Cervical Pedicle Subtraction Osteotomy

Andrew H. Milby

John M. Rhee

Illustrative Case

A 68-year-old female with a history of prior anterior cervical diskectomy and fusion at another institution for myelopathy because of ossification of the posterior longitudinal ligament (OPLL). After inadequate anterior decompression, the outside treating surgeon performed a subsequent posterior decompression and fusion. However, the patient continued to develop worsening myelopathy, along with progressive kyphosis and difficulty with horizontal gaze, having to hold her chin up with her hand. She also complained of radiating left arm pain in a T1 distribution (Figures 9-1, 9-2, 9-3).

Figure 9-1 ▪ Preoperative standing 36 in lateral x-ray demonstrating sequelae of prior C3-4 anterior cervical diskectomy and fusion and C3-6 laminectomy/posterior spinal fusion with persistent upper thoracic and cervical kyphosis, near chin-on-chest deformity, and compensatory hyperextension at the craniocervical junction.

Figure 9-2 ▪ A, B, Sagittal and axial T2-weighted MR images demonstrating persistent ossification of the posterior longitudinal ligament at C3-4 with ventral deformation of the spinal cord, mild-moderate cord compression at C6-7 and T1-2, as well as bilateral neuroforaminal stenosis at T1-2 with spondylolisthesis.

Figure 9-3 ▪ Sagittal CT images demonstrating severe right-sided C1-2 arthrosis, C3-6 posterior instrumentation with solid fusion, probable autofusion C6-7 retained anterior cervical implant at C3-4 with persistent retrovertebral ossification of the posterior longitudinal ligament, severe disk degeneration, and anterolisthesis at T1-2.

Radiologic Assessment

Preoperative CT angiogram recommended
- Carefully assess vertebral arteries for any anatomic variation and determine safe zone for exposure and instrumentation.
- When performing a cervical osteotomy, C7 is preferred due to the absence of vertebral artery in most cases. However, a small percentage of patients will have a vertebral artery in the foramen transversarium at C7, which can be verified on CT, MRI, or CT angiography. Other options for osteotomy include T1 or T2.
Examine T1 slope, cervical lordosis, chin-brow to vertical angle to determine extent of correction needed and landmarks for osteotomy.

Positioning

Refer to the chapter on cervical laminectomy, instrumentation,and fusion.
Ensure that monitors/lines are free around Mayfield to allow for intraoperative adjustment.
If harvesting iliac crest, ensure harvest site is exposed for prep/drape.

Anesthesia/Neuromonitoring Concerns

Mean arterial pressure goal greater than 80 mm Hg in the setting of myelopathy
Total intravenous anesthesia in the setting of motor evoked potential monitoring

Localization of incision and Approach