Upper Limb Nerve Transfer Surgery in Patients With Tetraplegia

Neuromuscular consequences of spinal cord injury: New mechanistic insights and clinical considerations

The spinal cord facilitates communication between the brain and the body, containing intrinsic systems that work with lower motor neurons (LMNs) to manage movement. Spinal cord injuries (SCIs) can lead to partial paralysis and dysfunctions in muscles below the injury. While traditionally this paralysis has been attributed to disruptions in the corticospinal tract, a growing body of work demonstrates LMN damage is a factor. Motor units, comprising the LMN and the muscle fibers with which they connect, are essential for voluntary movement. Our understanding of their changes post-SCI is still emerging, but the health of motor units is vital, especially when considering innovative SCI treatments like nerve transfer surgery. This review seeks to collate current literature on how SCI impact motor units and explore neuromuscular clinical implications and treatment avenues. SCI reduced motor unit number estimates, and surviving motor units had impaired signal transmission at the neuromuscular junction, force-generating capacity, and excitability, which have the potential to recover chronically, yet the underlaying mechanisms are unclear. Furthermore, electrodiagnostic evaluations can aid in assessing the health lower and upper motor neurons, identify suitable targets for nerve transfer surgeries, and detect patients with time sensitive injuries. Lastly, many electrodiagnostic abnormalities occur in both chronic and acute SCI, yet factors contributing to these abnormalities are unknown. Future studies are required to determine how motor units adapt following SCI and the clinical implications of these adaptations.

Peripheral nerve transfers for dysfunctions in central nervous system injuries: a systematic review

BACKGROUND

The review highlights recent advancements and innovative uses of nerve transfer surgery in treating dysfunctions caused by central nervous system (CNS) injuries, with a particular focus on spinal cord injury (SCI), stroke, traumatic brain injury, and cerebral palsy.

METHODS

A comprehensive literature search was conducted regarding nerve transfer for restoring sensorimotor functions and bladder control following injuries of spinal cord and brain, across PubMed and Web of Science from January 1920 to May 2023. Two independent reviewers undertook article selection, data extraction, and risk of bias assessment with several appraisal tools, including the Cochrane Risk of Bias Tool, the JBI Critical Appraisal Checklist, and SYRCLE's ROB tool. The study protocol has been registered and reported following PRISMA and AMSTAR guidelines.

RESULTS

Nine hundred six articles were retrieved, of which 35 studies were included (20 on SCI and 15 on brain injury), with 371 participants included in the surgery group and 192 in the control group. These articles were mostly low-risk, with methodological concerns in study types, highlighting the complexity and diversity. For SCI, the strength of target muscle increased by 3.13 of Medical Research Council grade, and the residual urine volume reduced by more than 100 ml in 15 of 20 patients. For unilateral brain injury, the Fugl-Myer motor assessment (FMA) improved 15.14-26 score in upper extremity compared to 2.35-26 in the control group. The overall reduction in Modified Ashworth score was 0.76-2 compared to 0-1 in the control group. Range of motion (ROM) increased 18.4-80° in elbow, 20.4-110° in wrist and 18.8-130° in forearm, while ROM changed -4.03°-20° in elbow, -2.08°-10° in wrist, -2.26°-20° in forearm in the control group. The improvement of FMA in lower extremity was 9 score compared to the presurgery.

CONCLUSION

Nerve transfer generally improves sensorimotor functions in paralyzed limbs and bladder control following CNS injury. The technique effectively creates a 'bypass' for signals and facilitates functional recovery by leveraging neural plasticity. It suggested a future of surgery, neurorehabilitation and robotic-assistants converge to improve outcomes for CNS.

