Finite Element Analysis of Proximal Femur Bionic Nail (PFBN), Froximal Femoral Anti-rotation Intramedullary Nail and InterTan for Treatment of Reverse Obliquity Intertrochanteric Fractures

Finite Element Analysis of Proximal Femur Bionic Nail (PFBN), Froximal Femoral Anti-rotation Intramedullary Nail and InterTan for Treatment of Reverse Obliquity Intertrochanteric Fractures | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Finite Element Analysis of Proximal Femur Bionic Nail (PFBN), Froximal Femoral Anti-rotation Intramedullary Nail and InterTan for Treatment of Reverse Obliquity Intertrochanteric Fractures Chen Xiong, Lijia Zhang, Yanhua Wang, Wei Chen, Xiaomeng Zhang, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-1837198/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background: Reverse intertrochanteric fracture is an unstable type of fracture. Current guidelines recommend intramedullary fixation, but there are still complications such as screw removal, hip varus, nail withdrawal, and nail fracture. The objective of this study was to use finite element analysis to compare the biomechanical properties of the novel proximal femoral bionic intramedullary nail (PFBN), proximal femoral anti-rotation intramedullary nail (PFNA) and combined compression interlocking intramedullary nail (InterTan) in the treatment of reverse obliquity intertrochanteric fractures [AO/OTA 31-A3.1]. Methods: The three-dimensional models of PFBN, PFNA, InterTan and the A3.1 intertrochanteric fracture model were established by using modeling software such as Mimics and Unigraphics. Different force loads were implemented using ANSYS software to compare finite element biomechanical parameters, such as maximum stress in the implant and maximum stress and displacement at the proximal femur. Results: In this finite element study, we found that the distribution trend of maximum femoral stress and displacement in the femoral model of the three internal fixation groups was similar, but the maximum stress and maximum displacement were the lowest in the PFBN group, and the maximum stress of the internal fixation implant in PFBN group was lower than that in the PFNA group and the InterTan group. The maximum stress and displacement of the femur in the PFNA group were 403.71MPa and 14.274mm, the maximum stress and displacement in the InterTan group were 362.72MPa and 10.678mm, and the maximum stress and displacement in the PFBN group were 186.23MPa and 9.7068mm.In the internal fixation implant model, the maximum stress of the PFNA group was 1445MPa, the maximum stress of the InterTan group was 919.62 MPa, and the maximum stress of the PFBN group was the lowest, 911.77MPa. Conclusion: Compared with PFNA and InterTan, PFBN designed by the lever - fulcrum - reconstruction theory can provide better biomechanical stability. It is a feasible choice for the future treatment of reverse intertrochanteric fracture. Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Background Femoral Intertrochanteric fracture is one of the common causes of death and disability in the elderly. Falls and indoor activity injuries are the most common causes of injury. Given the name of "the last fracture in the life of the elderly", this type of fracture affects approximately 750,000 people worldwide each year with an annual mortality rate up to 37%[1-5].The surgical treatment of intertrochanteric fractures has evolved from the previous extramedullary fixation to the current intramedullary fixation. Although the treatment has been constantly improving[6], complications have always existed, which makes them hard to be ignored. Among the subtypes of intertrochanteric fractures, A3 type fractures accounts for 10% to 34% of all intertrochanteric fractures[2, 7, 8], which is characterized by the simultaneous involvement of medial wall and lateral wall. It is classified as unstable intertrochanteric fractures due to the characteristics including difficult reduction, hard reduction maintenance, etc. Although the American Association of Orthopedic Surgery (AAOS) recommends intramedullary nailing for the treatment of type A3 intertrochanteric fractures, the failure rate after internal fixation is up to 30%[9-11], and the incidence of complications was significantly higher than those of A1 and A2 fractures. Previous studies emphasize the importance of the integrity of lateral or medial wall on postoperative stability. Due to the unique fracture morphology of this fracture subtype, it cannot acquire complete medial or lateral wall support after fixation. Thus, stable internal fixation is not obtained, and postoperative internal fixation failure happens. The theory of "lever - balance - reconstruction" put forward by Prof. Zhang gives new enlightenment to the reduction and fixation of intertrochanteric fractures. According to the theory, the pressure trabecula and tension trabecula within proximal femur under physiological condition form a structure similar to that of lever. Its fulcrum is located near the center of femoral head. The pressure arm of medial femur is short, and the lateral arm is long. Thus, the proximal femur can bear large compressive stress. After fractures, the original lever system is destroyed, and the internal fixation system establishes a new lever system to replace the original lever system until fracture healing. Postoperative stability depends on the stability of the internal fixation and has nothing to do with the structure of internal or external wall[12, 13]. The proximal femur bionic nail (PFBN) derived from this theory includes a main nail, a pressure nail and a tension nail[14]. Through the combination of the tension nail and the pressure nail, the reconstructed fulcrum of the fixation system is very close to the anatomical fulcrum, which makes the fixed proximal femur effective in counteracting the compressive stress generated during postoperative weight-bearing and thus offer better stability to the fixation system. Theoretically, it is suitable for all types of intertrochanteric fractures. Preliminary finite element analysis and biomechanical tests have confirmed that PFBN has a greater advantage in the treatment of traditionally stable intertrochanteric fractures than proximal femoral rotation intramedullary nail (PFNA) and InterTan. It is more effective in the prevention of complications, such as internal fixation of fracture, hip varus and shortening of the femoral head shift, screw cutout. In this study, the biomechanical characteristics of PFBN, PFNA and InterTan in the treatment of AO-OTA 31-A3.1 type intertrochanteric fracture were analyzed by finite element analysis to further study the mechanical properties of PFBN and to provide a new idea for the treatment and study of elder intertrochanteric fracture. Methods 1. Establishment of fracture model The femoral CT images of an elderly woman (65 years old, 168cm, 53Kg, no femoral disease) were selected, which were imported into Mimics 21.0 (Materialise, Leuven, Belgium) software. The femur 3D model was established through threshold segmentation, region growth, space filling and other steps to complete the smooth treatment of the surface. According to the fracture characteristics of AO/OTA 31-A3.1, the model was segmented to establish the fracture model(Figure 1). 2. Establishment of intramedullary nailing model According to the dimensions of the intramedullary nails provided by the manufacturers, the 3D geometric models of intramedullary nail were established via Unigraphics NX 12.0 (Siemens PLM Software). The assemblies of the intramedullary nail models were completed before export of the geometric files(Figure 2). 3. Model assembly The three-dimensional femoral model and the intramedullary nail models were imported into 3-matic. According to the manufacturer's instructions, the position of intramedullary nail system was adjusted via rotation and translation function to make it consistent with the surgical fixation position. A circular region of 30mm diameter above femoral head was divided as the loading surface. The fixation surface is defined as the 40mm high area at the base of femoral condyle. 4. Meshing The mesh size of the model was set as 1.5mm in 3-matic. The mesh quality was checked and optimized, and the second-order decahedral mesh (Solid187) was generated based on surface mesh(Model was meshed like Figure 3, and number of nodes and units of each model was shown in Table 1). Table 1: Number of nodes and units divided by Meshing Mesh Normal PFNA InterTan PFBN Number of nodes 20636 325170 347236 324130 Number of units 152280 217101 228819 214458 5. Material properties The volume mesh file was imported into Mimics, and values were assigned to the model based on the gray values. According to the method recommended in previous literature, the Young's moduli of cortical bone and cancellous bone were set as 17Gpa and 445MPa, and the Poisson's ratios were set as 0.3 and 0.2; the Young's modulus of implant was set as 113800MPa, and the Poisson's ratio was set as 0.342[15, 16].(Table 2) Table 2: Material properties of bone and internal fixation Part Component Young 's modulus (MPa) Poisson 's ratio Bone Cortical bone 17000 0.3 Cancellous bone 445 0.2 Implant Nail & Screw(TI6Al4V) 113800 0.342 6. Calculation Import the ANSYS processing file into ANSYS Workbench 2020R2 and set the contact conditions (friction contact, bone-to-bone friction coefficient 0.46, bone-to-nail friction coefficient 0.42, nail to nail internal friction coefficient 0.2)[15]. Referring to similar studies[17], in order to simulated the different stages of gradual loading under the fracture, loading condition was set as 2100N, divided into seven steps, and the direction was downward of normal standing Angle. A diameter range of 30mm above the femoral head was set as the loading surface(Figure 4), and the restriction surface at the femoral condyle was set for full fixation. 