Pathogenesis

The cervical spinal cord contains eight cervical segments encased in the seven cervical vertebrae. The bone and ligamentous structure of the cervical spine allows a wide range of motion, thus exposing the cervical spinal cord to increased risk of injury. Injury occurs most commonly through a flexion deformity with bone or disk compression of the cord after fracture or dislocation or through traction on the cord with translation due to spine instability. Over days and weeks, acute hemorrhage and edema subside, followed by local reparation and finally scar formation. The area of injured spinal cord can vary in width and length and is termed the injured metamere. Nerve function above the injured metamere is normal; nerve function within the injured metamere is absent; nerve function below the injured metamere may be stimulated if the lower motor neuron unit is unharmed.

The muscles that are innervated above the level of injury have normal strength. The muscles that are innervated below the level of injury may be flaccid or have some elements of spasticity. The strength of muscles at the level of injury may improve over time, most commonly within a year of injury. Ditunno and colleagues and Waters and associates reported upper limb strength recovery rates using manual muscle testing and the British Medical Research Council grading system ( Table 33.1 ). One third of muscles classified as grade 0 at 1 month after injury improved to grade 3 at 4 to 6 months after injury; improvement was documented in some cases up to 24 months after injury. All upper limb muscles with an initial strength of grade 1 improved to at least grade 3 by 1 year after injury, with the exception of the triceps. If a muscle’s strength was grade 2 or better at 1 month after injury, the median time for full recovery was 6 months.

Preoperative Evaluation

The reconstructive surgeon is less concerned with the specific level of cervical injury than with the remaining strength of each muscle in the upper limb. Classically, tetraplegic patients have been classified by the injured cervical spine segment of C1-C7. Formerly, it was assumed that the level of paralysis and sensory loss coincided with the bony injury, producing a precise transverse spinal cord lesion. Careful examination of tetraplegic patients has shown that there is frequently little relationship between the level of the skeletal lesion and the spinal cord lesion; lesions may be asymmetric, and there may be unusual patterns of spared sensory or motor function. A classification for spinal cord injury commonly used by surgeons other than hand surgeons is the American Spinal Injury Association (ASIA) classification. This classification is based on intact muscle groups.

The classification used in this chapter was developed by an international group of hand surgeons in 1978 in Edinburgh and modified in 1984 at Giens, France. The International Classification for Surgery of the Hand in Tetraplegia (ICS) grades the level of the spinal cord injury based on the number of muscles with grade 4 strength below the elbow and includes ICS levels 0 to 9 ( Table 33.2 ). The ICS level characterizes the most common patterns of presentation, based on the number of functional muscles below the elbow. A muscle is defined as functional if it demonstrates grade 4 or better strength by manual muscle testing.

Another aspect of patient evaluation includes assessment of the general suitability for surgery. An assessment based on age, occupation, interests, level of education, learning capacity, economic support, family and agency support, personality type, and understanding of what can and cannot be expected from surgical treatment needs to be explored with the patient and the spinal cord injury management team.

Physical Examination

After a thorough history of the injury and associated medical conditions is obtained, a physical examination is performed, including sensory and motor testing to establish the patient’s group (ICS level 0 to 9). Manual muscle testing (see Table 33.1 ) is performed on all muscle groups in the upper extremity. The surgeon can make a working list of which tendons are available for transfer (those having grade 4 strength or higher) and which muscles are paralyzed (those having grade 1 strength or lower). Once the muscles with grade 4 strength have been identified, the patient is assigned a group number (see Table 33.2 ). For example, a patient with grade 4 strength of the brachioradialis (BR), both radial wrist extensors, the pronator teres (PT), and the flexor carpi radialis (FCR) would be classified as a group 5 patient. One of the difficulties in physical examination is distinguishing between group 2 and group 3 injuries. In group 2 patients, only the extensor carpi radialis longus (ECRL) has strength of grade 4 or higher, and physical examination reveals significant radial deviation of the wrist with resisted wrist extension. In group 3 patients, both the ECRL and the extensor carpi radialis brevis (ECRB) have strength of grade 4 or higher. In a group 3 patient, the wrist extends with less radial deviation and often grade 1 to 3 strength is present in the PT, the next most caudal muscle. In thinner patients, the ECRL, a flat muscle, and the ECRB, a more bulbous muscle, can be palpated while muscle strength is being tested ( Figure 33.1 ).

