[The Biomechanics Influence of unilateral laminectomy and discectomy surgery on the adjacent different grades of Disc Degeneration].

OBJECTIVES: To study the stress distribution of the adjacent different grades of disc degeneration underwenting unilateral laminectomy and discectomy surgery using non-linear finite element analysis. METHODS: Based on the lumbar CT scans, the finite element model (FEM) of lumbar spinal segment (L3-L5) was established. According to L3-L4 intervertebral disc degeneration, different grades of disc degeneration (healthy, mild, moderate and severe) models were established and unilateral laminectomy and discectomy surgery were also established. Physiological action such as flexion, extension, lateral bending and lateral rotation was simulated and the von Mises stress in the nucleus pulposus and annulus fibrosus matrix of L3-L4 disc was investigated. RESULTS: After unilateral laminectomy and discectomy surgery, the extremum value of von Mises stress of nucleus pulposus and annulus fibrosus matrix was maximum during extension and minimus left bending in the healthy intervertebral disc. Compared with healthy disc, the increment of extremum value was found during left bending in the mildly degenerated disc. When the value decreased in the moderately degenerated disc, but still higher than that in the healthy disc. When the adjacent disc is severely degenerated, the extremum value of nucleus pulposus decreased, in addition to axial rotation, and even lower than that of healthy disc. The value of annulus matrix decreased and still higher than that of healthy disc, especially during left bending. CONCLUSIONS: After unilateral laminectomy and discectomy surgery, avoiding lateral bending will reduce the abnormal stress in the degenerated disc and decreased the risk of accelerating disc degeneration.

Influence of volar margin of the lunate fossa fragment fixation on distal radius fracture outcomes: A retrospective series.

BACKGROUND: Distal radius fractures accompanied by the volar margin of the lunate fossa (VMLF) lesions are often overlooked or inadequately reduced in clinical practice. AIM: To investigate the impact of VMLF fragment in distal radius fractures on the stability and function of the wrist joint. METHODS: This was a retrospective study of patients with distal radius fractures who underwent surgical treatment between January 2013 and December 2017. The patients were divided into two groups according to whether the VMLF fragments were fixed or not. X-rays and computed tomography were performed before surgery, immediately postoperatively, and at 1, 3, and 6 mo to measure the scapholunate angle, radiolunate angle, capitolunate angle, and effective radiolunate flexion (ERLF). The Mayo wrist score and disabilities of the arm, shoulder, and hand (DASH) score were determined at 1 year. RESULTS: Thirty-five patients were included. There were 15 males and 20 females. Their mean age was 52.5 ± 14.3 (range: 19-70) years. There were 38 wrists (17 on the left side, 15 on the right, and three bilateral; 16 in the fixed group, and 22 in the unfixed group). The interval between trauma and surgery was from 1 h to 1 mo. The incidence of postoperative wrist instability in the unfixed group (86.4%) was higher than in the fixed group (25.0%) (P ≤ 0.001). Ten patients had ERLF > 25° in the unfixed group and none in the fixed group (P = 0.019). The Mayo wrist score was 94 ± 5.7 in the fixed group and 68 ± 15.1 in the unfixed group (P < 0.001). The DASH score was 4.6 ± 2.5 in the fixed group and 28.5 ± 19.5 in the unfixed group (P < 0.001). CONCLUSION: Injuries of VMLF, even small fractures, might damage the radial-lunar ligament, leading to postoperative wrist instability, sagittal force line imbalance, and poor recovery of wrist joint function.

[Finite element analysis of adolescent idiopathic scoliosis of PUMC II d2 surgical treatment with different fusion levels].

