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A-B The boundary conditions for the FE model are shown. The vector of the single hip force (F) with its angles in the frontal (A) and in the sagittal (B) plane are illustrated.
Source publication
The choice of the appropriate implant continues to be critical for fixation of unstable hip fractures. Therefore, the goal of this study was to develop a numerical model to investigate the mechanical performance of hip fracture osteosynthesis. We hypothesized that decreasing fracture stability results in increasing load share of the implant and the...
Similar publications
Thirteen matched pairs of cadaveric femurs were placed into two groups. In each group, a transverse fracture was created at a point 70% distal between the lesser trochanter and the adductor tubercle. One femur out of each matched pair was then stabilised with an interlocking intramedullary nail (nail only group) and the other femur was stabilised w...
Citations
... All nodes at the distal end of the femur had degrees of freedom set to 0 in all six directions, and a load of three times the body weight (2100 N) was applied above the femoral head to simulate the load generated during normal gait cycles [14]. The loading direction is shown in Fig. 4. All interfaces between the implant and the two fracture ends were considered frictional contact, and the friction coefficients between the bone-bone, bone-implant, and implant-implant were set to 0.46, 0.30, and 0.23, respectively [15][16][17]. ...
Objective
The thickness of the lateral femoral wall, which is an important indicator for evaluating the stability and integrity of intertrochanteric fractures, has been widely studied in recent years. However, as a typical representative of internal fixation treatment, there are few reports on the biomechanical comparison between PFNA and DHS + CS. This study focused primarily on the biomechanical effects of different lateral femoral wall thicknesses on two types of internal fixation through finite element analysis.
Methods
We randomly recruited a healthy adult and collected his femoral CT data to establish a model of femoral intertrochanteric fracture with different lateral femoral wall thicknesses. Following PFNA and DHS + CS fixation, femoral models were simulated, and variations in stress and displacement of the internal fixation and femoral head were recorded under the same physiological load.
Results
First, finite element mechanical analysis revealed that the stress and displacement of the internal fixation and femoral head were lower in the femoral model after PFNA fixation than in the DHS + CS model. Second, as the outer wall thickness decreased, the stress and deformation endured by both types of internal fixation gradually increased.
Conclusions
Finite element analysis determined that PFNA exhibits significantly better biomechanical stability than DHS + CS when subjected to varying lateral femoral wall thicknesses. Moreover, lateral femoral wall thickness substantially affects the stability of the two internal fixation biomechanical environments. When the thickness of the lateral femoral wall is too small, we do not recommend using extramedullary fixation because there is a significant risk of internal fixation fracture.
... Hip fracture, which grows exponentially with age, is the most severe clinical consequence of osteoporosis and causes a significant financial burden on the public health care system [1][2][3]. These fractures are linked to a 10%-20% mortality risk, functional disability, and mobility loss( [4,5]). By 2050, hip fractures will affect up to 6.3 million individuals worldwide, including 3.25 million in Asia [6]. ...
Hip fracture, increasing exponentially with age, is osteoporosis's most severe clinical consequence. Intertrochanteric fracture, one of the main types of hip fracture, is associated with higher mortality and morbidity. The current research hotspots lay in improving the treatment effect and optimizing the secondary stability after intertrochanteric fracture surgery. Cortex buttress reduction is a widely accepted method for treating intertrochanteric fracture by allowing the head-neck fragment to slide and rigidly contact the femoral shaft's cortex. Medial cortical support is considered a more effective option in treating young patients. However, osteo-degenerations features, including bone weakness and cortical thickness thinning, affect the performance of cortex support in geriatric intertrochanteric fracture treatment. Literature focusing on the age-specific difference in cortex performance in the fractured hip is scarce. We hypothesized that this osteo-19 degenerative feature affects the performance of cortex support in treating inter-trochanteric fractures between the young and the elderly. We established twenty models for the old and the young with intertrochanteric fractures and performed static and dynamic simulations under one-legged stance and walking cycle conditions. The von Mises stress and displacement on the femur, proximal femoral nail anti-rotation (PFNA) implant, fracture plane, and the cutting volume of cancellous bone of the femur were compared. It was observed that defects in the anterior and posterior cortical bone walls significantly increase the stress on the PFNA implant, the displacement of the fracture surface, and cause a greater volume of cancellous bone to be resected. We concluded that ensuring the integrity and alignment of the anterior and posterior cortical bones is essential for elderly patients, and sagittal support is recommended. This finding suggests that the treatment method for intertrochanteric fracture may differ, considering the patient's age difference.
