Walking Away Does Not Mean Walking Away Uninjured
After a car accident, most patients are discharged from the emergency room with normal X-rays, CT scans, or MRIs showing no fractures. They are informed they are fine and sent home. However, pain may worsen in the days or weeks that follow.
For many accident survivors, the problem lies not in the bones themselves but in the supporting structures that hold them together.
The Spine Is Held Together by More Than Bone
Understanding spinal stability helps explain why some injuries are overlooked.
The spine consists of 24 vertebrae stacked on top of one another. Each vertebra is connected to the next through a system of discs, ligaments, and muscles. These structures work together to allow movement while preventing any single vertebra from moving too far out of place.
The sudden force of a car accident, even at low speeds, can damage these supporting structures. Ligaments may stretch or tear, and muscles can be strained or detached. This can cause one vertebra to move more than the adjacent vertebrae.
This condition is known as spinal instability and is among the most commonly missed diagnoses after a car accident.
Why Standard Imaging Can Miss It
Standard X-rays, CT scans, and MRIs are performed with the patient lying still. These static images capture the spine at rest.
Instability may not be visible when the spine is immobile. A study published in PubMed Central found that MRI missed 37.7% of spinal instability cases later identified on flexion-extension radiographs. This means more than one in three cases were not detected by MRI alone.
A 2025 review published in PubMed Central reported that MRI sensitivity for detecting ligamentous injury is estimated at no more than 75%, often leading to missed diagnoses, especially when subtle ligament damage is present without significant structural changes on the scan.
What a Flexion-Extension X-Ray Actually Does
A flexion-extension X-ray, also known as dynamic radiography, differs from other spinal imaging because it captures the spine in motion.
Unlike routine static radiographs, which show the spine in a fixed position, dynamic flexion-extension views are designed to detect subtle instability that appears only during movement.
The procedure is straightforward. For the neck, the patient looks down as far as possible, then up. For the lower back, the patient bends forward and then backward. X-ray images are taken in both positions, and the physician compares vertebral movement between positions.
If one vertebra shifts more than the accepted normal threshold relative to those around it, greater than 2.5 mm of anterior or posterior displacement, or more than 11 degrees of angular difference, it indicates that the structures meant to hold it in place have been compromised.
This finding cannot be captured in a static image and only becomes visible during spinal movement.
What This Looks Like After a Car Accident
Peer-reviewed literature documents the relationship between car accidents and missed spinal instability.
Research published in NCBI/PMC found that the incidence of delayed or missed diagnosis of cervical spine injury following trauma ranges from 4.9% to 20%. Incomplete radiological studies and misinterpretation remain among the most common causes.
A study published in the journal Neurospine documented four patients who were diagnosed with cervical instability days to weeks following car accidents. All four had persistent neck pain with no neurological deterioration and no abnormalities on standard static radiographic studies. Only after dynamic flexion-extension radiographs were performed was the instability identified.
In one documented case, a patient was evaluated at another facility with a CT scan, an MRI, and standard X-rays, and was diagnosed with cervical sprain. No fracture was visible. Seven weeks later, a follow-up CT scan combined with dynamic flexion-extension radiographs revealed subluxation and abnormal vertebral slippage at the C5-C6 level.
The instability was present from the outset, but standard imaging was not designed to detect it.
Symptoms That May Indicate Further Evaluation Is Needed
Spinal instability after a car accident may not present with obvious symptoms. Several patterns are particularly relevant for accident survivors:
Why Early Evaluation Matters
Undiagnosed spinal instability can lead to more than discomfort. If left untreated, abnormal vertebral movement may progressively damage surrounding discs, joints, and nerves, turning a recoverable injury into a chronic condition.
Per research published in NCBI/PMC, dynamic flexion-extension radiography is often recommended for patients presenting with neck pain or tenderness following an acceleration-deceleration injury, particularly when initial static imaging yields no clear findings and symptoms persist.
Early and comprehensive evaluation, including appropriate imaging for the specific injury, provides the best opportunity for full recovery.
How AP Healthcare Supports Access to the Right Care
Navigating the diagnostic process after a car accident can be complex. Understanding which imaging is appropriate and connecting with experienced providers can significantly speed diagnosis and treatment.
AP Healthcare connects injured individuals with experienced providers who understand the full range of post-accident injuries, including those requiring specialized diagnostic evaluation. We assist with scheduling, transportation, and care coordination from the first appointment onward.
To learn more, visit aphealthcare.org or call (404) 850-9600.
Sources:
Kim, H.J. et al. (2015). Delayed or Missed Diagnosis of Cervical Instability after Traumatic Injury: Usefulness of Dynamic Flexion and Extension Radiographs. Neurospine (formerly Journal of Korean Neurosurgical Society). PMC4623170.
Braca, J.A. et al. (2022). The Utility of Flexion-Extension Radiographs in Degenerative Cervical Spondylolisthesis. PMC9311460.
Documenting Cervical Spine Injuries Following Negative MRI Findings: Clinical and Medico-Legal Overview of Dynamic Imaging. PMC12273891.
Hartman, J. (2019). Radiologic Evaluation of Lumbar Spinal Stenosis. Cureus. PMC6529051.
Bone and Spine. (2025). Flexion-Extension X-Rays of Cervical Spine. boneandspine.com.