To determine whether a patient is in group 2 or group 3, the physician can palpate the extensor carpi radialis brevis (ECRB), a long flat muscle, and the extensor carpi radialis longus (ECRL), a more bulbous muscle. In thinner individuals, both muscles can be palpated as muscle strength is tested (Bean sign). If the Bean sign is present, indicating that both the ECRL and ECRB are firing, and the patient has wrist extension strength of grade 4 or 5, the patient is in group 3, and the muscle belly of the ECRL can be palpated.

In addition to manual muscle testing, the surgeon must also examine the passive range of motion to evaluate joint and muscle contractures and the resting posture of the hand. The examiner can induce a tenodesis effect by passively flexing the wrist while observing passive myostatic tensioning of the digital extensors; the reverse effect of passive digital grasp can be induced with passive wrist extension. The hand must have passive mobility or tenodesis ability to achieve what the patient needs; for example, if the thumb rests in a fully supinated position and lacks any tenodesis for thumb flexion or opposition, tendon transfers will be ineffective without skeletal stabilization (carpometacarpal [CMC] fusion) in a key pinch position.

The next step is to determine the patient’s needs, as shown in Table 33.3 , and match the needs with the muscles available for transfer. For example, in a group 4 patient, the BR is available because the patient has the biceps and brachialis for elbow flexion (and, therefore, no function will be lost with the transfer); the ECRL is available because the patient has the ECRB for wrist extension. The PT can also be used for transfer, but this could result in diminished pronator power and loss of strength for manual wheelchair function. To complete the assessment, the muscles available for transfer (BR, ECRL) are matched with the needed functions (thumb extension and abduction, finger extension, thumb flexion and opposition, finger flexion, intrinsics) using principles of tendon transfer surgery (see Chapter 31 ), combined with other surgical options such as arthrodesis and tenodesis. In a group 4 patient, strength of grasp and pinch is deemed most important; thus the BR and ECRL are selected for finger and thumb flexion. The BR will be transferred to the flexor pollicis longus (FPL) because it has (and needs) less excursion, and the ECRL will be transferred to the flexor digitorum profundus (FDP) tendons, which need greater excursion. Surgical adjuncts will be used to pre-position the thumb in key pinch with a CMC fusion and to provide thumb and finger extension through an extensor pollicis longus (EPL) and extensor digitorum communis (EDC) tenodesis. If necessary, intrinsic reconstruction can be added during a second staged surgery if joint imbalance manifests. By evaluating what the patient has, what the patient needs, and what is available, the surgeon can determine the optimal combination of transfers and adjunctive procedures to restore function.

TABLE 33.3

Preoperative Workup for the Assessment of Muscle Strength Testing

Function Needed by the Patient	Muscles to Be Tested and Graded
Elbow flexion	Biceps, brachialis
Elbow extension	Triceps
Wrist extension	ECRL, ECRB, ECU
Wrist flexion	FCR, FCU
Finger extension	EDC, EIP, extensor digiti quinti
Finger flexion	FDP, FDS
Thumb extension/abduction	EPL, EPB, APL
Thumb flexion/opposition	FPL, APB, opponens, flexor pollicis brevis
Intrinsics	Adductor pollicis, interossei, lumbricals

 

APB, abductor pollicis brevis; APL, abductor pollicis longus; ECRL, extensor carpi radialis longus; ECRB, extensor carpi radialis brevis; ECU, extensor carpi ulnaris; EDC, extensor digitorum communis; EIP, extensor indicis proprius; EPB, extensor pollicis brevis; EPL, extensor pollicis longus ; FCR, flexor carpi radialis; FCU, flexor carpi ulnaris; FDP, flexor digitorum profundus; FDS, flexor digitorum superficialis; FPL, flexor pollicis longus.

