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Acromioclavicular Joint Pathology
Acromioclavicular (AC) joint pathology can be divided into conditions that cause pain or conditions of instability that may cause pain or compromise function. AC joint pain can be secondary to a specific injury, from repetitive minor trauma, or as part of the aging process. The most common etiologies of pain are posttraumatic arthritis, persistent pain from a low-grade AC separation, primary osteoarthritis, rheumatoid arthritis, septic arthritis, sequelae of a prior fracture, and osteolysis of the distal clavicle ( Figs. 15.1–15.3 ). Instability occurs from trauma and includes type III, IV, V, and VI AC separations ( Fig. 15.4 ).
Acromioclavicular joint arthritis.
Deformity and elevation from prior healed distal clavicle fracture.
Apical tilt view of acromioclavicular joint arthritis.
Type V acromioclavicular joint separation on the right.
Literature Review
Adequate AC resection can be performed arthroscopically with satisfactory results. Snyder (see Buford et al.) and Flatow reported good results in 90% of patients. Neviaser demonstrated the efficacy of resecting only the medial acromion without resecting the distal clavicle. Both the direct approach to the AC joint and the indirect approach through the subacromial bursa appear to be equally effective. Arthroscopic reconstruction of the AC joint for dislocation has been reported extensively over the past several years. There are many techniques that are driven by new technologies.
Diagnosis
Painful Conditions
Patients complain of pain in the area of the AC joint during cross-body adduction (washing the opposite axilla or reaching for a seatbelt) or behind-the-back internal rotation (fastening a bra or pulling a belt through its loops). Weight lifters experience pain during a flat or inclined bench press. Physical examination demonstrates normal active and passive range of motion, with the exception of limited adduction or internal rotation due to pain. There is pain on direct palpation of the anterior or superior aspect of the AC joint. Selective injections (described later) are a useful adjunct.
Plain anteroposterior radiographs may demonstrate joint space narrowing, joint incongruity, inferior osteophytes, or distal osteolysis. A 15-degree apical tilt view may show the AC joint more clearly (see Fig. 15.3 ). Magnetic resonance imaging (MRI) commonly demonstrates AC joint arthritis in patients older than 40 years. The radiologist almost always mentions changes that are interpreted as AC arthritis. The surgeon should be careful to interpret such studies in light of an appropriate patient history and physical examination ( Figs. 15.5 and 15.6 ).
Instability
The diagnosis is much easier in patients with instability. They generally describe a trauma, such as a fall onto the shoulder. This may occur while playing sports, a fall from a height, or an injury related to a vehicle, such as a bicycle or motorcycle. The patient will present with a deformity at the AC joint representing elevation of the distal clavicle. Depending on the energy of the injury, there is soft tissue swelling and ecchymosis that extends over the lateral chest wall. The patient will often have trouble elevating the arm due to pain.
Differential Diagnosis
Some patients with superior labrum from anterior to posterior (SLAP) lesions have a presentation similar to that of patients with AC arthritis. Patients localize their pain deep to the AC joint and have pain with adduction and behind-the-back internal rotation. Specific AC tenderness to palpation is absent. Adduction is similar to the movement performed during the O'Brien test and may misdirect the surgeon. Traumatic AC separations are generally easy to diagnose so the differential diagnosis is not the main issue. However, the same trauma that causes an AC separation can injure other structures, so the surgeon should be aware of this potential ( Figs. 15.7 and 15.8 ).
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