Clinical Analysis Of Single-segment Fixation For Unstable Atlas Fractures And Development Of Posterior Atlantal Reduction Screw-rod System

Objective:1.To compare and analyze the clinical efficacy of transoral anterior JeRP single-segment fixation and posterior horizontal screw-rod(PSR)single-segment fixation in the treatment of unstable atlas fractures.2.To complete related anatomical measurements of atlas and design a posterior atlantal reduction screw-rod system.3.To apply finite element method to analyze the mechanical properties of the posterior atlantal reduction screw-rod system.4.To evaluate the three-dimensional biomechanical stability of the posterior atlantal reduction screw-rod system using in vitro specimen models.Methods:1.Twenty-two patients with unstable atlas fractures were treated by transoral anterior JeRP single-segment fixation(JeRP group)and 11 patients with unstable atlas fractures treated by PSR single-segment fixation(PSR group),and the clinical features of all patients were retrospectively analyzed.2.Anatomical measurements were performed on 50 atlas specimens and 80 atlas CT images,and a posterior atlantal reduction screw-rod(PARSR)system was designed.3.The three-dimensional finite element model of normal upper cervical spine was constructed and verified,and then the three-dimensional finite element models of unstable atlas fracture,PSR fixation,anterior JeRP fixation and PARSR system fixation were constructed,and the ROM of C1-C2 segment,stress and displacement of each model under various loads were analyzed.4.The unstable atlas fracture model,PSR fixation model,anterior JeRP fixation model,and PARSR system fixation model were established using 6 fresh craniocervical specimens to test C1-C2 segment ROM in the each direction.Results:1.The operative time of JeRP group had no difference from it of PSR group(P>0.05),but the blood loss in JeRP group was lower than that in PSR group(P<0.05).The length of hospital stay in the PSR group was shorter than that in the JeRP group(P<0.05).The visual analogue scale scores and Neck Disability Index of the two groups after surgery and at the last follow-up decreased significantly,comparing to those before surgery(P<0.05),and there was no difference between two groups(P<0.05).Postoperative distance of anterior arch fracture and Lateral Mass Displacement in both groups was significantly lower than PSR group(P<0.05).The distance of posterior arch fracture and R-J distances(the vertical distance from the midpoint of the lower margin of the axis to the McGregor line)of the JeRP group after operation was greater than that in PSR group(P<0.05).Two groups had similar incidence of postoperative complications(P>0.05).Compared with The fracture fusion rate of the PSR group,it was higher in the JeRP group at 3 months after opration(P<0.05),but two groups had similar fracture fusion rate at 6 months postoperatively(P>0.05).2.There was no difference between related anatomical data of atlas specimens and CT images(P>0.05),and based on which a posterior atlantal reduction screw-rod(PARSR)system with a reduction mechanism was designed.3.The C1-C2 segment ROM of PARSR system fixation model under various loading conditions was significantly smaller than that of Fracture model,and was comparable to PSR and JeRP.The internal fixation stress of PARSR system fixation was larger in the extension condition,while the stress of vertebral body and displacement in other conditions were larger.4.There was no difference in the C1-C2 segment ROM of PSR group,JeRP group or PARSR group(P>0.05),but they were significantly smaller than that of the Fracture group(P<0.05),and had no difference from the Intact group(P>0.05).Conclusions:1.Both transoral anterior JeRP and PSR single-segment fixation have good clinical efficacy in the treatment of unstable atlas fractures,but the effect of fracture reduction of PSR fixation is worse.2.The PARSR system designed based on anatomical data conforms to the anatomical characteristics of posterior part of atlas and has a better fracture reduction mechanism.3.The PARSR system has reliable mechanical stability and firmness.4.The PARSR system has good three-dimensional biomechanical stability.