Clinical trials have demonstrated that kilohertz-frequency transcutaneous spinal cord stimulation (TSCS) can be used to facilitate the recovery of sensory-motor function for patients with spinal cord injury, whereas the neural mechanism of TSCS is still undetermined so that the choice of stimulation parameters is largely dependent on the clinical experience. In this paper, a finite element model of transcutaneous spinal cord stimulation was used to calculate the electric field distribution of human spinal cord segments T ₁₂ to L ₂, whereas the activation thresholds of spinal fibers were determined by using a double-cable neuron model. Then the variation of activation thresholds was obtained by varying the carrier waveform, the interphase delay, the modulating frequency, and the modulating pulse width. Compared with the sinusoidal carrier, the usage of square carrier could significantly reduce the activation threshold of dorsal root (DR) fibers. Moreover, the variation of activation thresholds was no more than 1 V due to the varied modulating frequency and decreases with the increased modulating pulse width. For a square carrier at 10 kHz modulated by rectangular pulse with the frequency of 50 Hz and the pulse width of 1 ms, the lowest activation thresholds of DR fibers and dorsal column fibers were 27.6 V and 55.8 V, respectively. An interphase delay of 5 μs was able to reduce the activation thresholds of the DR fibers to 20.1 V. The simulation results can lay a theoretical foundation on the selection of TSCS parameters in clinical trials.
Humans ; Spinal Cord Stimulation/methods* ; Nerve Fibers/physiology* ; Finite Element Analysis ; Spinal Cord/physiology* ; Computer Simulation ; Spinal Cord Injuries/physiopathology* ; Lumbosacral Region ; Lumbar Vertebrae ; Transcutaneous Electric Nerve Stimulation/methods* ; Models, Neurological

In order to investigate the mechanical response of lumbar vertebrae during gait cycle in adolescents with idiopathic scoliosis (AIS), the present study was based on computed tomography (CT) data of AIS patients to construct model of the left support phase (ML) and model of the right support phase (MR), respectively. Firstly, material properties, boundary conditions and load loading were set to simulate the lumbar vertebra-pelvis model. Then, the difference of stress and displacement in the lumbar spine between ML and MR was compared based on the stress and displacement cloud map. The results showed that in ML, the lumbar stress was mostly distributed on the convex side, while in MR, it was mostly distributed on the concave side. The stress of the two types of stress mainly gathered near the vertebral arch plate, and the stress of the vertebral arch plate was transmitted to the vertebral body through the pedicle with the progress of gait. The average stress of the intervertebral tissue in MR was greater than that in ML, and the difference of stress on the convex and convex side was greater. The displacement of lumbar vertebrae in ML decreased gradually from L1 to L5. The opposite is true in MR. In conclusion, this study can accurately quantify the stress on the lumbar spine during gait, and may provide guidance for brace design and clinical decision making.
Humans ; Lumbar Vertebrae/diagnostic imaging* ; Scoliosis/diagnostic imaging* ; Adolescent ; Gait/physiology* ; Biomechanical Phenomena ; Tomography, X-Ray Computed ; Stress, Mechanical ; Female ; Male

