The effect of rib cage on the dynamic response stability of the scoliotic spine / 生物医学工程学杂志

The purpose of this study is to reveal the protective effect of rib cage on scoliotic spine by comparing the different effect of rib cage on the stability of normal spine and Lenke1 scoliotic spine. Firstly, according to X-ray computed tomography (CT) image data, four spinal finite element models (SFEMs), including normal spine without rib cage (N1), normal spine with normal rib cage (N2), scoliotic spine without rib cage (S1) and scoliotic spine with deformed rib cage (S2), from the first thoracic vertebrae to the sacral vertebrae (T1～S) were established. Secondly, the natural vibration characteristics of the four SFEMs were obtained by modal analysis. Finally, the maximum vibration amplitudes of the four SFEMs under external excitation were obtained by steady-state analysis. As shown in results, compared with N1, the maximum deformation of N2 segment T4～T6 in the -axis (coronal axis), -axis (sagittal axis) and -axis (vertical axis) directions decreases by 38.44%, 53.80% and 33.72%, respectively. Compared with S1, the maximum deformation of S2 segment T4～T6 in the -axis direction, -axis direction and -axis directions decreases by 44.26%, increases by 32.80% and decreases by 49.23%, respectively. As it can be seen, for normal spine, the rib cage can improve the stability of the whole spine in three directions; for the Lenke1 scoliotic spine, the rib cage can reduce the vibration of the scoliotic spine in the -axis and -axis directions and improves the stability of the whole spine in the two directions, while in the -axis direction, for the serious severe anteversion of scoliotic spine, the deformed rib cage exacerbates the vibration of the scoliotic spine in this direction and destroys the stability of the scoliotic spine in the -axis direction. This study reveals the biomechanical characteristics of rib caged influence on the stability of the scoliotic spine and it has guiding significance for the study of daily protection methods and protective tools for scoliotic patients.

Dynamic Characteristics of an Adolescent Idiopathic Scoliotic Spine / 医用生物力学

Objective To establish the three-dimensional (3D) finite element (FE) model of thoracolumbosacral T1-S spine based on the computed tomography (CT) images of patients with scoliosis and study its dynamic characteristics. Methods The established scoliotic model was validated by axial compression and shear loading, and the predicted responses were in good agreement with the experimental data. The modal and harmonic analyses were performed using the ABAQUS software, and during the harmonic analysis, the dynamic response of the model was collected at frequencies 5 Hz and 10 Hz. Results From the modal analysis, the first fourth-order modal was extracted. The first- and second-order resonant frequencies of the model were 1.097 Hz and 1.384 Hz, respectively, and the vibration mode was longitudinal bending and lateral bending, respectively. The distribution of the second- and third-order modal resonant frequencies were 5.688 Hz and 28.090 Hz, and the vibration mode was vertical vibration and twisting around the long axis, respectively. The peak amplitude in the harmonic analysis appeared near the modal frequencies, and the average amplitude of vertebral body of the lateral convex segment was larger than that of other segments of the scoliotic spine. Under the vibration frequencies of 5 Hz and 10 Hz, the stress inhomogeneously concentrated on the concave and convex sides of the segments of the vertebral deformity as well as on the intervertebral disc. Conclusions The segments of the spinal deformity in patients with scoliosis were the weak links of their spines and more vulnerable to damage in a vibrating environment. Patients with scoliosis should avoid a vibrating environment, particularly in a sensitive frequency range. The research outcomes provide methodological assistance and mechanical analysis references for the protection, rehabilitation treatment, and clinical pathological studies of patients with scoliosis.

Flexibility of the coronal lumbosacral region of congenital scoliosis: a three-dimensional finite element analysis / 中国组织工程研究

