Comparison of trapeziometacarpal joint motion between genders using multiple measurement techniques

Hulbert, Robert
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University of Delaware
Thumb function accounts for up to 50 percent of total hand function with most of its function coming from the trapeziometacarpal (TMC) joint, located at the base of the thumb between the first metacarpal and trapezium. The TMC joint is unique in that it has two non-intersecting, non-orthogonal axes of rotation that generate three distinct motions; flexion/extension, abduction/adduction and pronation/supination. Past studies have analyzed overall ROM of the TMC joint by simultaneously measuring maximal planar and composite motions, which together form a spherical surface area used to find the maximal workspace. However, none of these studies have compared their results with range of motion (ROM) or workspace measurements obtained during clinical tests such as the thumb opposition portion of the Modified Kapandji Index (MKI), which is designed to measure the thumb component of overall hand mobility. Analysis of TMC kinematics is also important in identifying potential risk factors of TMC osteoarthritis (OA), one of the most common diseases of the hand. TMC OA is believed to be caused by increased joint ROM, and has been shown to be more prevalent in the female population. However, past studies analyzing TMC kinematics between genders have shown mixed results, so it becomes imperative to determine if females display significantly greater TMC ROM and workspace than males. The purpose of this study was to determine the difference in ROM and workspace measurements at the trapeziometacarpal joint between genders using multiple measurement techniques. An eight camera motion capture system was used to track the location of retroreflective markers placed on the wrist, hand, and thumb. Based on these marker locations, coordinate systems for the wrist, hand, and thumb were built. TMC axis orientation and TMC workspace were then calculated using custom software written in LabVIEW and Matlab. Comparisons between the MKI task and Max TMC task showed that the MKI task displays significantly less abduction/adduction ROM (p=.038) and workspace (p=.045) than the Max TMC task. Comparisons between genders for each of the measured motions showed no significant differences in TMC ROM in either of the TMC axes. Comparisons between genders during each of the multi-movement tasks (MKI and Max TMC) showed no significant differences in TMC workspace. These results indicate that increased mobility is not a viable explanation for the increased likelihood of developing TMC OA in the female population, which raises further research questions aimed at determining the TMC joint differences between genders which may explain the discrepancy in TMC OA development. These results also prove that the clinical MKI test is ineffective in measuring the entire ROM and workspace of the thumb. This means that it may need to be done in unison with other tests to ensure that the patient is exploring a greater amount of their available TMC abduction/adduction ROM and workspace. This information is important to both clinicians and patients as it may help to improve on the process of clinically measuring and evaluating thumb ROM and function in injured and pathological populations. While this research has proven beneficial in determining kinematic differences between healthy populations, future research should focus on the development of an accurate musculoskeletal model of the human thumb with the ability of assessing both kinematic and kinetic parameters. This would prove to be a valuable tool that could be used to track the onset and progression of thumb related pathologies as well as make comparisons between different subject populations, such as individuals with healthy TMC joints and individuals with osteoarthritic TMC joints. This future thumb model would also be a monumental tool which could be used by surgeons and clinicians to optimize pre-surgical planning and assess different treatment outcomes at an individual patient level.