Introduction
The annual incidence of spinal cord injury (SCI) is highly variable between different regions and countries. A systematic search using multiple sources (e.g., PubMed, EMBASE, Cochrane Database of Systematic Reviews) demonstrated that the incidence, prevalence, and causation of SCI differs between developing and developed countries. Further, the study suggested that management and precautionary strategies need to be tailored to trends also at the regional level. In the United States, the annual incidence of SCI is approximately 54 cases per one million people. Vehicle accidents and falls are responsible for more than 70% of the cases. Tetraplegia represents roughly 60% of the SCI, and recently incomplete tetraplegia is the most common neurological category. The increase of incomplete tetraplegia presents a particular challenge for reconstruction strategies of hand function. In Westernized countries, the rising age of the population indicates that traumatic SCI secondary to falls is an increasing public health challenge and that incidence among the elderly may rise with longer life expectancy.
Regaining hand function is a highly prioritized objective for most of the patients with cervical SCI and tetraplegia. , The benefits and risks of undergoing surgery are considered acceptable by individuals living with tetraplegia. Usually, the goal can be reached by transferring muscles innervated above the level of the lesion to nonfunctioning key muscles innervated by lower motor neurons deriving from below or at the level of the lesion.
Individuals living with tetraplegia who still have adequate functioning upper-extremity muscle(s) can usually achieve improved hand function through surgical reconstruction. Only the affected person knows exactly what performance goals are needed to become more independent. Thus it is imperative to carefully consider how the individual’s specific functional desires and outcome expectations fit with the given conditions to achieve these goals. The advanced surgical options available to accommodate specific functions require deep communication between the patient and surgeon/caregiver as well as a functioning health care infrastructure to achieve the best possible outcomes ( Box 32.1 ).
“Tetrahand World Congress, Philadelphia, 2007”
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Outcome of surgery must mean significant improvement of patient’s abilities.
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All patients should have the right to be assessed by an experienced hand surgeon.
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Surgery must be performed using modern strategies aiming at voluntary control of key functions.
Specific needs such as “be able to write by hand,” “dress myself,” “drive my manual wheelchair,” “control the steering wheel,” and “catheterize myself” make it easier to analyze the detailed components of these motions. Analysis of combined and more complex movements, for example, sports, provides a better basis for dialogue about how well surgical procedures and postoperative training can achieve the prioritized goals. This approach places greater demands on surgeons and the rehabilitation team and will result in greater patient satisfaction. If for any reason there is a discrepancy between the patient’s wishes and the surgeon’s predicted outcome, the surgery may best be not performed. Conversely, when the necessary prerequisites are present, there is a variety of surgical options available depending on the level and type of lesion as well as the pattern of muscles retained under full or partial voluntary control. Normally, every patient considered for surgical reconstruction will be assessed according to the International Classification for Surgery of the Hand in Tetraplegia (ICSHT) ( Table 32.1 ).
| Group | Remaining Function | Spinal Level |
| 1 | Brachioradialis | C5 |
| 2 | 1 + ECRL | C6 |
| 3 | 2 + ECRB | C6 |
| 4 | 3 + Pronator teres | C6 |
| 5 | 4 + FCR | C7 |
| 6 | 5 + EDC | C7 |
| 7 | 6 + EPL | C7 |
| 8 | Partial digital flexion | C8 |
| 9 | Lacks only intrinsics | Th1 |
| X | Exceptions |
This classification refers to the number of muscles below the elbow available for muscle-tendon transfer (Medical Research Council [MRC] ≥4) for each group. For example, in ICSHT group 1, only the brachioradialis (BR) is available, and wrist extension is absent or impaired (MRC ≤3). Typically, this patient would be offered a transfer of the BR to the extensor carpi radialis brevis (ECRB) to restore wrist extension. Additional procedures in surgery would be suturing the flexor pollicis longus (FPL) to the radius for passive key pinch and reconstruction of passive intrinsics to ensure metacarpophalangeal joint flexion and proximal interphalangeal joint extension of at least the index and middle fingers. Opening of the hand would be achieved by gravity-driven wrist flexion combined with extensor pollicis longus (EPL) tenodesis to the distal forearm fascia in addition to the tenodesis for fingers (see “Restoring Intrinsic Balance” in this chapter).
