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H K Genant

Publications and source records attributed to H K Genant.

At least 37 records · Page 2Linked to original sources
PubMed2002

The evaluation of a new digital semi-automated system for the radiological assessment of distal radial fractures.

OBJECTIVE: To compare intra- and inter-observer variation for measurements of wrist deformity using a manual method of measurement and a semi-automated digital system developed in our department. DESIGN: Four observers measured radial angle, radial shift, radial length, palmar tilt, and dorsal shift on ten wrist-fracture films using a standardised protocol. Each observer made measurements directly from the radiograph on three occasions, and on a further three occasions digitised images were viewed and measurements made with semi-automated on-screen measurement tools. RESULTS: Manual measurements took 12 min per case compared with 3 min for the digital system. The digital system resulted in improved intra-observer variation for all measurements and an improvement in inter-observer variation for all measurements except posterior tilt. CONCLUSION: The new system allows greater precision in assessing fracture reduction and follow-up. Its principal application is in studies that utilise the wrist as a model for fracture healing.

Humans↗
PubMed2002

Fractures before menopause: a red flag for physicians.

There is substantial interest in the early identification of women at risk for osteoporotic fractures, so that preventive measures may be instituted early. We examined whether women with a history of fractures before menopause were at an increased risk of fractures after menopause. We obtained information about any lifetime fractures of the hip, arm, spine, wrist, leg, ankle, foot and finger from 9086 ambulatory white women ages 65 years and older participating in the Study of Osteoporotic Fractures. We also measured bone mineral density and recorded history of falls, maternal fracture history, drug use, diet, functional status, and other characteristics commonly associated with osteoporotic fractures. We used proportional hazards models to estimate the effects of fractures that occurred before menopause on the risk of fractures after menopause, in particular those that occurred during the 12 years of study follow-up. The risk of fractures of all types during the study period was greater among women with a premenopausal fracture of any type compared with women without a premenopausal fracture (hazard ratio (HR), 1.33; 95% confidence interval (CI), 1.14-1.56; p<0.001). Adjustment for possible confounders, including bone mineral density, had only a modest effect (HR, 1.25; 95% CI, 1.03-1.50; p<0.02). An increased risk of fracture among women with a premenopausal fracture was also seen after stratification by estrogen use, propensity to fall and maternal fracture history. Premenopausal fractures are therefore a risk factor for subsequent fractures independent of other risk factors for osteoporotic fractures, such as bone mineral density. A fracture history, including fractures before menopause, should be obtained when making decisions about preventive treatments.

Aged↗
PubMed2002

Does osteoporosis classification using heel BMD agree across manufacturers?

The lack of standardization in bone mineral density (BMD) measurements is known. Several studies have been carried out to cross-calibrate the axial dual X-ray absorptiometry (DXA) devices. Recently, a number of peripheral DXA (pDXA) densitometers have been introduced. In this study we evaluated the agreement between two heel DXA devices on BMD and T-scores. A total of 99 females aged 21-78 years (ca. 16 per decade) had their non-dominant heel BMD measured using the PIXI (Lunar Inc.) and the Apollo (Norland Medical) pDXA scanners. The mean BMD values were 0.492 and 0.607 g/cm(2) and the mean T-scores using manufacturers' specified reference data were -0.07 and -0.25 for the PIXI and Apollo, respectively. Both the BMD and T-score intermachine relationships were highly correlated but showed significant nonidentity slopes and non-zero offsets. The diagnostic comparison on T-scores resulted in 86% agreement between the instruments (weighted kappa score of 0.550). Normalizing the reference peaks and SDs using this study's young adult population BMD results removed the systematic T-score disagreement. We found that PIXI and Apollo are highly correlated. Differences in BMD values are mainly due to different region of interest (ROI) definitions and additional T-score disagreement reflects the difference in normative databases.

Absorptiometry, Photon↗
PubMed2002

Effects of raloxifene on fracture severity in postmenopausal women with osteoporosis: results from the MORE study. Multiple Outcomes of Raloxifene Evaluation.

