| Atlantoaxial-instability refered to the the atlantoaxial,intervertebral joints and ligamentous structures suffering trauma,malformations,tumors,inflammation and other damage,lossing normal physiological function and stability,and leading to atlantoaxial dislocation or subluxation,mergering or secondaring to the symptoms of irritation and compression of spinal cord and nerve root There was a serious risk in atlantoaxial instability to cause the signs and symptoms of compression of upper cervical spinal cord,nerve roots,vertebral artery.Therefore,it was usually taken into surgery.Clinical surgery on atlantoaxial instability was divided into posterior and anterior fixation currently.There were some main posterior fixation such as the Cl-2lamina wire technique,lamina clamp technique,magerl screw technique,posterior atlas lateral mass pedicle screws and rods technique.The mechanical properties of the Cl-2lamina wire technique,lamina clamp technique which were used early were poor,demanded for completing atlantoaxial rear structure,had unreliable fixation;The mechanical properties of "magerl" screw technique and posterior atlas lateral mass pedicle screws and rods technique improved,had reliable fixation.However,there were some special cases such as congenital incompleting atlantoaxial rear structure,the variation of the vertebral artery,gooseneck deformity,iatrogenic posterior bone structure resection,the anatomic variation on position and size of the atlantoaxial which should not be taken into posterior but anterior fixation and fusion.Posterior surgery was helpless in compression and adhesion which came from the front of the spinal cord,required anterior decompression and release, I or II period posterior fixation,turning over in surgery might cause fatal spinal cord injury,while increasing the cost of hospitalization of patients.Anterior surgery was mainly applied to the special cases such as congenital incompleting atlantoaxial rear structure,the variation of the vertebral artery which could not apply posterior surgery in the past.However,after developments in recent years,it was applied to various atlantoaxial instability and had the the advantage that posterior surgery did not have.Anterior transoral atlantoaxial titanium plate fixation could release,decompress and fix from the front side at the same time,which had been widely used for fresh and old traumatic atlantoaxial instability clinically,and had achieved a certain degree of efficacy.But there were fatal deficiencies that the surgical operation was in the case of pollution,susceptible,intraoperative injury of dural caused cerebrospinal fluid leakage,then infection would be difficult to control,so that threatened life.therefore,to anterior surgery,submandibular approach became a new choice,but there were not any satisfactory fixation devices currently.If atlantoaxial vertebral atlas lateral mass screw fixation was choosen,larger upper angle of the screw was required,which was easy to damage the spinal cord and the vertebral artery,in addition,high atlantoaxial integrity was required.The channel of anterior atlantoaxial transarticular screw passed through the pivot vertebral body and lateral mass of atlas from anteromedial to posterolateral,which could avoid penetrating the spinal canal to injure spinal cord,far away the vertebral artery,difficult to damage vertebral artery,reduced the risk of spinal cord vertebral artery injury.This internal fixation in our hospital had been popularized,and achieved satisfactory results,but the mechanical property of the technology was to be further improved,for the reason that it demanded for high axial bone structure.Otherwise,the screw would loose and prolapse for osteoporosis,difficult to operate.That comminuted fracture of the lateral mass of the atlas was not appropriate to apply this surgery. Anterior atlantoaxial transarticular anatomic locking titanium plate screw fixiation system (The Chinese patent No was ZL201120134687.X) was a new anterior atlantoaxial-instability internal fixation system we independently developed with independent intellectual property rights.There were some characteristic in the internal fixation system that had its own reposition functions locking mechanism with screws,aiming function to form an integration.This technique used the submandibular surgical approach that could apply anterior decompression and I period fixation at the same time,then simplified the surgical operation,strengthened internal fixation reliability.The feasibility and safety of new anterior atlantoaxial transarticular anatomic locking titanium plate screw fixiation system in atlantoaxial fixiation was investigated to provide anatomical reference for the design of a new anterior atlantoaxial transarticular anatomic locking titanium plate screw fixiation system by measuring the atlantoaxial anatomical parameters,screw channel parameters and safety distance related to anterior atlantoaxial transarticular anatomic locking titanium plate screw fixiation system.The clinical feasibility of a new anterior atlantoaxial transarticular anatomic locking titanium plate screw fixiation system was testified by surgical model and match assessment,then the superiority of this method was summarized,the defect was proposed at the same time in order to further improve,make it more perfect.Part one Anatomical measurement and clinical significance of anterior atlantoaxial transarticular anatomic locking titanium plate screw fixiation systemObjective The feasibility and safety of new anterior atlantoaxial transarticular anatomic locking titanium plate screw fixiation system in atlantoaxial fixiation was investigated to provide anatomical reference for the design and applyment of a new anterior atlantoaxial transarticular anatomic locking titanium plate screw fixiation system by measuring the atlantoaxial anatomical parameters,screw channel parameters and safety distance related to anterior atlantoaxial transarticular anatomic locking titanium plate screw fixiation system.Methods30sets of normal Chinese adults craniovertebral junction specimens