Acromioclavicular Joint Pathology

Abstract

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. Instability occurs from trauma and includes type III, IV, V, and VI AC separations. Pain can be addressed arthroscopically with distal clavicle excision. Instability can be addressed arthroscopically with stabilization procedures driven by new and advancing fixation technology.

Keywords

acromioclavicular joint, arthritis, instability, clavicle

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 ).

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 ).

Nonoperative Treatment

Nonoperative treatment for painful conditions is usually successful and consists of avoidance of painful positions and activities, nonsteroidal antiinflammatory (NSAIDs) medication, and injections. Because the pain from this condition is rarely disabling, patients are counseled to wait at least 6 to 12 months before they consider surgery.

Type I, II, and III AC separations are generally treated nonoperatively with time, oral NSAIDs, and benign neglect. Usually, pain and function is gradually restored over 4 to 12 weeks, depending on the patient’s desired activity and the grade of the injury. They occasionally cause long-term pain and may need surgical intervention in the future. Type IV and type VI separations are rare, but they always need open surgical reduction. Type V separations can be addressed nonoperatively, but they will result in moderate deformity, pain, and weakness. However, this is acceptable in some populations, including older individuals or any individual willing to accept the limited outcome.

Injection

Lesions of the AC joint and subacromial space are difficult to differentiate. AC arthritis can cause irritation of the underlying cuff, and the altered shoulder mechanics that accompany rotator cuff disease may aggravate an otherwise normal AC joint. A selective AC joint injection has two possible benefits: it may help the surgeon diagnose the primary source of pain, and it may be therapeutic if the cortisone diminishes joint inflammation. This can be done by palpation or it can be done with ultrasound guidance ( Figs. 15.9 and 15.10 ).

Indications for Surgery

Painful Conditions

Surgery is indicated when AC joint arthritis has been identified as the source of shoulder pain by patient history, physical examination, plain radiographs, and, when appropriate, MRI. Patients whose pain interferes with activities of daily living, work, or sports, and who have not responded to a minimum of 6 months’ conservative care are good candidates for arthroscopic AC joint resection. Patients with MRI evidence of AC joint arthritis, but whose pain is not localized to the AC joint, are not candidates for AC joint resection.

Operative Technique ( )

The two goals of arthroscopic AC joint resection are to remove the abnormal distal portion of the clavicle and to create enough space between the medial acromion and distal clavicle so that physical contact is eliminated during shoulder motion. Traditionally, open resection involves the removal of 1 to 1.5 cm of distal clavicle. Arthroscopic AC resection creates approximately 1 cm of space by removing 8 to 10 mm of distal clavicle and 1 to 2 mm of medial acromion.

Patient positioning and diagnostic glenohumeral arthroscopy are performed routinely. Any other procedures that need to be performed are completed first. This includes addressing all intra-articular pathology, rotator cuff repair, biceps tenodesis, and subacromial decompression if indicated.

Soft tissue débridement of the AC joint is done first while viewing from the posterior or lateral portal. If viewing from posteriorly, the lateral portal is the working portal. If viewing laterally, an anterolateral portal or posterior portal can be the initial working portal. Once the distal clavicle is exposed, a shaver or a burr is used to remove the undersurface of the acromial side of the AC joint ( Figs. 15.11–15.14 ).