Assessment of the risk of vertebral fracture in menopausal women

Conservative Treatment of Carpometacarpal Dislocation of the Three Last Fingers

Posterior carpometacarpal (CMC) dislocation is a rare condition. Treatment is usually surgical though no strict consensus can be found upon literature review. If diagnosed early and no associated fractures are found, CMC dislocation could benefit from conservative treatment comprising closed reduction and splint immobilisation. We report the case of a 26-year-old man diagnosed with a posterior dislocation of the third, fourth, and fifth CMC joints after a fall of 1.5 meters, treated by external reduction under procedural sedation and immobilisation with a cast for 6 weeks. Evolution was excellent with no relapse observed during follow-up. Our aim is to increase physician awareness of CMC dislocation so that they seek this injury in the emergency department. Unrecognised CMC dislocation can lead to neurovascular injuries as well as chronic instability and early articular degeneration.

Comparison of vertebral and femoral bone mineral density in adult females

[Purpose] This study assessed vertebral and femoral bone mineral density in adult females. [Subjects and Methods] A total of 314 females in their 40s to 70s were divided into normal, osteopenia, and osteoporosis groups and their vertebral and femoral bone mineral densities were compared. [Results] Comparisons of T scores revealed significant differences among measurements of the third lumbar vertebra, femoral neck, Ward's triangle, and femoral trochanter. Pearson correlation coefficients were used to assess differences between the vertebral and femoral measurements, and significant differences and positive correlations were observed among third lumbar vertebra, femoral neck, Ward's triangle, and femur trochanter in the normal group. [Conclusion] Females in the normal, osteopenia, and osteoporosis groups showed significant differences in their third lumbar vertebrae. The lack of significant differences among measurements in the osteoporosis group in this study suggests that patients with osteoporosis require careful and accurate diagnosis.

Carpometacarpal Joint Fracture Dislocation of Second to Fifth Finger

Background

Carpometacarpal joint fracture dislocation of the second to fifth finger is a rare hand injury associated with high energy trauma. Due to severe swelling and overlapping of bones on the radiograph of wrist-hand, dislocations are missed. We reported a series of six patients with rare carpometacarpal joint fracture dislocation treated with open reduction.

Methods

We retrospectively studied six cases of carpometacarpal joint fracture dislocation. All patients were treated with open reduction and internal fixation with Kirschner wire. Functional assessment was done with Quick Disabilities of the Arm, Shoulder and Hand score (Quick DASH score) at regular intervals.

Results

Average Quick DASH score was improved from 75.76 to 1.9 from 6 weeks to 18 months of duration. Of the six patients, three patients had a Quick DASH score of 0 at the end of 18 months.

Conclusions

Careful hand examination and radiographic assessment is necessary to avoid missed diagnosis of carpometacarpal joint fracture dislocation. Early open reduction and internal fixation lead to excellent recovery of hand function.

Bone tissue compositional differences in women with and without osteoporotic fracture

It is generally accepted that the hallmark of osteoporosis is a reduction in bone mass. There is significant overlap, however, in bone mineral density between osteoporotic and normal individuals. This study examined the chemical composition of bone tissue obtained from women who had sustained a fracture and women without fracture to determine if there are differences between the two groups. Nineteen fractured and eleven non-fractured proximal femurs were obtained, matched for age and bone volume fraction obtained from micro-computed tomography. Trabecular bone specimens were examined by Raman spectroscopy to determine measures of chemical composition. A subset of the specimens was utilized to compare locations at the fracture and regions at least 2 mm away from apparent tissue damage using Raman spectroscopy. In addition, fifteen iliac crest biopsies each were obtained from women who had sustained a fracture and from normal controls. Raman spectroscopy was used to determine measures of chemical composition of trabecular and cortical bone. The results demonstrated that femoral bone tissue in the region of visible damage had a trend towards differences compared to regions at least 2 mm from visible damage. Femoral trabecular bone in fractured women had a higher carbonate/amide I area ratio than in unfractured women. Iliac crest biopsies revealed a higher carbonate/phosphate ratio in cortical bone from women who had sustained a fracture. Results suggest that the chemical composition of bone tissue may be an additional risk factor for osteoporotic fracture.

