Design And Application Of A Portable Pedicle Screw Navigator Based On MINS And BIA Techniques

BackgroundIn 1959,Boucher first applied pedicle screw instrumentation to lumbar fusion surgery.In recent years,with the progress of science and technology the development of modern medicine,the pedicle screw instrumentation has been widely used for internal fixation in spinal procedure for its characteristics of three-column fixation,reasonable biomechanics and firm stability,which can correct the deformity in the coronal,sagittal,and axial planes.However,how to achieve precise placement of pedicle screws is a significant conundrum for clinicians.There are still 21%to 41%screw malposition rate.Because of close proximity to spinal canal and surrounding vessels,misplacement of pedicle screw frequently develops complications which can cause to paralysis or death in severe cases.Some procedures such as x-ray fluoroscopy,computer-aided technique,and robot-assisted surgery are now being increasingly used for the sake of improving the precision of pedicle screw,but there is still some limitation,including large volume,high price,complexity,radiation exposure,and cumbersome operation.Therefore,it is necessary to research and develop an inexpensive,stable,easy to handle navigator based on micro inertial navigation sy stem(MINS)and bioelectrical impedance analysis(BIA).MethodsThe novel and portable navigator,based on micro inertial navigation system and bioelectrical impedance technique,was used to improve precision of pedicle screws.The develop navigator will be applied to animal experiments using twelve pigs for accuracy and safety validation.1.Twelve healthy Wuzhishan male minipigs of similar age and weight(10-12.5kg)were used in this experiment.At the end of the feeding period,all the pigs underwent CT scan,and then generated simulated screw trajectories on a 3D reconstruction.2.Anesthesia was induced using an intramuscular injection of xylazine(1.5ml),tiletamine(2.5ml),and tiletamine hydrochloride(2.5ml).Infusion doses of atropine(0.1ml)and propofol(5ml)were administered through the outer vein on the edge of the ear for anesthesia.After endotracheal intubation,a general anesthesia was maintained with mechanical ventilation and inhalation of 1.0%to 2.0%.3.An incision was made over the mid lumbar region,and the spinous process,lamina and articular processes was exposed.The screws were implanted into pedicle using a navigator-assisted technique in MINS-BIA group,and the FH group via freehand technique.The surgeon recorded the screw trajectory and measured bioelectrical impedance values during the entire surgery.4.Pigs were CT scanned again after sacrificed,pedicle screw traj ectory angulation and pedicle breach in axial and sagittal planes were measured and investigated using postoperative 3-D reconstruction.The comparisons of preoperative and postoperative pedicle screws trajectory are performed.Authors also compared the accuracy of detecting impending breach between BIA and free-hand technique.Results1.A total of 216 screws were placed into 12 minipigs(each group had 108 pedicle screws).There are 15 pedicle breaches in the navigator group,and 31 in the free-hand group.The detection rate of these breaches was 14/15(93.3%)for the navigator device compared to 25/31(80.6%)by the free-hand technique.There are statistically significant difference between these two groups(P<0.01).The sensitivity and specificity of the pedicle navigation to detect impending breach were 93.3%and 96.8%.The negative predictive value and positive predictive value were 98.9%and 82.3%.For the surgeon by free-hand technique,the sensitivity and specificity to detect impending breach were 80.6%and 93.5%.The negative predictive value and positive predictive value were 92.3%and 83.3%.2.The mean offsets between the planned and postoperatively measured till angles of the screw trajectory were 4.5°±2.80 for the axial plane and 4.8°±3.3°for the sagittal plane.For the free-hand technique,the mean offsets between the planned and postoperatively measured tilt angles of the screws were 7°±5.1° for the axial plane and 7.7°±4.7° for the sagittal plane.The differences between the two groups were statistically significant.The differences between the two groups were statistically significant(P<0.01).ConclusionThe’ novel and portable navigator,based on micro inertial navigation system and bioelectrical impedance technique,was designed to provide a simple,safe,and sensitive approach for the pedicle screw placement.The detection of iatrogenic cortical bone perforation can be achieved most conveniently by bioelectrical impedance analysis.Micro inertial navigation systems can provide actual screws trajectory accurately in real time.