| BackgroundIntertrochanteric fracture with subtrochanteric fracture is a serious unstable fracture,which was classified into type 5 by Seinsheimer in the1970 s.Seinsheimer type V is intertrochanteric fracture with subtrochanteric fracture.The operative treatment of Seinsheimer’s V fracture is extremely difficult,which is the difficulty of clinical treatment.The occurrence of such fractures is usually bimodal.After the occurrence of Seinsheimer’s V fracture,unless there is an absolute contraindication to surgery,early surgical treatment and early functional exercise should be performed,otherwise it will cause serious complications,even lifethreatening.In younger patients,the intertrochanteric Seinsheimer V fracture is mainly due to high-energy violence,while in older patients it is mainly due to osteoporosis.Due to the rapid development of the transportation industry,construction industry and the rapid increase of the elderly population in recent years,the number of patients with Seinsheimer V fracture is also increasing.In recent years,the occurrence and discussion of this kind of fracture have become more and more frequent.The studies and literatures on this kind of fracture mainly include clinical retrospective analysis,meta-analysis or case report.The domestic and foreign literatures have reported the discussion on the operation time,blood loss,complications and healing time of different treatment methods for this kind of fracture successively.In addition,all literatures do not have completely unified standards for the treatment of such fractures.Due to the lack of biomechanical studies related to Seinsheimer’s V fracture,a set of finite element analysis experiments were designed for this study.Firstly,through retrospective analysis,57 cases of intertrochanteric Seinsheimer V fracture treated in our hospital from 2020.3 to 2022.6 were reviewed,and then biomechanical finite element analysis was conducted according to the internal fixation method used in clinical treatment.This paper studied the stress distribution under different motion states after fixation of intertrochanteric fracture with subtrochanteric fracture by four internal fixation devices(proximal femoral locking plate PFLP,Inter TAN intramedullary nail,extended Gamma3 intramedullary nail and proximal femoral anti-rotation intramedullary nail PFNA).Finally,combined with the results of finite element analysis and retrospective analysis.To compare which internal fixation has better postoperative recovery effect for this kind of fracture,so as to choose a more reasonable fixation method for clinical use.ObjectiveIn order to further increase the success rate of surgical treatment for such fractures,reduce operation time,increase fixation effect and reduce postoperative complications,finite element analysis and clinical retrospective analysis were used to simulate such fractures and fix them with different internal fixation devices.The stress and displacement nemo gram under different motion states were obtained by applying loads and combined with clinical data.To provide mechanical basis and reference for future clinical treatment.methodThrough retrospective analysis,57 cases of intertrochanteric Seinsheimer V fracture treated in our hospital from 2020.3 to 2022.6 were reviewed,and then three-dimensional finite element analysis software was used to establish fracture models and 4 kinds of internal fixation devices.Intertrochanteric fracture with subtrochanteric fracture was divided into three groups: 1.Intertrochanteric fracture combined with subtrochanteric fracture can restore bone support.2,intertrochanteric combined with subtrochanteric fracture lower medial trochanteric crushing group;3,intertrochanteric combined with subtrochanteric fracture subtrochanteric comminuted fracture group.Four kinds of internal fixation devices(proximal femoral locking plate,Inter TAN intramedullary nail,Gamma3 intramedullary nail,proximal femoral anti-rotation intramedullary nail PFNA)were installed on the fracture mechanics models of the three groups,and three conditions(bipedal standing,single standing and walking)were simulated for each group of fracture internal fixation devices.The stress nephogram of the femur and the fracture end displacement of the 36 groups of internal fixators in 3 fracture models under 3 loads of 4 internal fixators were obtained,and the fixation effect between internal fixators was compared,providing a mechanical reference for clinical treatment.Through the comparison between groups and the experimental setting standard,the acceptable state of movement was obtained to guide the postoperative functional exercise.The main observation indexes of finite element analysis in this paper were the peak von-Mises Stress(MPa),the relative displacement(mm)and the total elastic deformation(mm)of the fracture end of the femur and internal fixator in fracture models fixed with different internal fixators under three different loads.According to the review of relevant literature,the setting criteria of this experiment are as follows:(1)When the bone stress of femur is greater than 120 Mpa,bone absorption > bone growth will lead to bone absorption around the internal fixation device,and eventually lead to the failure of internal fixation.(2)The maximum stress peak of titanium alloy internal fixation device and 450 MPa will lead to irreversible deformation of titanium alloy internal fixation;Therefore,when the stress of the internal fixation device is greater than 450 MPa,the failure of the internal fixation device is considered in this study.(3)When the displacement of the fracture end is greater than 0.5mm,the study believes that the effect of fracture fixation is poor,which will eventually lead to poor fracture union or even non-union.ResultsIn retrospective analysis,there was no significant difference between Inter TAN,Gamma and PFNA in fixation effect,healing time and complications,and only Gamma 3 and PFNA were superior to Inter TAN in operation time.In the finite element analysis,in the fracture model with restored bone support,four internal fixation devices(Inter TAN intramedullary nail,proximal femur locking plate,Gamma3 intramedullary nail,proximal femur square rotation intramedullary nail PFNA)were used to treat intertrochanteric fracture with subtrochanteric fracture,and the stress values of the femur and internal fixation device were the highest during walking in all three motion states.The stress peaks of femur and internal fixation were 96.566MPa\342.82 MPa,157.12MPa\299.67 MPa,88.835MPa\542.78 MPa and 98.098 MPa \ 552.24 Mpa respectively.In the case of intertrochanteric combined subtrochanteric fracture,lower medial trochanteric fracture or complete subtrochanteric comminuted fracture,the plate group reached the yield limit only under small vertical load.In the case of lower medial trochanteric comminuted fracture and subtrochanteric comminuted fracture,When three other internal fixation devices(Inter TAN intramedullary nail and Gamma3 intramedullary nail PFLP)were used to fix these fractures,the stress peaks of femur and internal fixation devices were: :111.84MPa\396.66MPa111.63 MPa \459.48 MPa、112.99 MPa \469.34 MPa、和 74.801 MPa\461.63 MPa、77.07 MPa \510.22 MPa、73.521 MPa \461.73 MPa.Based on the above data,it can be seen that Inter TAN has the best stress dispersion effect and fixation effect among the four internal fixation devices in this study.ConclusionIn the treatment of intertrochanteric Seinsheimer V fracture,Inter TAN has the best stress dispersion under various loads,and the best anti-rotation effect due to its special double-nail system structure,and the minimum displacement at the fracture end.In the fracture model with nonrecoverable bone support,the same Inter TAN group showed the best performance in all working conditions,with the best fixation effect and anti-rotation ability.Therefore,extended Inter TAN therapy is preferred for internal fixation regardless of whether the medial support can be restored.In addition,in some cases where intramedullary pin fixation is not possible due to narrow femoral bone marrow space,large anterior arch,child fractures,incomplete proximal epiphysis or pathological fractures,congenital malformations and other reasons,proximal locking plate can achieve the effect of fixing fracture end without weight bearing,but only when the stability of medial support is restored.The proximal locking plate is used for early loading.However,due to the common subtrochanteric comminution of such fractures,perfect anatomical reduction cannot be achieved in the clinic,and only a small displacement will not be able to carry out perfect conduction through the medial bone trabecula.Therefore,when using proximal locking plate fixation,patients should be asked not to bear weight in the early stage,and only carry out non-weight-bearing functional exercise in the early stage,otherwise the plate fracture will be caused. |
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