Copyright ©The Author(s) 2018. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Orthop. Nov 18, 2018; 9(11): 245-254
Published online Nov 18, 2018. doi: 10.5312/wjo.v9.i11.245
Biomechanics of posterior shoulder instability - current knowledge and literature review
Henrik Constantin Bäcker, Samuel E Galle, Mauro Maniglio, Melvin Paul Rosenwasser
Henrik Constantin Bäcker, Samuel E Galle, Melvin Paul Rosenwasser, Department of Orthopedic Surgery, New York Presbyterian/Columbia University Medical Center, New York, NY 10032, United States
Mauro Maniglio, Department of Orthopedics, HFR Cantonal Hospital of Fribourg, Fribourg 1752, Switzerland
Author contributions: All authors equally contributed to this paper with conception and design of the study, literature review and analysis, drafting and critical revision and editing, and final approval of the final version.
Conflict-of-interest statement: No potential conflicts of interest.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:
Correspondence to: Henrik Constantin Bäcker, MD, Academic Fellow, Research Fellow, Senior Postdoctoral Fellow, Surgeon, Department of Orthopedic Surgery, Columbia University Medical Center - Presbyterian Hospital, 622 West, 168th Street, 11th floor, Apartment 64, New York, NY 10032, United States.
Telephone: +1-212-3053912 Fax: +1-212-3421749
Received: July 12, 2018
Peer-review started: July 12, 2018
First decision: August 2, 2018
Revised: August 7, 2018
Accepted: October 10, 2018
Article in press: October 10, 2018
Published online: November 18, 2018

Posterior instability of the shoulder is a rare condition and represents about 10% of shoulder instability. It has become more frequently recognized in the last year, even though it is more difficult to diagnose than anterior shoulder instability. As this form of shoulder pathology is somewhat rare, biomechanical knowledge is limited. The purpose of our study was to perform an extensive literature search, including PubMed and Medline, and to give an overview of the current knowledge on the biomechanics of posterior shoulder instability. The PubMed/Medline databases were utilized, and all articles related to posterior shoulder instability and biomechanics were included to form a comprehensive compilation of current knowledge. A total of 93 articles were deemed relevant according to our inclusion and exclusion criteria. As expected with any newly acknowledged pathology, biomechanical studies on posterior shoulder instability remain limited in the literature. Current biomechanical models are performed in a static manner, which limits their translation for explaining a dynamic pathology. Newer models should incorporate dynamic stabilization of both the rotator cuff and scapulothoracic joint. There is a current lack of knowledge with regards to the pathomechanism of posterior shoulder instability, with no consensus on appropriate treatment regimens. Further investigation is therefore required at both basic science and clinical levels.

Keywords: Posterior shoulder instability, Anatomy, Shoulder complex, Scapula, Humerus, Glenohumeral

Core tip: Posterior shoulder instability is an infrequent type of injury, and there is limited discussion of this topic within the literature. Other authors have acknowledged the current paucity of papers on this topic. To our knowledge, no comparable literature review has been performed showing the interactions of the individual shoulder parts, including the osseous structures, capsule, labrum, ligaments and muscles[1]. This article aspires to help develop new protocols to investigate shoulder instability and inform clinicians about the importance of this topic in daily practice.