7. Observation index The VonMises stress and displacement of the whole femur were extracted. The Von Mises stress distribution of the intramedullary nailing system was obtained under 7 equal-spacing loading conditions from 300N to 2100N. Results 1. Femoral displacement distribution The figure(Figure 5) shows the femoral displacement distributions of regular femur model and A3.1 intertrochanteric fracture model integrated with three different internal fixations under a load of 2100N. It can be seen that the maximum displacement of regular femur was concentrated at the region near the loading point of femoral head followed by intertrochanter, subtrochanter, femoral shaft and distal femur as the regions with subsequential large displacement, respectively. In addition, there was another area with relatively large displacement at greater trochanter. The displacement trends of the fractured femur model with three different internal fixations were similar to that of regular femur model. Among these models, the PFBN group had the smallest maximum displacement of 9.7068mm; the InterTan group had the maximum displacement of 10.678mm; the PFNA group had the largest maximum displacement of 14.274mm. 2. Stress distribution of femur This figure(Figure 6) shows the femoral stress distributions of regular femur model and the fracture model assembled with three different internal fixations under a load of 2100 N. It was found that the maximum stress of regular femur was located at subtrochanteric inner cortex. The maximum stress of the PFNA group was distributed at the intersection of the helical blade and outer cortex bone with a value of 403.71MPa. The maximum stress of the InterTan group was 362.72 MPa, which was distributed at the intersection of the compression screw and the main nail. The maximum stress of the PFBN group was the lowest among those of the three groups, which was distributed at the intersection of the pressure nail and lateral cortex with a value of 186.23MPa. 3. Stress distribution of proximal femoral head In all the three groups in Figure 7, there was relative stress concentration at the interface between cancellous bone and head screw. The local maximum stress of the PFBN group was the smallest (19.344MPa), which occurred at the tip of the pressure nail. The maximum stresses of the PFNA and InterTan groups were 32.761MPa and 28.111 MPa, and the locations were the tips of the helical blade and one of the twin screws, respectively. 4. Stress distribution of proximal fracture fragment The figure(Figure 8) shows the stress distributions of the proximal fracture blocks under a load of 2100N. It can be seen that the maximum stresses were all distributed at the junction of internal fixator and fracture surface. In the PFNA group, the maximum stress was 102.3MPa at the position of the helical blade near and the main nail. The maximum stress of the InterTan group was 64.797MPa at the junction of the compression screw and the main nail. The maximum stress of the PFBN group was 46.644 MPa with the location the same as that of the InterTan group. 5. Stress distribution of inner plants 5.1 PFNA internal fixation stress distribution Table 3: Stress values at each point of PFNA internal fixation Unit: MPa 300N 600N 900N 1200N 1500N 1800N 2100N Position 1 27.313 54..94 82.138 109.15 135.64 161.92 188.300 Position 2 188.860 377.410 570.820 775.190 986.550 1208.300 1445.000 Position 3 289.42 550.42 713.03 807.13 840.73 878.82 965.58 5.2 Internal Fixed Stress Distribution of InterTan Table 4: Stress values at each point of InterTan internal fixation Unit: MPa 300N 600N 900N 1200N 1500N 1800N 2100N Position 1 12.508 24.526 36.144 47.636 59.059 70.278 81.335 Position 2 148.310 290.450 432.270 574.230 711.210 823.920 919.620 Position 3 43.953 84.271 123.280 162.990 203.510 245.000 354.330 5.3 PFBN internal fixed stress distribution Table 5: Stress values at each point of PFBN internal fixation Unit: MPa 300N 600N 900N 1200N 1500N 1800N 2100N Position 1 29.023 57.941 87.439 117.82 149.94 185.16 222.41 Position 2 131.86 256.38 382.06 510.76 640 773.71 911.77 Position 3 47.837 93.648 138.38 178.93 217.89 252.66 285.79 Position 4 40.453 82.013 123 163.08 201.07 237.02 270.26 Position 5 22.201 44.671 66.132 86.626 106.17 125.07 143.26 Position 6 0.66951 1.3359 1.9981 2.6542 3.306 3.9605 4.6268 As shown in the figures above(Figure 9-14, Table 3-5), the maximum stresses of the three groups were located at the intersections of the main nail and the pressure/helical blade/twin screw. We found that the maximum stresses of the three groups of internal fixation model were increased linearly with the increase of the applied stress. Under the condition of 2100N, the maximum stress of the PFNA group was 1445 MPa; the maximum stress of the InterTan group was 919.62 MPa; the maximum stress of the PFBN group was 911.77 MPa, which was the lowest among those of the three groups. Discussion AO/OTA 31-type A3 femoral intertrochanteric fractures has its unique characteristics. Different from A1 and A2 types of fracture, the direction of its intertrochanteric fracture line extends from the superior medial side of proximal lesser trochanter to the inferior lateral side of greater trochanter, and both the inner and outer side walls are involved. Furthermore, the fracture line often spread to upper femur. All of these traits make it as unstable fractures. Compared with type A1 and A2 intertrochanteric fractures, type A3 fractures has higher occurrence of complications including screw cutout, hip varus deformity, nail withdraw, internal fixation failure, etc. These ultimately lead to fracture nonunion or malunion. High-energy damage often causes comminuted fracture, making the reduction and biomechanical stability as the key to the treatment of type A3 intertrochanteric fracture. In this study, the biomechanical properties of PFBN, PFNA and InterTan in the treatment of AO/OTA 31-A3 intertrochanteric fractures in elderly were compared using the model of A3.1 fracture for fracture model construction. Previous studies on the stability of the internal fixation for type A3 intertrochanteric fractures emphasized the important influence of the anatomical morphology of proximal femur such as the integrity of medial or lateral wall on the stability of the fracture after internal fixation. The concept of lateral wall was first proposed by Gotfried[ 18 ]. It was suggested that the integrity of lateral wall has significant meaning on the stability of the internal fixation of intertrochanteric fractures. Extramedullary fixations such as dynamic hip screw are particularly more dependent on the integrity of lateral wall. During the fixation of intertrochanteric fractures, the head screw or helical blade of both extramedullary and intramedullary fixations needs to be inserted through the lateral wall of femur. An intact lateral wall can provide lateral support for proximal fracture block, thus effectively preventing proximal fracture mass from sliding outward and turning inward and femoral shaft from moving inward, thereby reducing the occasion of screw cut-out [ 19 – 21 ]. Evans found that the stability of the posterior medial cortex of proximal femur is closely related to fracture stability [ 22 ]. He proposed that the medial wall, as an important conduit of compressive stress at proximal femur, directly affects the stability of intertrochanteric fractures via its integrity. Hence, intertrochanteric fractures should be treated with the objective of restoring and maintaining the anatomical alignment of posterior medial femoral cortex. However, there is a great controversy over whether to perform the reduction of medial wall after intertrochanteric fractures in elderly. In addition, AO/OTA classification in 2018 no longer used lesser trochanteric bone as an indicator but directly proceeded to the second step classification based on the condition of lateral wall, emphasizing the value of external wall to a greater extent[ 8 ]. As the structures that serve vital function in conducting load and bearing weigh, medial wall and posteromedial lesser trochanteric block have very important biomechanical significance in normal proximal femoral model. However, the current concept no longer emphasizes lesser trochanter fixation. Furthermore, the extreme difficulty of medial wall reduction will increase the operation time and surgical risk for elderly patient. In recent years, the theory of "lever - fulcrum - reconstruction" proposed by Dr. Zhang asserts that the trabecular structure within proximal femur is similar to that of lever system with the fulcrum located near the center of femoral head. Once intertrochanteric fractures occur, the trabecular structure is destroyed. In this case, the physiological lever of proximal femur is destroyed, and the fulcrum disappears, which results in the failure of weight bearing by femur. Therefore, the principle of intertrochanteric fractures treatment is to reconstruct the fulcrum of femur through the mechanical conduction system of internal fixation. The closer the reconstructed fulcrum is to the physiological fulcrum, the more stable the postoperative fixation is. Current treatments overemphasize the importance of internal and external walls, but postoperative stability is also determined by internal fixation system. The fulcrum reconstructed by the proximal femur bionic nail (PFBN) designed based on this theory is located at the junction of its tension nail and pressure nail, which is closer to the physiological fulcrum, endowing better stability to this type of internal fixation system. In this finite element analysis study, we found that the trends of maximum femur stress and displacement of the femoral models in the three fixation groups were similar. However, the maximum stress and displacement were the lowest in the PFBN group. Also, the maximum stress of the PFBN implant was lower than those in the PFNA group and InterTan group. These data indicate that the PFBN shows better mechanical property than the InterTan and PFNA do. One of the complications of femoral intertrochanteric fractures is screw cut-out of femoral head after internal fixation. Despite of the low incidence between 1% and 6.3%, it is the most common cause of the failures of extramedullary and intramedullary fixation, accounting for 85% of the total failure rate. In this study, the stress at the junction between the tip of neck nail and the cancellous bone of femoral head can intuitively reflect the magnitude of screw cutting force. The greater the