Wrist kinematic coupling and performance during functional tasks: effects of constrained motion

To quantify the coupled motion of the wrist during selected functional tasks and to determine the effects of constraining this coupled motion using a radial-ulnar deviation blocking splint on performance of these tasks.

Ten healthy, right-handed men performed 15 trials during selected functional tasks with and without a splint, blocking radial and ulnar deviation. The following tasks were performed: dart throwing, hammering, basketball free-throw, overhand baseball and football throwing, clubbing, and pouring. Kinematic coupling parameters (coupling, kinematic path length, flexion-extension range of motion, radial-ulnar deviation range of motion, flexion-extension offset, and radial-ulnar deviation offset) and performance were determined for each functional task. A generalized estimation equation model was used to determine whether each kinematic coupling parameter was significantly different across tasks. A repeated-measures generalized estimation equation model was used to test for differences in performance and kinematic coupling parameters between the free and splinted conditions.

Wrist motion exhibited linear coupling between flexion-extension and radial-ulnar deviation, demonstrated by R(2) values from 0.70 to 0.99. Average wrist coupling and kinematic path lengths were significantly different among tasks. Coupling means and kinematic path lengths were different between free and splinted conditions across all tasks other than pouring. Performance was different between wrist conditions for dart throwing, hammering, basketball shooting, and pouring.

Wrist kinematic coupling parameters are task specific in healthy individuals. Functional performance is decreased when wrist coupling is constrained by an external splint.

Surgical procedures that restrict wrist coupling may have a detrimental effect on functional performance as defined in the study. Patients may benefit from surgical reconstructive procedures and wrist rehabilitation protocols designed to restore kinematic coupling.