A biomechanical confirmation of the relationship between critical shoulder angle (CSA) and articular joint loading.

Villatte, Guillaume; van der Kruk, Eline; Bhuta, Asim I.; Zumstein, Matthias A.; Moor, Beat K.; Emery, Roger J. H.; Bull, Anthony M. J.; Reilly, Peter (2020). A biomechanical confirmation of the relationship between critical shoulder angle (CSA) and articular joint loading. Journal of shoulder and elbow surgery, 29(10), pp. 1967-1973. Elsevier 10.1016/j.jse.2020.03.002

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BACKGROUND

The critical shoulder angle (CSA) has been shown to be correlated with shoulder disease states. The biomechanical hypothesis to explain this correlation is that the CSA changes the shear and compressive forces on the shoulder. The objective of this study is to test this hypothesis by use of a validated computational shoulder model. Specifically, this study assesses the impact on glenohumeral biomechanics of modifying the CSA.

METHODS

An inverse dynamics 3-dimensional musculoskeletal model of the shoulder was used to quantify muscle forces and glenohumeral joint forces. The CSA was changed by altering the attachment point of the middle deltoid into a normal CSA (33°), a reduced CSA of 28°, and an increased CSA of 38°. Subject-specific kinematics of slow and fast speed abduction in the scapular plane and slow and fast forward flexion measured by a 3-dimensional motion capture system were used to quantify joint reaction shear and compressive forces.

RESULTS

Increasing the CSA results in increased superior-inferior forces (shearing forces; integrated over the range of motion; P < .05). Reducing CSA results in increased lateromedial (compressive) forces for both the maximum and integrated sum of the forces over the whole motion (P < .01).

DISCUSSION/CONCLUSION

Changes in the CSA modify glenohumeral joint biomechanics with increasing CSA producing higher shear forces that could contribute to rotator cuff overuse, whereas reducing the CSA results in higher compressive forces that contribute to joint wear.

Item Type:

Journal Article (Original Article)

Division/Institute:

04 Faculty of Medicine > Department of Orthopaedic, Plastic and Hand Surgery (DOPH) > Clinic of Orthopaedic Surgery

UniBE Contributor:

Zumstein, Matthias, Moor, Beat Kaspar

Subjects:

600 Technology > 610 Medicine & health

ISSN:

1058-2746

Publisher:

Elsevier

Language:

English

Submitter:

Kathrin Aeschlimann

Date Deposited:

04 Dec 2020 14:41

Last Modified:

05 Dec 2022 15:42

Publisher DOI:

10.1016/j.jse.2020.03.002

PubMed ID:

32499200

Uncontrolled Keywords:

Critical shoulder angle (CSA) computational shoulder model glenohumeral joint joint wear rotator cuff

BORIS DOI:

10.7892/boris.149039

URI:

https://boris.unibe.ch/id/eprint/149039

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