Raloxifene reduces the risk of new vertebral fractures, but its effect on the severity of these new fractures has not been determined. The MORE (Multiple Outcomes of Raloxifene Evaluation) trial studied the effects of placebo, raloxifene 60 or 120 mg/day in 7,705 postmenopausal women with osteoporosis. Radiologists assessed new vertebral fractures from radiographs and graded the fracture severity as normal (no fracture) or mild, moderate or severe. New clinical vertebral fractures were defined as new vertebral fractures associated with symptoms, such as back pain, and confirmed in radiographs. In the total study population, the majority (76.4%) of the women who experienced clinical vertebral fractures were diagnosed with new moderate/severe vertebral fractures. In turn, women with moderate/severe vertebral fractures in the overall population were more likely to experience clinical symptoms suggestive of fracture than were women who had new mild-only vertebral fractures. The incidence of new mild-only and moderate/severe fractures was the same in women without prevalent vertebral fractures, but the incidence of new moderate/severe fractures was 2 to 3 times higher than that for new mild-only fractures in women with prevalent vertebral fractures. Raloxifene 60 mg/day decreased the risk of at least 1 new moderate/severe vertebral fracture by 61% in women without prevalent vertebral fractures [RR 0.39 (95% CI 0.17, 0.69)], and by 37% in women with prevalent vertebral fractures [RR 0.63 (95% CI 0.49, 0.83)] at 3 years. The risk reductions for at least 1 new moderate/severe vertebral fracture were not significantly different between the raloxifene doses, in women with and without prevalent vertebral fractures. The effects of raloxifene on significantly decreasing the risk of new moderate/severe vertebral fractures may explain the risk reduction for new painful clinical vertebral fractures observed with raloxifene, and is particularly important in postmenopausal women with severe osteoporosis who are at higher risk for moderate or severe fractures.

Aged↗
PubMed2002

In vivo assessment of architecture and micro-finite element analysis derived indices of mechanical properties of trabecular bone in the radius.

Measurement of microstructural parameters of trabecular bone noninvasively in vivo is possible with high-resolution magnetic resonance (MR) imaging. These measurements may prove useful in the determination of bone strength and fracture risk, but must be related to other measures of bone properties. In this study in vivo MR imaging was used to derive trabecular bone structure measures and combined with micro-finite element analysis (microFE) to determine the effects of trabecular bone microarchitecture on bone mechanical properties in the distal radius. The subjects were studied in two groups: (I) postmenopausal women with normal bone mineral density (BMD) (n = 22, mean age 58 +/- 7 years) and (II) postmenopausal women with spine or femur BMD -1 SD to -2.5 SD below young normal (n = 37, mean age 62 +/- 11 years). MR images of the distal radius were obtained at 1.5 T, and measures such as apparent trabecular bone volume fraction (App BV/TV), spacing, number and thickness (App TbSp, TbN, TbTh) were derived in regions of interest extending from the joint line to the radial shaft. The high-resolution images were also used in a micro-finite element model to derive the directional Young's moduli (E1, E2 and E3), shear moduli (G12, G23 and G13) and anisotropy ratios such as E1/E3. BMD at the distal radius, lumbar spine and hip were assessed using dual-energy X-ray absorptiometry (DXA). Bone formation was assessed by serum osteocalcin and bone resorption by serum type I collagen C-terminal telopeptide breakdown products (serum CTX) and urinary CTX biochemical markers. The trabecular architecture displayed considerable anisotropy. Measures of BMD such as the ultradistal radial BMD were lower in the osteopenic group (p<0.01). Biochemical markers between the two groups were comparable in value and showed no significant difference between the two groups. App BV/TV, TbTh and TbN were higher, and App TbSp lower, in the normal group than the osteopenic group. All three directional measures of elastic and shear moduli were lower in the osteopenic group compared with the normal group. Anisotropy of trabecular bone microarchitecture, as measured by the ratios of the mean intercept length (MIL) values (MIL1/MIL3, etc.), and the anisotropy in elastic modulus (E1/E3, etc.), were greater in the osteopenic group compared with the normal group. The correlations between the measures of architecture and moduli are higher than those between elastic moduli and BMD. Stepwise multiple regression analysis showed that while App BV/TV is highly correlated with the mechanical properties, additional structural measures do contribute to the improved prediction of the mechanical measures. This study demonstrates the feasibility and potential of using MR imaging with microFE modeling in vivo in the study of osteoporosis.

