Since X-rays look at bones, is it possible that an X-ray can miss a grade 1 AC injury?
An injury to the AC joint that results in damage to the ligaments (including a severing) typically occurs from a fall to the shoulder.
The outer region of the patient’s shoulder gets slammed to the ground.
This can happen from a freak fall off a small stool, a judo slam to the floor, being tackled to the ground in sport or crashing to the ground via a skiing mishap or bicycle accident.
Higher impact forces such as a motor vehicle crash or fall from a height can sever even more ligaments, resulting in a grade 4 or 5 separation.
But back to the X-ray—which can easily reveal a separation (grade 2 and beyond).
“Yes, an x-ray can absolutely miss a grade 1 (or low-grade) injury,” says John-Paul H. Rue, MD, orthopedic sports medicine surgeon with Orthopedics and Joint Replacement at Mercy Medical Center in Baltimore, MD.
Dr. Rue explains, “In fact, by definition, grade 1 AC sprains would be expected to have normal X-rays.”
In a grade 1 injury, the bone is not broken; only the ligaments are injured (sprained).
“Mechanism of injury, pain at the joint, and physical exam findings are the mainstay for diagnosing low grade sprains. X-rays are important to rule out higher grade injuries, or fractures.”
If you don’t have an X-ray, and especially if you don’t have that tell-tale bump jutting out towards the outer portion of your clavicle area that strongly suggests a complete ligament tear, you could end up guessing that you have either a grade 1 AC sprain or a mild fracture of the clavicle.
Both these conditions will cause very similar symptoms, including a lot of pain at the moment of injury and plenty of pain lingering for hours afterwards.
If an X-ray comes up negative for an AC injury but shows a little fracture in the clavicle, you’ll likely be diagnosed with a subtle fracture.
Dr. Rue specializes in prevention and treatment of sports and exercise injuries. His primary focuses are knee, shoulder and elbow injuries including ACL and cartilage injuries, rotator cuff injuries and overuse tendonitis.