Impact of Timing on Muscle Strength Following Nerve Transfer for Upper Trunk Palsy: A Systematic Review and Meta-Analysis

Introduction: Nerve transfers are a widely utilized treatment for severe upper trunk palsy, yet the optimal timing for surgical intervention remains debated. This study aimed to evaluate the effect of early versus late nerve transfer on postoperative muscle strength outcomes.

Methods: A systematic review following PRISMA guidelines was conducted to address the PICO question: Does early ( < 6 months) compared to late (≥6 months) nerve transfer for upper trunk palsy improve muscle strength outcomes, as measured by the Medical Research Council (MRC) scale? A meta-analysis was performed to compare the mean difference in MRC between the early and late intervention groups. The association between age and successful muscle function recovery was assessed as a secondary outcome. The quality of included studies was evaluated using the Methodological Index for Non-Randomized Studies (MINORS) tool.

Results: A total of 349 studies were screened, with 27 studies meeting criteria for systematic review, and 16 included in the meta-analysis. There were 655 male, 80 female, and 97 patients of unspecified sex. The average age was 30 years old, with the majority of cases involving traumatic etiologies. The average time from injury to surgery was approximately 6 months, and most patients had follow-up times exceeding one year. The nerve transfers included spinal accessory to suprascapular, triceps branch to axillary, and ulnar to musculocutaneous, among others. Overall, 192 patients underwent nerve transfer within 6 months of injury, while 146 underwent nerve transfer after 6 months. Patients who underwent early nerve transfer had a 0.96 point higher postoperative MRC, compared to patients in the delayed period (p < 0.05, n = 338). Additionally, patients who achieved useful postoperative muscle strength (MRC ≥ 3) were 3.96 years younger than patients who did not (95% CI = [-6.39, -1.53], n = 271). All included studies were of moderate quality according to MINORS, except one of poor quality.

Conclusion : Early nerve transfers for upper trunk palsy result in clinically and statistically significant improvements in muscle strength. When possible, patients with persistent severe upper trunk palsy should undergo nerve transfer within 6 months post-injury.