The Biomechanical Analysis Of The Stability Of The Lower Cervical Spine By The Joint Capsule And The Joint Screw Fixation

Objective:Cervical in front of the vertebral body by intervertebral disc and anterior and posterior longitudinal ligament connected,in the rear of vertebral arch by facet joint,yellow ligament,interspinal spine ligament and the transverse ligament connected,these bone and joint ligament together constitute and maintain the physiological stability with physiological curvature of the cervical sequence.Lower cervical spine injury is a common injury in the neck,more common in the car accident and fall injury patients,lower cervical spine injury if involved facet joints,often lead to changes in the physiological stability of the cervical spine.When cervical spine subjected to violence on buckling or rotational violence accompanied by buckling or lateral flexion violence and violent strength too high over the facet joint capsule can withstand the maximum force strength,the joint capsule will rupture,and facet joints will dislocation.The general treatment methods of lower cervical spine injury associated with facet joint capsule rupture and facet joint dislocation are closed reduction and continuous traction treatment,pedicle screw,lateral mass screws and facet screws fixation.For the standard treatment and selection of internal fixation,there is no unified view of the domestic orthopedics physicians.There is no evident biomechanical theoretical proof to the effect of capsule integrity on the stability of lower cervical spine and the physiological stability of the lower cervical spine can be restored by the fixation of the facet screws alone.Our study aimed to assess the effect of the role of facet joint capsule on the stability of lower cervical spine and facet screw fixation on the goat specimen,which resected unilateral or bilateral facet joint capsule,by analyzing the data from the biomechanical experiments.Methods:1 16 cervical spines of fresh adult goats,which were collected within one hour after death.All specimens were retrieved and stored in the-200 C refrigerator.All specimens were taken out and thawed at the experimental day.Carefully remove the muscle and soft tissue without breaking the various ligaments.A small amount of soft tissue around the joints can be left to ensure the integrity of the joint capsule.Then cervical specimens were randomly divided into A,B two groups.The C2 and C7 of all the specimens were fixed with dental care powder.To the group A,the right joint capsule of C4 and C5 were completely resected without injuring joint;To the group B,the bilateral joint capsule of C4 and C5 were completely resected.All these were be done after the completion of the experiment of the complete cervical spine.Last all screws were inserted by high seniority orthopedic clinical doctor with the klekamp method.2 Lateral bending tests and vertical compression test were performed on the specimens.The load of bending tests were 80 N,and compression tests were 100 N.Loading speed was 5mm/min.The whole test process was always uniform loading,the load-displacement curve is recorded by a computer connected to the sensor.Each experiment was repeated 3 times to load / unload cycle,take the corresponding value,in order to reduce the impact of the viscoelastic effect of cervical specimens on the experimental results.The test order was:(1)Complete specimens;(2)unilateral joint capsule resection specimens;(3)unilateral facet screw fixation specimens;(4)bilateral joint capsule resection specimens;(5)bilateral joint facet screw fixed specimens.3 For statistical data analysis,including the(1)(2)(3)and(1)(4)(5)respectively by single factor analysis of variance.Result: There was an increase in the displacement of the five kinds of movement of unilateral joint capsule resection specimens when compared with complete specimens,but the difference was not statistically significant(P > 0.05).Under the same load unilateral facet screw fixation The displacement of the unilateral facet screw fixation specimens were decreased,but the difference was not statistically significant(P > 0.05).Under the same load,the displacement of the five kinds of the bilateral joint capsule resection group were significantly increased,and the difference was statistically significant(P<0.05).Compared with complete specimens,The displacement of the specimens with bilateral facet screw fixation in the posterior extension test was decreased,but the difference was not statistically significant(P>0.05).In other movement status,the difference of displacement was statistically significant(P < 0.05).Conclusion: The experimental study confirms that the facet joint capsules have an important role in maintaining the physiological stability of lower cervical spine.The cervical stability is significantly reduced when the bilateral facet joint capsules rupture,which needed treatment to restore the physiological stability.Transarticular screw fixation is a simple and reliable internal fixation.It can provide strong fixation to restore physiological stability of the lower cervical,which is an effective internal fixation methods for clinical treatment of lower cervical facet joint injury.