Pertinent Anatomy

Injuries of the spinal cord produce a different nerve deficit than do central nervous system deficits, brachial plexus injuries, or isolated peripheral nerve injuries. The pattern seen with a spinal cord injury is based on segmental innervation; this concept means that the anterior horn cells in the spinal cord are arranged in a pattern from cephalad to caudad. Motor nuclei form longitudinal columns crossing several segmental levels, innervating the peripheral musculature in a predictable manner.

Figure 33.2 shows the segmental anatomy, based on Zancolli’s clinical experience with tetraplegic patients. When a spinal cord injury occurs, the motor nuclei cephalad to the injury will be functional; the motor nuclei at or caudad to the level of the injury will be nonfunctional.

Segmental innervation of muscles of the elbow, forearm, and hand. Although not shown in this figure, the deltoid and biceps are both innervated from the C5-C6 level. Both the deltoid and the biceps receive their innervation from a higher level on the cervical cord than the triceps.

(See Zancolli EA: Structural and dynamic bases of hand surgery , ed 2, Philadelphia, 1979, JB Lippincott.)

Historical Review

Before the 1960s, the poor prognosis and low survival rate of patients with spinal cord injury precluded the need for upper extremity reconstruction. As the prognosis and medical care of patients with spinal cord injury improved, so did the surgical advancements in tendon transfer surgery. As shown in Table 33.4 , advancements in tendon transfer surgery that were initiated by Bunnell were applied to tetraplegic patients by Moberg, Lamb, Zancolli, and Freehafer. Patients and physicians are now enthusiastic about the potential benefits of a well-designed and well-executed surgical plan for upper limb reconstruction in those with tetraplegia.

In addition to hand surgery reconstruction, significant research on and clinical treatment with a neuroprosthesis was performed from the 1980s to the 2000s. The use of electrical current for muscle stimulation in patients with spinal cord injury led Keith and associates at Case Western University to develop a fully implantable functional neuromuscular stimulation neuroprosthetic system. This technology takes advantage of paralyzed muscles that are no longer under cortical control (due to spinal cord injury) but have intact spinal reflex arcs. The anterior horn cell of the motor units for eligible muscles must be uninjured to preserve the spinal reflex arc; the muscles are generally located below the level of the direct spinal cord injury. These muscles can be stimulated to contract with relatively weak electrical currents. Muscle signals, nerve signals, or volitional movements (above the level of spinal cord injury), typically from the contralateral shoulder or neck, are used to control the device.

The neuroprosthesis is indicated for tetraplegic patients for whom standard surgical procedures or orthotic devices cannot provide useful improved function or who have exhausted these options. Most commonly, the neuroprosthesis is implanted in patients in groups 0, 1, 2, and 3. More than 250 adults and children have received the neuroprosthesis system worldwide. As of 2008, the company that manufactured the device discontinued its production; second-generation 12-channel devices with telemetry and myoelectric control are available under research protocols and have shown promise in achieving independent two-handed use.

Indications and Contraindications for Operative Intervention

The goal of tetraplegic hand reconstructive surgery is to increase the patient’s independence; thus, the indication for operative treatment is functional impairment that can be improved through surgical reconstruction. Candidates for surgery include patients whose injury occurred at least 12 months ago, who have a stable upper extremity motor examination, and whose functional impairments can be improved by hand reconstruction. Ideally, the patient is free from contractures, pain, and spasticity; has the ability to comply with the postoperative rehabilitation regimen; has appropriate postoperative support services available; and is highly motivated to improve hand function. It is also critical that the patient be medically stable, including bowel and bladder function, blood pressure control, and no urinary tract infection or decubitus ulcers.

