Intrinsic hand muscle function, part 2: kinematic comparison of 2 reconstructive procedures.

PURPOSE: Reconstruction of grasp is a high priority for tetraplegic patients. Restoration of finger flexion by surgical activation of flexor digitorum profundus can result in roll-up finger flexion, interphalangeal (IP) joint before metacarpophalangeal (MCP) joint flexion, which can be improved by restoring intrinsic function. This study compares grasp kinematics between 2 intrinsic balancing procedures-Zancolli-lasso and House.

METHODS

The intrinsic muscles of 12 cadaver hands were reconstructed by either the Zancolli-lasso or the House procedure (n = 6 each) and tested by deforming the flexor digitorum profundus (FDP) with a motor to simulate hand closure. Results were compared with 5 control hands. All 17 hands were studied by video analysis. Kinematics were characterized by the order of MCP joint and IP joint flexion. Optimal grasp was defined as the maximal fingertip-to-palm distance during the arc of finger closure.

RESULTS

Kinematics differed between the 2 procedures. The Zancolli-lasso reconstructed hands flexed first in the IP joints, and then in MCP joints, resembling an unreconstructed intrinsic-minus hand whereas the House reconstructed hands flexed first in the MCP joints and then in the IP joints, resembling an intrinsic-activated hand. Maximal fingertip-to-palm distance did not differ significantly between the 2 procedures, and both showed improvement over unreconstructed controls.

CONCLUSIONS

Both intrinsic balancing techniques improved grasp. Only the House procedure restored hand kinematics approximating those of an intrinsic-activated hand. Improvement in fingertip-to-palm distance in Zancolli-lasso hands resulted primarily from the initial resting MCP joint flexion of 40°. We therefore advocate the more physiological House procedure for restoration of intrinsic function in tetraplegic patients.

CLINICAL RELEVANCE: This study provides a rationale for advocacy of 1 reconstructive procedure over another.