A protrusion and an extrusion are both disc herniations. The difference is shape: in a protrusion the base of the displaced disc material is wider than the part that sticks out, and in an extrusion the part that sticks out is wider than its base or extends above or below the disc. That shape difference tracks with a difference in how strongly each finding is linked to pain. After a car accident, patients in Charlotte often see one of these words on an MRI report without knowing which carries more weight.
The Definitions
The 2014 consensus nomenclature defines a herniation as a focal displacement of disc material involving less than 25% of the disc circumference (Fardon, Spine J 2014). In a protrusion, the base of the displaced material is wider than any distance the material extends. In an extrusion, the displaced material is wider than its base in at least one plane, or it extends above or below the level of the disc. Sequestration means a fragment has separated from the disc.
The radiology committee behind the nomenclature wrote that these definitions do not imply trauma, a relationship to symptoms, or a need for treatment (Williams, AJNR 2014). They describe shape.
How Common Each Is Without Pain
In a systematic review of 3,110 people with no back pain, disc protrusion was present in 29% at age 20 and 43% at age 80 (Brinjikji, AJNR 2015). Protrusions are common enough in pain-free adults that one on a post-crash MRI is not, by itself, evidence of injury.
How Strongly Each Is Linked to Pain
A meta-analysis by the same group compared 1,193 asymptomatic adults with 1,904 adults with low back pain, all aged 50 or younger (Brinjikji, AJNR 2015 meta-analysis). Both findings were significantly more common in people with pain. Disc extrusion had an odds ratio of 4.38. Disc protrusion had an odds ratio of 2.65. Put plainly, an extrusion was more strongly associated with having back pain than a protrusion was.
The study has limits that matter. It covered the lumbar spine only, adults 50 or younger only, and it measured association with pain, not cause. It does not say an extrusion on a given patient's MRI came from a given collision.
What Moves an Individual Case
For either finding, three things connect it to a crash: prior imaging of the same level showing it was not there before, symptoms that began after the collision, and a neurologic exam that matches the level. An extrusion at L5-S1 with new leg symptoms in the S1 distribution and a normal MRI from two years earlier is a different case from the same extrusion with no prior imaging and back pain only.
I read the word on the report as the starting point. The exam and the history decide what it means.
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 the difference between a disc protrusion and an extrusion?
In a protrusion, the base of the displaced disc material is wider than the part that extends out. In an extrusion, the displaced material is wider than its base in at least one plane, or extends above or below the disc (Fardon, Spine J 2014).
Is a disc extrusion worse than a protrusion?
An extrusion was more strongly associated with low back pain than a protrusion in adults 50 or younger, with odds ratios of 4.38 versus 2.65 (Brinjikji, AJNR 2015 meta-analysis). Association with pain is not the same as severity in an individual.
Are disc protrusions common in people without pain?
Yes. A systematic review found disc protrusion in 29% of pain-free 20-year-olds and 43% of pain-free 80-year-olds (Brinjikji, AJNR 2015).
Does a disc extrusion on MRI prove a car accident caused it?
No. The standard definitions do not imply trauma. Prior imaging, symptom timing, and a matching neurologic exam connect a finding to a collision.
What does Dr. Justin Dick look for when an MRI shows a disc herniation?
Dr. Justin Dick in Charlotte, NC checks whether the level matches the patient's symptoms and neurologic exam, when the symptoms began, and whether prior imaging of that level exists.
Where can I get an MRI disc finding reviewed 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
- Fardon DF, Williams AL, Dohring EJ, Murtagh FR, Gabriel Rothman SL, Sze GK. Lumbar disc nomenclature: version 2.0. Spine J. 2014;14(11):2525-2545. PMID 24768732. LinkEvidence tier: Expert consensus (NASS, ASSR, ASNR task forces)
- Williams AL, Murtagh FR, Rothman SLG, Sze GK. Lumbar disc nomenclature: version 2.0. AJNR Am J Neuroradiol. 2014;35(11):2029. LinkEvidence tier: Editorial by the ASSR/ASNR nomenclature committee (expert consensus)
- Brinjikji W, Luetmer PH, Comstock B, et al. Systematic literature review of imaging features of spinal degeneration in asymptomatic populations. AJNR Am J Neuroradiol. 2015;36(4):811-816. PMID 25430861. LinkEvidence tier: Systematic review
- Brinjikji W, Diehn FE, Jarvik JG, et al. MRI findings of disc degeneration are more prevalent in adults with low back pain than in asymptomatic controls: a systematic review and meta-analysis. AJNR Am J Neuroradiol. 2015;36(12):2394-2399. PMID 26359154. LinkEvidence tier: Systematic review and meta-analysis
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
Book online
Justin Dick
Contact Me