Two factors have had a uniformly adverse effect on the results of surgical treatment: spasticity and psychological problems. Spasticity that cannot be controlled by the patient is a strong contraindication to surgery. Freehafer and colleagues and Moberg stated that some spasticity might be helpful, but judging the degree of spasticity that is compatible with good results is very difficult; in fact, Moberg noted such an error in his poor results group. Psychological impairment, unrealistic expectations, insufficient motivation to complete the operative and postoperative protocols, and inadequate social support mechanisms should be assessed before surgery. Patients who want to have reconstructive surgery and are strongly motivated to improve their functional status are more likely to obtain a better outcome. The surgeon and patient must be able to communicate effectively and share realistic expectations of the benefits of surgery. Allowing a prospective patient to visit a postoperative patient with a similar condition is particularly useful.

Tendon Transfer

Provided that the patient has adequate voluntary muscle control and strength of potential donor muscles, tendon transfers are preferred over tenodesis or arthrodesis because these restore active control and strength. However, the primary problem after spinal cord injury is a paucity of adequate donor muscles available for transfer. It is critical to ensure that sacrifice of a potential donor muscle for transfer will not create another functional deficit. The available muscles are prioritized first for wrist extension, then for pinch, then for grasp, and finally for release functions. Tendon transfer principles, including donor availability, donor strength, amplitude of excursion, passive mobility of recipient joints, and condition of the soft tissue bed, must be followed (see Chapter 31 ). When transfer options are exhausted, remaining hand functions are achieved through tenodesis and/or arthrodesis.

Tenodesis

Tenodesis is defined as the movement of one joint produced by the motion of an adjacent (usually proximal) joint. For instance, with active or passive extension of the wrist, the fingers and thumb spontaneously flex; with wrist flexion, the fingers and thumb extend. Although the finger and thumb muscles are paralyzed, there is sufficient remaining myostatic tension to induce reciprocal action of the digital flexor and extensor tendons that cross the wrist joint. Spinal cord injury patients learn to use the tenodesis effect naturally and commonly have functional but very weak pinch or grasp owing to the tenodesis effect alone. The tenodesis effect can be enhanced surgically without the need to transfer an active muscle. Passive tenodesis procedures anchor the paralyzed tendon proximal to the wrist joint to decrease effective tendon excursion and thus increase digital movement with active wrist movement. Common tenodesis techniques include those for finger flexion and extension, as well as for thumb flexion, extension, and abduction. Tenodesis can also be used to improve function of the intrinsic muscles of the fingers and thumb.

Arthrodesis

Arthrodesis is useful in the thumb to make this multiarticular joint more stable and easier to control. Combinations of tendon transfers and tenodesis procedures can be used at the CMC, metacarpophalangeal (MP), and interphalangeal (IP) joints to provide effective positioning and control of the thumb to produce pinch function. Particularly in the index finger, proximal interphalangeal (PIP) joint fusions can be used to stabilize a digit to provide a post for pinch. The wrist is never fused because the tenodesis effect would be lost. Surgical techniques for arthrodesis are no different in the paralytic hand; when possible, rigid fixation should be chosen to allow some weight bearing and early mobilization for tendon transfer rehabilitation.

Surgical reconstruction is based on the patient’s International Classification group (see Table 33.2 ). Elbow procedures are presented first, followed by procedures used for grasp, pinch, and release.

Biceps to Triceps Tendon Transfer

The biceps to triceps tendon transfer is my preferred method for establishing elbow extension ( Figure 33.3 ). The biceps is used as the donor muscle. To ensure that function will not be lost with transfer of the tendon, the strength of the brachialis as an elbow flexor and of the supinator as a forearm supinator must be verified before transfer. Manual muscle testing is performed, testing elbow flexion, attempting to isolate the brachi­alis by supinating the forearm, and allowing relaxation of the biceps. This can be verified by palpating the groove between the more tubular biceps anteriorly and the flatter brachialis posteriorly to differentially test strength. In reviewing the segmental innervations of the upper limb from the spinal cord (see Figure 33.2 ), note that the biceps, brachialis, and supinator are all innervated at about the same level (C5-C6). If the patient has strong wrist extension, the spinal cord lesion should be below C6, sparing the biceps, brachialis, supinator, and wrist extensors, but above the innervation of the paralyzed triceps. Such findings on clinical examination verify that transfer of the biceps will not lead to a functional loss. Electromyography is generally not necessary as part of the routine evaluation.

