Digital Study Of Thoracie Fixation By "Pedicle Rib Unit "Screws In School-Age Children

OBJECTIVE:To provide experimental theoretical basis for clinical application and enterprise design and production of internal fixation apparatus.By measuring the relevant development morphological parameters of thoracic spine internal fixation through"pedicle rib unit"?PRU?in school-age children,to explore its development regularity and morphological characteristics in different ages,genders and sides.METHODS:67 cases?male 35,female 32?of thoracic vertebrae(T₁?T₁₂)in7-12-year-old school-age children were selected,excluding the spinal diseases such as bone destruction,tumor,tuberculosis,deformity,fracture and the previous spinal operation history.Three dimensional reconstruction was performed after spiral CT scanning.The shape of Pru was observed.The diameter,length,inclination angle and the safety angle of Pru were measured and statistically analyzed.The feasibility of the nail placement in school age was discussed.RESULTS:1.The width of"pedicle-rib unit"?PRU-W?of the thoracic vertebra(T₁?T₁₂)increased with age,and the male in the same age group was larger than the female,but decreased first and then increased with the increase of the vertebra sequence;2.There was a significant difference in the theoretical length?PRU-L?of the pedicle rib unit(T₁?T₁₂)in different age groups?P<0.05?,which increased significantly with age,but increased first and then decreased with the increase of the vertebral sequence.In 7?9 age groups?group A?PRU-L showed no significant difference except that between T₁₂ genders?P<0.05?.However,in the age group of 10?12 years?group B?showed significant gender difference in T₃,T₅and T₆?P<0.05?.3.The included Angle between the central axis and the sagittal plane of the"pedicle rib unit"?PRU-A?showed significant difference between group A and group B?P<0.05?only at segments T₆,T₇ and T₁₂.The mean value of the two groups did not increase significantly with age.The changes of the anatomical structure of the pedicle of the thoracic vertebrae with the vertebral sequence are similar to those of the adult.The maximum and minimum values were all located at T₁ and T₁₂.4.The safety range of the minimum and maximum inclination Angle of screw placement via PRU is 18°?25°,and the maximum safety range of screw placement is T₁,followed by T₁₀,and the minimum is T₄and T₅.CONCLUSION:Thus,the width of"pedicle-rib unit"?PRU-W?and the theoretical length of the"pedicle-rib unit"?PRU-L?of the thoracic vertebra and the safety angle of the"pedicle-rib unit"?PRU-A?of the thoracic vertebra were significantly narrower in children than in adults.The included Angle between the central axis and the sagittal plane the"pedicle-rib unit"?PRU-A?was not significantly affected by age,and the closer it was to the tail of the thoracic sequence,the smaller the PRU-A would be.When the screw was fixed to the caudal thoracic vertebra with PRU screws,the screw point should be slightly moved out in order to smoothly enter the vertebral body and obtain better stability.Serious nerve,blood vessel and viscera damage may be caused if adult standard is taken as reference during PRU screw placement,so individual screw placement should be conducted according to preoperative CT results.