Improving femoral bone density measurements

Bilateral hip DXA Reporting: 2023 Official Positions of the International Society for Clinical Densitometry

INTRODUCTION

This position development conference (PDC) Task Force examined the use and reporting of bilateral hip bone mineral density (BMD) measurements. This was deemed appropriate as increased availability of Dual-energy X-ray Absorptiometry (DXA) technology offering bilateral hip measurement resulted in more routine clinical use. The International Society for Clinical Densitometry Official Positions accept bilateral hip BMD measurement for clinical use but currently do not include recommendations for reporting those studies.

METHODS

Four key questions regarding bilateral hip reporting were proposed by the PDC Steering Committee. Relevant literature was identified using PubMed. Questions included whether bilateral hip measurements are appropriate for diagnostic classification or monitoring, as well as which bilateral hip regions of interest should be reported for diagnosis and monitoring. Additionally, the appropriate nomenclature for bilateral hip acquisition was defined.

RESULTS

The literature review demonstrated that bilateral hip measurement is appropriate and diagnostic classification should be based on the lowest T-score at the right or left side femoral neck or total hip; the mean T-score should not be used for diagnostic purposes. Mean bilateral total hip is preferred for BMD monitoring. The terms hip, or total hip were deemed appropriate nomenclature instead of femur or total proximal femur.

CONCLUSION

Bilateral hip acquisition is clinically appropriate and reporting and nomenclature standards are offered herein when a bilateral hip study is acquired. In terms of future research, the impact of discordant hips on diagnosis and monitoring was identified as a significant knowledge gap.

Non-BMD DXA measurements of the hip

Hip fracture is one of the most serious complications of osteoporosis. More than 50% of hip and other fractures occur in patients without densitometric osteoporosis. Therefore, areal bone mineral density (aBMD) may not be the best way to assess fracture risk. In order to improve assessment of fracture risk, many other approaches have been taken. At the present time, the Fracture Risk Algorithm (FRAX©) is one of the most notable ways to improve assessment of fracture risk. However, since early in the initiation of the dual energy x-ray absorptiometry (DXA) era, several non-BMD DXA approaches to the assessment of hip fracture risk have been proposed. This review will cover some of those methodologies, including hip-axis length (HAL), hip-structural analysis (HSA), finite element analysis (FEA) by DXA, and body composition of the thigh by DXA (BCT). These methods have been utilized in models of hip fracture occurrence and in pharmacological clinical trials. How they should be used in clinical practice or if they should be used in clinical practice is more of an issue. In addition, we will discuss the recent proposal of the use of Long Femur Scan Field in the effort to diagnose atypical femoral fractures.

Study of the variations of fall induced hip fracture risk between right and left femurs using CT-based FEA

Background

Hip fracture of elderly people—suffering from osteoporosis—is a severe public health concern, which can be reduced by providing a prior assessment of hip fracture risk. Image-based finite element analysis (FEA) has been considered an effective computational tool to assess the hip fracture risk. Considering the femoral neck region is the weakest, fracture risk indicators (FRI) are evaluated for both single-legged stance and sideways fall configurations and are compared between left and right femurs of each subject. Quantitative Computed Tomography (QCT) scan datasets of thirty anonymous patients’ left and right femora have been considered for the FE models, which have been simulated with an equal magnitude of load applied to the aforementioned configurations. The requirement of bilateral hip assessment in predicting the fracture risk has been explored in this study.

Results

Comparing the sideways fall and single-legged stance, the FRI varies by 64 to 74% at the superior aspects and by 14 to 19% at the inferior surfaces of both the femora. The results of this in vivo analysis clearly substantiate that the fracture is expected to initiate at the superior surface of femoral neck region if a patient falls from his/her standing height. The distributions of FRI between the femurs vary considerably, and the variability is significant at the superior aspects. The p value (= 0.02) obtained from paired sample t-Test yields p value ≤ 0.05, which shows the evidence of variability of the FRI distribution between left and right femurs. Moreover, the comparison of FRIs between the left and right femur of men and women shows that women are more susceptible to hip fracture than men.