OBJECTIVE: To explore the best surgical fusion level for adolescent idiopathic scoliosis (AIS) of PUMC II d(2) with finite element model (FEM). METHODS: FEM (T(5)-S) of PUMC II d(2) idiopathic scoliosis was used to simulate upper thoracic curve, lower lumbar curve and double curve fusion manners. The pedicle of concave vertebral arch received 50, 100 and 150 N load respectively. Displacement of T(5) and T(11) on upper sagittal plane (displacement of Z axis positive value on upper sagittal plane, displacement of negative value on lower sagittal plane) and their different values were compared. T(5) displacement represented the outcomes of double curve orthopedics. T(11) displacement represented the outcomes of lower lumbar curve orthopedics. Their difference (T(5)-T(11)) represented the outcomes of upper thoracic curve orthopedics. Different fusion segments and displacement of T(5) and T(11) under different orthopedic forces were measured. RESULTS: In PUMC II d(2) lateral curvature, T(5) displacement on Z axis: fusion displacement of double curve was greater than the upper or lower curve alone (F = 8, P < 0.01). Difference of T(5)-T(11) displacement: double curve orthopedics > upper thoracic curve orthopedics alone > lower lumbar curve orthopedics alone (F = 8, P < 0.01). Displacement of T(11) on Z axis: double curve orthopedics > lower lumbar curve orthopedics alone > upper thoracic curve orthopedics alone (F = 8, P < 0.01). CONCLUSION: Fusing two curves achieves the best effect on the AIS of PUMC II d(2) in comparison with upper or lower curve fusion alone. Effects of 3 kinds of load on correction of upper thoracic curve: double curve orthopedics > upper thoracic curve orthopedics alone > lower lumbar curve orthopedics alone. Effect of 3 kinds of load on correction of lower lumbar curve orthopedics alone: double curve orthopedics > lower lumbar curve orthopedics alone > upper thoracic curve orthopedics alone. Three-dimensional finite element analysis is an effective method to analyze the biomechanics of scoliosis deformity correction and provides a virtually non-invasive verification manner. And it may optimize the surgical protocol.

[Association study of Trp2 allele polymorphism with degenerative disc disease in a Chinese Han nationality].

OBJECTIVE: To investigate the association between Trp2 allele polymorphism with degenerative disc disease (DDD) in a Chinese Han population. METHODS: A total of 125 DDD patients (58 males and 67 females, 51.8 +/- 7.6 years old), and 125 controls matched in sex and age (63 males and 62 females, 45.3 +/- 8.3 years old) were recruited in the case-control study. Their peripheral blood samples were collected for DNA isolation. Based on NCBI genebank, the corresponding single nucleotide polymorphisms (snp)-SNP1 (rs7533552) and SNP2 (rs2077871) were identified. Hardy-Weinberg equilibrium was analyzed both in case and control groups. Then the case group was classified into different clinical phenotypes according to severity of degeneration, sole or multi-disc degeneration and different affected discs. Genotyping of all selected SNPs was performed by SNP stream technology. The association analysis between phenotypes and SNPs was conducted. Pairwise linkage disequilibrium was calculated in control population using Haploview 4.0 software. RESULTS: SNP1 (rs7533552), SNP2 (rs2077871) and corresponding SNP of Trp2 allele were gentyped and both polymorphisms distributed in line with Hardy-Weinberg equilibrium in case and control groups. Allelic frequency of SNP1A, SNP1G, SNP2C and SNP2T (42%, 47%, 88% and 90% respectively) of case group were not significantly different from those of control group (48%, 53%, 88% and 10% respectively, all P > 0.05). Genotypic frequencies of SNP1AA, SNP1AG, SNP1GG, SNP2CC, SNP2CT and SNP2TT in case group were not significantly different from those of control group (all P > 0.05). However there was an association with genotypic frequencies of SNP2 and severity of disc degeneration (chi(2) = 6.920, P = 0.031). CONCLUSION: Trp2 allele is one of risk factors for the development and severity of DDD in a Chinese Han population.

A double-network hydrogel for the dynamic compression of the lumbar nerve root.

Current animal models of nerve root compression due to lumbar disc herniation only assess the mechanical compression of nerve roots and the inflammatory response. Moreover, the pressure applied in these models is static, meaning that the nerve root cannot be dynamically compressed. This is very different from the pathogenesis of lumbar disc herniation. In this study, a chitosan/polyacrylamide double-network hydrogel was prepared by a simple two-step method. The swelling ratio of the double-network hydrogel increased with prolonged time, reaching 140. The compressive strength and compressive modulus of the hydrogel reached 53.6 and 0.34 MPa, respectively. Scanning electron microscopy revealed the hydrogel's crosslinked structure with many interconnecting pores. An MTT assay demonstrated that the number of viable cells in contact with the hydrogel extracts did not significantly change relative to the control surface. Thus, the hydrogel had good biocompatibility. Finally, the double-network hydrogel was used to compress the L4 nerve root of male sand rats to simulate lumbar disc herniation nerve root compression. The hydrogel remained in its original position after compression, and swelled with increasing time. Edema appeared around the nerve root and disappeared 3 weeks after operation. This chitosan/polyacrylamide double-network hydrogel has potential as a new implant material for animal models of lumbar nerve root compression. All animal experiments were approved by the Animal Ethics Committee of Neurosurgical Institute of Beijing, Capital Medical University, China (approval No. 201601006) on July 29, 2016.

