Children with residual brachial plexus birth palsy are prone to develop glenohumeral deformity. Coronal deformity has been characterized by humeral head subluxation and angular deformity has been measured by glenoid version. To date, rotational deformity has not been measured.
The authors attempted to provide a measurement of rotational deformity based upon magnetic resonance imaging. Ninety-one children were included in the cohort. The glenoscapular angle or glenoid version was measured along with the percentage of the humeral head inferior to the middle of the glenoid fossa (PHHA).
The angle of rotation of the biceps or bicep angle is a new method to assess rotational position of the ball within the socket. Decreased values of biceps angle are indicative of increased internal rotation and increased angles are indicative of increased external rotation.
The authors report significant differences between the involved and uninvolved shoulders in the version, the PHHA and the biceps angle. Of the three MRI measurements, the biceps angle was only one that remained significant utilizing a multiple regression model. Those patients with limited external rotation less than 0 had marked differences in the version, humeral head subluxation, and biceps angle compared to those patients with external rotation greater than neutral.
The glenoid version and percent of PHHA characterize osseous deformity. The biceps angle provides an additional rotational measurement that further defines the deformity in children with birth palsy. The biceps angle correlate more closely with lack of external rotation then the glenoid version or PHHA. The biceps angle adds another dimension in assessing the complex multi-factorial glenohumeral deformity in patients with residual brachial plexus palsy and may be used in conjunction with the glenoid version and PHHA.