Experimental Study Of Dual Placement In Atlantoaxial Pedicle Using Spinal Navigation Surgery Robot

BACKGROUNDAtlantoaxial pedicle screw technique with three-dimensional fixed effects is thought to be the most stable instrumentation for reconstructive surgery of the cervical spine. However, because the atlantoaxial pedicle is narrow and large variable, there are unresolved and inherent risks of neurovascular injuries due to screw perforation, it remains not widespread nowadays despite the excellent biomechanical property. Reported in the literature, the rate of perforation is 6% -8% in the placement of atlantoaxial pedicle by hand. Computer-assisted navigation system includes digital oriented template improved the accuracy of placement obviously, but there are 1.7% of perforation rate. Therefore, it is a critical task need to be solved urgently that improve the accuracy of atlantoaxial pedicle screw placement ulteriorly.OBJECTIVETo explore the principle of spinal surgical navigation surgery robot atlantoaxial transpedicular dual placement with the aim of establishing a high accurate and easily takled atlantoaxial transpedicular dual placement technique.METHODSDual placement in atlantoaxial pedicle using spinal navigation surgery robot through registration of virtual line, proceed as follows:1.Setting Tranverse Lines and Perpendicular LinesPrior to surgery, on CT scanning image bisecting atlantoaxial pedicle in superior/inferior, each point was selected on both sides of sagittal line respectively, which located on vertebra arc-shaped epiphyseal line. The line segment across the above two points was named TL (tranverse line).The midline cuts TLA and the line tangent to the furthest point of at the back of atlantoaxial respectively, and the line segment across the two points was named PL (perpendicular line), thus TL and PL which have known length and orthogonality were set on vertebra. One tranverse line and one perpendicular line with the same length to TL and PL respectively were set in vitro on dual placement manipulator.2.Matching Tranverse Lines and Perpendicular LinesIntraoperatively, the two tranverse lines and two perpendicular lines were matched respectively under X-ray lateral fluoroscopy on condition as follows:(1) Two Parallel registration arm is always perpendicular to the center lines of projection, the projections of tip is in the center line projection of C-arm;(2) Take the central axis of two registration arm bisecting atlantoaxial pedicle in superior/inferior under X ray lateral fluoroscopy and the tip of manipulator's registration arm contact tightly the surface of vertebra.(3) The projection of locating block bottom line is just contact to the point with center axial of atlantoaxial pedicle in superior/inferior and the edge of the intersection of cortical bone.3. Dual placement under dynamic monitoringThe length between both guide-wires'tip was set equally to the length of both entry points, the angle between the centre axis line of pedicle and the midline equally to preoperative measurements, dual placement along the centre axis line of pedicle can be conducted with Spinal Navigation Surgery Robot with real-time monitoring.Postoperative MeasurementsEach vertebra underwent postoperative vertebra body axial and lateral radiographs as well as CT scans to assess guide-wire trajectory. (1) the angle between the trajectory and the Sagittal Plane (post a); (2) the angle between the trajectory and the coronal plane (postβ); (3) the vertical distances from the actual entry point to inferior and lateral side of pedicle isthmus respectively (dn,dm).Statistical AnalysisThe results were expressed asx±s. Paired t test was used to analyze the difference between preoperative and postoperativeα,β;dm and dn with SPSS 17.0. Statistical significance was determined at the 0.05 Alpha level.RESULT(1) The pedicles was placement successfully in total of 24 atlantoaxial vertebrae (48pedicles). In postoperative vertebra body axial and lateral radiographs, the trajectory were demonstrated staying in the central core of the pedicle, none of the trajectory was found to have contracted or perforated the pedicle walls.(2) The excursion of direction between post/pre-operative:α:0.09±1.01°(P=0.53);β:-0.02±1.09°(P=0.89)。There was no statistical difference between post/pre-operative data respectively (P>0.05).(3) The medial/lateral vertical and superior/inferior distance from entry point to the planned was dm:0.13±0.62mm(P=0.14); dn:0.05±0.18mm(P=0.08) respectively. There was no statistical difference between post/pre-operative data respectively also (P>0.05).CONCLUSION With the application of Spinal Navigation Surgery Robot to dual placement on atlantoaxial vertebra, when inside and outside traverce line, perpendicular line were matched respectively, and the tip of manipulator's registration arm contact tightly arc-shaped surface of vertebra, the tips of both guide-wires locate nowhere but the entry points of both pedicles. With real-time monitoring, dual placement along the centre axis line of pedicle can be performed with Spinal Navigation Surgery Robot., which can provide a more safe, accurate, and easily tackled method for the study of atlantoaxial placement.