Impact of Upper Limb Motor Recovery on Functional Independence After Traumatic Low Cervical Spinal Cord Injury

Cervical spinal cord injury (SCI) causes devastating loss of upper limb function and independence. Restoration of upper limb function can have a profound impact on independence and quality of life. In low-cervical SCI (level C5-C8), upper limb function can be restored via reinnervation strategies such as nerve transfer surgery. The translation of recovered upper limb motor function into functional independence in activities of daily living (ADLs), however, remains unknown in low cervical SCI (i.e., tetraplegia). The objective of this study was to evaluate the association of patterns in upper limb motor recovery with functional independence in ADLs. This will then inform prioritization of reinnervation strategies focused to maximize function in patients with tetraplegia. This retrospective study performed a secondary analysis of patients with low cervical (C5-C8) enrolled in the SCI Model Systems (SCIMS) database. Baseline neurological examinations and their association with functional independence in major ADLs-i.e., eating, bladder management, and transfers (bed/wheelchair/chair)-were evaluated. Motor functional recovery was defined as achieving motor strength, in modified research council (MRC) grade, of ≥ 3 /5 at one year from ≤ 2/5 at baseline. The association of motor function recovery with functional independence at one-year follow-up was compared in patients with recovered elbow flexion (C5), wrist extension (C6), elbow extension (C7), and finger flexion (C8). A multi-variable logistic regression analysis, adjusting for known factors influencing recovery after SCI, was performed to evaluate the impact of motor function at one year on a composite outcome of functional independence in major ADLs. Composite outcome was defined as functional independence measure score of 6 or higher (complete independence) in at least two domains among eating, bladder management, and transfers. Between 1992 and 2016, 1090 patients with low cervical SCI and complete neurological/functional measures were included. At baseline, 67% of patients had complete SCI and 33% had incomplete SCI. The majority of patients were dependent in eating, bladder management, and transfers. At one-year follow-up, the largest proportion of patients who recovered motor function in finger flexion (C8) and elbow extension (C7) gained independence in eating, bladder management, and transfers. In multi-variable analysis, patients who had recovered finger flexion (C8) or elbow extension (C7) had higher odds of gaining independence in a composite of major ADLs (odds ratio [OR] = 3.13 and OR = 2.87, respectively, p < 0.001). Age 60 years (OR = 0.44, p = 0.01), and complete SCI (OR = 0.43, p = 0.002) were associated with reduced odds of gaining independence in ADLs. After cervical SCI, finger flexion (C8) and elbow extension (C7) recovery translate into greater independence in eating, bladder management, and transfers. These results can be used to design individualized reinnervation plans to reanimate upper limb function and maximize independence in patients with low cervical SCI.

The Role of Upper Extremity Motor Function in the Choice of Bladder Management in Those Unable to Volitionally Void due to Neurologic Dysfunction

It is estimated that 425,000 individuals with neurologic bladder dysfunction (spinal cordinjury, spina bifida and multiple sclerosis) are unable to volitionally void and must rely oncatheter drainage. Upper extremity (UE) motor function is one of the most important factors indetermining the type of bladder management chosen in individuals who cannot volitionally void. Novel bladder management solutions for those with impaired UE motor function and concurrent impairments involitional voiding continue to be an area of need. Those with poor UE motor function more often choose an indwelling catheter, whereas those with normal UE motor function more often choose clean intermittent catheterization.

Nerve Transfer After Cervical Spinal Cord Injury: Who Has a "Time Sensitive" Injury Based on Electrodiagnostic Findings?

OBJECTIVE

To use the ulnar compound muscle action potential (CMAP) to abductor digiti minimi (ADM) to identify the proportion of individuals with cervical spinal cord injury (SCI) who have lower motor neuron (LMN) abnormalities involving the C8-T1 spinal nerve roots, within 3-6 months, and thus may influence the response to nerve transfer surgery.

DESIGN

Retrospective analysis of prospectively collected data. Data were analyzed from European Multicenter Study About SCI database.

SETTING

Multi-center, academic hospitals.

PARTICIPANTS

We included 79 subjects (age=41.4±17.7, range:16-75; 59 men; N=79), who were classified as cervical level injuries 2 weeks after injury and who had manual muscle strength examinations that would warrant consideration for nerve transfer (C5≥4, C8<3).

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

The ulnar nerve CMAP amplitude to ADM was used as a proxy measure for C8-T1 spinal segment health. CMAP amplitude was stratified into very abnormal (<1.0 mV), sub-normal (1.0-5.9 mV), and normal (>6.0 mV). Analysis took place at 3 (n=148 limbs) and 6 months (n=145 limbs).

