Objective: We constructed 3D-model of ONFH in computer according to three-dimensional computerized tomography (3D-CT) data. We determined the location and volume of necrosis to investigate its clinical efficacy. Method: Totally 92 hips (59 cases) with ONFH (44 males, 15 females) were included, with mean age of 37.5 years (range from 26 to 58). Totally 20 cases (35 hips) were induced by corticosteroid (CTSs), 31 (49 hips) induced by alcohol, 4 (4 hips) induced by trauma and 4 (4 hips) idiopathic. All the hips were categorized into stage ARCO II. Finally diagnosed by MRI, all hips were scanned by CT to acquire data in DICOM format. The images were imported into software to extract 3D-shape of femoral heads, necrotic foci, their volumes and distribution in each quadrant. Deviation of volumes between digital image and biopsy specimen was analyzed by SAS9.1 package. Correlativity between collapse and volume of necrosis under specific pathogeneses was also analyzed. Among the cases necessitating total hip arthroplasty (THA) due to advancing to ARCO III, we randomly selected 8 of them to perform 3D-CT scanning thrice prior to surgical operation. Total femoral heads harvested were torn asunder. Cubic capacity of femoral heads and necrotic foci were hereby measured and compared with those acquired from digital models. Result: Through the digital model, necrotic foci were found mainly locating within the super lateral portion of femoral head, coinciding with those observed in biopsy specimen. Average volumetric ratio of digitally acquired necrosis focus/femoral head in 58 collapsed hips was 36.8%. The ratio of the 34 hips without collapse was 17.3%. In collapsed femoral heads, the distribution of necrosis focus was 23.4% in quadrant 1 (q1), 23.6% in q2, 12.1% in q3, 14.4% in q4, 9.0% in q5, 11.8% in q6, 1.6% in q7 and 3.9% in q8. In femoral heads without collapse, the distribution was 34.2% in q1, 29.6% in q2, 11.8% in q3, 11.3% in q4, 6.0% in q5, 6.0% in q6, 0.5% in q7 and 0.4% in q8. As for the average cubic capacities of femoral heads and necrotic foci, those acquired from the digital model and biopsy specimen had no significant difference in matched-pairs test (t = -1.49, P = 0.179 for femoral heads and t = -1.52, P = 0.172 for necrotic foci). There was significant difference (F = 2.720, P = 0.035 P was respectively 0.0001 and 0.0005). Decision tree model showed that 94.6% (53/56) hips would progress into collapse if the volumetric ratio of necrotic tissue was over 23.48%. Otherwise, if distribution in q2 was over 45.13%, 83.3% (5/6) hips would progress into collapse. No collapse (0/30) would occur if the distribution of necrotic tissue in q2 was under 45.13%. Conclusion: Digital 3D-model reconstructed from CT scanning can precisely incarnate spatial orientation of necrotic foci in femoral head. Multinomial logistic regression and decision-making tree shows that volumetric ratio of necrotic tissues plays an important role in anticipating collapse of femoral head.

Objective To investigate the feasibility and accuracy of volumetric measurement of necrotic lesion using CT and MRI,and to assess the value of necrotic lesion volume in predicting collapse of the femoral head in patients with avascular necrosis of the femoral head(ANFH). Methods Comparison among CT,MRI and gross section was performed in 25 femoral heads of 18 patients who underwent total hip replacement for established ANFH.The volume of necrotic lesion was measured using fluid displacement.CT and MRI data were transferred to a computer to calculate the volume of necrotic lesion using software.One way ANOVA was used to compare the volumes of necrotic lesion measured by CT,MRI and gross section.A total of 62 patients (92 hips) who were diagnosed with ANFH but without collapse by CT were followed up 24 months.Student t-test was used to compare the ratio of the volumes of the necrotic lesion and entire femoral head in the hips with and without collapse and ROC curve analysis was carried out.Results CT and MRI coincided with gross section in the necrotic area,proliferative area and extralesional area.The volumes of the necrotic lesion measured by CT,MRI and gross section were ( 20.5 ± 5.2 ),( 21.4 ± 4.8 ),( 20.9 ± 5.2 ) cm3,respectively.There was no significant difference among the necrotic volumes measured by the three methods(F =0.185,P =0.831 ).In fifty-seven out of 92 hips,collapse of the femoral head occurred during the follow-up.The ratio of the volumes of the necrotic lesion and entire femoral head was higher in hips with collapse than in hips without collapse[ (34.5 ±9.3)％ vs.(23.4 ±8.4)％ ;t =5.749,P=0.000].The area under the ROC curve was 0.808. Conclusions The volume of the necrotic lesion plays an important role in the collapse of femoral head in patients with ANFH.Both CT and MRI can identify the shape and location of the necrotic lesion intuitively and stereospecifically and can determine the volume of the necrotic lesion accurately.