INTRODUCTION
The acromioclavicular joint may endure traumatic lesions such as dislocations or fractures, but also wear of the joint by overuse called arthropathy.
ANATOMY ET PHYSIOLOGY
The acromioclavicular joint is constituted:
- on one side of the lateral or distal end of the clavicle,
- on the other side, with an extension of the scapula, called acromion.
This tiny superficial joint allows the clavicle to rotate from the front to the back when the arm goes above 90° in anterior active elevation.
The clavicle is maintained in its place by two types of ligaments:
one between the distal end of the clavicle and the acromion
two others that pull the clavicle downwards and are linked between the clavicle and an extension of the scapular called coracoid.
AC JOINT DISLOCATIONS
These are very frequent lesions and are different from the main scapula humeral shoulder joint and occur during trauma or falls, especially when skiing or playing rugby and other contact sports.
They are classified in different ways, but we will choose the classification with three stages of severity, depending of the upward migration of the clavicle in comparison to the acromion
Stage 1 - there is no deformity but on examination the acromioclavicular joint is sore.
stage 2– there is an intermediate migration of the distal clavicle visible on standard radiograph when compared to the opposite side.
stage 3 – the superior migration of the clavicle is maximum and all the ligaments which should maintain the clavicle in place are torn. The clavicle is then mobile, and you can press on it to reduce it, like on a piano
Conservative treatment is offered in most stage 1 and 2. A sling is needed for pain relief for approximately 10 days. It is important to state that in stage 3 AC joint dislocation the clavicle never gets back down to its initial position and leaves a definitive deformity.
Surgical treatment is indicated in grade 3 for patients who have fresh grade 3 injuries. For those who do a high amount of sporting activity, surgical treatment may also be offered several months after dislocation if persistent discomfort is present and unbearable. In which case, torn ligaments are not repairable and cannot be fixed. This is why artificial ligaments are used to fix the clavicle back in place.
DISTAL CLAVICLE FRACTURES
Distal clavicle fractures are rare and very often complex. They are classified in different types depending on the localization towards the ligaments, the amount of displacement and presentation of the fracture.
AC JOINT ARTHROPATHY
AC joint pathology is related to an overuse of the shoulder, physical work or excessive motion during sporting activity, for example intensive muscular strengthening at the gym. The arthropathy gives pain during shoulder motion, but also at night when the patient is laying on their side.
On examination the AC joint is sore.
On standard x-ray arthropathy shows with little black holes at the end of each part of the joint, like a mirror, at the end of clavicle and the acromion.
A test injection of the AC joint – a test guided injection under ultrasound or x-ray control is sometimes used to confirm the diagnosis. There is no arthritis in this case and the patient is often quite young.
If two injections do not relieve the pain for a long period of time, arthroscopic surgical treatment may be decided on. This consists of rimming the distal 5mm of the clavicle to check the two surfaces of the joint are no longer touching each other. Pain relief after such a procedure will be progressive in time.
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