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Analysis
of in vivo 1H Magnetic Resonance Spectroscopy in Osteonecrosis
of Femoral Head
HC
Shon1, JS Chang2
1Department of Orthopedic Surgery, Chungbuk National University, College
of Medicine, Chungju, Korea, and 2Department of Orthopedic Surgery,
Asan Medical Center, University of Ulsan College of Medicine, Ulsan,
Korea
Introduction: Proton magnetic resonance spectroscopy (1H MRS) is a powerful non-invasive technique used to identify and quantify the chemical compounds. In recent study, the early histopathologic findings of osteonecrosis shows marrow edema and hemorrhage, and the late findings are fibrous marrow transformation with new bone formation. The purpose of this study is to apply 1H MRS to the bone marrow of osteonecrosis and bone marrow edema syndrome by measuring the amount of lipid relative to water of femoral head and greater trochanter.
Materials and Methods: MR imaging and MR spectroscopy were performed in twenty five patients (male: female = 17:8, age = 29-69 years) who were diagnosed osteonecrosis and bone marrow edema syndrome and compared with three normal control group. Twenty three cases were osteonecrosis and two were bone marrow edema syndrome. Ficat stages of osteonecrosis in femoral head were the stage I for 1 patient, II for 8, and III for 14. Osteonecrosis was developed in 14 patients with steroid therapy after kidney transplantation, in 6 alcoholics, and 3 idiopathic. After routine hip MRI, spectroscopy was obtained from T2 weighted image by 3-dimensional localization technique. Locations of voxels were the center of the osteonecrotic zone verified by T2-weighted MR images and from the fat marrow in greater trochanter of femur. The values of the [Lipid/Water] ratios were calculated for all patients.
Results: The average Lipid/Water ratio of osteonecrotic area was 3.15, those of greater trochanter was 6.45, compared with 10.28 in normal control group. The MRS pattern for osteonecrosis could be divided into 4 patterns: A, Lipid/Water > 10 ; B, 3 < Lipid/Water £ 10; C, 0.3 £ Lipid/Water < 3; D, Lipid/Water £ 0.3. The numbers of cases for each pattern were 1 in A, 6 in B, 10 in C, and 6 in D. Interestingly, in one patient with Ficat stage I osteonecrosis diagnosed by only bone scintigraphy, 1H MR spectroscopy revealed much higher lipid/water peak ratio compared with normal control group. The average Lipid/Water ratio of the bone marrow edema syndrome was 0.71.
Conclusions: This study revealed decreasing pattern of lipid content as osteonecrosis progresses, which correlates with histopathologic results. In bone marrow edema syndrome, reverse pattern to normal control group was found. Further study is needed for the change of Lipid/Water ratio in early change of osteonecrosis.