A literature review of intercostal-to-musculocutaneous-nerve transfers in brachial plexus injury patients: Does body mass index influence results in Eastern versus Western countries?

BACKGROUND: A wide range of results have appeared in the literature for intercostal nerve transfers in brachial plexus patients. Oriental countries generally have a lower body mass index (BMI) than their occidental counterparts. We analyzed published series of intercostal nerve transfers for elbow reinnervation to determine if a difference in outcomes exists between Eastern and Western series that could be inversely related to BMI. METHODS: A PubMed search was conducted. Inclusion criteria were: (1) time from trauma to surgery <12 months, (2) minimum follow-up one year, (3) intercostal to musculocutaneous nerve transfer the only surgical procedure performed to reestablish elbow flexion, and (4) males comprising more than 75% of cases. Two groups were created: Series from western countries, including America, Europe, and Africa; and series from Asia. Pearson correlation analysis was performed to assess for the degree of correlation between percent responders and mean national BMI. RESULTS: A total of 26 series were included, 14 from western countries and 12 from Eastern countries, encompassing a total of 274 and 432 surgical cases, respectively. The two groups were almost identical in mean age, but quite different in mean national BMI (26.3 vs. 22.5) and in the percentage of patients who achieved at least a Medical Research Council (MRC) level 3 (59.5% vs. 79.3%). Time from trauma to surgery was slightly shorter in Eastern (3.4 months) versus Western countries (5.0 months). CONCLUSIONS: The percentage of responders to intercostal to musculocutaneous nerve transfer was inversely correlated with the mean national BMI among male residents of the country where the series was performed.