[Assessment of correction effect in relation to fulcrum bending flexibility in adult idiopathic scoliosis patients].

OBJECTIVE: To study the relationship between the fulcrum bending flexibility (FBF) and correction rate (CR) of adult idiopathic scoliosis, and to explore the ability of FBF to assess the correction effect in relation to fulcrum bending flexibility. METHODS: 69 patients with adult idiopathic scoliosis with structural curves at thoracic or lumbarthoracic segments, 16 males and 53 females, aged 26.5 (19 - 53) were treated by pedicle screws instrumentation. Pre-operative standing and fulcrum bending films and postoperative standing X-ray film were taken. Cobb angle was measured. The data underwent regression analysis with the software SPSS 10.0. RESULTS: A regression formula was established: CR = 0.213 + 0.768 x FBF with P < 0.01. CONCLUSION: A definite linear relation exists between the FBF and CR of adult idiopathic scoliosis. By using the formula in proper samples, the effects of new instrumentation or correction technique can be objectively assessed.

[Finite element analysis on stress change of lumbar spine].

OBJECTIVE: To build a 3D finite element model of whole lumbar spine and verify its efficiency and analyze the biomechanical change of L3-4 motion segment. METHODS: L1-L5 segment data were obtained from computed tomography (CT) scans of the lumbar spine of a 40-year-old man with no abnormal findings. A three-dimensional finite element model of the human whole lumbar spine was built in the Mimics and the ABAQUS software. The model was composed of bony vertebrae, articulating facets, intervertebral disc and associated ligaments. The basic stress analysis of L3-4 motion segment was made under the considerations of different material properties of bone, ligaments and facet joints contacting frictional property. The stress on annulus fiber, nucleus pulposus, endplate and facet joints under axial pressure (0.3 MPa, 0.5 MPa, 1.0 MPa, 2.0 MPa & 4.0 MPa) were analyzed. RESULTS: A three-dimensional finite element model of human L3-L4 motion segment has 272, 619 elements, the stresses were higher in the posterior of annulus fiber, the Max pressure stress (S33) distributed in nucleus pulposus and the center of endplate. The stresses increased as axial pressure rose. CONCLUSION: 3D finite element model of whole lumbar spine and L3-4 motion segment were established successfully and the stress analyses were feasible and reliable.

[Finite element analysis of stress changes of posterior spinal pedicle screw infixation].

OBJECTIVE: To evaluate the mechanical response of L3-L4 segment after posterior interfixation with a transpedicle screw system. METHODS: Spiral CT machine was used to conduct continuous parallel scan on the L3-L4 section of a 40-year-old healthy male Chinese. The image data thus obtained were introduced into MIMICS software to reconstruct the 2-D data into volume data and obtain 3-D models of every element.. Pro/3-D model construction software system was used to simulate the 3-D entity of L3-L4 fixed by screw robs through spinal pedicle via posterior approach that was introduced into the finite element software ABAQUS to construct a 3-D finite element model. The stress changes on the vertebrae and screw under the axial pressure of 0.5 mPa was analyzed. RESULTS: Under the evenly distributed pressure the displacement of the L4 model was 0.00125815 mm, with an error of only 0.8167% from the datum displacement. The convergence of the model was good. The stress of the fixed vertebral body, intervertebral disc, and internal fixators changed significantly. The stress concentration zone of the intervertebral disc turned from the posterolateral side to anterolateral side. The stress produced by the fixed vertebral bodies decreased significantly. Obvious stress concentration existed in the upper and lower sides of the base of screw and the fixed screw at the upper vertebral body bore greater stress than the lower vertebral body. CONCLUSIONS: Integration of computer aided device and finite element analysis can successfully stimulate the internal fixation of L3-IA visa posterior approach and observe the mechanic changes in the vertebral column more directly.

[Finite element analysis on stress change of the lumbar disc degeneration].

