Injury Diagnosis

The physical examination forms an important basis for management and evaluation. The physical examination typically reveals medial deviation of the inferior angle of the scapula and prominent winging of the medial border of the scapula with backward pressure on the shoulder as in pushing off a wall. Superior elevation of the scapula is also noted. Overhead movements of the arm and shoulder cause significant discomfort and feelings of shoulder instability; many patients are unable to flex or abduct the shoulder beyond 90 degrees (shoulder level).

In the absence of established grading systems for the serratus anterior muscle, the degree of winging can be quantified by angle of posterior projection of the inferior scapular border from the chest wall at the point of maximal winging. British Motor Grading is applicable to examination of the other shoulder and arm muscles. Most patients with long thoracic nerve injury also show weakness of the deltoid and biceps muscles on examination.

EMG (electrical) testing of the long thoracic nerve and the serratus anterior muscle should be expected to find dysfunction in many cases. A normal EMG test is probably related to the difficulty of placing a recording needle within the substance of the serratus anterior muscle, given its relatively deep location on the chest wall. It has been our experience that electromyographers are sometimes reluctant to approach the serratus anterior with a recording needle for fear of traversing the chest wall and causing a collapsed lung. The tendency toward normal readings after serratus anterior testing may then be inferred as arising from inadvertent testing of the latissimus dorsi, teres major or other unaffected chest wall muscles.