Osteolysis of the Distal Clavicle
Readily Detected and Treated Shoulder Pain
Melissa Stephens, MD; Preston M. Wolin, MD; Joyce A. Tarbet, MD; Mohammed Alkhayarin, MD
THE PHYSICIAN AND SPORTSMEDICINE - VOL 28 - NO. 12 - DECEMBER 2000
In Brief: Osteolysis of the distal clavicle is a pathologic process involving resorption of the distal clavicle and is usually posttraumatic or caused by the repetitive microtrauma of weight lifting. Pain localized to the acromioclavicular joint and radiographs or bone scans showing pathology in the distal clavicle are diagnostic. Modification of activities, such as curtailment of weight lifting, often alleviates symptoms, but surgery is an option when conservative measures fail or for patients who cannot limit their activities.
Disorders of the acromioclavicular (AC) joint are a common cause of shoulder pain and generally involve the ligaments, bones, or articular surfaces. Isolated involvement of the articular surface can result from arthritis or osteolysis. Osteolysis of the distal clavicle is typically associated with AC pain and, on radiographs, a loss of subchondral bone detail, AC separation, and cystic changes (1).
Cahill (2) credited Dupas with the first reported case of osteolysis of the distal clavicle. In 1936, Dupas reported a case of progressive osteolysis following a traumatic episode. Since that time, several others have reported similar traumatically induced cases (3). In 1959, Ehricht (4) reported the first case of atraumatic osteolysis of the distal clavicle, occurring in an air-hammer operator. Others (5-7) subsequently reported osteolysis of the distal clavicle in a deliveryman, a judo artist, and a handball player.
In 1982, Cahill (2) reported the first series, which included 46 patients with atraumatic osteolysis of the distal clavicle. He noted that all of the patients were male and involved in weight training. Since this report, there have been more than 100 cases reported, most of which involved male weight lifters. More recently the condition has been reported in a female bodybuilder (8). Regardless of the cause, physicians need to have a firm grasp of the anatomy, etiology, and diagnostic findings to optimize treatment.
Anatomy of the AC Joint
"Shoulder" is a general term used to describe a complex structure that includes the clavicle, scapula, and humerus as well as all of the muscles and ligaments that connect these bones (figure 1). The AC joint is a diarthrodial joint connecting the convex distal clavicle with the flat or slightly concave acromion. The degree of congruence between these two surfaces is highly variable, as is the amount of medial inclination. A fibrocartilaginous meniscal disk separates the two hyaline-covered articular surfaces in adolescence. In adults the disk is often small or ill-defined (9). The joint is stabilized by the coracoclavicular ligaments (conoid and trapezoid), the AC ligament, and the AC capsule. These ligaments limit the amount of motion allowed at the AC joint to about 10° of rotation as the arm is taken into full elevation (10).
Etiology of Osteolysis
The mechanical cause of atraumatic osteolysis appears to be repetitive microtrauma to the shoulder (eg, caused by weight-training exercises), whereas traumatic osteolysis is induced by a single blunt trauma to the shoulder. The pathophysiology for both mechanisms remains unclear. Several hypotheses have been proposed, including vascular compromise, nervous system dysfunction, microfracture, and stress-induced osteoclastic resorption (11).
Madsen (12) postulated nerve dysfunction after noting anisocoria in four of eight patients. Cahill (2) found 50% of the distal clavicles that he surgically removed for osteolysis had microfractures. He postulated that these microfractures initiated an osteolytic process. Brunet et al (11) described the histologic findings in one case of atraumatic osteolysis. They found inflamed synovial tissue extending from the surface into the bony distal clavicle with fibroblastic proliferation and inflamed synovial tissue filling the bony voids.
In both traumatic and atraumatic osteolysis, the patient usually reports a dull ache that localizes over the AC joint. It may radiate to the anterior deltoid or the trapezius. With posttraumatic osteolysis, the patient will relate the onset of the pain to a direct blow to the shoulder. The traumatic episode may be as recent as 4 weeks, or it may have occurred years prior to the patient's presentation (13). These patients may or may not be involved in repetitive physical activities with the affected shoulder.