Aged↗
PubMed2002

Measurement of bone mineral density at the spine and proximal femur by volumetric quantitative computed tomography and dual-energy X-ray absorptiometry in elderly women with and without vertebral fractures.

The goal of this study was to determine the effect of vertebral fracture status on trabecular bone mineral density (BMD) measurements obtained in the proximal femur and spine by helical volumetric quantitative computed tomography (vQCT). The study population consisted of 71 Italian women (average age 73 +/- 6) years. This group included 26 subjects with radiographically confirmed atraumatic vertebral fractures and 45 controls. The subjects received helical CT scans of the L1 and L2 vertebral bodies and the hip. The three-dimensional CT images were processed using specialized image analysis algorithms to extract measurements of trabecular, cortical, and integral BMD in the spine and hip. To compare the vQCT results with the most widely used clinical BMD measurement, dual X-ray absorptiometry (DXA) scans of the anteroposterior (AP) spine and proximal femur were also obtained. The difference between the subjects with vertebral fractures and the age-matched controls was computed for each BMD measure. All BMD measurements showed statistically significant differences, which ranged from 7% to 22% between subjects with fractures and controls. Although, given our small sample size, we could not detect statistically significant differences in discriminatory power between BMD techniques, integral BMD of the spine measured by vQCT and DXA tended to show stronger associations with fracture status (0.001 < p < 0.004). Measurements by QCT and DXA at the hip were also associated with vertebral fracture status, although the association of DXA BMD with fracture status was explained largely by differences in body weight between subjects with vertebral fractures and controls.

Absorptiometry, Photon↗
PubMed2002

Influence of region of interest and bone size on calcaneal BMD: implications for the accuracy of quantitative ultrasound assessments at the calcaneus.

There is considerable technological diversity among quantitative ultrasound (QUS) devices used to assess osteoporosis. Because the distance between the transducer and the footplate remains constant, the location of the calcaneus measured will vary with foot size. This study was designed to quantify the variation in bone mineral density (BMD) between a manufacturer's region of interest (ROI_M), which is fixed relative to the footplate, and an anatomical region of interest (ROI_A), which is defined as 20% of calcaneal length. The effect of foot length and width on QUS variables measured using two Food and Drug Administration cleared QUS devices, the Sahara (Hologic) and the Achilles+ (Lunar) was assessed. 26 healthy subjects (12 male and 14 female), aged 22-54 years (35.6+/-10 years) and with foot lengths of 21.5 cm to 29.7 cm (25.1+/-2.3 cm) were recruited. QUS assessments were performed at the right calcaneus. In addition, a Hologic 4500 densitometer was used to measure the BMD of the calcaneus in the ROI_M and ROI_A. The sizes of the ROIs were approximated to the sizes of the transducers of the Sahara and Achilles+ devices. The results showed a significant difference in BMD between the two ROI locations for the Sahara device (BMD 0.642+/-0.135 g cm(-2) vs 0.616+/-0.114 g cm(-2), p=0.014), but no significant difference was found in BMD between the two locations for the Achilles device (BMD 0.661+/-0.120 g cm(-2) vs 0.662+/-0.123 g cm(-2), p=0.818). At the ROI_A, there was a significant difference in BMD between the two QUS devices (p<0.001). The correlation between QUS variables and BMD was slightly higher for the ROI_M (r=0.68-0.79, since this is site-matched) than the ROI_A (r=0.59-0.70) for the Achilles device, while for the Sahara device the correlations were r=0.35-0.40 and r=0.51-0.54, respectively. The smaller ROI of the Sahara device resulted in more than 50% of the subjects having BMD differences of greater than 5% between the ROI_A and the ROI_M, compared with only 20% of the subjects on the Achilles device. ROIs containing cortical bone edge and other soft tissues were found in 58% of cases for the Achilles device and 46% of cases for the Sahara device. The greatest differences occurred in very small and very large feet. Calcaneal length correlated significantly with Sahara speed of sound (SOS), and heel width correlated significantly with Achilles SOS. Heel width also correlated significantly with Sahara broadband ultrasound attenuation (BUA) but not Achilles+ BUA. These results suggest that variation in ROI and bone size might affect the accuracy of QUS measurements, since the calcaneus is heterogeneous both in terms of its external geometry and its internal structure and density.

