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Prior Years' Projects

2005

• Biomechanical Modeling of Tendon Transfer in Tetraplegia
• Functional Restoration of Grasp in Quadriplegia
• Multi-Center Trial to Improve Grasp in Tetraplegia
• Muscle-Tendon Adaptation following Tendon Transfer

2004

• Biomechanical Modeling of Tendon Transfer in Tetraplegia
• Functional Restoration of Grasp in Quadriplegia
• Muscle-Tendon Adaptation following Tendon Transfer Surgery

2003

• Biomechanical Modeling of Tendon Transfer in Tetraplegia
• Functional Restoration of Grasp in Quadriplegia
• Muscle-Tendon Adaptation following Tendon Transfer Surgery

2002

• Functional Restoration of Grasp in Quadriplegia (B1967R)
• Functional Restoration of Grasp in Quadriplegia (B2785R)

2001

• ProVAR Project, H F Machiel Van der Loos, PI
• Functional Restoration of Grasp in Quadriplegia

PhD Research

PhD Defense: Quantitative Assessment of Pinch Stability in the Tetraplegic Hand

The restoration of pinch in the tetraplegic hand through reconstructive hand surgery has profound consequences to the tetraplegic spinal cord injured individual (paralysis of all four limbs). Reacquiring the ability to perform common activities of daily living (ADLs) can reduce dependence on others and restore a greater sense of independence and self worth. Reconstructive hand surgeries are designed to restore both pinch force and pinch stability. However, while obtaining quantitative objective measures of pinch force is simple, a direct quantitative measure of pinch stability does not exist.

In this presentation, I discuss two research studies and the development of a novel pinch stability measure. The first study identifies pinch force magnitudes necessary to complete a set of common ADLs, chosen primarily from existing clinical functional assessment tests. Tetraplegic individuals are tested for lateral pinch strength and then asked to perform these same ADL tasks. With pinch force magnitude criteria, I am able to predict success or failure in 81.1% of subject trials. However, greater than 25% of task performance failures are not due to pinch strength deficits. This highlights the need for additional measures of pinch function, including pinch stability.

The concept of pinch stability, as I develop it here, is derived from grasp stability measures from the field of robotic manipulation. Specifically, the concept of grasp stiffness in combination with quasi-static analysis of compression spring buckling, leads to the development of a novel clinical pinch stability assessment tool, the Strength-Dexterity Kit. In addition to the development of the physical tool, I formulate a data analysis technique that distills the resulting large binary data sets down to single measures for pinch strength and pinch stability.

The Strength-Dexterity Kit is used, in the second study, to test the general hypothesis that the greater the number of muscles actuating the thumb, the greater the pinch strength and pinch stability. 12 non-impaired individuals and 22 tetraplegic individuals are tested. The tetraplegic group is divided into four sub groups: a pre-operative group, two post-operative groups separated by surgical procedure, and a non-surgical group with significant residual hand function. Non-parametric rank sum statistical tests identify pinch strength and stability differences between the subject groups. Perhaps most interestingly, the Strength Dexterity Kit effectively identifies pinch stability deficits in the post-operative group with the fewest muscles actuating the thumb (with respect to the other tetraplegic sub groups).

I conclude by discussing the implications of this research as they relate to tetraplegic reconstructive surgeries, the limitations of this work, and the future development of pinch stability measures.

Last updated 10/05/2007