Kinematic differences between children with obstetric brachial plexus palsy and healthy controls while performing activities of daily living.

Abstract

Residual shoulder dysfunction and deformity impacts on functional performance in children with obstetric brachial plexus palsy. Clinical understanding of upper limb dynamic movement patterns is difficult with observation alone. This case-control study describes the significant kinematic differences between children with obstetric brachial plexus palsy compared to typically developing children while performing tasks of the modified Mallet Scale. Eleven children with obstetric brachial plexus palsy (mean 10 years, range 7-15 years, Narakas group I-III) and 10 typically developing children (mean 9 years 9 months, range 6-15 years) completed three-dimensional upper limb motion analysis using the acromion method to track dynamic scapular movement. Kinematic data were captured by a 4-CODA cx1 optoelectronic tracking system. Participants performed three trials of the modified Mallet scale tasks. Local coordinate systems, segment and joint rotations were defined as recommended by the International Society of Biomechanics. Joint rotation angles against time of the glenohumeral, thoracohumeral and scapulohumeral joints were calculated. Kinematic findings demonstrated increased internal rotation in all postures, reduced glenohumeral excursion, habitual "trumpet" posture of glenohumeral abduction/elevation and variability in movement strategies. Scapulohumeral rhythm during abduction task was 1.88:1 in typically developing children and 1.04:1 in children with obstetric brachial plexus palsy. Children with obstetric brachial plexus palsy demonstrate deficient external rotation in all tasks. Despite increased postural internal rotation, ability to move through internal rotation range is compromised. The glenohumeral joint showed the greatest range deficit, contributing to abnormal scapulohumeral rhythm. Future sub-group analysis of Narakas Classification is recommended.