Comparative Assessment of Bone Mineral Measurements Using Dual X-ray Absorptiometry and Peripheral Quantitative Computed Tomography

A measurement of bone mass is the single most important determinant of future fracture. However, controversy exists as to which technique (dual X-ray absorptiometry (DXA) or peripheral quanitative computed tomography (pQCT)), and which site of skeletal measurement (axial vs appendicular) provides the best prediction of fracture risk. The aims of this study were: (1) to determine the ability of pQCT to predict bone mass of the lumbar spine, proximal femur, and distal forearm measured using DXA, and (2) to compare the ability of DXA and pQCT to discriminate prevalent fractures in women with established osteoporosis. One hundred and sixty-five women were studied, including 47 with established osteoporosis (vertebral, hip or Colles' fractures) as well as 118 who had bone mass measurements to assess osteoporosis risk. Each subject had bone mass measured by DXA at the lumbar spine and femoral neck, and at the distal radius by both DXA and pQCT. In women with fractures, bone mass, when expressed as a standardized score, was in general lower using DXA compared with the appendicular skeleton measured using pQCT. Bone mass determinations at all sites were significantly correlated with each other. The highest correlation coefficients were observed within the axial skeleton. In women with fractures, the highest odds ratios were observed at skeletal regions measured using DXA. Likewise, the areas under the receiver-operating characteristic (ROC) curves were comparable at all skeletal regions measured using DXA; and were significantly greater than the areas under the ROC curves for pQCT measurements. In summary, the strongest discriminators of prevalent fractures were measurements using DXA. Measurements of bone mass at the appendicular skeleton, using either DXA or pQCT, were poorly associated with axial bone mass. PQCT has the poorer ability to discriminate persons with fractures, and appears to be less sensitive than measurements using DXA. Received: 15 September 1997 / Accepted: 17 February 1998     

Structural Parameters of the Proximal Femur by 3-Dimensional Dual-Energy X-ray Absorptiometry Software: Comparison With Quantitative Computed Tomography

Structural parameters of the proximal femur evaluate the strength of the bone and its susceptibility to fracture. These parameters are computed from dual-energy X-ray absorptiometry (DXA) or from quantitative computed tomography (QCT). The 3-dimensional (3D)-DXA software solution provides 3D models of the proximal femur shape and bone density from anteroposterior DXA scans. In this paper, we present and evaluate a new approach to compute structural parameters using 3D-DXA software. A cohort of 60 study subjects (60.9?±?14.7?yr) with DXA and QCT examinations was collected. 3D femoral models obtained by QCT and 3D-DXA software were aligned using rigid registration techniques for comparison purposes. Geometric, cross-sectional, and volumetric structural parameters were computed at the narrow neck, intertrochanteric, and lower shaft regions for both QCT and 3D-DXA models. The accuracy of 3D-DXA structural parameters was evaluated in comparison with QCT. Correlation coefficients (r) between geometric parameters computed by QCT and 3D-DXA software were 0.86 for the femoral neck axis length and 0.71 for the femoral neck shaft angle. Correlation coefficients ranged from 0.86 to 0.96 for the cross-sectional parameters and from 0.84 to 0.97 for the volumetric structural parameters. Our study demonstrated that accurate estimates of structural parameters for the femur can be obtained from 3D-DXA models. This provides clinicians with 3D indexes related to the femoral strength from routine anteroposterior DXA scans, which could potentially improve osteoporosis management and fracture prevention.     

Analysis of Trabecular Bone Structure with Multidetector Spiral Computed Tomography in a Simulated Soft-Tissue Environment

We investigated the influence of soft tissue (ST) on image quality by high-resolution multidetector computed tomography (MDCT) scans and assessed the effect of surrounding ST on the quantification of trabecular bone structure. Eight bone cores obtained from human proximal femoral heads discarded during hip replacement surgery were scanned with micro-computed tomography (μCT) as well as with MDCT both without (w/o) and with (w) simulated surrounding ST, where a phantom imitated a human torso. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured in all scans. Apparent trabecular bone structure parameters were calculated and compared to similar parameters obtained in coregistered sections of the μCT scans. Residual errors were calculated as root-mean-square (RMS) errors relative to the μCT measurements. Compared to μCT results, trabecular structure parameters were overestimated by MDCT both w and w/o ST. SNR and CNR were significantly higher in the scans w/o ST. Significant correlations between μCT and MDCT results were found for bone fraction (r = 0.90 w/o ST, r = 0.84 w ST), trabecular number, and separation. RMS ranged from 10% to 15% for MDCT w/o ST and from 10% to 17% for MDCT w ST. Only bone fraction showed significantly different RMS and correlations for scans w/o vs. w ST (P < 0.05). This study showed that MDCT is able to visualize trabecular bone structure in an in vivo-like setting at skeletal sites within the torso such as the proximal femur. Even though ST scatter compromises image quality substantially, the major characteristics of the trabecular network can still be appreciated and quantified. Funding source Seed grant by the Department of Radiology, University of California, San Francisco, CA, USA     

The Relationship between Osteoarthritis of the Knee and Bone Mineral Density of Proximal Femur: A Cross-Sectional Study from a Korean Population in Women

Background

The relationship between osteoarthritis (OA) and osteoporosis (OP) is complicated and it may differ according to the site or stage of disease. The purpose of this cross-sectional study is to examine the relationship between the severity of radiological knee OA and the degree of OP in the ipsilateral proximal femur as denoted by bone mineral density (BMD) in a Korean population, especially among women.

