The Establishment For In Vitro Experimental Model Of The Lower Cervical Bilateral Facet Dislocation

Study Design:To establish an In Vitro experimental model of the lower cervical bilateral facet dislocation.Background:To determine the mechanism of the lower cervical bilateral facet dislocation and the biomechanics characteristic of the dislocated cervical vertebra with normal physiological condition.An In Vitro experimental model of the lower cervical bilateral facet dislocation which was more consistent with the normal physiological condition has been established according to the radiology measurement of the angle of declination on the chinese lower cervical facet joints and the previous biomechanical models of the lower cervical vertebra.Method:This study was divided into three parts.Part one:radiology measurement.In order to get more rational data for designing an In Vitro experimental model of the lower cervical bilateral facet dislocation,100 cases of normal persons were included in this part and 500 angles of declination on the lower cervical facet joints(C3～C7) of these cases included were obtained by use of radiology measurement and statistically analyzed.Part two:the design of the experimental facility for an In Vitro experimental model of the lower cervical bilateral facet dislocation.On base of radiology measurement and literatures related,the shape of the experimental facility was designed.The material and functional characteristic of the experimental facility were also described.Part three:6 fiesh-frozen human osteoligamentous cervical spine specimens(C3～T1) were used to establish In Vitro experimental models of C4/5 bilateral facet dislocation and biomechanical study had been made at the same time.Results:The 500 angles of declination on the lower cervical facet joints(C3～C7) were normal distribution,the population mean was 57.302°and the median was 56.9°;there was no obviously statistical significance between the angles of declination on C4 and C6 by one-factor analysis of variance and SNK-q test(P=0.168) and it is indicated that the angle of C4 is equal to that of C6.With the comparation of C4,C6 and C3,C5,C7,there are obviously statistical significance by SNK-q test(P＜0.05).The order of the angles of declination on the lower cervical facet joints(C3～C7) is C7＞C3＞C_4,6＞C5,C4=C6 and the the median(56.9°) can objectively represent the collected characteristic of the lower cervical facet joints(C3～C7).With muscle force replication of the cervical spine,bilateral facet dislocation of the lower cervical spine can be made by exerting shearing force to specimens.The injury mechanism of the lower cervical bilateral facet dislocation can be concluded as follow: firstly the supraspinal ligaments,interspinal ligaments,ligamenta flava,articular capsule and annulus fibrosus may been ruptured by the shearing force,then the facet jionts of the injured segment been dislocated;Secondly with the strong contraction force of the cervical muscle,the dislocated articular process can been kept interlocking.It is indicated that cervical muscle force is very important to keep stability for the cervical vertebrae and the dislocated articular process can not been kept interlocking without cervical muscle force.Conclusion:An In Vitro experimental model of the lower cervical bilateral facet dislocation with normal physiological condition had been established.With the help of the In Vitro experimental model,the mechanism of the lower cervical bilateral facet dislocation and the biomechanics characteristic of the dislocated cervical vertebra can be understanded more clearly and it also can fine to guide the diagnoses and therapy principles for the patients with lower cervical bilateral facet dislocation.