Article

For the nonimpaired individual, hand function is a consequence of active muscle contractions orchestrated by the central nervous system. For example, thumb function is controlled by 10 distinct muscles. For most individuals with cervical spinal cord injury, none of the muscles controlling finger or thumb movement is controlled actively. As a result, passive forces must assume a critical role in functional use of the hand after tetraplegia. An injury involving the cervical level of the spinal cord paralyzes muscles in the forearm and hand, with the degree of residual motor function traditionally linked to the segmental level of injury. In the unoperated tetraplegic upper extremity, an individual uses the hand to interact with the environment by combining residual voluntary control of proximal muscles and joints with the very small passive forces produced by finger and thumb muscles. Most rehabilitation modalities aimed at improving hand function after tetraplegia exploit the passive properties of the upper extremity. Many approaches, including the wrist-driven tional electrical stimulation, attempt to strengthen the natural patterns of movement arising from the passive force-generating characteristics of the paralyzed hand muscles. Passive tension produced by noncontracting structures is used most effectively for hand function by individuals who can extend the wrist after injury.
If wrist extension is voluntary, a tenodesis grasp is possible [1]. The tenodesis grasp is a mechanism of hand opening and closing that arises from passive forces developed by the extrinsic muscles of the fingers and thumb during wrist extension and flexion (Fig. 1). A functional tenodesis grasp is most frequently observed in injuries below the fifth cervical segment, where brachioradialis and one or two of the radial wrist extensors are spared. Individuals who can voluntarily extend the wrist benefit from the tenodesis grasp even if they have paralyzed wrist flexors, because gravity can assist wrist flexion. Individuals with an effective tenodesis grasp are able to pick up light objects, such as finger food, and can often learn how to hold a utensil to eat, write, and brush their teeth [2]. Individuals who cannot extend the wrist are more dependent on assistance for many daily functions [3]. While the pinch force produced using a passive tenodesis grasp is minimal, some hand function is possible even in the unoperated hand. During the first postinjury year, the tenodesis grasp is the basis for hand movement. Generally, surgical reconstruction of the hand is not recommended until approximately I year after trauma to allow neurological recovery and physical and psychological stabilization [4]. During this period, the patientcan experiment with new patterns of movement and learn how to use the impaired upper extremity. The primary goals of upper extremity rehabilitation are to maintain functional hand posture, prevent the development of contracture, and maintain passive range of motion [5]. Nonsurgical, acute therapeutic intervention provides the individual with an arsenal of basic functional skills. The strategies the patient develops during this period may be incorporated into the surgical plan for reconstructing hand function or may prove to be adequate for the individual's basic needs.
This article presents an overview of the musculoskeletal anatomy and function associated with the tenodesis grasp; describes how passive properties influence posture, movement, and function in the unoperated hand; discusses surgical enhancement of natural tenodesis; and provides insight into how individuals with severe loss of active control of hand muscles adapt to interact with their environment.

Langue : ANGLAIS

Tiré à part : OUI

Identifiant basis : 2003225784