ABSTRACT
Purpose To investigate the value of quantitative evaluation of upper urinary tract pump function after unilateral lower urinary tract obstruction using 640-slice dynamic volumetric CT. Materials and Methods Twenty-six healthy subjects (control group), thirty cases of acute upper urinary tract obstruction caused by unilateral ureteral calculi and thirty cases of chronic upper urinary tract obstruction were selected, all receiving dynamic volume scan of 640-slice dynamic volumetric CT during renal excretion. The value of contrast agent volume, volumetric difference, time difference correspondent to the difference, volumetric change rate, and flow rate in ureteropelvic and partial upper ureter were calculated and analyzed. Results Volumetric change rate of obstruction side of upper urinary tract in acute obstruction group was higher than that of contralateral upper urinary tract. Volumetric average value, volumetric difference and flow rate were increased with time difference value decreased, the difference of which were all statistically significant (P<0.001). Volumetric change rate, volumetric difference and flow rate of obstruction side of upper urinary tract in acute obstruction group was lower compared with those of contralateral upper urinary tract, while volumetric average value and time difference raised, the difference was statistically significant (P<0.001). The difference of five pump function values among acute obstruction group, obstruction side of chronic obstruction group and control group were statistically significant (P<0.001). Conclusion 640-slice dynamic volumetric CT can be used to quantitatively evaluate changes of urinary tract pump function in physiological and obstructive status.
ABSTRACT
Objective To compare the biomechanical properties of single-segment and two-segment fusion for Denis type B spinal fracture.Methods Two female patients with Denis type B L1 vertebral fracture were enrolled in this study.The 45-year-old patient (Frankel B) underwent posterior reduction and fixation with pedicle screw system plus anterior two-segment fusion and the 41-year-old patient (Frankel C) underwent posterior reduction and fixation with pedicle screw system plus anterior one-segment fusion.The intervertebral fusion was achieved in both patients 1 year after operation.CT data of the two patients at 1 year after surgery was collected,including data of 41-year-old patient before and after removal of pedicle screws and data of 45-year-old patient without removal of pedicle screws.These three sets of data were imported into the Mimics software to establish T11-L2 three dimensional models.After construction of the models,they were imported into ANSYS software.An axial load (260 N) and 10 Nm torque were loaded to simulate the flexion,extension,lateral bending and rotation of the spine,respectively.Meantime,under above 6 kinds of motion form,the average displacement of the spine and the average Von Mises stress of T11-12 intervertebral disc were recorded and compared.Results There was no significant difference in the average displacement of the spine between two-segment fusion patient and single-segment fusion patient without removal of pedicle screws.However,under all motion forms,the average displacement of the spine of single-segment fusion patient after removal of pedicle screws was significantly higher than that before removal of pedicle screws and that of two-segment fusion patient.The average Von Mises stress of T11-12 intervertebral discs of two-segment fusion patient was significantly higher than that of one-segment fusion patient.Moreover,the average Von Mises stress of T11-12 intervertebral discs of single-segment fusion patient before removal of pedicle screw was higher than that after removal of pedicle screw.Conclusion Under the premise of satisfactory interbody fusion,removal of pedicle screws after one-segment fusion can increase spinal motion,reduce the stress of the adjacent intervertebral discs and delay disc degeneration.