Test your knowledge: anatomy of the suprascapular notch
...which structure passes through the suprascapular notch, and why is it so important?
Have you heard of that 0.5 to 1 cm notch located on the superior border of your scapula? Although inconspicuous, the suprascapular notch allows the passage of a structure that when damaged, severely limits the full range of movement of your arm.
The suprascapular notch houses the suprascapular nerve, an anatomical structure that ultimately innervates two muscles located posterior to the shoulder - the supraspinatus and infraspinatus. When this nerve is damaged, as seen in suprascapular nerve entrapment, the patient loses the ability to fully abduct and laterally rotate the arm.
The suprascapular notch is an indentation, or partial cavity, located on the superior border of the scapula, approximately two-thirds from its medial border. Passing superior to it is the superior transverse scapular (suprascapular) ligament, which closes the notch, transforming it into a complete cavity, or foramen, called the suprascapular foramen. For visualization purposes, you can imagine a valley being transformed into a tunnel by the ligament.
The suprascapular notch, and foramen, connect the base of the neck with the posterior region of the scapula, providing a route of passage for the suprascapular nerve.
This nerve originates from the superior trunk (C5, C6) of the brachial plexus, follows a posterolateral course through the posterior triangle of the neck and towards the suprascapular foramen. The suprascapular nerve then passes through the cavity to reach the posterior region of the scapula. In this region, it gives off an innervating branch to the supraspinatus muscle and then passes through the greater scapular notch to reach the infraspinatus muscle, innervating it. These two muscles are responsible for partial abduction and lateral rotation of the arm at the shoulder (glenohumeral) joint.
The importance of the suprascapular nerve becomes apparent in a condition called suprascapular nerve entrapment. An afflicted patient typically presents with a dull, aching pain located posterior to the shoulder, together with atrophy and weakness of the infraspinatus and supraspinatus muscles. As a result, the patient will have an abnormally limited abduction and lateral rotation of the arm.
Suprascapular nerve entrapment can have a variety of causes. Some of them include conditions that narrow the suprascapular notch itself and cause chronic irritation of the nerve, such as hypertrophy or ossification/calcification of the transverse scapular ligament. In addition, frequent exaggerated movements that directly stretch or injure the nerve are also common. For example, repetitive overhead activities, such as playing volleyball or painting a ceiling, or tears of the rotator cuff muscles can all lead to suprascapular nerve entrapment.
Treatment for this condition usually involves surgery, where the suprascapular notch is physically enlarged and an arthroscopic burr (rod) is inserted to protect the suprascapular nerve.