Clavicle fracture classification
When an orthopaedic surgeon is evaluating a clavicle fracture he or she tries to classify the type of fracture into one of three groups:
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Group I: the clavicle is fractured in the middle of the bone. This is the most common region in which the clavicle is fractured in both adults and children, making up about 80% of all clavicle fractures. The medial bone fragment (the half of the bone next to the sternum) usually displaces upward due to the pull of the sternocleidomastoid muscle on that portion of the clavicle. The lateral fragment (the half of the bone that is toward the shoulder) is pulled downward by the weight of the arm.
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Group II: the clavicle is fractured at the distal third of the bone (toward the shoulder). This fracture pattern accounts for 10-15% of all clavicle fractures. Group II fractures may be subdivided into three separate types:
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Type 1: there is minimal displacement of the two ends of the bone
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Type 2: the fracture is medial to a group of ligaments called the coracoclavicular ligaments. These ligaments, along with the ligaments of the AC joint, connect the clavicle to the scapula.
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Type 3: the fracture involves the articular joint surface of the AC joint. Fractures that are this distal may have a high incidence of nonunion, meaning that the bone does not always heal properly to produce a solid, bony structure. Still, most nonunions are asymptomatic, and of these only a small number will be problematic enough to require surgery.
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Group III: the clavicle is fractured medially (close to the sternum). This is the least common location for a clavicle fracture, and accounts for only about 5% of all clavicular fractures
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