BACKGROUND: In the patients with congenital scoliosis, the spinal motor units exhibit developmental disorders and poor range of motion. It has been found that the compensation ability of coronal lumbosacral region (L4-S1) is associated with the occurrence of non-compensable trunk migration postoperatively.OBJECTIVE: To establish the three-dimensional finite element models of coronal lumbosacral region of normal and patients with congenital scoliosis and to compare the strain, displacement, stress and stiffness under different loading conditions among models.METHODS: One normal subject and two congenital scoliosis patients with different coronal lumbosacral region flexibility were selected, DICOM image datawere obtained by spiral CT scanning at the lumbosacral region, and then imported into MIMICS software, and a three-dimensional model was established according to the gray values of each tissue on CT,followed by simplified by GEOMAGIC, and finally imported into ABAQUS foftware to conduct a mechanic analysis under different loading conditions.RESULTS AND CONCLUSION: (1) Under different lateral forces, in the three models, the maximum stress mainly distributed on the frontal region of L4 cortical bone, and maximum displacement concentrated on L5. (2) There was no significant change in the stress distribution in the two scoliosis models, but the compensable model showed larger displacement change, and its stiffness was significantly less than that of the non-compensable model, indicating that the compensable model is easy to deform. (3) These findings suggest that three-dimensional finite element model is helpful to perform a biomechanical analysis for coronal lumbosacral region of congenital scoliosis, among which, a compensable model exhibits large displacement, suggesting a good flexibility.

Finite element analysis on scoliosis lumbosacral vertebral structure and its deformation trend / 医用生物力学

Objective To study the correlation between the deformation and displacement trend of the lumbosacral vertebra (L1-S1) for two typical scoliosis spines under vertical loads,so as to provide the mechanical basis of treatment and prevention of scoliosis in clinic.Methods The X-ray computed tomography (CT) images of two typical scoliosis spines (Lenke-4AN type and Lenke-5CN type) were converted into 3D models,and their finite element models were then established and verified.The internal stress distribution and displacement variation of the models were calculated by the finite element software;the correlation between the lumbosacral vertebral structure and displacement of the spine was analyzed.Results Under the same boundary conditions and load cases,the stress and displacement for two kinds of lumbosacral vertebral models showed different trends.Due to its leftleaning and forward convex bending deformation as well as the relatively large lordosis angle (60°) and smaller left-leaning angle (17.37°),the Lenke-4AN type lumbosacral spine produced slightly small forward convex displacement (8.18 mm) and relatively large left-leaning displacement (0.97 mm).The Lenke-5CN type lumbosacral spine showed left-leaning and forward convex bending deformation as well,with relatively large lordosis angle(59°) and left-leaning angle (26.97°),so it produced more severe left-leaning displacement (20.65 mm) andforward convex displacement (9.22 mm).Conclusions The deformation trend of lumbosacral vertebra is closelyrelated to its structural characteristics,and different scoliosis lumbosacral vertebral structures will cause the corre-sponding deformation trend.The research findings are important for the prevention and treatment of scoliosis.

Dynamic characteristics of the lumbosacral vertebrae based on three-dimensional finite element models / 中国组织工程研究

BACKGROUND: Inherent modal analysis and harmonic response analysis on the human normal lumbosacral vertebraehave been reported, but there is a lack of comparative research on their modal analysis results before and after pediclescrew fixation.OBJECTIVE: To explore the dynamic characteristics of human lumbosacral vertebrae using three-dimensional finiteelement method.METHODS: Finite element model of lumbosacral vertebrae (L1-S1) before and after pedicle screw fixation was developedand validated based on CT images, and the modal analysis and harmonic response analysis were then conducted.RESULTS AND CONCLUSION: (1) Representative nodes were selected at the spinous process segments of L1, L3 andL5, and numbered as A, B, and C, respectively. (2) The maximum displacement of each node in Y and Z directions oflumbosacral vertebral model after internal fixation was significantly decreased compared with those of the normallumbosacral vertebral model, suggesting that screw fixation system plays a protective role in lumbosacral vertebrae, andreduces its amplitude under external load, thus diminishing its sensitivity to external load. (3) The lumbosacral vertebralmodal analysis can provide basis for further study on dynamic analysis, and the parameters such as natural frequency,modal shape and vibration amplitude of the lumbar spine have been determined.

