PT  - JOURNAL ARTICLE
AU  - Storey, Richard N.
AU  - Baker, Joseph F.
TI  - Feasibility of C2 Lamina Screw Placement in a New Zealand Cohort: Computed Tomography Analysis According to Ethnicity and Gender
AID  - 10.14444/8600
DP  - 2024 Apr 26
TA  - International Journal of Spine Surgery
PG  - 8600
4099  - https://www.ijssurgery.com/content/early/2024/04/26/8600.short
4100  - https://www.ijssurgery.com/content/early/2024/04/26/8600.full
AB  - Background Previous analyses have suggested variations in cervical spine canal morphology according to ethnicity, possibly in part due to variations in the posterior elements. The potential for these variations to affect the placement of instrumentation is uncertain. The aim of this study was to report on the feasibility of C2 lamina screw insertion in a New Zealand cohort including analysis of Māori, the indigenous people of New Zealand.Methods A trauma computed tomography database was accessed to identify suitable images. On axial images, where the isthmus was at its widest, the outer diameter (OD) and inner diameter (ID) of the lamina were measured. Screw length was measured from a proposed entry point to the contralateral junction of the lamina and lateral mass. The spinolaminar angle was measured as the angle subtended by the screw trajectory and midsagittal plane. A 5.5-mm OD was accepted as a threshold for the feasibility of lamina screw placement.Results One hundred eighty-seven images were assessed: 115 New Zealand European and 72 Māori. The mean age of the cohort was 41.9 years (SD 19.6), and most patients (64%) were men. For the entire cohort, mean OD was 6.6 and 6.8 mm on the right and left, respectively; the mean inner diameter was 3.5 and 3.8 mm; mean screw length was 31.5 and 31.5 mm; and mean spinolaminar angle was 46.0° and 46.1°. C2 lamina screw placement was feasible in a majority of patients. Considering only Māori patients, placement was feasible in 96% of right and 94% of left laminae in men but 72% of right and 72% of left laminae in women.Conclusions In a majority of patients, C2 lamina screw placement is feasible. However, advanced imaging must be carefully assessed preoperatively because data suggest that Māori women may not necessarily have optimal anatomy.Clinical Relevance Care needs to be taken when assessing and planning surgery inpatients of different ethnicities because variations may exist in the morphology of the posterior elements of C2, leading to variation in optimal fixation strategy.Level of Evidence 3.