stress value is, the more likely the screw cut-out will occur. In the PFBN group, the maximum stress at the junction between tension nail and cancellous bone was 19.344MPa, which was significantly lower than those in the PFNA and InterTan groups. Furthermore, the maximum displacement at femoral head in the PFBN group was 9.7068mm, which was also lower than those in the other two groups. Thus, the risk of screw cut-out was the lowest in the PFBN group. The same phenomenon suggests that the PFBN group was less prone to hip varus. The maximum stress values of the proximal fracture fragments in the three groups were all located at the junction between internal fixation and fracture plane, suggesting that almost all the stress applied by gravity toward proximal bone fragment transmits downward to internal fixation due to the interruption of bone continuity at fracture plane. Under 2100N, the maximum stresses of the internal implants in the three groups were located at the intersection of main nail and pressure nail/helical blade/twin nail. As the maximum stress was the smallest in the PFBN group, the corresponding possibilities of postoperative nail withdrawal and internal fixation breakage was the smallest. The advantages of PFBN discussed above are due to its unique bionic structure. While the original fulcrum formed by main nail and neck nail is preserved, the new fulcrum formed by the tension nail incorporate in PFBN and pressure nail mimics the fulcrum formed by pressure trabecula and tension trabecula near femoral head under physiological condition. Compared with the relatively long lever arms on gravitation side of PFNA and InterTan, the inner lever arm of PFBN is shorter, and the outer lever arm at trochanter is longer. Hence, the stress at the new fulcrum of PFBN was significantly smaller than those at the original fulcrums of PFNA/InterTan. The same reason can explain that the stress at the junction between pressure nail and exterior cortex in PFBN was smaller than that in PFNA. In addition, the fulcrum is also formed by main nail and tension nail. All these new fulcrums help to share the stress that was originally exerted on the original fulcrum, which reduce the occurrence of strew withdraw and breakage caused by local stress concentration. Compared with PFNA and InterTan, PFBN has larger surface contact with the cancellous bone within femoral head. Thus, the relatively smaller stress at the junction between the tip of neck nail and the cancellous bone of femoral head can be explained. Conclusion Compared with PFNA and InterTan, PFBN has better mechanical properties and has advantages over traditional internal fixation systems in the treatment of unstable intertrochanteric fractures. Abbreviations PFBN Proximal Femur Bionic Nail PFNA Froximal Femoral Anti-rotation FEA Finite Element Analysis OTA the Orthopaedic Trauma Association CT Computed Tomography Declarations Ethics approval and consent to participate The study was approved by the institutional ethical review board of the Peking University People’s Hospital and was done in accordance with the Declaration of Helsinki. Consent to participate was obtained from the any participants included in the study, and informed written consent was obtained from all subjects and/or their legal guardian(s). Consent to publish Not applicable. Availability of data and materials The datasets supporting the conclusions of this article are included within the article and its additional files. If anyone wants to request data of this study, please contact Zhang Dianying of corresponding authors. Competing interests All authors declare no conflict of interest. Funding This work was financially supported by Innovative Research Team of Ministry of Education of China (IRT_16R01); College Construction Project of Peking University Health Science Center (2020) - National Trauma Medical Center (BMU2020XY005-01); College Construction Project of Peking University Health Science Center (2020) - Key Laboratory of Trauma Treatment and Nerve Regeneration of Ministry of Education (BMU2020XY005-03); College Construction Project of Peking University Health Science Center (2021) - National Trauma Medical Center (BMU2021XY005-01); College Construction Project of Peking University Health Science Center (2021) - Key Laboratory of Trauma Treatment and Nerve Regeneration of Ministry of Education (BMU2021XY005-03); Construction Project of Peking University People's Hospital (2021) - National Trauma Medical Center (BMU2021XY008-01); Construction project of Peking University People's Hospital - Key Laboratory of Trauma Treatment and Nerve Regeneration of Ministry of Education (BMU2021XY008-03). Acknowledgement, Thanks to De.Testing Lab for the guidance of this study. Authors Contribution Chen Xiong, Lijia Zhang and Yanhua Wang wrote the main manuscript text , and Xiaomeng, Kai Yu, and Jiabao Ju prepared figures and tables. Dianying Zhang and Yingze Zhang Provides the idea. All authors have reviewed and approved the final manuscript. Chen Xiong, Lijia Zhang and Yanhua Wang contribute equally to this work. References Ren Y, Hu J, Lu B, Zhou W, Tan B: Prevalence and risk factors of hip fracture in a middle-aged and older Chinese population . Bone 2019, 122 :143-149. Mattisson L, Bojan A, Enocson A: Epidemiology, treatment and mortality of trochanteric and subtrochanteric hip fractures: data from the Swedish fracture register . BMC Musculoskelet Disord 2018, 19 (1):369. İmerci A, Aydogan NH, Tosun K: A comparison of the InterTan nail and proximal femoral fail antirotation in the treatment of reverse intertrochanteric femoral fractures . Acta Orthop Belg 2018, 84 (2):123-131. 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Hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Xiaofeng","middleName":"","lastName":"Chen","suffix":""},{"id":121177513,"identity":"281fa581-87ae-4357-9824-0efa038aae81","order_by":8,"name":"Yun Ji","email":"","orcid":"","institution":"Peking University People's Hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Yun","middleName":"","lastName":"Ji","suffix":""},{"id":121177514,"identity":"b810e741-6be0-46b9-8738-9c0f8db072b5","order_by":9,"name":"Yingze Zhang","email":"","orcid":"","institution":"Third Hospital of Hebei Medical University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Yingze","middleName":"","lastName":"Zhang","suffix":""},{"id":121177515,"identity":"c4eb5b69-0899-4143-bed2-4f2063d00d20","order_by":10,"name":"Dianying Zhang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAw0lEQVRIiWNgGAWjYFCCBMYHCQY2cmzs7QeI1sJs8KEgzZiP50wC0VrYJGd8OJQ4T8LBgDgN8u05xsY8BgfS2yQYEhh+VGwjrIWx543hYx6DO7lt0o0HGHvO3CashVkCbMuz3DaZAwnMjG1EaGGTyDGT5jE4nM4mkWBAnBYeoBbJGQaHE4jXIsHzrNjgg0GaYRswkA8S5Rf59uSNDxL+2MjLt7cffPCjgggtDAwciOg4QIx6IGB/QKTCUTAKRsEoGLEAAPGUO/wg+Zy6AAAAAElFTkSuQmCC","orcid":"","institution":"Peking University People's Hospital","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Dianying","middleName":"","lastName":"Zhang","suffix":""}],"badges":[],"createdAt":"2022-07-08 02:59:14","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-1837198/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-1837198/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":24205295,"identity":"946e2a23-f950-47dd-923f-4fe6d6e1de8e","added_by":"auto","created_at":"2022-07-22 16:42:41","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":52324,"visible":true,"origin":"","legend":"\u003cp\u003e\tModel of femoral fracture\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-1837198/v1/6f517f304ebd21774f9acba6.png"},{"id":24205296,"identity":"717d76d1-ce6e-4dbd-a574-3a219fd9f8c3","added_by":"auto","created_at":"2022-07-22 16:42:41","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":247571,"visible":true,"origin":"","legend":"\u003cp\u003eModel of an intertrochanteric fracture of a normal femur with internal fixation\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-1837198/v1/cd2e0f114c23390ecc766d74.png"},{"id":24204570,"identity":"5de929b9-d5e3-400a-b2c8-86314eecf516","added_by":"auto","created_at":"2022-07-22 16:37:41","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":153390,"visible":true,"origin":"","legend":"\u003cp\u003eMeshing of the model\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-1837198/v1/2a730685c63794a300ced233.png"},{"id":24205652,"identity":"334af263-26b7-45a7-8832-2875445dee1d","added_by":"auto","created_at":"2022-07-22 16:47:41","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":56235,"visible":true,"origin":"","legend":"\u003cp\u003ePoint of application of the femoral load\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-1837198/v1/251533d9990625a32175b1e9.png"},{"id":24206333,"identity":"f54ac0b8-a739-4ad6-89bb-33ff944b3af5","added_by":"auto","created_at":"2022-07-22 16:52:41","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":159050,"visible":true,"origin":"","legend":"\u003cp\u003eFemoral displacement distribution in normal femur and in fracture models with three internal fixation\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-1837198/v1/0ef79561eeec105d4ccda37d.png"},{"id":24204573,"identity":"612899ab-1e3a-4526-bdf9-61f6d8a2b204","added_by":"auto","created_at":"2022-07-22 16:37:41","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":294505,"visible":true,"origin":"","legend":"\u003cp\u003eStress distribution of the femur in normal femur and in three fracture models with internal fixation\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-1837198/v1/5d862de86b026650d76c1578.png"},{"id":24204584,"identity":"3d422bfd-ad5a-44be-95df-0d3c81d6378e","added_by":"auto","created_at":"2022-07-22 16:37:41","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":341333,"visible":true,"origin":"","legend":"\u003cp\u003eProximal femoral head stress distribution in models with three different internal fixations\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-1837198/v1/dac23c3f5451278959ad32f4.png"},{"id":24205293,"identity":"748e3c78-da0a-4121-838e-9a16d0be3d10","added_by":"auto","created_at":"2022-07-22 16:42:41","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":191407,"visible":true,"origin":"","legend":"\u003cp\u003eStress distribution of proximal femoral fracture