Shoulder impingement syndrome is a syndrome involving tendonitis (inflammation of tendons) of the rotator cuff muscles as they pass through the subacromial space, the passage beneath the acromion. It is particularly associated with tendonitis of the supraspinatus muscle. This can result in pain, weakness, and loss of movement at the shoulder. Signs and symptoms
The most common symptoms in impingement syndrome are pain, weakness and a loss of movement at the affected shoulder. The pain is often worsened by shoulder overhead movement and may occur at night, especially when lying on the affected shoulder. The onset of the pain may be acute if due to an injury or insidious if due to a gradual process such as an osteoarthritic spur. The pain has been described as dull rather than sharp, and lingers for long periods of time, making it hard to fall asleep. Other symptoms can include a grinding or popping sensation during movement of the shoulder.The range of motion at the shoulder may be limited by pain. A painful arc of movement may be present during forward elevation of the arm from 60° to 120°. Passive movement at the shoulder will appear painful when a downward force is applied at the acromion but the pain will ease once the force is removed. Causes
When the arm is raised, the subacromial space (gap between the anterior edge of the acromion and the head of the humerus) narrows; the supraspinatus muscle tendon passes through this space.
Steroids
Therapeutic injections of corticosteroid and local anaesthetic may be used for persistent impingement syndrome. The total number of injections is generally limited to three due to possible side effects from the corticosteroid. A 2017 review found corticosteroid injections only give small and transient pain relief. Surgery
A number of surgical interventions are available, depending on the nature and location of the pathology. Surgery may be done arthroscopically or as open surgery. The impinging structures may be removed in surgery, and the subacromial space may be widened by resection of the distal clavicle and excision of osteophytes on the under-surface of the acromioclavicular joint. Damaged rotator cuff muscles can be surgically repaired. A 2019 review found that the evidence does not support decompression surgery in those with more than 3 months of shoulder pain without a history of trauma. A recent metaanalysis has further supported that early SIS would likely benefit from non-operative treatment modalities and surgical open decompression should be considered only with chronic presentation. History
Impingement syndrome was reported in 1852. Impingement of the shoulder was previously thought to be precipitated by shoulder abduction and surgical intervention focused on lateral or total acromionectomy. In 1972, Charles Neer proposed that impingement was due to the anterior third of the acromion and the coracoacromial ligament and suggested surgery should be focused on these areas. The role of anteriorinferior aspect of the acromion in impingement syndrome and excision of parts of the anteriorinferior acromion has become a pivotal part of the surgical treatment of the syndrome.