Laboratoire de Biomécanique en Orthopédie EPFL-HOSR, STI-IGBM-LBO, Bâtiment AA.B0, Station 15, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland. alexandre.terrier@epfl.ch <alexandre.terrier@epfl.ch>
- Reist A
- Vogel A
- Farron A
- 2007-03-21
Published in:
- Clinical biomechanics (Bristol, Avon). - 2007
Algorithms
Biomechanical Phenomena
Finite Element Analysis
Humans
Humerus
Movement
Muscle, Skeletal
Rotator Cuff Injuries
Shoulder Joint
English
BACKGROUND
Supraspinatus deficiency is the most frequent and important problem associated to rotator cuff pathologies. It reduces shoulder stability and can lead to osteoarthritis. The goal of this study was to develop a numerical model of the shoulder to analyse the biomechanical consequences of this pathology.
METHODS
A 3D finite element model of the shoulder was developed from a normal cadaver specimen. It included the scapula, the humerus and the major abduction muscles. Instead of the usual ball-socket assumption, which prevents the natural translation of the humerus, shoulder stability was actively achieved by muscles. A feedback algorithm was developed to synchronise muscle forces during abduction. The numerical algorithm was validated against an algebraic model, and the calculated muscle moment arms were compared to the literature. Two cases were considered: a normal shoulder and the same one without supraspinatus.
FINDINGS
For the normal shoulder, the model predicted the initial upward migration of the humeral head. The maximal humerus translation occurred at 30 degrees of abduction and was 0.75 mm above its ideal centered position. Without supraspinatus, it was 1.6 times higher and the contact point in the glenoid fossa was more eccentric. For the normal shoulder, the maximal glenohumeral force was 81% of the body weight, at 82 degrees of abduction. Without supraspinatus, it increased by 8%, while the increase of muscle forces was 30%.
INTERPRETATION
Supraspinatus deficiency increased the upward migration of the humerus, the eccentric loading, and the joint and muscle forces, which may cause a limitation of active abduction and degenerative glenohumeral changes (osteoarthritis and the rotator cuff tear).
Supraspinatus deficiency is the most frequent and important problem associated to rotator cuff pathologies. It reduces shoulder stability and can lead to osteoarthritis. The goal of this study was to develop a numerical model of the shoulder to analyse the biomechanical consequences of this pathology.
METHODS
A 3D finite element model of the shoulder was developed from a normal cadaver specimen. It included the scapula, the humerus and the major abduction muscles. Instead of the usual ball-socket assumption, which prevents the natural translation of the humerus, shoulder stability was actively achieved by muscles. A feedback algorithm was developed to synchronise muscle forces during abduction. The numerical algorithm was validated against an algebraic model, and the calculated muscle moment arms were compared to the literature. Two cases were considered: a normal shoulder and the same one without supraspinatus.
FINDINGS
For the normal shoulder, the model predicted the initial upward migration of the humeral head. The maximal humerus translation occurred at 30 degrees of abduction and was 0.75 mm above its ideal centered position. Without supraspinatus, it was 1.6 times higher and the contact point in the glenoid fossa was more eccentric. For the normal shoulder, the maximal glenohumeral force was 81% of the body weight, at 82 degrees of abduction. Without supraspinatus, it increased by 8%, while the increase of muscle forces was 30%.
INTERPRETATION
Supraspinatus deficiency increased the upward migration of the humerus, the eccentric loading, and the joint and muscle forces, which may cause a limitation of active abduction and degenerative glenohumeral changes (osteoarthritis and the rotator cuff tear).
- Language
-
- English
- Open access status
- green
- Identifiers
-
- DOI 10.1016/j.clinbiomech.2007.01.015
- PMID 17367904
- Persistent URL
- https://roar.hep-bejune.ch/global/documents/209632
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