NONINVASIVE BONE MINERAL DENSITY MEASUREMENT IN THE EVALUATION OF OSTEOPOROSIS

Chemical structure, biosynthesis and synthesis of free and glycosylated pyridinolines formed by cross-link of bone and synovium collagen

This review focuses on the chemical structure, biosynthesis and synthesis of free and glycosylated pyridinolines (Pyds), fluorescent collagen cross-links, with a pyridinium salt structure. Pyds derive from the degradation of bone collagen and have attracted attention for their use as biochemical markers of bone resorption and to assess fracture risk prediction in persons suffering from osteoporosis, bone cancer and other bone or collagen diseases. We consider and critically discuss all reported syntheses of free and glycosylated Pyds evidencing an unrevised chemistry, original and of general utility, analysis of which allows us to also support a previously suggested non-enzymatic formation of Pyds in collagen better rationalizing and justifying the chemical events.

Assessment of trabecular bone mineral density using quantitative computed tomography in normal cats

The aim of this study was to assess age-related changes and anatomic variation in trabecular bone mineral density (tBMD) using quantitative computed tomography (QCT) in normal cats. Seventeen normal cats were included in this study and divided into the following 3 age groups:<6 months (n=4), 2-5 years (n=10) and >6 years (n=3). A computed tomographic scan of each vertebra from the 12th thoracic to the 7th lumbar spine and the pelvis was performed with a bone-density phantom (50, 100 and 150 mg/cm(3), calcium hydroxyapatite, CIRS phantom(®)). On the central transverse section, the elliptical region of interest (ROI) was drawn to measure the mean Hounsfield unit (HU) value. Those values were converted to equivalent tBMD (mg/cm(3)) by use of the bone-density phantom and linear regression analysis (r(2) >0.95). The mean tBMD value of the thoracic vertebrae (369.4 ± 31.8 mg/cm(3)) was significantly higher than that of the lumbar vertebrae (285 ± 58.1 mg/cm(3)). The maximum tBMD occurred at the T12, T13 and L1 levels in all age groups. There was a statistically significant difference in the mean tBMD value among the 3 age groups at the T12 (P<0.001), T13 (P<0.001) and L4 levels (P=0.013), respectively. The present study suggests that age-related changes and anatomic variation in tBMD values should be considered when assessing tBMD using QCT in cats with bone disorders.

Could lower bone turnover be a cause of chest pain during childhood?

Chest pain, a frequent complaint during childhood, rarely originates from a cardiac pathology. Although it usually is idiopathic, it also could be associated with psychogenic, musculoskeletal, respiratory, and digestive disorders. This study aimed to investigate a possible relation between bone mineral density and chest pain in children. Bone mineral density and bone metabolism parameters were measured for 50 children with chest pain, and the findings were compared with those for 40 age- and sex-matched healthy children. Most of the cases (64%) were in the idiopathic group, and musculoskeletal chest pain was the second most frequent complaint (12%). Although bone mineral densities and osteocalcin levels did not differ significantly between the whole chest pain group and the control group, both were found to be lower in the musculoskeletal chest pain group than in other groups and the control group (p < 0.05). Musculoskeletal chest pain may be related to reduced bone mineral metabolism, and monitoring of risk factors is of particular importance.

Correlations between bone mineral density of the hand and other skeletal sites as measured by DXA in Chinese women and men

This study was aimed at assessing the correlations between the bone mineral density (BMD) of the hand and other skeletal sites in Chinese women and men. We measured the BMD of the total body, the anteroposterior lumbar spine (L2-L4), bilateral proximal femurs (i.e., total hip, femoral neck, and trochanter), and bilateral total hands in 363 Chinese adults (96 males, 267 females) using dual-energy X-ray absorptiometry (DXA). Data were analyzed by descriptive statistics, Student's t tests, and Pearson's correlation coefficients (r). We found that bilateral hand measurements reduced precision error by 36% as compared with a single hand measurement. Dominant hand BMD was significantly higher than nondominant hand BMD. For both the dominant and nondominant sides, hand BMD was significantly higher in males than in females. Hand BMD correlated significantly (p<0.001) with the BMD of all skeletal sites for all subjects (r=0.681-0.848), the male group (r=0.568-0.857), and the female group (r=0.687-0.859). After normal references for the Chinese population have been established, further investigations may determine the clinical usefulness of hand BMD measurement in the diagnosis of osteoporosis and the prediction of fracture risk.

Ward's triangle bone mineral density determined by dual-energy x-ray absorptiometry is a sensitive indicator of osteoporosis

OBJECTIVE

To assess the clinical utility of bone mineral density (BMD) of Ward's triangle by dual-energy absorptiometry (DEXA) as an indicator of osteoporosis in comparison with quantitative computed tomography (QCT) of the lumbar spine and DEXA of the lumbar spine and hip sites (trochanter and femoral neck).