OBJECTIVE: To investigate the mechanical changes of the degenerated lumbar disc with finite element analysis. METHODS: A three dimensional finite element model of a human lumbar spine at the L3-L4 disc was established by the software MIMICS and ABAQUS based on computer tomography images. Degeneration was modeled by changes in geometry and material properties. The model was loaded with 0.3 MPa in axial plane. The von Mises stress on the annulus fiber, nucleus pulposus, endplate and facet joints in healthy and degenerated discs was compared. RESULT: Compared with healthy discs, the von Mises stress of disc distributed in the side of annulus fiber, the stress of nucleus pulposus decreased remarkably, the stress of endplate distributed in the posterior part, and the stress of facet joints increased for the degenerated disc. CONCLUSION: The finite element models can provide a method of understanding the relationship between biomechanical performance of the disc due to disc degeneration.

Folic acid contributes to peripheral nerve injury repair by promoting Schwann cell proliferation, migration, and secretion of nerve growth factor.

After peripheral nerve injury, intraperitoneal injection of folic acid improves axon quantity, increases axon density and improves electromyography results. However, the mechanisms for this remain unclear. This study explored whether folic acid promotes peripheral nerve injury repair by affecting Schwann cell function. Primary Schwann cells were obtained from rats by in vitro separation and culture. Cell proliferation, assayed using the Cell Counting Kit-8 assay, was higher in cells cultured for 72 hours with 100 mg/L folic acid compared with the control group. Cell proliferation was also higher in the 50, 100, 150, and 200 mg/L folic acid groups compared with the control group after culture for 96 hours. Proliferation was markedly higher in the 100 mg/L folic acid group compared with the 50 mg/L folic acid group and the 40 ng/L nerve growth factor group. In Transwell assays, the number of migrated Schwann cells dramatically increased after culture with 100 and 150 mg/L folic acid compared with the control group. In nerve growth factor enzyme-linked immunosorbent assays, treatment of Schwann cell cultures with 50, 100, and 150 mg/L folic acid increased levels of nerve growth factor in the culture medium compared with the control group at 3 days. The nerve growth factor concentration of Schwann cell cultures treated with 100 mg/L folic acid group was remarkably higher than that in the 50 and 150 mg/L folic acid groups at 3 days. Nerve growth factor concentration in the 10, 50, and 100 mg/L folic acid groups was higher than that in the control group at 7 days. The nerve growth factor concentration in the 50 mg/L folic acid group was remarkably higher than that in the 10 and 100 mg/L folic acid groups at 7 days. In vivo, 80 µg/kg folic acid was intraperitoneally administrated for 7 consecutive days after sciatic nerve injury. Immunohistochemical staining showed that the number of Schwann cells in the folic acid group was greater than that in the control group. We suggest that folic acid may play a role in improving the repair of peripheral nerve injury by promoting the proliferation and migration of Schwann cells and the secretion of nerve growth factors.

[Imaging diagnosis of degenerative scoliosis and adult idiopathic scoliosis].

OBJECTIVE: To analyze and compare the Imaging findings of adult idiopathic scoliosis and degenerative scoliosis which were the most common adult scoliosis, and evaluate imaging characteristics. METHOD: The radiological and clinical data of 98 case, among them, 41 cases of adult idiopathic scoliosis and 57 cases of degenerative scoliosis, were analyzed retrospectively. RESULT: There were differences at presence age, sex ratio, anatomic area of scoliosis and apex between two types of adult scoliosis. The analyses and comparison between the two groups revealed significant change in the Cobb angle, involved segment and convex side orientation (all P < 0.05). CONCLUSION: Adult idiopathic scoliosis and degenerative scoliosis show distinctive imaging characteristics. These characteristics combining clinical data are decisive in diagnosis.

Non-invasive quantification of age-related changes in the vertebral endplate in rats using in vivo DCE-MRI.

