The Difference of Bone Mineral Density of Lumbar Spine and Wrist in the Preterm and Full-term Infants: Using Dual Energy X-ray Absorptiometry

PURPOSE: To assess the differences in bone mineral density (BMD) of lumbar spine and wrist between preterm infants of postconceptional age 40 weeks and normal full-term infants. MATERIALS AND METHODS: Sixty-eight preterm infants born at conceptional age 26 -36 weeks and 31 normal full-term infants born at 38 -42 weeks were investigated. Bone mineral densities of the lumbar spine (from the second to the fourth segment) and wrist were measured by dual energy X-ray absorptiometry. In preterm infants, the corrected age of 0 month was defined as postconceptional 40 weeks. Full-term infants were evaluated within three days of birth, and the average bone mineral densities of preterm and full-term infants were compared. In the preterm group, birth weight and conceptional age were correlated with lumbar spinal and wrist bone mineral densities. Data were analyzed by student's t-test and Pearson's correlation coefficient, and a pvalue of less than 0.05 was considered significant. RESULTS: In preterm in fants, the values of bone mineral densities of the lumbar spine and wrist were 0.137 +/- 0.018 g/cm2(0.061 -0.202 g/cm2) and 0.089 +/-0.013 g/cm2 (0.065 -0.123 g/cm2), respectively, while the respective values for full-term infants were 0.214 +/-0.030 g/cm2 (0.160 -0.296 g/cm2) and 0.118 +/-0.014 g/cm2(0.096 -0.162 g/cm 2). In the preterm group, lumbar spinal BMD correlated significantly with conceptional age(r=0.384, p0.05). CONCLUSION: The lumbar spinal and wrist BMDs of preterm infants at corrected age 0 were lower than those of normal full-term infants. In the preterm group, BMD values for the lumbar spine were lower in infants of lower conceptional age and birth weight.

Quantitative Morphologic Assessment of Thoracolumbar Vertebrae in Korean Women by Morphometric X-rayAbsorptiometry

PURPOSE: To compare the accuracy of lateral radiography of the spine with that of morphometric X-rayabsorptiometry(MXA) in vertebral morphometry, and to evaluate normal vertebral morphometry using MXA in Koreanwomen. MATERIALS AND METHODS: A spine phantom was constructed using copper pipe. Its anterior and posteriorheights were measured directly, with lateral radiographs and with MXA, and the values thus obtained were compared.Inter -and intra -observer variations were evaluated by three radiologists. The vertebral morphometry of 30 youngwomen volunteers were imaged using thoracic and lumbar lateral radiographs and MXA, and analysis included themeasurement of anterior and posterior heights from T4 to L4. We also obtained the vertebral morphometry of 200normal Korean women who underwent MXA between March 1995 and February 1996, though those with osteoporosis andother spinal lesions were excluded from this study. Thoracolumbar vertebral indexes were statistically correlatedwith age, height and bone mineral. RESULTS: There were no statistically significant differences in the heights ofspine phantom measured by MXA compared with actual size (mean difference=0.28mm). Simple radiographs weremagnified by 23.7% at a phantom-table distance of 15cm, and distortion ranged from 0.5% to 22.5%, depending onphantom level and phantom-table distance. In the study of volunteers, the magnification rate between a simpleradiograph and MXA was about 26.6%. Anterior height increased progressively from the thoracic to the lumbar spine,though posterior height peaked at L2, and L4 was less than anterior height. In Korean women, indices of vertebralmorphometry decreased significantly with aging, with the most prominent decrease occurring during the seventhdecade. The mineral density of spinal bone decreased markedly after the sixth decade. CONCLUSION: Radiographsshowed more magnification and distortion than did MXA, though between morphometric X-ray absorptiometry (MXA) andactual size, there was no significant difference. The vertebral morphometric indices of Korean women and referredbone mineral density may provide useful data for determining and evaluating follow-up changes in spinalmorphology.

Correlation between Osteoporosis and Skin Thickness on CT Scan

PURPOSE: The purpose of this study was to evaluate the relationship between osteoporosis and skin thicknessas shown by CT scanning. MATERIALS AND METHODS: Eighty- six women with osteoporosis (mean age, 52) and 51 normalcontrols (mean age, 50) participated in the study. For a quantitative CT examinations, a CT scanner(Somatom Plus,Siemens) was used. Osteoporosis was defined as present when spinal bone mineral density was more than 2.5 standarddeviations below young normal density, as determined by quantitative CT. Patients with endocrinologic, malignantor collagen disease and undergoing antimetabolite or steroid therapy were excluded. The thickness of back skin wasretrospectively measured at the third lumbar vertebra level, as seen on CT films, using a conventional magnifier.For statistical analysis, Students' t test and Spearman's rank correlation were used. RESULTS: On the basis of CTscans, the mean thickness of back skin in the osteoporotic group(0.50+/-0.20 mm) was significantly less than innormal control subjects(0.80+/-0.23 mm) (p<0.001). Significant correlation was observed between skin thickness andbone mineral density(r=0.523, p<0.0001). Sensitivity, specificity, accuracy, and positive and negative predictivevalues were measured as 76, 78, 76, 88, 62% with a cut-off value of 0.6 and 84, 61, 77, 81, 66% with a cut-offvalue of 0.7, respectively. CONCLUSION: The present study demonstrated that the thickness of back skin, asmeasured by CT scanning, is predictive of osteoporosis.

