The Study Of Craniovertebral Junction Fixation With Transarticular Screws

This study is designed to find a new and more ideal internal fixation technique for clinical occipitocervical arthrodesis. By a series of studies, we attempt to achieve the following goals:1. Provide anatomic parameters of the occipitoatlantoaxial complex for clinical, scientific and Chinese constitution investigations so as to provide anatomic clues for and confirm feasibility of posterior occipitoatlantoaxial transarticular screw fixation.2. Explicit the entry point, ideal angle of insertion, and allowable range and length of the trajectory in posterior atlanto-occipital transarticular screw fixation; discuss the indication, complication and procedure of craniovertebral junction fixation with transarticular screws.3. Evaluate stability of biomechanics of occipitoatlantoaxial reconstruction with transarticular screw fixation and compare the outcome with that of the clinical conventional methods of craniovertebral junction fixation.4. Compare the extracting stress of four craniovertibral screws bearing biological load under the condition of three-dimensional motion in six directions and evaluation biomechanical properties in their respective biological settings.Materials and Methods1. Anatomic data that are clinically significant were obtained by measuring the dried occipital condyle and atlas specimens from 100 normal Chinese adult cadavers, and anatomic observation was conducted of the lateral masses and posterior arch of atlas from 12 fresh human cadaveric occipitocervical spine specimens.2. Posterior occipitoatlantoaxial transarticular K-wire implantation was performed under visual control on 20 dried bony specimens that contained complete atlanto-occipital articulations, and cephalocaudal and lateral views were X-rayed, on which an angle and length of the screw trajectory were measured. The atlanto-occipital articulations of 30 normal adult Chinese were three-dimensionally reconstructed by CT, on which the adjustable range of allowable angle of the posterior atlanto-occipital transarticular screw trajectory were measured. Posterioratlanto-occipital transarticular screw fixation was performed on 12 fresh craniovertebral junction specimens, and P-A and lateral views were X-rayed and the three dimensions were reconstructed by CT postoperatively.3. Using a spine three-dimensional motion tester, motor parameters of the Oc-Cl and C1-C2 segments were tested on 12 fresh human cadaveric occipitocervical spine specimens under seven different conditions: the intact specimen group (Intact group), the occipitoatlantoaxial instability group (Destabilized group), the craniovertebral junction fixation with Ti-cable and bone graft group (Cable+Graf group), the transarticular fixation group (CIS group), the fixation with SUMMIT occitocervical spinal fixation system group (SUMMIT group), the fixation with transarticular screw and bone graft group (CTS+Graf group), and the fixation with SMMIT system and bone graft group (SUMMIT+Graf group). The data obtained were statistically analyzed.4. Posterior transarticular fixation and SUMMIT occipitocervical fixation were performed in succession on 12 fresh craniovertebral junction specimens (containing Oc-C3). Using the strain electronic measure, the extracting stress was measured of Oc-Cl transarticular screws(Oc-Cl TA group), C1-C2 transarticular screws(Cl-C2 TA group), C2 isthmicm screws(C2 IS group) and occipital screws(Oc Screw group) that were bearing biological load under the condition of three-dimensional motion in six directions. The results were statistically analyzed.Results1. The occipital condyle and the superior articular facet of atlas bit to form the atlanto-occipital articulation, where the articular face of the occipital condyle was inside oblique and there was great variation in morphology of the hypoglossal canal. The distance between the articular face of occipital condyle and the hypoglossal cannal was 9.66+1.13 (6.80-13.32)mm; the distance of the angle of the two occipital condyle...