Coronal shear fractures of the femoral neck (CSFF) are the most challenging to treat among proximal femur fractures, directly affecting the life expectancy of patients with osteoporosis. However, an adequate osteosynt...Coronal shear fractures of the femoral neck (CSFF) are the most challenging to treat among proximal femur fractures, directly affecting the life expectancy of patients with osteoporosis. However, an adequate osteosynthesis method has not been elucidated yet. This study investigated the displacement direction of the femoral head fragment and its effect on the bone using finite element method. A finite element model for CSFF was developed from CT image data of a patient with osteoporosis using Mechanical Finder (ver. 11). Subsequently, finite element analyses were performed on six osteosynthesis models under maximum load applied during walking. The compressive stresses, tensile stresses, and compressive strains of each model were examined. The results suggested that the compressive and tensile stress distributions were concentrated on the anterior side of the femoral neck. Compressive strain distribution in the femoral head and neck was concentrated in four areas: at the tip of the blade or lag screw, the anteroinferior side of the blade or lag screw near the fracture site, and the upper right and lower left near the junction of the blade or lag screw and nail. Thus, the distribution of both these stresses revealed that the femoral head fragment was prone to anterior and inferior displacement. Distribution of compressive strains revealed the direction of the stress exerted by the osteosynthetic implant on the bone. The same results were observed in all osteosynthetic implants;thus, the findings could lay the foundation for developing methods for placing osteosynthetic implants less prone to displacement and the osteosynthetic implants themselves. In particular, the study provides insight into the optimal treatment of CSFF.展开更多
Plate and screw constructs are routinely used in the treatment of long bone fractures. Despite considerable advancements in technology and techniques, there can still be complications in the healing of long bone fract...Plate and screw constructs are routinely used in the treatment of long bone fractures. Despite considerable advancements in technology and techniques, there can still be complications in the healing of long bone fractures. Non-unions, delayed unions, and hardware failures are common complications observed in clinical practice following open reduction and internal fixation of fractures [1]. Potential causes of these adverse clinical effects may be disruptive to the periosteal and endosteal blood supply, stress shielding effects, and inadequate mechanical stability. The goal of the present study was to explore the effect of screw position on the fracture healing and formation of new bone tissue with mechanoregulatory algorithms in a computational model. An idealized poroelastic 3D finite element (FE) model of a femur with a 5 mm fracture gap, including a plate-screw construct was developed. Nineteen different plate-screw combinations, created by varying the number and position of screws within the plate, were created to identify a construct with the most favourable attributes for fracture healing. The first phase of the study evaluated constructs through mechanical stress analyses to identify those constructs with high loadsupport capability. The second phase of the study evaluated healing and bone formation with a biphasic mechanoregulatory algorithm to simulate tissue differentiation for fixation within selected constructs. The results of our analysis demonstrated a 4-screw symmetrical construct with the largest distance between screws to provide the most favourable balance of stability and optimized conditions to promote fracture healing.展开更多
Background:Refractory femoral neck fractures cannot be anatomically reduced by closed traction reduction which may affect fracture healing.We evaluated the biomechanical effects of positive,negative,and anatomic reduc...Background:Refractory femoral neck fractures cannot be anatomically reduced by closed traction reduction which may affect fracture healing.We evaluated the biomechanical effects of positive,negative,and anatomic reduction of various degrees of displacement in Pauwels I femoral neck fractures by a finite element analysis.Methods:Five reduction models of Pauwels type I femoral neck fracture were established using the Mimics 17.0(Materialize,Leuven,Belgia)and Hypermesh 12.0(Altair Engineering,Troy,MI,USA).According to the degree of fracture displacement,there were three models of positive support,an anatomic reduction model,and a negative 2mm reduction model.Finite element analysis was conducted using the ABAQUS 6.9 software(Simulia,Suresnes,France).The von Mises stress distribution and the stress peak of internal fixation in different models,the displacement between fracture blocks,and the principal strain of the femoral neck cancellous bone model were recorded under the axial stress of 2100 N.Results:The peak von Mises stress on screw of each model was located at the thread of the screw tip.The peak von Mises stress was the lowest at the tip of the anatomic reduction model screw(261.2 MPa).In the positive 4mm model,the von Mises stress peak was the highest(916.1 MPa).The anatomic reduction model showed the minimum displacement(0.388 mm)between fracture blocks.The maximum displacement was noted in the positive 4mm model(0.838 mm).The displacement in the positive 3mm model(0.721 mm)was smaller than that in the negative 2mm model(0.786 mm).Among the five models,the strain area of the femoral neck cancellous bone was mainly concentrated around the screw hole,and the area around the screw hole could be easily cut.Conclusions:Compared with negative buttress for femoral neck fracture,positive buttress can provide better biomechanical stability.In Pauwel type I fracture of femoral neck,the range of positive buttress should be controlled below 3mm as far as possible.展开更多
