The Analysis Of The Effect Of Adjacent Vertebral Disease After Posterior Lumbar Interbody Fusion With Fixed Nail Rod System Parameters

Objective To investigate the effect of fixation parameters of screw system on secondary operation of adjacent vertebral disease after posterior lumbar fusion.Methods A retrospective analysis was performed on 26 patients with reoperation for adjacent vertebral disease after posterior lumbar fusion in General Hospital of Ningxia Medical University and Guolong Hospital,including 16 patients with single level,10 patients with double level,8 males and 18 females.The mean age of initial surgery was 66.38 years(62.00-69.75)years,and the follow-up was 14-59 months.Anteroposterior and lateral lumbar radiographs were obtained before the second operation,and the fixation parameters of the screw rod system were measured:(1)pedicle screw length and insertion depth: screw length was obtained from the surgical record sheet,and the insertion depth was the ratio of the length from the posterior edge of the vertebral body to the length of the vertebral body(represented by %);(2)Screw placement Angle: the Angle between the long axis of the screw and the endplate of the vertebral body;(3)nail rod Angle:the Angle between the screw and the connecting rod;(4)radian of connecting rod:Angle of bending of connecting rod;(5)length of connecting rod;Distance from the top of connecting rod to the end of connecting rod;(6)The type of pedicle screw(unidirectional or universal)and diameter were checked by surgical records.52 patients with the same age,same gender,same fusion segment and no adjacent vertebral disease were selected as the control group according to the 1:2 pairing condition.Lumbar anteroposteric and lateral radiographs with the same follow-up time as the patients undergoing the second operation were obtained,and the parameters of the screw system were measured.Finally,data were analyzed by Ttest,Chi-square test and Mann-Whitney U test to compare whether there were differences between the two groups,and conclusions were drawn by conditional Logistic regression analysis.Results 1.Single factor analysis was performed on 7 factors of general data and screw/rod parameters in a single level.After single factor analysis,there were statistical differences in screw Angle and connecting rod length,and it was considered that screw Angle and connecting rod length had an impact on the incidence of adjacent segment disease;Univariate analysis was performed on the general data and 7 factors of screw-rod parameters in the two segments.After analysis,there were statistically significant differences in screw depth and screw Angle.It is believed that the depth and Angle of screw insertion have an impact on the incidence of adjacent segment disease.2.Conditional Logistic regression analysis was performed on all the indicators,including 7 factors such as screw Angle,screw depth,screw rod Angle,screw diameter,screw length,connecting rod radian and connecting rod length in single level and double level,respectively.After conditional Logistic regression analysis,it was concluded that: There were significant differences in the Angle of screw insertion and the length of connecting rod in a single level.It is considered that the Angle of screw insertion and the length of connecting rod in a single level are independent risk factors for adjacent segment disease.There were significant differences in screw depth and screw rod Angle between the two levels.The screw depth and screw rod Angle in the two levels were considered to be independent risk factors for adjacent segment disease.Conclusion The occurrence of adjacent segment disease after posterior lumbar interbody fusion is closely related to some parameters of scree-rod system.The screw Angle and rod length are independent risk factors for reoperation in single-level posterior lumbar fusion.Screw depth and screw-rod Angle are independent risk factors for reoperation in two-level posterior lumbar fusion.