Biceps to triceps transfer. A and B , The biceps tendon (BT) and bicipital aponeurosis (BA; lacertus fibrosus) are released, and the muscle belly is mobilized proximally through an anterior incision. C and D, The biceps is rerouted medially around the arm in the subcutaneous plane and inserted by braiding the tendon “tails” into the triceps tendon. E , Direct insertion of the biceps tendon into a bone tunnel in the olecranon, with heavy sutures tied over bone. This provides strong fixation, permitting relatively early mobilization.

The biceps to triceps tendon transfer can be performed using a medial or a lateral routing technique. The lateral technique was first described by Friedenberg in 1954 and later reported by Zancolli. No loss of active elbow flexion was noted, although flexor strength was diminished by 24%. In 1988 Ejeskar reported his results using the lateral routing technique in five patients, including the first complication of radial nerve palsy. Because the radial nerve is the only functioning peripheral nerve in these patients, such a complication is devastating and has subsequently been noted by others using the lateral routing technique. Thus, medial routing is strongly preferred.

The procedure is performed with the patient supine, a roll under the operative shoulder blade, and the limb draped free with a sterile tourniquet high on the arm. The incision extends from the midhumerus on the medial side, transversely across the antecubital crease, and courses distally, centered over the biceps insertion on the radial tuberosity. The lateral antebrachial cutaneous nerve is identified and protected as the biceps tendon is dissected free from its medial and lateral fascial attachments and sharply dissected off its insertion on the bicipital tuberosity. The lacertus fibrosus is freed from the forearm fascia during the dissection and is preserved as a second tail of the biceps tendon for subsequent weaving. The muscle is raised proximally, with care taken to preserve the musculocutaneous nerve running on the surface of the brachialis muscle.

A second (posterior) incision is made over the distal one third of the triceps tendon, passing lateral to the olecranon to avoid subsequent olecranon pressure ulceration and allowing an adequate skin bridge with the medial incision. A subcutaneous tunnel is made medially from the anterior wound to the posterior wound, creating a line of pull that is straight and free for medial rerouting of the biceps. The medial intermuscular septum may need to be partially resected, and care is taken to protect the neighboring ulnar nerve. The biceps tendon is passed from the anterior wound into the posterior wound, superficial to the ulnar nerve. A bone tunnel is created in the tip of the olecranon with a drill bit of 4 to 8 mm to receive the terminal end of the biceps tendon. The biceps length usually allows two or three weaves through the triceps tendon before it is inserted into the olecranon drill hole. A No. 5 nonabsorbable grasping suture is placed into the end of the biceps tendon and passed through the bone tunnel using Keith needles, tying the grasping suture over bone.

The transfer is tensioned to allow 60 to 90 degrees of passive elbow flexion. The lacertus fibrosus is interwoven through the biceps to triceps weaves to further secure the tendon weave. Postoperatively, the elbow is placed in about 30 degrees of flexion in a long-arm cast for 4 weeks. A flexion block splint (hinged elbow orthosis) is then used full time, and 15 degrees of flexion is added each week until full flexion and adequate arm control are achieved. Strengthening exercises are then added.

The strength of the biceps to triceps transfer continues to improve for at least a year, resulting in substantial improvements in performing activities of daily living. Published series have reported functional improvements for overhead, reaching, and driving activities. No clinical loss of active flexion has been reported, although flexor strength was diminished by 24% in one series. Mulcahey and coworkers published a randomized prospective comparison of posterior deltoid to biceps transfer versus biceps to triceps with medial routing transfer. These authors reported that at 2 years, seven of eight arms treated with biceps to triceps transfer had antigravity use of the arm, whereas only one of eight arms treated with posterior deltoid to triceps transfer had antigravity use of the arm.