The reintroduction and popularization of nerve transfer in tetraplegia has widened the possibilities but also the complexity of assessments in planning of restorations. Consequently, the roadmap for reconstruction has changed and requires continual reevaluation and updates of restoration strategies for hand and extremity functions. This chapter will present essential clinical findings, different treatments, the clinical treatment of spasticity, and current investigations.
Essential clinical findings and strategies
Clinical presentations
Persons with tetraplegia present with a wide spectrum of motor and sensory losses depending on the level and type of lesion, the degree of completeness, and the distribution of the lesion.
A sub C7 lesion typically permits extensive opportunities for reconstruction of many key functions. Conversely, a complete sub C4 SCI injury with only accessory nerves available for transfer presents limited options for upper-extremity muscle reanimation. From a diagnostic and prognostic point of view, the patient with complete transection of the cervical spinal cord is usually the most straightforward to evaluate, and the reconstruction options available are usually better defined. For the highest, complete lesions (C4-C5) considered for upper-extremity reanimation of motor functions, awareness of the risk of interfering with phrenic nerve functions must be considered. This patient group may be dependent on auxiliary breathing muscles, which would exclude the anterior portion of the axillary nerve for transfer. The other extreme of SCI lesion (C8-Th1) also requires a cautious approach, but for other reasons. This group of patients maintains many of their hand functions. Although they satisfactorily can perform many normal activities, the fine-tuning of hand movement may be missing because of lack of intrinsic control. Any surgical intervention for patients in the “low level” cervical SCI group must be carefully tailored to add exactly the key function (intrinsic balancing) needed without interfering with existing functions. This is an intricate decision as well as a delicate planning and challenging reconstruction that must be performed by surgeons with a solid knowledge of the physiological effect of their personalized interventions in patients with tetraplegia.
Impairment scale.
The ASIA (American Spinal Injury Association) impairment scale may be helpful to understand the complexity of the wide range of clinical presentations SCI. The scale delineates and categorizes the different types of completeness of the lesions. AIS A marks a complete lesion, whereas AIS B, C, and E correspond to degrees of incomplete injuries. Particularly AIS D and E may be challenging from a reconstruction point of view because of their variability in both sensory and motor pattern but also potential for improvement and access to motors available for transfer.
Lack of sensation in the hand and upper extremity.
Undoubtedly, sensory loss in the hand is a troubling factor in many patients living with tetraplegia. However, most of our patients considered for surgical reconstruction belong to the SCI level of lesion C6 and present retained or partial innervation in the median nerve distribution. It is essential for the outcome of a grip reconstruction that at least the thumb and index finger have some sensation preserved. After grip reconstruction, many patients report improved sensation, probably due to the enhanced sensory-motor feedback after increased use. Conversely, lack of sensation is no contraindication to surgery in patients with intact vision. A restored grip function provides an important motor skill and facilitates daily life even with markedly limited or absent sensation. However, the concomitant dryness of skin reduces friction and requires extra attention when grasping objects.
Surgical options, therapy, and combined treatment approaches
Although the nerve transfer concept to restore functions below the level of a SCI lesion is not new, it was not until 10 to 15 years ago that multiple nerve transfer studies appeared and demonstrated successful reinnervation of different target muscles after nerve transfers in tetraplegia. These promising results have broadened our horizon about strategizing surgical reconstructions and have challenged our traditional approaches. Yet, both tendon transfers and nerve transfers have limitations that must be considered. Moreover, in selected cases it appears reasonable to wait on the outcome of nerve transfers that sometimes may take 2 years. Subsequently, and depending on the success of reinnervation, tailored tendon transfer procedures can be conducted to achieve maximal functional outcome. This approach has certainly its drawbacks because of the time delay until complete, partial, or absent reinnervation will be evaluated. Conversely, when it is successful, a nerve transfer provides the patient with more versatility in motor control of the restored extrinsic muscle functions than what can be accomplished by tendon transfers. The current treatment techniques are summarized in Box 32.2 .
- 1.
Muscle-tendon transfers: Improve thumb, finger, and wrist function.
- 2.
Nerve transfers: 6–8 months after injury, to repair muscle function.
- 3.
Tenodeses: Improve hand function and balance of muscle powers.
- 4.
Joint fusions: Used for thumb only.
- 5.
Capsulodeses: Correct joint position.
- 6.
Myo-tenotomies: Correct joint position and increase joint motion.
- 7.
Tendon lengthening: Correct joint position and increase joint motion.
- 8.
Muscle releases: Correct joint position, increase muscle power and joint motion.
