Anatomy
At the back of the upper edge of the scapula, in a small channel (incisura scapulae) closed by a ligament (ligamentum transversum), a nerve (N suprascapularis) runs which sends nerve fibres to parts of the shoulder joint capsule and upper and lower scapular muscles (M supraspinatus and M infraspinatus).
Right shoulder blade seen from behind:
A. Acromion
B. Cavitas glenoidalis
C. Fossa supraspinata
D. Spina scapulae
E. Incisura scapulae
F. Processus coracoideus
Cause
Repeated strain with movement in the shoulder joint, especially with the arm above the head, can cause pinching of the nerve (Mazza D, et al. 2021). Pinching of the nerve can also occur after direct trauma. Often it is a cyst (fluid-filled accumulation) that pinches the nerve (N. Suprascapularis). The cyst can be caused by an injury to the shoulder joint lip or a capsular tear (Strauss EJ, et al. 2020). The nerve is often pinched where it runs over the scapula (incisura scapula).
Symptoms
There is usually a burning or shooting pain in the shoulder. There may be a feeling of weakness in the shoulder. With prolonged symptoms, there is muscle wasting of the shoulder blade muscles (M supraspinatus and M infraspinatus).
Examination
Uncharacteristic shoulder symptoms that do not improve with relief should be examined by a doctor. If the findings from the medical examination raise suspicion of nerve entrapment, the diagnosis is made by examining the nerve conduction velocity (EMG). Often a cyst that is pinching the nerve can be seen on ultrasound scanning.
Treatment
Treatment includes relief from the painful activity, stretching and rehabilitation of the muscles around the shoulder. If relief and rehabilitation are not successful, ultrasound-guided drainage of the cyst and injection of adrenal cortex hormone can be attempted. If this is also unsuccessful, surgical treatment can be attempted (Mazza D, et al. 2021).
Rehabilitation
Relief is paramount and it is especially important that rehabilitation does not cause discomfort. Strength training should only be resumed once pain relief has been achieved.
Complications
If the progress is not smooth, you should consider whether the diagnosis is correct or if there are complications.
In particular, the following should be considered:
- Slipped disc in the nape of the neck
- Frozen shoulder
- Rupture of the upper shoulder blade muscle
- Inflammation of the tendon sheath of the upper shoulder blade muscle
- Inflammation of the bursa at the elbow
- Rupture of the biceps tendon
- Luxation of the shoulder joint
- Luxation of the joint between the shoulder blade and the collarbone
- Muscle infiltrations
- Meniscus lesion in the shoulder