... Future studies should consider 10-noded tetrahedral elements. A frictional contact algorithm was used for the numerical analysis with frictional coefficients of 0.46, 0.23, and 0.30 for bonebone interactions [48], implant-implant interactions [48], and bone-implant interactions [49], respectively. The contact interface between cortical and trabecular bones was considered as perfectly bonded. ...
... Future studies should consider 10-noded tetrahedral elements. A frictional contact algorithm was used for the numerical analysis with frictional coefficients of 0.46, 0.23, and 0.30 for bonebone interactions [48], implant-implant interactions [48], and bone-implant interactions [49], respectively. The contact interface between cortical and trabecular bones was considered as perfectly bonded. ...
Maintaining post-operative mechanical stability is crucial for successfully healing intertrochanteric fractures treated with the Proximal Femoral Nail Antirotation (PFNA) system. This stability is primarily dependent on the bone mineral density (BMD) and strain on the fracture. Current PFNA failure analyses often overlook the uncertainties related to BMD and body weight (BW). Therefore, this study aimed to develop a probabilistic model using finite element modeling and engineering reliability analysis to assess the post-operative performance of PFNA under various physiological loading conditions. The model predictions were validated through a series of experimental test. The results revealed a negative nonlinear relationship between the BMD and compressive strain. Conversely, the BW was positively and linearly correlated with the compressive strain. Importantly, the compressive strain was more sensitive to BW than to BMD when the BMD exceeded 0.6 g/cm ³ . Potential trabecular bone compression failure is also indicated if BMD is equal to or below 0.15 g/cm ³ and BW increases to approximately 2.5 times the normal or higher. This study emphasizes that variations in the BMD significantly affect the probability of failure of a PFNA system. Thus, careful planning of post-operative physical therapy is essential. For patients aged > 50 years restrictions on high-intensity activities are advised, while limiting strenuous movements is recommended for those aged > 65 years.
... 7,8 Simulation Parameters (Load, Mesh, and Contact Conditions) ►Fig. 2 shows the applied forces of 450, 500, 550, and 600 N considered a normal loading position, which assumes that the load vector has an angle of 8°of adduction with the hip longitudinal axis in the plane. 6,[9][10][11][12][13][14][15][16][17] In a clinical situation, both values are greater than those produced by touch support with crutches and should provide sufficient postoperative stability. 10,11 The force application frequency was 1 Hz, considering walking 1 step per second. ...
... Plate and screw contact surfaces had a friction coefficient of 0.34. 15,17 The screw and plate contacted at the surface of the screw head and the surface of the countersunk in the plate holes, all with a restriction to not allow penetration between them. As for the contacts, locked screws in plate holes were deemed connected and fixed. ...
Resumo
Objetivo: Testar a diferença do comportamento de distribuição de cargas e pressões da placa lâmina comparativamente com a placa bloqueada para osteotomia varizante do fêmur proximal através do método de elementos finitos.
Métodos: A modelagem foi realizada através do escaneamento de um fêmur esquerdo com deformidade medial em valgo fabricado em poliuretano de tamanho médio.
Resultados: Como resultados, pode-se inferir que a rigidez da placa bloqueada é maior do que a da placa lâmina. No entanto, essa diferença não foi significativa e, além disso, a placa bloqueada possui parafusos de travamento proximal para garantir que os momentos de flexão que agem nos parafusos sejam ainda menores durante o carregamento.
