Biomechanical Effects Of Intervertebral Space Distraction Height On Adjacent Segments In Cervical Anterior Fusion

Objective 1.The purpose of this study was to explore the significance of choosing proper height of intervertebral distraction by measuring the pressure of adjacent intervertebral discs and articular processes,and range of motion of cervical vertebrae with different C5/6 intervertebral space distraction height.2.To retrospectively analyze the imaging parameters of the adjacent intervertebral space height,cervical curvature and adjacent segment stability and the improvement of clinical spinal nerve function under different distraction heights of cervical anterior cervical fusion,and analyze the cervical anterior approach.The effect of different intervertebral opening heights on the imaging and clinical outcomes of adjacent segments.Methods 1.Cervical vertebrae were taken from 6 fresh adult cadavers to prepare models.The models prepared were placed on a BOSE dynamic/static material testing machine,and multi-dimensional movements of standing upright,flexion and extension,side bending,and rotating were applied.Changes in C4/5 and C6/7 intervertebral disc pressure,articular process pressure,and range of motion of cervical vertebrae before thedistraction of C5/6 intervertebral space and after distraction at benchmark heights of 100%,120%,140%,and 160% were tested under different exercise loads.2.From 2013 to 2016,87 cases of cervical anterior cervical interbody fusion were performed in the anterior cervical vertebrae.There were 48 males and 39 females,aged 45 to 71 years old,C4/5: 18 cases,C5./6: 47 cases,C6/7: 22 cases.All patients underwent anterior cervical discectomy and spinal nerve decompression.All cases were treated with autogenous iliac bone for bone grafting and titanium plate fixation.Preoperative and postoperative cervical anterior lateral radiographs and functional X-ray films were collected to measure the height of the intervertebral space distraction 1 week after surgery,and the cervical spine X-ray intervertebral space distraction height was grouped 1 week after operation.: Group A: the height of the distraction is 100%-110%(21 cases);the height of the group B is 110%-130%(43 cases);the height of the group C is more than 130%(25 cases);In the first week,2years,at the last follow-up,the imaging parameters of the adjacent segmental intervertebral space height,cervical kyphosis angle,and adjacent segment stability,and the improvement of clinical spinal cord function,neurological spinal cord function improvement using cervical spine JOA score,VAS score The NDI index was evaluated to analyze the effect of different scapular heights of the anterior cervical fusion on the degeneration of adjacent segments.The correlation between different intervertebral space distraction heights wasanalyzed.Results 1.First,the pressure of the adjacent intervertebral discs was highest with standing upright position among various positions before distraction,the pressure of the adjacent intervertebral discs varied with different positions of the specimens and different distraction heights after distraction,and the pressure of the adjacent intervertebral discs at a distraction height of 120% was closest to that before distraction(P<0.05).Further,the pressure of the adjacent articular processes was highest with left and right rotation among different positions before distraction,while the pressure of the adjacent articular processes varied with different positions of the specimens and different distraction heights after distraction,and the pressure of the adjacent intervertebral discs under the same exercise load with different positions at a distraction height of 120% was lower than that at other distraction heights(P<0.05).Finally,the range of motion of cervical vertebrae was largest without distraction,the range of motion of the intervertebral discs was largest at a distraction height of 120% after distraction(P<0.05).2.The shortest follow-up time was 2 years in 87 cases and the longest follow-up time was 5 years.Postoperative height loss of adjacent segmental intervertebral space: group A was the least,group C was the most;postoperative cervical lordosis angle group B was the closest to normal cervical curvature;the last follow-up period was the incidence of adjacent segment instability is the highest in group C.After thepostoperative JOA score,the improvement rate of group B was the highest.The NDI index changes regularly with the neck pain VAS score.Conclusions 1.When removing the C5/6 intervertebral disc and implanting an intervertebral bone graft,a benchmark height of 120% as the intervertebral space distraction height had little influence on the change of pressure of adjacent intervertebral discs and articular processes and range of motion of cervical vertebrae,and is therefore an appropriate intervertebral space distraction height.2.After cervical anterior interbody fusion,the improvement of clinical symptoms is most obvious when the height of intervertebral space is about 120%.When the height of intervertebral space is more than 140%,the height of intervertebral space is obviously lost in adjacent segments.The incidence of instability in the segment increased.Choosing about 120% of the opening height can obtain better clinical efficacy,and the effect on adjacent segment degeneration is relatively small.