The focal article provides hand surgeons with an exploration of the basic principles of spinal cord injury (SCI) as well as the role that hand therapy, nerve transfers, and tendon transfers can play in maximizing the quality of life of these patients [1]. In this commentary, we aim to provide a comprehensive guide for physiatrists, who often meet SCI patients early in their recovery course, on the role that nerve transfer and tendon transfer can play in the treatment of SCI patients, with the aim of optimizing referral patterns between providers in order to best serve SCI patients and improve their quality of life.

Greater than 27 million people live with SCI globally, with an incidence of 13 new cases per 100,000 people each year [2,3]. Countries with a high sociodemographic index have both a higher incidence and prevalence of SCI than countries with a low sociodemographic index, with the highest rates in North America, Western Europe, and high income countries in Asia. These disparities are driven in part by higher morbidity and mortality of SCI of the same severity in lower-income countries [2,4]. Young men 15-25 years of age have the highest ncidence of cervical SCI, while all-level SCI is highest in the elderly population [3,5]. Globally, the prevalence of men with SCI is at least twice that of women [3,5].

Acute care for SCI revolves around patient stabilization, with surgery performed to decompress, reduce, or stabilize the spine. The level of injury fluctuates during the first few weeks after injury, with the apparent root level affected rising by one or two segments during the first 48 hours after injury, although recovery of function back to the initial root level usually occurs over ensuing weeks [6]. As spinal shock resolves over the first few weeks after injury, improvement in upper extremity function may occur. This recovery is due to the resolution of edema and hemorrhage at the site of injury. Subsequently, areas of partial denervation may experience peripheral nerve sprouting and muscle fiber hypertrophy, improving muscle strength [7]. After the first month of injury, further functional recovery is frequently observed in cervical SCI up to one root level, at rates between 66% and 90% [8,9]. Overall, the likelihood of spontaneous recovery decreases over time, with studies observing that a muscle that remains paralyzed after the first month has between a 1% and 10% chance of recovering antigravity strength within one year [10,11]. Spontaneous recovery is more likely to occur in incomplete SCI, with progress plateauing around six months after injury [12,13] In complete SCI, after six months there is almost no chance of any spontaneous functional recovery [14].

Therapy for patients should begin shortly after stabilization to encourage maximal recovery and maintenance of function. Passive range of motion exercises can help prevent joint stiffening and contracture, with supple passive movement an important prerequisite to successful nerve transfer [15]. Exercise has further been shown to improve peripheral nerve regeneration as well as psychological well-being in SCI patients [16]. Additionally, custom orthoses can be used to help prevent contracture or improve function [17]. Ultimately, these adjunct therapies can help patients maximize recovery potential but cannot achieve the functional improvement seen with surgical intervention.

The devastating impacts of SCI are felt most profoundly in the upper extremities, as loss of function here impedes independence in activities of daily living. The restoration of upper extremity function has been shown to be the most important reconstructive goal for patients living with SCI, with one study revealing that greater than 90% of patients with SCI believed that improving upper limb function would significantly improve their quality of life [18,19].

However, the benefits of surgical intervention are poorly understood by patients impacted by SCI, with over 25% of patients unaware of reconstructive options [19]. Additionally, patients who do learn about surgical options often receive false or discouraging information from non-surgical healthcare team members, leading many of these patients to not pursue surgery [19]. A qualitative study identified barriers to surgery as patient reluctance or lack of knowledge, and inadequate referral patterns [20]. Physiatrists can play an integral role in removing these barriers, as other work has found information from experts to serve as a facilitator of patient trust in upper limb reconstruction, with the preferred time to receive information about surgical information identified as during the acute or inpatient rehabilitation time period [20-22]. These studies highlight the importance of improving physician knowledge of reconstructive options as well as the establishment of a clear referral pathways, which would enhance patient understanding of and access to upper extremity limb reconstruction.

To quote Sterling Bunnell, “to someone who has nothing, a little is a lot” [23]. While the simple act of opening or closing the hand may be overlooked by most, it can have an immense impact on the quality of life of SCI patients. For almost every patient who has suffered SCI, there is a role for surgery to improve their function and independence.
Nerve transfers are relatively new procedures that can restore sensory and motor function by coapting the proximal end of a redundant donor nerves to the distal end of an injured nerve, sacrificing the function of the muscle innervated by the donor nerve but restoring function to the muscle innervated by the recipient nerve [24]. In comparison, tendon transfers can restore motor function only and involve moving the attachment site of the tendon of a functional muscle to restore more critical motion [25]. Tendon transfers have the benefit of being able to be undertaken at any time point after injury, but require a long period of splinting and immobilization, which can be difficult for patients with already limited function. The senior author offers nerve transfer surgery as initial upper extremity reconstruction for patients with SCI, reserving tendon transfers for secondary procedures if necessary. However, the functional desires of the patient should be carefully considered when choosing a reconstructive strategy, as nerve transfer often provides better dexterity while tendon transfer improves power [26].