fragment in three groups of fracture models with internal fixation\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-1837198/v1/7b23d8020ee7034297033826.png"},{"id":24206630,"identity":"d1da4051-5eaf-4907-8148-1eebf1984b66","added_by":"auto","created_at":"2022-07-22 16:57:41","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":201513,"visible":true,"origin":"","legend":"\u003cp\u003ePFNA stress distribution under increasing load\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-1837198/v1/0ce51eeb3ab83cc519605558.png"},{"id":24205656,"identity":"f5fd2d06-5249-45fe-8e90-10f9e468ba1c","added_by":"auto","created_at":"2022-07-22 16:47:41","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":44610,"visible":true,"origin":"","legend":"\u003cp\u003eStress extraction site markers for PFNA\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-1837198/v1/471d54043cc2894a9762764c.png"},{"id":24205302,"identity":"307c167e-254a-40d2-a3cd-d49fb0d3fa77","added_by":"auto","created_at":"2022-07-22 16:42:41","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":218954,"visible":true,"origin":"","legend":"\u003cp\u003eInterTan stress distribution under increasing load\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-1837198/v1/8a29831a4af8ea0adccdbf69.png"},{"id":24205654,"identity":"15429c9f-2350-4430-a159-1ee3c1cbb756","added_by":"auto","created_at":"2022-07-22 16:47:41","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":62071,"visible":true,"origin":"","legend":"\u003cp\u003eStress extraction site markers at InterTan\u003c/p\u003e","description":"","filename":"12.png","url":"https://assets-eu.researchsquare.com/files/rs-1837198/v1/5ebe67904de4b69806152c95.png"},{"id":24205299,"identity":"fdc3a442-ead3-44ca-8357-bf4dd27b5f1b","added_by":"auto","created_at":"2022-07-22 16:42:41","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":223145,"visible":true,"origin":"","legend":"\u003cp\u003ePFBN stress distribution under increasing load\u003c/p\u003e","description":"","filename":"13.png","url":"https://assets-eu.researchsquare.com/files/rs-1837198/v1/0231e8e1f3277bef7f59a74a.png"},{"id":24204579,"identity":"0b002339-436b-440b-b7d0-289c96d6a47a","added_by":"auto","created_at":"2022-07-22 16:37:41","extension":"png","order_by":14,"title":"Figure 14","display":"","copyAsset":false,"role":"figure","size":52741,"visible":true,"origin":"","legend":"\u003cp\u003eStress extraction site markers for PFBN\u003c/p\u003e","description":"","filename":"14.png","url":"https://assets-eu.researchsquare.com/files/rs-1837198/v1/ddc4bb6ee264337b3b1d1e7b.png"},{"id":29831160,"identity":"4b0dcb2b-c237-4741-963d-f73c49684a83","added_by":"auto","created_at":"2022-12-02 17:32:04","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3523123,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-1837198/v1/2b91efa2-4e72-49de-a386-c337ea80b863.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Finite Element Analysis of Proximal Femur Bionic Nail (PFBN), Froximal Femoral Anti-rotation Intramedullary Nail and InterTan for Treatment of Reverse Obliquity Intertrochanteric Fractures","fulltext":[{"header":"Background","content":"\u003cp\u003eFemoral Intertrochanteric fracture is one of the common causes of death and disability in the elderly. Falls and indoor activity injuries are the most common causes of injury. Given the name of \u0026quot;the last fracture in the life of the elderly\u0026quot;, this type of fracture affects approximately 750,000 people worldwide each year with an annual mortality rate up to 37%[1-5].The surgical treatment of intertrochanteric fractures has evolved from the previous extramedullary fixation to the current intramedullary fixation. Although the treatment has been constantly improving[6], complications have always existed, which makes them hard to be ignored. Among the subtypes of intertrochanteric fractures, A3 type fractures accounts for 10% to 34% of all intertrochanteric fractures[2, 7, 8], which is characterized by the simultaneous involvement of medial wall and lateral wall. It is classified as unstable intertrochanteric fractures due to the characteristics including difficult reduction, hard reduction maintenance, etc. Although the American Association of Orthopedic Surgery (AAOS) recommends intramedullary nailing for the treatment of type A3 intertrochanteric fractures, the failure rate after internal fixation is up to 30%[9-11], and the incidence of complications was significantly higher than those of A1 and A2 fractures. Previous studies emphasize the importance of the integrity of lateral or medial wall on postoperative stability. Due to the unique fracture morphology of this fracture subtype, it cannot acquire complete medial or lateral wall support after fixation. Thus, stable internal fixation is not obtained, and postoperative internal fixation failure happens. The theory of \u0026quot;lever - balance - reconstruction\u0026quot; put forward by Prof. Zhang gives new enlightenment to the reduction and fixation of intertrochanteric fractures. According to the theory, the pressure trabecula and tension trabecula within proximal femur under physiological condition form a structure similar to that of lever. Its fulcrum is located near the center of femoral head. The pressure arm of medial femur is short, and the lateral arm is long. Thus, the proximal femur can bear large compressive stress. After fractures, the original lever system is destroyed, and the internal fixation system establishes a new lever system to replace the original lever system until fracture healing. Postoperative stability depends on the stability of the internal fixation and has nothing to do with the structure of internal or external wall[12, 13].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe proximal femur bionic nail (PFBN) derived from this theory includes a main nail, a pressure nail and a tension nail[14]. Through the combination of the tension nail and the pressure nail, the reconstructed fulcrum of the fixation system is very close to the anatomical fulcrum, which makes the fixed proximal femur effective in counteracting the compressive stress generated during postoperative weight-bearing and thus offer better stability to the fixation system. Theoretically, it is suitable for all types of intertrochanteric fractures. Preliminary finite element analysis and biomechanical tests have confirmed that PFBN has a greater advantage in the treatment of traditionally stable intertrochanteric fractures than proximal femoral rotation intramedullary nail (PFNA) and InterTan. It is more effective in the prevention of complications, such as internal fixation of fracture, hip varus and shortening of the femoral head shift, screw cutout. In this study, the biomechanical characteristics of PFBN, PFNA and InterTan in the treatment of AO-OTA 31-A3.1 type intertrochanteric fracture were analyzed by finite element analysis to further study the mechanical properties of PFBN and to provide a new idea for the treatment and study of elder intertrochanteric fracture.\u003c/p\u003e"},{"header":"Methods","content":"\u003ch2\u003e1. Establishment of fracture model\u003c/h2\u003e\n\u003cp\u003eThe femoral CT images of an elderly woman (65 years old, 168cm, 53Kg, no femoral disease) were selected, which were imported into Mimics 21.0 (Materialise, Leuven, Belgium) software. The femur 3D model was established through threshold segmentation, region growth, space filling and other steps to complete the smooth treatment of the surface. According to the fracture characteristics of AO/OTA 31-A3.1, the model was segmented to establish the fracture model(Figure 1).\u003c/p\u003e\n\u003ch2\u003e2. Establishment of intramedullary nailing model\u003c/h2\u003e\n\u003cp\u003eAccording to the dimensions of the intramedullary nails provided by the manufacturers, the 3D geometric models of intramedullary nail were established via Unigraphics NX 12.0 (Siemens PLM Software). The assemblies of the intramedullary nail models were completed before export of the geometric files(Figure 2).\u003c/p\u003e\n\u003ch2\u003e3. Model assembly\u003c/h2\u003e\n\u003cp\u003eThe three-dimensional femoral model and the intramedullary nail models were imported into 3-matic. According to the manufacturer\u0026apos;s instructions, the position of intramedullary nail system was adjusted via rotation and translation function to make it consistent with the surgical fixation position. A circular region of 30mm diameter above femoral head was divided as the loading surface. The fixation surface is defined as the 40mm high area at the base of femoral condyle.\u0026nbsp;\u003c/p\u003e\n\u003ch2\u003e4. Meshing\u003c/h2\u003e\n\u003cp\u003eThe mesh size of the model was set as 1.5mm in 3-matic. The mesh quality was checked and optimized, and the second-order decahedral mesh (Solid187) was generated based on surface mesh(Model was meshed like Figure 3, and number of nodes and units of each model was shown in Table 1).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1: Number of nodes and units divided by Meshing\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellpadding=\"0\" cellspacing=\"0\" width=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e\u003cstrong\u003eMesh\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e\u003cstrong\u003eNormal\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e\u003cstrong\u003ePFNA\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e\u003cstrong\u003eInterTan\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e\u003cstrong\u003ePFBN\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003eNumber of nodes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e20636\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e325170\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e347236\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e324130\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003eNumber of units\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e152280\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e217101\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e228819\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20%\"\u003e\n \u003cp\u003e214458\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003ch2\u003e5. Material properties\u003c/h2\u003e\n\u003cp\u003eThe volume mesh file was imported into Mimics, and values were assigned to the model based on the gray values. According to the method recommended in previous literature, the Young\u0026apos;s moduli of cortical bone and cancellous bone were set as 17Gpa and 445MPa, and the Poisson\u0026apos;s ratios were set as 0.3 and 0.2; the Young\u0026apos;s modulus of implant was set as 113800MPa, and the Poisson\u0026apos;s ratio was set as 0.342[15, 16].