The deltoid extension lag sign for diagnosis and grading of axillary nerve palsy.

The deltoid extension lag sign has been developed to avoid the pitfalls confounding the diagnosis of an axillary nerve lesion. The physician elevates the arm into a position of near full extension. The patient is asked to attempt active maintenance of this position. If the deltoid is weak, the arm will drop. In five patients with traumatic axillary nerve palsy after anterior dislocation of the shoulder, the deltoid extension lag sign was used to evaluate the functional status of the deltoid muscle. The magnitude of the angular drop, or lag, of the arm was a precise indicator of the functional status and recovery of the deltoid. The sign proved to be objective and reproducible, allowing confident assessment of deltoid function and when repeated over time allowed precise follow-up of deltoid recovery.