soaked in formalin were scaned by Multislice Spiral Computer Technology(MSCT) on2.0mm thickness,the raw data acquired was delivered to Vitrea2workstation to conduct by Multi-planar Reconstruction (MPR) and Volume Rendering (VR) of Three Dimension CT Reconstruction.The screw parameter of the image of Multi-planar Reconstruction (MPR) which related to anterior atlantoaxial transarticular anatomic locking titanium plate screw fixiation system was measured by the measurement software the Vitrea2workstation comes with.Then the results obtained were statistically analyzed to evaluate the feasibility and safety of the fixation system.Results Atlantoaxial specimens were measured by Three Dimension CT Reconstruction preoperatively.The inner side wall spacing of atlantoaxial transverse foramen was (44.48±1.90)mm,the triangular protrusion part of the front structure of the vertebral was (17.68±2.26)mm,the anterior height of atlantoaxial vertebral was (20.56±0.81)mm,the anterior height was (16.48±0.68)mm,the coronal diameter of the inferior endplate was (22.00±1.71)mm,the sagittal diameter of the inferior was endplate (17.30±1.13)mm.The paired t-test was applied in the left and right screw channel parameters,and there was no statistically significant difference(P>0.05).Both the left and the right sides of the screw channel parameters were applied group merger,the lateral angulation of the atlantoaxial transarticular screw trajectory to the coronal plane ranged from14°to32°and the ideal angle was (23.05±1.90)°,the posterior angulation to the sagittal plane ranged from14°to42°and the ideal angle was (27.89±2.67)°,the length ranged from19mm to32mm and the ideal length was (27.49±1.23)mm;The inner angulation of the atlantoaxial screw trajectory to the horizontal plane ranged from0°to15°,the upper angulation to the sagittal plane ranged from0°to50°,the length ranged from15mm to21mm.Conclution There was enough screw placement space for Chinese atlantoaxial specimens,the anterior atlantoaxial transarticular anatomic locking titanium plate screw fixation system in atlantoaxial fixation was anatomicly safe and feasible for Chinese.Part two Match assessment of anterior atlantoaxial transarticular anatomic locking titanium plate screw filiation systemObjective The clinical feasibility of a new anterior atlantoaxial transarticular anatomic locking titanium plate screw fixiation system was testified by surgical model and match assessmentMethods The screw channel parameters of anterior atlantoaxial transarticular anatomic locking titanium plate screw fixiation system were taken as a reference,the surgical models of anterior atlantoaxial transarticular anatomic locking titanium plate screw fixiation were manufactured on the30sets of normal Chinese adults craniovertebral junction specimens soaked in formalin,then the surgical models were scaned again by Multislice Spiral Computer Technology (MSCT) on2.0mm thickness postoperatively,the raw data acquired was delivered to Vitrea2workstation to conduct Multi-planar Reconstruction (MPR) and Volume Rendering (VR) of Three Dimension CT Reconstruction.Then the correlated screw trajectory parameters and the distance between atlantoaxial transarticular screw and vertebral artery,spinal cord in different planes,the upper articular surface of the lateral mass of atlas of Multi-planar Reconstruction (MPR) which related to anterior atlantoaxial transarticular anatomic locking titanium plate screw fixiation system were measured.At the same time DR was applied postoperatively to analyze the match between fixation system and atlantoaxial by observing the relative position of the titanium plate and the atlantoaxial,in order to verify the feasibility of this fixation system for clinical applications.Results Three Dimension CT Reconstruction and DR about atlantoaxial specimens which were simulated anterior atlantoaxial transarticular anatomic locking titanium plate screw fixiation were applied postoperatively.There were the postoperative examination results which suggested that the titanium plate and atlantoaxial surface were matching,without exceeding the edge.All the screws were within the bone,wihout any injuries of vertebral artery,spinal cord,and atlanto-occipital joint.All the screw channel parameters were in line with normal distribution.There was no statistically significant difference(P>0.05) according to the paired t-test which was applied in the left and right screw channel parameters.Both the left and the right sides of the screw channel parameters were applied group merger to get the results that the angle of the atlantoaxial transarticular screw trajectory was (23.22±1.71)°lateral angulation in coronal plane and (27.96±3.05)°posterior angulation in sagittal plane,the length was (27.50±1.55)mm,the angle of atlantoaxial screw trajectory was (9.55±0.80)°nner angulation in horizontal plane and (25.35±2.36)°upper angulation in sagittal plane,the length was (15.47±0.89)mm.The shortest distance between atlantoaxial transarticular screw and vertebral artery,spinal cord was in horizontal plane A(the upper edge of the transverse foramen of atlas),with interval of (5.05±1.04)mm and (8.05±0.92)mm respectively;with an interval of (3.15±0.67)mm between atlantoaxial transarticular screw and the upper articular surface of the lateral mass of atlas.The distance between atlantoaxial transarticular screw and vertebral artery,spinal cord was (5.45±1.01)mm and (8.05±1.06)mm respectively in horizontal plane B(the lower edge of the transverse foramen of atlas),was (9.55±1.33)mm and (10.55±1.03)mm respectively in horizontal plane C(the lower edge of atlantoaxial upper articular surface).Conclution Postoperative image of surgical model showed that there was match between anterior atlantoaxial transarticular anatomic locking titanium plate screw fixiation system and atlantoaxial complex which demonstrated that the technique of anterior atlantoaxial transarticular anatomic locking titanium plate screw fixiation system in atlantoaxial fixation was safe and feasible. |
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