Conclusão: Em síntese, ambos os materiais são consagrados e eficazes para serem utilizados, porém o estudo pelo método de elementos finitos apresenta papel importante para compreendermos a situação de distribuição de cargas e pressões do implante e abre novas possibilidades para novos estudos, como, por exemplo, o estudo da proposta cirúrgica e materiais a serem implantados de forma individual e personalizada.
... It has been shown that IMNs provide sufficient stability, especially for unstable basicervical fractures and Pauwels type 3 fractures. Biomechanical studies comparing implants for femoral neck fracture fixation in young adults have focused not only on the type of implant but also on the type of fracture, which significantly affects the mechanical performance [18][19][20][21]. The use of CS systems in vertical, unstable fractures has been observed to result in earlier varus collapse [22]. ...
Background
Unstable femoral neck fractures with medial calcar defects are difficult to manage. The optimal fixation methods for these fractures have been a subject of ongoing debate among orthopedic surgeons. In this study, three different fixation techniques for vertical, medial defected femoral neck fractures were compared.
Methods
In this study, a biomechanical analysis was conducted to compare three fixation methods: cannulated screws (Group 1), cannulated screws combined with a medial buttress plate (Group 2), and intramedullary nails (Group 3). Synthetic composite bone models representing vertical collum femoris fractures with medial calcar defects were used. Each group consisted of seven specimens, and, to maintain consistency, a single surgeon performed the surgical procedure. Biomechanical testing involved subjecting the specimens to axial loading until failure, and the load to failure, stiffness, and displacement values were recorded. Normality was tested using the Shapiro–Wilk test. One-way ANOVA and Tukey’s HSD post hoc test were used for comparisons.
Results
The difference in the load to failure values was statistically significant among the groups, with Group 2 exhibiting the highest load to failure value, followed by Group 3 and Group 1. Stiffness values were significantly higher in Group 2 than in the other groups. Displacement values were not significantly different between the groups. Fracture and displacement patterns at the point of failure varied across the groups.
Conclusion
The results of this study indicate that fixation with a medial buttress plate in combination with cannulated screws provides additional biomechanical stability for vertical femoral neck fractures with medial calcar defects. Intramedullary nail fixation also demonstrated durable stability in these fractures. These findings can be used to better understand current management strategies for these challenging fractures to promote the identification of better evidence-based recommendations.
... Biomechanical studies indicate that the lesser trochanter plays a vital role in the stabilization of unstable osteoporotic intertrochanteric fractures [16] . Theoretical studies also suggest that the stress on the surface of the internal xation increases with decreasing medial stability [17] . According to Do et al., the sizes of the greater and lesser trochanteric fragments are important factors for determining stability after dynamic compression screw xation [18] . ...
Objective To investigate the clinical efficacy in the treatment of intertrochanteric fracture in conjunction with trochanter minor fracture through intramedullary nail fixation.
Methods A retrospective study was conducted in the Civil Aviation General Hospital from the records of 94 patients with intertrochanteric femur fracture from February 2017 to September 2020.According to different treatment plans, patients were divided into a study group, control group, and observation group.The 14 patients in the study group displayed intertrochanteric femur fracture with displaced fracture of the lesser trochanter that underwent intramedullary nail fixation, and fixation and reduction of the lesser trochanter. The 40 patients in the control group displayed intertrochanteric femur fracture with displaced fracture of the lesser trochanter that only underwent intramedullary nail fixation. The 40 patients in the observation group displayed intertrochanteric femur fracture without displaced fracture of the lesser trochanter that underwent intramedullary nail fixation. The operative time, intraoperative blood loss, fracture healing time, and postoperative hip joint function (Harris Hip Score, HHS) were compared in each group.
Results The operative time of the study group was longer than the control group; the amount of intraoperative blood loss in the study group was more than the control group; the fracture healing time in the study group was shorter than the control group; the HHS of postoperative hip joint function in the study group was better than the control group; the differences were statistically significant (P<0.05). The operative time of the study group was longer than the observation group; the amount of intraoperative blood loss in the study group was more than the observation group; the fracture healing time in the study group was shorter than the observation group; the HHS of postoperative hip joint function in the study group was better than the observation group; the differences were statistically significant (P<0.05).
