A Method for Predicting Collagen Fiber Alignment in the Glenohumeral Capsule During Clinically Relevant Deformations

Injury to the anteroinferior (anterior band of the inferior glenohumeral ligament (AB-IGHL) and axillary pouch) glenohumeral capsule is a common result of anterior dislocation [1]. Validated finite element models of the capsule can be used to address research questions regarding diagnostic and repair techniques targeted to this region of the capsule. However, these models require adequate constitutive models to describe capsule behavior. Structural models have improved predictions of capsule behavior compared to phenomenological models [2] but current experimental techniques used to measure fiber distributions in biologic soft tissues require that the sample be planar and cannot be performed on three-dimensional structures. Although recent work has demonstrated that the fiber kinematics in the capsule do not precisely follow the global tissue deformation [3], the affine assumption is presently the best approximation to provide initial insight into changes in collagen fiber alignment under moderate deformations. The collagen fibers in localized areas of planar samples from the anteroinferior capsule align with the direction of loading [4,5]; however, their behavior may be quite different during the complex loading conditions experienced by the intact capsule. Therefore, the objective of this work was to computationally project planar fiber distribution information to the three-dimensional glenohumeral capsule and use the affine assumption to quantify the change in fiber alignment of the anteroinferior glenohumeral capsule from an inflated reference state to three clinically relevant joint positions.Copyright © 2012 by ASME