The number and spatial configuration of the screws will affect the stability and prognosis of the fractures.In our study,we assessed the biomechanical effects of the double-head cannulated compression screw(DhCCS)and ...The number and spatial configuration of the screws will affect the stability and prognosis of the fractures.In our study,we assessed the biomechanical effects of the double-head cannulated compression screw(DhCCS)and ordinary cannulated compression screw(OCCS)for the treatment of femoral neck fractures by using computer finite element analysis.The original digital imaging and communications in medicine(DICOM)data of a proximal femur were imported into Materialise’s interactive medical image control system(MIMICS)software for modeling.Both DhCCS and OCCS 3D-models were obtained by using the 3D scan technique.Using the fracture model and internal fixation assembly model with an inverted triangle,two horizontal and vertical distribution were established in UG software.Next,the displacement and stress distribution were calculated in ANSYS software.The displacement value of the femoral head in the DhCCS group was smaller than that in the OCCS group,and the displacement value in the two horizontal groups was smaller than that in the vertical group.The stress distribution in the DhCCS group was concentrated on the screw rod at the fracture block and thread end,while only at the fracture block in the OCCS group.The stress in the horizontal group was more dispersed on the screws than that in the vertical group.DhCCS has reliable stability for the fixation of femoral neck fractures and applied in the clinical work and 2 horizontal fixation can be used when two screws are selected.展开更多
目的验证基于临床CT的数字体相关(digital volume correlation,DVC)方法在测量股骨内部变形场时的准确性,并通过DVC进一步测量股骨在跌倒情况下的内部变形,验证基于临床CT的有限元分析方法(finite element analysis,FEA)在计算股骨内部...目的验证基于临床CT的数字体相关(digital volume correlation,DVC)方法在测量股骨内部变形场时的准确性,并通过DVC进一步测量股骨在跌倒情况下的内部变形,验证基于临床CT的有限元分析方法(finite element analysis,FEA)在计算股骨内部变形场的准确性。方法使用猪股骨,模拟侧向跌倒姿态,进行分步力学加载实验,同步进行多次CT成像。通过重复扫描和虚拟位移验证DVC方法的准确性。DVC以子体积作为配准两组图像的研究对象,分别设置8、12、16和20 mm的子体积进行测试。量化误差指标包括位移系统误差-平均值(mean)、位移随机误差-标准差(standard deviation,SD)、应变准确度-平均绝对误差(mean absolute error,MAER)和应变精确度-标准差误差(standard deviation of the error,SDER)。基于CT图像建立股骨有限元模型,模拟实验条件,计算股骨内部位移,与DVC测量的内部变形场对比验证。结果基于临床CT的DVC方法重复扫描位移偏差小于0.013 mm,MAER和SDER均小于200με;虚拟位移偏差小于0.098 mm,MAER为1093~1687με,SDER为604~1267με,远小于骨组织屈服应变。FEA计算的位移和DVC测量的位移之间具有较强的相关性(R^(2)≥0.76,P<0.05)。结论基于临床CT的DVC方法可以准确测量股骨内部变形场,并且基于临床CT的有限元模型可以准确计算股骨内部变形场。展开更多
文摘Coronal shear fractures of the femoral neck (CSFF) are the most challenging to treat among proximal femur fractures, directly affecting the life expectancy of patients with osteoporosis. However, an adequate osteosynthesis method has not been elucidated yet. This study investigated the displacement direction of the femoral head fragment and its effect on the bone using finite element method. A finite element model for CSFF was developed from CT image data of a patient with osteoporosis using Mechanical Finder (ver. 11). Subsequently, finite element analyses were performed on six osteosynthesis models under maximum load applied during walking. The compressive stresses, tensile stresses, and compressive strains of each model were examined. The results suggested that the compressive and tensile stress distributions were concentrated on the anterior side of the femoral neck. Compressive strain distribution in the femoral head and neck was concentrated in four areas: at the tip of the blade or lag screw, the anteroinferior side of the blade or lag screw near the fracture site, and the upper right and lower left near the junction of the blade or lag screw and nail. Thus, the distribution of both these stresses revealed that the femoral head fragment was prone to anterior and inferior displacement. Distribution of compressive strains revealed the direction of the stress exerted by the osteosynthetic implant on the bone. The same results were observed in all osteosynthetic implants;thus, the findings could lay the foundation for developing methods for placing osteosynthetic implants less prone to displacement and the osteosynthetic implants themselves. In particular, the study provides insight into the optimal treatment of CSFF.
文摘Plate and screw constructs are routinely used in the treatment of long bone fractures. Despite considerable advancements in technology and techniques, there can still be complications in the healing of long bone fractures. Non-unions, delayed unions, and hardware failures are common complications observed in clinical practice following open reduction and internal fixation of fractures [1]. Potential causes of these adverse clinical effects may be disruptive to the periosteal and endosteal blood supply, stress shielding effects, and inadequate mechanical stability. The goal of the present study was to explore the effect of screw position on the fracture healing and formation of new bone tissue with mechanoregulatory algorithms in a computational model. An idealized poroelastic 3D finite element (FE) model of a femur with a 5 mm fracture gap, including a plate-screw construct was developed. Nineteen different plate-screw combinations, created by varying the number and position of screws within the plate, were created to identify a construct with the most favourable attributes for fracture healing. The first phase of the study evaluated constructs through mechanical stress analyses to identify those constructs with high loadsupport capability. The second phase of the study evaluated healing and bone formation with a biphasic mechanoregulatory algorithm to simulate tissue differentiation for fixation within selected constructs. The results of our analysis demonstrated a 4-screw symmetrical construct with the largest distance between screws to provide the most favourable balance of stability and optimized conditions to promote fracture healing.
