History of the Procedure
Distal clavicle osteolysis was first described in 1936 as a condition secondary to acute shoulder trauma. Today, it is described as a sequela of trauma associated with contact sports, falls, and motor vehicle accidents.
In 1959, distal clavicle osteolysis was reported in an air-hammer operator without evidence of acute trauma. In 1982, Cahill reported on 45 male athletes with distal clavicle osteolysis, confirming repetitive microtrauma as an etiology.  Of Cahill's 45 patients, 44 were weightlifters.
Distal clavicle osteolysis is a pathologic process involving resorption of subchondral bone in the distal clavicle. The condition usually presents as pain localized to the acromioclavicular (AC) joint. 
Although more than 100 cases have been reported in the US literature, distal clavicle osteolysis may be an underdiagnosed disorder. Its incidence has increased with the growth in popularity of weight training in the past 20 years. 
As more women are participating in competitive and recreational weight lifting and sports that involve overhead throwing, more women are presenting with cases of distal clavicle osteolysis.  In a retrospective review of 1432 consecutive magnetic resonance imaging (MRI) shoulder reports in patients aged 13-19 years, distal clavicle osteolysis was identified in 93 patients (6.5%), of whom 24% were female. 
Different theories concerning the etiology of distal clavicle osteolysis have been advanced:
The first theory proposed an autonomic neurovascular origin; one author noted the presence of ipsilateral anisocoria in four of eight patients
A theory set forth in another report proposed synovial invasion of the subchondral bone
Cahill, noting the presence of microfractures in subchondral bone in 50% of his cases, proposed that repetitive microtrauma caused subchondral stress fractures and remodeling  ; this theory is currently the most most widely accepted one
A case report of hypertrophic synovial tissue that migrated across the articular cartilage and invaded subchondral bone has been published, but most specimens show disruption of articular cartilage, subchondral cyst formation, and evidence of increased osteoclastic activity. 
Most patients present with pain over the distal end of the clavicle and AC joint, which is usually described as a dull ache. Patients with an etiology of trauma report a specific event as the start of their symptoms. In patients with repetitive/overuse injuries, pain is exacerbated by athletic or work activity. In weightlifters, most symptoms occur with the bench press and related exercises. 
On physical examination, patients have point tenderness over the affected AC joint, and cross-chest maneuvers elicit pain. Usually, the AC joint is not unstable; however, crepitation may be present. Range of motion (ROM) of the glenohumeral joint should be full.
The differential diagnosis must include metabolic (hyperparathyroidism), autoimmune (rheumatoid arthritis), and neoplastic (multiple myeloma) etiologies. Because distal clavicle osteolysis is usually a unilateral condition, inflammatory disease should be considered in bilateral cases.
Patients in whom conservative treatment fails or who refuse to limit their activities are candidates for surgical treatment.
The AC joint is a diarthrodial joint. The capsule of the AC joint is reinforced by the superior and inferior AC ligaments, with additional stability provided by the coracoclavicular ligaments. A fibrocartilaginous disk is present between the convex distal clavicle and the flat acromion, both of which are covered by hyaline cartilage.
The only contraindications noted for surgical treatment of distal clavicle osteolysis are those general to surgery. Most surgical approaches are best performed with general anesthesia; therefore, patients who have risks associated with general anesthesia should continue with nonoperative therapy.
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