METHODS

We conducted a retrospective study of all patients (28 men and 17 women) with decreased BMD by QCT (T-score less than -1.0) who had DEXA BMD performed at the lumbar spine and hip between October 1993 and January 1995 in our Endocrine Clinic.

RESULTS

Osteoporosis based on the World Health Organization criteria (T-score less than -2.5) was defined by QCT lumbar spine BMD in 78% of the study subjects and by DEXA of Ward's triangle in 53%, of the femoral neck in 22%, of the trochanter in 7%, and of the lumbar spine in 2%. In the men, the only DEXA BMD measurement that was sensitive for detecting osteoporosis was Ward's triangle. Of the 24 men with osteoporosis by QCT BMD, 14 were defined as having osteoporosis by DEXA exclusively at Ward's triangle. The DEXA lumbar spine BMD measurement was actually above the mean for young normal control subjects in 8 of the 24 men with osteoporosis by QCT BMD. In the 11 women with osteoporosis by QCT BMD, the DEXA BMD at Ward's triangle and the femoral neck were equally sensitive in detecting osteoporosis, whereas the DEXA lumbar spine and trochanter BMD measurements were insensitive.

CONCLUSION

DEXA BMD of Ward's triangle is a sensitive indicator of osteoporosis, particularly in men, and should be used to identify patients at increased risk for osteoporosis-related fractures.

Comparative assessment of bone mineral measurements obtained by use of dual-energy x-ray absorptiometry, peripheral quantitative computed tomography, and chemical-physical analyses in femurs of juvenile and adult dogs

OBJECTIVE

To compare bone mineral measurements obtained by use of dual-energy x-ray absorptiometry (DEXA), peripheral quantitative computed tomography (pQCT), and chemical-physical analyses and determine effects of age and femur size on values obtained for the various techniques.

SAMPLE POPULATION

Femurs obtained from 15 juvenile and 15 adult large-breed dogs.

PROCEDURE

n each femur, 7 regions of interest were examined by use of DEXA to measure the bone mineral content (BMC) and bone mineral density (BMD), and 5 were examined by use of pQCT to measure BMD. Among these, 1 region was examined by both noninvasive methods and an invasive method. Volume of the femur was determined by water displacement. Volumetric bone density (VBD) was calculated. Calcium (Ca), phosphorus (P), total Ca, and total P contents were determined.

RESULTS

DEXA- and pQCT-derived results revealed that all values increased with age in juvenile dogs. In adults, VBD and pQCT-derived BMD decreased significantly and DEXA-derived BMD increased with increasing femur length. The pQCT-derived BMD correlated well with VBD and Ca content, whereas DEXA-derived BMC was strongly correlated with Ca content. In juveniles, values correlated regardless of the technique used, whereas in adult dogs, DEXA-derived BMD did not correlate with pQCT-derived BMD, Ca concentration, or VBD unless data were adjusted on the basis of femur length.

CONCLUSIONS AND CLINICAL RELEVANCE

DEXA-derived BMD adjusted for femur length yields approximately the same percentage variability in VBD as for pQCT-derived BMD. However, pQCT-derived BMD is still more sensitive for determining variability BMD in Ca concentration, compared with DEXA-derived BMD adjusted for femur length.

Relationship between bone mineral density and radiologic scores of hands in rheumatoid arthritis

This study proposed to assess the relationship between hand bone mineral density (BMD) and radiographic scoring methods, important measures to assess the course of rheumatoid arthritis. Hand, spine, and femur BMD of 49 patients with rheumatoid arthritis and 34 age- and sex-matched healthy control subjects were measured using dual X-ray absorptiometry and the results were compared. Standard hand films of patients were scored according to five different scoring methods--Larsen method, modified Larsen method, Sharp/van der Heijde modified method, carpo:metacarpal ratio, and simple erosion narrowing score (SENS)--and were correlated with hand BMD. There was a moderate relationship between hand BMD measurements and radiologic scores. SENS was the method that correlated significantly with the highest correlation coefficient. Hand BMD correlated significantly with disease duration and c-reactive protein levels. Hand BMD in patients with rheumatoid arthritis was significantly lower than in control subjects, whereas there was no significant difference in axial BMD measurements. The advantages and disadvantages of hand BMD and radiographic scoring methods were determined. Our results indicate that hand BMD measurements may be as useful is assessing the course of rheumatoid arthritis as radiologic scoring methods. However to prove this, a well-designed reference population for hand BMD and longitudinal studies are required.

Role of risk assessment and bone density monitoring in osteoporosis

Osteoporosis and its complications are prevalent medical problems. Of the risk factors for fractures, low bone mass is the best predictor. Measuring bone density in a person with risk factors for osteoporosis can provide important information for both patient and physician when choosing clinical interventions. For patients with the disease it is a way to assess response to drug therapy. Advances in technology have made measuring bone density safer, faster, and more practical than ever. Guidelines addressing when, where, and how the test should be done are useful when deciding how to apply this technology to patient care.