Transcutaneous fiber optic Raman spectroscopy of bone using annular illumination and a circular array of collection fibers

Transcutaneous bone Raman spectroscopy with an exciting annulus of 785-nm laser light surrounding the field of view of a circular array of collection fibers is demonstrated. The configuration provides distributed laser light. The annulus is located 2 to 3 mm beyond the edge of the field of view of the collection fibers to reject contributions from skin and other overlying tissues. Data are presented for rat and chicken tissue. For rat tibia, the carbonate/phosphate ratio measured at a depth of 1 mm below the skin is in error by 2.3% at an integration time of 120 s and within 10% at a 30-s integration time. For chicken tibia 4 mm below the skin surface, the error is less than 8% with a 120-s integration time.

Relationship between low back pain in post-menopausal women and mineral content of lumbar vertebrae

Until recently, chronic low back pain in post-menopausal women was commonly attributed to osteoporosis. This opinion has since been challenged on many counts, but controversy persists. The objective of this study was to examine this relationship. In 67 post-menopausal women, the mineral content of the lumbar vertebrae was measured by dual-energy X-ray absorptiometry and the age-normalized bone mineral index (ANBMI), the Z-score, was determined. Mean ANBMI in 40 subjects who complained of chronic low back pain (Group 1) was compared with mean ANBMI in the 27 who did not (Group 2). Pain intensity and related disability were quantified using standard questionnaires. Their respective correlations with ANBMI index and age at onset of menopause were examined. Correlation coefficients and significance of group differences were examined by appropriate statistical methods. The results showed that the mean ANBMI in Group 1 subjects was 96.5 +/- 16.9%, in Group 2 subjects it was 88.6 +/- 10.0%. Neither pain intensity nor disability was correlated with ANBMI. A weak but significant positive correlation was noted between body mass index and intensity of low back pain (r = 0.37; P < 0.05). The occurrence and severity of chronic low back pain in post-menopausal women, and the disability thereof, appear to be unrelated to the mineral content of lumbar vertebrae.

Dorsal hamatometacarpal fracture-dislocation in a gymnast

A rare case of unstable hamatometacarpal joint fracture-dislocation in a gymnast is presented. It was treated conservatively with successful outcome.

Load sharing within a human lumbar vertebral body using the finite element method

STUDY DESIGN

A finite element parametric study was performed to investigate the structural roles of the vertebral cortical shell and the trabecular centrum.

OBJECTIVES

To address the debated issue of the relative load-carrying role of the vertebral cortical shell.

SUMMARY OF BACKGROUND DATA

Several experimental and computational studies have been aimed at quantifying the load-carrying roles of the human vertebral cortical shell and trabecular centrum. These studies, however, have supported no consensus.

METHODS

A finite element model of three lumbar vertebral bodies was developed to predict the fraction of the total compressive load acting on the lumbar vertebral body, under two different loading conditions, that was supported by the cortical shell. Parametric variations in vertebral material and geometric properties were examined to determine how this fraction was influenced by such changes.

RESULTS

The fraction of the compressive load supported by the cortical shell was found to be strongly dependent on the distance from the endplate, increasing from about 34% at either endplate to approximately 63% at the midtransverse plane. This fraction was independent of the loading characteristics, proportional to the properties of the cortex, and inversely proportional to the modulus of the centrum. Additionally, the cortical shell force fraction was affected significantly by changes in the overall vertebral geometry.

CONCLUSIONS

Our findings indicate that the structural dominance of the cortical shell and centrum alternate depending on the location within the vertebral body. However, as age-related bone loss progresses, the load-carrying role of the cortical shell could increase significantly.

Low bioavailable testosterone levels predict future height loss in postmenopausal women

