Basic And Clinical Study For Restoration And Reconstruction Of Osteonecrosis Of The Femoral Head

1 ObjectiveOsteonecrosis of the femoral head(ONFH) is a disaster disease of clinical orthopaedics, the rule of necrosis to collapse then to osteoarthritis is inevitable if it was not proper treated. The ability of walking will partially or completely lose, and ONFH may have a major impact on these patients' quality of life. Total hip replacement is applied for the patients older than 50 years. Surgical treatment of osteonecrosis is preservation of the femoral head to avoid a total hip arthroplasty for younger with more activities. Preservation of the femoral head is the goal of various treatments. There are lots of methods including nonvascularized bone grafting, osteotomy of proximal femur, vascularized bone flaps grafting, free vascularized fibula grafting, vascularized periosteum grafting and branch blood vessel transplantation. All this procedures are effective for the precollapse cases, while the case results and the hip function of femoral head after collapse are poor. So it will be an important subject to find a convenient and less invasive procedure for all stages of ONFH. On the foundation of biomechanics and anatomy, this study is to cure ONFH by applying bi-vascularized bone flap of greater trochanter to different location of the lesion.2 Materials and Methods2.1 The biomechanical Study in Predicting collapse in Ischemic Necrosis of Femoral HeadFirst scanning a upper femur specimen with SCT, dealing the two-dimensional image with Efilm software, identifying the outline of the femoral head by range estimation, inputting coordinate value of the femur into the computer to build up three-dimensional finite element model of the upper femur by Ansys-5.7 software, then simulating cystic degeneration of lcm diameter by analogue computer, at last put three kinds of pressure on the femoral head respectively to analyse ihe stress distribution and the stress/strength ration and predict the collapse of the femoral head.2.2 Design of anatomy studyThe courses and distribution of transversal and middle gluteus medius branches of lateral femoral circumflex artery together with morphology and blood supply of middle gluteus medius were observed on 52 lower limbs cadavers which were ferfused with red emulsion. To evaluated the feasibility of restoration and reconstruction of the femoral head by simulate the incised greater trochatiter bone flap pedicled with double blood vessels. Collected data was analyzed by using SPSS.2.3 Clinical research2.3.1 Cases selectionStage ARCO II-III cases were selected according to clinical symptoms, signs and radiography findings.2.3.2 Treatment projectsTo renovate and reconstruct the femoral head by applying greater trochanter bone flap pedicled with double blood vessels according to the degrees and joint cartilage on foundation of biomechanical analysis and anatomy studying.2.3.3 Observation index and evaluation standard ?Clinical symptoms and signsObservation of clinical symptoms and signs were evaluated according to Harris score.This hundred-mark system standard including pain, viability, walking ability,joint deformity and range-of-motion.?Radiography findingsIf X-rays or CT showed positive findings according to ARCO radiography contents, MRI and ECT were not recommended?Evaluation standarda.Joint function improvedb.Osteonecrosis were stable on postoperative X-raysc.No further treatments of THR were requiredIt is effectively that if the outcome achieved a and b or c standard.2.4 Radiography study of haemodynamic changing in the femoral head perioperativelyHaemodynamic of femoral head renovated with transplanting greater trochanter bone flap pedicled with transversal branch of lateral femoral circumflex artery and gluteus medius branches was evaluated by Digital Subtraction Angiography.3 Results3.1 The biomechanical study in restoration and reconstruction of ONFHEstablished three-dimensional finite element model of the femoral head had 21852 nodal points and 10472 units, this model had advantage of high grid density and analyzing precision. The straining in femoral head decrease progressively from superior part to inferior part after the lateral-superior ellipse loading area of the femoral head was bearing compressive stress, and the straining of the loading area was maximum. The stress in femoral head was increasing gradually with the additional loading. The stress in loading area of femoral head was 3.93mm with 2.75w load, it was 9.83mm while the load was 15w.The stress was maximum in the loading area and it was similar in other areas of the femoral head; the tension of the upper femoral neck was maximum but compressive stress occurs in the inferiorborder. The compromised strength of femoral head subcartilage bone lamella was 82.3Mpa, while cancellous bone was 13Mpa. So the stress-tolerance power of subcartilage bone lamella was higher.Full of granulation tissue occurred in