Ultrasound for the assessment of bone quality in preterm and term infants.

OBJECTIVE: As 80% of intrauterine bone mineralization takes place during the last trimester of pregnancy, preterm infants should be supplemented postnatally with optimal doses of calcium, phosphate and vitamin D. Calcium and phosphate excretion in the urine may be used to monitor individual mineral requirements, but are sometimes difficult to interpret. The objective of this study was to assess the value of quantitative ultrasound (QUS) for the analysis of bone status in neonates. STUDY DESIGN: All admissions to three independent tertiary neonatal intensive care units were studied. In 172 preterm and term infants with a gestational age between 23 and 42 weeks (mean 33.8±5.0) and a birth weight from 405 to 5130 g (mean 2132±1091 g) bone status was evaluated prospectively by quantitative ultrasound velocity using a standardized protocol. Infants were followed in regular intervals up to their first discharge home. While measurements were conducted in weekly intervals initially (n=55), 2-week intervals were regarded as sufficient thereafter due to limited changes in QUS values within the shorter period. Infants with a birth weight below 1500 g were followed during outpatient visits until up to 17 months of age. RESULT: The intra-individual day-to-day reproducibility was 0.62%. QUS-values from the first week of life correlated significantly with gestational age and birth weight (r=0.5 and r=0.6; P<0.001). Small-for-gestational-age infants showed lower values for QUS than appropriate-for-gestational-age infants allowing for their gestational age. Follow-up measurements correlated positively with age and weight during the week of measurement (r=0.2 and r=0.4; P=0.001). Comparing bone quality at 40 weeks of age in infants born at term versus infants born at 24 to 28 weeks, preterm infants showed significantly lower QUS than term infants (P<.0001).There was a significant correlation of QUS with serum alkaline phosphatase (P=0.003), the supplementation with calcium, phosphate and vitamin D (P< 0.001 each), as well as risk factors for a reduced bone mineralization. No correlation was found between QUS and calcium or phosphate concentration in serum or urine. CONCLUSION: QUS is a highly reproducible, easily applicable and radiation-free technique that can be used to monitor bone quality in individual newborns. Further prospective randomized-trials are necessary to evaluate, if therapeutic interventions based on QUS are able to prevent osteopenia of prematurity.

Experimental hip fracture load can be predicted from plain radiography by combined analysis of trabecular bone structure and bone geometry.

UNLABELLED: Computerized analysis of the trabecular structure was used to test whether femur failure load can be estimated from radiographs. The study showed that combined analysis of trabecular bone structure and geometry predicts in vitro failure load with similar accuracy as DXA. INTRODUCTION: Since conventional radiography is widely available with low imaging cost, it is of considerable interest to discover how well bone mechanical competence can be determined using this technology. We tested the hypothesis that the mechanical strength of the femur can be estimated by the combined analysis of the bone trabecular structure and geometry. METHODS: The sample consisted of 62 cadaver femurs (34 females, 28 males). After radiography and DXA, femora were mechanically tested in side impact configuration. Fracture patterns were classified as being cervical or trochanteric. Computerized image analysis was applied to obtain structure-related trabecular parameters (trabecular bone area, Euler number, homogeneity index, and trabecular main orientation), and set of geometrical variables (neck-shaft angle, medial calcar and femoral shaft cortex thicknesses, and femoral neck axis length). Multiple linear regression analysis was performed to identify the variables that best explain variation in BMD and failure load between subjects. RESULTS: In cervical fracture cases, trabecular bone area and femoral neck axis length explained 64% of the variability in failure loads, while femoral neck BMD also explained 64%. In trochanteric fracture cases, Euler number and femoral cortex thickness explained 66% of the variability in failure load, while trochanteric BMD explained 72%. CONCLUSIONS: Structural parameters of trabecular bone and bone geometry predict in vitro failure loads of the proximal femur with similar accuracy as DXA, when using appropriate image analysis technology.