(Table 2)\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;Table 2: Material properties of bone and internal fixation\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellpadding=\"0\" cellspacing=\"0\" width=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"20.60931899641577%\"\u003e\n \u003cp\u003ePart\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"33.691756272401435%\"\u003e\n \u003cp\u003eComponent\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"22.043010752688172%\"\u003e\n \u003cp\u003eYoung \u0026apos;s modulus (MPa)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"23.655913978494624%\"\u003e\n \u003cp\u003ePoisson \u0026apos;s ratio\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" valign=\"top\" width=\"20.60931899641577%\"\u003e\n \u003cp\u003eBone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"33.691756272401435%\"\u003e\n \u003cp\u003eCortical bone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"22.043010752688172%\"\u003e\n \u003cp\u003e17000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"23.655913978494624%\"\u003e\n \u003cp\u003e0.3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"42.43792325056433%\"\u003e\n \u003cp\u003eCancellous bone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"27.76523702031603%\"\u003e\n \u003cp\u003e445\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"29.79683972911964%\"\u003e\n \u003cp\u003e0.2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"20.60931899641577%\"\u003e\n \u003cp\u003eImplant\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"33.691756272401435%\"\u003e\n \u003cp\u003eNail \u0026amp; Screw(TI6Al4V)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"22.043010752688172%\"\u003e\n \u003cp\u003e113800\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"23.655913978494624%\"\u003e\n \u003cp\u003e0.342\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003ch2\u003e6. Calculation\u003c/h2\u003e\n\u003cp\u003eImport the ANSYS processing file into ANSYS Workbench 2020R2 and set the contact conditions (friction contact, bone-to-bone friction coefficient 0.46, bone-to-nail friction coefficient 0.42, nail to nail internal friction coefficient 0.2)[15]. Referring to similar studies[17], in order to simulated the different stages of gradual loading under the fracture, loading condition was set as 2100N, divided into seven steps, and the direction was downward of normal standing Angle. A diameter range of 30mm above the femoral head was set as the loading surface(Figure 4), and the restriction surface at the femoral condyle was set for full fixation.\u0026nbsp;\u003c/p\u003e\n\u003ch2\u003e7. Observation index\u003c/h2\u003e\n\u003cp\u003eThe VonMises stress and displacement of the whole femur were extracted. The Von Mises stress distribution of the intramedullary nailing system was obtained under 7 equal-spacing loading conditions from 300N to 2100N.\u003c/p\u003e"},{"header":"Results","content":"\u003ch2\u003e1. Femoral displacement distribution\u003c/h2\u003e\n\u003cp\u003eThe figure(Figure 5) shows the femoral displacement distributions of regular femur model and A3.1 intertrochanteric fracture model integrated with three different internal fixations under a load of 2100N. It can be seen that the maximum displacement of regular femur was concentrated at the region near the loading point of femoral head followed by intertrochanter, subtrochanter, femoral shaft and distal femur as the regions with subsequential large displacement, respectively. In addition, there was another area with relatively large displacement at greater trochanter. The displacement trends of the fractured femur model with three different internal fixations were similar to that of regular femur model. Among these models, the PFBN group had the smallest maximum displacement of 9.7068mm; the InterTan group had the maximum displacement of 10.678mm; the PFNA group had the largest maximum displacement of 14.274mm.\u003c/p\u003e\n\u003ch2\u003e2. Stress distribution of femur\u003c/h2\u003e\n\u003cp\u003eThis figure(Figure 6) shows the femoral stress distributions of regular femur model and the fracture model assembled with three different internal fixations under a load of 2100 N. It was found that the maximum stress of regular femur was located at subtrochanteric inner cortex. The maximum stress of the PFNA group was distributed at the intersection of the helical blade and outer cortex bone with a value of 403.71MPa. The maximum stress of the InterTan group was 362.72 MPa, which was distributed at the intersection of the compression screw and the main nail. The maximum stress of the PFBN group was the lowest among those of the three groups, which was distributed at the intersection of the pressure nail and lateral cortex with a value of 186.23MPa.\u0026nbsp;\u003c/p\u003e\n\u003ch2\u003e3. Stress distribution of proximal femoral head\u003c/h2\u003e\n\u003cp\u003eIn all the three groups in Figure 7, there was relative stress concentration at the interface between cancellous bone and head screw. The local maximum stress of the PFBN group was the smallest (19.344MPa), which occurred at the tip of the pressure nail. The maximum stresses of the PFNA and InterTan groups were 32.761MPa and 28.111 MPa, and the locations were the tips of the helical blade and one of the twin screws, respectively.\u0026nbsp;\u003c/p\u003e\n\u003ch2\u003e4. Stress distribution of proximal fracture fragment\u003c/h2\u003e\n\u003cp\u003eThe figure(Figure 8) shows the stress distributions of the proximal fracture blocks under a load of 2100N. It can be seen that the maximum stresses were all distributed at the junction of internal fixator and fracture surface. In the PFNA group, the maximum stress was 102.3MPa at the position of the helical blade near and the main nail. The maximum stress of the InterTan group was 64.797MPa at the junction of the compression screw and the main nail. The maximum stress of the PFBN group was 46.644 MPa with the location the same as that of the InterTan group.\u0026nbsp;\u003c/p\u003e\n\u003ch2\u003e5. Stress distribution of inner plants\u0026nbsp;\u003c/h2\u003e\n\u003ch2\u003e5.1 PFNA internal fixation stress distribution\u003c/h2\u003e\n\u003cp\u003e\u003cstrong\u003eTable 3: Stress values at each point of PFNA internal fixation\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellpadding=\"0\" cellspacing=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"15.625%\"\u003e\n \u003cp\u003e\u003cstrong\u003eUnit: MPa\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.458333333333334%\"\u003e\n \u003cp\u003e\u003cstrong\u003e300N\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.458333333333334%\"\u003e\n \u003cp\u003e\u003cstrong\u003e600N\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.458333333333334%\"\u003e\n \u003cp\u003e\u003cstrong\u003e900N\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.458333333333334%\"\u003e\n \u003cp\u003e\u003cstrong\u003e1200N\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.458333333333334%\"\u003e\n \u003cp\u003e\u003cstrong\u003e1500N\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.541666666666666%\"\u003e\n \u003cp\u003e\u003cstrong\u003e1800N\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.541666666666666%\"\u003e\n \u003cp\u003e\u003cstrong\u003e2100N\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"15.625%\"\u003e\n \u003cp\u003ePosition 1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.458333333333334%\"\u003e\n \u003cp\u003e27.313\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.458333333333334%\"\u003e\n \u003cp\u003e54..94\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.458333333333334%\"\u003e\n \u003cp\u003e82.138\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.458333333333334%\"\u003e\n \u003cp\u003e109.15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.458333333333334%\"\u003e\n \u003cp\u003e135.64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.541666666666666%\"\u003e\n \u003cp\u003e161.92\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.541666666666666%\"\u003e\n \u003cp\u003e188.300\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"15.625%\"\u003e\n \u003cp\u003ePosition 2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.458333333333334%\"\u003e\n \u003cp\u003e188.860\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.458333333333334%\"\u003e\n \u003cp\u003e377.410\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.458333333333334%\"\u003e\n \u003cp\u003e570.820\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.458333333333334%\"\u003e\n \u003cp\u003e775.190\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.458333333333334%\"\u003e\n \u003cp\u003e986.550\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.541666666666666%\"\u003e\n \u003cp\u003e1208.300\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.541666666666666%\"\u003e\n \u003cp\u003e1445.000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"15.625%\"\u003e\n \u003cp\u003ePosition 3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.458333333333334%\"\u003e\n \u003cp\u003e289.42\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.458333333333334%\"\u003e\n \u003cp\u003e550.42\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.458333333333334%\"\u003e\n \u003cp\u003e713.