Methods

One hundred ninety-five female patients who had knee pain and radiological knee OA were investigated with respect to the relationship of knee OA severity with BMD. The BMD of the proximal femur and spine was measured by dual energy X-ray absorptiometry, and the severity of knee OA was evaluated based on Kellgren-Lawrence (K-L) radiographic criteria, joint space narrowing (JSN) and mechanical axis of knee alignment. Partial correlation analysis and ANCOVA adjusted for confounding factors (age and body mass index) were performed to assess the relationship.

Results

There was a statistically significant relationship between the BMD of the proximal femur and JSN, and the BMD of the proximal femur was positively associated with increased joint space width. There was a lack of association between the spine BMD and JSN. The BMD of the proximal femur was also significantly lower in patients who had a higher K-L grade.

Conclusions

The radiographic finding of severe OA in the knee is associated with decreased BMD of the ipsilateral proximal femur including the femoral neck, trochanter, intertrochanter, and region of the entire hip (neck, trochanter, and Ward''s triangle).     

The Combination of Structural Parameters and Areal Bone Mineral Density Improves Relation to Proximal Femur Strength: An In Vitro Study with High-Resolution Peripheral Quantitative Computed Tomography

The aim of this study was to assess structural indices from high-resolution peripheral quantitative computed tomography (HR-pQCT) images of the human proximal femur along with areal bone mineral density (aBMD) and compare the relationship of these parameters to bone strength in vitro. Thirty-one human proximal femur specimens (8 men and 23 women, median age 74 years, range 50–89) were examined with HR-pQCT at four regions of interest (femoral head, neck, major and minor trochanter) with 82 μm and in a subgroup (n = 17) with 41 μm resolution. Separate analyses of cortical and trabecular geometry, volumetric BMD (vBMD), and microarchitectural parameters were obtained. In addition, aBMD by dual-energy X-ray absorptiometry (DXA) was performed at conventional hip regions and maximal compressive strength (MCS) was determined in a side-impact biomechanical test. Twelve cervical and 19 trochanteric fractures were confirmed. Geometry, vBMD, microarchitecture, and aBMD correlated significantly with MCS, with Spearman’s correlation coefficients up to 0.77, 0.89, 0.90, and 0.85 (P < 0.001), respectively. No differences in these correlations were found using 41 μm compared to 82 μm resolution. In multiple regression analysis of MCS, a combined model (age- and sex-adjusted) with aBMD and structural parameters significantly increased R ² values (up to 0.90) compared to a model holding aBMD alone (R ² up to 0.78) (P < 0.05). Structural parameters and aBMD are equally related to MCS, and both cortical and trabecular structural parameters obtained from HR-pQCT images hold information on bone strength complementary to that of aBMD.     

Positive Correlation Between the Femur Neck Shaft and Anteversion Angles: A Retrospective Computed Tomography Analysis in Patients With Developmental Dysplasia of the Hip

BackgroundThis study aimed to explore the anatomical correlation between the femoral neck shaft angle (NSA) and femoral anteversion angle (AA) in patients with developmental dysplasia of the hip based on the Crowe classification and provide a novel method to estimate the femoral AA on anteroposterior pelvic radiographs.MethodsA total of 208 patients with dysplastic hips who underwent total hip arthroplasty at our institution were retrospectively included. Preoperative physiological AA and NSA were determined via 3-dimensional computed tomography. Linear regressions and Pearson’s coefficients were calculated to assess the correlation between the femoral NSA and femoral AA.ResultsA total of 416 hips were divided into 5 subgroups: 99 normal, 143 type I, 71 type II, 63 type III, and 40 type IV hips following the Crowe classification. Dysplastic femurs had significantly higher AAs than normal hips (25.2° vs 31.4° vs 33.3° vs 35.5° vs 41.7°). Significant positive correlations between the AA and NSA were observed in normal (r = 0.635), type I (r = 0.700), type II (r = 0.612), and type III (r = 0.638) hips (P < .001); however, no meaningful correlation was observed in type IV hips (r = 0.218, P = .176).ConclusionThe NSA and AA correlated positively and significantly in the normal and dysplastic Crowe type I-III hips. The relationship between the NSA and AA indicates torsion of the proximal femur and offers an opportunity for straightforward estimation of AA based on NSA.     

