Technical Feasibility of Subaxial Cervical Pedicle Screws for Distal Anchoring of Occipitocervical Fixation Constructs in the Mid-Cervical Spine: Early Clinical Experience

Abstract

Occipitocervical fixation and fusion (OCF) is performed for patients who have destabilizing traumatic injuries or pathologies affecting the complex bony and ligamentous structures of the occipitoatlantal and atlantoaxial joint structures. Distal fixation failure and pseudoarthrosis are known risks of these constructs, especially for those constructs ending in the mid-cervical spine. We present the technical feasibility of using cervical pedicle screws (CPSs) as distal fixation anchors to strengthen OCF constructs ending in the mid-cervical spine and present a case series describing our early clinical experience with this technique. We used a freehand technique to place subaxial pedicle screws in the mid-cervical spine as the distal fixation point in OCF constructs. This technique involves performing a laminotomy to provide direct visualization of the pedicle borders to safely guide freehand pedicle screw placement. Our early clinical experience with this technique is presented. Three patients received OCF constructs ending in the mid-cervical subaxial spine between C3 and C6. CPSs were placed at the distal vertebra in each construct. Stable instrumentation and arthrodesis were confirmed postoperatively in all patients. This freehand technique uses direct visualization of the pedicle to aid in safe and accurate subaxial pedicle screw placement. CPS placement is clinically feasible and increases the robustness of OCF constructs in appropriately selected patients. Larger case series are needed to further validate the safety and effectiveness of this technique.

Keywords: case series; cervical pedicle screws; freehand technique; occipitocervical fusion; subaxial cervical spine.

Figure 1. Illustrations showing steps in the freehand technique with direct visualization for subaxial cervical pedicle screw placement.

This technique was used for pedicle screw fixation at the lowest instrumented level in occipitocervical fixation and fusion constructs. (A) A hemilaminotomy is performed (dashed line). Posterolateral (B) and axial (C) views showing the superior, inferior, and medial walls of the pedicle. The entry point is placed 1 to 2 mm lateral to the midpoint of the base of the superior articulating process. A dissector is used to retract the dura medially to visualize the interface of the medial pedicle wall with the posterior vertebral body to determine screw trajectory medialization (dashed line). Posterolateral (D) and axial (E) views show proper pedicle screw placement. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

Figure 2. A woman in her early 40s presented with basilar invagination causing cervicomedullary compression in the setting of rheumatoid arthritis.

(A) Preoperative sagittal MRI showed cervicomedullary compression. The patient was treated with a fusion from the occiput to C6. Pedicle screws were placed at the distal fixation point at C6 using the described freehand technique with direct visualization. (B) Hardware remained intact on three-year follow-up lateral radiographs. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

Figure 3. A man in his late 40s presented with a bony lesion at C2 that was found to have enlarged after three years of monitoring.

(A) Preoperative sagittal MRI showed the lesion at C2 with epidural extension causing spinal cord compression. (B) Preoperative axial computed tomography (CT) showed a lytic bony lesion eccentric to the right side of C2. A transoral biopsy confirmed a pathologic diagnosis of chordoma, and the patient underwent a two-stage resection and reconstruction surgery. Posterior fixation was performed from the occiput to C4 with pedicle screws placed at the distal anchor point at C4 using the freehand technique with direct visualization. A second-stage anterior approach was then performed for en bloc tumor resection and anterior column reconstruction using a modified Harms cage and screws from the clivus to the C3 vertebral body. Three-month postoperative anterior-posterior (C) and lateral (D) radiographs showed intact hardware. (E-F) Six-month sagittal CT slices showed arthrodesis spanning the corpectomy (arrows). Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

Figure 4. A man in his mid-50s presented with a bony lesion eroding the left C1 lateral mass.

Preoperative sagittal (A) and axial (B) MRI showed a lesion in the left C1 lateral mass. (C) Preoperative coronal CT showed the lytic bone lesion. Biopsy results confirmed the diagnosis of plasma cell myeloma. The patient underwent fixation from the occiput to C3 with pedicle screws placed at the distal fixation point at C3 using the freehand technique with direct visualization. Three-month postoperative lateral (D) and anterior (E) radiographs showed intact hardware. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.