Background: Approximately 1 of every 1000 live births results in life-long impairments because of a brachial plexus injury. The long-term sequelae of persistent injuries include glenohumeral joint dysplasia and glenohumeral internal rotation and adduction contractures. Scapular winging is also common, and patients and their families often express concern regarding this observed scapular winging. It is difficult for clinicians to adequately address these concerns without a satisfying explanation for why scapular winging occurs in children with brachial plexus birth palsy. This study examined our proposed theory that a glenohumeral cross-body abduction contracture leads to the appearance of scapular winging in children with residual brachial plexus birth palsy.
Methods: Sixteen children with brachial plexus injuries were enrolled in this study. Three-dimensional locations of markers placed on the thorax, scapula, and humerus were recorded in the hand to mouth Mallet position. The unaffected limbs served as a control. Scapulothoracic and glenohumeral cross-body adduction angles were compared between the affected and unaffected limbs.
Results: The affected limbs demonstrated significantly greater scapulothoracic and significantly smaller glenohumeral cross-body adduction angles than the unaffected limbs. The affected limbs also exhibited a significantly lower glenohumeral cross-body adduction to scapulothoracic cross-body adduction ratio.
Conclusions: The results of this study support the theory that brachial plexus injuries can lead to a glenohumeral cross-body abduction contracture. Affected children demonstrated increased scapulothoracic cross-body adduction that is likely a compensatory mechanism because of decreased glenohumeral cross-body adduction. These findings are unique and better define the etiology of scapular winging in children with brachial plexus injuries. This information can be relayed to patients and their families when explaining the appearance of scapular winging.
Level of Evidence: Level II.