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Atlas Frx / Jefferson Fracture


- See: Anatomy of C1 / C2

- Discussion:
    - classically described as a 4 part burst frx of the atlas, w/ combined anterior and posterior arch fractures;
    - frx variants: include two and three part fractures;
    - pediatric frx:
          - frx proceeds thru open synchondroses, and may occur w/ minimal trauma;
          - posterior synchondroses fuses at age 4;
          - anterior synchondroses fuses at age 7;
    - mechanism:
          - original description in 1920 noted role of axial compression;
          - may also be caused by hyperextension, causing a posterior arch fracture;
    - associated injuries:
          - approx 1/3 of these fractures are associated with a axis fracture;
          - approx 50% chance that some other C-spine injury is present;
          - low rate of neurologic deficits is due to large breadth of C1 canal;

- Exam:
    - pts usually complain of upper neck pain;
    - pts are usually neurologically intact;
    - in cases of vertebral artery injury, neurologic injury can occur;
         - neurologic injury may manifiest as Wallenberg's syndrome w/ ipsilateral loss of cranial nerves,Horner's syndrome, ataxia, and 
                loss of contra-lateral pain and temp. sensation;

- Radiographs:

    - Odontoid view:
         - open mouth odontoid view shows overlapping of C1 facets on C2 facets;
         - if sum of lateral mass displacement over articularsurfaces of axis is > 7 mm, transverse ligamentis likely 
                 to be torn;
                - this fracture is therefore considered unstable & should be rx'ed in halo for 3 months;
         - children:
                - overlapping lateral masses can be a normal variant in children and therefore this view may not allow assessment of whether frx is 
                       stable or unstable;

    - Lateral view:
         - shows prevertebral soft tissue widening
         - if atlantodental interval is > 4 mm, there may be a rupture of the transverse ligament;
         - if antantal dens interval is > 6 mm, transverse ligament is presummed to be disrupted and the injury is unstable;
         - fusion anomalies of theAtlas differ from a burst frx in that fusion defect has well corticated margins and is associated w/ no soft 
                tissue swelling;

    - Flexion and Extension Views:
         - usually required to determine whether there is transverse ligament disruption;
         - atlantodens interval > 3 mm indicates hypermobility;
         - may detect concomitant anterior hypermobility;

    - CT Scan:
         - probably should be ordered for all children suspected of having Jefferson frx, since the odontoid view may be difficult to interpret;
         - additional information may be provided by a CT scan, which may detect ligament avulsion frx, even if displacement is < 7 mm;
         - CT of C1 is often helpful in further delineating exact displacement of fragments;

- Treatment of Stable Frx:
    - by definition stable fractures are those w/ intact transverse ligament;
    - nondisplaced or minimally displaced frx is rx'ed w/ orthosis;
            - soft-collar treatment is sufficient for isolated posterior arch frx;
    - w/ minimally displaced fracture (and overhang is < 7 mm), then frx is stable and should be treated in a rigid support, such as a 
            cervicothoracic brace, for 3 month;
    - although late subluxation of C-1 is not common, it should be looked for following bony healing;

- Treatment of Unstable Frx:
    - separation of lateral masses implies that transverse ligament is ruptured, and is therefore unstable;
    - prolonged cranial traction is only method that will reduce lateral mass displacement, because halovest will not dependably produce 
          sustained traction;
          - w/ adequate reduction following traction, halovest can be worn although late atlantoaxial instability may occur;
          - halo or skeletal traction is necessary for a total of 3 months;
    - w/ greater than 5 mm of C1-C2 subluxation consider C1-C3 fusion


Fractures of the atlas

Non-union of fractures of the atlas

Injuries of the atlas and axis. A follow-up study of 85 axis and 10 atlas fractures.

Jefferson fracture in a 2-year-old child.