RESULTS

At 3- and 6-month post-injury, 33.1% and 28.3% of limbs had very abnormal CMAP amplitudes, respectively, while in 54.1% and 51.7%, CMAPs were sub-normal. Median change in amplitude from 3 to 6 months was 0.0 mV for very abnormal and 1.0 mV for subnormal groups. A 3-month ulnar CMAP <1 mV had a positive predictive value of 0.73 (95% CI 0.69-0.76) and 0.78 (95% CI 0.75-0.80) for C8 and T1 muscle strength of 0 vs 1 or 2.

CONCLUSION

A high proportion of individuals have ulnar CMAPs below the lower limit of normal 3- and 6-month post cervical SCI and may also have intercurrent LMN injury. Failure to identify individuals with LMN denervation could result in a lost opportunity to improve hand function through timely nerve transfer surgeries.

Advancements in autologous peripheral nerve transplantation care: a review of strategies and practices to facilitate recovery

Autologous peripheral nerve transplantation, a pioneering technique in nerve injury treatment, has demonstrated remarkable progress. We examine recent nursing strategies and methodologies tailored to various anatomical sites, highlighting their role in postoperative recovery enhancement. Encompassing brachial plexus, upper limb, and lower limb nerve transplantation care, this discussion underscores the importance of personalized rehabilitation plans, interdisciplinary collaboration, and innovative approaches like nerve electrical stimulation and nerve growth factor therapy. Moreover, the exploration extends to effective complication management and prevention strategies, encompassing infection control and pain management. Ultimately, the review concludes by emphasizing the advances achieved in autologous peripheral nerve transplantation care, showcasing the potential to optimize postoperative recovery through tailored and advanced practices.

Symptomatic Treatment of Myelopathy

OBJECTIVE

This article discusses the effects of myelopathy on multiple organ systems and reviews the treatment and management of some of these effects.

LATEST DEVELOPMENTS

Recent advances in functional electrical stimulation, epidural spinal cord stimulation, robotics, and surgical techniques such as nerve transfer show promise in improving function in patients with myelopathy. Ongoing research in stem cell therapy and neurotherapeutic drugs may provide further therapeutic avenues in the future.

ESSENTIAL POINTS

Treatment for symptoms of spinal cord injury should be targeted toward patient goals. If nerve transfer for upper extremity function is considered, the patient should be evaluated at around 6 months from injury to assess for lower motor neuron involvement and possible time limitations of surgery. A patient with injury at or above the T6 level is at risk for autonomic dysreflexia, a life-threatening condition that presents with elevated blood pressure and can lead to emergent hypertensive crisis. Baclofen withdrawal due to baclofen pump failure or programming errors may also be life-threatening. Proper management of symptoms may help avoid complications such as autonomic dysreflexia, renal failure, heterotopic ossification, and fractures.

Supinator to Posterior Interosseous Nerve Transfer for Recovery of Hand Opening in the Tetraplegic Patient: A Case Series

BACKGROUND AND OBJECTIVES

Cervical spinal cord injury results in devastating loss of function. Nerve transfers can restore functional use of the hand, the highest priority function in this population to gain independence. Transfer of radial nerve branches innervating the supinator to the posterior interosseous nerve (SUP-PIN) has become a primary intervention for the recovery of hand opening, but few outcome reports exist to date. We report single-surgeon outcomes for this procedure.

METHODS

The SUP-PIN transfer was performed on adults with traumatic spinal cord injury resulting in hand paralysis. Outcome measures include Medical Research Council strength grade for extension of each digit, and angles representing critical apertures: the first web space opening of the thumb, and metacarpophalangeal angle of the remaining fingers. Factors affecting these measurements, including preserved tone and spasticity of related muscles, were also assessed.

RESULTS

Twenty-three adult patients with a C5-7 motor level underwent SUP-PIN transfers on 36 limbs (median age 31 years, interquartile range [21.5, 41]). The median interval from injury to surgery was 10.5 (8.2, 6.5) months, with 9 (7.5, 11) months for the acute injuries and 50 (32, 66) months for the chronic (>18 months) injuries. Outcomes were observed at a mean follow-up of 22 (14, 32.5) months. 30 (83.3%) hands recovered at least antigravity extension of the thumb and 34 (94.4%) demonstrated successful antigravity strength for the finger extensors, providing adequate opening for a functional grasp. Chronic patients (>18 months after injury) showed similar outcomes to those who had earlier surgery. Supination remained strong (at least M4) in all but a single patient and no complications were observed.