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.458333333333334%\"\u003e\n \u003cp\u003e807.13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.458333333333334%\"\u003e\n \u003cp\u003e840.73\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.541666666666666%\"\u003e\n \u003cp\u003e878.82\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"13.541666666666666%\"\u003e\n \u003cp\u003e965.58\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003e5.2 Internal Fixed Stress Distribution of InterTan\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 4: Stress values at each point of InterTan internal fixation\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellpadding=\"0\" cellspacing=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"15.151515151515152%\"\u003e\n \u003cp\u003e\u003cstrong\u003eUnit: MPa\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.121212121212121%\"\u003e\n \u003cp\u003e\u003cstrong\u003e300N\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.121212121212121%\"\u003e\n \u003cp\u003e\u003cstrong\u003e600N\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.121212121212121%\"\u003e\n \u003cp\u003e\u003cstrong\u003e900N\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.121212121212121%\"\u003e\n \u003cp\u003e\u003cstrong\u003e1200N\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.121212121212121%\"\u003e\n \u003cp\u003e\u003cstrong\u003e1500N\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.121212121212121%\"\u003e\n \u003cp\u003e\u003cstrong\u003e1800N\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.121212121212121%\"\u003e\n \u003cp\u003e\u003cstrong\u003e2100N\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"15.151515151515152%\"\u003e\n \u003cp\u003ePosition 1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.121212121212121%\"\u003e\n \u003cp\u003e12.508\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.121212121212121%\"\u003e\n \u003cp\u003e24.526\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.121212121212121%\"\u003e\n \u003cp\u003e36.144\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.121212121212121%\"\u003e\n \u003cp\u003e47.636\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.121212121212121%\"\u003e\n \u003cp\u003e59.059\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.121212121212121%\"\u003e\n \u003cp\u003e70.278\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.121212121212121%\"\u003e\n \u003cp\u003e81.335\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"15.151515151515152%\"\u003e\n \u003cp\u003ePosition 2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.121212121212121%\"\u003e\n \u003cp\u003e148.310\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.121212121212121%\"\u003e\n \u003cp\u003e290.450\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.121212121212121%\"\u003e\n \u003cp\u003e432.270\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.121212121212121%\"\u003e\n \u003cp\u003e574.230\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.121212121212121%\"\u003e\n \u003cp\u003e711.210\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.121212121212121%\"\u003e\n \u003cp\u003e823.920\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.121212121212121%\"\u003e\n \u003cp\u003e919.620\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"15.151515151515152%\"\u003e\n \u003cp\u003ePosition 3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.121212121212121%\"\u003e\n \u003cp\u003e43.953\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.121212121212121%\"\u003e\n \u003cp\u003e84.271\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.121212121212121%\"\u003e\n \u003cp\u003e123.280\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.121212121212121%\"\u003e\n \u003cp\u003e162.990\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.121212121212121%\"\u003e\n \u003cp\u003e203.510\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.121212121212121%\"\u003e\n \u003cp\u003e245.000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.121212121212121%\"\u003e\n \u003cp\u003e354.330\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003e5.3 PFBN internal fixed stress distribution\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 5: Stress values at each point of PFBN internal fixation\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellpadding=\"0\" cellspacing=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"17.894736842105264%\"\u003e\n \u003cp\u003e\u003cstrong\u003eUnit: MPa\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"12.631578947368421%\"\u003e\n \u003cp\u003e\u003cstrong\u003e300N\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e\u003cstrong\u003e600N\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e\u003cstrong\u003e900N\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e\u003cstrong\u003e1200N\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e\u003cstrong\u003e1500N\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e\u003cstrong\u003e1800N\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e\u003cstrong\u003e2100N\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"17.894736842105264%\"\u003e\n \u003cp\u003ePosition 1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"12.631578947368421%\"\u003e\n \u003cp\u003e29.023\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e57.941\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e87.439\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e117.82\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e149.94\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e185.16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e222.41\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"17.894736842105264%\"\u003e\n \u003cp\u003ePosition 2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"12.631578947368421%\"\u003e\n \u003cp\u003e131.86\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e256.38\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e382.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e510.76\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e640\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e773.71\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e911.77\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"17.894736842105264%\"\u003e\n \u003cp\u003ePosition 3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"12.631578947368421%\"\u003e\n \u003cp\u003e47.837\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e93.648\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e138.38\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e178.93\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e217.89\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e252.66\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e285.79\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"17.894736842105264%\"\u003e\n \u003cp\u003ePosition 4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"12.631578947368421%\"\u003e\n \u003cp\u003e40.453\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e82.013\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e123\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e163.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e201.07\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e237.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e270.26\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"17.894736842105264%\"\u003e\n \u003cp\u003ePosition 5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"12.631578947368421%\"\u003e\n \u003cp\u003e22.201\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e44.671\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e66.132\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e86.626\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e106.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e125.07\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e143.26\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" width=\"17.894736842105264%\"\u003e\n \u003cp\u003ePosition 6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"12.631578947368421%\"\u003e\n \u003cp\u003e0.66951\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e1.3359\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e1.9981\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e2.6542\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e3.306\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e3.9605\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" width=\"11.578947368421053%\"\u003e\n \u003cp\u003e4.6268\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eAs shown in the figures above(Figure 9-14, Table 3-5), the maximum stresses of the three groups were located at the intersections of the main nail and the pressure/helical blade/twin screw. We found that the maximum stresses of the three groups of internal fixation model were increased linearly with the increase of the applied stress. \u0026nbsp;Under the condition of 2100N, the maximum stress of the PFNA group was 1445 MPa; the maximum stress of the InterTan group was 919.62 MPa; the maximum stress of the PFBN group was 911.77 MPa, which was the lowest among those of the three groups.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eAO/OTA 31-type A3 femoral intertrochanteric fractures has its unique characteristics. Different from A1 and A2 types of fracture, the direction of its intertrochanteric fracture line extends from the superior medial side of proximal lesser trochanter to the inferior lateral side of greater trochanter, and both the inner and outer side walls are involved. Furthermore, the fracture line often spread to upper femur. All of these traits make it as unstable fractures. Compared with type A1 and A2 intertrochanteric fractures, type A3 fractures has higher occurrence of complications including screw cutout, hip varus deformity, nail withdraw, internal fixation failure, etc. These ultimately lead to fracture nonunion or malunion. High-energy damage often causes comminuted fracture, making the reduction and biomechanical stability as the key to the treatment of type A3 intertrochanteric fracture. In this study, the biomechanical properties of PFBN, PFNA and InterTan in the treatment of AO/OTA 31-A3 intertrochanteric fractures in elderly were compared using the model of A3.1 fracture for fracture model construction.