Age-related reference ranges of serum prostate-specific antigen in men free of prostate cancer in Beijing / 南方医科大学学报

<p><b>OBJECTIVE</b>To determine the age-related normal ranges of serum prostate-specific antigen (PSA) level in men free of prostate cancer in Beijing.</p><p><b>METHODS</b>Form April 2010 to October 2011, 1611 healthy men undergoing routine physical examinations in our hospital were enrolled and received examinations with serum PSA test, digital rectal examination and transrectal ultrasound. The men with abnormalities in any two of the three examinations were referred to a prostate biopsy. The men with normal results in any two of the examinations or with a negative biopsy finding were defined as men without prostate cancer. Men with a prior history of prostate cancer/surgery or with urinary tract infection/obstruction were excluded.</p><p><b>RESULTS</b>A total of 1572 men without prostate cancer were finally included in this study and stratified into 5 age groups, namely 40 to 49, 50 to 59, 60 to 69, 70 to 79, and older than 80 years groups. The median PSA values (95th percentile ranges) of these age groups were 0.506 (1.565), 1.04 (2.920), 1.16 (4.113), 1.34 (5.561), and 2.975(7.285), respectively, and the 25th to 75th percentiles were 0.343 to 0.923, 0.663 to 1.580, 0.693 to 2.203, 0.789 to 2.368, and 1.188 to 4.295, respectively. The serum PSA value was positively correlated with age (r=0.314, P<0.001).</p><p><b>CONCLUSION</b>Using the age-related reference ranges for PSA can increase the sensitivity for screening prostate cancer in younger men and decrease the biopsy rate in elderly patients.</p>

Hemorrhagic complications and risk factors in transrectal ultrasound-guided prostate biopsies / 中华超声影像学杂志

Objective To determine the rate of hemorrhagic complications and the possible risk factors in transrectal ultrasound(TRUS)guided prostate biopsies.Methods TRUS guided prostate biopsies were carried out in 252 patients.Chi-aquare test,t test,conditional Logistic regression were used to comparatively analyze the risk factors(age,presence of prostate cancer,the volume of prostate,arterial hypertension,diabetes mellitus,use of acetylsalicylic acid and anticoagulant,number of samples)between hemorrhagic patients and non-hemorrhagic groups.Results Hematuria was the most frequent sing in all complications,corresponding to 19.1% of the cases.According to the general feature analysis between two groups,age and the volume of the prostate were significant different.Multiple factor Loigistic regression analysis showed that patients with or without hemorrhagic complications were significant differences in age(OR=0.97,95% CI:0.942～1.000)and the volume of the prostate(OR=0.989,95% CI:0.9790～0.999).Patients with or without hematuria were significant differences in presence of prostate cancer(OR=0.479,95% CI:0.236～0.975),the volume of the prostate(OR=0.987,95% CI:0.976～0.999)and use of acetylsalicylic acid and anticoagulant(OR=3.589,95% CI:1.133～11.366).Conclusions TRUS guided prostate biopsy is a safe and effective procedure.Age and the volume of prostate are influencing factors for hemorrhagic complications.Presence of prostate cancer and the volume of prostate are influencing factors for hematuria.Use of acetylsalicylic acid and anticoagulant are risk factors for hematuria after biopsy.

The clinical study of transrectal ultrasound guided biopsies of the prostate cancer with PSA level less than 4 μg/L / 中华超声影像学杂志

Objective To evaluate the clinical value of transrectal ultrasound(TRUS)guided biopsies of the prostate cancer(PCA)with serum prostate specific antigen(PSA)level less than 4 μg/L.Methods Fifty-nine patients suspected PCA were underwent TRUS guided-biopsy.The ultrasonographic features of lesions and prostate gland were observed.The PSA,PSA density(PSAD),F/T(free/total PSA ratio),prostatic volume(PV)were compared between PCA group and non-PCA group,and further analyzed the sensitivity and specificity of PSAD and F/T at different thresholds for PCA diagnosis.Results In 59 patients,16 were proved to be cancer by pathological examination,the positive detection rate was 27%.In these 16 patients,12 had lesions on ultrasound,which locatqed in outer gland.The rich vascularity was observed in PCA more than in benign and precancerous lesion.There were statistical significant differences in PSA,PSAD,F/T,PV between PCA and non-PCA groups.When selecting threshold of PSAD and F/T were 0.09 and 0.20,respectively,there were the highest diagnostic specificity and sensitivity.The diagnostic specificity and sensitivity of PSAD were higher than those of F/T.Conclusions TRUS guided biopsies of the prostate is one of the most efficient methods for detection of PCA with PSA level less than 4μg/L.Combining TRUS features with PSA parameters can further increase positive detection rate of PCA.