These occur as either a direct blow e.g. direct injury when rugby tackler takes the impact on the top of the shoulder. Most common mechanism of injury is falling onto the point of the shoulder. These injuries are particularly common in rugby players, cyclist and motor cyclists. Patients will feel pain over the top of the shoulder and often will have an abrasion just behind the AC joint.
There are various grades of injury;
Grade I – minor tear or strain of the capsule
Grade II – complete rupture of the capsule but the coracoclavicular ligaments
are intact. The end of collar bone rises up a small amount (Fig. 4)
Grade III – complete rupture of the capsule and the coracoclavicular ligaments; the end
of the collar bone rises right up (Fig. 5)
Grade IV – Grade III with the end of the collar bone tearing through the muscles at the
back of the AC Joint. The end of the collar bone comes to lie just under the skin.
Grade V and VI – more extreme types.
The patient points to the area of the AC joint as the site of their pain and there is tenderness over the AC joint often with bruising and there may be an abrasion over the top of the shoulder just behind the AC joint or over the shoulder blade. With Type III, IV and V there is an obvious deformity.
One must carefully examine the shoulder itself as there may be an injury to other structures e.g. the rotator cuff tendons. It may be difficult to ascertain this initially as the examination is hampered because of the patient’s pain.
Fig 4 – Grade II ACJ dislocation
Initially the patient may not be able to lift their arm at all. In Grade I, the x-rays are normal whereas in Grade II, the clavicle is slightly elevated (Fig. 4) .
An x-ray of the opposite side may be necessary for comparison to see subtle differences.
Fig 5 – Grade III ACJ dislocation
In Grade III onwards, the diagnosis is very clear on the x-ray (Fig. 5).
For Types I and II, the treatment is non operative with rest, icing and anti-inflammatories. If the pain does not settle within a few weeks then a cortisone injection can be given into the joint.
In Types IV, V and VI, surgery is indicated.
The treatment for Type III is controversial with some surgeons preferring to fix it and others leaving it. In most cases (90 – 95%) with a type III, when treated without an operation, the pain will settle and patients will regain full function of their arm but will have a ‘bump’ on the top of the shoulder. It essentially ends up being a cosmetic deformity.
In a person who works continually with arms above shoulder height, then surgery may be advised.
Recent literature has shown that there is a higher failure rate with early surgery as compared with late reconstruction.
Approximately 5 to 10% of patients with a type III dislocation will continue to be troubled by it. There may be persistent pain over the end of the collar bone or a nagging pain over the muscles of the shoulder blade. In these patients a late reconstruction may be done and the results of this are generally very good.
There are many different operations described and devices available for stabilizing the end of the collar bone.
The operations are aimed at reconstructing the torn coracoclavicular ligaments Fig. 6. This can be done using synthetic material, donor tendon or transfer of the patient’s own ligament. One of the more well recognised procedures is the modified Weaver Dunn operation (Fig. 6 and Fig. 7). In this operation, the coracoacromial ligament is detached form the acromion and is transferred into the cut end of the collar bone or clavicle.
Fig. 6 – Torn coracoclavicular ligaments
Fig. 7 – Modified Weaver Dunn Procedure