Influence of Combined Hill-Sachs and Bony Bankart Defects on Range of Motion in Anterior Instability of the Shoulder in a Finite Element Model

Piyush Walia; Anthony Miniaci; Morgan H Jones; Stephen D Fening

doi:10.1016/j.arthro.2015.04.099

Influence of Combined Hill-Sachs and Bony Bankart Defects on Range of Motion in Anterior Instability of the Shoulder in a Finite Element Model

Arthroscopy. 2015 Nov;31(11):2119-27. doi: 10.1016/j.arthro.2015.04.099. Epub 2015 Jul 2.

Authors

Piyush Walia¹, Anthony Miniaci², Morgan H Jones², Stephen D Fening³

Affiliations

¹ Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, U.S.A.; Department of Orthopaedic Surgery, Summa Health System, Akron, Ohio, U.S.A.; Department of Chemical and Biomedical Engineering, Cleveland State University, Cleveland, Ohio, U.S.A.
² Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, U.S.A.; Department of Orthopaedic Surgery, Cleveland Clinic, Cleveland, Ohio, U.S.A.
³ Case Western Reserve University, Cleveland, Ohio, U.S.A.. Electronic address: steve.fening@case.edu.

PMID: 26142052
DOI: 10.1016/j.arthro.2015.04.099

Abstract

Purpose: To quantify the effect of different size combinations of Hill-Sachs defects and bony Bankart defects on shoulder instability across a broad range of motion.

Methods: A computer-based finite element approach was used to model an intact glenohumeral joint. Defects were created for the glenoid with respect to its width (12.5%, 25%, 37.5%, and 50%). The defect sizes chosen for the humeral head were 6%, 19%, 31%, and 44% of the diameter. Simulations were analyzed using quasi-static analysis with displacement control under 50 N of medial compression. Distance to dislocation (DTD) was the primary outcome.

Results: Every progressive bony Bankart defect lowered the value of DTD (P < .0001). These DTD values of individual glenoid defects were the same for every abduction and rotation angle. This may be an artifact due to the glenoid's spherical-shape assumption, which was necessary for the sample-specific model and is not a completely accurate representation of specimen-specific geometry. The largest glenoid defect size had a DTD value of 0 mm, which signifies no contact between surfaces. At 90° of abduction, Hill-Sachs defect sizes 19%, 31% (P < .0001), and 44% (P < .0001) further reduced DTD values gradually after 30° of external rotation, 10° of external rotation, and 20° of internal rotation, respectively. This signifies loss of contact between articulating surfaces, resulting in reduced motion. However, at a 45° abduction angle, the loss of contact only occurred for humeral head defect sizes 31% and 44%.

Conclusions: This model shows that increasing shoulder instability is predicted by increasing humeral head and glenoid defect sizes for a broad envelope of motion. The size of glenoid defect can be used to determine the baseline stability. An additional humeral head defect can further reduce the stability when the arm is in external rotation because of loss of contact.

Clinical relevance: The data from this study will be helpful in establishing thresholds for performing bony reconstructions.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Biomechanical Phenomena / physiology
Computer Simulation*
Finite Element Analysis
Humans
Joint Instability / physiopathology*
Range of Motion, Articular / physiology*
Shoulder Injuries
Shoulder Joint / physiopathology*