Abnormalities in skeletal growth in children with juvenile rheumatoid arthritis

A review of the acquisition of peak skeletal mass in normal children and studies that have been reported for children with JRA lead to the following tentative conclusions: (1) The appendicular skeleton is predominantly the overall status of skeletal mineralization; (2) a failure to develop adequate bone mineralization is virtually universal in children with JRA and is characterized by a failure of bone formation. A failure to undergo the normal increase in bone mass during puberty is common in children with JRA and markedly decreases their potential to achieve an adequate peak skeletal mass; (3) the onset of accelerated skeletal maturation with puberty is a critical period of potential intervention in JRA. Conversely, therapeutic interventions later during adolescence offer less promise of reversal of inadequate bone mineralization; and (4) the most important therapeutic maneuver is likely to be control of the inflammation process, although there is hope, at present unsubstantiated, that supplemental dietary calcium and vitamin D, and normalization of physical activity, many lead to some "catch-up" mineralization.

Bone quality factor analysis: a new noninvasive technique for the measurement of bone density and bone strength

The sensitivity of bone mineral density (BMD) as a predictor of fracture risk is limited by the fact that this index does not take into account the geometrical and material characteristics of bone. In contrast, both BMD and bone architecture influence the quality factor (QF), the fraction of the inverse of the energy lost in one cycle of deformation. In this study we have compared the sensitivity of a QF analyzer and dual-energy X-ray absorptiometry (DXA) in detecting the changes induced by ovariectomy (OVX) on the QF, impact strength, and BMD of the femur of mature rats. QF and BMD were measured noninvasively before and 4 weeks after OVX or sham operation using a QF analyzer developed in our laboratory and a Hologic QDR 2000 bone densitometry, respectively. Impact strength was measured in excised femurs at the end of the study. The in vivo short-term precision (coefficient of variation) of the QF analyzer was 1.9%. BMD and QF measurements were highly correlated (r = 0.80,p <0.0001). At baseline, QF and BMD were similar in OVX and sham-operated rats. At 4 weeks, BMD was 14.7 + or - 0.9% lower than at baseline (p < 0.001) in OVX rats and 5.3 + or - 1.3% lower in sham-operated rats (p <0.05). QF decreased 36.0 + or - 2.8% (p <0.0001) in OVX and 10.6 + or - 3.6% in sham rats (p <0.01). As a result, at 4 weeks the difference between sham-operated and OVX rats was larger (p < 0.05) by QF than by BMD. Moreover, QF correlated better than BMD with impact strength and the difference in impact strength between sham and OVX mice was closer to that in QF than that in BMD. These data demonstrate that QF analysis is a precise technique that is more sensitive than DXA in detecting the changes in bone density and strength induced by OVX. QF analysis may represent a new, simple, and economic technique for predicting fracture risk.

Bone mineralization and bone mineral metabolism in children with juvenile rheumatoid arthritis

OBJECTIVE

To identify mechanisms of the osteopenia associated with juvenile rheumatoid arthritis (JRA) by determining parameters of bone mineralization, and bone mineral content and density (BMC and BMD), in children with JRA.

METHODS

BMC and BMD were measured by dual x-ray absorptiometry in 41 children with JRA and 62 healthy children. Serum samples were analyzed for concentrations of minerals, vitamin D, parathyroid hormone, osteocalcin, bone-specific alkaline phosphatase (BAP), procollagen I carboxy-terminal propeptide, and tartrate-resistant acid phosphatase (TRAP), and urinary excretion of deoxypyridinoline crosslinks and calcium.

RESULTS

BMD was decreased in all sites in JRA patients. BMD, corrected for age, height, weight, and bone area, was decreased at cortical bone sites (1/3 radius, upper and lower extremities, and whole body). Low concentrations of osteocalcin and BAP suggested reduced bone formation, and low TRAP levels suggested decreased resorption. Clinical scales of disease severity were negatively correlated with measures of bone mass. Laboratory markers of disease severity were highly correlated with decreases in markers of bone formation, but not with those of resorption. Although laboratory findings were similar for children with oligoarticular and polyarticular disease, differences in bone mass were greater in children with polyarticular disease.

CONCLUSION

These data suggest an association between decreased bone mineralization in JRA and low bone formation that is related to disease severity. Efforts to stimulate bone formation, therefore, need to be considered clinically in prepubertal children with active JRA.

Bone mineral metabolism in children with juvenile rheumatoid arthritis

Osteopenia has emerged as a major determinant of the outcome of children with juvenile rheumatoid arthritis. Although vertebral compression fractures and fractures of long bones were recognized historically as important clinical developments in the course of disease, a decrease in skeletal mass could only be quantitated and documented early in disease by the recent introduction of bone absorptiometry. This article is limited to recent data from studies on osteopenia in juvenile rheumatoid arthritis and suggests directions of future research that have relevance to current unanswered questions in prevention or management.