Upper Limb Nerve Transfer Surgery in Patients With Tetraplegia

Abstract

Importance: Cervical spinal cord injury (SCI) causes devastating loss of upper extremity function and independence. Nerve transfers are a promising approach to reanimate upper limbs; however, there remains a paucity of high-quality evidence supporting a clinical benefit for patients with tetraplegia.

Objective: To evaluate the clinical utility of nerve transfers for reanimation of upper limb function in tetraplegia.

Design, setting, and participants: In this prospective case series, adults with cervical SCI and upper extremity paralysis whose recovery plateaued were enrolled between September 1, 2015, and January 31, 2019. Data analysis was performed from August 2021 to February 2022.

Interventions: Nerve transfers to reanimate upper extremity motor function with target reinnervation of elbow extension and hand grasp, pinch, and/or release.

Main outcomes and measures: The primary outcome was motor strength measured by Medical Research Council (MRC) grades 0 to 5. Secondary outcomes included Sollerman Hand Function Test (SHFT); Michigan Hand Outcome Questionnaire (MHQ); Disabilities of Arm, Shoulder, and Hand (DASH); and 36-Item Short Form Health Survey (SF-36) physical component summary (PCS) and mental component summary (MCS) scores. Outcomes were assessed up to 48 months postoperatively.

Results: Twenty-two patients with tetraplegia (median age, 36 years [range, 18-76 years]; 21 male [95%]) underwent 60 nerve transfers on 35 upper limbs at a median time of 21 months (range, 6-142 months) after SCI. At final follow-up, upper limb motor strength improved significantly: median MRC grades were 3 (IQR, 2.5-4; P = .01) for triceps, with 70% of upper limbs gaining an MRC grade of 3 or higher for elbow extension; 4 (IQR, 2-4; P < .001) for finger extensors, with 79% of hands gaining an MRC grade of 3 or higher for finger extension; and 2 (IQR, 1-3; P < .001) for finger flexors, with 52% of hands gaining an MRC grade of 3 or higher for finger flexion. The secondary outcomes of SHFT, MHQ, DASH, and SF36-PCS scores improved beyond the established minimal clinically important difference. Both early (<12 months) and delayed (≥12 months) nerve transfers after SCI achieved comparable motor outcomes. Continual improvement in motor strength was observed in the finger flexors and extensors across the entire duration of follow-up.

Conclusions and relevance: In this prospective case series, nerve transfer surgery was associated with improvement of upper limb motor strength and functional independence in patients with tetraplegia. Nerve transfer is a promising intervention feasible in both subacute and chronic SCI.

Figure 1.. Nerve Transfers

Only muscles innervated by recipient nerves have restoration of activity (gray represents atrophic muscles not innervated). In high tetraplegia (International Classification for Surgery of the Hand in Tetraplegia group 0), no upper extremity donor nerves are available. The spinal accessory nerve (SAN) is transferred to the triceps motor branch using an approximately 20-cm interpositional nerve graft to restore elbow extension. The brachialis motor branch is transferred to the isolated anterior interosseus nerve (AIN) fascicle in the proximal median nerve. A indicates anterior; L, lateral; M, medial; P, posterior.

Figure 2.. Incremental Change in Motor Strengths of Flexor and Extensor Muscles Recorded at Baseline and at Each Follow-up Evaluation

Missing data between initial visit and final follow-up were imputed using the last observation carried forward approach between before and after time points. Gradient bars demonstrate Medical Research Council (MRC) grade of 0 to 5. Paired Wilcoxon signed rank tests were used to analyze preoperative and final postoperative MRC scores. Flexor digitorum profundus (FDP) in brachialis to anterior interosseus nerve and extensor digitorum communis (EDC) in supinator to posterior interosseus nerve and triceps in axillary to triceps nerve transfer were used as surrogates to demonstrate evidence of reinnervation and gaining meaningful function. Reinnervation was defined as gaining palpable contraction of an MRC grade of 1, and antigravity was defined as gaining an MRC grade of 3 or higher at subsequent follow-up evaluations. Log-rank tests were used to analyze the significance of difference in gaining reinnervation and meaningful function. Final indicates the last recorded motor strength for each patient; EPL/B, exensor pollicis longus/brevis; and FPL, flexor pollicis longus.

Figure 3.. Gain in Postoperative Hand Function and Patient-Reported Outcome Measures

The Sollerman Hand Function Test (SHFT) scores are raw scores of a maximum of 80. To avoid confounding with hand functional scores, triceps nerve transfers were excluded from SHFT and only nerve transfers to reanimate hand function were included. The Michigan Hand Outcome Questionnaire (MHQ) total cumulative scores and activities of daily living (ADLs) component were normalized to 100. The Disabilities of Arm, Shoulder, and Hand (DASH) scores were normalized to 100. The 36-Item Short Form Health Survey (SF-36) physical component summary (PCS) and mental component summary (MCS) scores were normalized to 100. Preoperative (pre-op) and final postoperative (post-op) values were analyzed via a paired Wilcoxon signed rank test. Error bars represent 95% CIs. Dotted lines represent the minimal clinically important difference (MCID) threshold from mean baseline scores.