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C1 Fractures

  • Author: Mark R Foster, MD, PhD, FACS; Chief Editor: Jeffrey A Goldstein, MD  more...
Updated: Mar 09, 2015


The upper cervical spine is defined by the two most cephalad cervical vertebrae, C1 (the atlas) and C2 (the axis). This region is distinct in anatomic shape and is more mobile than the lower cervical spine, the subaxial cervical spine. The occipital condyles of the head (or the globe) rest upon the lateral masses of C1 (the atlas). These articular facets allow most of the flexion and extension of the head on the neck as the occipital condyles articulate on the atlas.[1, 2, 3, 4]

The ring of C1 has no vertebral body; the vertebral body that would correspond to C1 is connected or contiguous with the vertebral body of C2 and projects up as the dens (the tooth), also known as the odontoid of C2 (the axis). Most of the lateral rotation of the neck actually occurs at the C1-2 junction; the remaining motion of the cervical spine is distributed among the subaxial spine vertebral motion segments as a fractional amount (~7%) per level and is less in total than the C1-2 lateral rotation.

This area of the upper cervical spine is extremely mobile, and its stability is dependent on ligamentous structures. In unresponsive patients or those who are unable to report symptoms or pain, a C1 fracture or an occipital cervical dislocation must be excluded by radiographic screening. Also, displacement of the C1 ring may occur if the capsule or ligaments are disrupted, even without a C1 fracture; hence, the head may be displaced on the neck, and the atlas may also rotate around the odontoid or sustain a fracture of the dens.


History of the Procedure

Jefferson originally described this type of C1 fracture in 1920.[5] The principal treatment is with a halo and vest or cast, which remains an effective current treatment for many of these fractures.



The C1 vertebra (atlas) is a closed ring. A fracture of a closed ring necessarily results in at least two areas of ring disruption. These disruptions are customarily accompanied by a spread of the C1 ring fragments as a result of the axial loading mechanism of this injury and the weight of the head.

In addition to anteroposterior and lateral views, radiographs of the upper cervical spine include the open mouth view. This view may identify spreading or widening of the lateral masses or asymmetry of the separation of the odontoid from the lateral masses, which, in an appropriately centered radiograph, may be consistent with spreading of the C1 ring or a C1 fracture. Increased overhang of the lateral masses over the C2 facet totaling more than 6.9 mm suggests a fracture with disruption of the transverse odontoid ligament that may otherwise constrain displacement.

Fractures of the ring of C1 may be associated with an odontoid fracture; thus, the combination of the two fractures should be considered. Furthermore, congenital anomalies of the arch (eg, agenesis of the posterior ring) may be present. Anterior subluxation of C1 on C2 may be present and, if so, often indicates a disruption of the transverse odontoid ligament.




Fractures of the atlas account for 25% of atlantoaxial complex bony injuries, 10% of cervical spine injuries, and 2% of all spine injuries. Injury to the cervical spine occurs infrequently in pediatric populations, and although C1 represents only 1-2% of pediatric trauma and 2-10% of all cervical injuries in this population, the associated mortality is 16%.



The Jefferson fracture most commonly occurs as the result of axial loading on the head through the occiput, leading to a burst-type fracture of C1. Diving is the most frequent cause of this fracture, when it results from striking the head on an obstacle in shallow water; hence, the national program "Feet first, first time" (North American Spine Society, 2005) provides a motto for diving in unknown waters or shallow collections of water and has been an effective deterrent.

The next most frequent cause of this fracture is being thrown up against the roof of a motor vehicle, a car or bus, or even an aircraft, and the forces are distributed to the body through the neck. The third most frequent cause of these injuries is falls onto the head, except in toddlers, who are predisposed to injury from falls because of their disproportionate head size.[1]

Less frequently, when a significant rotatory force is exerted, an atlanto-occipital junction dislocation may occur, or the force may also be dissipated through the odontoid as an associated fracture.



The ring of C1 is a structural member of the cervical spine. Because it is a ring and because fracture results in disruption of this ring, more than one location is affected.

The fragments have a propensity to shift laterally, from both the weight of the head and the muscular contraction acting through this articulation; thus, occipital condylar support for the head is lost. The absence of the rigid bony structure and the lack of interconnection or interrelation of the attached ligamentous structures meet the definition of instability, particularly as the bony protective function of C1 for the neural elements is lost.

Vertebral artery injuries have been reported as a result of C1 fractures, especially with atlanto-occipital dislocations; small excursions of displacement can be fatal. In addition, vertebral artery injuries can occur and have been reported in the absence of severe trauma as a result of cervical traction, chiropractic manipulation, overhead work, or yoga exercises. Hyperextension is customarily accompanied with rotation; when this is not limited by normal restraints, it becomes excessive, severely diminishing blood flow through the vertebral arteries.

