Acromioclavicular or AC Joint
The AC joint is located at the top of the shoulder where the acromion (part of the shoulder blade or scapula) and collarbone (clavicle) form a joint (Figure 1).
Fig. 1 – Acromioclavicular Joint (AC Joint)
The joint is enclosed in a capsule or sac and there is a disc of tissue (meniscus) which lies between the two bones.
Fig. 2 – Coracoclavicular and acromioclavicular ligaments
The collar bone is held down against the acromion by the capsule and the coracoclavicular ligaments. The acromioclavicular ligament passes from the acromion to the coracoid bone (Fig. 2).
The AC joint is a common site of pathology and of injuries to the shoulder.
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Conditions of the AC Joint
CONDITIONS OF THE AC JOINT
1. Injuries
2. Overuse and osteolysis
3. Osteoarthritis (wear and tear)
Condition 1 - Injury
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.
Clinical Features
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).
Treatment
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.
SURGERY
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
Condition 2 - Overuse and Osteolysis
OVERUSE AND OSTEOLYSIS
The AC joint may become painful because of overuse that may occur in overhead sports and in weight training.
Clinical Features
The onset is usually gradual and patients feel the pain right over the top of the shoulder and can point exactly to the spot. The pain may radiate into the neck and is exacerbated when the patient lies on the shoulder. Overhead activities, putting hand behind their back and taking the arm across the body will bring on or exaccerabate the pain. The features on examination are classical with point tenderness over the AC joint, pain on cross body adduction, pain on resisted adduction and pain on distraction test.
X-rays
Fig. 5 – Osteolysis
These may be completely normal. In weight lifters there may be Osteolysis of the end of the clavicle where on x-ray the end of the bone becomes fuzzy, eaten away or disappears
(Fig. 5).
Treatment
Initially is rest, icing and anti-inflammatories. If this treatment is unsuccessful then a cortisone injection is given. These are very effective (a course of injections may be necessary) and in one study where patients were followed-up 5 years after injection, 80% still had no recurrence of pain. If the injections do not resolve the condition then an arthroscopy and excision of the end of the clavicle may be performed.
Condition 3 - Osteoarthritis
OSTEOARTHRITIS
Osteoarthritis or ‘wear and tear’ of the clavicle is very common. Many people will have this but not have pain from it. In one study where people without shoulder pain had an MRI of their shoulder; there were wear and tear changes in 60% of people at 40 years of age and changes in 90% of people at 60 years of age.
Clinical Features
Some people may just notice a bump on the top of their shoulder. Some people however do develop pain. The clinical features are as above.
X-rays
Fig. 6 – Osteoarthritis
X-rays may show narrowing of the joint space between the acromion and clavicle, cysts in the end of the clavicle and/or osteophytes (spurs; extra bone formation) at the edges of the joint (fig. 6).
Treatment
Is the same as above, where initially anti-inflammatories are tried, then injection and finally arthroscopy and removal of the end of the clavicle.
SURGERY
The surgery is done arthroscopically (‘key hole’) and involves removing a small amount of bone from the end of the clavicle so as to produce a gap of approximately 1 cm between the clavicle and acromion. Thus the two bones no longer rub together causing pain, the meniscus is also removed which is often damaged. This 1 cm gap fills with scar tissue and the bones continue to move together as a joint but without any pain and there is no loss of strength. The results of this procedure are excellent (>95% success rate). It may however take patients up to 6 months to be functioning completely normally.
Surgery procedure
Shoulder Arthroscopy
Most surgical procedures of the shoulder are now performed with arthroscopy. This involves the inserting of a telescope (fibre optic) through a thin tube in small incisions around the shoulder. The incisions are between 0,5 to 1,0 cm in size and between 2 and 6 incisions are used depending what operation is done. A single stitch or suture is used to close the incisions after the operation.
This is less invasive but the operation inside is the same as those done with an open operation and thus recovery may still take months depending on the procedure performed.
