Magnetic resonance imaging of the coracoclavicular ligaments: its role in defining pathoanatomy at the acromioclavicular joint.

Four patients with acromioclavicular joint injuries (one type II, two type III, one type V), two patients without acromioclavicular joint injury, and a fresh-frozen cadaver underwent magnetic resonance imaging (MRI) and plain radiographs. The normal conoid and trapezoid ligaments were easily identified in the cadaver and the two uninjured patients. Magnetic resonance imaging revealed disruption of both coraclavicular ligaments in the three patients with type II and type III injuries. However, the patient with the type V injury had disruption of the trapezoid ligament alone. Thus, the grade of injury, as determined by the change in the coracoclavicular interval onplain radiography and defined by the Rockwood classification system, failed to correlate with the pathoanatomy seen on MRI in two of the four injured patients. These findings suggest that improvements in the classification of these injuries may be necessary.