Minimally Invasive C1-2 Fusion




Indications




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    Approximately 50% of the normal rotation of the cervical spine occurs at the atlantoaxial motion segment. Factors that lead to instability at the atlantoaxial junction include traumatic injury to the axis or atlas and traumatic ligamentous injury. Other pathologic processes that lead to instability at C1-2 include inflammatory conditions such as rheumatoid arthritis, congenital lesions, malignancy, and severe osteoarthritis. Because of the high degree of motion at this level, rigid internal fixation provides the most stable construct to facilitate bony fusion.





Contraindications




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    Absolute contraindications for surgery are related to the medical condition of the patient. The patient must be stabilized after a traumatic injury, and any coagulopathy must be corrected before proceeding with surgery.


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    Preoperative imaging (computed tomography [CT] angiography) with careful attention to the bony and vascular anatomy must be reviewed. Large, tortuous, medially directed vertebral artery anatomy may preclude placement of C2 pars screws on one or both sides.





Planning and positioning




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    After a detailed history and physical examination are completed, imaging is reviewed. Plain x-rays of the cervical spine are reviewed to evaluate for fractures or malalignment of the cervical spine.


  • •

    CT angiography of the cervical spine adds further detailed information regarding the bony integrity of C1 and C2 and vascular anatomy.


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    For detailed soft tissue anatomy, magnetic resonance imaging (MRI) or magnetic resonance angiography is essential to visualize any compressive elements against the spinal cord. Analysis of MRI can also help delineate the severity of the ligamentous injury.


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    Intraoperative monitoring with somatosensory evoked potentials and motor evoked potentials is often used in surgery of the upper cervical spine to identify any reversible injury to the spinal cord.




    Figure 80-1:


    The patient is placed in a Mayfield head holder while supine and is carefully rotated into the prone position on two chest rolls. Care is taken to allow for sufficient space between the patient’s chin and the operative table. All dependent pressure points are carefully padded. The shoulders can be retracted with tape as needed to visualize anatomy better on fluoroscopy if necessary. Lateral fluoroscopy is used to evaluate alignment of the C1-2 motion segment and to evaluate the need for any reduction. A metal indicator is placed lateral to the cervical spine to identify the correct level and angle of approach. The midline cervical spine is palpated at C2 and C7 and marked. The incision is 2.5 cm lateral to the midline and 3 cm in length.


  • •

    Preoperative antibiotics are administered before the incision, and stockings with compressive boots are placed for deep vein thrombosis prophylaxis. The patient is prepared from occiput to T1 and draped in a sterile fashion.





Procedure





Figure 80-2:


After subcutaneous injection of the skin with local anesthetic and epinephrine, an incision is made. Bipolar cautery is used to achieve hemostasis, and monopolar cautery is used to carry the incision down to the level of the fascia. The fascia is incised with a monopolar cautery under direct vision the length of the incision. The smallest dilator is used to spread the paraspinal musculature gently. The dilator is manipulated so that it is always perpendicular to the incision and not angled medially in any way. The dilator is advanced until it rests on the lateral mass of C2.

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Jun 15, 2019 | Posted by in NEUROSURGERY | Comments Off on Minimally Invasive C1-2 Fusion

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