PURPOSE: To study the surgical morphometry of C1 and C2 vertebrae in Chinese, Indian, and Malay patients.
OVERVIEW OF LITERATURE: C1 lateral mass and C2 pedicle screw fixation is gaining popularity. However, there is a lack of C1-C2 morphometric data for the Asian population.
METHODS: Computed tomography analysis of 180 subjects (60 subjects each belonging to Chinese, Indian, and Malay populations) using simulation software was performed. Length and angulations of C1 lateral mass (C1LM) and C2 pedicle (C2P) screws were assessed.
RESULTS: The predicted C1LM screw length was between 23.2 and 30.2 mm. The safe zone of trajectories was within 11.0°±7.7° laterally to 29.1°±6.2° medially in the axial plane and 37.0°±10.2° caudally to 20.9°±7.8° cephalically in the sagittal plane. The shortest and longest predicted C2P screw lengths were 22.1±2.8 mm and 28.5±3.2 mm, respectively. The safe trajectories were from 25.1° to 39.3° medially in the axial plane and 32.3° to 45.9° cephalically in the sagittal plane.
CONCLUSIONS: C1LM screw length was 23-30 mm with the axial safe zone from 11° laterally to 29° medially and sagittal safe zone at 21° cephalically. C2P screw length was 22-28 mm with axial safe zone from 26° to 40° medially and sagittal safe zone from 32° to 46° cephalically. These data serve as an important reference for Chinese, Indian, and Malay populations during C1-C2 instrumentation.
PURPOSE: The C1 and C2 laminas in the Malaysian Malay population were analyzed for the feasibility of fitting 3.5-mm laminar screws in a cross configuration.
OVERVIEW OF LITERATURE: Morphometric analysis of the C1 and C2 laminas has been performed for various populations but not for the Malaysian Malay population.
METHODS: A total of 330 CT cervical images were measured to establish the bicortical diameter of the C1 and C2 laminas as well as their height and length. The C1 posterior tubercle bicortical diameter and height were also determined from these images. All parameters were measured up to 0.1 mm, and statistical analysis was performed using IBM SPSS Statistics ver. 24.0 (IBM Corp., Armonk, NY, USA). An independent t -test and the Pearson chi-square test were used to determine the mean difference and screw acceptance.
RESULTS: The means of the C1 lamina measurements were 5.79±1.19 mm in diameter, 9.76±1.51 mm in height, and 20.70±1.86 mm in length. The means of the measurements of the posterior tubercle were 7.20±1.88 mm in diameter and 10.51±1.68 mm in height. The means of the C2 lamina measurements were 5.74±1.31 mm in diameter, 11.76±1.69 mm in height, and 24.96±2.56 mm in length. Overall 65.5% of C1 and 80.3% of C2 laminas are able to accept 3.5-mm screws in a cross configuration. Screw acceptability is similar between the right and left sides (p >0.05). However, males have a higher screw acceptability compared with females (p <0.05), except for the C2 left lamina.
CONCLUSIONS: It is feasible to insert a 3.5-mm screw in a cross configuration in the C1 and C2 laminas of the Malaysian Malay population, especially in males. However, a CT scan should be performed prior to the operation to determine screw acceptability and to estimate screw sizes.