The young patient fell on an outstretched arm while playing football.
The “S” shape and normal overlap with the upper ribcage renders the clavicle a difficult structure to evaluate on straight anteroposterior projections. The optimum view is anteroposterior projections with 15 degrees cephalad tube angulation. Weights (10-15 pounds) may be held to aid in detecting undisplaced fractures. The exposure factors should be approximately half of that utilized in standard shoulder projections, to prevent overexposure.
Generally, a clavicle fracture follows direct trauma and is the most common bone fractured during birth and in childhood.
Medial Clavicle Fractures
This is the least common site, representing only approximately 5% of all clavicle fractures.1 These are difficult to observe and usually require CT scans.
Middle Clavicle Fractures
This is the most common site, representing approximately 80% of all clavicle fractures.1 A force applied to the distal end of the “S” shaped clavicle creates a shearing effect at the middle third, producing the fracture. The fracture is usually complete, with the medial fragment elevated by the action of the sternocleidomastoid muscle, and the lateral fragment depressed by the weight of the shoulder and upper extremity. In addition to misalignment, an overlap at the fracture site is common, with the distal fragment usually lying below the medial fragment. Healing is often associated with extensive callus formation.
Lateral Clavicle Fractures
These account for approximately 15% of all clavicle fractures.1 There are three varieties:
2) displaced, where the distal fragment moves anterior and inferior; and
3) articular surface extension.
Whenever a fracture of the lateral third is identified, weight bearing stress views should be obtained to clarify the status of the coracoclavicular ligaments.2 Notably, fractures that extend into the joint frequently precipitate the onset of degenerative arthritis.
Complications of Clavicle Injuries
Childhood clavicular fractures usually heal without sequelae; however, in adults, the incidence of complications increases.
Associated injury to the underlying neurovascular structures most frequently involves the subclavian artery, less commonly the vein and, occasionally, the brachial plexus and sympathetic chain.3 Compressive effects from the hypertrophic callus can also precipitate pressure-related neurovascular disturbances.1,4
A failure to unite the fracture requires surgical fixation. The key signs of nonunion are located at the fracture margins, where sclerosis, rounding, and a smooth contour will be visible.
In the presence of fragment overlap and massive callus formation, a cosmetic deformity may result. Correction requires osteotomy, realignment and fixation.
Painful degenerative arthritis frequently follows intra-articular fractures of the clavicle. This is evidenced by loss of joint space, sclerosis and osteophyte formation.
A peculiar bone response to clavicular injury is resorption of the distal segment, usually 1-3 mm, but never more than 2-3 cm. The initiating injury may be relatively minor, often lacking the severity of that required to cause a fracture or dislocation. It first becomes radiologically visible 2-3 months after injury. The precise mechanism is uncertain, although synovial hypertrophy suggests inflammatory osteoclastic activity.5 Pain is mild to moderate, while the disorder takes a self-limiting course over a number of months.
The earliest radiographic sign in the development of osteolysis is a cystic rarefaction of the clavicular subarticular cortex, followed by cortical dissolution.5,6 The joint appears wide and the clavicular surface is frayed and irregular or cup-shaped. With healing, there are varying degrees of bony reconstitution to complete restoration of structure to a permanently tapered distal clavicle and increased joint space.
Dr. Terry R. Yochum is a second-generation chiropractor and a cum laude graduate of the National College of Chiropractic, where he subsequently completed his radiology specialty. He is currently Director of the Rocky Mountain Chiropractic Radiological Center, in Denver, CO, an Adjunct Professor of Radiology at the Los Angeles College of Chiropractic, as well as an instructor of Skeletal Radiology at the University of Colorado School of Medicine, Denver, CO. Dr. Yochum is, also, a consultant to Health Care Manufacturing Company that offers a Stored Energy system. For more information, Dr. Yochum can be reached at: 303-940-9400 or by e-mail at [email protected].
Dr. Chad Maola is a 1999 Magna Cum Laude graduate of National College of Chiropractic.
1. Pavlov H, Freiberger RH: Roentgenology of Fractures and Dislocations, Shoulder. Edited by B. Felson, New York, Grune & Stratton, 1978.
2. Heppenstall RB: Fractures and dislocations of the distal clavicle. Orthop Clin North Am 6:477, 1975.
3. Yates OW: Complications of fractures of the clavicle. Injury 7:189, 1975.
4. Rockwood CA, Green DP: Fractures, Philadelphia, JB Lippincott, 1975.
5. Levine, HL, Pais MJ, Schwartz EE: Post-traumatic osteolysis of the distal clavicle, with emphasis on early radiologic changes. AJR 127:781, 1976.
6. Yochum TR, Rowe LJ: Essentials of Skeletal Radiology, ed 3. Baltimore, Lippincott Williams & Wilkins, Baltimore, 2005.