Background: Tendon transfers are commonly performed in patients with brachial plexus birth palsy (BPBP) to improve function. Transferring 2 tendons in patients with C5-7 injury has the potential complication of loss of midline function. The purpose of this study was to investigate whether a single tendon transfer (1TT) as opposed to the traditional double tendon transfer (2TT) resulted in any differences in functional outcomes in patients with C5-7 BPBP. Methods: A retrospective review of all patients with C5-7 BPBP who underwent tendon transfers to improve shoulder external rotation over a 5-year period was performed at 2 institutions. Outcomes were assessed using the modified Mallet (MM) classification scores. Results: Twenty-two C5-7 patients had complete records of preoperative and postoperative MM scores, including 11 sex-matched patients in both the 1TT and 2TT groups. When comparing preoperative and postoperative MM categories, there were significant improvements in both the 1TT and 2TT groups for global abduction ( P < .05 and P < .01, respectively) and external rotation ( P < .00001 for both). Modified Mallet (MM) hand to neck scores were significantly improved in the 2TT group ( P < .05) but not in the 1TT group ( P = .053). Internal rotation scores significantly decreased in both groups ( P < .001). Both groups demonstrated significant increases in total scores from the preoperative MM scores ( P < .01). Conclusion: The 1TT and 2TT procedures result in substantial gains in upper extremity functions for patients with C5-7 BPBP as measured by the MM score, specifically within the global abduction and external rotation subcategories. However, a significant loss occurs in internal rotation for both groups.