Conclusions

The results and statistical variation clearly signify a need for bilateral hip scanning in predicting hip fracture risk, which is clinically conducted, at present, based on one hip chosen randomly and may lead to inaccurate fracture prediction. This study, although preliminary, may play a crucial role in assessing the hip fractures of the geriatric population and thereby, reducing the cost of treatment by taking predictive measure.

The effect of age on the changes in bone mineral density and osteoporosis detection rates in Han Chinese men over the age of 50

OBJECTIVE

To examine the relationship between age and BMD at different skeletal sites and osteoporosis (OP) detection rates in Han Chinese men over 50 years and to assess the diagnostic value of the OSTA.

METHODS

A retrospective analysis of 1488 men over 50 was carried out and group comparisons were made.

RESULTS

BMDs at total hip and femoral neck decreased with age (p < 0.01) and were negatively correlated with age by liner correlation analysis (r = -0.36, -0.30; p all <0.05). The detection rates of OP and osteopenia were 10.08% and 43.21% respectively, which increased with age, and significantly higher among over 70 years old than under 70 individuals (47.75% versus 35.56%; 14.88% versus 1.99%; p all <0.01). The detection rate at the femoral neck was similar to the overall detection rate. Sensitivities of OSTA index at a cutoff value of -1 and -4 were 87.33% and 52.0% respectively, and the specificities were 56.20% and 87.59%.

CONCLUSION

BMDs at femoral neck and total hip decrease with age. Detection rates of OP increase with age. Bilateral femoral neck BMD measurement can improve detection rates of OP. OSTA is a useful screening tool for OP in Han Chinese men over 50 years.

Bone density, body composition, and markers of bone remodeling in type 1 diabetic patients

OBJECTIVE

To assess bone mineral density (BMD), body composition by dual X-ray absorptiometry (DXA), and various biochemical markers of bone growth and resorption in a group of children with type 1 diabetes mellitus (T1DM).

PATIENTS AND METHODS

The study included 47 patients with T1DM and 30 age- and sex-matched controls. Anthropometric measurements, biochemical markers for bone formation, bone resorption and DXA were done for all patients and controls.

RESULTS

Of our diabetes patients, seven (16.7 %), three (7.3 %), and 17 (41.5%) met diagnostic criteria for osteopenia at the right femur, lumbar spine and total body, respectively. On the other hand, osteoporosis as defined by the WHO criteria was diagnosed in 21 patients (51.2%) at the total body by DXA. Lean body mass and lean fat ratio were lower, while, total fat mass, abdominal fat%, soft tissue fat mass%, and fat/lean ratio were higher in diabetics compared to controls. Also, our patients showed lower serum osteocalcin, osteoprotegerin, procollagen type 1, and higher urinary deoxypyridinoline. Pubertal (diabetics and controls) have higher BMD and BMC than prepubertal.

CONCLUSION

Diabetic patients had a low BMD after adjustment (Z score), low bone formation and high bone resorption markers. Diabetes control and increase in BMI leads to a decrease in the incidence of low bone mineral density. Diabetes causes an increase in body fat especially abdominal fat which leads to an increase in insulin resistance and decrease in lean mass.

What happens to femoral neck bone mineral density after hip resurfacing surgery?

The major advantage of hip resurfacing is the decreased amount of bone resection compared with a standard total hip replacement. Fracture of the femoral neck is the most common early complication and poor bone quality is a major risk factor. We undertook a prospective consecutive case control study examining the effect of bone mineral density changes in patients undergoing hip resurfacing surgery. A total of 423 patients were recruited with a mean age of 54 years (24 to 87). Recruitment for this study was dependent on pre-operative bilateral femoral bone mineral density results not being osteoporotic. The operated and non-operated hips were assessed. Bone mineral density studies were repeated over a two-year period. The results showed no significant deterioration in the bone mineral density in the superolateral region in the femoral neck, during that period.

These findings were in the presence of a markedly increased level of physical activity, as measured by the short-form 36 health survey physical function score.

Effect of the bilateral hip bone density measurement on clinical practice in elderly subjects

OBJECTIVES

The aim of this study was to determine whether the addition of the measurement of bilateral hip bone mineral density (BMD) has an impact on indications for osteoporosis (OP) treatment in community-dwelling elderly individuals, based on criteria from the National Osteoporosis Foundation (NOF).

