Research On The Treatment Of Unstable Jefferson Fractures With JeRP

ObjectiveAtlas is the most important part of occipital-atlanto- axial complex,it has much influence on the stability of upper cervical vertebrae.Once unstable Jefferson fractures, which are included in atlas fractures,result in injury of the upper cervical spinal cord, the consequence would be serious.While most authors agree with the conservative treatment of stable Jefferson fractures,the discussion about surgical or nonsurgical treatment of isolated or combined unstable atlas burst fractures remains a matter of controversy.The current therapy includes immobilization with halo vest, atlanto-occipital fusion and atlanto- axial fusion.From our view,halo vest extension and extemal immobilization by a rigid collar are often insufficient to achieve a satisfactory and permanent repositioning of the displaced lateral masses of the atlas. The risk of fixing the dislocation during long-term immobilization can lead to irreversible incongruence of the atlantooccipital and atlanto- axial joints,followed by arthrosis and increasing neck pain.The serious disadvantage of these fusion techniques is the elimination of the important rotation mobility of C1-C2.The range of motion is reduced,and the incidence of degeneration of the lower cervical spine may be increased.To reduce unstable Jefferson fractures anatomically and preserve the activity of upper-cervical vertebra,Yin Qing-shui design JeRP(Jefferson-fracture reduction plate) fixation system.In this research we evaluated applied anatomy,biomechanical characteristics and clinical application of JeRP for treatment of unstable Jefferson fractures with a view to offering evidence for widespread clinical treatment.Research1.A total of 60 atlas(C1) vertebrae for a total of 120 lateral masses were examined and external measurements obtained to assess the feasibility of placing JeRP in the lateral mass;2.Simulated unstable Jefferson fractures and JeRP internal fixation operation on 6 fresh cadaveric upper cervical spines to evaluate biomechanical characteristics of JeRP;3.Observe the clinical efficacy of JeRP fixation for treatment of unstable Jefferson fractures.Materials and Methods1.A total of 60 atlas specimens were studied,for a total of 120 lateral masses evaluated,with skeletal age ranging from 17 to 45 years,average 29 years.The following dimensions of the atlas were measured with an electronic digital caliper (accuracy 0.01 mm):The lateral mass anteroposterior dimension superior to the posterior ring insertion(LMAPsup);the distance between lateral mass entry site and anterior tubercle(AO);the distance between two lateral mass entry sites(AA');the minimum diameter of the anterior arch(MD);the minimum lateral mass anteroposterior dimension in sagittal orientation(LMAPmin).So we got external measurements of 120 lateral masses,which were 120 LMAPsup values,120 LMAPmin values,120 MD values,120 AO values and 60 AA' values.All the data was calculated by SPSS 13.0 programme,which was supplied by department of Southern Medical University,and we got 5 series of maximum,minimum,mean and standard deviation.2.A total of 6 cadaveric upper cervical spines,were studied in this trial.All the specimens were obtained form fresh cadavers,which include 4 males and 2 females, with age ranging from 11 to 30 years,average 21 years and without cervical disease or injury.All the specimens were made into fracture models of bilateral anterior arch fracture of atlas,which is one type of unstable Jefferson fractures,and then fixed with JeRP.The ranges of motion(ROM) of C1-3 in 3 statuses were measured by the analysis system of three-dimensional spinal motions one by one,and then we got the neutral zones and ROMs of every dimension in every status.Then the data was analyzed by SPSS 13.0 programme,which was supplied by the statistics department of Southern Medical University,and the statistics model was Repeated Measures.We analysed the main effects and interact effect of the two factors and we copared the simple effect via One-Way ANOVA.We used Bonferroni method to compare the means of every group.The difference significant level was 0.05.In the end,we isolated atlases form those specimens and placed HA screws on the lateral masses.We measured the pull-out strength of screws via MTS858 Mini BioIli biomechanical machine.3.Observe the clinical efficacy of JeRP fixation for treatment of 7 unstable Jefferson fractures cases.We analyzed pre-operation symptoms,signs and radiographs and those of post-operation data.Results1.LMAPsup,LMAPmin,AO,AA' and MD were(20.60±1.84),(19.57±1.55),(18.68±1.89),(35.46±2.86) and(4.66±0.65)mm respectively;2.There is significant difference between neutral zones for flexion-extension of different status(F=18.980,P=0.000),there is significant difference between neutral zones for lateral bending of different status(F=17.745,P=0.001),and there is significant difference between neutral zones for axial torque of different status (F=105.502,P=0.000 ).There is significant difference between ROM for flexion-extension of different status(F=43.558,P=0.000 ),there is significant difference between ROM for lateral bending of different status(F=16.275,P=0.001), and there is significant difference between ROM for axial torque of different status (F=164.548,P=0.000).The neutral zones of fracture status was larger than the normal values(P＜0.05).There was statistically significant difference between the neutral zones and ROM of fixation status with those of normal status(P＞0.05).The measurement of screw pull-out strength was 412.74±51.81N,ranging from 323.49N to 493.30N.3.The average follow-up time was 12 months(range,8 months to 30 months).All patients were examined clinically and radiographically.Measurements were taken from anteroposterior(open mouth) and lateral radiographs,computed tomography scans, postoperative flexion-extension films,and rotation MRI.All the patients underwent JeRP internal fixation recovered well.The pharynx cut got primary healing and there were no complications related to the transoral approach.Conclusions1.LMAPsup measured in this study is feasible screw trajectory,which could prevent screws from penetrating the posterior cortex and injuring the vertebral artery. The incidence point of LMAPsup on the anterior aspect of lateral mass is feasible entry point for the screws,and we measured AO values to choose the entry point.In the same method,we could define the heterolateral entry point for the screws,defined as A'.AA' values could help us to choose the proper JeRP plate.And we measured the MD values to choose suitable screw.Because there is individual variation in crowd, those measurements above could just conduct as reference to guide clinical manipulation.2.After being made into Jefferson fracture model,the neutral zones of those specimens increased significantly,so those fractures were defined as unstable Jefferson fractures.There is no statistical difference between the neutral zones of those specimens after being fixed by JeRP and normal values,which proved that the stability of upper cervical spines had restored.There is no statistical difference between the ROMs of those specimens after being fixed by JeRP and normal values,which proved that JeRP fixation both restored the stability of upper cervical spines and reserve the ranges of motion.3.The JeRP fixation system,which was designed by Yin Qing-shui,could reduce unstable Jefferson fractures and fix at the same time.With the combination of JeRP and reductor,the reduction and fixation could be finished at once.The difference between JeRP fixation and other fixation is that it only fixes atlas.It is the only technique which could both restored the stability of upper cervical spines and reserve the ranges of motion.So it is a perfect choice for treatment of unstable Jefferson fractures.