Acromio-clavicular Joint Dislocation

By Joe F de Beer

Introduction

The acromio-clavicular joint is between the clavicle (collar bone) and the acromion (shoulder bone). This injury usually results from a fall onto the tip of the shoulder or on to the back of the shoulder. The acromion is driven downwards and the tip of the clavicle remains behind; this results in tears of ligaments which normally hold them together (Figure 1). Although the injury usually appears like the collar bone is pointing into the air, it is actually the other way around, with the shoulder blade hanging down. The injury is graded into different types depending upon the number of ligaments torn and direction of the dislocation.

Anatomy of Acromio-clavicular Joint Dislocations

The stabilising ligaments are:

1. Acromio-clavicular (AC) ligaments, (the capsule of the joint),
2. Coraco-clavicular (CC) ligaments (conoid and trapezoid).
3. Types (Grades) of dislocation: (Figure 2).

• Type I: Mild subluxation only involving a sprain of the capsular ligament.
• Type II: This is a tear of the capsular ligament but the important coraco-clavicular ligaments may still be intact.
• Type III: The coraco-clavicular and capsular ligaments are torn. This is the most common injury.
• Type IV: The tip of the clavicle is displaced to the rear.
• Type V: This is a severe upward displacement with the tip of the clavicle protruding up through the overlying trapezius muscle.
• Type VI: This is a downward displacement of the clavicle.

These injuries are common in contact sports and are often seen in rugby, and mountain biking.  Type III is commonly encountered in clinical practice.

Treatment of Acromio-clavicular Joint Dislocations

Type I and II:

Type I and II of Acromio-clavicular Joint Dislocations do not require surgery.

Patients with these injuries usually experience pain over the AC joint and there is swelling. They are usually managed conservatively and surgery is not necessary. Conservative treatment includes ice, rest and physiotherapy. A shoulder sling is not necessary to aid healing of the ligaments. The recovery is usually full with return to full and painless activity within a few weeks. Return to sport and other activities is safe as soon as the pain has settled.

Type III:

Type III of Acromio-clavicular Joint Dislocations can be managed conservatively, but due to the demands of sporting and other activites, it may need surgical reconstruction.

Type IV and V:

Early repair of type IV and V of Acromio-clavicular Joint Dislocations are usually indicated. These patients usually have a lot of pain due to the fact that the tip of the collar boner protrudes into the overlying trapezius muscle and non- operative management does not have a favourable outcome

What is meant by “Conservative management” of these injuries?

This would include ice, anti-inflammatory medicines, physiotherapy and later, exercises within pain limits.

More about the (common) Type III dislocation:

It is very seldom necessary to do an operation in the early period after the injury. The reasons are the following:

1. Many could be managed conservatively, but in more active people, reconstruction will be indicated.
2. In cases where conservative management fails, late reconstruction can be successfuly. 
3. Scapular Malpositioning and Rotatory Instability of the scapula: Those AC joint dislocations that do remain symptomatic are usually due to the fact that the shoulder blade is displaced downwards, pulling on the nerves above the shoulder as well as the muscles stabilising the scapula – causing symptoms into the shoulder and down the arm. (This type of displacement of the scapula or shoulder blade is referred to as “winging of the scapula”) Lameness, tingling of fingers and pain at the back in the area of the shoulder blade may result.This lame, tired, aching feeling is often relieved by supporting the elbow and relieving the downward traction of the arm. Carrying bags in the hand with the arm by the side also aggravates the pain down the arm. If scapula malpositioning is noticed directly after the injury, reconstruction is indicated.

Surgery for chronic Acromio-clavicular Joint Dislocations:

After years of experience of different procedures, we now use the LARS ligament for reconstruction of the AC joint.

The LARS ligament is a unique synthetic braided ligament of extreme strength.

After inserting it it acts as a lattice for the body to grow normal tissue into it, and to reconstitute ligamentous stability.

This procedure is usually very successful, and is done as a day case.

Details about LARS ligament:

Normal ligaments

The LARS ligament:  An extremely strong synthetic ligament, which enables normal tissue ingrowth

The ligament is introducted, and fixed with tiny screws to reduce the subluxed AC joint

Arthroscopic assisted reconstruction:

In most cases we pass the ligament around the coracoid with arthroscopic visualisation, and the fixation to the clavicle is done with a small exposure over the top of the clavicle.

Recovery:

The sling will be worn for about three weeks and during this post-operative time the patient is permitted to do movements of the arm without stressing it heavily. Gradual motion to normal activities will be permitted under supervision of the doctor and the physiotherapist.

Everyday activities like dressing, driving etc are permitted. Return to work will be very soon for people in less stressful occupations

Pain following the procedure is usually minimal and the symptoms down the arm are relieved soon after the operation

The success rate of this procedure has been very high with full return to pre-injury activities.

Further reading

National Institutes of Health (NIH) (.gov)