Acromioclavicular (AC) joint injuries represent nearly half of all athletic shoulder injuries. The injury is caused by direct impact to the point of the shoulder from a fall. Injury to the acromioclavicular joint involves failure of the AC ligaments and capsule followed by failure of the coraco-clavicular ligaments and deltotrapezial fascia. The classification system put forth by Rockwood is commonly used to describe the extent of the injury.
As outcomes correlate well with the grade of injury, knowing the grade is crucial in dictating the appropriate treatment. It is important to note that while MRI is being used more commonly to evaluate injuries, plain radiographs of the AC joint are all that is needed to establish the grade of injury.
The classifications are as follows:
Type I- AC ligament sprain with the AC joint not dislocated.
Type II- AC ligament tear, and coracoclavicular ligaments intact
Type III- AC and coracoclavicular ligaments torn with 100% AC joint dislocation.
Type IV- Complete dislocation with posterior displacement of the distal clavicle throught the trapezius muscle.
Type V- exaggerated superior dislocation of the AC joint between 100% and 300%, a 2-3 times
increase in the coracoclavicular distance (normal 1.2cm), involving disruption of the deltotrapezial
fascia.
Type VI- complete dislocation with clavicle under the coracoid (extremely rare).
Grade 1 and 2 injuries are managed well conservatively with Physiotherapy. Grade 4 and above require surgery to restore the anatomical position. Grade 3 injuries remain controversial but the trend is towards conservative management. Your Physio will take you through a rehabilitation program aimed at reducing pain initially, restoring scapular mechanics and pain free range of movement and progressing to rotator cuff strength as the joint stabilises. Comprehensive rehab of Grade 1-3 AC joint injuries is essential to reduce the likelihood secondary problems, especially in overhead athletes and labourers.
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