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Anatomical feasibility for safe occipital condyle screw fixation
Ho Jin Lee1, Doo Yong Choi1, Myoung Hoon Shin1
1Department of Neurosurgery, Incheon St. Mary's Hospital, The Catholic University of Korea, Incheon, Korea.
Summary
Direct occipital condyle screw fixation is often not feasible due to vertebral artery proximity. Anatomical variations limit safe screw placement in a significant portion of patients across age groups.
Area of Science:
- Neurosurgery
- Anatomy
- Radiology
Background:
- Occipital condyle (OC) screws offer an alternative for occipito-cervical fixation.
- Assessing the risk of vertebral artery (VA) injury during direct OC screw fixation is crucial.
Purpose of the Study:
- To determine the course of the V3 segment of the VA relative to adjacent bony structures.
- To evaluate the feasibility of direct OC screw fixation based on anatomical relationships.
- To analyze how age and sex influence these anatomical relationships.
Main Methods:
- Analysis of 387 three-dimensional computed tomographic angiograms (3D-CTA).
- Measurement of occipito-C1 arch space (O-C1S) and VA-occipital bone distance (VOD).
- Determination of a minimum feasible VOD of 4 mm for direct OC screw fixation.
Main Results:
- Mean VOD ranged from 3.2 to 3.5 mm, with only 32-42% of individuals having feasible direct OC screw placement.
- No significant differences in feasibility were found between age groups or by gender.
- Upper cervical spine kyphosis correlated with increased space for OC screw placement.
Conclusions:
- Direct OC screw fixation is not consistently possible due to limited space and VA proximity, irrespective of age.
- Bilateral direct OC screw placement was feasible in only 21-24% of patients.
- Cervical spine alignment, particularly kyphosis, influences the available space for OC screw fixation.
