Analysis Of Risk Factors For Adjacent Segment Degeneration After Spinal Fusion Surgery

【Objective】The main purpose of this study is to analyze the risk position of Proximal junctional kyphosis(PJK)by using a finite element analysis model,and to focus on the effects of PJK and the risk factors of adjacent segmental degeneration(Adjacent segment disease,ASD),so as to provide guidance for the clinical and surgical treatment of adjacent vertebral disease and the correct functional exercise of postoperative patients Must refer to.【Methods】1.A patient with thoracolumbar congenital wedge vertebra with kyphosis who underwent posterior pedicle screw fixation anterior subtotal vertebral resection and reconstruction in the Third Affiliated Hospital of Guangzhou Medical University on March 2,2020 were selected as subjects,based on the thin slice CT scan data in the scope of osteotomy during the one-year follow-up.The interactive medical image control system Mimics 14.0 system and ANSYS 13.0 finite element analysis software were used to construct the finite element analysis model of thoracolumbar kyphosis.The biological stress in 5 regions,including anterior and posterior margins and left and right margins,of the upper fixed vertebra and upper disc under 7 working conditions,such as anterior flexion,posterior extension and left and right lateral flexion,was analyzed.2.Using the retrospective analysis method,39 patients who received three or more levels of lumbar fusion combined with pedicle screw fixation in the Third Hospital of Guangzhou Medical University from September 2018 to September 2020 were divided into PJK group and non PJK group according to the occurrence of PJK,and the risk factors of each group were statistically analyzed.3.A total of 59 patients who received fusion therapy in the Third Hospital of Guangzhou Medical University from September 2017 to September 2019 were selected as the subjects.According to the occurrence of ASD at the last follow-up,they were divided into ASD group and non ASD group.The difference of surgical data between the two groups was compared to find the risk factors for ASD..【Results】1.Under 7 working conditions,the stress value of leading-edge forward flexion position is the largest,which is 31.301 Mpa.The force of trailing edge-left rotation position is the highest,which is 17.089 Mpa.The maximum force of left edge-left rotation position is 16.715 Mpa;The maximum force on the right edge-left rotation position was15.261 Mpa;The center-right rotation position has the maximum force of 3.238 Mpa.In the flexion position,extension position and right rotation position,the forces on the leading edge are the largest,which are 31.301 Mpa,28.886 Mpa and 16.576 Mpa,respectively.In the left rotation position,left flexion position and upright position,the force on the trailing edge is the largest,which is 17.089 Mpa,5.202 Mpa and 4.517 Mpa,respectively.In the right flexion position,the force on the right edge is the largest,7.336 Mpa.2.Body mass index(BMI)and Bone mineral density(BMD)are independent risk factors for PJK after long segment lumbar pedicle screw surgery.3.The incidence of ASD was 6.78%.The comparative study found that the risk of ASD was significantly higher in patients with fusion of more than one segment(P<0.05).【Conclusions】For patients with thoracolumbar kyphosis undergoing unilateral UPVCR,the finite element analysis showed that the force on the anterior edge of the upper fixed vertebra disc would increase under three working conditions of the anterior flexion position and the left and right rotation position,which could lead to postoperative PJK;Body mass index and bone mineral density are both potential risk factors leading to the occurrence of PJK after surgery.Therefore,in terms of avoiding the occurrence of PJK after surgery,the perioperative control of the weight of surgical patients is the key to prevent and reduce the occurrence of PJK after surgery,which should be highly valued,and effective anti osteoporosis measures should be taken to reduce the occurrence of PJK;There is a risk of ASD after lumbar decompression,fixation and fusion.The increase of surgical fusion segments is an important risk factor for ASD after surgery.Multi level fusion should be avoided to the maximum extent.