The effect of intrinsic loading and reconstruction upon grip capacity and finger extension kinematics

To compare active and passive reconstructive procedures for tetraplegia and their ability to produce a powerful grip and allow appropriate finger extension in a cadaveric model.

Seventeen fresh-frozen hands were used, which included 5 in intrinsic minus and intrinsic activation conditions, 6 with Zancolli-lasso tenodeses, and 6 with modified House tenodeses to simulate intrinsic function. To test grip, flexor digitorum profundus tendons were powered with a motor. Polyvinyl chloride cylinders of diameters 43, 51, 57, 70, or 89 mm and masses 250, 400, or 550 g were used. Grip was considered successful if the cylinder was grasped and resisted gravity. Finger extension was tested by powering the extensor tendons in the same hands.

No successful grasps were recorded in the intrinsic minus hands for larger diameter cylinders (≥ 70 mm), whereas multiple successes were seen after intrinsic activation and after Zancolli-lasso and House procedures. Whereas active intrinsic and the House reconstruction reached near full extension, this was not true for the Zancolli-lasso group.

These data demonstrated that active and passive intrinsic reconstruction methods improved basic grasp and release kinematics in experimental cadaver hand models. Using our model and based on the more optimal kinematics and full extension of the House procedure, we suggest that this should be the preferred tenodesis-based intrinsic reconstruction method. Nevertheless, both procedures were equally successful at grasping objects of the sizes and masses studied.

Comparative clinical studies are indicated to corroborate the findings of this cadaveric hand model.