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Subacromial impingement is a common condition affecting patients from all ages above about 30 years. It is characterized by a generalized pain in the region of the shoulder that is made worse by movement; elevation of the arm above shoulder level and the action of putting on a coat often exacerbate the pain. Pain at night, particularly when lying on the affected side, is a frequent occurrence. Symptoms usually appear spontaneously without a history of injury. Initially symptoms are intermittent and mild and patients will often wait several months before seeking medical advice.
Pain is caused when the supraspinatus tendon, part of the rotator cuff (see Shoulder anatomy) is squeezed between the humeral head and the acromium (part of the shoulder blade). Once symptoms have become established the pathology is often self perpetuating; every movement of the shoulder results in more inflammation of the supraspinatus, which in turn becomes more swollen and susceptible to further impingement.
It is uncertain as to what initiates the process of subacromial impingement. In some cases there may be an anatomical abnormality such as a spur of bone on the acromium or a small tear in the supraspinatus tendon that starts the process, but in most cases there is no obvious cause.
The classical presentation of subacromial impingement is of a patient who complains of maximal pain when the arm is held a shoulder level (the painful arc). Power in the shoulder is normal and the range of movement is not normally severely restricted.
Plain radiographs may show a subacromial spur.
MR scanning may show abnormality within the tendon of the supraspinatus; it will also show whether there is an associated cuff tear. However scanning is not normally required to make the diagnosis and should be only be considered if surgery is contemplated.
Most cases of subacromial impingement will respond to conservative measures and only a small proportion of patients will come to surgery. The treatment options are:
- Simple analgesia Subacromial impingement is often self limiting. Treatment with simple pain killers such as paracetamol or anti-inflammatories (e.g. ibuprofen) may well be sufficient.
- Physiotherapy Physiotherapy designed to strengthen the rotator cuff muscles may be helpful.
- Intrabursal steroid In cases that do not respond to the above measures an injection of steroid into the space around the shoulder (the subacromial bursa) may be considered. Steroids reduce inflammation and will prevent the repeated impingement on the supraspinatus tendon; by breaking this 'vicious circle' an injection will often result in a long term cure. Injections have a reputation for being painful; whilst patients may experience increased discomfort for 48 hours following injection, this is rarely severe.
- Subacromial decompression When all conservative treatment options have failed surgery may be considered. This is an operation to increase the space between the humerus and the acromium. It may be done through a short incision at the front of the shoulder, but more frequently done by arthroscopic ('keyhole') surgery. To read more about this click here.
|© J M Britton 2007|