Mechanics Research For Reconstruction Technique On Femoral Intertrochanteric Fracture With Lateral Wall Instability

Part?: Three-dimension finite element analysis of reconstruction technique on femoral intertrochanteric fracture with lateral wall instabilityObjective We aimed to study biomechanical property of reconstruction technology used to treat femoral intertrochanteric fracture by three-dimension finite element analysis.Methods We established the three-dimension finite element models of femur of one old female volunteer,intramedullary nail and reconstruction plate through spiral CT scanning technique and related software.Then we established models of simple femoral intertrochanteric fractures and fractures with lateral wall instability.After that,we divided models into three groups.Simple fracture models treated by Proximal Femoral Nail Anti-rotation(PFNA)fixation were in group A,fracture models with lateral wall by PFNA fixation were in group B,and fracture models with lateral wall by PFNA fixation combined with reconstruction plate were in group C.When fixation was finished,models in every group were analyzed by software ANSYS to test displacement of fracture sites and stress distribution of femur,PFNA and reconstruction plate under different levels of axial compression and torsion.Results A.Under axial compression condition,stress was distributed mostly on basement of proximal femoral neck of models in group A,and was on interior distal part of fracture in group B and C.The stress on interior distal part of fracture and the lateral displacement of fracture sites of three groups were both sorted in descending order as group B,C and A,and the interior displacement of fracture sites was sorted as group C,B and A.The lateral displacement was bigger than the interior one.B.Under torsion condition,stress was distributed mostly on basement of proximal femoral neck of models in group A,on interior distal part of fracture in group B and on distal nails of construction plates in group C.The stress on interior distal part of fracture and the lateral displacement of fracture sites of three groups were both sorted in descending order as group B,C and A,and the interior displacement of fracture sites was sorted as group C,B and A.The lateral displacement was bigger than the interior one.C.Under combined working condition,there were no significant difference of maximum displacement,stress distribution and stress intensity among three groups.Conclusion A.More displacement of fracture sites and lower stability in femoral intertrochanteric fracture become obvious with lateral wall instability.B.Stress will concentrate on interior distal part of femoral intertrochanteric fracture with lateral wall damage.C.The stress concentration could be reduced though construction of lateral wall by construction plate,as well as the displacement of lateral fracture ends.Part ?: In vitro biomechanical study on reconstruction technology on femoral intertrochanteric fracture with lateral wall instabilityObjective We aimed to study biomechanical property of intramedullary nail fixation combined with reconstruction technology used to treat femoral intertrochanteric fracture.Methods We took 18 femurs from 9 adult corpse donors which were conformed as no osteonosus and divided them into three groups at random.Femurs in group A were modeled as AO type 1.1 femoral intertrochanteric fracture and fixed with short intramedullary nails,femurs in group B were modeled as AO type 1.1 femoral intertrochanteric fracture with lateral wall damage and fixed with short intramedullary nails and femurs in group C were were modeled as AO type 1.1 femoral intertrochanteric fracture with lateral wall damage and fixed with short intramedullary nails combined with reconstruction plate repairing lateral wall.After that,we measured the displacement of fracture ends and relative displacement between internal fixation and medullary space in three groups under axial static loading,cyclic loading and torsion loading.Results A.Under axial compression condition,different static and cyclic compression load from 300 N to 700 N were orderly applied on proximal femur.The displacement of fracture sites of three groups were gradually increasing with increasing load,which was consistent with the result of finite element analysis.The medial and the lateral displacement of fracture sites of three groups were both sorted in descending order as group B,C and A,which were statistically significant.Relative displacement between internal fixation and medullary space in three groups under cyclic loading had no statistically significance to one another.The medial and lateral displacement was bigger than the interior one.B.Under torsion condition,different static and cyclic torsion load within 8N.m were orderly applied on proximal femur.The medial and the lateral displacement of fracture sites of three groups were both sorted in descending order as group B,C and A,which were statistically significant.The medial and lateral displacement was bigger than the interior one.Conclusion A.More displacement of fracture sites and lower stability in femoral intertrochanteric fracture become obvious with lateral wall instability,which was consistent with the result of finite element analysis.B.The rotate degree result from torsion load could be reduced though construction of lateral wall by construction plate,as well as the displacement of lateral fracture ends,which can provide patients with early function rehabilitation after operations.