The lumbar intervertebral disc exhibits a complex physiological structure with interactions between various segments, and its components are extremely complex. The material properties of different components in the lumbar intervertebral disc, especially the water content (undergoing dynamic change as influenced by age, degeneration, mechanical loading, and proteoglycan content) - critically determine its mechanical properties. When the lumbar intervertebral disc is under continuous pressure, water seeps out, and after the pressure is removed, water re-infiltrates. This dynamic fluid exchange process directly affects the mechanical properties of the lumbar intervertebral disc, while previous isotropic modeling methods have been unable to accurately reflect such solid-liquid phase behaviors. To explore the load-bearing mechanism of the lumbar intervertebral disc and establish a more realistic mechanical model of the lumbar intervertebral disc, this study developed a solid-liquid biphasic, fiber-reinforced finite element model. This model was used to simulate the four movements of the human lumbar spine in daily life, namely flexion, extension, axial rotation, and lateral bending. The fluid pressure, effective solid stress, and liquid pressure-bearing ratio of the annulus fibrosus and nucleus pulposus of different lumbar intervertebral discs were compared and analyzed under the movements. Under all the movements, the fluid pressure distribution was closer to the nucleus pulposus, while the effective solid stress distribution was more concentrated in the outer annulus fibrosus. In terms of fluid pressure, the maximum fluid pressure of the lumbar intervertebral disc during lateral bending was 1.95 MPa, significantly higher than the maximum fluid pressure under other movements. Meanwhile, the maximum effective solid stress of the lumbar intervertebral disc during flexion was 2.43 MPa, markedly higher than the maximum effective solid stress under other movements. Overall, the liquid pressure-bearing ratio under axial rotation was smaller than that under other movements. Based on the solid-liquid biphasic modeling method, this study more accurately revealed the dominant role of the liquid phase in the daily load-bearing process of the lumbar intervertebral disc and the solid-phase mechanical mechanism of the annulus fibrosus load-bearing, and more effectively predicted the solid-liquid phase co-load-bearing mechanism of the lumbar intervertebral disc in daily life.
Humans ; Finite Element Analysis ; Intervertebral Disc/physiology* ; Lumbar Vertebrae/physiology* ; Weight-Bearing/physiology* ; Biomechanical Phenomena ; Stress, Mechanical ; Computer Simulation ; Models, Biological

To investigate the effects of postoperative fusion implantation on the mesoscopic biomechanical properties of vertebrae and bone tissue osteogenesis in idiopathic scoliosis, a macroscopic finite element model of the postoperative fusion device was developed, and a mesoscopic model of the bone unit was developed using the Saint Venant sub-model approach. To simulate human physiological conditions, the differences in biomechanical properties between macroscopic cortical bone and mesoscopic bone units under the same boundary conditions were studied, and the effects of fusion implantation on bone tissue growth at the mesoscopic scale were analyzed. The results showed that the stresses in the mesoscopic structure of the lumbar spine increased compared to the macroscopic structure, and the mesoscopic stress in this case is 2.606 to 5.958 times of the macroscopic stress; the stresses in the upper bone unit of the fusion device were greater than those in the lower part; the average stresses in the upper vertebral body end surfaces were ranked in the order of right, left, posterior and anterior; the stresses in the lower vertebral body were ranked in the order of left, posterior, right and anterior; and rotation was the condition with the greatest stress value in the bone unit. It is hypothesized that bone tissue osteogenesis is better on the upper face of the fusion than on the lower face, and that bone tissue growth rate on the upper face is in the order of right, left, posterior, and anterior; while on the lower face, it is in the order of left, posterior, right, and anterior; and that patients' constant rotational movements after surgery is conducive to bone growth. The results of the study may provide a theoretical basis for the design of surgical protocols and optimization of fusion devices for idiopathic scoliosis.
Humans ; Scoliosis/surgery* ; Spinal Fusion/methods* ; Lumbar Vertebrae/surgery* ; Osteogenesis ; Biomechanical Phenomena/physiology* ; Finite Element Analysis