METHODS

In total, 605 consecutive community-dwelling elderly individuals who were 65 years and older were evaluated. Dual energy X-ray absorptiometry was used to determine the lowest T-score in the lumbar spine+unilateral hip, the bilateral hips, and the lumbar spine+bilateral hips. Risk factors associated with the lowest T-score in these three conditions were applied to indicate treatment in accordance with NOF criteria. McNemar's test was used to assess the difference of adding bilateral hip BMD measurements.

RESULTS

There was a significant difference in the frequency of pharmacological indication using NOF criteria together with the lowest T-score for the three tests (72.8% for lumbar spine+bilateral hips and 71.2% for lumbar spine+unilateral hip; p=0.002). A higher frequency of treatment indication was also observed for lumbar spine+unilateral hip (71.2%) compared to bilateral hips (61.1%) (p<0.001). The discrepancies in treatment appeared to be more evident in women when analyzed by gender distribution.

CONCLUSION

Our finding supports the theory that evaluation of the bilateral hips with the lumbar spine seems to be more sensitive measure for identifying patients with an osteoporosis treatment indication. Furthermore, despite the well-known artifact in the lumbar spine, this site should not be excluded when determining the indication for OP treatment in elderly people.

Bilateral femoral bone mineral density measurements in Chinese women and men

The aim of this study was to assess the contralateral femoral bone mineral density (BMD) difference as measured by dual-energy X-ray absorptiometry (DXA) in mainland Chinese women and men. We measured bilateral proximal femora (i.e., total hip, femoral neck, upper femoral neck, and trochanter) using DXA in 1101 subjects (284 males, 817 females), among whom 504 were postmenopausal. Data were analyzed by descriptive statistics, Student's t-tests, and Pearson's correlation coefficients (r). With bilateral femur measurements and the acquisition of the mean BMD, precision error could be significantly reduced at the total hip, the femoral neck, and the upper femoral neck. Contralateral femoral BMD was highly correlated at all measuring sites (r=0.879-0.964). For the male group and for the postmenopausal subgroup, no significant differences in contralateral femoral BMDs were found. In the postmenopausal women, the percentage of subjects with discordance in classification (i.e., normal, osteopenia, and osteoporosis) for the left and right femora declined from 16.9% to 8.1% with precision adjustment. From a population perspective, since there may still be a considerable number of misdiagnosed cases, we therefore suggest that bilateral femur measurements may be justified for postmenopausal Chinese women.

Bone mineral density and hip structural analysis in type 1 diabetic men

OBJECTIVE

The risk of non-vertebral fractures is increased in men with type 1 diabetes (DM1) but studies have shown only moderately decreased or normal bone mineral density (BMD) in these patients. No previous studies have evaluated hip strength and geometry indices in DM1 patients. This study was therefore designed to characterize associations between BMD, dual X-ray absorptiometry (DXA)-based hip strength indices, metabolic control, and DM1chronic complications.

DESIGN AND METHODS

The study was performed on 36 males aged 43.6 +/- 5.1 years with long-lasting DM1 and 36 healthy males matched for age, weight, and height. BMD in lumbar spine, total hip, upper and lower part of the femoral neck, hip axis length, cross-sectional area and moment of inertia (CSMI), and glycated hemoglobin (HbA1c) were measured.

RESULTS

DM1 men had decreased spine BMD (P < 0.05) and normal total hip BMD in comparison with controls. Hip geometry and strength indices were comparable in both groups. However, M1 men had decreased CSMI and upper femur BMD but these differences did not reach statistical significance (P = 0.06). BMD changes and hip strength parameters did not correlate with HbA1c.

CONCLUSIONS

Middle-aged DM1 men have decreased lumbar spine BMD, normal hip BMD and normal hip strength indices. These changes are not influenced by metabolic control and presence of chronic microvascular complications.

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.

Comparison of BMD precision for Prodigy and Delphi spine and femur scans

INTRODUCTION

Precision error in bone mineral density (BMD) measurement can be affected by patient positioning, variations in scan analysis, automation of software, and both short- and long-term fluctuations of the densitometry equipment. Minimization and characterization of these errors is essential for reliable assessment of BMD change over time.

