Shawn Peter Reese

Learn More
Experimental measurements of the Poisson's ratio in tendon and ligament tissue greatly exceed the isotropic limit of 0.5. This is indicative of volume loss during tensile loading. The microstructural origin of the large Poisson's ratios is unknown. It was hypothesized that a helical organization of fibrils within a fiber would result in a large Poisson's(More)
An objective measurement technique to quantify 3D femoral head shape was developed and applied to normal subjects and patients with cam-type femoroacetabular impingement (FAI). 3D reconstructions were made from high-resolution CT images of 15 cam and 15 control femurs. Femoral heads were fit to ideal geometries consisting of rotational conchoids and(More)
The proteoglycan decorin is known to affect both the fibrillogenesis and the resulting ultrastructure of in vitro polymerized collagen gels. However, little is known about its effects on mechanical properties. In this study, 3D collagen gels were polymerized into tensile test specimens in the presence of decorin proteoglycan, decorin core protein, or(More)
The topics of verification and validation have increasingly been discussed in the field of computational biomechanics, and many recent articles have applied these concepts in an attempt to build credibility for models of complex biological systems. Verification and validation are evolving techniques that, if used improperly, can lead to false conclusions(More)
The underlying mechanisms for the viscoelastic behavior of tendon and ligament tissue are poorly understood. It has been suggested that both a flow-dependent and flow-independent mechanism may contribute at different structural levels. We hypothesized that the stress relaxation response of a single tendon fascicle is consistent with the flow-dependent(More)
Ligaments and tendons undergo volume loss when stretched along the primary fiber axis, which is evident by the large, strain-dependent Poisson's ratios measured during quasi-static tensile tests. Continuum constitutive models that have been used to describe ligament material behavior generally assume incompressibility, which does not reflect the volumetric(More)
Aligned, collagenous tissues such as tendons and ligaments are composed primarily of water and type I collagen, organized hierarchically into nanoscale fibrils, microscale fibers and mesoscale fascicles. Force transfer across scales is complex and poorly understood. Since innervation, the vasculature, damage mechanisms and mechanotransduction occur at the(More)
Mechanical injury to connective tissue causes changes in collagen structure and material behaviour, but the role and mechanisms of molecular damage have not been established. In the case of mechanical subfailure damage, no apparent macroscale damage can be detected, yet this damage initiates and potentiates in pathological processes. Here, we utilize(More)
In vitro polymerized type I collagen hydrogels have been used extensively as a model system for three-dimensional (3D) cell and tissue culture, studies of fibrillogenesis, and investigation of multiscale force transmission within connective tissues. The nanoscale organization of collagen fibrils plays an essential role in the mechanics of these gels and(More)
In this study, a new nitinol based fixation device was investigated for use in repairing severed digital flexor tendons. The device, composed of superelastic nitinol, is tubular in shape with inward facing tines for gripping tissue. Its cellular structure was designed such that it has a large effective Poisson's ratio, which facilitates a “finger trap”(More)