Acromioclavicular Joint Injuries

The acromioclavicular (AC) joint connects the arm to the chest and is seen as an important structure providing the “strut” function of the upper extremity. Injuries may result from direct or indirect trauma. The involvement of intrinsic and/or extrinsic ligaments is responsible for several injury patterns. The extent of AC joint injuries range from mild sprains of the AC capsule with preservation of the coracoclavicular (CC) ligaments to complete tearing of both the AC capsule complex and the CC ligaments. Peculiar radiographs are needed for a precise diagnosis; however, more accurate analysis involving Magnetic Resonance Imaging (MRI) or Computerised Tomography (CT) helps detect associated injuries. Minor trauma typically only affects the AC capsuloligamentous complex and a conservative approach usually yields satisfactory functional outcomes. Persistent instability and unsatisfactory outcomes are common (20–40%) after conservative treatment when coraco-clavicular ligaments or the trapezius fascia are involved as a result of significant trauma. Surgery may be advised in these circumstances to control inferior-superior as well as horizontal instability; however, the timing of such surgery guides selection of appropriate technique for stabilisation. For example internal CC-fixation with synthetic loops and cortical buttons may be proposed in the acute situation. In chronic cases healing of the ligaments is no longer possible; therefore, any fixation device should ideally be reinforced with a biologic soft tissue graft. Great care should also be taken to control anterior-posterior instability especially in high demand patients since it is one of the most common reasons for poor results. Hence, an additional AC capsuloligamentous augmentation should be considered. When key treatment principles are followed, satisfactory outcomes can be expected.