| [Objective] The biomechanical advantage of a three-column fixation device implanted to secure an unstable cervical spine has proven to be a valuable tool in the spine surgeon's armamentarium. Successful placement of a pedicle screw in the cervical spine requires a sufficient three-dimensional understanding of pedicle morphology to allow accurate identification of the ideal screw axis. Variability in cadaveric based morphometric measurements used to guide the surgeon in the placement of a pedicle screw has raised legitimate concerns as to whether transpedicle fixation can be applied without significant neurovascular complications. Only surgeons experienced in transpedicle screw fixation and surgery of the cervical spine should perform this method of instrumentation.. The smaller size of cervical pedicles and variability in pedicle morphometry demand careful assessment of the angle and placement of transpedicular screws. Incorrect insertion of pedicle screwscan cause damage to adjacent vital structures such as thespinal cord, nerve roots, and vertebral arteries. With aquantitative understanding of cervical pedicle morphologyalong its axis and at different spinal levels, it shouldbe possible to improve the percentage of successful surgicaloutcomes while minimizing risk to the patient. The isthmus is extends on the pedicle axis thread the narrowest spot, The pedicle can withstand large diameter the screw to be decided by this plane. Therefore, Is familiar with and grasps anatomical morphology characteristic of the isthmus of pedicle to implant in the technology in the cervical vertebra after the pedicle screw to appear especially importantly. Sets at the nail front screw trajectory drilling security and the accuracy is in particular becomes the surgery success or failure the key. In order to solve has the sharp thread the traditional drill bit to set at the nail front screw trajectory drilling secure energy balance prominent question, We independently design the safety drill bit will apply in the lower cervical pedicle sets at the screw trajectory drilling after the pedicle screw. The objective of this study was to evaluate the accuracy of the safety drill technique of cervical pedicle screw placement. To explore the accuracy and safety of safety drill prepare for cervical pedicle screw trajectory. [Methods] fourteen adult cadaver specimens of cervical spine (C3～C7)with intact structures including ligaments and perivertebral muscles were reserved and used. 2.The gain pedicle isthmus department CT reconstruction data selects GElightspeed16 CT, Level thick 1.25mm thin layer scanning ,And uses the reconstruction software oblique reconstruction pedicle shape On the cross section graph surveys the pedicle axis thread length (L),Pedicle axis thread and arrow shape surface include dangle (A1),And in flank angle of departure (A2,A3).The three dimensional reconstruction pedicle isthmus department and surveys the isthmus of pedicle width (IEW). 3.The experiment groups (1) stochastically to divide into two groups: High period of service and low period of service group (2) presses implants the angle differently to enter nails toch astically to divide 7 groups, First group of 2,(E,A1) this group for best enters the road plan ,Second group of 2 (E,A1-A3),Third group of 2 (E,A1+A2). 4th group of 2 (E1, A1-A3). 5th group of 2 (E1,A1). 6th group of 2 (E2,A1+A2). 7th group of 2 (E2,A1). 4.Laboratory procedure simulation cervical vertebra rear guard surgery process, Selects the safety drill bit ,Its front end circle is obtuse, Does not have the thread ,Has the certain elasticity, Has to the cerebral cortex bone avoids the function on own initiative, Cannot create the cerebral cortex bone damage, Establishes nail according to the phantom study survey result and enters the nail direction, Carries on the safety drill bit the cervical vertebra after the pedicle screw passageway drilling. Will process after the centrum to arrange firmly with the jig, Selects feel law to implant the safety drill bit. Uses the rongeur first to nip eliminates enters drills a cortex , The diameter 1.0mm silk core testing observes the vertebral arch root entrance spot ,Diameter 1.7mm nose bluntness probe survey pedicle axis thread direction, A mount used horn ware survey angle ,Is away from d with the straight scale division measurement access distance side block most outflow boundary ,Selects the diameter 2.0mm safety drill bit , Respectively by A1,A1-A3,A1+A2 three kind of angles, Three entrances spots ,Implants the safety drill bit in three groups of centrums vertebral arch roots, Enters drills the depth for the technique in front of a CT survey pedicle axis hairs breadth nail length 60%. Searches with the probe observes, According to the technique feel confirmation pedicle four walls is the osseous ,For correctly implants. Like has the unusual situation tomake there cord. Safety drill bit drilling hole magical skill CT scanning, And oblique three dimensional reconstruction passageway shape ,Observes in the cross section in the flank cerebral cortex infrigement degree, On arrow strong surface on underneath cerebral cortex infrigement degree And take the naked eye line-of-sight observation result as the golden standard, Appraisal passageway drilling success or failure. According to the radiographic measurements, safety drill was inserted into cervical pedicle individually. The evaluation of the drill`s trajectory was carried out by CT scan and three-dimension reconstruction and autopsy. [ Result and discussion ] 1. C3～C7 pedicle axis ray breadth CT survey data , Including pedicle axis sagittal angle A1,In flank angle of departure A2,A3,Pedicle axis length (L) , Isthmus of the pedicle width IEW, After pedicles projection point and articular process plane point of intersection (E) and articular process most outflow boundary vertical range( d). Various parameters result sees (table one). The next cervical vertebra pedicle CT measurement result indicated that, The C4 isthmus department inside diameter is smallest,C6,The C7 isthmus department inside diameter is biggest. The pedicle axis thread length, arrow shape position angle C3～C7 does not have the obvious difference. This result and Abumi [ 13 ] there sult is close. 2.Sets at the nail passageway drilling result to divide into correct (invertebral arch root, does not have cerebral cortex infrigement) and is wrong (infrigement pedicle cerebral cortex or wears out)two kinds. Because cervical pedicle... |
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