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

PURPOSE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: Wrist kinematic coupling parameters are task specific in healthy individuals. Functional performance is decreased when wrist coupling is constrained by an external splint. CLINICAL RELEVANCE: 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.

The accuracy of an automasking algorithm in plantar pressure measurements.

Masking algorithms provide a way to analyze plantar pressure parameters based on distinct anatomical regions of the foot. No study has addressed their accuracy. The purpose of this study was to determine the accuracy of the Novel® ten-region standard masking algorithm in both dynamic and static measurements in normal feet. Static and dynamic plantar pressure measurements were collected from ten normal subjects (20 ft) with and without 10-mm radiopaque markers placed under the first through fifth metatarsal heads, fifth metatarsal base, and first proximal phalanx. The automask was then applied to subdivide the foot into distinct anatomical areas. Weight-bearing AP radiographs were obtained with and without markers. Plantar pressures and radiographs were overlaid. The percent accuracy of each marker within its appropriate mask region was calculated. The average accuracies of the automasking algorithm regions for dynamic and static measurements, respectively, were 98.8% and 90.4% (1MH), 89.9% and 80.6% (2MH), 98.6% and 81.4% (3MH), 96.8% and 82.3% (4MH), 93.1% and 80.8% (5MH), 97.3% and 92.5% (5MB), and 91.2% and 64.2% (1PPH). Marker presence did not alter foot structure or function as determined by intermetatarsal angles (range, p = 0.361 to p = 0.649) and the center of pressure excursion index (p = 0.727), respectively. The automasking algorithm accurately identifies most foot regions in normal feet, particularly in gait. Such accuracy may be reduced in the setting of foot deformity. Understanding the accuracy of masking algorithms may help guide the interpretation of plantar pressure measurements and ultimately both conservative and operative treatment decisions.