ARTHROSCOPIC PUMP
To facilitate the arthroscopic (keyhole) surgery, fluid is pumped into the shoulder. This opens the spaces in the shoulder and prevents bleeding. During the procedure some fluid leaks into the tissues around the shoulder which can become very swollen. This fluid is absorbed over the following few hours and patients may find that they pass more urine during this period as this fluid is excreted. Some of this fluid which is blood stained leaks out the small incisions and an absorbent dressing (nappy) is strapped to the shoulder. This is left on overnight and is replaced with small waterproof dressings the next morning so that the patient can shower normally.
This bloody fluid tracks down between the skin layer and muscle and patients may develop quite marked bruising down their arm and over their chest/breast during the week following the operation. This bruising will disappear over 2 -3 weeks.
ANAESTHESIA
This is done with a general anaesthetic and a regional block. It can be done with a block alone but the patient is placed into a seated position on the operating table which can be uncomfortable and thus a general anaesthetic is preferred. The block is done with local anaesthetic injected into the side of the neck where the nerves to the arm are passing. This provides excellent pain relief during the operation thus less anaesthetic drugs are required, patients thus wake up quite refreshed afterwards. The block provides excellent relieve of pain after the operation and lasts for between 8 and 24 hours. The arm may be completely dead and the patient may not even be able to move their fingers initially. Care must be taken not to put anything hot on the arm as this will not be felt and a burn may occur. In approximately 1% of cases there may be a persisting area of numbness in the arm, forearm or hand which usually disappears within 3 months. Occasionally neuralgia (nerve pain) may occur after the block and may require medication till it settles of its own accord.
HOSPITAL STAY
Patients come in on the day of the operation and may be discharged a few hours after the operation or may stay overnight depending on the operation performed and how they are feeling.
MEDICATION
An anti-inflammatory and a pain killer are prescribed. The anti-inflammatory is taken for a week and the pain killer if and when necessary. Most patients take the pain killer for an average of 5 days after the operation. Some patients however don’t take any medication whereas other patients may need pain killers for up to 6 weeks. This is dependent on the individual and the operation performed. More pain is usually felt following a rotator cuff repair. Patients often struggle to sleep initially and a sleeping tablet may be required.
SLEEP
Patients often have difficulty sleeping and besides taking sleeping tablets, sleeping propped up with pillows or sleeping in a chair will be easier. A recliner (lazy boy chair) will often be the best option.
Anaesthesia
The anaesthetist will see you in the ward prior to the operation or in the reception room in theatre. If you have medical problems; eg: heart condition, previous cardiac surgery, chest disease (eg: emphysema), you will be referred to a physician for an assessment and may see the anaesthetist a few days prior to the operation. A premed is sometimes given prior to theatre which will make you a little drowsy and relaxed. In theatre you will sit on the theatre table and make yourself comfortable prior to the induction of anaesthesia. A drip will be inserted into your arm through which the anaesthetic drugs are administered. Gases will be given by a mask and once you are asleep a tube will be inserted into your throat, this is why you may have a sore throat for a short time after the operation.
The anesthetic is a general anaesthetic with a regional block. It can be done with a block alone but you are placed into a seated position on the operating table which can be uncomfortable and thus a general anaesthetic is preferred. The block is done with local anaesthetic injected into the side of the neck where the nerves to the arm are passing (essentially an epidural of the arm). This provides excellent pain relief during the operation thus less anaesthetic drugs are required; you tend to wake up quickly and are quite refreshed afterwards. The block provides excellent relieve of pain after the operation and lasts for between 8 and 24 hours. The arm may be completely dead and you may not even be able to move your fingers initially. Care must be taken not to put anything hot on the arm as this will not be felt and a burn may occur. In approximately 1% of cases there may be a persisting area of numbness in the arm, forearm or hand after the block has worn off. This numbness will usually disappear within 3 months. Occasionally neuralgia (nerve pain) may occur after the block and may require medication till it settles of its own accord. Although extremely rare, permanent nerve damage has been reported.
You tend to wake up very quickly after the operation and may eat soon afterwards. The drip will be taken down when you are back in the ward. The block provides excellent pain relief for between 8 and 24 hours but pain killers and anti-inflammatories are started before the block wears off so that they are already working when the pain starts. Patients vary in the amount of pain killers that they need; some don’t need to take any whereas others may need to take them for up to 6 weeks.