With atraumatic osteolysis, the patient has an insidious onset of pain in the region of the AC joint. These patients are usually weight lifters or heavy laborers who do not recall a specific incident that precipitated their symptoms. Weight lifters often have the most pain while performing bench presses, push-ups, and dips (2). Night pain is not often a complaint, but the patient will have difficulty sleeping on the affected side (9). Activities of daily living may become painful as the patient's symptoms progress (14).
On physical examination, patients consistently exhibit point tenderness over the AC joint and pain with cross-body adduction. Patients generally have well-developed shoulder musculature and full range of motion, but they can have pain with the impingement test, making diagnosis difficult. In this situation, 1 mL of 1% lidocaine hydrochloride can be injected directly into the AC joint. Patients with isolated distal clavicle osteolysis will have a temporary resolution of their symptoms after injection, whereas patients with other shoulder pathology will continue to have pain with provocative testing.
Radiographic evaluation should include an anteroposterior (AP) view and a 10° to 15° cephalic tilt AP view. X-rays taken soon after the onset of symptoms may appear normal; however, months or years later, loss of subchondral bone detail in the distal clavicle, microcystic changes in the subchondral area, and widening of the AC joint may be visualized (2). The acromion in osteolysis reveals no pathologic changes, differentiating it from AC arthritis (3) (figure 2). Joint scintigraphy with cone-down views of the AC joint demonstrates marked uptake in the distal clavicle, and it should be used if x-rays are normal (figure 3). Although rarely indicated for isolated osteolysis, magnetic resonance imaging (MRI) consistently shows a bright signal in the distal clavicle on T2-weighted imaging, signifying edema (figure 4). Atraumatic and traumatic osteolysis have similar MRI findings (12).
Other shoulder problems that specifically affect the AC joint, such as AC separation and arthritis, can mimic osteolysis. Patients with glenohumeral pathology may also have pain referred to the AC joint; therefore, glenohumeral instability, labral tears, and rotator cuff pathology should be ruled out. Multiple myeloma, Gorham's massive osteolysis, steroid arthropathy, and aggressive rheumatoid arthritis are problems that can occasionally produce similar clinical and radiographic findings (6).
Treatment of the patient with osteolysis needs to be individualized. Factors to be considered include the extent of disability, hand dominance, activity level, and age.
Nonoperative treatment. Patients are initially started on a nonsteroidal anti-inflammatory drug (NSAID) and instructed in activity modification. Specifically, weight lifters should avoid bench presses, dips, flies, push-ups, and other lifts that elicit pain. Most patients will respond to activity modification; however, symptoms often recur if the previous weight-training schedule is reinstituted (2). Intra-articular corticosteroids can be considered for short-term symptom relief, but studies to date have not shown any long-term benefits (11). Because patients generally retain normal shoulder function, formal physical therapy is generally not initiated unless there is concomitant shoulder pathology. Patients whose condition does not respond to conservative management or who cannot limit their activities require surgery.
Operative management. Both open and arthroscopic distal clavicle resection have been successful in alleviating pain and returning patients to previous activity levels (2,9,10,14-17). Open resection is a relatively simple procedure, but a 4- to 5-cm incision is required. It also entails at least partial detachment of the deltoid; therefore, patients must avoid strenuous use of the arm for 3 to 4 weeks. The arthroscopic technique is technically more demanding, but it is more cosmetically appealing, and patients return to activities as soon as they are comfortable (18).
The amount of distal clavicle that needs to be resected remains controversial. The early open procedures advocated resecting 10 to 20 mm, but the need for such a large amount of resection has been questioned. A recent study (19) reported that arthroscopic resection of only 4 mm was effective. The amount resected should prevent impingement at the AC joint as the shoulder is brought into flexion and adduction (figure 5).
The patient with osteolysis of the distal clavicle usually reports a dull ache over the superior aspect of the shoulder. The pain is exacerbated by activities involving shoulder flexion and adduction. History, physical exam, and plain x-rays usually suffice to make the diagnosis. Modification of activities is the mainstay of conservative treatment, but NSAIDs and corticosteroid injections can provide short-term relief. When conservative management fails, operative resection of the distal clavicle provides good to excellent results with few complications.