OBJECTIVETo compare the differences between computer aided identification and ultra-thin layer slicing in measuring the lesions of femoral head necrosis,and to confirm the accuracy and practicability of computer aided method.

METHODSFrom June 2012 to December 2013, the X-ray and MRI of 24 patients (24 hips on unilateral) were reviewed, who had avascular necrosis of the femoral head (ANFA) at late stage (stage III and IV) according to the ARCO international staging system. There were 15 males and 9 females, with an average age of (65.1 ± 8.8) years old, ranged 33 to 74 years old. Based on the software system with seeds point identification, the ragional adaptive search method with computer aid was used to calculate the volume of necrotic lesion in femoral on MRI. Then the pathological slices of those intraoperative femoral heads were made to measure the gross volume of necrotic lesion in femoral head,and the values were compared with the data in the computer.

RESULTSFor 24 hips, by the calculation of computer, the necrotic volume was (20.00 ± 3.04) cm (ranged, 18.72 to 21.29 cm³). Under the pathological section, the necrotic volume of the femoral head was (19.89 ± 3.17) cm³ (ranged, 18.55 to 21.23 cm³). In computer and pathology two kinds of measurement, the two entire femoral head volume had no significant difference using these two measurements (t = -1.227, P = 0.232).

CONCLUSIONComputer aided identification for necrotic area of femoral head adaptive can demonstrate the morphology of femoral head necrosis accurately and reliably, which will help surgeon better understand the morphology and orientation in femoral head.