Shoulder and elbow kinematics during the Mallet score in obstetrical brachial plexus palsy

The physical signs of obstetrical brachial plexus palsy range from temporary upper-limb dysfunction to a lifelong impairment and deformity in one arm. The aim of this study was to analyze the kinematics of the upper limb and to evaluate the contribution of glenohumeral and scapulothoracic joints of obstetrical brachial plexus palsy children.

Six children participated in this study: 2 males and 4 females with a mean age of 11.7years. Three patients had a C5, C6 lesion and 3 had a C5, C6, C7 lesion. They were asked to perform five tasks based on the Mallet scale and the kinematic data were collected using the Fastrak electromagnetic tracking device.

The scapulothoracic protraction and posterior tilt were significantly increased in the involved limb during the hand to mouth task (p=0.006 and p=0.015 respectively). The scapulothoracic Protraction/glenohumeral Elevation ratio was significantly increased in the involved limb during the hand to neck task (p=0.041) and the elevation task (p=0.015). The ratios of scapulothoracic Tilt on the three glenohumeral excursion angles were significantly increased during the hand to mouth task (p≤0.041). The scapulothoracic Mediolateral/glenohumeral Elevation ratio was significantly increased in the involved limb during the elevation task (p=0.038). The glenohumeral elevation excursion was significantly decreased in the involved limb during the hand to neck task (p<0.001) and the elevation task (p=0.0003).

This study gives us information about the greater contribution of the scapulothoracic joint to shoulder motion for affected arm of obstetrical brachial plexus palsy patients compared to their unaffected arm. Kinematic analysis could be useful in shoulder motion evaluation during the Mallet score and to evaluate outcomes after surgery.