CONCLUSION

SUP-PIN is a reliable procedure for recovery of finger extension. Chronic patients remain good candidates, provided innervation of target muscles is preserved. Higher C5 injuries were more likely to have poor outcomes.

Comparison of nerve versus tendon transfer for radial nerve palsy

OBJECTIVE

This study aims to investigate the choice of intervention time and operation mode between nerve and tendon transfer for the treatment of radial nerve palsy (RNP).

METHODS

46 RNP patients underwent nerve transfer (n = 22) and tendon transfer (n = 24). The intraoperative blood loss, main incision length, operation duration, and length of hospital stay and follow-up period of patients in these two groups were recorded and compared. The range of motion (ROM) of the elbow, wrist, fingers, and thumb, the hand grip and pinch strength, the Disabilities of Arm, Shoulder, and Hand (DASH) and the 36-Item Short Form Health Survey (SF-36) scores were measured and compared preoperatively and postoperatively between the two groups.

RESULTS

The ROM of thumb and the hand grip strength of patients in the nerve transfer group were greater than that in the tendon transfer (P < 0.05). Both of the two groups indicated significant improvements in the ROM of elbow, wrist, finger, thumb and the hand grip and pinch strength (P < 0.05) postoperatively. The DASH scores decreased significantly at 6 months (P < 0.05) and 12 months (P < 0.05) after surgery in both groups, while the postoperative SF-36 scores significantly increased (P < 0.05). There was no significant difference in postoperative DASH and SF-36 scores between the two groups (P > 0.05).

CONCLUSION

In summary, both nerve and tendon transfer techniques are effective treatments for RNP. Nerve transfer is particularly advantageous for early RNP, while tendon transfer is suitable for patients with radial nerve injury more than one year.

Clinical Outcomes of "Paralyzed" Nerve Transfer for Treating Spinal Cord Injury: A Proof of Concept in a Human Model

Functional electrical stimulation (FES) is an option to restore function in individuals after high cervical spinal cord injury (SCI) who have limited available options for tendon or nerve transfer. To be considered for FES implantation, patients must possess upper motor neuron (UMN) type denervation in potential recipient muscles, which can be confirmed by response to surface electrical stimulation during clinical evaluation. Lower motor neuron (LMN) denervated muscles will not respond to electrical stimulation and, therefore, are unavailable for use in an FES system. Previous animal studies have demonstrated that a "paralyzed" nerve transfer of a UMN-denervated motor branch to an LMN-denervated motor branch can restore electrical excitability in the recipient. In this study, we report the indications, surgical technique, and successful outcome (restoration of M3 elbow flexion) after the first "paralyzed" nerve transfer in a human patient.

Artificial Intelligence Image Recognition System for Preventing Wrong-Site Upper Limb Surgery

Our image recognition system employs a deep learning model to differentiate between the left and right upper limbs in images, allowing doctors to determine the correct surgical position. From the experimental results, it was found that the precision rate and the recall rate of the intelligent image recognition system for preventing wrong-site upper limb surgery proposed in this paper could reach 98% and 93%, respectively. The results proved that our Artificial Intelligence Image Recognition System (AIIRS) could indeed assist orthopedic surgeons in preventing the occurrence of wrong-site left and right upper limb surgery. At the same time, in future, we will apply for an IRB based on our prototype experimental results and we will conduct the second phase of human trials. The results of this research paper are of great benefit and research value to upper limb orthopedic surgery.

T12-L3 Nerve Transfer-Induced Locomotor Recovery in Rats with Thoracolumbar Contusion: Essential Roles of Sensory Input Rerouting and Central Neuroplasticity

