Nerve transfers in the upper extremity following cervical spinal cord injury. Part 2: Preliminary results of a prospective clinical trial

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OBJECTIVE

Patients with cervical spinal cord injury (SCI)/tetraplegia consistently rank restoring arm and hand function as their top functional priority to improve quality of life. Motor nerve transfers traditionally used to treat peripheral nerve injuries are increasingly used to treat patients with cervical SCIs. In this article, the authors present early results of a prospective clinical trial using nerve transfers to restore upper-extremity function in tetraplegia.

METHODS

Participants with American Spinal Injury Association (ASIA) grade A–C cervical SCI/tetraplegia were prospectively enrolled at a single institution, and nerve transfer(s) was performed to improve upper-extremity function. Functional recovery and strength outcomes were independently assessed and prospectively tracked.

RESULTS

Seventeen participants (94.1% males) with a median age of 28.4 years (range 18.2–76.3 years) who underwent nerve transfers at a median of 18.2 months (range 5.2–130.8 months) after injury were included in the analysis. Preoperative SCI levels ranged from C2 to C7, most commonly at C4 (35.3%). The median postoperative follow-up duration was 24.9 months (range 12.0–29.1 months). Patients who underwent transfers to median nerve motor branches and completed 18- and 24-month follow-ups achieved finger flexion strength Medical Research Council (MRC) grade ≥ 3/5 in 4 of 15 (26.7%) and 3 of 12 (25.0%) treated upper limbs, respectively. Similarly, patients achieved MRC grade ≥ 3/5 wrist flexion strength in 5 of 15 (33.3%) and 3 of 12 (25.0%) upper limbs. Among patients who underwent transfers to the posterior interosseous nerve (PIN) for wrist/finger extension, MRC grade ≥ 3/5 strength was demonstrated in 5 of 9 (55.6%) and 4 of 7 (57.1%) upper limbs 18 and 24 months postoperatively, respectively. Similarly, grade ≥ 3/5 strength was demonstrated in 5 of 9 (55.6%) and 4 of 7 (57.1%) cases for thumb extension. No meaningful donor site deficits were observed. Patients reported significant postoperative improvements from baseline on upper-extremity–specific self-reported outcome measures.

CONCLUSIONS

Motor nerve transfers are a promising treatment option to restore upper-extremity function after SCI. In the authors’ experience, nerve transfers for the reinnervation of hand and finger flexors showed variable functional recovery; however, transfers for the reinnervation of arm, hand, and finger extensors showed a more consistent and meaningful return of strength and function.

ABBREVIATIONS AIN = anterior interosseous nerve; ASIA = American Spinal Injury Association; DASH = Disabilities of the Arm, Shoulder, and Hand; ECRB = extensor carpi radialis brevis; ECRL = extensor carpi radialis longus; EDC = extensor digitorum communis; EMG = electromyography; EPB = extensor pollicis brevis; EPL = extensor pollicis longus; FCR = flexor carpi radialis; FDP = flexor digitorum profundus; FDS = flexor digitorum superficialis; FPL = flexor pollicis longus; ICSHT = International Classification for Surgery of the Hand in Tetraplegia; MHQ = Michigan Hand Questionnaire; MRC = Medical Research Council; PIN = posterior interosseous nerve; SCI = spinal cord injury.

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Article Information

Correspondence Wilson Z. Ray: Washington University School of Medicine, St. Louis, MO. rayz@wustl.edu.

INCLUDE WHEN CITING Published online July 12, 2019; DOI: 10.3171/2019.4.SPINE19399.

Disclosures Dr. Mahan: consultant for AxoGen, joimax, and Gecko Biomedical. Dr. Ray: consultant for Globus and DePuy Synthes and patent holder with Acera.

© AANS, except where prohibited by US copyright law.

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    CONSORT flow diagram providing details of participants’ involvement in the clinical study. CONSORT Flow Diagram Template obtained from http://www.consort-statement.org/. Figure is available in color online only.

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    Pre- and postoperative muscle strength of flexor recipient muscle groups assessed by manual muscle testing and Medical Research Council (MRC) scores. “Final” indicates muscle strength at the time of the last recorded follow-up evaluation. As follow-up at the intervening time points between the initial and final follow-ups was incomplete, we imputed missing data for muscle strengths as being the lower of the two adjacent (before/after) time points. Paired preoperative versus final postoperative comparisons were performed using the Wilcoxon signed-rank test. Figure is available in color online only.

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    Pre- and postoperative muscle strength of extensor recipient muscle groups assessed by manual muscle testing and MRC grades. “Final” indicates muscle strength at the time of the last recorded follow-up evaluation. As follow-up at the intervening time points between the initial and final follow-ups was incomplete, we imputed missing data for muscle strengths as being the lower of the two adjacent (before/after) time points. Paired preoperative versus final postoperative comparisons were performed using the Wilcoxon signed-rank test. Figure is available in color online only.

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    Preoperative and final postoperative patient-reported outcome measures. MHQ total combined median score for affected hand(s) (n = 15 pairs) and the DASH symptom (n = 14 pairs) median scores are normalized out of 100. Error bars represent 95% CIs. Paired preoperative versus final postoperative comparisons were performed using the Wilcoxon signed-rank test.

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    Zones of the spinal cord after injury. The supralesional segment (blue) is largely intact; the descending fibers and lower motor neurons (LMNs) permit normal volitional control in corresponding myotomes. The zone of SCI (red) disrupts cortical control and damages anterior horn cells, resulting in both upper motor neuron (UMN) and lower motor neuron injury. Below the level of injury (green), there is no volitional control due to disruption of the descending motor fibers by the injury; however, the anterior horn lower motor neurons are intact and in continuity with their target motor endplates. The upper segment represents our donor nerves and, depending on the timing after injury, the lower 2 segments represent potential recipients. From Ray WZ, Chang J, Hawasli A, Wilson TJ, Yang L: Motor nerve transfers: a comprehensive review. Neurosurgery 78(1):1–26, 2016, used by permission of Oxford University Press and the Congress of Neurological Surgeons. Figure is available in color online only.

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