E-ISSN: 1019-5157
ISSN: 2651-5024
Research
C2 Vertebral Morphometry and Feasibility of Conventional C2 Instrumentation in Patients with Chiari I Malformation
Mehmet Sabri GÜRBÜZ✉ ,
Mohammed ALADDAM ,
Said ABUMARASA ,
Burak BAYRAKTAR ,
Ertugrul GÜLAY ,
Nadir Emre HERDAN ,
Başak ATALAY ,
Numan KARAARSLAN
Neurological Surgery, University of Wisconsin School of Medicine and Public Health; Neurosurgery, Istanbul Medeniyet University
DOI: 10.5137/1019-5149.JTN.50741-25.2
Article in Press
Corresponding Author:
Mehmet Sabri GÜRBÜZ (mehmetsabrigurbuz@gmail.com)
Abstract
Aim
To investigate C2 morphometry, prevalence of high-riding vertebral artery (HRVA) and feasibility of conventional C2 screw instrumentation for Chiari malformation type I (CM-I) patients without basilar invagination, and to compare these parameters with matched controls.
Material and Methods
This retrospective CT-based casecontrol study included patients with symptomatic CM-I who had thin-slice cervical CT (≤1 mm). Patients with basilar invagination or other craniovertebral junction anomalies were excluded. Controls were trauma patients who underwent cervical CT and were matched for age range and sex. C2 pedicle width, laminar thickness, isthmus height, and internal height were measured by a hypothesis-blinded neuroradiologist. Feasibility of 3.5-mm pedicle and laminar screws was defined as bilateral osseous corridor ≥4.0 mm. HRVA was defined as isthmus height <5 mm and/or internal height <2 mm on at least one side. Group comparisons using t-tests and/or Fishers exact tests were performed.
Results
Forty-seven patients were analyzed (28 controls, 19 CM-I). Groups were similar in age and sex distribution. CM-I patients had smaller C2 pedicle and isthmus widths bilaterally and reduced left laminar thickness, whereas internal height did not differ significantly between groups. Bilateral pedicle screw feasibility was present in 22/28 controls (78.6%) versus 9/19 CM-I patients (47.4%; Fisher p=0.034), laminar feasibility in 26/28 controls (92.9%) versus 13/19 CM-I patients (68.4%; Fisher p=0.047). HRVA (isthmus <5 mm and/or internal height <2 mm on ≥1 side) was present in 10/28 controls (35.7%) and 15/19 CM-I patients (53.2% overall), mainly driven by isthmus narrowing (Fisher p = 0.007).
Conclusion
CM-I patients without associated basilar invagination, exhibit hypoplastic C2 posterior elements, higher prevalence of HRVA and thus reduced feasibility for 3.5-mm pedicle and laminar screws compared to controls. Therefore, thin-slice CT and careful vertebral artery assessment are critical when planning instrumentation in this population, with a higher likelihood of requiring alternative techniques.
To investigate C2 morphometry, prevalence of high-riding vertebral artery (HRVA) and feasibility of conventional C2 screw instrumentation for Chiari malformation type I (CM-I) patients without basilar invagination, and to compare these parameters with matched controls.
Material and Methods
This retrospective CT-based casecontrol study included patients with symptomatic CM-I who had thin-slice cervical CT (≤1 mm). Patients with basilar invagination or other craniovertebral junction anomalies were excluded. Controls were trauma patients who underwent cervical CT and were matched for age range and sex. C2 pedicle width, laminar thickness, isthmus height, and internal height were measured by a hypothesis-blinded neuroradiologist. Feasibility of 3.5-mm pedicle and laminar screws was defined as bilateral osseous corridor ≥4.0 mm. HRVA was defined as isthmus height <5 mm and/or internal height <2 mm on at least one side. Group comparisons using t-tests and/or Fishers exact tests were performed.
Results
Forty-seven patients were analyzed (28 controls, 19 CM-I). Groups were similar in age and sex distribution. CM-I patients had smaller C2 pedicle and isthmus widths bilaterally and reduced left laminar thickness, whereas internal height did not differ significantly between groups. Bilateral pedicle screw feasibility was present in 22/28 controls (78.6%) versus 9/19 CM-I patients (47.4%; Fisher p=0.034), laminar feasibility in 26/28 controls (92.9%) versus 13/19 CM-I patients (68.4%; Fisher p=0.047). HRVA (isthmus <5 mm and/or internal height <2 mm on ≥1 side) was present in 10/28 controls (35.7%) and 15/19 CM-I patients (53.2% overall), mainly driven by isthmus narrowing (Fisher p = 0.007).
Conclusion
CM-I patients without associated basilar invagination, exhibit hypoplastic C2 posterior elements, higher prevalence of HRVA and thus reduced feasibility for 3.5-mm pedicle and laminar screws compared to controls. Therefore, thin-slice CT and careful vertebral artery assessment are critical when planning instrumentation in this population, with a higher likelihood of requiring alternative techniques.
Keywords
Chiari I malformation
C2 morphometry
laminar screws
cranio-vertebral junction
vertebral artery