Impingement occurs when the supraspinatus tendon, or the region where it attaches to the humerus, makes contact with the under surface of the acromion and the coraco-acromial ligament. In effect, the tendon is being pinched in a space that has become too tight for it.
Symptoms
Pain occurs as the arm is lifted up and away from the side of the body. It typically occurs at around 90 degrees of abduction and commonly presents as a painful catch. This is a sharp, brief pain at a particular point in the arc of movement, rather than a constant ache.
Many people also describe pain reaching overhead or behind, and aching at night when lying on the affected side.
Causes
Impingement can occur for a variety of reasons.
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Rotator cuff injury. A tear or strain can cause the supraspinatus tendon to swell, making it more prone to catching on the under surface of the acromion.
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A bone spur. A spur can develop on the under surface of the acromion as part of the normal ageing process, and dig into the upper surface of the rotator cuff.
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AC joint arthritis. Spurs forming on the under surface of the acromioclavicular joint may also cause or contribute to impingement.
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Bursitis. Impingement commonly occurs together with inflammation of the subacromial bursa.
Treatment
Non-surgical treatment
Initial treatment usually involves physiotherapy, often alongside a steroid injection into the subacromial space, which lies immediately under the acromion.
The aim of physiotherapy is twofold: to strengthen the parts of the rotator cuff that are not involved, and to retrain the way the shoulder moves so that the humeral head is drawn downwards as the arm is lifted. That downward glide is what creates room under the acromion and avoids the pinching.
Surgical treatment
If physiotherapy and steroid injections are unsuccessful, surgery may be considered. In most cases this involves arthroscopic (keyhole) surgery called an acromioplasty, which means shaving the under surface of the acromion and releasing the coraco-acromial ligament. The subacromial bursa is also excised. This provides more space for the rotator cuff tendons under the acromion, so the arm can be lifted without catching.
As with any operation there are risks, including those of the anaesthetic, infection and post-operative stiffness. These are discussed individually in consultation before any decision is made.
Recovery
Recovery following an arthroscopic acromioplasty is normally straightforward and relatively quick. The surgery itself is short, often taking around 15 minutes. There is no requirement to wear a sling, and discharge from hospital normally occurs the day following surgery.
Recovery usually occurs within the first six weeks after surgery, though occasionally it can take up to three months for full recovery.
What to do next
If you have a catching pain when you lift your arm that has not settled with rest, see your general practitioner. A referral is needed to claim the Medicare rebate for a specialist consultation.
This page is general information and is not a diagnosis. Individual circumstances vary, and the right treatment for you can only be determined after assessment. Any procedure carries risk; these are discussed in consultation.
