Scapulohumeral reflex

The scapulohumeral reflex is a muscle stretch reflex to be differentiated from the scapulohumeral reflex (Shimizu). It is produced by percussing the inferior bony medial border of the scapula. A normal response is a retraction of the scapula as the rhomboid muscle contracts. The muscles which respond vary according to their degree of stretching at the time.

Since the rhomboid muscles are innervated by the dorsal scapular nerve (C5), absence of this reflex may indicate altered neurology at the spinal level, such as spinal cord or nerve root compression. Injury or compression to the dorsal scapular nerve may occur more peripherally and, indeed, a scapular subluxation may diminish the reflex.

It is not unusual in today's computer age with static postural fatigue to see more scapular subluxation in patients. Diligent neurological examination leads to evidence of reflex weakness.

Lower Third of Scapular Medial Border