Analysis Of Anatomic Factors For The Subsidence Of Titanium Mesh Cage After Single Segment Anterior Cervical Corpectomy And Fusion (ACCF)

Objects:To figure out cervical anatomic factors for the subsidence of titanium mesh cage after single segment anterior cervical corpectomy and fusion(ACCF).Methods:The imaging data of 84 patients who suffered from Cervical spondylotic myelopathy and underwent single segment ACCF at the China-Japan Union Hospital of Jilin University from June 2016 to June 2019 was analyzed Retrospectively.According to lateral X-ray image of cervical spine from post-operation and the last follow-up,we divided all 84 patients into two groups: subsidence group and non-subsidence group through the criterion that the loss of height of fusion segment was > 3 mm anteriorly or posteriorly.Japanese Orthopaedic Association Scores was used to evaluate the surgical effect and correlation between cervical endplate inclination,cervical angle,cervical curvature and the subsidence of titanium mesh cage was also analyzed.Results:The subsidence of titanium mesh cage was observed in 32 of all 84 patients while other 52 patients is not.The rate of subsidence is 38.10%.There were significant differences in preoperative cervical curvature,fusion segment,and inferior endplate inclination angle of fusion segment between the two groups(P<0.05)whereas fusion angle and superior endplate inclination angle show no significant difference(P>0.05).Among those with the different cervical curvatures,the kyphotic group tend to have more risk of subsidence of titanium mesh cage with 11 of 17 patients(64.71%)witness the subsidence.Among those with the different fusion segments,C6 tend to have more risk of subsidence of titanium mesh cage with 13 of 20 patients(65.00%)witness the subsidence.Inferior endplate inclination increased with cervical segment,reached a maximum at C6,and decreased at C7 and as the inclination of the inferior endplate increases,the risk of subsidence of the titanium mesh also gradually increases.Significant difference was proved in postoperative JOA score and JOA score improvement rate(P < 0.05).The JOA score improvement rate in non-subsidence group(66.0% ± 13.3%)was significantly better than that in subsidence group(51.3% ± 12.6%).Conclusions:Subsidence of the titanium mesh in a single segment anterior cervical corpectomy and fusion has an impact on surgical effect.Those with cervical curvature kyphosis is prone to witness subsidence of the titanium mesh and segment of C6 shows highest risk of subsidence in C4-C7.Inferior plate inclination angle of fusion segment also relate to the subsidence.The risk is increased with angle and reaches a maximum at C6.