Normal Coracoclavicular Distance Size on Radiography
The coracoclavicular (CC) distance is the vertical interval between the superior margin of the coracoid process and the inferior surface of the clavicle, maintained by the conoid and trapezoid ligaments. Accurate measurement of this distance on anteroposterior (AP) shoulder radiographs is essential for detecting acromioclavicular (AC) joint injuries and assessing ligamentous disruption. Even subtle increases in this measurement can indicate clinically significant instability requiring surgical or conservative management.
Normal Reference Values
| Orientation | Location | Measurement |
|---|---|---|
| Anteroposterior | Distance | 11-13 mm |
| Anteroposterior | Right And Left Shoulder Difference | <5 mm |
Clinical Significance
A normal CC distance ranges from 11–13 mm on AP radiography, with a bilateral difference of less than 5 mm considered within normal limits. Asymmetry exceeding 5 mm between shoulders strongly suggests disruption of the coracoclavicular ligaments and warrants careful clinical correlation. Stress views with weights can accentuate displacement when standard radiographs are equivocal.
The Rockwood classification of AC joint injuries relies heavily on CC distance measurements. In Type III injuries, the CC distance increases by 25–100% compared to the contralateral side; Types IV–VI demonstrate even greater or atypical displacement. Pitfalls include patient positioning (rotation or tilt), beam angulation, and obesity, all of which can artificially alter the measured interval.
- Acromioclavicular joint sprain (Rockwood I–II): CC distance within normal limits or minimally increased
- Complete AC dislocation (Rockwood III–VI): CC distance markedly increased, often >5 mm asymmetry
- Distal clavicle fracture (Neer Type II): CC ligament disruption with superior clavicle displacement
- Os coracoideum or coracoid fracture: May alter baseline CC measurement
- Physiological asymmetry: Dominant-arm hypertrophy can cause borderline differences; always correlate clinically
Reference: Marincek B, Dondelinger RF. Emergency Radiology, Imaging and Intervention. Springer. (2007).
Imaging Notes
CC distance is measured on a true AP radiograph of the shoulder with the patient upright and arms at the sides. The measurement is taken as the perpendicular vertical distance from the superior cortex of the coracoid process to the inferior cortex of the clavicle. Bilateral comparison views should be obtained with identical technique and positioning to ensure a valid side-to-side comparison; a dedicated AP projection without tube angulation minimizes parallax error.
Weighted stress views (5–10 lb in each hand) are recommended when standard radiographs are inconclusive, as they may unmask occult ligamentous laxity not apparent at rest. CT is occasionally used for complex cases but is not routinely required for CC distance assessment.