The unoperated hand: the role of passive forces in hand function after tetraplegia.

Passive forces play a large role in hand function after tetraplegia. Most individuals with tetraplegia choose not to undergo surgical reconstruction of hand function and, therefore, depend on the passive properties of their musculoskeletal system to perform functional tasks. Knowledge of the levels of force needed to perform many of these tasks is lacking. Understanding the mechanics of producing passive force is important for designing adaptive tools and other devices for tetraplegic individuals. Knowledge of the passive properties of the upper extremity is important in forming treatment strategies. The passive forces produced for change to the tenodesis grasp are small but useful to the individual. Since these forces arise from basic anatomy and muscle function, they are important even after surgical restoration of hand function. Compensatory strategies for the unoperated hand probably play a role in the operated hand. The approach to surgical restoration of grasp must consider how passive forces contribute to functional outcome.