An injury to the upper part of the spinal cord can leave an individual with little or no sensation or movement in both the arms and the legs, a condition called tetraplegia (tet-rah-PLEE-gee-ah). A surgical technique called a tendon transfer can help restore function to arms and hands by giving working muscles different jobs.
This can greatly enhance the quality of life for people with tetraplegia by enabling them to do many more tasks for themselves. The types of tendon transfer surgeries that can be performed depend on where the spinal cord injury occurred and which muscles are affected.
How it works
Tendons are the strong cords that connect muscle to bone. When a tendon crosses a joint, it helps transmit muscle action into joint movement. A tendon transfer repositions the tendons of a working muscle so that they take over the functions of a paralyzed muscle. This enables the working muscle to do what the paralyzed muscle can no longer do.
For example, in the upper arm, the triceps muscle is used to straighten the elbow. The larger deltoid muscle pulls the arm backwards and forwards away from the body. If the triceps muscle is paralyzed but the deltoid is still functional, surgeons can split the deltoid muscle and graft a portion of it to the triceps. This restores elbow function without greatly diminishing shoulder function.
Tendon transfers can help restore three critical capabilities necessary for self-care and increased independence:
- the ability to straighten (extend) and bend (flex) the elbow
- the ability to bend and straighten the wrist
- the ability to grip with the fingers and hand
Planning for a tendon transfer
Usually, a tendon transfer is not scheduled until about a year after injury. During the first months after the injury, rehabilitation focuses on retaining passive range of motion. These exercises help prevent shoulder stiffness and pain. As time progresses, strength and range of motion (both active and passive) must be evaluated frequently. Severe muscle contractures or muscle spasms may necessitate another type of surgery rather than a tendon transfer. Usually tendon transfer surgery is scheduled only after there is no more progress in function.
Before surgery is scheduled, several assessments must be made, including:
- identifying which muscles still work and measuring how well they work to determine whether they can be used in the transfer
- assessing the individual’s abilities to see which functions need to be restored
- matching available muscles with functional requirements
- determining if an additional procedure such as a joint fusion or electrical stimulation implant is needed to restore function
- verifying that the individual has a strong support system that can provide the care needed during rehabilitation after surgery
- assessing the individual’s motivation and commitment to the process
- determining which surgeries should be performed, when, and in what order
Elbow Extension
The ability to bend and straighten the elbow adds greatly to a person’s independence, so this is often the first surgery to be performed. In most cases, a portion of the deltoid muscle in the shoulder is used to provide elbow extension. The back (posterior) portion of the deltoid is brought down toward the elbow. Because the deltoid portion is not long enough to reach the attachment point in the lower arm, a graft is taken from an upper leg muscle (fascia lata) to provide the necessary length.
In some cases, the biceps muscle in the upper arm is used instead of the deltoid muscle. After the surgery, the arm is immobilized in a slightly bent position for up to four weeks. When the cast is removed, a hinged brace is used to allow a gradual stretching and strengthening of the muscles. Initially, the brace is worn night and day, but as the individual gains the ability to fully extend the arm, the brace is worn only at night.
Tendon transfer to achieve elbow extension is done on one arm at a time because the arm is totally immobilized during rehabilitation. This means that the person becomes even more dependent on others for the simple activities of daily living. However, the results are impressive. It can eliminate the need for many adaptive devices and enable the person with tetraplegia to propel a wheelchair, to move independently from bed to chair, to shift weight within a chair or bed and to reach up and outwards.
Key Pinch
Restoring key pinch enables the individual to grip items between the thumb and the hand. This greatly enhances the ability of the patient with tetraplegia to accomplish activities of daily living, such as writing or feeding themselves. In this surgery, one of the forearm muscles (brachioradialis) is grafted to the tendons that move the wrist and thumb. The surgeon may also stiffen the joint so that when the wrist is extended, the grip forms automatically.
These two surgeries significantly improve hand and arm function in many patients, providing them with much greater independence.
Electronic Implants
A relatively recent advance uses an electronic implant, similar to a pacemaker, to stimulate muscles. Tiny electrodes are attached to the functioning muscles of the arm and hand. The electrodes are connected to a control device implanted in the front of the chest. An external unit delivers the signals to initiate grasp and key pinch. This is an option when tendon transfers cannot be used.
Outcomes
Because tendon transfers use the patient’s own tissues, the risk of infection is lessened. However, the risk of developing a latex allergy is increased so precautions should be taken. The length of the surgery (approximately six hours) also increases the risk of postoperative respiratory problems.
In general, the results using tendon transfer surgery to restore arm and hand function after spinal cord injury are good. People with tetraplegia can often benefit from the increased self-confidence and independence they gain after tendon transfer surgery.