The combined approach to reconstruction is delicate. Of course, it would be desirable to accurately predict the outcome of nerve transfers and perform the necessary tendon transfers during the same operation. Unfortunately, this approach would be too risky from a balancing point of view and must be avoided. Nevertheless, accurate diagnostic procedures increase the chance of successful planning and outcomes whether nerve transfers are combined with tendon transfers.
Current diagnosis and treatment
Improved diagnostics in planning nerve transfer surgery
Muscles innervated from the level of the lesion lack neural connections to the spinal cord, are typically nonreflexive, and are unexcitable via nerve stimulation. The lesion is classified as a lower motor neuron lesion. Muscles innervated from below the level of the complete lesion are inactive. They are, however, reflexive and electrically excitable, and the lesion is referred to as a upper motor neuron lesion. All muscles and functional groups have multiple root innervations and multiple peripheral nerve overlaps effect intricate combinations of innervation, atrophy, and recovery potential.
We believe that more accurate mapping of motor endplate integrity will allow even more precise selection of muscles with intact lower motor neurons and thus better functional outcomes after nerve transfers. A feasible method for daily practice using pen electrodes is demonstrated ( Fig. 32.1 ).
Surgeons should be cautious about transferring nerves to denervated or partially denervated muscles. These muscles should be avoided as targets for nerve transfers or should be subjected to pretreatment with electrical stimulation to preserve/restore the structural integrity of motor endplates and contractile muscle components before nerve transfer is considered. Nerve conduction studies appear to better predict lesion patterns in SCI than electromyograms. Furthermore, a much higher proportion of denervated muscles seem to be present in flexor muscles (flexor digitorum profundus [FDP] and flexor pollicis longus [FPL]) than extensor muscles (extensor digitorum communis [EDC], EPL, and extensor carpi ulnaris [ECU]). The reason for that discrepancy remains unclear. For the nerve transfer substituting finger flexion and extension, we therefore suggest a decision strategy ( Fig. 32.2 ). To improve the incidence of success and the predictability of neurotization, it is advisable to select nondenervated target muscles. Such muscles would show noteworthy muscle contraction when the motor points are electrically stimulated at low intensity. A recent, retrospective review of prospectively collected data in patients with SCI determined various zones of injury via electrodiagnostic assessment to predict motor outcomes after nerve transfers in tetraplegia. The study illuminated the relationship of the preoperative innervation zones to final motor outcomes after nerve transfer and concluded that electrodiagnostic studies can be used to tailor surgical strategies for nerve transfers in patients with tetraplegia. To predict motor outcomes, the authors also proposed an algorithm for augmenting nerve transfer plans based on the understanding the zones of injury and the integrity grade of the donor and recipient nerves ( Fig. 32.3 ).
Even with optimal outcomes of nerve and tendon transfer or combinations of both, many challenges exist. They relate mainly to the level and type of lesion, the degree of completeness, and the distribution of the lesion. For example, a sub C7 lesion typically permits extensive opportunities for reconstruction of many key functions. Conversely, a complete sub C4 SCI injury with only accessory nerves available for transfer presents limited options for upper-extremity muscle reanimation.
Regardless of the reconstruction strategy selected, restoration of intrinsic function requires special attention. Not only should an intrinsic minus finger position be avoided, but also the position and trajectory of the thumb for pinch and hand opening should be optimized. Reconstruction of intrinsic function is still a major challenge, and when not carefully addressed, the outcome of an entire reconstruction may be jeopardized.
Additionally, patients with incomplete lesions (AIS B-D) present frequently with spasticity, soft tissue swelling, increased general muscle tone, and greater risk of developing muscle and joint contractures. Surgical intervention in this group requires special precautions and planning and is usually performed only after the condition is stable and noninvasive treatment has reached an endpoint. In this chapter, we summarize the current diagnostic and surgical treatment strategies to restore hand function after SCI. The following focus areas are included: recent advances in nerve transfer surgery, securing intrinsic balance, reconstruction options in patients with spasticity, and the potentials for neuroprostheses and neuromodulation.
Nerve transfers
Nerve transfers have been successfully used to reconstruct elbow extension, wrist extension, grasp, pinch, and hand opening after mid-cervical SCI. Nerve transfers have expanded the reconstructive options for the restoration of function in the upper extremity by adding new motor donors to the pool already available through tendon transfer surgery. The addition of these nerve donors increases the number of functions that can be reconstructed and provides a nerve transfer alternative to traditional tendon transfer reconstructions. This occurs while keeping those tendon transfer donors intact for add-ons and salvage and enables reanimation in higher levels of SCI. , ,
Timing of surgery.
