Impingement occurs when the supraspinatus tendon or the region where the supraspinatus tendon is attached to the humerus contacts the under surface of the acromion and the coraco-acromial ligament.
In patients with impingement the pain occurs as the arm is lifted up away from the side of the body. It typically occurs at approximately 90 degrees abduction and commonly occurs as a painful catch.
Impingement can occur for a variety of reasons. Injury to the rotator cuff such as a tear or strain injury can cause the supraspinatus tendon to swell in which case it can be more prone to catching on the under surface of the acromion.
A spur may be another cause for impingement and can develop on the under surface of the acromion as part of the normal aging process. This spur can then dig into the superior surface of your rotator cuff.
Arthritis of the AC joint may also cause or contribute to impingement due to spurs forming on the under surface of the acromioclavicular joint.
Impingement can also occur with bursitis.
The initial treatment for patients with impingement will usually involve steroid injections to the subacromial space (which lies immediately under the acromion) along with physiotherapy. The aim of physiotherapy is to strengthen the remainder of your rotator cuff that is not involved and also to teach you to depress the humeral head as you lift your arm up to avoid the pinching phenomenon on the under surface of the acromion and the coraco-acromial ligament.
If treatment with physiotherapy and steroid injections is unsuccessful then surgery will usually be considered if you have impingement. Surgery in most cases will involve arthroscopic (key hole) surgery. This involves shaving off the under surface of the acromion and release of the coraco-acromial ligament. This provides more space for the rotator cuff tendons to fit under the acromion, hence allowing you to lift your shoulders up without catching. The subacromial bursa is also excised.
Post operative recovery following an arthroscopic acromioplasty is normally straight forward. Is is also a fairly rapid recovery. Surgery is not a particularly long often taking 15 minutes. There is no requirement for patients to wear a sling and you will normally be discharged from hospital the day following surgery. Recovery will normally occur within the first 6 weeks following surgery. Occassionally it can take up to 3 months following the operation for full recovery to occur.