The objective of this study was to examine the relation of endogenous sex hormones to subsequent height loss in postmenopausal women, in whom height loss is usually a surrogate for osteoporotic vertebral fractures. This was a prospective, community-based study. The site chosen was Rancho Bernardo, an upper middle class community in Southern California. A total of 170 postmenopausal women participated, aged 55-80 years. None of them were taking exogenous estrogen between 1972 and 1974. Plasma was obtained for sex hormone and sex hormone-binding globulin (SHBG) assays. Estradiol/SHBG and testosterone/SHBG ratios were used to estimate biologically available hormone levels; bioavailable (non-SHBG-bound) testosterone was measured directly in 60 women. Height loss was based on height measurements taken 16 years apart. Height loss was strongly correlated with age (p = 0.001). These women lost an average 0.22 cm/year in height. Neither estrone nor estradiol levels were significantly and independently related to height loss. Both estimated bioavailable testosterone (testosterone/SHBG ratio) and measured bioavailable testosterone levels predicted future height loss (p = 0.02 and 0.08, respectively) independent of age, obesity, cigarette smoking, alcohol intake, and use of thiazides and estrogen. We conclude that bioavailable testosterone is an independent predictor of height loss in elderly postmenopausal women. The reduced height loss is compatible with a direct effect of testosterone on bone mineral density or bone remodeling.

Premature menopause and low back pain. A population-based study

The association between premature menopause and low back pain was examined among 5325 women surveyed in the second National Health and Nutrition Examination survey. Nearly 49% of the women were postmenopausal. In a multiple logistic regression model that included age, postmenopausal women were approximately twice as likely to report low back pain compared to premenopausal women (odds ratio = 2.1; 95% confidence interval: 1.4-3.0). Among postmenopausal women, significant positive trends in low back pain were observed with decreasing age at menopause (P = 0.005) and increasing years since menopause (P = 0.004). The prevalence odds ratio for women who had their menopause before the age of 30 was 3.2 (1.8-5.4); and for women who had their menopause for 15 or more years the odds ratio was 3.0 (1.7-5.3). These findings suggest that premature menopause is associated with low back pain. Further studies appear warranted to confirm these findings, assess possible explanations, and examine the circumstances in which premature menopause occurs.

Role of trabecular morphology in the etiology of age-related vertebral fractures

Osteoporotic compression fractures of the spine differ from most other age-related fractures in that they usually are associated with minimal trauma and with loads no greater than those encountered during normal activities of daily living. With aging and osteoporosis, there is progressive resorption of bone, resulting in reductions in bone density, thinning of trabeculae, and loss of trabecular contiguity. These changes in trabecular bone structure are associated with losses in bone strength which are disproportionate to the reductions in bone mass alone. To explain this disproportionate loss of bone strength, the prevailing opinion is that density reductions in the vertebral centrum are accompanied by a reduction in the number of trabeculae, by preferential resorption of horizontal trabeculae, and by hypertrophy of the remaining vertical trabeculae. To evaluate this view of vertebral morphology, we performed three-dimensional stereological analysis of trabecular bone extracted from midsagittal sections of first lumbar vertebral bodies from 12 donors spanning an age of 27-81 years. We found that both the number (R2 = 0.63, P < 0.01) and thickness (R2 = 0.91, P < 0.01) of trabeculae decreased linearly with density (as expressed by bone volume fraction) whereas the spacing between the trabeculae (R2 = 0.61, P < 0.01) increased reciprocally. There were more vertical trabeculae with transverse trabeculae at all densities, and the number of vertical trabeculae changed with density at twice the rate of the number of transverse trabeculae (P < 0.001). These data do not support the prevailing view that there is preferential resorption of horizontal trabeculae or hypertrophy of the remaining vertical trabeculae.(ABSTRACT TRUNCATED AT 250 WORDS)

When bone mass fails to predict bone failure

New technology for noninvasive measurement of bone mass has enabled many studies of bone mass and its relationship to fracture, which challenge the view that bone mass is the only relevant factor in the etiology of fractures. Several studies have reported ROC curves that generally show values of about 80%. No convincing evidence suggests that one technique is superior to another. The reported relative risks or odds ratios for a fracture usually range between 1.2 and 2.5 per SD. There is no doubt that the risk of a fracture increases as the bone density decreases. However, even with a low bone mass, the risk of not fracturing a bone over the next year is over 90%. Most of the data suggest that patients with severe vertebral fractures have lower bone mass than those with mild fractures, but some women with similarly low bone mass have mild or no fractures. The weight of the evidence suggests that age has an effect on fracture incidence which is independent of bone mass. Trauma is such a major factor that it is surprising to find almost no studies that have controlled for it. The relationship between bone mass and bone failure is strong, but other factors must also be contributing to the bone failure which, like heart failure or renal failure, is a complex, multifactorial disease.

