Background: Elbow flexion after upper brachial plexus injury may be restored by a nerve transfer from the ulnar nerve to the biceps motor branch with an optional nerve transfer from the median nerve to the brachialis motor branch (single and double fascicular nerve transfer). This meta-analysis assesses the effectiveness of both techniques and the added value of additional reinnervation of the brachialis muscle. Methods: Comprehensive searches were performed identifying studies concerning restoration of elbow flexion through single and double fascicular nerve transfers. Only C5 to C6 lesion patients were included in quantitative analysis to prevent confounding by indication. Primary outcome was the proportion of patients reaching British Medical Research Council elbow flexion grade 3 or greater. Meta-analysis was performed with random effects models. Results: Thirty-five studies were included (n = 688). In quantitative analysis, 29 studies were included (n = 341). After single fascicular nerve transfer, 190 of 207 patients reached Medical Research Council grade 3 or higher (random effects model, 95.6 percent; 95 percent CI, 92.9 to 98.2 percent); and after double fascicular nerve transfer, 128 of 134 patients reached grade 3 or higher (random effects model, 97.5 percent; 95 percent CI, 95.0 to 100 percent; p = 0.301). Significantly more double nerve transfer patients reached grade 4 or greater if preoperative delay was 6 months or less (84 of 101 versus 49 of 51; p = 0.035). Conclusions: Additional reinnervation of the brachialis muscle did not result in significantly more patients reaching Medical Research Council grade 3 or higher for elbow flexion. Double fascicular nerve transfer may result in more patients reaching grade 4 or higher in patients with a preoperative delay less than 6 months. The median nerve may be preserved or used for another nerve transfer without substantially impairing elbow flexion restoration.
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