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Objective To investigate the trabecular stress distributions on the cortical bone and determine whether the cancellous bone can share the load of the acetabulum with a press-fit acetabular cup. Methods The acetabulum was scanned via micro-computed tomography (CT) to build a three-dimensional micro-finite element analysis (μFEA) model of the acetabulum. The trabecular stress and strain of the bony acetabulum were calculated following total hip arthroplasty (THA) to investigate the biomechanical characteristics of their distributions. Results With the implantation of the press-fit acetabular cup into the acetabulum, the high-stress zone of the articular surface was found to be located in the pubic bone area, with a maximum stress of 1.398 MPa. The largest high-stress zone within the articular surface was at the craniomedial part where it was supported by the iliac. For the cancellous bone within the acetabulum, the high stress was relatively widely distributed on the craniomedial part. When a 1.372 kN load was applied, the high stress was found at the craniomedial and anterior-inferior parts of the articular surface where it was supported by the iliac and pubic bone, with a trabecular micro-damage occurring in the anterior-inferior part. The highest tensile stress at the craniomedial part was 0.604 MPa. For the cancellous bone within the acetabulum, the high stress was mainly distributed on the craniomedial and anterior-inferior parts. Conclusions The high stress near the periphery of the articular surface showed a three-point circular distribution, which was mainly distributed on the iliac, ischial, and pubic bone area. The stress was distributed more uniformly owing to the deformation of the cancellous bone in the acetabulum. The cancellous bone in the acetabulum has the function of load-bearing.
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Objective To quantify the stress and strain of trabecular bone with microdamage/microfracture by using micro-CT and micro-finite element (μFE) analysis, so as to investigate the effects of osteoporosis on relationship between trabecular stress and microdamage/microfracture. Methods Two cylindrical specimens of healthy and osteoporotic acetabular trabecular bones were scanned by micro-CT to build 3D μFE analysis models. The uniaxial compression on two specimens was simulated under frictionless displacement boundary condition. The trabecular stress, trabecular strain, microdamage and microfracture under different apparent strains were calculated through nonlinear μFE analysis. Results For both the healthy and osteoporotic trabeculae under apparent strain of 0.05%-0.50%, the undamaged trabecular stress was under 50 MPa, while the damaged trabecular stress was above 110 MPa. Compared with the osteoporotic trabeculae, the mean stress of the healthy trabeculae was relatively higher, but the maximum stress of the osteoporotic trabeculae was higher. Trabecular damage occurred in both the healthy and osteoporotic trabeculae, while the healthy trabeculae showed more microdamage, and microfracture occurred in the osteoporotic trabeculae. Conclusions Within the scope of apparent strain, the healthy trabeculae can withstand a higher stress with more trabecular microdamage, and microfractures might occur in the osteoporotic trabeculae under the high stress.
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Objective To study the repairing mechanism of mechanical microdamage around implants in the cortical bone of rats. Methods Thirty rats were divided into the ovariectomy group (OVX) and the sham group. At three months after the ovariectomy, a hole was drilled in the right tibial diaphysis by a metal pin. The rats were executed at 1, 2 and 4 weeks, respectively, after the hole drilling. The tetracycline and calcein labeling were performed before the execution. Bone segments containing the hole were stained with the basic fuchsin, embedded in the methylmethacrylate and cut into sections with thickness of 50 μm. Histomorphometric measurement was conducted on bone sections using Bioquant image analysis system. Results Bone resporpion cavities related to the microdamage occurred in both the OVX rats and the sham operated rats. The bone porosity and the number of bone resorption cavities were both greater in the OVX rats than that in the sham operated rats (P<0.05). In addition, the number of bone resorption cavities significantly increased with time after the surgery (P<0.05). Conclusions Increased bone porosity and resorption cavities in OVX rats may be related to the crack formation and the estrogen deficiency, which made the bone remodeling in the cortical bone of OVX rats more active. However, remarkably increased resorption cavities would reduce the bone strength and increase the risk of bone fracture.
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Objective To study the effects of mineral-collagen interfacial behavior on the microdamage progression within bone tissue. Methods Based on the finite element model, cohesive elements were introduced and the traction-separation law was used to simulate the role of ionic interactions, hydrogen bonds and van der waals forces. The effects of aforementioned interactions on the microdamage progression within bone were studied by the random field theory and probabilistic failure analysis. Results Strong interfaces (ionic interactions in both opening and sliding modes) between the mineral and collagen phases might encourage the formation of linear cracks in bone, whereas weak interfaces (van der Waals in opening mode and viscous shear in sliding mode) might facilitate the formation of diffuse damages. In addition, there existed a transitional interfacial bonding strength (hydrogen/van der Waals bonds) that governed the transition of microdamage accumulation from linear microcrack to diffuse damage.Conclusions The results from this study will help to understand the effects of mineral collagen interfacial behavior on microdamage accumulation in bone and further investigate the underlying mechanism of bone fracture due to osteoporosis or ageing.
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[Objective]To study Bone microdmage to osteoavascular epiphysis caput humeralis in teenagers of the guts outbreak mechanism and make a diagnosis and give treatment in early stage important point.[Method]The review was from 138 patients of the shoulder department ache with shoulder joint movable function obstacle that orthopedics out-patient service of 2004~2005.There was X-rays / CT,the blood bio-chemical 5 example among the teenager of the patients,it was observed by medium short-term curative effect.We was combined a related cultural heritage study,put forward to make a diagnosis and gave treatment to have the instruction meaning to the clinic of four expect to categorize a method,and to early,medium,later period the non-surgical operation treatment observation.[Result]In 138 patients,there were 5 teenager patients who were the epiphysis of head humeralis bone microdamage ON,through the function instauration was normal:Earlier period 2 cases of 1~4 weeks,middle period 2 cases of 5~8 weeks,the later period 1 case of 4~6 months.We choose the medicine of prescription with the independence,"Huo xue hua yu","Bu shen zhuanggu","Tong luo zhi tong" medicinal broth,the right amount internal use outside use,having already obtained good result.We have already observated the serious bone arthritis/canceration,resulting in serious result(in another report).[Conclusion]Once or more shoulder was bone microdamage lead the caput epiphysis humeralis occurrence ON of guts.We observe the sufferer whom had the clinical symptom,physical sign,according to the clinical performance,course of disease's long/short,imageology atc.The suggestion is divided into early,medium,night and most late four periods,for the convenience of the choice treatment measure.Because of various reason,long and non-healing cases might develop to the most later period of case,such as the avascular osteo arthritis/canceration.