of necrotic femoral head. Modulus of elasticity was lMpa,the stress was blocked after arrived this area, and compressive stress concentrated in the boarder of cystis degeneration. In coronal plane of the femoral head, the stresses of cystis degeneration 0.5cm under cartilage(number 1,4,5) were obviously. The stress in femoral head was increasing gradually with the load additionally especially for number 1,because of the nearest position to the loading area. The stress alteration of subcartilage and cancellous bone was under high stress status and decreasing but high tension occurred when the stress arrived superior board as well as inferior part. The straining in loading area of femoral head was 3.93mm with 2.75w load, it was 9.83mm while the load was 15w.So the stress around the cystis degeneration showed tensional concentration, not compressive stress. Number 5 had intension to collapse because of rounding with tension and closed to the tension area of the femoral neck. But the first broken area was subcancellous bone, when stress of femoral head was 15w load, the subcancellous bone of 1,4,5 cystis degeneration broke because of over compromised strength. The ratio of stress/strength was 1.5,1.32,1.38, while the ration of superior boarder of number 1 was 0.8.After repeatedly stress stimulus would be broken too. When the cyst locates in the anterior and posterior parts of the femoral head, its upper edge displays tension concentration but not obvious and the stress/strength ratio of the cancelious bone beneath the articular surface is smaller than normal and the danger of collapse is little. The central part of the femoral head displays stress, the anterior and posterior part of the femoral head displays tension, which is in conformity with the principle of ball expansion after being compressed.3.2 Anatomy studyGreater trochanter bone flap pedicled with transversal branch of lateral femoral circumflex artery or gluteus medius branch or hereinbefore double blood vessel and periosteum graft pedicled with transversal branch were incised from cadaver based on anatomy study could be transferred to the femoral head area conveniently.3.3 Clinical researchThe follow-up was 5~18 months (mean 11 months). The outcome of recent follow-up was satisfied and no further treatment required except function rehabilitation. No worse progressive finding on the X-ray accord to the ARCO standard of ONFH. Harris score assessment improved individually compared with preparation in the latterly follow-up.(score ranged from 56 to 72,mean 79)3.4 Radiography study of haemodynamic changing in the femoral head perioperatively.To evaluated the haemodynamic changes in the femoral head after treatment with using of vascularized bone flaps by Digital Subtraction Angiography. Digital Subtraction Angiography was performed in 12 hips with ONFH stage II and III according to the classification system. Five were stage II and 7 were stage in. Procedure was done through tansfemoral approach and traversing the aortic bifurcation, the catheter advanced into the contralateral femoral artery. Subtraction was continued up to disappearance of the contrast medium. DSA demonstrated abnormal findings in all 12 hips with ONFH and the blood supply to femoral head was impaired in 6 hips while abnormal changes of venous system were observed in 4 hips. Using vascularized bone flaps proved the haemodynamic change in ONFH.4 Conclusion4.1 The cystic degeneration locates in different part of the femoral head influences the biomechanical mechanism differently, which shows different collapseprobability of the femoral head. The stress analysis basing on three-dimensional finite element theory can predict the collapse of the femoral head and guide the appropriate microsurgical treatment.4.2 Various greater trochanter bone (periosteum) flaps could be transferred conveniently to the junction between femoral head and neck or the lower part of femur. The vessel pedicle without tension or twisted, which applied the quest of restoration and reconstruction by transferring vascularized bone flaps for the femoral head, femoral neck fracture and nonunion or defect of lower femur.4.3 Recent clinical follow up found that greater trochanter bone flap pedicled with transversal branch of lateral femoral circumflex artery and glutens medius branch could be used for the treatment of ONFH. This method could restore large lesions and improve blood supply to resolve the key problem of treatment for ONFH. This procedure will improve the curative effect of preserving head treatment of ONFH and expand the application of greater trochanter bone flap.4.4 Greater trochanter bone flaps pedicled with transversal branch of lateral femoral circumflex artery and gluteus medius branch was applied in this group to restore and reconstruct of the osteonecrotic femoral head. Preoperative DSA finding confirmed the diagnosis and postoperative DSA proved the blood supply of the femoral head reconstructed.