Conclusion In the treatment of intertrochanteric fracture in combination with trochanter minor fractures, with or without displacement of the lesser trochanter, reduction and fixation of the lesser trochanter are recommended to promote fracture healing and functional recovery and should be applied and promoted in clinical practices.
... Previous reports have suggested several reasons why IMN is preferred for plate fixation in AFFs. First, from a mechanical aspect, IMN has advantages, including a better load-sharing capacity and less bending moment owing to its more medial location compared to plate fixation [15,16]. Thus, devices with greater load sharing have an advantage in AFFs in terms of early ambulation in elderly patients. ...
The atypical femoral fracture (AFF) has been attracting significant attention because of its increasing incidence; additionally, its treatment is challenging from biological and mechanical aspects. Although surgery is often required to manage complete AFFs, clear guidelines for the surgical treatment of AFFs are currently sparse. We reviewed and described the surgical treatment of AFFs and the surveillance of the contralateral femur. For complete AFFs, cephalomedullary intramedullary nailing spanning the entire length of the femur can be used. Various surgical techniques to overcome the femoral bowing common in AFFs include a lateral entry point, external rotation of the nail, and the use of a nail with a small radius of curvature, or a contralateral nail. In the case of a narrow medullary canal, severe femoral bowing, or pre-existing implants, plate fixation may be considered as an alternative. For incomplete AFFs, prophylactic fixation depends on several risk factors, such as a subtrochanteric location, presence of a radiolucent line, functional pain, and condition of the contralateral femur; the same surgical principles as those in complete AFFs can be applied. Finally, once AFF is diagnosed, clinicians should recognize the increased risk of contralateral AFFs, and close surveillance of the contralateral femur is recommended.
... They are a significant contributor to old age impairment. These fractures are linked to functional impairment, decreased mobility, and loss of independence [4] . While sliding hip screws (SHS) are typically used to treat stable intertrochanteric fractures, unstable fractures still provide a difficulty due to the wide range of implant options and fewer specific indications, as well as mechanical complication rates that can reach 20% [4][5][6][7] . ...
... These fractures are linked to functional impairment, decreased mobility, and loss of independence [4] . While sliding hip screws (SHS) are typically used to treat stable intertrochanteric fractures, unstable fractures still provide a difficulty due to the wide range of implant options and fewer specific indications, as well as mechanical complication rates that can reach 20% [4][5][6][7] . The PFLCP (proximal femoral locking compression plates) have some biomechanical advantages, intramedullary implants are typically chosen for the fixation of unstable fractures [5,6] . ...
... While using percutaneous plating to treat unstable trochanteric fractures, this complication has not yet been documented. Locking plates with lateral wall buttresses are helpful for keeping unstable fractures reduced [4,7] . Infection, non-union, malunion, decubitus ulcers, fat emboli, deep vein thrombosis, pulmonary embolism, pneumonia, myocardial infarction, stroke, and mortality are complications related to these injuries that result in substantial morbidity. ...
... The Young's modules and Poisson's ratio of the LCP, caps and screws were consisted with Ti 6 Al 4 V (113000 MPa, 0.34) (Collings, 1994). The following friction coefficients were applied to contact surfaces: 0.3 between the bone and LCP (Lu et al., 2020), 0.46 for bone-bone interactions (Eberle et al., 2009), and 0.23 between locking caps and the LCP (Zeng et al., 2020). Bone-screw interfaces were assumed to be fully fixed and contact surfaces between the screws and locking caps were tied. ...
