By: Terry R. Yochum, DC, DACBR, Fellow, ACCR, Michael S. Barry, DC, DACBR, and Chad J. Maola, DC
While playing football, this young adult male patient suffered shoulder trauma and complains of pain. Is there any abnormality on these images?
Traumatic dislocation of the acromioclavicular joint, Type III.
Acromioclavicular Joint Separations
The traumatic dislocation of this patient’s acromioclavicular joint is only demonstrated on the weightbearing views of the acromioclavicular joint. The normal measurement between the coracoid process and the inferior surface of the clavicle is within the range of 11–13 mm. As a result of tearing of the acromioclavicular ligament and undoubtedly the coracoclavicular ligament in this case, there is a significant increase in this measurement.
The optimal radiographic views are anteroposterior projections with 15° of cephalic tilt and with and without 10–15 pounds of weight. These should be done bilaterally, for comparison purposes. An AP view with internal rotation performed without weights may show grade III tears due to scapular motion.
Three landmarks are assessed on weightbearing and non-weightbearing views to evaluate displacement at the acromioclavicular joint.
- Acromioclavicular joint space. Normally, the space is bilaterally symmetrical, within 2-3 mm of each other, and averages between 2–4 mm in absolute width.
- Acromioclavicular joint alignment. The inferior and superior margins of the clavicle and opposing acromion should be in smooth horizontal alignment.
- Coracoclavicular distance. The distance between the inferior margin of the clavicle and the closest surface of the coracoid is normally 11–13 mm. There should be no more than 5 mm difference in the measurement from right to left.
Classification of Acromioclavicular Injuries
This is usually based on the degree of injury to the acromioclavicular and coracoclavicular ligaments.
Type I (Mild Sprain). The acromioclavicular ligament is stretched but not disrupted, and the coracoclavicular ligament is intact. Even on weightbearing views, no discernable increase in the joint space or altered alignment is visible. These are treated conservatively.
Type II (Moderate Sprain). The acromioclavicular ligament is torn, and the coracoclavicular ligaments are stretched but intact. Radiographically, the joint space is widened and slight elevation of the clavicle has occurred. These are initially treated conservatively, with a brace, but may require surgery. Old injuries to the coracoclavicular ligament may manifest as ligamentous ossifications.
Type III (Severe Sprain). Both the acromioclavicular and coracoclavicular ligaments are completely disrupted. Radiographic signs include widened joint space, distinctive elevation of the distal clavicle above the acromion, and a coracoclavicular space that is widened more than 5 mm from the contralateral counterpart. The separation can be shown on an AP non-weightbearing view with internal rotation. These may require joint repair and open fixation.
- Yochum TR, Rowe LJ. Essentials of Skeletal Radiology, 2nd ed. Baltimore, MD: Williams & Wilkins, 1996.
- Vanarthos WJ, Ekman EF, Bohrer SP. Radiographic diagnosis of acromioclavicular joint separation without weight bearing: importance of internal rotation of the arm. AJR 1994; 162:120.
- Allman FL Jr. Fractures and ligamentous injuries of the clavicle and its articulations. J Bone Joint Surg (Am) 1963; 49:774.
- Prolass JJ, Stampfi FW, Osmer JC. Coracoid process fracture diagnosis in acromioclavicular separation. Radiology 1975; 116:61.
About the Authors
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 a Diplomate of the American Chiropractic Board of Radiology and served as its vice-president and president for seven years (1983-1990).
Dr. Michael S. Barry is a 1988 cum laude graduate of Palmer College of Chiropractic. He completed a three-year radiology residency at Logan College of Chiropractic following two years of clinical practice in Las Vegas, Nevada. He received his diplomate in radiology from the American Chiropractic Board of Radiology in 1992.
Dr. Chad J. Maola is a 1999 magna cum laude graduate of National College of Chiropractic.