Residual brachial plexus birth palsy often leads to limb-length discrepancy. The exact amount of shortening of the limb has yet to be quantified. This study attempts to identify the precise limb inequality in a cohort of patients with residual brachial plexus birth palsies. Twenty-two skeletally immature children, with an average age of 8.6 years, were included in the study. Ten children had involvement of the upper brachial plexus, nine had a global involvement and three had lower plexus dysfunction. Radiographs of the uninvolved and involved humerii and forearms were obtained, with a radiographic markers placed adjacent to the extremity. Humeral length and forearm lengths were calculated, using standard anatomic landmarks. Respective lengths were compared, as was the overall limb length. Twenty-one of the twenty-two children had shortening at both the humeral and forearm level. The involved limb length averaged 92% of the uninvolved limb, with a range from 82-98%. Humeral length averaged 93% and forearm length averaged 90%. All differences in length were statistically significant. Children with global brachial plexus lesions had more forearm shortening when compared to those with isolated upper lesions. As expected, there was a correlation between total length and age of the child.
This information can be applied to clinical practice. Children with residual brachial plexus birth palsy often have involvement of the upper trunk. The expected limb-length discrepancy is approximately 10%. Global lesions have increased limb-length discrepancy that can be as great as 25%. This inequality in limb length is disconcerting to both patient and family. Early consultation and education may be useful. Unfortunately, the exact cause of limb-length discrepancy remains unclear. The growth plate is extremely receptive to early range of motion and applied loads. Future studies need to concentrate on methods to enhance recovery and diminish the limb-length discrepancy.
J Pediatr Orthop