Functional grasp potential of the intrinsic minus hand

The functional grasp potential of a hand controlled only by extrinsic muscles or by both intrinsic and extrinsic muscles was investigated using a biomechanical model simulation. The simulation, which was based on a set of equilibrium equations, was driven by muscle-like forces. Contact with fixed objects provided external forces, which interacted with muscle forces and joint passive moments to produce finger position. It was found that functional grasps of several different sized objects could be obtained using only extrinsic muscles, but that the position of the object with respect to the hand was an important parameter. Using both intrinsic and extrinsic muscles provided additional object positions at which functional grasp could be achieved. These results could prove useful in training people using functional electrical stimulation systems to restore hand function