Deformity about the shoulder is common after brachial plexus birth injuries. The imbalance between external rotation and internal rotation typically leads to an internal rotation contracture over time. This leads to secondary changes in the glenohumeral joint. Recently, studies have concentrated on the relationship between the humeral head and glenoid after brachial plexus birth palsies. This study focuses on the amount of humeral head version in children with brachial plexus birth lesions. Thirty-three children were included in the study. Thirteen infants underwent MR imaging early in life, with a mean age of 5 months. Twenty additional children underwent MR imaging of an established internal rotation contracture (mean age of 2 years). In all children both shoulders and elbows were examined. Measurements were made using digital format software. Version of the humeral head was measured using the humeral condyles as a baseline. Mean humeral retroversion of the normal side was –21.5 degrees with a large standard deviation of 15.1 degrees. The pathologic side showed an increased humeral retroversion compared to the normal contralateral side. The difference was present in the children older than 12 months of age. In this group, the mean humeral retroversion was – 29.9 degrees compared to –19.6 degrees in the normal shoulder. This 10 degrees difference was significant. This relationship was not found in children under the age of 12 months.
The contribution of humeral retroversion in glenohumeral dysplasia after brachial plexus birth palsy is an interesting supposition. These authors have previously demonstrated glenoid retroversion in response to the persistent internal rotation contracture. The increased humeral retroversion may compensate for the internal rotation posture of the arm. A combination of increased humeral retroversion in the presence of an internal rotation contracture may better position the limb. In contrast, this position of humeral retroversion may extenuate posterior subluxation of the humeral head. Reduction of glenohumeral subluxation may result in an external rotation contracture of the limb. This posturing has been found by Birch, et al, although it remains unclear as to whether this is due to stiffness of the glenohumeral joint or abnormal anatomic relationships. This study lends further insight into the pathoanatomy after residual brachial plexus birth palsy and warrants additional study.
J Bone Joint Surg