Adult↗
PubMed2002

Femoral neck and intertrochanteric fractures: radiographic indicators of fracture healing.

Serial hip radiographs from 280 patients with proximal femoral fractures were analyzed retrospectively by 3 radiologists to evaluate conventional radiographic healing patterns. Patients with hemiarthroplasty or insufficient follow-up were excluded. In the remaining 41 patients, the fracture line and callus was assessed. Intertrochanteric fractures demonstrated increasing callus and sclerosis at the fracture site. No such association was seen in femoral neck fractures. Traditional indicators of fracture healing cannot be readily applied at the hip. Radiographic features relate more to fracture type and fixation method.

Adult↗
PubMed2001

Sustained-release sodium fluoride in the treatment of the elderly with established osteoporosis.

BACKGROUND: We ascertained the safety and efficacy of fluoride in augmenting spinal bone mass and reducing spinal fractures in older women with established osteoporosis. We compared a combination of sustained-release sodium fluoride, calcium citrate, and cholecalciferol (SR-NaF group) with calcium and cholecalciferol alone (control group). METHODS: Eighty-five ambulatory women aged 65 years or older with 1 or more nontraumatic vertebral compression fractures were enrolled in a 42-month randomized, double-blind, placebo-controlled trial. Primary outcome measures were vertebral fracture rate, bone mass, and safety. RESULTS: The vertebral fracture rate determined by means of computer assistance in the SR-NaF group was significantly lower than that in the control group (relative risk [RR], 0.32; 95% confidence interval [CI], 0.14-0.73; P =.007). Results of visual adjudicated inspection also confirmed a significant reduction in fracture rate (RR, 0.40; 95% CI, 0.17-0.95; P =.04). Bone mineral density in L2 through L4 increased significantly from baseline in the SR-NaF group by 5.4% (95% CI, 2.7%-8.2%; P<.001), and by 3.2% in the control group (95% CI, 0.8%-5.6%; P =.01). The between-group differences in bone mineral density were not significant. The femoral neck and total hip bone mineral density remained stable in the SR-NaF group and was not significantly different from that of the control group. There were no significant differences in adverse effects between groups. CONCLUSION: The SR-NaF group significantly decreased the risk for vertebral fractures and increased spinal bone mass without reducing bone mass at the femoral neck and total hip.

Aged↗
PubMed2001

Effect of parathyroid hormone (1-34) on fractures and bone mineral density in postmenopausal women with osteoporosis.