This diminished blood flow is particularly a problem in the posterior inferior cerebellar artery and may result in Wallenberg syndrome, which is characterized by ipsilateral loss of cranial nerves V, IX, X, and XI with cerebellar ataxia.

Horner syndrome may occur and, in some cases, may involve contralateral loss of pain and temperature sensation; involvement can extend up from a lateral medullary infarct and spread to the basilar superior cerebellar or the inferior cerebral artery, leading to sudden death, quadriplegia, and the locked-in syndrome, in which quadriplegia occurs with loss of lower cranial nerves and only eye-blinking is possible.



Patients customarily present with a history of trauma and a symptom of pain in the neck. Amid the massive number of patients who qualify as having this history and symptom, a few patients have an unstable C1 injury and may present neurologically intact, but they are at grave risk for neurologic compromise if not promptly diagnosed and appropriately stabilized and treated.

Patients with a complete spinal cord injury and no neurologic function continue to have only sensation on the face and motor control of the facial muscles from the cranial nerves. A tracheostomy is essential; the patient requires respiratory assistance and a volume respirator. If the C3-5 area is intact, the phrenic nerve may often be stimulated to contract the diaphragm. If stimulation of the phrenic nerve does not contract the diaphragm, then the spinal cord is no longer functioning; the cell body is dead, and a phrenic electrical stimulator is not effective.



Recognition and identification of a Jefferson fracture is the indication for treatment. Treatment consists of spinal stabilization to protect the patient from further nerve damage, including that to the brainstem. Children may represent less unstable cases, presumably because of periosteal stability, and they are often treated with a collar. The body of C1 is not visible radiographically until age 1 year.

Even in the absence of a C1 fracture, assessment of stability must include the associated structures. An atlanto-occipital dislocation or disruption and C1-2 instability, particularly when the transverse ligament may be disrupted, poses severe risk to the brainstem and upper spinal cord. Furthermore, with a C1 fracture, associations exist with unstable injuries such as odontoid fractures and other injuries to the upper cervical spine. In addition, the odontoid fragment may migrate into the foramen magnum, endangering the brainstem and upper spinal cord.

Specific treatment should be based on analysis of the mechanism and extent of the injury. In a younger patient with limited displacement of the C1, immobilization with a collar or halo and vest may be adequate.

In more severe cases, particularly with associated injuries such as odontoid fracture, bypassing the C1 ring with an occipital-to-cervical fusion extending to C2 or lower may be necessary. Instrumentation spanning that area may stabilize the C1 ring, which otherwise cannot easily be addressed directly, because both the anterior and posterior components of the ring are disconnected by the fracture and are not amenable to instrumentation or direct repair.


Relevant Anatomy

The care of any fracture requires attention to the joint above and below. This cervical complex has often been treated as two separable articulations, C0-1 and C1-2, but the three-unit occipitoatlantoaxial complex (C0-C1-C2) articulation is much more functionally relevant.

The significance is the proximity to the brain, brainstem, and upper cervical spinal cord, but that is contrasted with the very significant motion that occurs in this area. Although patients are routinely asked to flex and extend their necks to determine range of motion, some of that motion observed is between the occiput and the atlas, and as the patient rotates laterally, at least 50% of that motion is atlantoaxial.

The stability of the injury depends on the ligaments between the bony structures. On the frontal view, the projecting occipital condyles are supported by the lateral masses (observed as wedges, narrow medially and expanding laterally), resting on the corresponding superior articular surface of the axis (C2). Consequently, the lateral masses provide inherent stability because of this bony shape and also illustrate the extent of the instability when this bony structure is disrupted, particularly when these wedges displace laterally.

The projecting condyles of the occiput are stabilized with the occipitoatlantal capsule, as well as anterior and posterior atlanto-occipital membranes. The ligamentum nuchae is a significant stabilizing structure; its specific relevance to the atlanto-occipital axial complex is controversial but should be considered. Connections from the occiput to the axis are the tectorium membrane and the alar and apical ligaments, which do not appear to be bulky enough to be independently significant restraints.