In Situ Femoral Dual-Energy X-ray Absorptiometry Related to Ash Weight, Bone Size and Density, and its Relationship with Mechanical Failure Loads of the Proximal Femur

The objective of this study was to directly compare in situ femoral dual-energy X-ray absorptiometry (DXA) and in vitro chemical analysis (ash weight and calcium) with mechanical failure loads of the proximal femur, and to determine the influence of bone size (volume) and density on mechanical failure and DXA-derived areal bone mineral density (BMD, in g/cm²). We performed femoral DXA in 52 fixed cadavers (age 82.1 ± 9.7 years; 30 male, 22 female) with intact skin and soft tissues. The femora were then excised, mechanically loaded to failure in a stance phase configuration, their volume measured with a water displacement method (proximal neck to lesser trochanter), and the ash weight and calcium content of this region determined by chemical analysis. The correlation coefficient between the bone mineral content (measured in situ with DXA) and the ash weight was r= 0.87 (standard error of the estimate = 16%), the ash weight allowing for a better prediction of femoral failure loads (r= 0.78; p<0.01) than DXA (r= 0.67; p<0.01). The femoral volume (r= 0.61; p<0.01), but not the volumetric bone density (r= 0.26), was significantly associated with the failure load. The femoral bone volume had a significant impact (r= 0.35; p< 0.01) on the areal BMD (DXA), and only 63% of the variability of bone volume could be predicted (based on the basis of body height, weight and femoral projectional bone area. The results suggest that accuracy errors of femoral DXA limit the prediction of mechanical failure loads, and that the influence of bone size on areal BMD cannot be fully corrected by accounting for body height, weight and projected femoral area. Received: 26 April 1999 / Accepted: 25 October 1999     

Effects of Treatment of Ovariectomized Adult Rhesus Monkeys with Parathyroid Hormone 1-84 for 16 Months on Trabecular and Cortical Bone Structure and Biomechanical Properties of the Proximal Femur

Treatment of monkeys and humans with parathyroid hormone (PTH) 1-84 stimulates skeletal remodeling, which increases trabecular (Tb) bone mineral density (BMD) but decreases cortical (Ct) BMD at locations where these bone types predominate. We report the effects of daily PTH treatment (5, 10, or 25 μg/kg) of ovariectomized (OVX) rhesus monkeys for 16 months on bone structure and biomechanical properties at the proximal femur, a mixed trabecular and cortical bone site. PTH reversed the OVX-induced decrease in BMD measured by dual-energy X-ray absorptiometry at the proximal femur, femoral neck, and distal femur. Peripheral quantitative computed tomography confirmed a significant decrease in Ct.BMD and an increase in Tb.BMD at the total proximal femur and at the proximal and distal femoral metaphyses. The decrease in Ct.BMD resulted primarily from increased area because cortical bone mineral content was unaffected by PTH. Histomorphometry revealed that PTH significantly increased the trabecular bone formation rate (BFR) as well as trabecular bone volume and number. PTH did not affect periosteal or haversian BFR at the femoral neck, but cortical porosity was increased slightly. PTH had no effects on stiffness or peak load measured using a shear test, whereas work-to-failure, the energy required to fracture, was increased significantly. Thus, PTH treatment induced changes in trabecular and cortical bone at the proximal femur that were similar to those occurring at sites where these bone types predominate. Together, the changes had no effect on stiffness or peak load but increased the energy required to break the proximal femur, thereby making it more resistant to fracture.     

Modeling of Cross-sectional Bone Size, Mass and Geometry at the Proximal Radius: A Study of Normal Bone Development Using Peripheral Quantitative Computed Tomography

It is becoming increasingly accepted that bone size is an important determinant of bone mass. Studies on the development of bone size may therefore promote a better understanding of the basis of diseases which are due to low bone mass. Here, we characterize the temporal changes in cross-sectional bone size, geometry and mass at the radial diaphysis in healthy subjects from 6 to 40 years of age (n= 469; 273 females). Peripheral quantitative computed tomography was used to measure total and cortical cross-sectional area, bone mineral content (BMC) and volumetric bone mineral density (BMD) at the site of the forearm whose distance from the ulnar styloid process corresponded to 65% of forearm length. Over the age range of the study, total cross-sectional area increased by 39 mm² (50%) in females and by 85 mm² (116%) in males. Cortical area increased to a similar extent in both sexes. Between 6–7 years and adulthood, BMC increased by 52 mg/mm (111%) in females and by 73 mg/mm (140%) in males and was significantly higher in males after the age of 15 years. Volumetric BMD increased by 246 mg/cm³ (48%) in females but by only 132 mg/cm³ (23%) in males and was significantly higher in women than in men. In summary, these data show that BMC in men is higher than in women, because periosteal modeling continues longer in boys than in girls. Volumetric BMD is higher in women, partly because the size of the marrow cavity does not increase in girls as it does in boys. Received: 11 May 2000 / Accepted: 11 January 2001