A. Stewart

Broadband ultrasound attenuation and dual energy X-ray absorptiometry in patients with hip fractures: Which technique discriminates fracture risk

There is considerable interest in predicting risk of hip fracture in order to allow targeting of preventive care. This study aimed to determine which of two methods best discriminates a hip fracture population from controls. Fifty women with fractured neck of femur, and 50 control subjects were scanned using dual energy X-ray absorptiometry (DXA) of the spine and hip and broadband ultrasound attenuation (BUA) of the os calcis. Significant differences between the two populations could be found for both DXA and BUA, with BUA showing the largest percentage difference (27%). The mean z-scores showed that BUA had the lowest, with the exception of DXA trochanter. However, no significant difference between BUA and DXA trochanter Z-scores was found. A receiver operator characteristic (ROC) analysis showed that BUA has a superior sensitivity and specificity compared with DXA measurements, with DXA of the hip being better than the spine. This retrospective study shows that BUA is a better discriminator of hip fracture than DXA lumbar spine of DXA hip, which may have important implications for predicting those at risk of future hip fracture.

A method for assessment of the shape of the proximal femur and its relationship to osteoporotic hip fracture

The shape of the proximal femur has been demonstrated to be important in the occurrence of fractures of the femoral neck. Unfortunately, multiple geometric measurements frequently used to describe this shape are highly correlated. A new method, active shape modeling (ASM) has been developed to quantify the morphology of the femur. This describes the shape in terms of orthogonal modes of variation that, consequently, are all independent. To test this method, digitized standard pelvic radiographs were obtained from 26 women who had suffered a hip fracture and compared with images from 24 age-matched controls with no fracture. All subjects also had their bone mineral density (BMD) measured at five sites using dual-energy X-ray absorptiometry. An ASM was developed and principal components analysis used to identify the modes which best described the shape. Discriminant analysis was used to determine which variable, or combination of variables, was best able to discriminate between the groups. ASM alone correctly identified 74% of the individuals and placed them in the appropriate group. Only one of the BMD values (Ward’s triangle) achieved a higher value (82%). A combination of Ward’s triangle BMD and ASM improved the accuracy to 90%. Geometric variables used in this study were weaker, correctly classifying less than 60% of the study group. Logistic regression showed that after adjustment for age, body mass index, and BMD, the ASM data was still independently associated with hip fracture (odds ratio (OR)=1.83, 95% confidence interval 1.08 to 3.11). The odds ratio was calculated relative to a 10% increase in the probability of belonging to the fracture group. Though these initial results were obtained from a limited data set, this study shows that ASM may be a powerful method to help identify individuals at risk of a hip fracture in the future.

Prediction of fractures in perimenopausal women: a comparison of dual energy x ray absorptiometry and broadband ultrasound attenuation.

OBJECTIVE: To consider whether bone mineral density (BMD) measurements can predict traumatic fractures occurring in perimenopausal women. METHODS: One thousand perimenopausal women called up for screening underwent both dual energy x ray absorptiometry (DXA) of the spine and hip, and broadband ultrasound attenuation (BUA) of the heel. Two years later, they were sent a questionnaire to discover those who had since had a fracture, and compare them with those who had not. RESULTS: About 2% of the women had sustained a fracture in the two years since attendance for screening. Fractures in this age group can be predicted weakly, but significantly, by bone mass measurements using DXA and BUA (odds ratios from 1.4 to 2.1). The lumbar spine appeared to be one of the best predictive sites (odds ratio for 1 SD reduction in BMD 2.1 (95% confidence interval 1.2 to 3.8)), but no significant differences were found between the areas under the curve in receiver operator characteristic (ROC) analysis. CONCLUSION: In this preliminary study it appeared that bone mass measurements are predictive of perimenopausal traumatic fractures in addition to postmenopausal fractures related to osteoporosis. DXA of the lumbar spine did not perform significantly better than BUA. The number of fractures occurring was low, however, and further long term follow up is required to confirm the finding.

Association between vitamin D receptor gene polymorphisms, falls, balance and muscle power: results from two independent studies (APOSS and OPUS)

SummaryFall prevention is a key strategy for reducing osteoporotic fractures. We investigated the association between vitamin D receptor (VDR) polymorphisms and reported falls in postmenopausal women. Bsm1 polymorphisms were associated with falls, balance and muscle power measurements. These results may explain some of the excess fracture risk associated with VDR in some studies.IntroductionFall prevention is a key strategy for reducing osteoporotic fractures. It has been suggested that vitamin D supplementation may reduce the incidence of falls by reducing body sway and increasing muscle power. The vitamin D receptor gene is a well-studied candidate gene for osteoporosis. We investigated the association between VDR polymorphisms and reported falls in postmenopausal women.MethodsFalls data were collected in two separate population cohorts. Five polymorphisms of the VDR gene were analysed (Cdx-2, Fok-1, BsmI, Taq1 and Apa1) in the Aberdeen Prospective Osteoporosis Screening Study (APOSS) cohort. Results found in APOSS were then validated in an independent cohort—the Osteoporosis and Ultrasound (OPUS) study (Bsm1 and Fok1 only), where muscle power and balance were also measured.ResultsCarriers of the ‘B’ allele (Bsm1) showed an increased risk for falls. In APOSS, this was statistically significant for visit 3 multiple falls (p = 0.047) and for recurrent falls (p = 0.043). Similar results were found in OPUS for visit 1 falls (p = 0.025) and visit 1 multiple falls (p = 0.015). Bsm1 polymorphisms were also associated with balance and muscle power measurements.ConclusionsIn conclusion, these results demonstrate an association between the Bsm1 polymorphism and risk of falling that may explain some of the excess fracture risk associated with VDR in some studies.

Screening Elderly Women for Risk of Future Fractures—Participation Rates and Impact on Incidence of Falls and Fractures

We have assessed the acceptability of a method for screening for risk of future hip fracture in elderly women. After receipt of an initial response to a mailed risk-factor questionnaire sent out to 5,306 women, women were randomly assigned to active or control groups. The active group was invited to participate in a screening visit that comprised a life-style questionnaire and a quantitative ultrasound heel scan. General practitioners (GPs) of women who were found to be in the lowest quartile of broadband ultrasound attenuation and/or who had two or more risk factors for hip fracture were advised to prescribe a calcium and vitamin D supplement. A second mailed questionnaire was sent to both groups 1 to 3 years later. Compared with the control group, the active group had a 56% lower risk of fracture (odds ratio [OR], 0.44; 95% confidence interval [CI], 0.24–0.81 adjusted age, weight, and treatment status). At follow-up, the proportion of fallers in the active group (25.3%) was lower than that in the control group (29.6%) (P = 0.064). The control group was found to have a higher rate of falls at follow-up than the active group (95% CI, 0.02–0.22); no difference was found at baseline (95% CI, −0.08 to +0.14). The screening method used was found to be acceptable to the majority of elderly women in this study. Screening the elderly in this way together with simple advice on treatment appears to reduce the age-associated increase in fall rates and the number of subsequent fractures. This form of screening may provide a cost-effective method to reduce falls and fractures in free-living elderly women. However, no such cost-effectiveness analysis has been performed to date.