BACKGROUND: Once-daily injections of parathyroid hormone or its amino-terminal fragments increase bone formation and bone mass without causing hypercalcemia, but their effects on fractures are unknown. METHODS: We randomly assigned 1637 postmenopausal women with prior vertebral fractures to receive 20 or 40 microg of parathyroid hormone (1-34) or placebo, administered subcutaneously by the women daily. We obtained vertebral radiographs at base line and at the end of the study (median duration of observation, 21 months) and performed serial measurements of bone mass by dual-energy x-ray absorptiometry. RESULTS: New vertebral fractures occurred in 14 percent of the women in the placebo group and in 5 percent and 4 percent, respectively, of the women in the 20-microg and 40-microg parathyroid hormone groups; the respective relative risks of fracture in the 20-microg and 40-microg groups, as compared with the placebo group, were 0.35 and 0.31 (95 percent confidence intervals, 0.22 to 0.55 and 0.19 to 0.50). New nonvertebral fragility fractures occurred in 6 percent of the women in the placebo group and in 3 percent of those in each parathyroid hormone group (relative risk, 0.47 and 0.46, respectively [95 percent confidence intervals, 0.25 to 0.88 and 0.25 to 0.861). As compared with placebo, the 20-microg and 40-microg doses of parathyroid hormone increased bone mineral density by 9 and 13 more percentage points in the lumbar spine and by 3 and 6 more percentage points in the femoral neck; the 40-microg dose decreased bone mineral density at the shaft of the radius by 2 more percentage points. Both doses increased total-body bone mineral by 2 to 4 more percentage points than did placebo. Parathyroid hormone had only minor side effects (occasional nausea and headache). CONCLUSIONS: Treatment of postmenopausal osteoporosis with parathyroid hormone (1-34) decreases the risk of vertebral and nonvertebral fractures; increases vertebral, femoral, and total-body bone mineral density; and is well tolerated. The 40-microg dose increased bone mineral density more than the 20-microg dose but had similar effects on the risk of fracture and was more likely to have side effects.

Bone Density↗
PubMed2001

A comparison of spinal quantitative computed tomography with dual energy X-ray absorptiometry in European women with vertebral and nonvertebral fractures.

Quantitative computed tomography (QCT) was compared to dual X-ray absorptiometry (DXA) measured in the lumbar spine of 508 European women defined as normal without fracture (NoF), or osteoporotic (OP), with either vertebral fracture (VF), or peripheral fracture (PF). The correlations between QCT and DXA BMD measurements were significantly different in normal and in osteoporotic patients, indicating that the two exams do not measure the same bone aspects. According to ROC curves results, QCT Z-scores separate OP from NoF with better sensitivity than all other measurements. A threshold to differentiate OP from NoF was chosen at Z-score = -1 for DXA-BMD and -1.5 for QCT-BMD. VF patients showed a highly significant decrease in BMD by DXA or QCT. PF patients revealed measurements lower than those of normal subjects but greater than those of VF, calling into question the idea of a diffuse osteoporosis causing nonvertebral fractures that is measurable by spinal DXA or QCT. DXA is weakly dependent upon age, and T-score or Z-score are equivalent for evaluating osteoporosis. QCT depends greatly upon age, and Z-score appears to be more efficient.

Absorptiometry, Photon↗
PubMed2001

Is quantitative ultrasound dependent on bone structure? A reflection.

Trabecular bone plays a significant role in maintaining bone structural integrity. Its density is a significant determinant of bone strength and fracture risk, but there is still unexplained variance. It has been suggested that the ability to measure structural information will improve the estimation of bone strength and fracture risk. Quantitative ultrasound (QUS) is a mechanical wave that can be influenced by bone structure, in addition to bone mineral density (BMD). This article reviews the evidence in the literature supporting or refuting this assumption. Theoretically, the propagation of QUS is influenced by both structure and density of the medium. QUS measurement in vivo shows weak but significant association with axial BMD. However, the association becomes stronger when measured in vitro. Broadband ultrasound attenuation (BUA) exhibits a nonlinear relationship with density over a large density range. When cubes of cancellous bone are measured in the three orthogonal directions, both BUA and speed of sound (SOS) show significant anisotropy which mirrors mechanical anisotropy. QUS has also been shown to correlate significantly with structural parameters measured by histomorphometry. However, structure remains a significant predictor after adjustment for BMD mainly in bovine samples. Other studies using phantoms of bone samples have also demonstrated that QUS is dependent on structure. There is preliminary indication that fractal dimensions are significantly associated with QUS. The ultimate usefulness of structural dependence of QUS will be in its ability to improve bone strength estimation above and beyond density. There is ample evidence documenting the ability of QUS to predict bone strength in vitro. BMD is a significant predictor of bone strength and the additive value of structure in estimating bone strength is variable. Clinically, ultrasound of the calcaneus is measured in one direction (medio-lateral) and the structural variation in this direction may be limited. Nevertheless, QUS can provide useful additional information to that provided by axial BMD due in part to different precision and accuracy errors and to biological discordance. On the whole one could conclude that ultrasound attenuation is due to structural parameters and these variables are also dependent on density.

