BACKGROUND:The distribution of the necrotic area plays an important role in hip preservation treatment.At present,there are few studies on whether the difference in the three-dimensional spatial distribution of osteonecrosis of the femoral head affects the clinical outcome of fibular support. OBJECTIVE:To explore the relationship between the spatial distribution and clinical outcome at the sites of osteonecrosis of the femoral head and fibular support using CT three-dimensional reconstruction so as to provide a basis for optimizing the applicable conditions of fibular support and improving the hip preservation effect of fibular support. METHODS:Eighty patients with osteonecrosis of the femoral head who were treated with fibular support for hip preservation from January 2010 to January 2021 were selected as the study subjects according to the inclusion criteria.They were followed up for at least 2 years.According to the clinical outcome,the patients were divided into the successful hip preservation group(n=55)and the failure hip preservation group(n=25).3D reconstruction was performed according to the preoperative and postoperative CT images of the patients.According to the three-column theory,the femoral head was divided into outer nine areas,middle nine areas and inner nine areas(L1-9,C1-9,and M1-9)to explore the spatial distribution of necrotic area of the femoral head and fibular support area and its relationship with clinical outcome. RESULTS AND CONCLUSION:(1)Before operation,the necrotic area of the femoral head was mainly distributed in L1,L2,L4,L5,C1,C2,C4,and C5(the upper and middle part of the anterior part of the outer ninth area and the middle part of the middle ninth area).After operation,the fibular support area was mainly distributed in L5,L6,C5,and C6(the middle and lower part of the outer ninth area and the middle and lower part of the middle ninth area).(2)There were significant differences in the distribution of osteonecrosis of the femoral head between the successful hip preservation group and the failure hip preservation group in L8(the posterior middle part of the outer ninth area),C3(the anterior lower part of the middle ninth area),C6(the lower middle part of the middle part of the inner ninth area)and M2(the anterior middle part of the inner ninth area)(P<0.05).There was a significant difference in the distribution of fibular support in L5 and L6(middle and lower part of outer nine)(P<0.05).Among them,the L8 region could be used as an independent predictor of hip preservation failure in fibular support surgery.The area under the curve of the L8 single factor prediction model was 0.698[95%CI(0.575,0.822)];the sensitivity was 76%,and the specificity was 63.6%.(3)It turns out,when the necrotic area involves L8,C3,C6,and M2,especially L8,the failure of fibular support may increase,and when the fibular support involves L5 and L6,the effect of hip preservation is often not ideal.