| With China entered the aging society gradually,and accelerate the process of city development,transportation and construction industry,in recent decades,the proximal femoral fracture incidence increased significantly,and is considered to be one of the most serious health problems the elderly facing.Relevant literature is expected in the next 40-50 years,the world’s annual incidence of proximal femoral fractures will exceed 7 million.According to the traditional classification,subtrochanteric fracture of femur fracture is very common in the proximal femoral fracture,which accounted for 10-34% of hip fracture.The age distribution of patients with subtrochanteric fracture of the femur was in the shape of double peaks,young patients are men,mainly caused by high-energy injury,while older patients are usually female,because often associated with osteoporosis,lower energy violence can lead to subtrochanteric femoral fracture.If with non surgical treatment,long time immobilization,improper care may cause hypostatic pneumonia,bedsore and deep vein thrombosis and other complications,and nonunion,malunion and delayed healing are common.Based on the causes and risks of this series,the current consensus is that the femoral subtrochanteric fractures should be treated with internal fixation.With the developmentthe of internal fixation materials and improvement of methods,the clinical internal fixation devices in the treatment of femoral subtrochanteric fracture is also more and more,can be divided into four categories: extramedullary fixation device,intramedullary fixation device,external fixation and artificial joint replacement.The external fixation devices include dynamic hip screw(DHS),dynamic condylar screw(DCS),proximal femoral anatomic locking plate(PFLP)and percutaneous compression plate(PCCP or LISS).Intramedullary fixation device including Russell-Tayler reconstruction nail and proximal femoral nail(PFN)and anti-rotation proximal femoral nail(PFNA),Asian anti-rotation proximal femoral nail(PFNA-II),Gamma nail,InterTAN nail etc.But because of the subtrochanteric femoral neck site and dry transfer force,lateral stress is not balanced;Fractures are mostly long segment comminuted,often involving small trochanter,the formation of medial wall defects of unstable fractures;tuberosity below the narrow part of the cortical bone area,the broken end of the contact surface is less;proximal by iliopsoas muscle,gluteus,external rotators,powerful effect of distal adductor,fracture displacement,stress persists after reduction.The above characteristics make the fracture mechanical and mechanical fixation requirements is very high,but the subtrochanteric femoral fracture fixation has no uniform standard,reasonable choice of internal fixation is a long-term problem plagued clinicians.At the same time by searching the relevant medical literature was informed that currently on the biomechanical studies of subtrochanteric fracture were no more,no ever have the clinical efficacy analysis and three dimensional finite element analysis of proximal femoral anatomical locking plate(PFLP)and InterTAN nail fixation for the treatment of subtrochanteric fractures InIn this study,the authors used the Intertan nail system and the proximal femoral anatomic locking plate system(PFLP)(both developed by smith&nephew)for the treatment of subtrochanteric fracture of femur.The first part of the paper discusses the effect of PFLP and InterTan internal fixation in the treatment of subtrochanteric fracture.The second part discusses the three dimensional finite element analysis of proximal femoral anatomic locking plate(PFLP)and InterTAN intramedullary nail in subtrochanteric fracture to better guide the clinical treatment of the clinical data and provide the basis for the corresponding theory of fracture mechanics.Part one:Clinical analysis of PFLP and InterTan internal fixation in the treatment of femur subtrochanteric fractureObjective: to compare the efficacy of proximal femoral anatomical locking plate(PFLP)and InterTan internal fixation in the treatment of subtrochanteric fracture of femur.Methods: 70 cases of subtrochanteric fracture were treated with the InterTan or PFLP were analyzed retrospectively from 2010-05 to 2015-05,PFLP group(n =34)and InterTan group(n = 36).Compare the 2 groups of operation time,blood loss,hospitalization time,fracture healing time,limb full weight-bearing time,VAS score of postoperative 7 days,6 weeks and 3 months,Harris hip score of postoperative 6 weeks,3 months,6 months,12 months and postoperative complications.Results: 70 cases were followed up for 12~36(21.52 + 3.11)months.The operation time and blood loss in InterTan group were lower than those in PFLP group,the difference was statistically significant(P < 0.05).There was no significant difference between the 2 groups in hospitalization time,fracture healing time,and limb full weight-bearing time(P > 0.05).See table 1.The VAS score of InterTan group was lower than that of PFLP group at 7 days and 6 weeks after operation,the difference was statistically significant(P<0.05),but the VAS score of 3 months after operation was no significant difference between the 2 groups(P > 0.05).The Harris hip score of InterTan group was higher than that of PFLP group at 6 weeks after operation,the difference was statistically significant(P < 0.05);but the Harris score of 3,6,12 months after operation were no significant difference between the 2 groups(P > 0.05).Conclusions: Both InterTan and PFLP internal fixation can be used as an effective method for the treatment of subtrochanteric fractures of the femur.However,the operation time of InterTan was shorter,the amount of blood loss was less,the postoperative pain was lighter,which was beneficial to the early postoperative functional recovery.Part two:Three dimensional finite element analysis of PFLP and InterTan internal fixation in the treatment of femur subtrochanteric fracturePurpose: Establish three-dimensional finite element model of instable subtrochanteric fracture and PFLP and InterTan,Separate assembly,calculation,analysis and study of the biomechanical characteristics,provide mechanical theoretical basis for the choice of clinical internal fixation,improve the prognosis of patients,improve the quality of life.Methods: Establish three dimensional finite element models on the basis of CT scanning data of femur,PFLP and InterTan,and established three dimensional finite element model of instable subtrochanteric fracture by using the three-dimensional finite element model of the intact femur.According to the operation requirements of the Department of orthopedics,the fracture and internal fixation model were assembled.After setting the boundary conditions,material properties,friction coefficient and contact relationship,with the same loading method,the stress distribution and displacement of different models were analyzed,and the maximum stress and displacement of the femur and internal fixation were compared.Results: Simulation the stress condition of the hip joint in the single leg during the gait of the body weight with 70 Kg,three dimensional finite element model of intact femur was loaded.The stress distribution and displacement degree are consistent with the traditional biomechanical experiment results.Under the same stress loading condition,PFLP internal fixation fracture model has the bigger maximum displacement value of the internal fixation device and the bigger maximum displacement value of the proximal femur than InterTAN internal fixation fracture model.But InterTAN internal fixation fracture model has the bigger maximum stress value of the internal fixation device,the bigger Maximum stress value of proximal femur than PFLP internal fixation fracture modelConclusions: Both PFLP and InterTan can be used as an effective surgical treatment for instable subtrochanteric fracture.But the InterTan system can provide better internal fixation effect. 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