Determinants of osteoporotic thoracic vertebral fracture. Screening of 57,000 Finnish women and men

A population sample of 27,000 Finnish women and 30,000 men was studied for the presence of a thoracic vertebral fracture. In both sexes, the prevalence of such fractures increased with age: after 40 years of age in the men and after 55 years of age in the women. The interaction of sex and age was significant, and even when the other determinants were adjusted for. In the women aged 35-44, 55-64, and 75 years or more, the prevalence per 1,000 was respectively 2.4, 5.1, and 29, and in the men in the corresponding age groups 5.2, 15, and 28. A previous history of trauma was a fracture determinant in both sexes. In the men, but not in the women, there was an increased risk of fracture when there was a history of tuberculosis and/or peptic ulcer, and in current smokers. Thus, contrary to observations on extremity fractures, the men had an increased risk of sustaining a thoracic vertebral fracture compared with the women. This may reflect differences in the development of osteoporosis in the axial skeleton versus the appendicular skeleton.

Normal bone density in Irish women: is American normative data suitable for use in Ireland?

The objective of the study was to determine whether or not U.S. normal data for female Vertebral Bone Mineral Density is suitable for use in an Irish population. One hundred and fifty-six healthy Caucasian women of permanent Irish domicile had bone densitometry performed using single energy quantitative computed tomography of L2, L3 and L4 vertebrae. We found that comparison of our results to normal American data shows a slight and progressive increase in bone mineral content of postmenopausal American women with age relative to the Irish population. This difference is small and not sufficient to justify development of separate normal values for Irish women. We conclude that this discrepancy may be due to a combination of environmental and racial factors or to the more rigorous exclusion criteria applied in our study.

Assessment of bone mineral density in postmenopausal and senile osteoporosis using quantitative CT

The authors analyzed bone mineral density in 213 patients from January 1988 to September 1989. Bone mineral density of the vertebral body in the osteoporosis group of patients was compared with that in the normal group to investigate the correlation between bone mineral density and age distribution, and to estimate fracture threshold in the osteoporosis group. It was found that men, by linear regression, lose an average of 0.91% of bone per year, and women, by cubic regression, lose an average of 1.14% per year, accelerating at menopause. In the osteoporotic group, bone mineral density of men decreased an average of 29.7% compared with the non-osteoporotic group; that of women decreased an average of 29.9%. There was no difference between sexes. The fracture threshold of the osteoporotic patient was estimated to be about 90 mg/cm3.

Risk of vertebral insufficiency fractures in relation to compressive strength predicted by quantitative computed tomography

Vertebral insufficiency fractures may result from excessive loading of normal and routine loading of osteoporotic spines. Fracture occurs when the mechanical load exceeds the vertebral compressive strength, i.e., the maximum load a vertebra can tolerate. Vertebral compressive strength is determined by trabecular bone density and the size of endplate area. Both parameters can be measured non-invasively by quantitative computed tomography (QCT). In 75 patients compressive strength (i.e., trabecular bone density and endplate area) of the vertebra L3 was determined using QCT. In addition, conventional radiographs of the spines were analysed for the prevalence of insufficiency fractures in each case. By relating fracture prevalence to strength, three fracture risk groups were found: a high-risk group with strength values of L3 less than 3 kN (kilo Newton) and a fracture risk of 100%, an intermediate group with strength values from 3 to 5 kN and a steeply increasing risk with decreasing strength, and a low-risk group with strength values greater than 5 kN and a fracture risk near 0%. Biomechanical measurements and model calculations indicate that spinal loads of 3 to 4 kN at L3/4 will be common in everyday activities. These data and the results described above suggest that spines with strength values of L3 less than 3 kN are at an extremely high risk of insufficiency fractures in daily life. Advantages of fracture risk assessment by strength determination over risk estimation based on clinically used trabecular bone density measurements are discussed.