OBJECTIVE: To analyze dynamic electromyography characteristics and related factors of lumbar back muscle activity in patients with lumbar disc herniation, and to clarify the clinical significance of dynamic electromyography in the diagnosis and treatment of patients with lumbar disc herniation(LDH). METHODS: From September 2014 to March 2021, 40 patients with lumbar disc herniation(LDH group) were detected by surface electromyography telemeter. There were 14 males and 26 females, aged from 20 to 61 years old, with an average of(40.68±10.56) years old, the course of illness was from 1 to 120 months, with an average of (17.75±27.56) months. In addition, 12 normal people were recruited as the control group. There were 2 males and 10 females. The age ranged from 24 to 53 years old, with an average of(36.50±10.30) years old. All subjects were subjected to dynamic electromyographic tests of the subthoracic erector spinae, lumbar erector spinae, and multifidus muscles during static standing and trunk flexion and extension. Compare the EMG activity data (average EMG amplitude, median frequency, original EMG graph) of the tested muscles between patients with lumbar disc herniation and normal people, and analyze the correlation between the general data of patients with lumbar disc herniation and the tested muscle EMG data. RESULTS: When standing still, the average electromyographic amplitude of the erector spinal muscle of the right and left thoracic segments of the subjects in the LDH group increased compared with the control group, and the difference was significant(P<0.05). In the trunk flexion and extension, the average electromyographic amplitude of the right and left proximal thoracic erector spinae, the right left lumbar erector spinae, and the right left multifidus muscle of the subjects in the LDH group are all larger than the control group, and the difference was significant(P<0.05). In the trunk flexion and extension, the median frequencies of the right left proximal thoracic erector spinae、the right left lumbar erector spinae, and the right left multifidus muscle of the subjects in the LDH group were all larger than the normal control group, and the difference was significant (P<0.05). During trunk flexion and extension, the original electromyographic patterns of subjects in the LDH group were significantly different from those in the control group. During the maintenance of the maximum trunk flexion of the subjects in the LDH group, there was a high level of electromyographic activity of the lower back muscles, and the electromyographic static signals that should appear regularly in the original signal could not be distinguished. When the trunk was flexed and extended, had gender, age, weight and height of subjects in the LDH group were not significantly correlated with the average EMG amplitude and median frequency of bilateral proximal thoracic, lumbar erector spinae and bilateral multifidus muscles respectively(P>0.05). CONCLUSION Patients with lumbar disc herniation have characteristic surface EMG changes in the back muscles that are different from those of normal people. These features can more objectively reflect the patient's muscle condition and can be an effective indicator for the diagnosis and treatment effect evaluation of patients with lumbar disc herniation. It can be seen that surface electromyography is not only a detection method, it can be considered in the routine diagnosis and treatment plan of LDH to guide clinical work.
Male ; Female ; Humans ; Young Adult ; Adult ; Middle Aged ; Electromyography ; Intervertebral Disc Displacement/therapy* ; Lumbar Vertebrae ; Paraspinal Muscles ; Range of Motion, Articular/physiology* ; Muscle, Skeletal

BACKGROUND: Areal bone mineral density (aBMD) applied for osteoporosis diagnosis unavoidably results in the missingdiagnosis in patients with large bones and misdiagnosis in those with small bones. Therefore, we try to find a new adjusted index of bone mineral content (BMC) to make up shortcomings of aBMD in osteoporosis diagnosis. METHODS: In this multi-center epidemiological study, BMC and aBMD of lumbar spines (n = 5510) and proximal femurs (n = 4710) were measured with dual energy X-ray absorptiometry (DXA). We analyzed the correlation between the bone mass and body weight in all subjects including four age groups (<19 years, 20-39 years, 40-49 years, >50 years). And then the body weight was used for standardizing BMC (named wBMC) and applied for the epidemiological analysis of osteoporosis. RESULTS: The correlation of body weight and BMC is 0.839 to 0.931 of lumbar vertebra 1-4 (L1-4), and 0.71 to 0.95 of femoral neck in different age groups. When aBMD was applied for diagnosing osteoporosis, the prevalence was 7.55%, 16.39%, and 25.83% in patients with a high, intermediate, and low body weight respectively. However, the prevalence was 21.8%, 18.03%, and 11.64% by wBMC applied for diagnosing osteoporosis. Moreover, the prevalence of osteoporosis increased by 3.76% by wBMC with the body weight increased by 5 kg. The prevalence decreased by 1.94% when the body weight decreased by 5 kg. CONCLUSIONS wBMC can reduce the missed diagnosis in patients with large body weight and reduce misdiagnosis in those with small body weight. Including children, wBMC may be feasible for osteoporosis diagnosis individuals at any age.
Absorptiometry, Photon ; Adult ; Age Factors ; Body Weight ; physiology ; Bone Density ; physiology ; Female ; Femur Neck ; diagnostic imaging ; metabolism ; Humans ; Lumbar Vertebrae ; diagnostic imaging ; metabolism ; Middle Aged ; Osteoporosis ; diagnostic imaging ; metabolism ; Prevalence ; Young Adult

