Tendon and nerve transfers for spinal cord injury patients

The most common causes of spinal cord injury (SCI) are motor vehicle collisions, sports injuries, and falls. SCI patients are typically between 20 and 50 years of age.

SCI affects the upper motor neurons and causes either complete or incomplete loss of function below the point of injury. As a result, patients may have a range of physical and functional deficits. In patients with bilateral upper limb involvement, the sensory and motor deficits often differ on each side.

Many SCI patients seek restoration of upper extremity function to regain control over activities of daily living, such as self-grooming, eating, and self-catheterization. Restoration of grip facilitates the patient’s ability to use utensils, write, or push a wheelchair.

Caring for SCI patients requires collaboration among family or caregivers, hand surgeons, rehabilitation medicine physicians, occupational therapists, physiatrists, nurses, and social workers.

A good surgical candidate is one who is motivated, with realistic expectations for postoperative outcomes. It is essential that the hand surgeon understands which functions the patient wants to regain and discusses the goals of surgery in detail with the patient.

The patient must be emotionally and psychologically stable, with excellent social support, because they will be more dependent on caregivers immediately after surgery.

The patient should also recognize that a 4-week period of immobilization is typically necessary postoperatively, followed by an extensive occupational therapy regimen to learn how to activate and use the tendon transfers.

Surgery is typically performed at least 12 months after the injury so that the patient can accept the injury and maximize gains from therapy. In rare circumstances, some surgeons may perform reconstruction as early as 6 months after injury if motor improvement has plateaued, there is no concern for ascending myelopathy (neurologic deterioration above the initial injured site in tetraplegic patients), and patients have fulfilled the aforementioned requirements.

Reconstruction should be tailored based on the needs of the patient and the available donor muscles. The specific indications for certain tendon and nerve transfers are explained further in the following sections.

Tetraplegia can affect high cervical nerves (C1-C4) or low cervical nerves (C5-C8); the higher the level, the greater the severity of the functional deficits.

The Medical Research Council (MRC) System ( Table 69.1 ) is used to grade the patient’s muscle strength on a scale from 0 to 5.

The International Classification for Surgery of the Hand in Tetraplegia (ICSHT; Table 69.2 ) is used to develop treatment plans for individual patients. This system groups tetraplegic patients based on the number of functional muscles (grade 4 or 5 on the MRC scale) available below the elbow. The expected function for patients in each group is also listed.

Fig. 69.1 depicts the segmental innervation of all upper extremity muscles.

Common donor muscles for reconstruction of the upper extremity include:

• Brachioradialis (BR)

• Extensor carpi radialis longus (ECRL)

• Pronator teres (PT)

• Biceps

• Deltoid

Recipient muscles that are restored during reconstruction include:

• Triceps

• Extensor carpi radialis brevis (ECRB)

• Extensor pollicis longus (EPL)

• Flexor digitorum profundus (FDP)

• Flexor pollicis longus (FPL)

• Thenar muscle (Abductor pollicis brevis)

  • Interossei muscles

A thorough history is obtained to identify any preexisting medical conditions and to note the date of injury, method of injury, spinal cord injury level, and other associated injuries. A list of prior nonoperative (i.e., Botox) and operative procedures is also needed.

The upper extremity is evaluated for any preexisting spasticity or contractures, which are typically treated with antispasmodic medications (e.g., Baclofen) and occupational therapy.

The passive and active range of motion (ROM) of all joints including the shoulder, elbow, wrist, fingers, and thumb is assessed “top-to-bottom,” in the following order:

• Shoulder stability and abduction (deltoid function)

• Elbow flexion (biceps/brachialis) and extension (triceps)

• Wrist flexion (flexor carpi radialis [FCR]/flexor carpi ulnaris [FCU]) and extension (ERCB/ECRL/extensor carpi ulnaris [ECU])

• Finger flexion (flexor digitorum superficialis [FDS]/flexor digitorum profundus [FDP]) and extension (extensor digitorum communis [EDC]/intrinsics)

• Thumb interphalangeal (IP) flexion (FPL), extension (EPL), and opposition (APB)

Tenodesis describes the position of the fingers with respect to wrist position; when the wrist is passively flexed, the fingers should extend, and when the wrist is passively extended, the fingers should flex.

The following examination maneuvers are used to test and grade muscles according to Table 69.1 . Muscles with a strength of 4 or 5 are suitable donors and should be noted.

• Deltoid: Have the patient sit with arms at sides. The anterior, middle, and posterior deltoid heads are assessed when the patient raises the arm forward, lateral, and posterior toward the shoulder.

• Biceps: Have the patient flex the elbow against resistance, with the forearm in a supinated position.

• BR: The patient flexes the elbow against resistance, with the forearm in mid to full pronation.

• ECRB and ERCL: Have the patient actively extend the wrist; if both ERCL and ECRB are intact, wrist extension will be central because the ERCB inserts on the third metacarpal. If only the ECRL is intact, the wrist will radially deviate with extension because the ERCL inserts on the second metacarpal.

• PT: Have the patient sit with elbow flexed, passively rotate the forearm into supination, and ask the patient to pronate against resistance.

Assess proprioception by using a two-point discriminator with points set to different distances (6 mm, 8 mm, 10 mm, etc.). Alternatively, a paper clip can be opened to the different widths and used if a discriminator is not available.