The dentate ligaments (ie, the alar ligament and the apical ligaments) attach to the dorsal lateral surface of the dens and run obliquely to the medial surfaces of the occipital condyles. In 1974, Anderson and D'Alonzo classified a type 1 odontoid fracture as an avulsion fracture of the odontoid tip caused by the apical ligament, suggesting that these ligaments impart a significant degree of stability. A modified, treatment-oriented classification of odontoid fractures has been presented to expand the Anderson-D'Alonzo classification, but further assessment is needed.[6]

The transverse ligament goes from the medial surface of one side of the atlas to the other side and essentially constrains the axis to rotate around the odontoid in a closed ring of bone and the transverse ligament. As a consequence, the atlas can displace and embarrass the brainstem and spinal cord if this ligament ruptures or if an associated fracture of the odontoid is present as a result of this specific anatomic arrangement.



No significant contraindications to treatment exist, because the lack of stabilization, which commonly is initially provided either with traction or with a halo brace, can have fatal consequences. Any contraindications are mitigated by the potential for serious and even fatal neurologic consequences without treatment, as well as by the observation that halo with vest or traction can be relatively effective in immobilizing the upper cervical spine, with low associated morbidity.

Contributor Information and Disclosures

Mark R Foster, MD, PhD, FACS President and Orthopedic Surgeon, Orthopedic Spine Specialists of Western Pennsylvania, PC

Mark R Foster, MD, PhD, FACS is a member of the following medical societies: American Academy of Orthopaedic Surgeons, Orthopaedic Research Society, Pennsylvania Orthopaedic Society, American Physical Society, American College of Surgeons, Christian Medical and Dental Associations, Eastern Orthopaedic Association, North American Spine Society

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

William O Shaffer, MD Orthopedic Spine Surgeon, Northwest Iowa Bone, Joint, and Sports Surgeons

William O Shaffer, MD is a member of the following medical societies: American Academy of Orthopaedic Surgeons, American Orthopaedic Association, Kentucky Medical Association, North American Spine Society, Kentucky Orthopaedic Society, International Society for the Study of the Lumbar Spine, Southern Medical Association, Southern Orthopaedic Association

Disclosure: Received royalty from DePuySpine 1997-2007 (not presently) for consulting; Received grant/research funds from DePuySpine 2002-2007 (closed) for sacropelvic instrumentation biomechanical study; Received grant/research funds from DePuyBiologics 2005-2008 (closed) for healos study just closed; Received consulting fee from DePuySpine 2009 for design of offset modification of expedium.

Chief Editor

Jeffrey A Goldstein, MD Clinical Professor of Orthopedic Surgery, New York University School of Medicine; Director of Spine Service, Director of Spine Fellowship, Department of Orthopedic Surgery, NYU Hospital for Joint Diseases, NYU Langone Medical Center

Jeffrey A Goldstein, MD is a member of the following medical societies: American Academy of Orthopaedic Surgeons, American College of Surgeons, American Orthopaedic Association, North American Spine Society, Scoliosis Research Society, Cervical Spine Research Society, International Society for the Study of the Lumbar Spine, AOSpine, Society of Lateral Access Surgery, International Society for the Advancement of Spine Surgery, Lumbar Spine Research Society

Disclosure: Received consulting fee from Medtronic for consulting; Received consulting fee from NuVasive for consulting; Received royalty from Nuvasive for consulting; Received consulting fee from K2M for consulting; Received ownership interest from NuVasive for none.

Additional Contributors

James F Kellam, MD, FRCSC, FACS, FRCS(Ire) Professor, Department of Orthopedic Surgery, University of Texas Medical School at Houston

James F Kellam, MD, FRCSC, FACS, FRCS(Ire) is a member of the following medical societies: American Academy of Orthopaedic Surgeons, Orthopaedic Trauma Association, Royal College of Physicians and Surgeons of Canada

Disclosure: Nothing to disclose.

  1. North American Spine Society. Spinal cord injury. Available at: Accessed: November 13, 2006.

  2. White AA, Panjabi MM. Clinical Biomechanics of the Spine. 2nd ed. Philadelphia: Lippincott Williams & Wilkins; 1990.

  3. Aebi M. Surgical treatment of upper, middle and lower cervical injuries and non-unions by anterior procedures. Eur Spine J. 2009 Oct 14. [Medline].

  4. Elgafy H, Dvorak MF, Vaccaro AR, Ebraheim N. Treatment of displaced type II odontoid fractures in elderly patients. Am J Orthop. 2009 Aug. 38(8):410-6. [Medline].

  5. Jefferson G. Fracture of atlas vertebra. Report of four cases and a review of those previously recorded. Br J Surg. 1920. 7:407-22.

  6. Grauer JN, Shafi B, Hilibrand AS, et al. Proposal of a modified, treatment-oriented classification of odontoid fractures. Spine J. 2005 Mar-Apr. 5(2):123-9. [Medline].

