Screw stress distribution of different fixation techniques following cervical laminectomy in lower cervical spine

English Keywords:Lower cervical spine  Laminectomy  Finite element model  Fixation  Stress distribution

English Abstract:

  【Abstract】 Objective：To investigate the screw stress distribution of different fixation techniques following cervical laminectomy in lower cervical spine.Method：CT scans were performed on a healthy adult male volunteer.Mimics 10.01，Geomagic studio 10.0，HyperMesh 10.0 and Abaqus 6.9.1 softwares were used to establish the intact model（C3-C7）.The model was subjected to three-level laminectomy and then reconstructed by different fixation protocols：pedicle screw fixation（PSF） and transarticular screw fixation（TSF）.The skull load of 75N and torsion preload of 1.0Nm was added on the models，which simulate flexion，extension，lateral bending and rotation.The stress distribution were analyzed while the skull was under flexion，extension，lateral bending and rotation conditions.Result：The intact finite element model showed good geometric similarity，which consisted of 61464 elements and 16588 nodes.Compared with the published data，the intact model was validated.Base on the intact model，the models following laminectomy and then reconstructed either by PSF or TSF were established.Under simulated physiological movements，the screw inserted by PSF had higher stress bearing at the connection between screw and rod with the maximal stress levels of less than 160MPa，while screws inserted by TSF had higher stress bearing at the middle part with the maximal stress levels of over 2800MPa.Conclusion：Base on the CT scans，finite element model of lower cervical spine can simulate the conditions of natural state，after laminectomy and after reconstruction breakage under different fixation techniques.Compared with PSF techniques，TSF has a higher risk of screw.