METHODS

We compared the short-term precision error of two dual-energy X-ray absorptiometry (DXA) devices: the Lunar Prodigy (GE Healthcare) and the Delphi (Hologic). Both are fan-beam DXA devices predominantly used to measure BMD of the spine and proximal femur. In this study, 87 women (mean age 61.6+/-8.9 years) were measured in duplicate, with repositioning, on both systems, at one of three clinical centers. The technologists were International Society for Clinical Densitometry (ISCD) certified and followed manufacturer-recommended procedures. All scans were acquired using 30-s scan modes. Precision error was calculated as the root-mean-square standard deviation (RMS-SD) and coefficient of variation (RMS-%CV) for the repeated measurements. Right and left femora were evaluated individually and as a combined dual femur precision. Precision error of Prodigy and Delphi measurements at each measurement region was compared using an F test to determine significance of any observed differences.

RESULTS

While precision errors for both systems were low, Prodigy precision errors were significantly lower than Delphi at L1-L4 spine (1.0% vs 1.2%), total femur (0.9% vs 1.3%), femoral neck (1.5% vs 1.9%), and dual total femur (0.6% vs 0.9%). Dual femur modes decreased precision errors by approximately 25% compared with single femur results.

CONCLUSIONS

This study suggests that short-term BMD precision errors are skeletal-site and manufacturer specific. In clinical practice, precision should be considered when determining: (a) the minimum time interval between baseline and follow-up scans and (b) whether a statistically significant change in the patient's BMD has occurred.

Cross-calibration and minimum precision standards for dual-energy X-ray absorptiometry: the 2005 ISCD Official Positions

The International Society for Clinical Densitometry (ISCD) Committee on Standards of Bone Measurement (CSBM) consists of experts in technical aspects of bone densitometry. The CSBM recently reviewed the scientific literature on cross-calibration and precision assessment. A report with recommendations was presented at the 2005 ISCD Position Development Conference (PDC). Based on a thorough review of the data by the ISCD Expert Panel during the conference, the ISCD adopted Official Positions with respect to (1) cross-calibration when changing or replacing hardware; (2) the approach to cross-calibration when an entire system is changed to one made by either the same or a different manufacturer; (3) when no cross-calibration study or bone mineral density (BMD) comparison is done between facilities; and (4) the minimum acceptable precision for an individual technologist. We present here the ISCD Official Positions on these topics that were established as a result of the 2005 PDC, together with the associated rationales and supportive evidence.

Effect of subtle positioning flaws on measured bone mineral density of the hip

Careful hip positioning is necessary for accurate and precise measurement of bone mineral density (BMD) by dualenergy X-ray absorptiometry (DXA). Large, intentional rotational deviations from best hip position reportedly increase measured BMD at the femoral neck. The aim of this study is to determine the effect of unintentional, subtle deviations from best hip position ("flaws") on expected and measured BMD of the hip and its subregions. Two hundred DXA scans (GE/Lunar Prodigy) performed in the dual-femur mode were randomly selected and scrutinized for hip-positioning flaws. Hips were sorted by side (right/left), positioning quality (flawless/flawed), and specific positioning flaw (under/over-rotation and adduction/abduction). Individual hip pairs in which at least one hip was flawlessly positioned were further sorted as flawless/flawless, flawless/vertically flawed, flawless/rotationally flaw, and flawless/dually flawed. Differences and direction of difference in BMD between sorted groups and within individual hip pairs were analyzed by univariate analysis (t-test for equal samples). Two hundred hip pairs (400 individual hip scans) were analyzed. Overall, there was no significant difference in BMD between all right and all left hips or between all flawlessly positioned and all flawed hips. In hip pairs in which one hip was flawlessly positioned and the contralateral hip position was flawed (vertically, rotationally, or both), the measured BMD of the latter hip was not predictably greater than the former. Average absolute intrapair BMD difference between hip subregions was 0.038+/-0.001 g/cm2 and was unaffected by the presence or type of positioning flaw. Net intrapair difference between sorted hip groups and within hip pairs was negligible, indicating that the direction of the variance was equally positive and negative. In the practice of clinical densitometry, subtle positioning flaws do not generate predictable changes in measured BMD at any hip region of interest. The current teaching that rotational deviations from best hip position results in a greater measured BMD needs to be reconsidered when comparing a rotationally flawed hip with a contralateral flawlessly positioned hip.