Sex steroids and osteoporosis: effects of deficiencies and substitutive treatments

Adult mammalian bone is continuously renewed by the process of remodelling. In young healthy adults the amount of bone that is resorbed by osteoclasts is replaced by osteoblasts so that no net loss of bone occurs. In a situation of reduced sex hormone levels, such as in females after menopause or ovariectomy, in males after orchidectomy, or in patients of either sex with gonadal dysfunction, there is an imbalance between bone resorption and bone formation resulting in bone loss. The various hypotheses to explain the aetiology of this imbalance are reviewed. Substitution therapy of females with oestrogen results in the prevention of oestrogen deficiency-induced bone loss. It is generally agreed that the effect is due to inhibition of bone resorption. Recent in vitro data, however, indicate that oestrogens also have the capacity to stimulate the proliferation and functioning of bone-forming cells. Prevention of oestrogen deficiency-induced bone loss can also be achieved by treatment with high doses of progestagens. Available data suggest that this too is caused by resorption inhibition. The aim of treatment of females, who have lost so much bone that there is an increased risk of fractures after minimal trauma, is to increase bone mass rather than to prevent further bone loss. This can be accomplished by treatment with anabolic steroids. Both biochemical and histological data indicate that anabolics stimulate the activity of functioning osteoblasts. The increase in bone mass during continuous treatment is temporary because anabolics most probably also inhibit bone resorption. Substitution therapy with anabolics or androgens in males is equally effective and increases trabecular bone mass in the spine.

Hip fractures in young patients: is this early osteoporosis?

Hip fracture in patients under age 50 is rare, and is often not attributable solely to the energy of injury. Our aim was to determine if trabecular bone mineral density (BMD) is abnormal in young patients with hip fractures. We reviewed all hip fractures treated at our institution between 1979 and 1986 and contacted 20 patients under the age of 50 at the time of injury, all of whom wished to be studied. The mean age at the time of injury was 39 (range 24-47). Subjects were questioned for osteoporosis risk factors, classified by level of energy producing their injury, and then underwent quantitative computed tomography (QCT) bone densitometry of trabecular bone in the lumbar spine. Bone mineral density by QCT was below the mean for age in 90% of the patients, and was greater than 1 SD below the mean in 75%. Mean percentage BMD decrease from age-matched controls was 34% (P less than 0.005) in women and 19% (P less than 0.005) in men. There was an inverse correlation in the degree of BMD decrease and the energy level of injury. There was a direct correlation of the severity of BMD decrease and the cumulative number of osteoporosis risk factors. This investigation has found that 1-7 years following hip fracture, otherwise presumedly healthy young patients demonstrate a statistically significant decrease in spinal BMD from age/sex-matched controls. These data do not determine if osteopenia is the cause or the result of injury, nor do we wish to infer that measurement of bone density at one site can predict future fractures at other sites.(ABSTRACT TRUNCATED AT 250 WORDS)

Bone mineral density and fracture in postmenopausal women

This retrospective study examined bone mineral density (BMD) for discrimination of female patients with fractures. Bone densitometry was done in 146 patients over the age of 50 years at radius, lumbar spine, and proximal femur sites using single and dual photon absorptiometry. The patients were divided into three groups: (A) no osteoporotic fractures (n = 92); (B) mild spine fractures with greater than 15% compression (n = 38); and (C) hip fractures (n = 16). Groups B and C did not differ significantly from each other in BMD, but these groups differed significantly from group A for spine and femur BMD. No significant differences between groups were found for the radius. Receiver operating characteristic (ROC) analysis showed that the BMD of the proximal femur had the highest diagnostic sensitivity for both spine and femur fractures; the radius had the lowest overall sensitivity, and the spine was intermediate.

Quantitative computed tomography reflects vertebral fracture morbidity in osteopenic patients

We studied the relationship between spontaneous vertebral compression fractures and lumbar vertebral trabecular bone density in 69 consecutive patients with suspected osteopenia. Seven had biopsy-confirmed osteomalacia. The remaining 62 were divided into three groups: group 1--asymptomatic patients suspected of having osteopenia on plain films, but with no vertebral compression fractures (N = 24); group II--those with one to five vertebral compression fractures (N = 16); and group III--those with six or more vertebral compression fractures (N = 22). A quantitative computed tomographic (QCT) scan of the lumbar spine was performed on all patients. Patients in group I had QCT values of 94 +/- 23 mg/cm3 (mean +/- SE); those in group II had QCT values of 66 +/- 28 mg/cm3; and those in group III had values of 34 +/- 28 mg/cm3. There were significant differences among all groups (P less than .001), although there was considerable overlap of individuals among the groups. There was no significant difference between the mean QCT value of patients with one compression fracture and the value of those with between two and five compression fractures. Patients with biopsy-proven osteomalacia had higher vertebral trabecular bone density than patients with osteoporosis and compression fractures. Our study provides evidence suggesting a strong inverse relationship between QCT-measured vertebral bone density and the presence of vertebral compression fractures in a group of osteopenic patients.