  7. Sugrue PA, Hage ZA, Surdell DL, Foroohar M, Liu J, Bendok BR. Basilar artery occlusion following C1 lateral mass fracture managed by mechanical and pharmacological thrombolysis. Neurocrit Care. Oct/2008. 11:255-260.

  8. Li L, Teng H, Pan J, Qian L, Zeng C, Sun G, et al. Direct posterior c1 lateral mass screws compression reduction and osteosynthesis in the treatment of unstable jefferson fractures. Spine. Jul/2011. 36:E1046-51.

  9. De Iure F, Donthineni R, Boriani S. Outcomes of C1 and C2 posterior screw fixation for upper cervical spine fusion. Eur Spine J. Jun / 2009. 18 suppl:2-6.

  10. Costa F, Ortolina A, Attuati L, Cardia A, Tomei M, Riva M, et al. Management of C1-2 traumatic fractures using an intraoperative 3D imaging-based navigation system. J Neurosurg Spine. 2015 Feb. 22(2):128-33. [Medline].

  11. Singh PK, Garg K, Sawarkar D, Agarwal D, Satyarthee GD, Gupta D, et al. Computed tomography-guided C2 pedicle screw placement for treatment of unstable hangman fractures. Spine (Phila Pa 1976). 2014 Aug 15. 39(18):E1058-65. [Medline].

  12. Platzer P, Thalhammer G, Krumboeck A, Schuster R, Kutscha-Lissberg F, Zehetgruber I, et al. Plate fixation of odontoid fractures without C1-C2 arthrodesis: practice of a novel surgical technique for stabilization of odontoid fractures, including the opportunity to extend the fixation to C3. Neurosurgery. 2009 Apr. 64(4):726-33; discussion 733. [Medline].

  13. Al Eissa S, Reed JG, Kortbeek JB, Salo PT. Airway compromise secondary to upper cervical spine injury. J Trauma. 2009 Oct. 67(4):692-6. [Medline].

  14. Gallie WE. Fractures and dislocations of the cervical spine. Am J Surg. 1939. 46(3):495-9.

  15. Brooks AL, Jenkins EB. Atlanto-axial arthrodesis by the wedge compression method. J Bone Joint Surg Am. 1978 Apr. 60(3):279-84. [Medline].

  16. Richter M, Schmidt R, Claes L, et al. Posterior atlantoaxial fixation: biomechanical in vitro comparison of six different techniques. Spine. 2002 Aug 15. 27(16):1724-32. [Medline].

  17. Cornefjord M, Henriques T, Alemany M, et al. Posterior atlanto-axial fusion with the Olerud Cervical Fixation System for odontoid fractures and C1-C2 instability in rheumatoid arthritis. Eur Spine J. 2003 Feb. 12(1):91-6. [Medline].

  18. Alker GJ, Oh YS, Leslie EV, et al. Postmortem radiology of head neck injuries in fatal traffic accidents. Radiology. 1975 Mar. 114(3):611-7. [Medline].

  19. Anderson LD, D''Alonzo RT. Fractures of the odontoid process of the axis. J Bone Joint Surg Am. 1974 Dec. 56(8):1663-74. [Medline].

  20. Bucholz RW, Burkhead WZ. The pathological anatomy of fatal atlanto-occipital dislocations. J Bone Joint Surg Am. 1979 Mar. 61(2):248-50. [Medline].

  21. Budin E, Sondheimer F. Lateral spread of the atlas without fracture. Radiology. 1966 Dec. 87(6):1095-8. [Medline].

  22. Eismont FJ, Bohlman HH. Posterior atlanto-occipital dislocation with fractures of the atlas and odontoid process. J Bone Joint Surg Am. 1978 Apr. 60(3):397-9. [Medline].

  23. Eleraky MA, Theodore N, Adams M, et al. Pediatric cervical spine injuries: report of 102 cases and review of the literature. J Neurosurg. 2000 Jan. 92(1 Suppl):12-7. [Medline].

  24. Eubanks JD, Gilmore A, Bess S, et al. Clearing the pediatric cervical spine following injury. J Am Acad Orthop Surg. 2006 Sep. 14(9):552-64. [Medline].

  25. Evarts CM. Traumatic occipito-atlantal dislocation. J Bone Joint Surg Am. 1970 Dec. 52(8):1653-60. [Medline].

  26. Gabrielsen TO, Maxwell JA. Traumatic atlanto-occipital dislocation; with case report of a patient who survived. Am J Roentgenol Radium Ther Nucl Med. 1966 Jul. 97(3):624-9. [Medline].

  27. Garber JN. Abnormalities of the atlas and axis vertebrae--congenital and traumatic. J Bone Joint Surg Am. 1964 Dec. 46:1782-91. [Medline].

