| Objective:To construct a three-dimensional model of ONFH in computer and determine the site and volume of necrosis so as to establish the three-dimensional morphology of necrosis and to investigate its clinical efficacy and accuracy.Method:A total of 92 hips(59 cases) with ONFH of ARCOⅡstage(44 males, 15 females) were included in this study,the patients had the mean age of 37.5 years-old(range,26-58 years-old).Of these,the pathogenesis were steroid of 20 cases(35 hips),alcohol of 31 cases(49 hips),trauma of 4 cases(4 hips) and idiopathic necrosis of 4 cases(4 hips).All 92 hips were diagnosed as ARCOⅡof ONFH under MRI,three-dimensional CT with thick of 1mm and gap of zero was used on each hip to acquire the DICOM data of hip. The images were put into self-designed software for get the profile of femoral head and necrosis site and measure the volume and percentage of necrosis site.The femoral head collapse was looked as final follow-up;the cases without developing collapse were followed up at least 24 months.The difference of necrosis volume between digital femoral head and real femoral head were analyzed by t-test using SAS9.1.The necrosis volume among different pathogenesis and their correlativeness with collapse were analyzed either.Of the cases necessitating THA due to progressing to ARCOⅢor above,8 cases were selected randomly,and three-dimensional CT scan was performed prior to THA.After THA,the total femoral heads were separated from neck and divided into 5-6 pieces,after removal of the necrosis tissue, the approximate volume of femoral head and necrosis site were measured,after that,the results were compared those acquired from three-dimensional model. Result:Under reconstructed model,the necrosis site mainly located in superiolateral site of femoral head,which were concordance with from specimen.The rate of necrosis vohme/total femoral head of 58 collapsed hips measured under computer was 36.8%±12.5,while that in 34 hips with no collapse was 17.3%±5.2.In collapsed femoral heads,the distribution of necrosis site was as following:23.4%±8.7 in q1,23.6%±11.7 in q2,12.1%±8.1 in q3,14.4%±7.9 in q4,9.0%±6.8 in q5,11.8%±7.9 in q6,1.6%± 2.6 in q7,3.9%±5.3 in q8;While those in femoral heads without collapse were as following:34.2%±5.8 in q1,29.6%±14.9 in q2,11.8%±9.8 in q3, 11.3%±12.1 in q4,6.0%±8.1 in q5,6.0%±6.8 in q6,0.5%±2.5 in q7,0.4%±1.3 in q8.The total volume of femoral head measured in computer was 50251.05±5630.49mm~3,while that measured in specimen was 50855.53±6056.49 mm~3,with a gap of 604.48±114.6 mm~3 between each other,which showed no statistical difference(P=0.179).The total volume of necrotic site measured in computer was 21756.48±3065.88mm~3,while that measured in specimen was 22213.67±2785.76mm~3,with a gap of 457.19±849.71mm~3 between each other,which showed no statistical difference(P=0.172).In all cases, rate of necrotic volume/ total femoral head was 33.55%±5.8 in steroid, 26.74%±9.6 in alcohol,40.41%±10.3 in trauma and 18.39%±4.7 in idiopathic. There was significant difference among each pathogenesis(F=2.720,P=0.035). The morphology of 92 hips constructed under computer was defined as following: vault shape,sublobe shape,dumbbell shape,ball shape and section of an orange shape.Necrosis caused by steroid was vault shape in 23 hips,sublobe shape in 3 hips,dumbbell shape in 2 hips,ball shape in 6 hips and section of an orange shape in 1 hip.Necrosis caused by alcohol was vault shape in 21 hips,sublobe shape in 6 hips,dumbbell shape in 7 hips,ball shape in 8 hips and section of an orange shape in 7 hips;Necrosis caused by trauma was vault shape in 1 hip,no sublobe shape and dumbbell shape,ball shape in 3 hips and no section of an orange shape;Necrosis caused by idiopathic was vault shape in 1 hip,no sublobe shape and dumbbell shape,ball shape in 2 hips and section of an orange shape in 1 hip.In 58 corrupted femoral hips,there were 30 cases of vault shape,4 of sublobe shape,6 cases of dumbbell shape,12 cases of ball and 6 cases of section of an orange shape, while in 34 hips without collapse,the number was 16,5,3,7 and 3 respectively.The correlativeness between rate of necrotic volume,rate of necrotic volume in q2 and collapse(P=0.0001 and 0.0005 respectively) showed no statistical difference.The decision tree showed that when rate of necrotic volume was over 23.48%,94.6%(53/56) hips would progress into collapse.When rate of necrotic volume was less than 23.48%and rate of necrotic volume in q2 was over 45.13%,83.3%(5/6) hips would progress into collapse,while rate of necrotic volume in q2 was less than 45.13%,no collapse would occur. Conclusion:Three-dimensional reconstruction under CT scan can demonstrate the morphology of ONFH accurately and reliably,which will help surgeon better understand the morphology and orientation in femoral head.The volume and distribution of necrotic site in ONFH is correlative to the collapse of femoral head.The rate of necrotic volume play an important role in the collapse of femoral head,with the rate of necrotic volume over 23%,there were risk of developing collapse.The distribution of necrotic site can pretend later collapse,when the rate of necrotic volume is less than 23% and distribution of necrosis locate at q2(superioanteriomedial site of femoral head)/total necrotic site is over 45%,there is risk of developing collapse.
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