The Acromio-Clavicular or ‘A-C’ Joint is formed by the junction of the clavicle and the acromion process of the scapula. It is supported by ligament structures (the A-C capsule and the two branches of the coraco-clavicular ligament), and also via dynamic muscular stabilisation provided by the upper trapezius, deltoid and pectoralis major. Because of its orientation, the A-C joint is vulnerable to downward shearing stress, so injuries are common in contact sports like AFL and rugby, but also any sport where there is risk of a heavy blow to the point of the shoulder—a fall off a bike for instance. In many directions the A-C joint is very strong; it needs to be in order to transmit forces from the arm to the trunk and vice versa! However, if sufficient downward force is applied to the tip of the acromion, the joint can injure easily, tearing the ligaments and driving a separation of the two bones.
Grades of injury vary, as does both their treatment and recovery time. Low grade injuries settle well and relatively quickly, but the highest grades may require stabilisation surgery and obviously imply longer rehab time.
Lower Grade strains:
Higher Grade injuries (dislocations):
Surgical fixation of A-C joint disruptions has been debated for many years, its popularity waxing and waning. In the 1970’s surgical fixation was deemed the most popular choice amongst orthopaedic surgeons, however by the 1990’s this had reversed and 72% of those surveyed favoured conservative management. Some believe that the high degree of disruption seen with Grade 3 leads to muscular fatigue and difficulty coping with loads overhead. Therefore, in sub-groups of patients who are involved with heavy manual labour, throwing sports, or are of an age where they are uncertain as to their future career, surgical fixation and/or reconstruction of the A-C complex will be considered.
A minority of cases will suffer from longer term instability and/or pain, particularly with overhead activities. Acceleration of degenerative change in the A-C joint is also frequently seen. For these patients, surgery may be warranted, usually taking the form of excision of the distal clavicle, A-C stabilisation and reconstruction of the coraco-clavicular ligaments. Variations on this may be favoured depending on the surgeon.
**Our Principal Physiotherapist at Belmont City Physiotherapy Clinic has been through the same injury process - sometimes first hand experience is unwanted but invaluable! If you have any queries, don't be afraid to ask!