Nerve transfer necessarily requires the sacrifice of a functional, innervated muscle group to take the donor nerve from. Yet, due to redundant innervation in the triceps and in the muscles involved in finger flexion, early nerve transfer for elbow extension and finger flexion both maximizes outcomes and does not inhibit spontaneous recovery, should it occur [27]. (Table 1) highlights common nerve transfers and their functional benefit, although surgical plans should be tailored to the needs of each patient, taking into consideration the pattern of injury, the patient’s current functional level, and their goals [28-32]. Patients who undergo nerve transfer report substantial improvements in function and regain more natural movement and fine motor control than patients who undergo tendon transfer [33,34]. Patients who choose to undergo nerve transfer should be counseled that reinnervation may take 12 months or more, and that regularly engaging with an experienced hand therapist is critical to the success of the surgery [26].

Timing of surgery should allow for a window for any spontaneous recovery to occur, but soon thereafter, as earlier surgery is associated with better results, especially for nerve transfer surgery [35]. Muscles that lose their motor innervation will undergo atrophic paralysis, therefore, the window in which a nerve transfer can successfully reinnervate a muscle is limited. Volitional control can theoretically be re-established for muscles with isolated upper motor neuron injuries after a longer period of time, since they maintain innervation by the lower motor neuron [33,36]. The senior author has observed successful reinnervation after an average of 5 years in a cohort of 7 patients, with a case reported in the literature of a patient regaining thumb and finger flexion after undergoing nerve transfer 12 years after injury [37]. Ultimately, reconstructive options are based on pattern of injury, time since injury, and the patient’s current and desired functional capabilities [26]. Timely referral to a hand surgeon is critical, as thorough workup including electrodiagnostic studies are necessary guide reconstructive options for the patient [38].

Physiatrists are an integral part of the multidisciplinary care team that supports patients who endure a SCI. Their participation has been established to improve both the morbidity and mortality of SCI, and their early involvement positions physiatrists as a trusted source of guidance for patients and families as they navigate rehabilitation [39]. This positions physiatrists as an important source of information to patients as well as a referral source to connect SCI patients with upper extremity surgeons.

It is important to consider that lack of referrals to hand surgeons by physiatrists may be in part due to valid concerns over the risks of surgery. One study found that over half of physiatrists had concerns about patient noncompliance and lack of social support [40]. This could impact a patient’s ability to successfully engage in therapy post-operatively, which could ultimately inhibit maximal functional gain [40,41]. Additionally, surgery carries the risk of downgrading function, which can be devastating for patients with limited mobility to begin with. While the novelty of modern nerve transfer techniques leaves the long term success rate of surgery not clearly defined, studies suggest about three quarters of patients regain useful function of their hand after nerve transfer [42,43]. The drivers behind the variability in observed outcomes are still being explored; However, age, BMI, time since injury, and ability to comply with postoperative hand therapy have been shown to impact outcomes, making careful patient selection and shared decision-making imperative to success [42].

Hand therapists often consider the ability of a patient to grasp with wrist extension via the tightening of finger flexors to be a contraindication to surgical intervention, however this grasp is notoriously weak [44,45]. While the risk of unsuccessful surgery exists, reconstruction has the potential to substantially improve patient independence by allowing them to manipulate objects to feed themselves, manage their own bladder and bowel, and improve confidence in social situations [31,46-51]. Given the gravity of both the risks of benefits of surgery after SCI, it is important for shared decision-making to occur between the patient and trusted members of their healthcare team, with accurate information provided by either a well-informed physiatrist or a hand surgeon.

The double Oberlin or double fascicular nerve transfer is a variant of the ulnar to musculocutaneous nerve transfer commonly used to restore elbow flexion in patients with SCI. The double Oberlin transfer utilizes both the ulnar and median nerve as donor nerves to restore function in the biceps and brachialis muscles [52]. A case report by Moses et al. describes the use of the double Oberlin transfer for a 25 year old patient who experienced left upper extremity weakness after a motor vehicle accident [53].

The patient initially underwent physical and occupational therapy but was referred to a peripheral nerve surgeon 5 months after injury due to persistent 0/5 strength of the left deltoid, supraspinatus, infraspinatus, and biceps, as well as decreased sensation throughout the left lateral arm, radial forearm and hand, and dorsal forearm and hand. He also experienced absent left biceps and brachioradialis reflexes. These findings were consistent with left cervical root avulsion, which was confirmed on MRI. Electrodiagnostic studies further confirmed this diagnosis, revealing root avulsions of C5 and C6, with partial C7 and C8 avulsion.

The patient underwent double Oberlin transfer without complication and over the next 12 months engaged in therapy to improve his range of motion and strength. At his 12 month follow up, the patient exhibited 4+/5 elbow flexion, 140 degree range of motion, 2+ reflexes, and intact sensation to light touch. Ultimately, the coordinated efforts of the patient’s interdisciplinary team allowed for significant recovery of left upper extremity function. Early referral to the peripheral nerve surgeon as well as consistent therapy throughout his recovery were critical components of the success of the patient’s nerve transfer.

Reconstructive options for patients with SCI can improve upper extremity function and overall quality of life. The importance of early referral to an upper extremity surgeon cannot be understated, as surgery should ideally be performed within the first year after injury. Physiatrists can play a critical role as an early member of a patient’s healthcare team, establishing referral patterns to hand surgeons early after injury. However, it is the senior author’s preference to see the most complicated patients in a multidisciplinary clinic, where a skilled team can collaboratively create a treatment plan for these patients. Partnerships between physiatrists and upper extremity surgeons can improve education for patients about reconstructive options as well as mitigate barriers to timely referral and treatment.

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