Jefferson Fracture¶

Definition¶

A Jefferson fracture is a burst fracture of the atlas (C1) ring, classically involving fractures of both the anterior and posterior arches. The injury results from axial loading transmitted through the occipital condyles to the lateral masses of the atlas, causing the ring to spread outward.

Mechanism of Injury¶

The mechanism is axial compression — a vertical force applied to the top of the head that is transmitted through the occipital condyles to the C1 lateral masses. Common scenarios include diving into shallow water, motor vehicle collisions (head striking the roof), and falls landing on the vertex of the head.

Because the fracture fragments spread outward (centrifugally), the spinal canal actually widens at the level of the fracture. This explains why isolated Jefferson fractures rarely cause spinal cord injury. However, if the transverse atlantal ligament (TAL) is disrupted, the injury becomes unstable and the risk of neurological compromise increases significantly.

Classification¶

The classic Jefferson fracture involves four fracture lines — two in the anterior arch and two in the posterior arch. Variants include two-part and three-part fractures. Atlas fractures are also classified by the Gehweiler system:

• Type I — Isolated posterior arch fracture
• Type II — Isolated anterior arch fracture
• Type III — Combined anterior and posterior arch fractures (classic Jefferson)
• Type IIIa — Bilateral
• Type IIIb — Unilateral lateral mass with anterior and posterior arch
• Type IV — Isolated lateral mass fracture
• Type V — Transverse ligament avulsion (with or without bony fragment)

Imaging Findings¶

Radiography¶

• Open-mouth (odontoid) view — Lateral overhang (offset) of the C1 lateral masses beyond the lateral margins of the C2 articular surfaces. The combined bilateral lateral mass overhang is measured — a total exceeding 6.9 mm (the "rule of Spence") suggests transverse ligament disruption, though this threshold has limited reliability.
• Lateral view — Prevertebral soft tissue swelling at the C1–C2 level; the anterior atlanto-dental interval (ADI) may be widened if the transverse ligament is disrupted (normal ADI ≤3 mm in adults).

CT¶

CT is the definitive modality for characterizing the fracture:

• Fracture lines through the anterior and/or posterior arches of C1
• Lateral mass displacement and degree of offset
• Associated C2 fractures (present in up to 50% of cases)
• Integrity of the bony attachment of the transverse ligament on the medial aspect of the lateral masses

MRI¶

MRI is essential for evaluating transverse ligament integrity:

• Intact transverse ligament appears as a low-signal band on axial T2 images
• Ligament rupture shows discontinuity, high T2 signal, or edema at the insertion sites
• Also evaluates for spinal cord compression and associated ligamentous injuries

Stability Assessment¶

The key question in Jefferson fractures is whether the transverse atlantal ligament is intact:

• TAL intact — Stable injury; treat conservatively with rigid cervical collar
• TAL disrupted — Unstable injury; requires halo vest or surgical fixation (C1–C2 fusion)

Associated Injuries¶

• C2 fractures (odontoid or hangman fractures) — present in up to 50% of cases
• Vertebral artery injury
• Other cervical spine fractures
• Head injury

Key Points¶

• Jefferson fracture is a burst fracture of the C1 ring caused by axial compression
• The spinal canal widens, so isolated Jefferson fractures rarely cause cord injury
• Transverse ligament integrity determines stability — MRI is essential for this assessment
• The combined lateral mass overhang on open-mouth view is a screening tool but not definitive
• C2 fractures coexist in up to 50% of cases and must be excluded
• CT is the primary modality for fracture characterization; MRI evaluates ligamentous stability

References¶

1. Kopparapu S, Mao G, Judy BF, Theodore N. Fifty years later: the "rule of Spence" is finally ready for retirement. J Neurosurg Spine. 2022;37(2):149-156. PMID: 35148514. https://pubmed.ncbi.nlm.nih.gov/35148514/
2. Dickman CA, Greene KA, Sonntag VK. Injuries involving the transverse atlantal ligament: classification and treatment guidelines based upon experience with 39 injuries. Neurosurgery. 1996;38(1):44-50. PMID: 8747950. https://pubmed.ncbi.nlm.nih.gov/8747950/
3. Woods RO, Inceoglu S, Akpolat YT, Cheng WK, Jabo B, Danisa O. C1 lateral mass displacement and transverse atlantal ligament failure in Jefferson's fracture: a biomechanical study of the "rule of Spence". Neurosurgery. 2018. PMID: 28431136. https://pubmed.ncbi.nlm.nih.gov/28431136/
4. Liu P, Zhu J, Wang Z, et al. "Rule of Spence" and Dickman's classification of transverse atlantal ligament injury revisited: discrepancy of prediction on atlantoaxial stability based on clinical outcome of nonoperative treatment for atlas fractures. Spine (Phila Pa 1976). 2019;44(5):E306-E314. PMID: 30222691. https://pubmed.ncbi.nlm.nih.gov/30222691/
5. Mead LB 2nd, Millhouse PW, Krystal J, Vaccaro AR. C1 fractures: a review of diagnoses, management options, and outcomes. Curr Rev Musculoskelet Med. 2016. PMID: 27357228; PMCID: PMC4958388. https://pmc.ncbi.nlm.nih.gov/articles/PMC4958388/
6. Fiester P, Rao D, Soule E, et al. Radiologic utility of the Gehweiler and AO spine classification systems for C1 trauma: a retrospective review from a Level I trauma center. J Craniovertebr Junction Spine. 2022;13(4):432-438. PMID: 36777912; PMCID: PMC9910133. https://pmc.ncbi.nlm.nih.gov/articles/PMC9910133/
7. Lee TT, Green BA, Petrin DR. Treatment of stable burst fracture of the atlas (Jefferson fracture) with rigid cervical collar. Spine (Phila Pa 1976). 1998. PMID: 9779528. https://pubmed.ncbi.nlm.nih.gov/9779528/

Related Articles¶

• Odontoid Fractures
• Hangman Fracture
• Atlanto-Occipital Dissociation
• Atlas (C1)