Pedicle morphology of the immature thoracic spine in children aged 1 to 6 years

English Keywords:horacic vertebra  Pedicle  Spiral computed tomography  Sectional and imaging anatomy  Children

English Abstract:

  【Abstract】 Objectives: To quantify the morphometric characteristics of the pedicles of the immature thoracic spine（aged 1 to 6 years old）, and to provide morphologic basis pedicular screw instrumentation. Methods: A total of 60 patients without muscularskeletal disease and aged 1 to 6 years underwent standard spiral computed tomography of the chest in Beijing children′s hospital. The patients were grouped according to age: group 1(1-2 years old), group 2(2-3 years old) and group 3(4-6 years old), with 20 cases per group． For each case measurement was taken from pedicles on both sides from T1 to T12. Images were reconstructed by the 64 row helical CT and multiplanar reconstructions were used to attain images of thoracic pedicles on sagittal, coronal, and transverse planes. The measurements included the inner and outer pedicle diameters on both transverse and sagittal planes, the pedicle angle on both transverse and sagittal planes, and distance to anterior cortex. Their correlations with age were analyzed, inter-group comparisons of transverse pedicle angle(TPA)/sagittal pedicle angle(SPA) were analyzed using Multiple T test. Results: (1)Transverse pedicle diameters decreased gradually from Tl to T4, and then increased gradually from T5 to T12. The shortest transverse diameter of the thoracic pedicle located at T4 or T5. There was no correlation between the transverse pedicle inner diameter and age, except T1, T6, T11, T12(rs: 0.011-0.363, P>0.05, except T1, T6, T11, T12). The correlations between age and the transverse pedicle outer diameters were significant in all thoracic vertebra except T4(rs: 0.151-0.539, P<0.05, except T4). (2)Sagittal pedicle diameters increased from Tl to T12 and was significant longer than transverse diameter except T1. The correlations between age and sagittal pedicle diameters were significant in all thoracic vertebra(the inner rs: 0.526-0.786, the outer rs: 0.692-0.864, P<0.05). (3)The length from posterior cortex to anterior cortex of the vertebra increased from T1 to T10, decreased slightly from T10 to T12. The correlations between age and the length to anterior cortex were significant in all thoracic vertebrae(rs: 0.299-0.676, P<0.05). (4)The transverse pedicle angle decreased gradually from T1 to T12 though some cases did not show this trend. The correlations between age and TPA were significant in all thoracic vertebra except T1[rs: (-0.432)-(-0.107), P<0.05, except T1]. TPA in group 1 were significantly greater than group 2 and 3(P<0.05), there was no significant difference between group 2 and 3(P>0.05). (5)There was no significance with respect to the sagittal pedicle angles between three groups. There was no correlation between SPA and age[rs: (-0.125)-0.127, P>0.05]. There was no significant difference among three groups(P>0.05). Conclusions: The correlations between age and the transverse pedicle outer diameters, the sagittal pedicle diameters, distance to anterior cortex are significant in all thoracic vertebra of children aged 1-6 years. However, the transverse pedicle inner diameters increase slowly with age. There is no correlation between the transverse pedicle inner diameters and age nor between age and the pedicle angle on both the transverse and sagittal planes. The angular dimensions show little change due to vertebral growth except group 1. It is cautious to place thoracic pedicle screw in patients aged below 6 years in order to avoid high risks.