Anatomical characteristics of the middle and lower thoracic pedicle in ankylosing spondylitis

English Keywords:Ankylosing spondylitis  Pedicle  Imaging parameters  CT 3D reconstruction

English Abstract:

  【Abstract】 Objectives: To compare the T5-T12 pedicle parameters in ankylosing spondylitis(AS) with those in normal people on the CT scan, in order to provide reference for pedicle screw placement. Methods: A total of 40 males AS(AS group) with complete clinical data, CT scan and three-dimensional reconstruction of the middle and lower thoracic spine from January 2003 to June 2017 was enrolled with the age ranging from 34 to 53 years old. And 40 males of thoracic vertebral fracture with complete clinical data, CT scan and three-dimensional reconstruction of middle and lower thoracic spine were selected(non-AS group), with the age ranging from 32 to 48 years old in the same period. The vertebral pedicle parameters from T5 to T12 were measured, including pedicle width(PW), pedicle height(PH), pedicle transverse angle(PTA) that between the pedicle axis and the median sagittal plane of the vertebral body, pedicles distance(PD), pedicle screw path length(PL). The measurements of two groups were compared. Results: The PW in AS and non-AS group increased gradually from T5 to T12. The PW in AS group was significantly smaller than that of non-AS group(P<0.05). There was no statistical difference of the PH between the two groups(P>0.05). The variation trend of PTA in the two groups was the same. The PTA gradually became negative(T5-T10 were positive, T11-T12 were negative) and the PTA in AS group was significantly smaller than that in non-AS group, but the results in T11 and T12 were opposite(P<0.05). The PD of the two groups gradually increased from T5 to T12, and it was significantly larger in AS group than that in non-AS group(P<0.05); the PL increased gradually from T5 to T12, and the PL in AS group was significantly larger than that in non-AS group(P<0.05). Conclusions: Long pedicle screw can be used to increase the strength of internal fixation in AS patients, but it is not suitable to increase the pedicle screw diameter. The pedicle screw angle is close to vertical. If necessary, it can be placed through pedicle-rib unit.