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.
METHODS: A cross-sectional analysis involving 102 MRIs that met the inclusion criteria was obtained and analyzed at the L3/L4, L4/L5, and L5/S1 discs level. For each level, the Kambin triangle was measured. By evaluating those measurements, the viability of this method was determined.
RESULTS: Safe working zone approach angles were consistently getting wider from L3 to S1 levels. It was statistically significant to be wider for the left side for the mean angle of lateral nucleus trajectory at the L4/L5 level and L5/S1. The entry point is at 32, 45, and 55-60 mm from the midline, and the instrument should be directed at 12°, 20°, and 27° medially for the lateral nucleus at L3/L4, L4/L5, and L5/S1, respectively. The center of the nucleus pulposus entry point is at 64, 77, and 85 mm from the midline with a medial inclination of 40°, 47°, and 52°, respectively, for L3/L4, L4/L5, and L5/S1. For the posterior nucleus pulposus, the skin should be pierced 90, 140, and 180 mm from the midline and directed medially at 53°, 61°, and 68°, respectively, for L3/L4, L4/L5, and L5/S1. The posterior annulus fibrosis entry point is 172, 355, and 450 mm with a medial inclination of 69°, 80°, and 84° at L3/L4, L4/L5, and L5/S1, respectively. The sagittal inclination is 3° cephalad at L3/L4, 10° caudally at L4/L5, and 27° caudally at L5/S1.
CONCLUSIONS: Preoperative MRI assessment is important to determine the angle of trajectory for the safe entry point for intradiscal procedure via transforaminal approach.