The objective of this paper is to investigate the different effects of disuse and estrogen deficiency on bone loss and the underlying mechanisms.A mechanical-biological factors coupled computational model was built to simulate different patterns of bone loss induced in female rats by hind limb unloading,ovariectomy,or both in an animal study.A remodeling analysis was performed on a representative cross section of 6 mm2 of cancellous bone in the distal femoral metaphysis of the rats.The BMU activation frequency,the refilling rate,and the principal compressive strain in the state of mechanical unloading and estrogen deficiency were simulated to interpret the underlying mechanisms.Simulated bone loss patterns due to mechanical unloading,estrogen deficiency,or both all corresponded with the experimental observations.The results show that mechanical unloading and estrogen deficiency cause different bone loss patterns;moreover,mechanical unloading induces a greater degree of bone loss than estrogen deficiency,which can lead to improved treatment and prevention strategies for osteoporosis.
Objective： To evaluate the role of high risk factors in octogenarians and nonagenarians with hip trauma, which may lead to excessive mortality and morbidity postoperatively. Methods： Fifty-four octogenarians and nonagenarians patients were enrolled in the study, receiving surgical repair of hip fracture in our hospital from January 2006 to January 2010. High risk factors were recorded preoperatively in detail. Complications and survival state were followed up by telephone for 2 years postoperatively. All the data were analyzed by Chi-square test with SPSS 13.0. Results： Twenty-six males （48.1%）, aged from 80 to 94 years with a mean age of 84.2 years, and twenty-eight females （51.9%）, aged from 80 to 95 years with a mean age of 83.4 years, were presented in the cohort study. The hip traumas were caused by daily slight injuries （52 cases） and car accidents （2 cases）, respectively. Twenty-eight patients （51.9%） with femoral neck fracture while 26 patients （48.1%） with intertrochanteric fracture were diagnosed through an anterior-posterior pelvic radiophotograph. In this series, 39 patients （72.2%） suffered from one or more comorbidities preoperatively. The morbidity was 48.1% and the major cause was urinary tract infection, while a significant difference was noted between females and males. The mortality was 20.4% with a predominant cause of acute renal failure. Conclusions： The gender should be considered as a critical high risk factor in octogenarians and nonagenarians with hip trauma postoperatively. Females are more likely to suffer complications postoperatively, which is especially obvious in senile patients over 80 years （P〈0.05）. Urinary tract infection is the most frequent complication after hip surgery, followed by low limb embolism and malnutrition. The mortality is dramatically greater in patients over 80 years old than those below, and major causes are acute renal failure, multiple organ dysfunction syndrome and mental deterioration. Multidisciplinary consultatio
MA Ren-shi GU Gui-shan HUANG Xu ZHU Dong ZHANG Yu LIMing YAO Hai-yu
This paper establishes a non-linear finite element model (NFEM) of L4-L5 lumbar spinal segment with accurate three-dimensional solid ligaments and intervertebral disc. For the purpose, the intervertebral disc and surrounding ligaments are modeled with four-nodal three-dimensional tetrahedral elements with hyper-elastic material properties. Pure moment of 10 N·m without preload is applied to the upper vertebral body under the loading conditions of lateral bending, backward extension, torsion, and forward flexion, respectively. The simulate relationship curves between generalized forces and generalized displacement of the NFEM are compared with the in vitro experimental result curves to verify NFEM. The verified results show that: (1) The range of simulated motion is a good agreement with the in vitro experimental data; (2) The NFEM can more effectively reffect the actual mechanical properties than the FE model using cable and spring elements ligaments; (3) The NFEM can be used as the basis for further research on lumbar degenerative diseases.
Zhitao Xiao,1 Liya Wang,1 He Gong,1, ) Dong Zhu,2, ) and Xizheng Zhang3 1)Department of Engineering Mechanics, Jilin University, Changchun 130012, China 2)Department of Orthopaedic Trauma No.1, Hospital of Jilin University, Changchun 130012, China 3)Institute of Medical Equipment, Academy of Military Medical Sciences, Tianjin 300161, China