BACKGROUND: Some porous materials have been developed to enhance biologic fusion of the implants to bone in spine fusion surgeries. However, there are several inherent limitations. In this study, a novel biomedical porous tantalum was applied to in vitro and in vivo experiments to test its biocompatibility and osteocompatibility. METHODS: Bone marrow-derived mesenchymal stem cells (BMSCs) were cultured on porous tantalum implant. Scanning electron microscope (SEM) and Cell Counting Kit-8 assay were used to evaluate the cell toxicity and biocompatibility. Twenty-four rabbits were performed discectomy only (control group), discectomy with autologous bone implanted (autograft group), and discectomy with porous tantalum implanted (tantalum group) at 3 levels: L3-L4, L4-L5, and L5-L6 in random order. All the 24 rabbits were randomly sacrificed at the different post-operative times (2, 4, 6, and 12 months; n = 6 at each time point). Histologic examination and micro-computed tomography scans were done to evaluate the fusion process. Comparison of fusion index scores between groups was analyzed using one-way analysis of variance. Other comparisons of numerical variables between groups were made by Student t test. RESULTS: All rabbits survived and recovered without any symptoms of nerve injury. Radiographic fusion index scores at 12 months post-operatively between autograft and tantalum groups showed no significant difference (2.89 ± 0.32 vs. 2.83 ± 0.38, F = 244.60, P = 0.709). Cell Counting Kit-8 assay showed no significant difference of absorbance values between the leaching liquor group and control group (1.25 ± 0.06 vs. 1.23 ± 0.04, t = -0.644, P = 0.545), which indicated the BMSC proliferation without toxicity. SEM images showed that these cells had irregular shapes with long spindles adhered to the surface of tantalum implant. No implant degradation, wear debris, or osteolysis was observed. Histologic results showed solid fusion in the porous tantalum and autologous bone implanted intervertebral spaces. CONCLUSION This novel porous tantalum implant showed a good biocompatibility and osteocompatibility, which could be a valid biomaterial for interbody fusion cages.
Animals ; Cell Proliferation ; physiology ; Diskectomy ; Lumbar Vertebrae ; surgery ; Microscopy, Electron, Scanning ; Prostheses and Implants ; Rabbits ; Spinal Fusion ; Tantalum ; chemistry

In order to study the mechanical behavior of degeneration and nucleotomy of lumbar intervertebral disc, compression experiments with porcine lumbar intervertebral discs were carried out. The lumbar intervertebral discs with trypsin-treated and nucleus nucleotomy served as the experimental group and the normal discs as the control group. Considering the effects of load magnitude and loading rate, the relationship between stress and strain, instantaneous elastic modulus and creep property of intervertebral disc were obtained. The creep constitutive model was established. The results show that the strain and creep strain of the experimental group increase significantly with the increase of compression load and loading rate, whereas the instantaneous elastic modulus decreases obviously, compared with the control group. It indicates that the effect of load magnitude and loading rate on load-bearing capacity of intervertebral disc after nucleotomy is larger obviously than that of normal disc. The creep behavior of the experimental group can be still predicted by the Kelvin three-parameter solid model. The results will provide theoretical foundation for clinical treatment and postoperative rehabilitation of intervertebral disc disease.
Animals ; Biomechanical Phenomena ; Intervertebral Disc ; physiology ; surgery ; Lumbar Vertebrae ; Stress, Mechanical ; Swine ; Weight-Bearing

