Design, Manufacture And Experical Study Of A Pedicle Piercer With Early Warning Device

Objective To design a pedicle piercer with early warning device which can provide real time auto alarm before the piercer would penetrate through vertebral body on the pedicle screw system of T₈～L₅.It can prompt surgeon to change drilling direction,and avoid damaging important nerves and blood vessel.Methods A pedicle piercer with early warning device(Pedicle-guide to call for short) was designed,which could warn by sound and light at once when the pressure increased stress at the threshold.Study of the threshold:The condition of the threshold was what the maximum pressure in the vertebral bodies was greater than the maximum pressure when Pedicle-guide penetrated through cortical bone.Maximum pressure was measured when the Pedicle-guide penetrated through cortical bone and cancellous bone of T₈～L₅.Eight thoracolumbar(T₈～L₅) spine specimens of normal adult body were randomly divided into 4 groups.Group 1,the maximum pressure was tested when Pedicle-guide penetrated through cancellous bone of vertebrae.Group 2,the maximum pressure was tested when Pedicle-guide penetrated through anterior vertebral cortical.Group 3,the maximum pressure was tested when Pedicle-guide penetrated through vertebral cortical of lamina terminalis and vertebral notch.Group 4, maximum pressure was tested when Pedicle-guide penetrated through the lateral vertebral cortex of vertebrae and pedicle.The threshold was set after statistical analysis.The effect of warning:Four spine specimens were choosen,included T₈～L₅,eighty vertebrae.The entry site for each pedicle was identified using anatomic landmarks based on estimation of the pedicle projection dorsally,our routine method in clinical practice.The screw channel was prepared with Pedicle-guide,the result of everyone was recorded.The screw channel was dissected,and the position between screw channel and cortex of vertebrae was compared.The effect of warning was analysis by using statistics.Results There was significant difference between the maximum pressure in the vertebral bodies and the maximum pressure when Pedicle-guide penetrated through cortical bone (P＜0.01).The threshold is 9.6～12.3kgN after statistical analysis.In the testing of the effect of warning,diagnostic effciency was 92.5%,senstivity was 92.31%,specificity was 95.12%,diagnostic availabiity was 87.45%,Youden index was 87.43%.The results was satisfactory.Conclusion The results of this in vitro study suggest the Pedicle-guide can sound the alarm and light immediately on pedicle screw fixation of T₈～L₈.It can be used as auxiliary surgical instruments on the operation of traditional pedicle screw fixation.