Effects of simulated injury on the anteroinferior glenohumeral capsule.

Glenohumeral dislocation results in permanent deformation (nonrecoverable strain) of the glenohumeral capsule which leads to increased range of motion and recurrent instability. Minimal research has examined the effects of injury on the biomechanical properties of the capsule which may contribute to poor patient outcome following repair procedures. The objective of this study was to determine the effect of simulated injury on the stiffness and material properties of the AB-IGHL during tensile deformation. Using a combined experimental and computational methodology, the stiffness and material properties of six AB-IGHL samples during tensile elongation were determined before and after simulated injury. The AB-IGHL was subjected to 12.7 ± 3.2 % maximum principal strain which resulted in 2.5 ± 0.9 % nonrecoverable strain. The linear region stiffness and modulus of stress-stretch curves between the normal (52.4 ± 30.0 N/mm, 39.1 ± 26.6 MPa) and injured (64.7 ± 21.3 N/mm, 73.5 ± 53.8 MPa) AB-IGHL increased significantly (p = 0.03, p = 0.04). These increases suggest that changes in the tissue microstructure exist following simulated injury. The injured tissue could contain more aligned collagen fibers and may not be able to support a normal range of joint motion. Collagen fiber kinematics during simulated injury will be examined in the future.