The Three-dimensional Finite Element Analysis Of The Osteonecrosis Of The Femoral Head And The Study Of The Clinical Effects Of Different Treatment Options

Part 1The Three-dimensional Finite Element Analysis of the Osteonecrosis ofthe Femoral HeadObjectives:The study created a three-dimensional finite element mode of the ONFH for the purpose that 1)calculating the different mechanical parameters and analyzing the mechanical conditions;2)calculating the mechanical parameters of ONFH with 60%involved postoperatively and analyzing the mechanical conditions.Methods:The three-dimensional finite element mode was created with the data of Virtual Chinese Human Male I.The reconstruction mode of proximal femur was input to ANSYS software and the finite element network mode was created.The groups were divided by the involvement of the lesion.The osteonecrosis region were determined by finite element nodes and grids number converting to 30%,50%and 60%area.The limited invasive operation modes were created and different loads were given.Results:The pre-operative peak surface stress strength ratio(SSR)was not more than 0.1 with different extents and loads.So that stress would not cause collapse unless more stress was loaded.For large lesions,the stress concentration at the bottom of lesion was common and SSR may be over 0.1 which may cause the micro-fracture and collapse.For large lesions,every SSR was less than 0.1 after different operations.The latter two operations' effects were much more significant,that is to say the femoral head was hard to collapse after latter two operations.Conculsions:The results revealed why the collapse of large lesion happened not in the surface but at the bottom.The reason was that the stress concentration occurred at the bottom and yield stress in the surface under limited challenge.So for the patient with ONFH,the limited weight bearing was suggested to reducing the collapse.The study demonstrated a detail condition after graft operation on large lesion ONFH. The mechanical condition improved a lot after fibular graft with screw stabilization and graft implantation.Those treatments improve the reconstruction of internal condition, prevent collapse and reduce osteoarthritis.While the simplex decompression and graft cause negative effect on mechanics,lead to regression of cartilage and result in osteoarthritis.Part 2The Study of the Clinical Effects of Different Treatment OptionsObjectives:The paper reviewed the cases of steroid osteonecrosis of the femoral head(SONFH) during JAN 2002 to DEC 2005 treated in our department.Then this paper tried to find the correspondent mechanic factors and their effect on prognosis.In the end the paper analyzed principles and the mechanic factors and intended to find specific therapy for different unstable factors and to improve the clinical effects.Methods:The involved cases were evaluated preoperatively.There were 115(207 hips)SONFH cases all together.23 cases were single hip evolved(20%),92 were both sides(80%);six hips belonged to stageⅠaccording to ARCO classification(2.9%),58 belonged to stageⅡ(28%),127 belonged to stageⅢ(61.4%),16 hips belonged to stageⅣ(7.7%);By location classification,four hips' lesion were type A(1.9%),26 were type B(12.6%),102 were type C1(49.3%),75 were type C2(36.2%);32 hips' lesion extended to class 1(15.5%),37 did to class 2(17.9%),69 did to class 3(33.3%),69 did to 33.3%;In AP view,81 hips(39.1%) did not collapse,72 hips(34.8%)collapsed within 2mm,36(17.4%)collapsed from 2 to 4mm,18(8.7%)collapsed more than 4mm;In frog lateral view,87 hips(42%)did not collapse,74 hips(35.7%)collapsed within 2mm,32(15.5%)collapsed from 2 to 4mm,14 (6.8%)collapsed more than 4mm;For 149 hips with MRI,25 hips'(16.8%)bone marrow edema(BME)belonged to stage 0,18 hips(12.1%)belonged to stage 1,59 hips(39.6%) belonged to stage 2,47 hips(31.5%)belonged to stage 3.Different treatments were taken,such as bone graft and vessel bundles implantation, core decompression(CD)and bone graft with screw support,CD and bone impaction with screw support,and traditional Chinese medicine(TCM)All of the data was analyzed by the statistical packages SPSS 15 for windows.The t test,one-way ANOVA or Kruskal-Wallis rank sum test was used for measurement data;x~2 for categorical data;Logistic regression for analysis of related factors;Kaplan-Meier curve for survivorship of the femoral head.There were 23 cases(23 hips)just took TCM as treatment,who were controlled with the group of untreated cases.Those two groups were followed up more than two years. More than two mm collapse on radiograph was used as the end point.Two groups' VAS data were compared and the survivorship was analyzed by Kaplan-Meier curve.Results:For the operation of CD and graft with screw support,the survivorship was higher in cases that stage in ARCOⅡ,lesion of C1,collapsed less than two mm.The extent of lesion and BME had no significant effect on survivorship.For the operation of CD and impaction graft with screw support,the survivorship was higher in cases that stage in ARCOⅡ,lesion of C1,extent within 300°,BME within stage 1 and collapsed less than two mm.For the operation of graft and vessel bundles implantation,the survivorship was higher in cases that stage in ARCOⅢ,collapsed less than two mm.The location of lesion,the extent of lesion and BME had no significant effect on survivorship.Conclusions:The indication of different treatment options may be as follows:1)For the operation of CD and graft with screw support,the cases are indicated that stage in ARCOⅡ,lesion of B or C1,collapsed less than two mm;2)For the operation of CD and impaction graft with screw support,the cases are indicated that stage in ARCOⅡ,stage in ARCOⅢbut collapse less than four mm and lesion of C1,lesion of type C2 and collapsed less than two mm;3)For the operation of graft and vessel bundles implantation,the cases were indicated that lesion of type C2,collapse between two and four mm,the extent of lesion more than class 3,slop like collapse,younger age,hope to delay the hip replacement and without significant change in acetabular.The hip replacement was indicated for the cases that collapse more than four mm,lesion of type C2,extent more than class 3.The indication for TCM is that lesion of type C1 or medial.And TCM improves symptoms of most cases of ONFH.