Application Of Distraction Before Discectomy In Anterior Cervical Surgery

Objective:To observe the effect of distraction before discectomy(DBD)in the distraction of the height of anterior cervical space and to explore its feasibility in restricting over distraction.Methods:A total of 31 patients with cervical spondylotic myelopathy were treated with anterior cervical discectomy and fusion(ACDF).During surgery,the intervertebral space was distracted before discectomy:when exposed to anterior of the cervical vertebral column,make sure that the segment is right using fluoroscopy.Distraction was performed only once when the anterior longitudinal ligment was kept perfectly intact.During distraction,when the surgeon felt that the force used to distract the Caspar ratchet to the next level increased intensively,stop distracting and use this standard as the finishing point of distraction.Before surgery,the distance from the arch top of inferior endplate of upper vertebrae of the index level to the midpoint of superior endplate of lower vertebrae was measured(H0).The same method was used to measure the adjacent proximal and distal intervertebral space heights(Hp and Hd),and the mean value of Hp and Hd,(H),was regarded as a referential height that the index intervertebral space should be restored.During operation,the intervertebral space heights before(H1)and after(H2)discectomy with application of DBD were measured with the aforementioned method.The pre-and post-operation index segment height AB and A’B’ were measured respectively.The change of index segment height was defined as△H(A’B’-AB),the index intervertebral space height after operation was defined as H3(H0+△H).Patients were all taken X rays beofe and after surgeries in supine position.Notice:patients lied down on the operation bed in supine position,after general anesthesia,through putting a soft and supportive roller behind the patient to extend cervical spine slightly.X ray was taken before surgery to measure the intervertebral height of the index level.When the surgery started,the position and the angle of the cervical spine extension were not changed any more.After surgery,the patient took X ray in supine position without wearing cervical collar.Before sugery,the X ray was taken by a movable C-arm in the operation room,while after surgery was taken in radiology department.Because the magnification ratio was different,we use a digital caliper to measure the real numerical value of the intervertebral height and then used the magnification ratio to calculate the real intervertebral height.During surgery,a 10 cents coin was attached to the posterior lateral cervical spine,before sugery,its diameter was measured by the digital caliper.When the coin was showed on the screen of the C-arm,it had another diameter value,so we could know the magnification ratio and with this ratio we could figure out the real value of the intervertebral height during sugery.Two residents were trained to use the same calibrated digital caliper to measure the intervertebral height before,during and after the surgery respectively.In order to acquire the most accurate value,use the averge mean of the two residents’ measured intervertebral height as the final value of the intervertebral height.The patients were divided into neck pain group and no neck pain group according to their post-operative neck pain VAS scores.SPSS 23.0 software was used to analyze statistics.H0、H1、H2、H、△H1、△H2、△H3 and △H were all examed with normal distribution test and all subjected to normal distribution,all the statistic data was showed by x±s.The difference adopted to t-test between the group while independent sample t-test within the group.P<0.05 was considered statisticaly different.Bland-Altman method was used make consistency analysis.x±2s was used as allowing rage and ratio-average scatter diagram was then made.Results:The post-operative neck pain incidence rate was 19.35%.During operation,after DBD,the intervertebral space height change △H1(H1-H0)=(1.19±0.51)mm.In no neck pain group,the difference between H,[(6.95±0.84)mm]and H[(6.98±0.70)mm]was not significant(P=0.80),the difference between H2[(7.31±0.90)mm]and Hi[(6.95±0.84)mm]was significant(P<0.01).In neck pain group,the difference between H2[(8.33±1.39)mm]and Hi[(7.87±1.35)mm]was significant(P<0.01).In neck pain group,△H=(3.04±0.42)mm,in no neck pain group,△H=(1,70±0.51)mm,the difference between two groups was significant(P<0.01).In no neck pain group,H1,H2 and H3 had good consistency with H.Conclusion:DBD can effectively control the distraction height of the index intervertebral space within 2 mm,also convenient to let the index intervertebral space be similar with adjacent segment and easy to follow.