Timing of surgery, level of injury, and recognition of nerve injury pattern (including the degree of lower motor neuron injury in donor nerves and the degree of upper versus lower motor neuron injury in recipient nerves), patient selection, patient goals for each hand, nerve transfer selection, an understanding of how to combine nerve and tendon transfers, and a plan for salvage are important considerations in planning successful nerve transfer surgery.
Indications.
The ideal patient for nerve transfer surgery post-SCI is cognitively intact and motivated to participate in surgery and rehabilitation, is 6 to 9 months post-SCI, has a C6 and/or an ICSHT group 4 or lower level of injury with slender limbs and supple joints, and is without complicating features such as spasticity or concurrent peripheral nerve or brachial plexus injury. Nerve transfers in lower-level spinal cord injuries have superior power outcomes. As the motor level of injury descends farther down the spinal cord, there is an increase of between one and two MRC grades of recipient muscle power.
Donor nerves.
The best donor nerve is one where its innervated muscle has a MRC grade of 5 and, once spinal shock has dissipated, has always functioned at near or full power. Donor nerves that are anatomically close to the recipient nerve target do better. Depending on availability of nearby functional nerves upon examination, a donor nerve can be decided. For example, the nerve to the ECRB or the nerve to the supinator transferred to the anterior interosseous nerve (AIN) result in greater grasp and pinch power than when the more proximal nerve to the brachialis is used. , , The supinator to posterior interosseous nerve transfer (S-PIN) is used to restore hand opening needed for placing the hand for grasping and releasing objects. Use of the hand in the open position is important for social interaction (handshake, touch) and self-care (washing, wiping) as well as for use of electronic devices.
On intraoperative stimulation of the donor nerve, a low stimulation threshold of 0.5 mA and a strong contraction of the muscle through more than 50% of its passive range are positive prognostic indicators for power outcomes. If surgery is performed early, ideally 6 to 9 months post-SCI, then a poorly or nonresponsive recipient nerve on intraoperative stimulation is not necessarily a contraindication for nerve transfer, but a recipient that responds with a strong contraction to intraoperative stimulation will result in more power in the reanimated muscle.
In patients with a less than ideal clinical picture, some restoration of function is better than none. These patients should also have the opportunity to discuss their reconstructive options with the treating team emphasizing a more guarded prognosis. The bilateral nature of SCI ensures that the motivated patient will take advantage of every small gain afforded them. Even MRC grade 2 recovery may offer some functional and positional improvement. For example, elbow extension across gravity expands the working space of the hand and helps to stabilize the movement of elbow flexion. However, nerve transfers in individuals who have recovered from a C4 to a C5 motor level of injury, thus theoretically making them candidates for nerve transfer surgery, should be offered nerve transfers with caution and where muscle donors allow tendon transfers used instead. It is important that authors reporting on outcomes for nerve transfer surgery in SCI clearly document the injury level as well as the time from injury to surgery so that an accurate comparison of results can be performed.
Although early nerve transfer surgery (6–12 months post SCI) is preferable, certain individuals may be candidates for delayed (≥18 months post SCI) surgery. Where the injury to the recipient neuromuscular unit is predominantly of an upper motor neuron pattern, nerve and neuromuscular junction health is maintained through spinal reflexes, which extends the timeframe after injury when nerve transfers can be successful to many years. The single most important clinical predictor of delayed nerve transfer success is a strong, full range of contraction of the proposed recipient muscle on stimulation with surface or point electrodes.
The addition of nerve transfers in the treatment of SCI is exciting and rapidly evolving. Further work with respect to late nerve transfer surgery, reconstructive options in C4 SCI, optimizing functional outcome tools that are specific to SCI, and integrating other technologies such as implantable neuroprostheses for trunk stability will further enhance the impact of this surgery (under “Current Research and Investigation” at the end of this chapter). The question of whether nerve transfer outcomes continue to improve with time remains to be determined.