Locking compression plates (LCP) with asymmetrical holes and polyaxial screws are effective for treating mid-femoral fractures, but are prone to failure in cases of bone nonunion. To understand the failure mechanism of the LCP, this study assessed the material composition, microhardness, metallography, fractography and biomechanical performance of a retrieved LCP used for treating a bone fracture of AO type 32-A1. For the biomechanical assessment, a finite element surgical model implanted with the intact fixation-plate system was constructed to understand the stresses and structural stiffness on the construct. Also, to avoid positioning screws around the bone fracture, different working lengths of the plate (the distance between the two innermost screws) and screw inclinations (±5°, ±10° and ±15°) were investigated. The fracture site of the retrieved LCP was divided into a narrow side and broad side due to the asymmetrical distribution of holes on the plate. The results indicated that the chemical composition and microhardness of the LCP complied with ASTM standards. The fatigue failure was found to originate on the narrow side of the hole, while the broad side showed overloading characteristics of crack growth. When the screws were inserted away from the region of the bone fracture by increasing the working length, the stress of the fixation-plate system decreased. Regardless of the screw insertion angle, the maximum stress on the LCP always appeared on the narrow side, and there was little change in the structural stiffness. However, angling the screws at -10° resulted in the most even stress distribution on the fixation-plate system. In conclusion, the LCP assessed in this study failed by fatigue fracture due to bone nonunion and stress concentration. The narrow side of the LCP was vulnerable to failure and needs to be strengthened. When treating an AO type 32-A1 fracture using an LCP with asymmetrical holes and polyaxial screws, inserting the screws at -10° may reduce the risk of implant failure and positing screws around the fractured area of the bone should be avoided.
... This effect is more pronounced in cases treated with DHS devices, where the inability to restore the posteromedial fragment has been linked with high failure rates [ 27 , 41 ]. From a biomechanical perspective the integrity of the posteromedial wall allows the fixation device to act as a load sharing device, transferring compressive loads via the cortical bone on the medial side and tensile loads via the implant on the lateral side [42] . ...
Background
Despite recent advances in implants and surgical techniques, catastrophic and clinical failures in the treatment of intertrochanteric fractures continue to occur, with dire consequences in an overall frail population subset. The aim of the current study is to evaluate the effect of the factors under the surgeons’ control, namely fracture reduction and implant selection, on the biomechanical behavior of fracture fixation constructs.
Material-Methods
An experimental protocol was conducted with the use of instrumented sawbones, in order to validate the finite element models. The implants used were the Gamma3®and DHS systems. Subsequently, a series of scenaria were considered, including various reduction and implant angle combinations. Data were retrieved concerning the peak cancellous bone stresses around the hip screw and the volume of cancellous bone in the femoral head stressed at critical levels, as well as implant stresses and stresses on the cortical bone of the distal fragment.
Results
All stable fracture models displayed significantly decreased cancellous bone stresses and implant stresses compared to their unstable counterparts, regardless of implant used. The effect of increasing implant angle led to a decrease in implant stresses in all models studied, but had a beneficial effect on the stresses in the cancellous bone of the proximal fragment only in the subgroups of stable fractures with both implants and unstable fractures treated with a cephalomedullary nail (CMN). In unstable fractures anatomically reduced, the use of CMN led to significantly lower peak stresses in the cancellous bone and a smaller volume of bone stressed at critical levels. Increasing the reduction angle by 5 degrees led to a significant decrease in both peak stresses and volume of bone stressed at critical levels, more prominent in the sliding hip screw (SHS) models. Decreasing the reduction angle into varus by 5 or 10 degrees led to a significant increase in bone and implant stresses regardless of implant used.
Conclusions
In stable two-part (AO31.A2) fractures the use of the SHS appears to be biomechanically equivalent to CMN. In unstable, anatomically reduced fractures, the use of CMN leads to significantly reduced cancellous bone stresses and decreased rotation of the proximal fragment during loading.
A reduction in varus should be avoided at all costs. In unstable fractures treated with SHS a reduction in slight valgus appears to be biomechanically beneficial. The highest implant angle that allows for proper screw position and trajectory in the femoral head should be used for stable fractures with both implants and unstable fractures treated with Gamma3®.
