A Cadaveric Study on the Surface Projection of the Dorsal Scapular Nerve

Background: Dorsal scapular nerve (DSN) syndrome is often associated by dull or aching pain along the medial border of the scapula that can radiate to the lateral aspect of the upper limb. The primary cause of this syndrome is due to the impingement or entrapment of this nerve at the middle scalene muscle. The purpose of this study is to identify the surface projection of the DSN relative to the middle scalene muscle by using the transverse plane of the laryngeal prominence and the posterior border of the sternocleidomastoid (SCM) muscle as reference points along with approximating the nerve's location using thumb interphalangeal joint (IPJ) width. Methods: The surface location of the DSN was examined in 10 embalmed adult cadavers. The posterior border of the SCM muscle was palpated and outlined along with the transverse plane of the laryngeal prominence. A resin dye was injected at a distance of 2.08 cm (~ 1 thumb IPJ width) medial to the intersection of the posterior border of the SCM and the transverse plane of the laryngeal prominence. Dissections were performed to reveal and record the location of the dye. The distance between the location of the dye to the DSN was also measured. Results: The overall accuracy of the injection study revealed that the scalene muscles were consistently located. Specifically, 50% of the injections were found at the middle scalene muscle, 20% was between the anterior and middle scalene muscles, 10% at the anterior scalene muscle, 10% between the middle and posterior scalene muscles, and 10% was located at the posterior scalene muscle. Conclusion: This investigation will provide clinicians a useful and convenient method to determine the surface projection of the DSN at its entrapment site for the purpose of diagnosis and therapeutic treatment.