Biomechanical Study On Atlantoaxial Pedical Screw-Rod And Crosslink Compression For Instability Jefferson Fracture

Objective: In order to provide the mechanical evidence of atlant- oaxial pedical screw-rod and crosslink compression for instable Jefferson fracture ,we had evaluated the stability of atlantoaxial junction fixation by atlantoaxial pedical screw-rod and crosslink system.Methods: After gross observation and X-radiography confirmation of the specimen's integrity and no osseons abnormal,six adult wet-cadvaveric spinal(Occiput-C4)specimens were used to test the biomechanical stability.The specimens were tested intact ,after instable Jefferson fracture and transverse ligament section,and after stabilization fellow the two techniques: atlantoaxial pedical screw-rod system,atlantoaxial pedical screw-rod and crosslink.The three dimensi- onal movements of C1-C2 were recorded though photogrametry with a pure moment of 1.53 Nm.The range of motion (ROM) of each specimens in two fixations was caculated. Statistical analysis was performed with one -way analysis of variance,Fish's least significant difference test to evaluat the immediate stability of the fixation with the two methods.Results: In flexion-extension,lateral bending and axial torsion the ROM increased significantly after the specimens were injured as compared with intact spines (p<0.05).After stabilization,the ROM were significantly lower than in injured and intact spines in all mo-tion.Among the 2 instrumented techniques,the ROM for the atlantoaxial pedical screw-rod and crosslink lower than atlantoaxial pedical screw-rod system in flecion-extension and lateral bending (P>0.05).In axial torsion , the atlantoaxial pedical screw-rod and crosslink significantly lower than atlantoaxial pedical screw-rod system (P<0.05).Conclusions: According to the biomechanical testing , atlantoaxial pedical screw-rod system and atlantoaxial pedical screw-rod and crosslink system fixation on atlantoaxial instability provide excellent postoperative stability.However, atlantoaxial pedical screw-rod and crosslink system fixation mide better fixation than atlantoaxial pedical screw-rod system in axial torsion.