Impact on the Intervertebral Foramen After Posterior Cervical Fixation Surgery Using Cervical Pedicle Screws

Area of Science:

• Neurosurgery
• Spinal Surgery
• Radiology

Background:

• Cervical spondylotic myelopathy (CSM) often requires surgical intervention.
• Posterior cervical fixation with pedicle screws is a common surgical approach for CSM.
• Understanding postoperative changes in intervertebral foraminal areas is crucial for preventing complications.

Purpose of the Study:

• To compare postoperative changes in intervertebral foraminal areas after posterior cervical fixation for CSM.
• To elucidate the mechanisms of foraminal stenosis following this surgical procedure.
• To investigate the correlation between spinal alignment changes and foraminal area modifications.

Main Methods:

• Retrospective analysis of 55 patients undergoing posterior cervical pedicle screw fixation.
• Measurement of intervertebral foraminal dimensions (craniocaudal, anteroposterior diameters, and area) using 3D computed tomography (3DCT) pre- and postoperatively.
• Calculation of the segmental angle change (α angle) to quantify spinal alignment shifts.

Main Results:

• The primary mechanism of foraminal stenosis was identified as a "lag effect" from posterior vertebral slippage.
• Foraminal area tended to increase with corrections < 0°, but significantly decreased with corrections > 10° (p < 0.01).
• An α angle ≥ 10° led to a 16.4% reduction in foraminal area, with a notable 26.9% decrease at C4/5 associated with C5 palsy.

Conclusions:

• Posterior cervical fusion can alter intervertebral foraminal dimensions.
• Excessive correction (α angle ≥ 10°) is a risk factor for foraminal narrowing and subsequent nerve root compression.
• These findings aid in optimizing surgical techniques to prevent postoperative nerve root palsy, including C5 palsy.