Indications for Surgery
For open or closed surgery, the diagnosis of impingement must be watertight, subluxation must have been excluded, the patient must be over 35 years, must have failed to respond to conservative management, and must have had the symptoms in excess of 6 months, with no improvement.
A scheme for diagnosis is given in the algorithm shown in Figure 8.4. The patient will typically be a man of over 40 years who complains of true shoulder pain, which is exacerbated in the mid-range of elevation, a mid-range painful arc. The onset is usually insidious. If there is a history of trauma, then cuff tear and dislocation or subluxation should be excluded. If the painful arc is work- or sport-related then it may be physiological and a change in posture may be of benefit during working or sporting activities. Unfortunately, most patients will have worked this out for themselves before attending a surgeon and have not achieved success.
Figure 8.4 Diagnostic algorithm for impingement.
During the examination, particular attention should be paid to the tests for dislocation, the apprehension tests, sulcus sign and any joint laxity. If there is pain on cross-body adduction, attention should be paid to the acromioclavicular joint and the coracoid. If subcoracoid impingement is suspected, a CT scan should be performed. If there is excessive muscle wasting or weakness, the surgeon should suspect a cuff tear or neurological cause.
Three plain radiographs should be taken, an anteroposterior view of the shoulder, an axial and a subacromial arch view. If there are bone changes on the anteroposterior view (cysts or sclerosis of the greater tuberosity, sclerosis of the undersurface of the acromion, or a decrease in the acromiohumeral interval below 7 mm) then the patient has stage 3 impingement or cuff tear and is a poor candidate for arthroscopic treatment. Degenerative change in the acromioclavicular joint with inferior spikes means that the outer 1 cm of the clavicle may need to be excised, and this is best done with open surgery. If the arch view shows a Bigliani type 3 acromion, then a bony procedure must be performed.
The 'impingement test' should now be performed, 2 ml 1 per cent lignocaine (US: lido-caine) being injected just under the anterior acromion. The patient is re-examined at 5 minutes and, for a diagnosis of impingement to hold good, the patient's painful arc should have improved dramatically.
If the patient has had no previous conservative treatment and the time course is under 6 months' duration, then a single steroid injection of 40 mg depomedrone, or equivalent dosage of triamcinalone, may be injected under the anterior acromion, the patient being reexamined in 6 weeks. If the patient fails to respond to conservative measures, then surgery can be considered.