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.

Bone Changes in Phenylketonuria

PURPOSE: While treating 14 phenylketonuria(PKU) patients, we evaluated bone density, changes in bone age, andbony changes such as spiculation or metaphyseal widening. MATERIALS AND METHODS: A total of 14 PKU patients agedbetween 1 month and 14 years(mean, 6.4 years) were under dietary treatment. Eight and eleven patients underwentradiography of the left hand and wrist and bone densitometry(BMD) of the lumbar spine, respectively. The resultswere reviewed with regard to abnormal bony changes, delayed bone age, and osteopenia. Patients were assigned toeither the early or late treatment group, depending on whether or not dietary therapy was started before 3 monthsof age. Those in whom a blood phenylalanine level of under 10 mg/dl was maintained were assigned to the 'goodcontrol' group; others were classified as 'variable control'. The findings of radiographs of the left hand andlumbar BMD were evaluated in relation to the time of dietary therapy, and adequacy of treatment. RESULTS: Onlumbar BMD, four of 11 patients (36%) showed reduced bone density of more than 1 S.D. None of the 11 who underwentradiography of the left hand showed bony abnormalities such as spiculation or metaphyseal widening. In four of the11, bone age was less than chronological age by at least one year. According to Fisher's exact test there was norelation between delayed bone age , osteoporosis and the time and adequacy of dietary therapy (p >0.05). CONCLUSION: None of the 14 PKU patients who underwent dietary therapy had bony abnormalities such as spiculationor metaphyseal widening. In four of the 11, bone age was at least one year less than chronological age, and onlumbar BMD, osteoporosis was seen. For the evaluation of bone change in PKU patients, plain radiography and BMDare thus complementary.

Relationship between Bone Mineral Density of Lumbar Spine and Fatty Replacement of Lumbar Paraspinal Muscles by Quantitative Computed Tomography

PURPOSE: To investigate whether bone mineral density(BMD) occurs in association with fatty replacement oflower paraspinal muscles and whether it relates with the area ratio(Ps/V) of psoas muscle(Ps) divided by adjacentvertebral body(V). MATERIALS AND METHODS: For the evaluation of osteoporosis, 100 females underwent quantitativeCT. At L1,L2 and L3 levels, the fatty replacement of lower paraspinal muscles was numerically graded and therelationship between this and BMD of the vertebral body was evaluated. The correlation between BMD and Ps/V at L2and L3 levels was also evaluated, as was the relationship between the thickness of subcutaneous fat tissue at L1,L2 and L3 levels. RESULTS: BMD showed significant inverse correlations with the grade of the fatty replacement oflower paraspinal muscles at L1(p<.01), L2 level and L3 level(p<.001). In particular, significant differenceswere established between grade 0 and 2 (p<.05) at L1 level, and between grade 0 and 2, and 1 and 2 (p<.05) at L2and L3 levels. There was markedly low correlation (gamma=.33) between BMD and Ps/V at L3 level(p<.001) and lowercorrelation (gamma=.22) at L2 level(p<.05). At L2 and L3 levels, there was no correlation between the thickness ofsubcutanous fat tissue and BMD or Ps/V. CONCLUSION: The present study demonstrates that there was significantinverse correlation between BMD and fatty replacement of lower paraspinal muscles, and low correlation between BMDand Ps/V.

The Usefulness of Whole Body Bone Mineral Densitometry in the Osteopenia of Preterm Infants: Comparison with the Wrist Radiography and Biochemical Parameters

PURPOSE: To evaluate the usefulness of whole body bone mineral densitometry in the diagnosis of frequent osteopenia of preterm infants by comparison with the wrist radiographs and biochemical parameters. MATERIALS AND METHODS: From January 1995 to January 1996, we obtained whole body bone mineral density(BMD) studies using dual energy X-ray absorptiometry(DXA) and wrist radiographs of 39 preterm infants. They were divided into three groups according to birth weight, under 1500g, 1501g to 2000g and above 2000g, and four grades of skeletal change, as seen on wrist radiography, according to the scoring method of Koo et al. Groups of birth weight and grades of skeletal change were then correlated with whole body BMD and biochemical parameters. For comparison, normal data were obtained from 13 infants born at full term. Data were analyzed by one way analysis of variation(ANOVA) and correlation and regression analysis. A p-value of less than 0.05 was considered significant. RESUTLS: Whole body BMDs were significantly lower in the more premature and smaller birth weight infants(r=0.77, p=0.0000), and in the higher grade of skeletal change (r=-0.5276, p=0.0000). Aggravated skeletal changes were found in infants with lower birth weight(r=-0.3822, p=0.01). Interobserver variation in grading skeletal change was 42.9%, and intraobserver variation was 18.4%. Biochemical parameters such as serum calcium, phosphate, alkaline phosphatase, parathromone, calcitonin and 25-hydroxy-vitamine D did not vary significantly according to either birth weight or skeletal change (p>0.05). CONCLUSION: Premature osteopenia is more effectively diagnosed by measuring whole body BMD using DXA than by grading radiographical skeletal change or by biochemical parameters.