Clinical Efficacy And Biomechanical Finite Element Analysis Of Percutaneous Transforaminal Endoscopic Discectomy For Ldh Treatment Based On The Theory Of "Tendon Softening And Bone Restoration"

Background:Lumbar intervertebral disc herniation（LDH）is a disease caused by a series of symptoms,such as lumbar and leg pain induced by nerve root compression due to the protrusion of the nucleus pulposus.Its incidence is accompanied by nerve root compression,decreased lumbar muscle strength,increased muscle tension,loss of intervertebral height and straighter lumbar curvature,consistent with the theory of"Tendon-softening and Bone-restoration"in Traditional Chinese Medicine（TCM）.At present,percutaneous transforaminal endoscopic discectomy（PTED）is a commonly used surgical method for the treatment of LDH,which can achieve definite clinical efficacy,but there are still problems of high recurrence and complication rates.Previous studies have found that PTED surgery reflects the theory of"Tendon-softening and Bone-restoration",and the two are related to each other to a certain extent.However,the clinical efficacy of PTED surgery under the guidance of"Tendon-softening and Bone-restoration"and its impact on lumbar biomechanics remain to be further clarified.Objective:1:To explore the clinical efficacy and biomechanical changes in lumbar spine with LDH treated by PTED based on the theory of"Tendon-softening and Bone-restoration",and to explore its impact on the changes in local soft tissue tension of lumbar spine.2:To explore the effect of PTED surgery guided by the theory of"Tendon-softening and Bone-restoration"on the stress distribution and vertebral body displacement of the intervertebral disc and vertebral body in the operated segment.Methods:1:A total of 30 LDH patients hospitalized in the First Affiliated Hospital of Tianjin University of Traditional Chinese Medicine from February 2021 to November 2021 were selected as the subjects for PTED surgery.The visual analogue scale（VAS）and oswestry disability index（ODI）scores were collected before,as well as at 1 and 3 months after operation to evaluate the clinical efficacy.The changes in lumbar lordosis angle（LL）,lumbosacral angle（LSA）,disc height（DH）and foraminal height（FH）were evaluated before and at 1 month after operation.The sagittal diameters of the foraminal and Pfirrmann grading of nerve roots were compared before and at 3 months after operation for imaging evaluation.In addition,the tension-displacement distance and area ratio of the closed curve of lumbar soft tissue were compared before and at 3 months after operation.SPSS 23.0 software was used for data statistical analysis,and P<0.05 indicated statistically significant differences.2:A patient with L₄-L₅disc herniation was selected,and the lumbar CT data were collected and imported into the image processing software Mimics to construct a preoperative three-dimensional finite element model.The Geomagic Studio software was then employed to construct the curved surface and optimize the surface model.Finally,the operation process of PTED was simulated in the Ansys Workbench software to reconstruct the postoperative FEA model.Under the constraints of loading conditions,the vertical loading value was set at300 N,and the maximum stress distributions of L₄-L₅intervertebral disc and vertebral body,together with the changes in L₄vertebral body position,were analyzed in the preoperative and postoperative FEA models under seven working conditions of vertical,forward flexion,extension,left-lateral tilt and left-lateral rotation,respectively.Finally,SPSS 23.0 software was used to analyze the obtained data.Results:1:Compared with preoperative scores,the VAS and ODI scores of patients significantly decreased at 1 and 3 months after operation,and the differences were statistically significant（P<0.001）.Besides,the length of the middle sagittal diameter of the intervertebral foramen and the degree of nerve root compression were significantly improved at 3 months after surgery,with statistically significant differences（P<0.001）.FH significantly increased at 1month after surgery（P<0.001）,while LL,LSA and DH were not significantly changed,and the differences were not statistically significant（P>0.05）.After 3 months of treatment,the soft tissue tension displacement values of L₁-L₃and L₅lumbar facet joints on the healthy side significantly increased compared with that before operation,and the differences were of statistical significance（P<0.05）.Similarly,the soft tissue tension displacement values of L₃-L₅facet joints on the affected side also increased significantly compared with those before operation,with statistically significant differences（P<0.05）.There was no significant change in the tension displacement value or the area ratio of the closed curve of soft tissue on both sides after operation compared with that before operation（P>0.05）.2:Under the 7 different working load conditions,the postoperative intervertebral disc,vertebral body stress and L₄-L₅vertebral position shift values were changed to varying degrees.In the lumbar spine L₄-L₅intervertebral disc,the stress at maximum right-lateral activities and the maximum stress distribution in the intervertebral disc on the left side（outstanding side）increased,but the postoperative intervertebral disc by the maximum preoperative stress decreased,and intervertebral disc stress distribution was also changed.The maximum stress and displacement of the vertebral body after operation were observed in the pedicle of L₄and spinous process of L₄,respectively.Conclusions:1.PTED surgery for LDH guided by the theory of"Tendon-softening and Bone-restoration"can achieve definite clinical efficacy,which significantly improves the degree of nerve root compression,reduces local soft tissue tension in the waist,and creates a physiological state of"Tendon-softening"inside and outside the"spinal canal".2.The height of the intervertebral foramen significantly increases after operation,which is conducive to maintaining the balance of lumbar mechanical structure and shaping the"Bone-restoration"mechanical structure.3.PTED surgery changes the stress distribution characteristics of the intervertebral disc.The maximum stress value of the intervertebral disc after PTED surgery decreases compared with that before surgery.