Na. Ebraheim et al., COMPUTED TOMOGRAPHIC EVALUATION OF THE INTERNAL STRUCTURE OF THE LATERAL MASS OF THE LOWER CERVICAL-SPINE, Orthopedics, 21(11), 1998, pp. 1207-1210
Axial computed tomography scans with a slice thickness of 2 mm taken f
rom 12 cervical spines were used to study the internal structure of th
e lateral mass. Images representing the middle of zone I (Heller's cla
ssification) and the top of zone III were analyzed. The measurement of
zone I involved anterior cortex thickness (ACT) while measurements of
zone III included ACT, lateral cortex thickness (LCT), posterior cort
ex thickness (PCT), lateral mass thickness (LMT), and lateral mass wid
th (LMW). The percentage of the ACT and PCT with respect to the LMT (A
CT/LMT and PCT/LMT) were calculated. Results showed the average ACT in
zone I ranged from 1.6 to 1.8 mm. In zone III, the average LMT and LM
W ranged from 8 to 9 mm and 13 to 15 mm, respectively. The smallest LM
T was found at C7. The average ACT and PCT for all levels ranged from
1.8 to 2 mm. The ACT with respect to the LMT (ACT/LMT) was approximate
ly 17% to 19% for C3 to C5 and C7, and 15% for C6 separately. The PCT
with respect to the LMT (PCT/LMT) was approximately 16% to 18% for C3
to C6, and 20% for C7. These results show the ventral cortex of the la
teral mass is relatively thicker and support the concept of bicortical
screw purchase.