Anisotropy↗
PubMed2001

Treatment of painful osteoporotic vertebral fractures with percutaneous vertebroplasty or kyphoplasty.

Vertebral fracture is the most common complication of osteoporosis. It results in significant mortality and morbidity, including prolonged and intractable pain in a minority of patients. Vertebroplasty and kyphoplasty, procedures that involve percutaneous injection of bone cement into a collapsed vertebra, have recently been introduced for treatment of osteoporotic patients who have prolonged pain (several weeks or longer) following vertebral fracture. To determine the details of the procedures and to gather information on their safety and efficacy, we performed a MEDLINE search using the terms 'vertebroplasty' and 'kyphoplasty.' We reviewed reports of these procedures in patients with osteoporosis. We supplemented the articles found with other papers known to the authors and with presentations at national meetings. Randomized trials of vertebroplasty and kyphoplasty have not been reported. Case reports suggest that these procedures are associated with pain relief in 67% to 100% of cases. Short-term complications, mainly the result of extravasation of cement, include increased pain and damage from heat or pressure to the spinal cord or nerve roots. Proper patient selection and good technique should minimize complications, but rarely, decompressive surgery is needed. Long-term benefits have not yet been shown, but potentially include prevention of recurrent pain at the treated level(s) with both procedures, and, with kyphoplasty, reversal of height loss and spinal deformity, an improved level of function, and avoidance of chronic pain and restriction of internal organs. Possible long-term complications, again not fully evaluated, include local acceleration of bone resorption caused by the treatment itself or by foreign-body reaction at the cement-bone interface, and increased risk of fracture in treated or adjacent vertebrae through changes in mechanical forces. Controlled trials are needed to determine both short-term and long-term safety and efficacy of vertebroplasty and kyphoplasty. Both procedures may be useful for osteoporotic patients who have prolonged pain following acute vertebral fracture. Until there is conclusive evidence for efficacy and long-term safety, these procedures should be done only in carefully selected patients, only by experienced operators with appropriate high-quality imaging equipment, and ideally at centers that are participating in controlled trials.

Back Pain↗
PubMed2001

Standardization of bone mineral density at femoral neck, trochanter and Ward's triangle.

The International Committee for Standards in Bone Measurement (ICSBM) has published standardization formulas for total hip bone mineral density (BMD). In many applications, however, BMD of hip subregions, such as femoral neck (FN), trochanter (TR), and Ward's triangle (WT), are commonly measured. This paper addresses whether the standardization formulas for total hip BMD can be adequately used for hip subregions. We used data from 100 healthy women, from 20 to 80 years old, who had hip BMD measured in both the total hip and hip subregions by a Hologic QDR 2000, a Lunar DPX, and a Norland XR26 Mark II. The same women were used by ICSBM for the standardization of total hip BMD. In addition, we used data of 3139 patients from a clinical trial to validate our results. We derived standardization formulas for FN, TR, and WT using the same statistical method as that used for total hip BMD. We applied both total hip calibration formulas and subregion-specific formulas to the data and compared the corresponding effect. We found that the total hip calibration formulas can partially reduce BMD differences between the Hologic and Lunar as well as the Lunar and Norland scanners in hip subregions, but increase differences between the Hologic and Norland scanners. The subregion calibration formulas are most appropriate for calibrating subregion BMD values and their absolute changes, and should be adopted. Standardization is unnecessary for BMD percentage changes in our clinical trial data.

