| Objective: According to the surface anatomy of the axis,the circular bucking bar is replaced by an anatomical bucking bar.Anatomical bucking bar is placed on the posterior pharyngeal wall in front of the axis during C2 pedicle screw placement to observe the damage of the soft tissue of the posterior pharyngeal wall by the pressure and time when the anatomical bucking bar maintains the stability of the vertebral body,and evaluate the safety of the anatomical bucking bar.Methods: According to the inclusion and exclusion criteria,posterior C2 pedicle screw fixation was performed in 31 patients with atlantoaxial instability between August2015 and December 2017.To record the time and the maximum pressure of pushing the posterior pharynx wall during the screw placement. According to C2 pedicle fracture,the patients were divided into C2 pedicle fracture group and non-C2 pedicle fracture group.Patients were divided into atlantoaxial fracture group and non fracture group according to whether there were atlantoaxial fractures.According to the results of laryngoscope,the patients were divided into the injured group and the non-injured group.The patients were divided into soft tissue thickening group and non-thickening group according to the width of soft tissue before and after the operation.The pressure and time in the process of drilling hole,wiring,tapping and screw placement were compared.Results: There were 6 patients with mild pharyngitis and the symptoms disappeared 3 days after operation.There were 5 patients with grade I mucosal injury and the symptoms disappeared 5-7 days after operation.None of them had dysphagia or infection.The pressure of each step during C2 pedicle screw placement was(4.1±0.8)N、(6.2±1.2)N、(5.2±0.7)N、(4.3±0.7)N,and the average pressure was(5.0±1.2)N.The time of each step during C2 pedicle screw placement was(21±1)s、(28±3)s、(26±1)s、(25±2)s,and the total time for one-side screw placement was(101±12)s,and the total time for bilateral screws placement was(202±23)s.The average pressure and time for C2 pedicle screw insertion in both C2 pedicle fracture group and non C2 pedicle fracture group were 5.3N/25 s and 4.8N/24 s respectively.The difference between the two groups was statistically significant(p<0.05).The pressure and time required during the wiring for the C2 pedicle fracture group were greater than that of the non C2 pedicle fracture.The difference between the two groups was statistically significant(p<0.05),indicating that the integrity of the C2 pedicle may be one of the reasons for the push and time required for the insertion of the needle.The average pressure and time for the bilateral C2 pedicle screw placement in the the atlantoaxial fracture group and non-atlantoaxial fracture group were5.1N/25 s and 4.5N/24 s respectively.The difference between the two groups was statistically significant(p<0.05).The pressure and time needed during the wiring for the atlantoaxial fracture group were greater than that of the non-atlantoaxial fracture group and the difference was statistically significant(p<0.05),indicating that the instability of C2 vertebral body caused by various fractures in the atlantoaxial region may increase the pressure and time of the screw placement.The average pressure and time for C2 pedicle screw insertion in both mucosa injury group and non-mucosa injury group were 5.6N/26 s and 4.9N/24 s respectively,and the difference between the two groups was statistically significant(p<0.05).The pressure and time needed during the wiring in the mucosa injury group were greater than that of the non-mucosa injury group,and the difference was statistically significant(p<0.05),indicating that the increased pressure and time during the wiring may be one of the factors causing mucosal injury.The average pressure and time for the bilateral C2 pedicle screw placement in the soft tissue thickening group and non thickening group were 5.3N/26 s and 4.9N/24 s respectively and the difference between the two groups was statistically significant(p<0.05).The pressure and time needed during the wiring in the soft tissue thickening group was greater than that in the non thickening group and the difference was statistically significant(p<0.05),indicating that the increased pressure and time during the wiring may be the main step to cause soft tissue swelling and injury.Conclusion: 1.The pressure and time of the anatomical bucking bar used in C2 pedicle screw placement each step were 4.1N/21s、6.2N/28s、5.2N/26s、4.3N/25 s,the average pressure of the unilateral screw placement and time was 5.0N/100 s,the average pressure and time of bilateral screw placement of 5.0N/200 s. 2.The increase of pressure and time in the wiring may be the main procedure for the injury of the posterior pharyngeal wall and the swelling of the soft tissue.3.The degree of fit between the anatomical rod and the anterior surface of the axis is obviously improved.It is a simple and safe method to assist posterior C2 pedicle screw placement. |
PDF Full Text Request