| Proximal junctional kyphosis(PJK)is a common postoperative complication of posterior internal fixation fusion in patients with scoliosis,which can lead to changes in the biomechanical properties of the spine and even loss of motor function,and patients often need to undergo secondary revision surgery,which greatly increases their financial burden.Domestic and international studies have shown that osteoporosis is one of the main factors leading to the occurrence of PJK.Considering that our population is aging and osteoporotic spine disease is a common problem in the elderly population,research related to the prevention of PJK occurrence after long-segment spinal fixation is necessary.In this study,a finite element model of the T10-S1 normal thoracolumbar spine was established and its effectiveness was verified.On this basis,different types of osteoporosis models were established,and the details and results of the study are as follows.(1)The effect of long-segment fixation to distal L5 or S1 on the stability of the thoracolumbar spine.The finite element models of two long segment fixation methods(T11-L5 fixation and T11-S1 fixation)were established,and then the Range of motion(ROM),Intradiscal pressure(IDP)and stress distribution of the connecting rods as well as the maximum Von-Mises stress were calculated for each segment of the thoracolumbar spine.The finite element results showed that the two types of fixation were not possible.Finite element results showed that both fixation methods accelerated disc degeneration in the non-operated segment,however,long segment fixation distal to S1 provided the best decompression of the entire spine and better stability of the spine.Therefore,long-segment fixation to the S1 segment is recommended for patients with scoliosis.(2)Study of bone cement augmentation for preventing the occurrence of PJK in posterior long-segment fixation.Based on the model of long segment fixation to S1(Posterior thoracolumbar fusion,PTCF),different segmental bone cement augmentation models(PTCF+T10VA,PTCF+T11VA,PTCF+T10&T11VA)were established,and then the maximum Von-Mises stresses were calculated for T10 and T11 cancellous,T10-T11 and T11-T12 segmental IDPs,and maximum Von-Mises stresses in the vertebral arch in T11 and T12 vertebrae.The finite element results showed that both single-segment and double-segment augmentation were effective in the prevention of PJK,but the decompression effect of double-segment augmentation was better,and the cancellous stresses in the adjacent segments did not produce a greater increase,thus reducing the occurrence of PJK.(3)Biomechanical differences in the prevention of PJK with different volumes of bone cement augmentation of the vertebral body.Based on the PTCF+T10VA model,finite element models were established by implanting three different volumes of bone cement(2 ml,3 ml,and 4 ml)in the T11 segment,and the ROM,intradiscal pressure and stress distribution,and mean Von-Mises stress of cancellous in the adjacent segments were calculated and analyzed.The finite element results showed that different volumes of bone cement had approximately the same effect on and prevention of PJK.Clinically,bone cement volumes between 2 ml and 4 ml can be used selectively depending on the degree of osteoporosis.Currently,there is a lack of biomechanical studies related to the effectiveness of bone cement for the prevention of PJK.To our knowledge,it has been clinically proven that bone cement enhanced vertebrae can effectively prevent the occurrence of PJK,however,it is unclear how bone cement can prevent PJK,what amount of bone cement is most effective for the prevention of PJK,and what kind of stress-strain is the result of this,while the finite element method can clearly depict the whole The finite element method can clearly depict the stress-strain of the whole system,which can well explain the process of PJK prevention by bone cement reinforced vertebrae.Therefore,in this study,finite element simulation analysis of various surgical models of osteoporotic thoracolumbar spine was performed from the perspective of biomechanics,so as to provide some theoretical reference for clinicians... |
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