Wrist Biomechanics Influence Hand Function: Computer Simulations and Cadaveric Experiments of Nonimpaired and Surgically Salvaged Wrists

The wrist is a complicated joint that implant technology has failed to effectively replicate. As a result, salvage procedures are used to treat wrist osteoarthritis. Salvage procedures successfully relieve osteoarthritic pain by removing, fusing, and repositioning the carpal bones of the wrist. These drastic, geometric changes result in long-term impairments in hand function. How salvage procedures, which specifically alter the wrist, result in hand impairments is not understood.;The goal of this dissertation is to analyze the biomechanical design of the nonimpaired and salvaged wrist to elucidate the mechanisms by which surgically altering the wrist impairs the hand. Specifically, two salvage procedures are examined: scaphoid-excision four-corner fusion (SE4CF) and proximal row carpectomy (PRC). These procedures treat the same degenerative diseases and result in the same post-operative impairments. Yet, each procedure alters the geometry of the wrist in different ways, thereby altering joint and muscle mechanics.;Studying the surgically salvaged wrist can provide valuable insights into the biomechanical design of not just the surgically altered wrist, but also the nonimpaired wrist. In this dissertation, cadaveric experiments and computer simulations are utilized to support this thesis. The cadaveric experiments measure key biomechanical parameters, namely muscle moment arms and wrist axes of rotation, in the nonimpaired and salvaged wrists. These experiments challenge current clinical views that salvage procedures are equivalent by quantifying significant differences between the SE4CF and PRC wrists and illustrating the need for rehabilitation strategies targeted at specific biomechanical deficits. The computer simulations probe the predictive limits of biomechanical models and provide a framework for studying how altering the biomechanical design of the wrist influences the production of endpoint forces in the hand. These simulations strive to overcome the current challenges preventing the efficient development of surgical models as well as the challenges of studying a system as complex as the wrist and hand. The simulation framework is particularly valuable because it is a tool with broad research applications to the study of the wrist and hand, ranging from biomechanical analysis of surgical procedures to the examination of neural control.