Static flexion and extension X-rays capture the spine at two end positions. Fluoroscopic motion analysis records the spine continuously as it moves and measures motion throughout the range. In one lumbar study, the continuous method detected radiographic instability at roughly twice the rate of static films. That finding has real implications and real limits, and patients and attorneys in Charlotte ask me about both.
How the Two Methods Differ
Static flexion and extension films are standard lateral X-rays taken with the patient bent forward and then backward. Translation and angulation are measured on each film. The AMA Guides to the Evaluation of Permanent Impairment apply their thresholds for loss of motion segment integrity to these films.
Fluoroscopic motion analysis uses low-dose continuous X-ray video while the patient moves, often with a device that controls the motion, and software tracks each vertebra frame by frame.
What the Comparison Study Found
A 2015 study measured lumbar motion in 509 symptomatic patients and 73 asymptomatic participants (Davis, Int J Spine Surg 2015). Coefficients of repeatability, the range within which two measurements of the same thing should agree 95% of the time, ranged from 1.99 to 3.11 depending on the method and reader. Using the study's thresholds, the fluoroscopic system detected rotational instability in 12.3% of levels versus 6.1% with static films, and translational instability in 11.9% versus 5.4%.
What That Does and Does Not Mean
If the result holds, static films underdetect instability, and a normal static study is less reassuring than it looks. It does not mean every additional level the motion system flagged was a true injury. The study measured how often each method crossed a threshold, not which method was right against a reference standard such as surgical findings or patient outcomes. Its thresholds, 15% translation and 25 degrees of rotation, also differ from the AMA lumbar values.
The study used a commercial system. I could not determine from the abstract whether any authors had a financial interest in it. It is one study, in the lumbar spine.
The Rating Problem
For impairment rating, the AMA Guides accept loss of motion segment integrity on plain-film flexion and extension views. A motion-analysis finding may be clinically useful and still not map directly onto that rating standard. Anyone relying on fluoroscopic findings in a case should know which standard the finding was measured against.
What I Use
I take static flexion and extension films and measure them against the AMA thresholds, reporting the values and the threshold applied. For context on normal cervical motion, a study of 75 normal subjects found nearly all intervertebral angular differences in flexion were under 7 degrees (Lin, Spine 2001). When a static study is normal but the clinical picture strongly suggests a segmental problem, I say in the report that static films can underdetect instability, rather than calling the spine cleared.
For an example of how post-collision imaging findings and outcomes are documented in the peer-reviewed literature, read Dr. Justin Dick's published case report on refractory lumbar pain following a motor vehicle accident in a geriatric patient.
Frequently Asked Questions
What is fluoroscopic motion analysis of the spine?
It records the spine with low-dose continuous X-ray video while the patient moves and tracks each vertebra frame by frame, measuring motion throughout the range rather than at two end positions.
Is fluoroscopic motion analysis better than flexion and extension X-rays?
In one lumbar study it detected radiographic instability at roughly twice the rate of static films (Davis, Int J Spine Surg 2015). The study did not compare either method against surgical findings or outcomes.
How accurate are spinal motion measurements?
In the same study, coefficients of repeatability ranged from 1.99 to 3.11 (Davis, Int J Spine Surg 2015). Values close to a threshold are not clear results.
Do the AMA Guides accept fluoroscopic motion findings?
The AMA Guides accept loss of motion segment integrity on plain-film flexion and extension views. A fluoroscopic finding may not map directly onto that rating standard.
What does Dr. Justin Dick report when static X-rays are normal?
Dr. Justin Dick in Charlotte, NC reports the values and threshold used, and notes when the clinical picture suggests static films may have underdetected instability.
Where can I get spinal motion X-rays after a car accident in Charlotte, NC?
Dr. Justin Dick, DC, CNMT, ARRT(N)(CT), sees car accident patients at Clear Life Scoliosis and Chiropractic Center, 8814 Rachel Freeman Way, Suite 103, Charlotte, NC 28278, phone 980-368-0766. Personal injury patients are treated on a lien basis, with no out-of-pocket payment at the time of care.
Sources and Evidence Tiers
- Davis RJ, Lee DC, Wade C, Cheng B. Measurement performance of a computer assisted vertebral motion analysis system. Int J Spine Surg. 2015;9:36. PMID 26273554. LinkEvidence tier: Retrospective diagnostic performance study
- American Medical Association. Guides to the Evaluation of Permanent Impairment, Fourth, Fifth, and Sixth Editions.Evidence tier: Expert consensus (impairment rating guideline)
- Lin RM, Tsai KH, Chu LP, Chang PQ. Characteristics of sagittal vertebral alignment in flexion determined by dynamic radiographs of the cervical spine. Spine. 2001;26(3):256-261. PMID 11224861. LinkEvidence tier: Cross-sectional normative study (75 subjects)
About the author. Dr. Justin M. Dick, DC, is the owner and treating clinician at Clear Life Scoliosis and Chiropractic Center in Charlotte, NC. He holds dual imaging credentials as a Certified Nuclear Medicine Technologist (CNMT) and as an ARRT-registered technologist in nuclear medicine and CT, ARRT(N)(CT). He is a Senior Fellow of the CLEAR Institute, holds the ISICO World Masters credential, is a SOSORT provisional member, and is a certified DOT medical examiner on the FMCSA National Registry. He has multiple peer-reviewed publications indexed in PubMed and serves as adjunct faculty at Life, Sherman, and Palmer chiropractic colleges.
Service Area
Clear Life Scoliosis and Chiropractic Center sees personal injury and spinal imaging patients from Charlotte NC, Huntersville NC, Ballantyne NC, Matthews NC, Concord NC, Mooresville NC, Rock Hill SC, and Fort Mill SC.
Related Pages
- Personal injury and car accident spinal care in Charlotte
- Dr. Justin Dick's research
- Case report: refractory lumbar pain after a motor vehicle accident
- Research and evidence at Clear Life
- Questions and answers
- Our team
- Press
- Book your evaluation
- Contact Clear Life
Clear Life Scoliosis and Chiropractic Center
8814 Rachel Freeman Way, Suite 103
Charlotte, NC 28278
Phone: 980-368-0766
Email: office@clearlifescoliosis.com
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