Comparison of three different models to represent the wrist during wheelchair propulsion

Due to the high incidence of secondary wrist injury among manual wheelchair users, recent emphasis has been placed on the investigation of wheelchair propulsion biomechanics. Accurate representation of wrist activity during wheelchair propulsion may help to elucidate the mechanisms contributing to the development of wrist injuries. Unfortunately, no consensual wrist biomechanical model has been established. In order to determine if different methodologies obtain similar results, this investigation created and compared three different wrist models: 1) a fixed joint center placed between the styloids (midstyloid joint center); 2) a joint center with 2/spl deg/ of freedom computed from de Leva's joint center data; and 3) a floating joint center. Results indicate that wrist flexion and extension angles are highly consistent between models, however, radial and ulnar deviation angles vary considerably. Mean maximum right flexion angles were found to be 3.5/spl deg/, 2.2/spl deg/, and 5.0/spl deg/ for the midstyloid, de Leva, and floating joint center models, respectively. Extension angles were 22.3/spl deg/, 23.6/spl deg/, and 23.6/spl deg/, respectively. Mean maximum right radial deviation angles for the midstyloid, de Leva, and floating joint center models were 26.0/spl deg/, 26.9/spl deg/, and 45.1/spl deg/, respectively, and ulnar deviation angles were found to be 30.5/spl deg/, 38.8/spl deg/, and 10.2/spl deg/, respectively. This information is useful when comparing kinematic studies and further supports the need for consensual methodology.