Algorithms for choice of surgery: Tendon transfers versus nerve transfers
Algorithms for choice of surgery are complex and depend on the injury level, hand dominance, patient preference, functional goals for each hand, access to hand therapy, and surgeon preference and experience. Where needed, elbow extension is reliably restored using a teres minor to triceps nerve transfer, and the motor portion of the posterior axillary nerve can be added as a donor if the nerve to the teres minor is small or its stimulation is suboptimal. A deltoid to triceps tendon transfer is our preferred choice 12 months after SCI and can also be used for salvage if the nerve transfer fails. A biceps to triceps tendon transfer should be avoided if the supinator is used as a nerve donor in the same limb because complete loss of active supination may be disabling.
Tendon transfers improve lower motor function, while nerve transfers are aimed to restore motor function to the original muscle. Tendon transfers can be combined with nerve transfers to maximize functional benefits, or be used for improving different function of a patient. Table 32.1 outlines the commonly used forearm/hand reconstructive combinations and complements previously published algorithms. , , Tendon transfer has been performed in the tetraplegic patients for decades and are well accepted popular treatment for these patients. The goals are to provide the patients with tetraplegia with active elbow extension, wrist extension (if absent), and sufficient pinch and/or grip strength, and release to perform activities of daily living. It is estimated that 65% to 75% of patients with cervical spinal cord injuries could benefit from upper extremity tendon transfer. Patients who have defined goals, actively participate in therapy, and understand expected outcomes, appear to have high satisfaction. Where motor donors allow, reconstruction of grasp and pinch with tendon transfers in one hand and nerve transfers in the other afford the patient one “power hand” reconstructed with tendon transfers and another softer, more supple, for social interactions, personal care, and a more open hand that allows grasp of larger objects. The trend toward reanimating functions, such as grasp, with double nerve transfers is improving our grasp strength outcomes. For example, at the Melbourne unit, when the injury level allows, we will reanimate grasp with simultaneous extensor carpi radialis longus (ECRL) to AIN and pronator teres to flexor digitorum superficialis (FDS) nerve transfers ( Fig. 32.4 ).
Intrinsic reconstruction, discussed in the later part of this chapter, may be applied in addition to any of the forearm/hand reconstructions with tendon transfer, tendon lengthening, tendon or muscle release, nerve transfer, or neurectomy, as listed in Tables 32.2 and 32.3 .
| Motor Level | ICSHT Group | ICSHT Muscle MRC Grade of ≥4 (Unless Otherwise Specified) | Possible Donors | Forearm Reconstructive Options | ||
|---|---|---|---|---|---|---|
| Wrist Extension | Pinch/Grasp: Any Tendon Transfer (TT) or Nerve Transfer (NT) for FPL Should Include a Procedure to Stabilize the IP joint of the Thumb | Hand Opening | ||||
| C5 | 0 | With weak (MRC grade 3) BR and SUP | BRA (N) weak BR (T), weak SUP (N) | Consider BR to ECRB TT & SUP to ECRB NT in combination to try to restore wrist extension | BRA to AIN NT assisted by tenodesis grasp secondary to restored active wrist extension | Tenodesis with gravity- assisted wrist flexion |
| C5 | 1 | BR |
|
| SUP to AIN NT | Tenodesis with gravity-assisted wrist flexion |
| BRA to AIN NT | S-PIN NT | ||||
| BR to FPL TT * or BR to FDP TT | Surgical tenodesis digital extensors | ||||
| BRA to AIN NT (keep BR in reserve to augment wrist extension, grasp or pinch as a TT if needed) | Tenodesis with gravity-assisted wrist flexion | ||||
| C6 | 2 | + ECRL | As above | Not needed |
| Tenodesis with gravity-assisted wrist flexion |
| S-PIN NT | |||||
| ||||||
| ||||||
| ||||||
| C6 | 3 | + ECRB |
| Not needed |
| S-PIN NT |
| ||||||
| ||||||
| C6 | 4 | + PT |
| Not needed | As for group 3 Consider double NT for grasp, i.e., ECRB to AIN and PT (distal branch) to FDS | S-PIN NT |
| C7 | 5 | + FCR | As above plus FCR | Not needed | As for group 4 | S-PIN NT |
| C7 | 6 | + EDC | As above plus EDC/EIP/EDM (T) | Not needed | As for group 4 | SUP to EPL fascicle of PIN NT |
| C7 | 7 | + EPL | As above | Not needed | As for group 4 | Not needed |
| C8 | 8 | + Partial digital flexors | As above | Not needed | BR to FPL and/or ECRL to FDP TT if needed | Not needed |
| C8 | 9 | Lacks only intrinsics | FDS (T) | Not needed | Not needed | Not needed |
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