BACKGROUND: To evaluate the effect of spondylolisthesis on lumbar lordosis on the OSI (Jackson; Orthopaedic Systems Inc.) frame. Restoration of lumbar lordosis is important for maintaining sagittal balance. Physiologic lumbar lordosis has to be gained by intraoperative prone positioning with a hip extension and posterior instrumentation technique. There are some debates about changing lumbar lordosis on the OSI frame after an intraoperative prone position. We evaluated the effect of spondylolisthesis on lumbar lordosis after an intraoperative prone position. METHODS: Sixty-seven patients, who underwent spinal fusion at the Department of Orthopaedic Surgery of Gwangmyeong Sungae Hospital between May 2007 and February 2012, were included in this study. The study compared lumbar lordosis on preoperative upright, intraoperative prone and postoperative upright lateral X-rays between the simple stenosis (SS) group and spondylolisthesis group. The average age of patients was 67.86 years old. The average preoperative lordosis was 43.5degrees (+/- 14.9degrees), average intraoperative lordosis was 48.8degrees (+/- 13.2degrees), average postoperative lordosis was 46.5degrees (+/- 16.1degrees) and the average change on the frame was 5.3degrees (+/- 10.6degrees). RESULTS: Among all patients, 24 patients were diagnosed with simple spinal stenosis, 43 patients with spondylolisthesis (29 degenerative spondylolisthesis and 14 isthmic spondylolisthesis). Between the SS group and spondylolisthesis group, preoperative lordosis, intraoperative lordosis and postoperative lordosis were significantly larger in the spondylolisthesis group. The ratio of patients with increased lordosis on the OSI frame compared to preoperative lordosis was significantly higher in the spondylolisthesis group. The risk of increased lordosis on frame was significantly higher in the spondylolisthesis group (odds ratio, 3.325; 95% confidence interval, 1.101 to 10.039; p = 0.033). CONCLUSIONS: Intraoperative lumbar lordosis on the OSI frame with a prone position was larger in the SS patients than the spondylolisthesis patients, which also produced a larger postoperative lordosis angle after posterior spinal fusion surgery. An increase in lumbar lordosis on the OSI frame should be considered during posterior spinal fusion surgery, especially in spondylolisthesis patients.
Aged ; Aged, 80 and over ; Female ; Humans ; Intraoperative Care/*methods ; Lumbar Vertebrae/*surgery ; Male ; Middle Aged ; Postoperative Complications/*prevention & control ; Posture/physiology ; Prone Position/*physiology ; Retrospective Studies ; Spinal Stenosis/*surgery ; Spondylolisthesis/*surgery

INTRODUCTIONThis retrospective review aimed to examine the relationship between preoperative pulmonary function and the Cobb angle, location of apical vertebrae and age in adolescent idiopathic scoliosis (AIS). To our knowledge, there have been no detailed analyses of preoperative pulmonary function in relation to these three factors in AIS.

METHODSA total of 38 patients with thoracic or thoracolumbar scoliosis were included. Curvature of spinal deformity was measured using the Cobb method. Forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) were used to evaluate preoperative pulmonary function. Statistical methods were used to analyse the relationship between preoperative pulmonary function and the factors that may contribute to poor pulmonary function.

RESULTSThe mean age of the patients was 16.68 ± 6.04 years. An inverse relationship was found between the degree of the Cobb angle and FVC as well as FEV1; however, the relationships were not statistically significant (p = 0.057 and p = 0.072, respectively). There was also a trend towards a significant negative correlation between the thoracic curve and FVC (p = 0.014). Patients with larger thoracic curves had lower pulmonary function. A one-year increase in age significantly decreased FVC by 1.092 units (p = 0.044). No significant relationship between age and preoperative FEV1 was found. The median FVC was significantly higher in patients with affected apical vertebrae located at levels L1-L3 than at T6-T8 or T9-T12 (p = 0.006).

CONCLUSIONLung function impairment was seen in more severe spinal deformities, proximally-located curvature and older patients.

Adolescent ; Adult ; Female ; Follow-Up Studies ; Forced Expiratory Volume ; physiology ; Humans ; Kyphosis ; diagnosis ; physiopathology ; surgery ; Lumbar Vertebrae ; Lung ; physiopathology ; Male ; Preoperative Period ; Respiratory Function Tests ; Retrospective Studies ; Scoliosis ; diagnosis ; physiopathology ; surgery ; Severity of Illness Index ; Spinal Fusion ; methods ; Thoracic Vertebrae ; Young Adult