Role of Ultrasound in Shoulder Impingement

Shoulder impingement syndromes and degenerative rotator cuff (RC) disease represent the main causes of shoulder pain . Impingement is classified into four types, depending on the site of soft-tissue entrapment: sub acromial, sub coracoid, poster superior inner and anterosuperior inner impingement. The sub acromial impingement syndrome is by far the most common in practice. . The clinical symptoms of sub acromial impingement include nocturnal pain and progressive, limited range of motion. At clinical examination, there is a painful area at 80-120° elevation, which is worsened during downward movements Osteophytes, or an abnormal shape of the acromion, sub acromial spurs, and the acromioclavicular joint, are common causes of compression at the rotator cuff and the overlying subacromial-subdeltoid bursa . Ultrasonography (US) is a commonly performed examination for shoulder impingement, recommended by experts as the first-choice technique to evaluate various shoulder diseases. Shoulder impingement is the most common and well-recognized indication for dynamic US in the shoulder.

Dynamic evaluation can be done by shoulder abduction or flexion with the probe placed at the end of the acromion in the coronal plane or in the sagittal plane. The two important points to be checked for shoulder impingement are the humeral head depression and tendon/bursal impingement . Because humeral head depression is essential to make enough space for the rotator cuff to slide beneath the acromion, the center of the humeral head normally moves inferiorly in the latter half of the cycle during shoulder abduction. When the humeral head does not move inferiorly or abnormally moves superiorly, the space for the rotator cuffs and the subacromial-subdeltoid bursa decreases and subacromial impingement can occur .

Magnetic resonance imaging (MRI) is currently considered the reference standard for imaging of shoulder disorders. The strength of MRI lies in its ability to assess sonographically inaccessible areas such as labrum, deep parts of various ligaments, capsule, and areas obscured by bone . MRI is the imaging study of choice for classifying tendon retraction and assessing the shoulder musculature. Its main disadvantage is being a static evaluation of the shoulder joint . There are several advantages of Ultrasonography over MRI. Ultrasonography has the benefit of being a dynamic form of imaging as compared to the static MRI. Ultrasonography is portable, quick, and a more cost-effective method. It is also better tolerated by the patient and allows interaction with the patient, who can point at the symptomatic area, thus optimizing the diagnostic yield.