Optimal needle electromyography approach to the serratus anterior muscle

There are two conventional needle electromyography (EMG) approaches to the serratus anterior (SA), both of which can result in erroneous insertion into adjacent structures such as the latissimus dorsi (LD), teres major, or external oblique abdominis muscles and pose a risk of long thoracic nerve (LTN) injury. Therefore, we identified a novel needle insertion point for the SA in cadavers that avoids other muscles and LTN injury.

This study included 17 cadavers: 12 to devise the new method and 5 to verify its accuracy. Novel landmarks were the inferior angle of the scapula (I), sternal notch (S), and xiphoid process (X). The relationships of the LD, pectoralis major (PM), SA, and LTN were determined relative to these landmarks.

When inserting a needle into the proximal one third along the line connecting points I and X, there were adequate safety margins around the LD, PM, and LTN, and the new method had excellent accuracy.

Compared to the conventional midaxillary method, our novel method improved the accuracy of needle EMG of the SA. Follow-up studies using clinical imaging techniques are needed to verify whether above findings are equally applicable in living subjects.