BACKGROUND: Small animal models that can mimic degenerative disc disease (DDD) are commonly used to examine DDD progression. However, assessments such as histological studies and macroscopic measurements do not allow for longitudinal studies because they can only be completed after the animal is sacrificed. Dynamic contrast-enhanced MRI (DCE-MRI) may provide a reliable, non-invasive in vivo method for detecting the progression. METHODS: The present study investigated the progression of changes in lumbar discs and the effect of endplate conditions on diffusion into the lumbar discs of aging sand rats after intravenous administration of gadolinium-containing contrast medium through the tail vein. Contrast enhancement was measured in the lumbar intervertebral discs on each image. The results were compared with those from conventional histological characterizations. RESULTS: T2-weighted images revealed that with aging, the shape of L3-L4, L4-L5, L5-L6, and L6-S1 nucleus pulposus (NP) became irregular, while the mean areas, signal intensities, and T2 values of the NP were significantly decreased. Each of the observed disc changes demonstrated a progressive increase in phase during 2-min scout scans. Post-contrast MRI showed impaired endplate nutritional diffusion to the disc with aging, enhancement was significantly greater in young animals than in old animals. Endplate calcification or sclerosis was histologically confirmed; histologic score was correlated with the age. We found the histological score of the endplate negatively corresponded to the DCE-MRI results. CONCLUSIONS: DCE-MRI studies offer a non-invasive in vivo method for investigating the progress of diffusion into the discs and the functional conditions of the endplate. We conclude that quantitative DCE-MRI can identify the severity of disc degeneration and efficiently reflect the progression of vertebral endplate changes in the aging sand rat lumbar spine via the NP contrast enhancement patterns.

[Dynamic observation of the biomechanic properties of sciatic nerve at the suture site in rats following repairing].

OBJECTIVE: To observe the biomechanic properties of sciatic nerve at the suture site in rats following repairing. METHODS: The right sciatic nerves of 40 white Sprague-Dawley 300-350 gm rats were exposed, cut and then repaired with 10-0 nylon sutures, laced in the epineurium. 0, 1, 3, 6 weeks after operation, the tensile strength of the sciatic nerves were measured, the data analyzed statistically. RESULTS: The load-elongation curves for both the normal unoperated and operated nerves had the similar shape. The tensile strength of the 0 week was significant difference to 1, 3 and 6 weeks (P < 0.01). No significant difference was found among 1, 3 and 6 weeks. CONCLUSION: The tensile strength of the injured nerves are recovered in the first week and resistant in 6 weeks after repairing.

Minimally invasive transforaminal lumbar interbody fusion (MI-TLIF): surgical technique, long-term 4-year prospective outcomes, and complications compared with an open TLIF cohort.

Transforaminal lumbar interbody fusion (TLIF) is an important surgical option for the treatment of back pain and radiculopathy. The minimally invasive TLIF (MI-TLIF) technique is increasingly used to achieve neural element decompression, restoration of segmental alignment and lordosis, and bony fusion. This article reviews the surgical technique, outcomes, and complications in a series of 144 consecutive 1- and 2-level MI-TLIFs in comparison with an institutional control group of 54 open traditional TLIF procedures with a mean of 46 months' follow-up. The evidence base suggests that MI-TLIF can be performed safely with excellent long-term outcomes.

Finite element analysis in adjacent segment degeneration after lumbar fusion.

BACKGROUND: Adjacent segment degeneration (ASD) following lumbar fusion has been well documented in recent years. However, the pathogenesis of ASD is not clear. To investigate this issue, we established a finite element model of segments L2-L5, simulated a single-segment posterior fixation in L3-L4 and investigated the stress variation and the effects of the instrumented lumbar posterior fixation on adjacent levels. METHODS: Models A, B and C of L2-L5 multisegment finite element intact models were established. In model A, segment L3-L4 was not fixed and was without disc degeneration in the adjacent segment (L2-L3, L4-L5); in model B there was posterior pedicle fixation in segment L3-L4 without disc degeneration in the adjacent segment (L2-L3, L4-L5); in model C there was posterior pedicle fixation in segment L3-L4 with a degenerated disc in the adjacent segment (L2-L3, L4-L5). Four levels of axial pressure, 0.3, 0.5, 1.0 and 2.0 MPa, were compared between each model of the stress variation on the discs of the adjacent segment (L2-L3, L4-L5). RESULTS: The maximum principal stress mean value of disc L2-L3 under four pressures in model A was determined. The statistical results showed that stress was not significant difference in disc L2-L3 between models A and B, but there was a significant difference in disc L2-L3 between models A and C and a significant difference between each group in disc L4-L5 under four pressure conditions. CONCLUSIONS: The preoperative degeneration of the adjacent segment of the disc is a significant risk factor for ASD.