Posterior Deltoid to Triceps Tendon Transfer

The posterior deltoid to triceps transfer uses the posterior third and the posterior half of the middle third of the deltoid muscle as a donor to provide active elbow extension ( Figure 33.4 ). An interposition tendon graft is used, and the triceps tendon serves as the insertion. The posterior deltoid is tested before surgery by supporting the limb in 90 degrees of shoulder abduction and palpating the muscle for bulk and selective control while testing the strength of shoulder extension. Scapular stabilization and control are also necessary to maximize the effectiveness of the transfer.

Deltoid to triceps transfer. A, The posterior border of the muscle belly is isolated, preserving as much of the tendinous insertion as possible. B, Tendon grafts are laced into the distal end of the deltoid muscle belly and triceps aponeurosis. C, Fascia lata is used rather than tendon grafts. Direct insertion into the olecranon through a bone tunnel can be performed with either type of graft.

(Copyright © Elizabeth Martin. See also Moberg EA: Surgical treatment for absent single-hand grip and elbow extension in quadriplegia. J Bone Joint Surg Am 57:196–206, 1975.)

The procedure is performed with the patient in a lateral decubitus position with the shoulder forequarter draped free. An incision is made from the tip of the posterior corner of the acromion distally to the deltoid tubercle insertion. Dissection is along the posterior border of the deltoid, leading into its insertion onto the deltoid tubercle. The axillary nerve courses about 5 cm distal to the acromion on the deep surface of the deltoid and must be protected as the posterior half of the middle deltoid is dissected with the posterior deltoid and freed from its insertion. A separate incision is made over the distal one third of the humerus to expose the triceps tendon. A subcutaneous tunnel is made, connecting the two incisions for placement of an interposition graft.

Several alternatives exist for the interposition graft. Moberg originally used toe extensors from the second, third, and fourth toes to allow at least three weaves at each attachment site. Alternative graft materials have included fascia lata, tibialis anterior, and extensor carpi ulnaris (ECU). Alternatively, Castro-Sierra and Lopez-Pita used the central one third of the triceps. In this method, a 1-cm strip from the central one third of the triceps is harvested from its insertion in a retrograde manner (proximally based), mobilizing it sufficiently to graft back to the distal end of the posterior deltoid. Reflecting the central third of the triceps with a bone block and internally fixing this to a bone block from the deltoid insertion has also been described.

After the interpositional graft has been placed, the transfer is sewn into place and tensioned with the shoulder in 30 to 40 degrees of abduction and no forward flexion, so that the elbow can flex to 60 degrees with moderate tension. Most commonly, a well-padded long-arm cylinder cast is applied to hold the elbow in about 10 degrees of flexion. The wrist can be left free. Forward flexion and shoulder adduction are avoided during the 6 weeks of cast immobilization. Gentle active exercises are performed to slowly gain elbow flexion for the next 3 months with a rate of 5 to 10 degrees of increased flexion per week.

Posterior deltoid to triceps transfers are compromised by the prolonged shoulder and elbow immobilization required postoperatively, as well as tendon graft elongation over time. Elongation of the tendon graft leads to decreased strength over time. Friden and colleagues used intraoperative metal markers at the ends of the tendon grafts and measured an average of 2.3 cm of elongation after 2 years. They changed their postoperative regimen to include longer elbow extension immobilization, and increased shoulder abduction. Follow-up of five patients using this regimen using the same markers averaged 0.8 cm.

Biceps Rerouting Procedure

The biceps is rerouted from a supinator moment arm wrapping counterclockwise around the proximal radius, to a pronator moment arm wrapping clockwise around the proximal radius ( Figure 33.5 ). This procedure can be done in isolation or in combination with one of the hand reconstructive procedures listed below. Indications for surgery are passive mobility of the forearm into pronation, without active pronation, as well as a biceps tendon of grade 5 strength that is a deforming force as a supinator leading to dysfunctional supination posturing. The biceps needs to be available for transfer, but not for transfer to the triceps to provide elbow extension strength.

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