基金This study was partially supported by a grant from the Zhejiang Medical Science Foundation of China(No.2019KY682).
文摘Background:Refractory femoral neck fractures cannot be anatomically reduced by closed traction reduction which may affect fracture healing.We evaluated the biomechanical effects of positive,negative,and anatomic reduction of various degrees of displacement in Pauwels I femoral neck fractures by a finite element analysis.Methods:Five reduction models of Pauwels type I femoral neck fracture were established using the Mimics 17.0(Materialize,Leuven,Belgia)and Hypermesh 12.0(Altair Engineering,Troy,MI,USA).According to the degree of fracture displacement,there were three models of positive support,an anatomic reduction model,and a negative 2mm reduction model.Finite element analysis was conducted using the ABAQUS 6.9 software(Simulia,Suresnes,France).The von Mises stress distribution and the stress peak of internal fixation in different models,the displacement between fracture blocks,and the principal strain of the femoral neck cancellous bone model were recorded under the axial stress of 2100 N.Results:The peak von Mises stress on screw of each model was located at the thread of the screw tip.The peak von Mises stress was the lowest at the tip of the anatomic reduction model screw(261.2 MPa).In the positive 4mm model,the von Mises stress peak was the highest(916.1 MPa).The anatomic reduction model showed the minimum displacement(0.388 mm)between fracture blocks.The maximum displacement was noted in the positive 4mm model(0.838 mm).The displacement in the positive 3mm model(0.721 mm)was smaller than that in the negative 2mm model(0.786 mm).Among the five models,the strain area of the femoral neck cancellous bone was mainly concentrated around the screw hole,and the area around the screw hole could be easily cut.Conclusions:Compared with negative buttress for femoral neck fracture,positive buttress can provide better biomechanical stability.In Pauwel type I fracture of femoral neck,the range of positive buttress should be controlled below 3mm as far as possible.
基金This research was supported by the health and family planning commission of chongqing under grant 2016MSXM162.
文摘The number and spatial configuration of the screws will affect the stability and prognosis of the fractures.In our study,we assessed the biomechanical effects of the double-head cannulated compression screw(DhCCS)and ordinary cannulated compression screw(OCCS)for the treatment of femoral neck fractures by using computer finite element analysis.The original digital imaging and communications in medicine(DICOM)data of a proximal femur were imported into Materialise’s interactive medical image control system(MIMICS)software for modeling.Both DhCCS and OCCS 3D-models were obtained by using the 3D scan technique.Using the fracture model and internal fixation assembly model with an inverted triangle,two horizontal and vertical distribution were established in UG software.Next,the displacement and stress distribution were calculated in ANSYS software.The displacement value of the femoral head in the DhCCS group was smaller than that in the OCCS group,and the displacement value in the two horizontal groups was smaller than that in the vertical group.The stress distribution in the DhCCS group was concentrated on the screw rod at the fracture block and thread end,while only at the fracture block in the OCCS group.The stress in the horizontal group was more dispersed on the screws than that in the vertical group.DhCCS has reliable stability for the fixation of femoral neck fractures and applied in the clinical work and 2 horizontal fixation can be used when two screws are selected.
文摘目的验证基于临床CT的数字体相关(digital volume correlation,DVC)方法在测量股骨内部变形场时的准确性,并通过DVC进一步测量股骨在跌倒情况下的内部变形,验证基于临床CT的有限元分析方法(finite element analysis,FEA)在计算股骨内部变形场的准确性。方法使用猪股骨,模拟侧向跌倒姿态,进行分步力学加载实验,同步进行多次CT成像。通过重复扫描和虚拟位移验证DVC方法的准确性。DVC以子体积作为配准两组图像的研究对象,分别设置8、12、16和20 mm的子体积进行测试。量化误差指标包括位移系统误差-平均值(mean)、位移随机误差-标准差(standard deviation,SD)、应变准确度-平均绝对误差(mean absolute error,MAER)和应变精确度-标准差误差(standard deviation of the error,SDER)。基于CT图像建立股骨有限元模型,模拟实验条件,计算股骨内部位移,与DVC测量的内部变形场对比验证。结果基于临床CT的DVC方法重复扫描位移偏差小于0.013 mm,MAER和SDER均小于200με;虚拟位移偏差小于0.098 mm,MAER为1093~1687με,SDER为604~1267με,远小于骨组织屈服应变。FEA计算的位移和DVC测量的位移之间具有较强的相关性(R^(2)≥0.76,P<0.05)。结论基于临床CT的DVC方法可以准确测量股骨内部变形场,并且基于临床CT的有限元模型可以准确计算股骨内部变形场。
