| ObjectiveHip preserving is the preferred treatment for patients with osteonecrosis of the femoral head (ONFH). However, at present clinical commonly used methods of treating ONFH mainly based on clinical experience, the biomechanical characteristics of the necrotic femoral head has no good application,also lacking the biomechanical basis. The main reason is the present clinical studies focus on biology and imaging, and the understanding and research associated with the biomechanics of collapse is insufficient. However, collapse is the result of the biological and biomechanical combined action, the ideal therapeutic method requirements from these two aspects for effective reconstruction, be short of one can not. This study in light of the present condition of the femoral head necrosis biomechanics research is insufficient, in allograft fibular graft(AFG) for example, studying normal, necrosis, postoperative changes of the biomechanical performance of the femoral head by means of computational biomechanics. At the same time, clinical retrospective study was carried out on these patients who treat with AFG in our hospital, and compared the experimental results with clinical findings, to provide effective biomechanics and clinical basis to make treatment decision in the treatment of ONFH around the time of collapse, to solve the problem of prevention and treatment for collapse ONFH making a new attempt and exploration.MethodsExperimental study:basing on the imaging data of the patient(X-ray, CT,MRI) establish the normal, necrosis and AFG three-dimensional finite element model of individualized hip respectively, research the load transfer model of the normal, necrosis, AFG head, to reveal the effective load transfer mechanism of the normal femoral head, the damage mechanism of load transfer of the necrotic femoral head and the reconstructed mechanism of the femoral head after AFG, to provide biomechanical basis for the collapse of ONFH prediction and treatment.Clinical study:This research review those patients treating ONFH by AFG in our hospital of the hip joint center on January 1,2010-March 1, 2014, and collect the patient’s X-ray, CT and MRI imaging data, sorted according to the JIC classification, operation method and so on, then carry on survival rate and COX regression analysis with class B collapse, total hip replacement for the end point event respectively, to explore the survival rate and the risk factors of the patients treated by AFG in the different end point events, to provide clinical basis for the treatment and prognosis judgement of the ONFH.ResultsExperimental study:1. Stress results of subchondral boneThe maximum stress region of subchondral bone(normal, necrosis, postoperative) appear in the top of the femoral head. The maximum mises stress of the subchondral bone increased significantly at the weight bearing area of the femoral head,32.34% more than normal. The maximum mises stress of the subchondral bone at the weight bearing area of the femoral head down 11.28% compared with before AFG.2. Stress results of necrotic regionThe maximum mises stress of the necrotic region of the femoral head decreased significantly, down 57.65% compared with normal. The maximum mises stress of the necrotic region of the femoral head increased 12.4% compared with before AFG.3. Load transfer path within the femoral headThe load transfer path within the normal femoral head is continuous is continuous, the load at the weight bearing area of the femoral head transfer along the load transfer path to calcar femorale; The normal load transmission path within the necrotic femoral head is interrupted; the load at the weight bearing area of the femoral head transfer to allogeneic fibula firstly, then transfer to calcar femorale, preliminary reconstructed the load transfer path.4.Stress results of hollow screw implantThe subchondral bone maximum stress areas are in the top of the femoral head whether cooperate with screw after AFG or not. Also, the maximum mises stress of the subchondral bone at the weight bearing area of the femoral head do not has an obvious change, only a difference of 0.57 MPa.Clinical study:1. General dataAccording to this study inclusion criteria and exclusion criteria, eligible participants included 136 patients(107 male,29 female) who undergone AFG in our hospital,17 cases of bilateral necrosis(13 male,4 female); a total of 153 hip(left 78 hips, right 75 hips),63 hips hormone necrosis,51 hips alcohol necrosis,6 hips traumatic necrosis,33 hips idiopathic necrosis;JIC classification:3 hips type A,15 hips type B,97 hips type C1,38 hips type C2; without cooperate with screw 104 hips, cooperate with screw 49 hips;Age 19-61 years (average 37.51±9.16 years); Follow-up time of 6.13-6.13 months (average 24.01±13.50 months); During follow-up 36 hips (23.53%) occurred more than class B collapse, collapse time 1.33-35.03 months (average 15.04±8.67 months), and 7 hips (4.58%) occurred total hip replacement, replacement time 16.87-16.87 months(average 22.53±5.94 months).2. Class B collapse as the end point eventsWith Class B collapse as the end point events, the 1 year,2 years,3 years,4 years,5 years survival rate are 90%±3%,74%±4%,66%±5%,66%±5%, 66%±5% respectively. After AFG with Class B collapse as the end point events the Survival rate fluctuations occurs in the first 3 years, from then on the survival rate remained stable. COX regression analysis results show that the variable JIC classification (P=0.001<0.01) was statistical significant, so JIC classification associated with postoperative femoral head survival rate significantly. The survival rate of type A and B, C1, C2 necrosis femoral head showed a trend of gradual decline, and the survival rates of type A and B is discrepant, but doesn’t give a clear trend. The gender, age, cause, affected side, the operation method and other variables (P> 0.05) have no statistical significance, so there is no correlation between the survival rate of the necrosis femoral head.3. Total hip replacement as the end point eventsWith total hip joint replacement as the end point events, the 1 year, 2 years,3 years,4 years,5 years survival rate are 100%±0%,94%±2%, 92%±3%,92%±3%,92%±3% respectively. After AFG with total hip joint replacement as the end point events the Survival rate fluctuations occurs in the first 3 years, from then on the survival rate remained stable. COX regression analysis results show that the variable JIC classification (P=0.032<0.05) was statistical significant, so JIC classification associated with postoperative femoral head survival rate significantly. The survival rate of type A and B, C1, C2 necrosis femoral head showed a trend of gradual decline, and the survival rates of type A and B is discrepant, but also doesn’ t give A clear trend. The gender, age, cause, affected side, the operation method and other variables (P> 0.05) have no statistical significance, so there is no correlation between the survival rate of necrosis femoral head.Conclusion1. AFG is a hip preserving surgery which can rebuild load transfer path within the femoral head, correct the stress concentration of subchondral bone and stress shieding, prevent collapse and promote repair for the necrotic femoral head to a certain degree in mechanics. However, the clinical curative effect is not as good as total hip replacement, but for the young patients and patients wish to get a close to normal joint is a good choice.2. The change of the biological mechanics performance within the femoral head is not only a influence factor of the collapse of the necrotic femoral head and a influence factor of the repair of the necrotic femoral head.3. Clinical healing period and imaging repair period of hip preserving of the necrotic femoral head is not equal. According to the results of this study can be speculated that the clinical healing period of AFG for the treatment of ONFH is about 3 years.4. The clinical curative effect of allogeneic fibular graft for treating ONFH associated with the JIC classification, the higher classification the worse curative effect; The gender, age, cause, affected side have no correlation between the survival rate of the necrosis femoral head. |
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