Absorptiometry, Photon↗
PubMed2001

Vertebral morphometry: a comparison of long-term precision of morphometric X-ray absorptiometry and morphometric radiography in normal and osteoporotic subjects.

Vertebral morphometry, the quantification of vertebral body shape, has proved a useful tool in the identification and evaluation of osteoporotic vertebral deformities in both epidemiologic surveys and clinical trials. Although conventionally it has been performed on lateral radiographs of the thoracolumbar spine (morphometric radiography, MRX), it may now be accomplished on morphometric X-ray absorptiometry (MXA) scans, acquired on dual-energy X-ray absorptiometry (DXA) machines. In this study the long-term precision of vertebral height measurement using MXA and MRX was directly compared. Initially 24 postmenopausal women were recruited (mean age 67+/-5.8 years): 12 normal subjects (group 1) and 12 with osteoporosis and known vertebral deformities (group 2). Each subject attended for a baseline visit at which they had a MXA examination and lateral thoracic and lumbar radiographs. Twenty-one subjects then returned 1.7+/-0.4 years later (10 subjects from group 1 and 11 from group 2) for a follow-up visit to repeat both the MXA scans and conventional radiographs. The baseline MXA scans and conventional radiographs were each analyzed quantitatively by two observers in a masked fashion, using a standard six-point method. The follow-up images were then analyzed by the same observers. The MRX observers were masked to the baseline analyses, while the MXA observers utilized the manufacturer's 'compare' facility. On all scans and radiographs anterior (Ha), mid (Hm) and posterior (Hp) vertebral heights were measured and wedge (Ha/Hp) and mid-wedge (Hm/Hp) ratios calculated for each vertebral body, ideally from T4 to L4. MRX analyzed 129 of the 130 available vertebrae in group 1 at both visits and 141 of the 143 available in group 2, while MXA analyzed 124 vertebrae in group 1 at both visits and 127 in group 2. Intra- and inter-observer precision errors, particularly in terms of coefficient of variation (CV%), were larger for MXA than for MRX in both normal subjects and those with vertebral deformities. For example, intra-observer precision errors for vertebral height measurement were 0.62 mm (2.9%) for MXA compared with 0.63 mm (2.2%) for MRX in group 1 (normal) subjects and 0.82 mm (4.2%) for MXA compared with 0.85 mm (3.3%) for MRX for group 2 (osteoporosis and vertebral deformities) subjects. Both MXA and MRX inter-observer precision was clearly poorer than the intra-observer precision, a problem associated with any morphometric technique. This was particularly noticeable for MXA; for example, precision of vertebral height measurement in group 1 subjects was 0.62 mm (2.9%) for intra-observer compared with 0.99 mm (4.6%) for inter-observer analyses. MXA and MRX intra- and inter-observer precision was significantly poorer for subjects with vertebral deformities compared with those without, with the CV% for subjects with vertebral deformity approximately 50% greater than that of normal subjects. For example, MRX intra-observer precision for the midwedge ratio was 2.6% for group 1 subjects compared with 3.8% for group 2 subjects. The precision of vertebral height measurement on deformed vertebrae of group 2 subjects was poorer than that for normal vertebrae in the same subjects using both MXA and MRX, as a result of increased variability in point placement. For example, MXA intra-observer precision (RMS SD) for the wedge ratio precision was 0.037 (3.9%) for normal vertebrae compared with 0.060 (6.6%) for deformed vertebrae. We conclude that MXA precision was generally poorer than MRX, although both techniques were adversely affected by the presence of vertebral deformities and the use of more than one observer. Although precision errors for both techniques were substantially smaller than the 20-25% reduction in vertebral height frequently proposed to identify incident deformities, the poorer precision of MXA may lead to an increased risk of erroneous classification of vertebrae as normal or deformed.

