Subacromial impingement syndrome is the most common shoulder disorder, accounting for 44 – 65% of all causes of shoulder pain. It is the condition in which the rotator cuff impinges on the surface of the acromion. It encompasses a spectrum of subacromial pathologies, including partial rotator cuff tears, rotator cuff tendinopathy, calcific tendinitis and subacromial bursitis.
Impact syndrome affects all subacromial tissues as a result of a reduction in subacromial space. The mechanisms of rotator cuff tendinopathy have been classically described as exogenous, endogenous or combinations of both. In endogenous impingement, rotator cuff tears occur as a result of the degenerative process that occurs over time due to overuse, overload or tendon injury. The constant repetitive movements of the arm above the level of the shoulder causes gradual deterioration of the joint. In exogenous impingement, inflammation and tendon degeneration occurs as a result of mechanical compression from structures external to the tendon, such as the anterior cochlea, coracromial ligaments and acromioclavicular joint.
Although impact symptoms may occur after trauma, pain usually develops insidiously over a period of weeks to months. The pain is usually located on the anterior-lateral surface of the acromion and often reflects on the outer surface of the arm. The pain is most severe at 60 – 120° of abduction, and the patient has difficulty raising their arm due to severe pain (painful arc of abduction). Patients usually complain of pain at night, which is exacerbated when lying on the affected shoulder. Normal daily activities, such as combing hair or opening a cupboard, become painful. Weakness and stiffness can also be treated, but are usually caused by pain.
X-rays of the shoulder can illustrate characteristic changes of the disease such as subacromial osteophytes, subacromial sclerosis, cystic changes of the greater humeral tuberosity and a decrease in subacromial distance. MRI provides details of possible sites of subacromial impingement, ossification of the coracromial ligament subacromial bursitis and the presence of fluid.
Initial treatment of impingement syndrome is conservative and includes analgesic and anti-inflammatory medications, shoulder immobilization, physical therapy with aggressive rotator cuff strengthening, steroid injections and PRP injections.
In case of failure of conservative treatment for a period of 4 to 6 months, surgical treatment is applied. This includes arthroscopic subacromial decompression/acromioplasty. Through a few small holes of a few mm in size, the lower surface of the acromion is shaved using appropriate instruments, thus enlarging the subacromial space. Many shoulder surgeons combine subacromial decompression with cleaning of the acromioclavicular joint. The procedure is performed under general or regional anaesthesia and takes 30 minutes. The patient can leave the hospital a few hours after surgery. The shoulder is immobilized with a simple suspension for a few days, recovery is rapid and within 15 days, the patient can return to daily activities.