Case of the Month #34: Shoulder Pain by Dr Sunil Dasari

What is impingement syndrome? What are the causes of impingement syndrome?

Impingement syndrome is a condition in which the tendons of the rotator cuff of the shoulder are pinched as they pass between the top of the humerus and acromion. It is believed to be the most common cause of shoulder pain accounting to 44-65 % of all shoulder complaints¹, and is diagnosed from history and physical examination. The subacromial space is normally 1.0 to 1.5 cm in width. Shoulder abduction, forward flexion, and internal rotation results in narrowing of the subacromial space with the superior migration of the humeral head approaching the anteroinferior edge of the acromion.² The symptom of pain associated with shoulder impingement results with this movement due to the humeral head applying a compressive force to either the rotator cuff, the subacromial bursa, or both structures. Measurements such as the acromiohumeral distance (AHD) in X-rays can help to detect
rotator cuff pathologies and defects. The AHD is measured from the inferior edge of the acromion to the humeral head. The normal range is approximately 7 to 14 mm in men and 7 to 12 mm in women. A lower AHD suggests rotator cuff pathology.²
Repetitive pathologic compression, degeneration, and fraying of the rotator cuff tendons are known to contribute to the narrowing of the subacromial space.² Other causes include sub-acromion bursitis, age related bone spurs and anatomical variation where the acromion is not flat.
More common in individuals who participate in sports and activities that require repetitive overhead activities.
The incidence of shoulder impingement syndrome rises with age, with peak incidence
occurring in the sixth decade of life.³

How is it diagnosed?

It is diagnosed from the history and examination. If there is any suspicion of rotator cuff tear, it needs investigation with Ultrasound or MRI of shoulder.