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Figure 1: Redlund-Johnell criterion as measured in Case #4. The distance between the McGregor line and the midpoint of the caudal margin of the second cervical vertebral body is measured. A measurement of less than 34 mm in males and less than 29 mm in females indicates basilar invagination. In this case the preoperative distance was 30.5. This improved to 38 after surgery. | Figure 2: Wackenheim line as measured in case #2. A line is drawn along the superior surface of the clivus. A. Protrusion of the odontoid tip posterior to the projection of this line indicates basilar invagination. B. After posterior instrumented reduction, the dens returned anterior to Wackenheim’s line. |
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Figure 3: Pre-reduction (A) and post-reduction (B) sagittal T-2 Weighted MRI of the cervical spine of Case #5. The posterior approach allows for C1 laminectomy in addition to reduction and restoration of cervical alignment which greatly increases the space available for the cord. | FIgure 4: 77 year old female with a type 2 odontoid fracture. Image guidance using intraoperative image acquisition provides a valuable tool in modern surgical treatment of odontoid fractures. |