Prediction of vertebral strength by dual photon absorptiometry and quantitative computed tomography

We measured the lumbar bone mineral of 19 cadavers (10 women, 9 men) by dual photon absorptiometry (DPA) and quantitative computed tomography (QCT). In addition, we determined the ultimate load and stress of each vertebra, and finally ash content and volumetric ash density of the vertebral body. We found that single energy QCT was inferior to DPA and dual energy QCT in the prediction of the ultimate load or stress of vertebrae (P less than 0.001). The ultimate stress was best predicted by using the dual energy QCT results (r = 0.71; SEE = 36.3 N/cm2) whereas the ultimate vertebral load was best predicted by using the DPA (BMC) results (r = 0.80; SEE = 740 N). If the QCT finding was multiplied with the surface area of the vertebral body it could be used to predict the ultimate load with good accuracy (r = 0.74; SEE = 841 N). All the above correlations were higher in women than in men. The frequency of vertebral compression fractures in the material was well correlated with the bone mineral findings. A nonlinear (third degree) relationship between mineral content and mechanical characteristics is proposed but within the area of measurement used in clinical practice a linear (first degree) equation is preferred.

Determinants of peak trabecular bone density in women: the role of androgens, estrogen, and exercise

To elucidate determinants of peak trabecular bone density, we studied the role of androgens, estrogen, and aerobic exercise in 30 women from 18 to 22 years old. The women were divided into three groups: Sedentary, 11 normal women who did not exercise regularly; eumenorrheic, 10 athletes with normal menstrual function; and oligomenorrheic, 9 athletes with exercise-induced oligomenorrhea. All athletes participated in aerobic sports that did not involve selective resistance loading of the back. Serum free and albumin-bound testosterone (fab T), androstenedione (A), and estradiol (E2) were measured on four separate occasions at consecutive 7 day intervals and averaged. Trabecular density was measured by quantitative computed tomography of the lumbar spine. Peak trabecular bone density was related to fab T (r = 0.48, p = 0.007), A (r = 0.40, p = 0.03), and E2 (r = 0.40, p = 0.04). When taken in combination, androgens and estrogen each accounted independently for significant portions of the variance in bone density [fab T and E2 (R2 = 0.38, p = 0.002) and A and E2 (R2 = 0.27, p = 0.01)]. Bone density (mg/ml, mean +/- standard error of the mean, SEM) in the sedentary group (174 +/- 6) was not significantly different from that in the eumenorrheic (183 +/- 12, p = 0.47) or oligomenorrheic (161 +/- 11, p = 0.32) subjects. We conclude that androgens and estrogen function as independent and additive determinants of peak trabecular bone density in young women. The quantitative impact of aerobic exercise (without resistance loading) and exercise-induced menstrual dysfunction appears to be less important than that of the hormones.

Early vertebral trabecular bone loss in normal premenopausal women

The precise timing for the onset of trabecular bone loss in women is a matter of controversy. To address this issue, we studied the relationship between age and vertebral trabecular bone density (measured by computed tomography) in 74 healthy premenopausal women from 18 to 48 years old. We also measured radial cortical bone density (by single photon absorptiometry) in 28 of these subjects. Trabecular bone density levels (milligrams per milliliter, mean +/- standard error of the mean, SEM) were significantly (p less than 0.05) higher in the second (178 +/- 8) and third (171 +/- 6) decades than in the fourth (158 +/- 4) or fifth (140 +/- 12) decades, and were inversely correlated with age (r = -0.39, p = 0.0006), diminishing at a rate of 1.3 mg/ml (0.73%) per year. Radial cortical bone density levels (grams per square centimeter) were similar in the third (0.711 +/- 0.021), fourth (0.721 +/- 0.012), and fifth (0.736 +/- 0.012) decades and were not related to age (r = 0.17, p = 0.39). We conclude that vertebral trabecular bone loss in women commences during or prior to the third decade. In contrast, radial cortical bone density does not decline during the premenopausal years.