\u003c/p\u003e \u003cp\u003ePrevious studies on the stability of the internal fixation for type A3 intertrochanteric fractures emphasized the important influence of the anatomical morphology of proximal femur such as the integrity of medial or lateral wall on the stability of the fracture after internal fixation. The concept of lateral wall was first proposed by Gotfried[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. It was suggested that the integrity of lateral wall has significant meaning on the stability of the internal fixation of intertrochanteric fractures. Extramedullary fixations such as dynamic hip screw are particularly more dependent on the integrity of lateral wall. During the fixation of intertrochanteric fractures, the head screw or helical blade of both extramedullary and intramedullary fixations needs to be inserted through the lateral wall of femur. An intact lateral wall can provide lateral support for proximal fracture block, thus effectively preventing proximal fracture mass from sliding outward and turning inward and femoral shaft from moving inward, thereby reducing the occasion of screw cut-out [\u003cspan additionalcitationids=\"CR20\" citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Evans found that the stability of the posterior medial cortex of proximal femur is closely related to fracture stability [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. He proposed that the medial wall, as an important conduit of compressive stress at proximal femur, directly affects the stability of intertrochanteric fractures via its integrity. Hence, intertrochanteric fractures should be treated with the objective of restoring and maintaining the anatomical alignment of posterior medial femoral cortex. However, there is a great controversy over whether to perform the reduction of medial wall after intertrochanteric fractures in elderly. In addition, AO/OTA classification in 2018 no longer used lesser trochanteric bone as an indicator but directly proceeded to the second step classification based on the condition of lateral wall, emphasizing the value of external wall to a greater extent[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. As the structures that serve vital function in conducting load and bearing weigh, medial wall and posteromedial lesser trochanteric block have very important biomechanical significance in normal proximal femoral model. However, the current concept no longer emphasizes lesser trochanter fixation. Furthermore, the extreme difficulty of medial wall reduction will increase the operation time and surgical risk for elderly patient. In recent years, the theory of \"lever - fulcrum - reconstruction\" proposed by Dr. Zhang asserts that the trabecular structure within proximal femur is similar to that of lever system with the fulcrum located near the center of femoral head. Once intertrochanteric fractures occur, the trabecular structure is destroyed. In this case, the physiological lever of proximal femur is destroyed, and the fulcrum disappears, which results in the failure of weight bearing by femur. Therefore, the principle of intertrochanteric fractures treatment is to reconstruct the fulcrum of femur through the mechanical conduction system of internal fixation. The closer the reconstructed fulcrum is to the physiological fulcrum, the more stable the postoperative fixation is. Current treatments overemphasize the importance of internal and external walls, but postoperative stability is also determined by internal fixation system. The fulcrum reconstructed by the proximal femur bionic nail (PFBN) designed based on this theory is located at the junction of its tension nail and pressure nail, which is closer to the physiological fulcrum, endowing better stability to this type of internal fixation system.\u003c/p\u003e \u003cp\u003eIn this finite element analysis study, we found that the trends of maximum femur stress and displacement of the femoral models in the three fixation groups were similar. However, the maximum stress and displacement were the lowest in the PFBN group. Also, the maximum stress of the PFBN implant was lower than those in the PFNA group and InterTan group. These data indicate that the PFBN shows better mechanical property than the InterTan and PFNA do. One of the complications of femoral intertrochanteric fractures is screw cut-out of femoral head after internal fixation. Despite of the low incidence between 1% and 6.3%, it is the most common cause of the failures of extramedullary and intramedullary fixation, accounting for 85% of the total failure rate. In this study, the stress at the junction between the tip of neck nail and the cancellous bone of femoral head can intuitively reflect the magnitude of screw cutting force. The greater the stress value is, the more likely the screw cut-out will occur. In the PFBN group, the maximum stress at the junction between tension nail and cancellous bone was 19.344MPa, which was significantly lower than those in the PFNA and InterTan groups. Furthermore, the maximum displacement at femoral head in the PFBN group was 9.7068mm, which was also lower than those in the other two groups. Thus, the risk of screw cut-out was the lowest in the PFBN group. The same phenomenon suggests that the PFBN group was less prone to hip varus. The maximum stress values of the proximal fracture fragments in the three groups were all located at the junction between internal fixation and fracture plane, suggesting that almost all the stress applied by gravity toward proximal bone fragment transmits downward to internal fixation due to the interruption of bone continuity at fracture plane. Under 2100N, the maximum stresses of the internal implants in the three groups were located at the intersection of main nail and pressure nail/helical blade/twin nail. As the maximum stress was the smallest in the PFBN group, the corresponding possibilities of postoperative nail withdrawal and internal fixation breakage was the smallest.\u003c/p\u003e \u003cp\u003eThe advantages of PFBN discussed above are due to its unique bionic structure. While the original fulcrum formed by main nail and neck nail is preserved, the new fulcrum formed by the tension nail incorporate in PFBN and pressure nail mimics the fulcrum formed by pressure trabecula and tension trabecula near femoral head under physiological condition. Compared with the relatively long lever arms on gravitation side of PFNA and InterTan, the inner lever arm of PFBN is shorter, and the outer lever arm at trochanter is longer. Hence, the stress at the new fulcrum of PFBN was significantly smaller than those at the original fulcrums of PFNA/InterTan. The same reason can explain that the stress at the junction between pressure nail and exterior cortex in PFBN was smaller than that in PFNA. In addition, the fulcrum is also formed by main nail and tension nail. All these new fulcrums help to share the stress that was originally exerted on the original fulcrum, which reduce the occurrence of strew withdraw and breakage caused by local stress concentration. Compared with PFNA and InterTan, PFBN has larger surface contact with the cancellous bone within femoral head. Thus, the relatively smaller stress at the junction between the tip of neck nail and the cancellous bone of femoral head can be explained.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eCompared with PFNA and InterTan, PFBN has better mechanical properties and has advantages over traditional internal fixation systems in the treatment of unstable intertrochanteric fractures.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003ePFBN \u0026nbsp;Proximal Femur Bionic Nail\u003c/p\u003e\n\u003cp\u003ePFNA \u0026nbsp;Froximal Femoral Anti-rotation\u003c/p\u003e\n\u003cp\u003eFEA \u0026nbsp;Finite Element Analysis\u003c/p\u003e\n\u003cp\u003eOTA \u0026nbsp;the Orthopaedic Trauma Association\u003c/p\u003e\n\u003cp\u003eCT \u0026nbsp;Computed Tomography\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study was approved by the institutional ethical review board of the Peking University People\u0026rsquo;s Hospital and was done in accordance with the Declaration of Helsinki. Consent to participate\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003ewas obtained from the any participants included in the study, and informed written consent was obtained from all subjects and/or their legal guardian(s).\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to publish\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets supporting the conclusions of this article are included within the article and its additional files. If anyone wants to request data of this study, please contact Zhang Dianying of corresponding authors.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors declare no conflict of interest. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was financially supported by Innovative Research Team of Ministry of Education of China (IRT_16R01); College Construction Project of Peking University Health Science Center (2020) - National Trauma Medical Center (BMU2020XY005-01); College Construction Project of Peking University Health Science Center (2020) - Key Laboratory of Trauma Treatment and Nerve Regeneration of Ministry of Education (BMU2020XY005-03); College Construction Project of Peking University Health Science Center (2021) - National Trauma Medical Center (BMU2021XY005-01); College Construction Project of Peking University Health Science Center (2021) - Key Laboratory of Trauma Treatment and Nerve Regeneration of Ministry of Education (BMU2021XY005-03); Construction Project of Peking University People\u0026apos;s Hospital (2021) - National Trauma Medical Center (BMU2021XY008-01); Construction project of Peking University People\u0026apos;s Hospital - Key Laboratory of Trauma Treatment and Nerve Regeneration of Ministry of Education (BMU2021XY008-03).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgement,\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThanks to De.Testing Lab for the guidance of this study.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors Contribution\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eChen Xiong, Lijia Zhang and Yanhua Wang wrote the main manuscript text , and Xiaomeng, Kai Yu, and Jiabao Ju prepared figures and tables. Dianying Zhang and Yingze Zhang Provides the idea. All authors have reviewed and approved the final manuscript. Chen Xiong, Lijia Zhang and Yanhua Wang contribute equally to this work.