The Anatomical Study Of Anterior Occiput To Axis Transarticular Screw Fixation By Locking Plate

The occipitoatlantoaxial complex located in the vital center of the body, with unique and complex anatomical structure and function. Variety of congenital or acquired factors that cause local bone and ligament structure of the destruction caused occipitocervical instability, leading to the medulla oblongata or spinal cord compression levy.That often potentially dangerous and it needs occipitocervical fusion and internal fixation.The occipitoatlantoaxial complex (Atlas, axis and occipital condyles) connects the cranial and vertebra, the anatomical location of which is deep and complex. It is situated next to the medulla oblongata, spinal cord, vertebral artery, throat, trachea, esophagus, cervical vessels and the superior laryngeal nerve, hypoglossal nerve closely, as the hazardous area of the surgery. Only a few large hospitals carry out surgery in the area. In case posterior surgery carrys out difficultly or impossiblely, anterior surgery is an ideal choice. Now anterior transarticular screw fixation from axis to occiput is just case report.However, the mechanical properties of the internal fixation was not excellent,and it is not easy to grasp and require high axial front side of the bone structure. It has not been largely applied in clinical practice. In view of this, our department developed a own set of new internal fixation system:the Anterior occiput to axis transarticular screw fixation by locking plate.This study was designed to examine the clinical anatomy of the anterior occiput to axis transarticular screw fixation by locking plate, and design looking anatomical plate and installation tools for Chinese populations.The purposes of this study are to investigate the feasibility and safety of anterior transarticular screw fixation from axis to occiput. The thesis has contributed to provide a feasible solution for occipito-cervial instability and develop a new kind of internal fixation technique and instrument with independent knowledge right. It promises to improve the cognition and treatment achievement ratio about this disease,alleviate the sufferings of the patient and show great military and social effect.Research Objectives1、The correlated anatomic linear and the screw rajectory parameters of anterior transarticular screw fixation from the axis to the occiput were observed and measured to investigate the feasibility and explore the anatomical basis for clinical applications of occipitocervical fusion by anterior transarticular screw fixation from the axis to the occiput.2、The screw rajectory parameters and the distance between the path and the Vertebral Artery were measured to investigate the safety of anterior transarticular screw fixation from axis to occiput3、The correlated anatomic linear and the screw rajectory parameters of anterior transarticular screw fixation from the axis to the occiput were measured to provide the anatomic data for design of internal fixation system.4、Simulated operations were conducted to test the feasibility and safety of anterior transarticular screw fixation from axis to occiput and provide experimental evidence for clincal application.. Part one The anatomical measurement of adult human bone specimens from the axis to the occiputObjective The correlated anatomic linear and the screw rajectory parameters of anterior transarticular screw fixation from the axis to the occiput were observed and measured to investigate the feasibility and explore the anatomical basis for clinical applications of occipitocervical fusion by anterior transarticular screw fixation from the axis to the occiput.Method The correlated anatomic linear and the screw rajectory parameters of anterior transarticular screw fixation from the axis to the occiput were observed and measured on thirty adult human bone specimens.According to the data measured,such as:anteroposterior diameter and transverse diameter of occipital condyle articular facet, the thickness Of the posterior third margin of the occipital condyle, anteroposterior diameter and transverse diameter of the atlas uparticular facet, the thickness of inner margin and the thickness of outer margin of massa lateralis atlantis,anteroposterior diameter and transverse diameter of the axis uparticular facet,vertical diameter and transverse diameter of the axis anterior surface,the maximum,minimum and ideally camber angle, the maximum, minimum and ideally caster angle,Results The morphologic and anatomical characteristics of adult human bone specimens from the axis to the occiput:(1) axis of anterior arch of the lower edge of the atlantoaxial vertebral side edge of the junction points above about4mm at a constant bone depression, a clear sign of bone;(2) The hypoglossal canal is located in the side of the articular surface of the occipital condyle bone pipeline, the pipeline outside the top go forward from the inside line.2/3of the hypoglossal canal is located in the occipital condyle in51cases (85%),1/3of the occipital condyle in9cases (15%);(3) lateral mass of atlas was outside the thick thin wedge of the atlas the lateral mass of the outer edge height around edge height of the lateral mass of atlas on the articular surface of the central narrow, was kidney-shaped concave inner edge under the articular surface than on the inner edge of the articular surface closer to the sagittal plane;(4) occipital convex condyle appear before the scaphoid, the Central than the trailing edge thickness, one cases of occipital