| Objectives: To test the mechanical load of the fixed adult femoral shaftfracture model with new type intramedullary nail and interlockingintramedullary nail using the finite element analysis, compare both strain andstress distribution characteristics. To analyze and verify the feasibility of newtype intramedullary nail fixing adult femoral shaft fracture biomechanics.Simultaneously, to propose indications for surgery, determine the newintramedullary nail in fixed adult femoral shaft fractures can replace theinterlocking intramedullary nailing has become a safe, effectiveintramedullary fixation by comparing.Femoral shaft fracture is a fracture proximal femoral lesser trochanter tothe femoral condyle. Femoral shaft fracture is one of the most commonfracture in clinical. It accounted for18.5%of the limbs fractures andaccounting for6%of the body fractures[1], its overall incidence rate is births1.33[2]. Femur is the longest bone of the human body, It is also one of thelower limb the main load-bearing bone. Adult femoral shaft fracture is oftendue to damage by high energy. There are more complications after the fracture.If not treated properly, will seriously affect the quality of life of patients andeven threaten the lives of patients. Today's adult femoral shaft fractures tend tofixation treatment because of the non-surgical treatment of time in bed, morecomplications, with internal fixation materials, surgical methods continue toimprove as well as fractures in the concept of change. The plate andintramedullary nail is gradually being used in the treatment of femoral shaftfractures since the19th century. The intramedullary nail is more in line withthe mechanical properties of bone, often as a treatment of primary choice forfemoral shaft fractures[3]. Initial intramedullary nail to rely on the friction of the nail and the medullary cavity to control the fracture site stability, however,this fixed only to a certain extent against the stress generated by the bendingload.it does not provide enough against the axial load and rotation load stress.So this is often caused by the shortening and rotation displacement of thefracture fragments. Today interlocking intramedullary nail is a good solutionto this problem. However, after a large number of clinical cases observed, Itwas found that interlocking intramedullary nail compared with otherintramedullary nails have better axial and rotary fixation. Interlockingintramedullary nail is still not reliable enough to stump stability for complexfemoral shaft fractures, such as the type of Winquist III, IV, sections offemoral shaft fractures. To solve this problem, scholars have made numerousattempts such as auxiliary plate fixation and improvements of shape ofintramedullary nail[4]. But these are not a fundamental solution to the ends ofmicro. Lock principle was gradually accepted by clinicians with the advent oflocking plate. It is widely used clinically because of ability to screw lockedwith steel plates to form an overall increase of fixed stability and persistence.But locking plate compared to the central fixed differential in the mechanicalproperties due to its eccentric fixation.To this end, we improved the design of a new intramedullary nail on thebasis of the interlocking intramedullary nail by combining with intramedullarynailing and locking the advantages of the steel plate. Its principle is to providea reliable stability of the fracture fragments by changing the main-nailedcross-section shape, increasing the number of nail holes of the main nailed tothe cross, changing the position of the transverse nail holes and locking thehorizontal nail and nail.The finite element analysis[5]can achieve the purpose of analysis of theelastomer by dividing a continuous elastic body into a finite number of cell,synthesizing study using the finite element software in the computer, studyingthe nature of each unit to ensure the similarity with the actual object of studyin the structure, physical parameters, materials, texture and mechanicalproperties. This method is mainly used in the biomechanical study in the medical field. Human body is a complex mechanical structure, biomechanicsexperiments are often difficult to directly applied to human. Finite elementanalysis which be used as an effective method for people to deepenunderstanding of the characteristics of the human body mechanics cansimulate the biomechanical behavior. Its effectiveness, the advantages havebeen fully proven in the basic experiments and clinical applications.Methods:1To establish the new type intramedullary nailing of adult femoral shaftfracture of the finite element model as the experimental group, theestablishment interlocking intramedullary nail fixed adult femoral shaftfractures in finite element model as a control group on the basis of a finiteelement model of the adult femoral shaft fractures, a new type intramedullarynail and the interlocking intramedullary nail.2To test the experimental group and control group model axial load, lateralbending and torsional loads, as well as eight times the weight of the static anddynamic mechanical load using finite element analysis software respectively.3To observe stressed and strained characteristics of two groups of modelunder the axial loads, lateral bending loads and torsional loads, and eight timesthe weight of the static and dynamic mechanical load test, and analyze theresults, finally, reach a conclusion.Results: The femur, nails, and horizontal nail has a stress concentrationzone In the load tests. New type intramedullary nail group cross nail stressmore evenly, while the interlocking intramedullary nail group cross nail stressvalues vary greatly.1The maximum stress values and displacement values at fracture fragments offemur, nail and transverse nail in the new type intramedullary nail guorp areless than the interlocking intramedullary nail group under vertical loads of235~700N,but are more under vertical loads of1400N,2100N.2The maximum stress values and deflection at facture fragments of femur,nail and transverse nail in the new type intramedullary nail guorp are less thanthe interlocking intramedullary nail group under bending loads of 200~600N,but are more under bending loads of800N,1000Nï¼›The maximumstress values of the horizontalnails of a new type intramedullary nail group aregreater than the interlocking intramedullary nail group under Bending loads.3The maximum stress values and displacement values at fracture fragments offemur, nail and transverse nail in the new type intramedullary nail guorp areboth less than the interlocking intramedullary nail group under torsional loadsof2~15Nm.4The maximum stress values of femur, nail and transverse nail of the newtype intramedullary nail are both less than yield strength of material, while themaximum stress values of femur are less than the maximum intensity of thecortical bone under static and dynamic mechanical loads of eight times thebody weight.Conclusion:1New type intramedullary nail to be able to meet the requirements for theinternal fixation of long bone fractures, especially complex femoral shaftfractures owing to reasonable structure design and Good biomechanicalproperties, to be a safe, reliable internal fixation.2New type intramedullary nail levy applies to all interlocking intramedullarynail fixed adaptation,but should avoid premature and excessive weight-bearing.3New type intramedullary nail has a unique advantage in the resistance torotation, and to be able to instead of the interlocking intramedullary nail to acertain exten.The above conclusions are preliminary study of the biomechanics beforethe experiment, also need further examination in future research confirmed. |
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