  28. Hamilton MG, Myles ST. Pediatric spinal injury: review of 174 hospital admissions. J Neurosurg. 1992 Nov. 77(5):700-4. [Medline].

  29. Hinchey JJ, Bickel WH. Fracture of the atlas: review and presentation of data on eight cases. Ann Surg. 1945 Jun. 121(6):826-32. [Full Text].

  30. Johnson RM, Hart DL, Simmons EF, et al. Cervical orthoses. A study comparing their effectiveness in restricting cervical motion in normal subjects. J Bone Joint Surg Am. 1977 Apr. 59(3):332-9. [Medline].

  31. Levine AM, Edwards CC. Fractures of the atlas. J Bone Joint Surg Am. 1991 Jun. 73(5):680-91. [Medline].

  32. Levine AM, Edwards CC. Treatment of injuries in the C1-C2 complex. Orthop Clin North Am. 1986 Jan. 17(1):31-44. [Medline].

  33. Lipson SJ. Fractures of the atlas associated with fractures of the odontoid process and transverse ligament ruptures. J Bone Joint Surg Am. 1977 Oct. 59(7):940-3. [Medline].

  34. McAfee PC. Jefferson's fracture. Frymoyer JW, Weinstein JN, Ducker TB, Kostuik JP, Hadler NM, eds. Adult Spine: Principles and Practice. 2nd ed. Philadelphia: Lippincott Williams & Wilkins; 1991. 1067.

  35. No authors listed. Isolated fractures of the atlas in adults. Neurosurgery. 2002 Mar. 50(3 suppl):S120-4. [Medline].

  36. No authors listed. Management of combination fractures of the atlas and axis in adults. Neurosurgery. 2002 Mar. 50(3 suppl):S140-7. [Medline].

  37. Oda T, Panjabi MM, Crisco JJ 3rd, et al. Experimental study of atlas injuries. II. Relevance to clinical diagnosis and treatment. Spine. 1991 Oct. 16(10 suppl):S466-73. [Medline].

  38. Panjabi MM, Oda T, Crisco JJ 3rd, et al. Experimental study of atlas injuries. I. Biomechanical analysis of their mechanisms and fracture patterns. Spine. 1991 Oct. 16(10 suppl):S460-5. [Medline].

  39. Patel JC, Tepas JJ, Mollitt DL, et al. Pediatric cervical spine injuries: defining the disease. J Pediatr Surg. 2001 Feb. 36(2):373-6. [Medline].

  40. Penning L, Wilmink JT. Rotation of the cervical spine. A CT study in normal subjects. Spine. 1987 Oct. 12(8):732-8. [Medline].

  41. Pierce DS, Barr JS Jr. Fractures and dislocations at the base of the skull and upper cervical spine. In: Bailey RW, ed. The Cervical Spine. Philadelphia, Pa:. Lippincott, Williams & Wilkins. 1983: 196-206.

  42. Richards PG. Stable fractures of the atlas and axis in children. J Neurol Neurosurg Psychiatry. 1984 Aug. 47(8):781-3. [Medline].

  43. Schellhas KP, Latchaw RE, Wendling LR, et al. Vertebrobasilar injuries following cervical manipulation. JAMA. 1980 Sep 26. 244(13):1450-3. [Medline].

  44. Sherk HH, Nicholson JT. Fractures of the atlas. J Bone Joint Surg Am. 1970 Jul. 52(5):1017-24. [Medline].

  45. Sherk HH, Schut L, Lane JM. Fractures and dislocations of the cervical spine in children. Orthop Clin North Am. 1976 Jul. 7(3):593-604. [Medline].

  46. Spence KF Jr, Decker S, Sell KW. Bursting atlantal fracture associated with rupture of the transverse ligament. J Bone Joint Surg Am. 1970 Apr. 52(3):543-9. [Medline].

  47. Wetzel SG, Martin JB, Somon T, et al. Painful osteolytic metastasis of the atlas: treatment with percutaneous vertebroplasty. Spine. 2002 Nov 15. 27(22):E493-5. [Medline].

  48. White AA 3rd, Panjabi MM. The clinical biomechanics of the occipitoatlantoaxial complex. Orthop Clin North Am. 1978 Oct. 9(4):867-78. [Medline].

Fracture of C1 ring may result in lateral displacement and subsequent overhang on open mouth view in radiographs.
Computed tomography is often best for visualizing C1 ring fractures. Note anterior disruption, which must be accompanied by another break in ring.
Computed tomography sagittal views can be used to evaluate atlantodental (or atlantodens or atlas-dens) interval or to visualize C1 fractures.
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