condyle showed a dumbbell-shaped (1.67%); a condylar fossa behind most of the specimens occipital condyle, there was47cases (78.33%);(5) front surface of the atlantoaxial vertebral Central as a "nose" protruding; the lower edge of the formation of the "tongue"(6) atlantoaxial vertebral before, prominent, and the vertebral body under the surface of the fornix-like. The ideally placed angle of the screw is directe18.75±1.70degrees laterally in the coronal plane and24.40±2.11degrees posteriorly in the sagittal plane. The mean length Of the screw trajectory was (34.45±1.95) mm.Conclusion From the anatomical standpoint,The technique of anterior fixation from the atlas to the occiput is feasible.Part two CTA osteometry of the anterior occiput to axis transarticular screw fixation by locking plate and its clinical relevanceObjective The screw rajectory parameters and the distance between the path and the Vertebral Artery were measured on CTA imaging data to investigate the safety of anterior transarticular screw fixation from axis to occiput.Material:The cranio-cervical CTA images in30patients were studied retrospectively,,18were male,and12were female. aged from21to55years(average33.6±4.2years old); Inclusive criteria:aged from20to60years, the CTA scanning sections are from October lth,2010to April lth,2011.Exclusive criteria:developmental deformity or anatomical variations, bone destruction (including tumour, inflammation,and fracture), cervical spondylosis history, prior cervical vertebra operation.Method Thirty health cases were selected from the date of head-neck CTA examination randomly. The angle and length of screw trajectory were measured by Vitreal software. So it is with the intervals between the vertebral artery and the screw trajectory.Results There were five vertebral artery physiologic bendings between the entrance point plane and the anchor point plane. The distance between bilateral vertebral artery was (25.59±1.04)mm in the entrance point plane.The shortest distance between the vertebral artery and the screw trajectory lied in the topmost point of the vertebral artery groove of the axial on CT images, and the interval was (3.6±0.71)mm. The ideally trajectory in anterior transarticular screw fixation from axis to occiput:the space between the two entry points of screws was15.25±0.94mm,the ideally placed angle of the screw is directe18.75±1.70degrees laterally in the coronal plane and24.40±2.11degrees posteriorly in the sagittal plane, the mean length Of the screw trajectory was (35.95±2.16) mm. the ideally trajectory of fixation screw on axis body:the space between the two entry points of screws was9.21±0.72mm,the ideally placed angle of the screw is directe13.89±0.87degrees laterally in the coronal plane and17.21±1.14degrees upper tilting in the sagittal plane.Conclusion From the anatomical standpoint,The technique of anterior transarticular screw fixation from axis to occiput for normal Chines is feasible and There was a certain safe distance between the vertebral artery and the screw trajectory;but there are some directions for implantating the screws. There was a good distance between the vertebral artery and the screw trajectory, but the trajectory directions need rigorous controls. Application of CTA may provide an excellent route for pre surgical individualized design.The correlated anatomic linear and the screw rajectory parameters of anterior transarticular screw fixation from the axis to the occiput were measured to avoid the injury of Vertebral Artery and improve the safety.Part three Simulated operations of the anterior occiput to axis transarticular screw fixation.Objective Simulated operations were conducted to test the feasibility and safety of anterior transarticular screw fixation from axis to occiput and provide experimental evidence for clincal application.Method CT scan and3D reconstruction were performed in specimens from occiput to axis for pre surgical individualized design. On these bases, simulated operations were conducted.The first step is to exposure the bone sign, then ensure entry points of screws and ideally anchor points.1.0mm Kirschner wires were applied to the ideal screw trajectory angle measured in the preoperative external guide auxiliary out, after the top of the drill into the edge into the pin side perspective, the entire operation in the C-arm X-ray fluoroscopy monitoring2.7mm hollow drill along the Kirschner wire drilled into perspective see Kirschner direction, length satisfaction, in order to enter the occipital condyle through the atlantoaxial joint and the atlanto-occipital joint to stop the top of the cortex of the occipital condyle. Sounding and select the appropriate length of4.0mmAO titanium hollow screw into..Roentgen rays were examined,and three-dimensional CT was reconstructed postoperatively to study the positions of screws.Results Imageological examination and direct vision demonstrated that anterior occiput to axis screw fixation according the above results ensured insertion of the trajectory passing through the atlanto-occipital articulation and the atlanto-axial articulation without piercing the bones. Imageological examination demonstrated that the angle and the length were within the reference range.Conclusion From the anatomical standpoint,The technique of anterior transarticular screw fixation from axis to occiput for normal Chines is feasible.But it requires the path to have high accuracy. To elevate the security,recovering their normal anatomical position is the important precondition of the application...