Effect of declining renal function on bone density in aging women

The factors that are responsible for trabecular bone loss in aging women are not completely understood. To evaluate declining renal function as a possible factor, we studied 19 Caucasian women (average age 67) who were from 6 to 41 years postmenopausal. Trabecular bone density was quantitated by computerized tomography of the spine. Serum calcium, phosphorus, and creatinine were normal in all subjects. Creatinine clearance averaged 74 ml/min (range 38-122), decreased with age (r = -0.60, P = 0.003), and was inversely related to serum creatinine (r = -0.51, P = 0.01). Bivariate regression demonstrated that bone density decreased with age (r = -0.59, P = 0.004); controlling for the effect of creatinine clearance weakened this correlation to r = -0.45 (P = 0.03); controlling additionally for 1,25-dihydroxyvitamin D [1,25(OH)2D] and parathyroid hormone (PTH) reduced the correlation coefficient to r = -0.34 (P = 0.11). Bone density also decreased in direct proportion to the decrement in creatinine clearance (r = 0.44, P = 0.03); controlling for the effects of 1,25(OH)2D and PTH reduced this correlation coefficient to r = 0.34 (P = 0.11). These results suggest that occult renal insufficiency may contribute to bone loss in aging women, and that this effect may be mediated in part by 1,25(OH)2D and PTH. In this age group renal function should be assessed by measuring creatinine clearance rather than the serum creatinine concentration since renal insufficiency can be masked by apparently normal circulating creatinine levels.

Prediction of the compressive strength of vertebral bodies of the lumbar spine by quantitative computed tomography

The ultimate compressive strength of 36 thoracolumbar vertebrae was determined experimentally. In addition, the trabecular bone mineral content was measured by single energy quantitative computed tomography. The areas of fractured endplates were also determined by computed tomography. The results show that a linear relationship exists between the compressive strength and the product of bone density and endplate area. These data allow an in vivo prediction of vertebral body strength using a noninvasive method with a standard error of estimate amounting to less than 0.95 kN.

Determinants of atraumatic vertebral fracture rates in menopausal women: biologic v mechanical factors

In menopausal women, the susceptibility to atraumatic vertebral fractures is thought to be governed by both mechanical factors (as represented by bone density) and by biologic factors such as age, body size, and dietary calcium. Whether these biologic factors independently influence fracture rates beyond the effect of bone density is a matter of controversy. To compare the relative importance of mechanical and biologic factors on vertebral fractures, we elucidated the determinants of atraumatic compression fractures in 63 menopausal women who had no chronic diseases other than osteopenia. Trabecular bone density was determined by quantitative computerized tomography of the spine. Fracture frequency was expressed as the number of compressed vertebrae per person between T5 and L4. The analysis showed that fracture frequency, bone density, and the biologic factors were closely interrelated. Fracture frequency was inversely correlated to bone density [R2 (spline model) = .40, P less than .0001], body size (r = -.26, P = .05), and dietary calcium (r = -.28, P = .04), and directly correlated with age (r = .46, P = .0002). Bone density decreased with age (r = -.65, P less than .0001), increased with body size (r = .37, P = .004), and tended to increase with dietary calcium (r = .24, P = .08). After controlling for bone density, there was no perceptible residual relationship between fracture frequency and any of these biologic factors. We conclude that mechanical factors overshadow age, body size, and dietary calcium as determinants of vertebral fracture frequency. The apparent influence of these biologic factors on fracture frequency is explained by their surrogate effects on bone density.

Adrenal androgens, sex-hormone binding globulin and bone density in osteoporotic menopausal women: is there a relationship?

The relationships among sex steroids, sex hormone binding globulin (SHBG) and vertebral bone density as measured by computerized tomography were studied in 18 post-menopausal women. A significant negative correlation was found between SHBG binding capacity (SHBG-BC) and bone density. Bone density and the adrenal androgen dehydroepiandrosterone sulfate (DHEAS) declined with age, and SHBG-BC was correlated significantly with DHEAS concentrations. The relationship between SHBG-BC and bone density may be affected by adrenal androgen output.