Ultrasound Measurement of the Suprascapular Nerve in Asymptomatic and Painful Shoulders

Suprascapular nerve is the first nerve that branches from the upper trunk of brachial plexus. It receives signals transmitted from the fifth and sixth cervical root. The clinical importance of suprascapular nerve is mainly based on its distribution of 70% sensory innervation to the glenohumeral joint. After divided from the upper trunk, the suprascapular nerve goes laterally and posteriorly. First, it passes underneath omohyoid muscle, and then goes through the suprascapular notch and into the suprascapular fossa. At suprascapular fossa, the suprascapular nerve is just below supraspinatus muscle. If there are some problems inside the supraspinatus muscle, the suprascapular nerve below it could be compromised. After suprascapular nerve passes suprascapular fossa, it will cross spinoglenoid notch, then go into infraspinatus fossa and innervates infraspinatus muscle. Based on the important distribution of suprascapular nerve to the sensory and motor function of shoulder joint, it has great benefits to understand its normal and abnormal sonographic images in order to diagnose refractory shoulder pain cases. Although there are some studies trying to measure the size of suprascapular nerve, most of them are limited in its location at the supraspinatus fossa. Also, they do not take factors into consideration, such as the subject's sex, body index, orientation and if shoulder pain or not at that point. In conclusion, our study is aimed to explore the difference of the suprascapular nerves between the participants with and without shoulder pain and to investigate potential factors that may influence the nerve's size using high-resolution ultrasound.