Experimental Study Of Predicting The Collapse Of The Femoral Head By Determining Its Bone Defect Area

Objective: For the past few years, the incidence of nontraumatic osteonecrosis of the femoral head ( NONFH ) has grown gradually. It is an serious influence for patient's physical and mental health. This Disease can lead to femoral head collapse. So, it is wery important to intervenes positively in the early time, resumes femoral head's blood supply, improve the biomechanical properties of the femoral head and prevent femoral head collapse. Learn from the past results at MRI and three-dimensional finite element study, we makes the bone defect model of femoral head on animal bones and the defect area of these models is precisely progressive. These models are use to simulate the varying degree in the femoral head necrosis. Through to study the change of the index of the biomechanical and the bone mineral density in these models, We want to verify the past results of clinical observation and computer technology , research the critical bone defect area of femoral head necrosis collapse, proposes the opportunity and strategy of the prevention of the femoral head necrosis collapse and the safe range of the bone transplant operation of femoral head.Method: We select 100 fresh femurs of healthy 6-7 month-old meat used landrace, cut open them from the middle coronal plane of the femoral head after the determination of bone mineral density, takes the anterior half piece ( main weight-bearing area of femoral head ) as experimental materials. Divides them into 10 groups according to the design of randomized block, each group of 10. we make the experimental model at weight-bearing area of femoral head by using cartography,measuring tool,desk-top driller, rubs bits, oscillating saw and Imaging equipment as assisted. All models are passed through the 64 shot CT scanning and immersed in the normal sodium in order to verify the scope of bone defect is precise. 1~10 group of specimen's damage scopes respectively are 0%, 17%, 22%, 28%, 33%, 39%, 50%, 67%, 83% and 100%. Then determine the mechanical properties ( Yield load ) of these models.Result: After statistical analysis, according toα=0.05 standard, the yield load of each group models are different ( P<0.0001 ), according to the comparable result of arbitrary two groups, we can think that between of the 4th group with 1~3 groups and 7~10 group, the yield load has significant differences and we still could not think that between 1~3 groups, 4~6 groups and 7~10 group, the yield load of the femoral head model has differences.Conclusion:1 We can make the bone defect level of the experimental model accurate, quantitative, and progressive increases at weight-bearing area of femoral head by using cartography, measuring tool, desk-top driller, rubs bits, oscillating saw and imaging equipment as assisted.2 The femoral head necrosis collapse or not is closely related in the necrotic area. The bone defect which is result from the interior cystic change of femoral head will lead to decline in biomechanical properties, When the defect size achieves above 28%, the risk of collapse of the femoral head is increased, especially when the volume surpasses 50%, the risk is further intensified.3 The operate position should be accurate during the decompression of the femoral head and bone graft surgery. We should determine the cavity size of the bone defect by C-arm X-ray machine after the necrotic bone tissue is removed. For the patients of ARCOⅠB,ⅡA～ⅡB, the cavity size should be avoided to exceed 30% of the volume of femoral head as far as possible and for the patients of ARCOⅠC,ⅡC, the cavity size should be avoided to exxceed 50%.In the operation, we should pay particular attention to the protection of subchondral bone plate.