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eRen Y, Hu J, Lu B, Zhou W, Tan B: \u003cstrong\u003ePrevalence and risk factors of hip fracture in a middle-aged and older Chinese population\u003c/strong\u003e. \u003cem\u003eBone \u003c/em\u003e2019, \u003cstrong\u003e122\u003c/strong\u003e:143-149.\u003c/li\u003e\n\u003cli\u003eMattisson L, Bojan A, Enocson A: \u003cstrong\u003eEpidemiology, treatment and mortality of trochanteric and subtrochanteric hip fractures: data from the Swedish fracture register\u003c/strong\u003e. \u003cem\u003eBMC Musculoskelet Disord \u003c/em\u003e2018, \u003cstrong\u003e19\u003c/strong\u003e(1):369.\u003c/li\u003e\n\u003cli\u003eİmerci A, Aydogan NH, Tosun K: \u003cstrong\u003eA comparison of the InterTan nail and proximal femoral fail antirotation in the treatment of reverse intertrochanteric femoral fractures\u003c/strong\u003e. \u003cem\u003eActa Orthop Belg \u003c/em\u003e2018, \u003cstrong\u003e84\u003c/strong\u003e(2):123-131.\u003c/li\u003e\n\u003cli\u003eSheehan KJ, Sobolev B, Guy P: \u003cstrong\u003eMortality by Timing of Hip Fracture Surgery: Factors and Relationships at Play\u003c/strong\u003e. \u003cem\u003eJ Bone Joint Surg Am \u003c/em\u003e2017, \u003cstrong\u003e99\u003c/strong\u003e(20):e106.\u003c/li\u003e\n\u003cli\u003eHoffmann MF, Khoriaty JD, Sietsema DL, Jones CB: \u003cstrong\u003eOutcome of intramedullary nailing treatment for intertrochanteric femoral fractures\u003c/strong\u003e. \u003cem\u003eJ Orthop Surg Res \u003c/em\u003e2019, \u003cstrong\u003e14\u003c/strong\u003e(1):360.\u003c/li\u003e\n\u003cli\u003eSocci AR, Casemyr NE, Leslie MP, Baumgaertner MR: \u003cstrong\u003eImplant options for the treatment of intertrochanteric fractures of the hip: rationale, evidence, and recommendations\u003c/strong\u003e. \u003cem\u003eBone Joint J \u003c/em\u003e2017, \u003cstrong\u003e99-B\u003c/strong\u003e(1):128-133.\u003c/li\u003e\n\u003cli\u003eZhang C, Feng J, Wang S, Gao P, Xu L, Zhu J, Jia J, Liu L, Liu G, Wang J\u003cem\u003e et al\u003c/em\u003e: \u003cstrong\u003eIncidence of and trends in hip fracture among adults in urban China: A nationwide retrospective cohort study\u003c/strong\u003e. \u003cem\u003ePLoS Med \u003c/em\u003e2020, \u003cstrong\u003e17\u003c/strong\u003e(8):e1003180.\u003c/li\u003e\n\u003cli\u003eMeinberg EG, Agel J, Roberts CS, Karam MD, Kellam JF: \u003cstrong\u003eFracture and Dislocation Classification Compendium-2018\u003c/strong\u003e. \u003cem\u003eJ Orthop Trauma \u003c/em\u003e2018, \u003cstrong\u003e32 Suppl 1\u003c/strong\u003e.\u003c/li\u003e\n\u003cli\u003eHaidukewych GJ, Israel TA, Berry DJ: \u003cstrong\u003eReverse obliquity fractures of the intertrochanteric region of the femur\u003c/strong\u003e. \u003cem\u003eJ Bone Joint Surg Am \u003c/em\u003e2001, \u003cstrong\u003e83\u003c/strong\u003e(5):643-650.\u003c/li\u003e\n\u003cli\u003eRoberts KC, Brox WT: \u003cstrong\u003eFrom evidence to application: AAOS clinical practice guideline on management of hip fractures in the elderly\u003c/strong\u003e. \u003cem\u003eJ Orthop Trauma \u003c/em\u003e2015, \u003cstrong\u003e29\u003c/strong\u003e(3):119-120.\u003c/li\u003e\n\u003cli\u003eRoberts KC, Brox WT, Jevsevar DS, Sevarino K: \u003cstrong\u003eManagement of hip fractures in the elderly\u003c/strong\u003e. \u003cem\u003eJ Am Acad Orthop Surg \u003c/em\u003e2015, \u003cstrong\u003e23\u003c/strong\u003e(2):131-137.\u003c/li\u003e\n\u003cli\u003eZhang dianyin, Zhang Xiaomeng, Yu Kai, Zhao Xiaotao: T\u003cstrong\u003ehe relationship between fracture fixation and internal and external factors\u003c/strong\u003e \u003cem\u003eChinese shoulder and elbow surgery electronic journal \u003c/em\u003e2018, \u003cstrong\u003e6\u003c/strong\u003e(02):81-84.\u003c/li\u003e\n\u003cli\u003eZhang Dianying, Yu Kai, Yang Jian, Zhao Xiaotao, Zhang Xiaomeng, Wang Yanhua, Ju JiaBao. \u0026quot;Lever-fulcrum balance\u0026quot; theory: A new understanding of the treatment of intertrochanteric femoral fractures. 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In.\u003c/li\u003e\n\u003cli\u003eTucker SM, Wee H, Fox E, Reid JS, Lewis GS: \u003cstrong\u003eParametric Finite Element Analysis of Intramedullary Nail Fixation of Proximal Femur Fractures\u003c/strong\u003e. \u003cem\u003eJ Orthop Res \u003c/em\u003e2019, \u003cstrong\u003e37\u003c/strong\u003e(11):2358-2366.\u003c/li\u003e\n\u003cli\u003eKwak D-K, Kim W-H, Lee S-J, Rhyu S-H, Jang C-Y, Yoo J-H: \u003cstrong\u003eBiomechanical Comparison of Three Different Intramedullary Nails for Fixation of Unstable Basicervical Intertrochanteric Fractures of the Proximal Femur: Experimental Studies\u003c/strong\u003e. \u003cem\u003eBiomed Res Int \u003c/em\u003e2018, \u003cstrong\u003e2018\u003c/strong\u003e:7618079.\u003c/li\u003e\n\u003cli\u003eLi J, Han L, Zhang H, Zhao Z, Su X, Zhou J, Li C, Yin P, Hao M, Wang K\u003cem\u003e et al\u003c/em\u003e: \u003cstrong\u003eMedial sustainable nail versus proximal femoral nail antirotation in treating AO/OTA 31-A2.3 fractures: Finite element analysis and biomechanical evaluation\u003c/strong\u003e. \u003cem\u003eInjury \u003c/em\u003e2019, \u003cstrong\u003e50\u003c/strong\u003e(3):648-656.\u003c/li\u003e\n\u003cli\u003eGotfried Y: \u003cstrong\u003eThe lateral trochanteric wall: a key element in the reconstruction of unstable pertrochanteric hip fractures\u003c/strong\u003e. \u003cem\u003eClin Orthop Relat Res \u003c/em\u003e2004(425):82-86.\u003c/li\u003e\n\u003cli\u003eHaq RU, Manhas V, Pankaj A, Srivastava A, Dhammi IK, Jain AK: \u003cstrong\u003eProximal femoral nails compared with reverse distal femoral locking plates in intertrochanteric fractures with a compromised lateral wall; a randomised controlled trial\u003c/strong\u003e. \u003cem\u003eInt Orthop \u003c/em\u003e2014, \u003cstrong\u003e38\u003c/strong\u003e(7):1443-1449.\u003c/li\u003e\n\u003cli\u003eMirzaei M, Keshavarzian M, Naeini V: \u003cstrong\u003eAnalysis of strength and failure pattern of human proximal femur using quantitative computed tomography (QCT)-based finite element method\u003c/strong\u003e. \u003cem\u003eBone \u003c/em\u003e2014, \u003cstrong\u003e64\u003c/strong\u003e:108-114.\u003c/li\u003e\n\u003cli\u003eHsu CE, Shih CM, Wang CC, Huang KC: \u003cstrong\u003eLateral femoral wall thickness. A reliable predictor of post-operative lateral wall fracture in intertrochanteric fractures\u003c/strong\u003e. \u003cem\u003eBone Joint J \u003c/em\u003e2013, \u003cstrong\u003e95-B\u003c/strong\u003e(8):1134-1138.\u003c/li\u003e\n\u003cli\u003eEvans EM: \u003cstrong\u003eThe treatment of trochanteric fractures of the femur\u003c/strong\u003e. \u003cem\u003eJ Bone Joint Surg Br \u003c/em\u003e1949, \u003cstrong\u003e31B\u003c/strong\u003e(2):190-203.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-1837198/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-1837198/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eBackground:\u003c/p\u003e\u003cp\u003eReverse intertrochanteric fracture is an unstable type of fracture. Current guidelines recommend intramedullary fixation, but there are still complications such as screw removal, hip varus, nail withdrawal, and nail fracture. The objective of this study was to use finite element analysis to compare the biomechanical properties of the novel proximal femoral bionic intramedullary nail (PFBN), proximal femoral anti-rotation intramedullary nail (PFNA) and combined compression interlocking intramedullary nail (InterTan) in the treatment of reverse obliquity\u0026nbsp;intertrochanteric\u0026nbsp;fractures [AO/OTA 31-A3.1].\u0026nbsp;\u003c/p\u003e\u003cp\u003eMethods:\u003c/p\u003e\u003cp\u003eThe three-dimensional models of PFBN, PFNA, InterTan and the A3.1 intertrochanteric fracture model were established by using modeling software such as Mimics and Unigraphics. Different force loads were implemented using ANSYS software to compare finite element biomechanical parameters, such as maximum stress in the implant and maximum stress and displacement at the proximal femur.\u0026nbsp;\u003c/p\u003e\u003cp\u003eResults: \u003c/p\u003e\u003cp\u003eIn this finite element study, we found that the distribution trend of maximum femoral stress and displacement in the femoral model of the three internal fixation groups was similar, but the maximum stress and maximum displacement were the lowest in the PFBN group, and the maximum stress of the internal fixation implant in PFBN group was lower than that in the PFNA group and the InterTan group. The maximum stress and displacement of the femur in the PFNA group were 403.71MPa and 14.274mm, the maximum stress and displacement in the InterTan group were 362.72MPa and 10.678mm, and the maximum stress and displacement in the PFBN group were 186.23MPa and 9.7068mm.In the internal fixation implant model, the maximum stress of the PFNA group was 1445MPa, the maximum stress of the InterTan group was 919.62 MPa, and the maximum stress of the PFBN group was the lowest, 911.77MPa.\u0026nbsp;\u003c/p\u003e\u003cp\u003eConclusion:\u003c/p\u003e\u003cp\u003eCompared with PFNA and InterTan, PFBN designed by the lever - fulcrum - reconstruction theory can provide better biomechanical stability. It is a feasible choice for the future treatment of reverse intertrochanteric fracture.\u003c/p\u003e","manuscriptTitle":"Finite Element Analysis of Proximal Femur Bionic Nail (PFBN), Froximal Femoral Anti-rotation Intramedullary Nail and InterTan for Treatment of Reverse Obliquity Intertrochanteric Fractures","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2022-07-22 16:37:38","doi":"10.21203/rs.3.rs-1837198/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"f04a5a5c-51ab-497a-b33d-36b7b1ee21d8","owner":[],"postedDate":"July 22nd, 2022","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2022-12-02T17:31:37+00:00","versionOfRecord":[],"versionCreatedAt":"2022-07-22 16:37:38","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-1837198","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-1837198","identity":"rs-1837198","version":["v1"]},"buildId":"ApUGefWb6u5IBVtyqm6d5","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}