Absorptiometry, Photon↗
PubMed2001

Quantitative ultrasound of the tibia depends on both cortical density and thickness.

This study investigated whether tibial speed of sound (SOS; SoundScan 2000, Myriad Ultrasound Systems, Israel) reflects not only bone mineral density (BMD) but also tibial cortical thickness, as assessed by dual-energy X-ray absorptiometry (DXA) and Quantitative CT (QCT) at a site-matched location. The secondary focus of the study was how tibial SOS compares with BMD at the spine and the hip, the most widely used locations for densitometry. Twenty-two young normal (N) and 23 postmenopausal women with spinal fractures (Fx) (mean (SD) age 35 (8) and 70 (5) years) underwent quantitative ultrasound (QUS) SOS measurement at the left tibial midshaft. From site-matched QCT scans (three 3-mm slices spaced along the QUS measurement region), BMD and cortical thickness were computed (QCT-cBMD, QCT-cTh). The cortex in the CT images was then subdivided into three concentric and equally spaced bands, and QCT-cBMD was computed separately for each band. DXA was performed at the mid-tibia (TIB BMD), at the spine (SPINE BMD) and the hip (total hip, HIP BMD). Correlation coefficients between parameters were determined with least-square linear fits. Intergroup differences were assessed by analysis of covariance, whose r2 value reflects the percentage variation in the data explained by group assignment. SOS correlated significantly with site-matched parameters (QCT-cBMD, OCT-cTh and TIB BMD, all r = 0.6, p < 0.001), SPINE BMD and HIP BMD (both r = 0.5, p < 0.001). Multiple regression with both QCT-cBMD and QCT-cTh against SOS yielded r = 0.7 with both parameters contributing significantly. For the cortex band subdivision, SOS correlated better with QCT-cBMD in the outermost band of the cortex (r = 0.67) than with the more central bands (r = 0.59 and r = 0.53). Group assignment could best explain SPINE BMD (r2 = 0.62) and HIP BMD (r2 = 0.51). SOS was comparable to TIB BMD (r2 = 0.3 vs. r2 = 0.35).: Our findings suggest that the tibial SOS measurement depends on both the thickness and density of the tibia, but is more strongly influenced by the density of the cortex near the surface than by its interior parts. The power of tibial ultrasound to discriminate between normal and fracture patients was less than that of spinal and femoral DXA BMD and comparable to site-matched DXA BMD.

Absorptiometry, Photon↗
PubMed2001

Structural analysis of high resolution in vitro MR images compared to stained grindings.

The recent advancement of high resolution magnetic resonance imaging has opened up new avenues for the determination of structural characteristics of the trabecular network, which may significantly improve the diagnosis of osteoporosis. An analysis of the calcaneus in healthy women has shown similar age-related changes when comparing structural parameters in high resolution MR images and BMD as measured by DXA [1]. Here we undertook an in vitro study to further compare structural measurements in MR images with those from stained grindings. A 3D gradient echo sequence on a 1.5 T scanner was used to obtain four contiguous sagittal MR images with a slice thickness of 1 mm and an in plane pixel size of 195 microns. Twenty-one stained grindings with a slice thickness of 1 micron each were obtained from a 3 mm thick slab of the same volume investigated by MR. The stack of stained grindings was also used to simulate the influence of variations in slice thickness and in plane resolution. Results for structural parameters derived from the high resolution MR images differed considerably from those derived from the stained grindings because the MR images are heavily influenced by partial volume artifacts. This finding was supported by simulations which also revealed that even at a slice thickness of 500 microns and an in plane pixel size of 13 microns, accurate results could not be obtained when a histomorphometric type analysis was applied. Results also depended strongly on the segmentation method. However, contrary to the stained grindings, images averaged over several slices reveal the three-dimensional network character of the trabecular structure. New efforts should be undertaken to develop analysis strategies that are more adequate for in vivo high resolution images instead of using analysis techniques applied in classical histomorphometry.

Cadaver↗