Locomotor recovery after spinal cord injury (SCI) remains an unmet challenge. Nerve transfer (NT), the connection of a functional/expendable peripheral nerve to a paralyzed nerve root, has long been clinically applied, aiming to restore motor control. However, outcomes have been inconsistent, suggesting that NT-induced neurological reinstatement may require activation of mechanisms beyond motor axon reinnervation (our hypothesis). We previously reported that to enhance rat locomotion following T13-L1 hemisection, T12-L3 NT must be performed within timeframes optimal for sensory nerve regrowth. Here, T12-L3 NT was performed for adult female rats with subacute (7-9 days) or chronic (8 weeks) mild (SCImi: 10 g × 12.5 mm) or moderate (SCImo: 10 g × 25 mm) T13-L1 thoracolumbar contusion. For chronic injuries, T11-12 implantation of adult hMSCs (1-week before NT), post-NT intramuscular delivery of FGF2, and environmentally enriched/enlarged (EEE) housing were provided. NT, not control procedures, qualitatively improved locomotion in both SCImi groups and animals with subacute SCImo. However, delayed NT did not produce neurological scale upgrading conversion for SCImo rats. Ablation of the T12 ventral/motor or dorsal/sensory root determined that the T12-L3 sensory input played a key role in hindlimb reanimation. Pharmacological, electrophysiological, and trans-synaptic tracing assays revealed that NT strengthened integrity of the propriospinal network, serotonergic neuromodulation, and the neuromuscular junction. Besides key outcomes of thoracolumbar contusion modeling, the data provides the first evidence that mixed NT-induced locomotor efficacy may rely pivotally on sensory rerouting and pro-repair neuroplasticity to reactivate neurocircuits/central pattern generators. The finding describes a novel neurobiology mechanism underlying NT, which can be targeted for development of innovative neurotization therapies.

Cervical spinal cord compression from subdural hematoma caused by traumatic nerve root avulsion: illustrative case

BACKGROUND

Posttraumatic intradural hematomas of the cervical spine are rare findings that may yield significant neurological deficits if they compress the spinal cord. These compressive hematomas require prompt surgical evacuation. In certain instances, intradural hematomas may form from avulsion of cervical nerve roots.

OBSERVATIONS

The authors present the case of a 29-year-old male who presented with right upper-extremity weakness in the setting of polytrauma after a motor vehicle accident. He had no cervical fractures but subsequently developed right lower-extremity weakness. Magnetic resonance imaging (MRI) demonstrated a compressive hematoma of the cervical spine that was initially read as an epidural hematoma. However, intraoperatively, it was found to be a subdural hematoma, eccentric to the right, stemming from an avulsion of the right C6 nerve root.

LESSONS

Posttraumatic cervical subdural hematomas require rapid surgical evacuation if neurological deficits are present. The source of the hematoma may be an avulsed nerve root, and the associated deficits may be unilateral if the hematoma is eccentric to one side. Surgeons should be prepared for the possibility of an intradural hematoma even in instances in which MRI appears consistent with an epidural hematoma.

Prognosis and conditional nomogram of cervical spine fracture in patients with severe spinal cord injury: a multicenter retrospective study

INTRODUCTION

Cervical spine fractures with severe spinal cord injury (SCI) are common following cervical spine trauma and are associated with a high mortality rate. Understanding the mortality patterns of patients with cervical spine fractures and severe SCI can offer valuable evidence to surgeons and family members who are required to make critical healthcare decisions. The authors aimed to evaluate the instantaneous death risk and conditional survival (CS) of such patients and developed conditional nomograms to account for different periods of survivors and predict the survival rates.

METHODS

Their instantaneous death risks were calculated using the hazard function, and the Kaplan-Meier method was used to evaluate the survival rates. Cox regression was used to choose the variables for the construction of the nomograms. The area under the receiver operating characteristic curve and calibration plots were used to validate the performance of the nomograms.

RESULTS

The authors finally included 450 patients with cervical spine fractures and severe SCI using propensity score matching. The instantaneous death risk was the highest during the first 12 months after injury. Surgical treatment can help decrease the instantaneous death risk quickly, especially in early-term surgery. The 5-year CS increased constantly from 73.3% at baseline to 88.0% after 2 years of survival. Conditional nomograms were constructed at baseline and in those who survived for 6 and 12 months. The area under the receiver operating characteristic curve and calibration curves indicated that the nomograms had a good performance.

CONCLUSION

Their results improve our understanding of the instantaneous death risk of patients in different periods following injury. CS demonstrated the exact survival rate among medium-term and long-term survivors. Conditional nomograms are suitable for different survival periods in predicting the probability of survival. Conditional nomograms help in understanding the prognosis and improve the shared decision-making approaches.