Effect of Degenerative Change of Lumbar Spine on Lateral Bone Mineral Density Measurement Using Dual EnergyX-ray Absorptiometry: Usefulness of Measurement in the Supine Lateral Projection

PURPOSE: To evaluate the usefulness of supine lateral bone mineral density (BMD) measurement using DXA bycomparing AP and lateral spine BMD in patients with degenerative change. MATERIALS AND METHODS: Six hundred andseventy-two women underwent AP and lateral BMD measurement of L-spine, using DXA. Spur changes and end-platesclerosis were considered as degenerative change, and osteoporosis was defined according to WHO criteria. Theratio of mid-lateral BMD to AP BMD was calculated and the differences in ratio were analyzed in the degenerativegroup and controls, according to aging and osteoporosis, using the t test and ANOVA. The correlation coefficiencybetween aging and AP BMD and lateral BMD, respectively, was calculated. RESULT: The mLat/AP ratio in the controland degenerative group was 0.710(0.005 / 0.622(0.028 (p=0.003) in the 40-49-year-old group, 0.663(0.006 /0.612(0.016 (p=0.002) in the 50-59-year-old group, 0.626(0.015 / 0.552(0.023 (p=0.007) in the 60-69 year-oldgroup, and 0.717(0.028 / 0.600(0.045 (p=0.076) in those aged over 70. The ratio was 0.656(0.015 / 0.598(0.038(p=0.099) in osteoporosis, 0.684(0.008 / 0.596(0.016 (p=0.000) in osteopenia, and 0.688(0.005 / 0.583(0.019(p=0.000) in normal subjects, showing that lateral BMD is more sensitive than AP BMD, especially in thedegenerative group. There was negative correlation between aging and AP BMD(r= -0.545), lateral BMD(r= -0.571),and mid-lateral BMD(r=-0.583). CONCLUSION: In a selective group of patients with degenerative change, supinelateral BMD measurement of L-spine is useful.

Differentiation between Osteoporotic and Metastatic Vertebral Compression Fractures by MRI

PURPOSE: To evaluate the MRI findings helpful in differentiating between osteoporosis and metastatic vertebral compression fracture. MATERIALS AND METHODS: This study involved 52 patients with nontraumaticvertebral compression fracture; 23 had osteoporosis and 29, metastatic diseases. We retrospectively analyzed signal abnormality and the extent to which bone marrow was seen within the involved vertebral body, sharpness of margin of abnormal signal intensity, morphological characteristics of the vertebral endplate, and the presence or absence of posterior element involvement and paraspinal mass, as seen on T1- and T2*-weighted MR images. For statistical analysis, the chi-square test was used. RESULTS: In 14 of 23 patients (61%) with osteoporotic benign compression, and 27 of 29 (93%) with metastatic compression fracture, the bone marrow of the compressed vertebral body showed both low signal intensity on T1-weighted image and high signal intensity on T2-weighted image. In 13 of 14 osteoporotic compression fractures, the extent of abnornal bone marrow signal was incomplete, but in 20 of 27 metastatic compression fractures, this was complete. In all 13 cases of osteoporosis, incomplete abnormal signal showed a sharp margin, whereas in five of seven metastatic compression fractures, this margin was ill-defined. Morphologically, the endplate was concave in 20 of 23 osteoporosis cases (87%), but was angled in 13 of 29 metastatic compression fractures (45%). Only the latter showed vertebral posterior element involvement (21/29) and paraspinal mass (16/29). CONCLUSION: The extent of signal abnormality, margin of compressed bone marrow, morphologic characteristics of the endplate, and the presence or absence of posterior element involvement and paraspinal mass on T1- and T2*-weighted MR images, as described above, may be helpful in differentiating between benign osteoporotic and malignant metastatic compression fractures.