Effect of Ovariectomy, Malnutrition and Glucocorticoid Application on Bone Properties in Sheep: A Pilot Study

The demographic changes in the human population continue to lead to an increasing incidence of osteoporosis. The main clinical symptom of osteoporosis is fracture. Fracture fixation in osteoporosis is frequently complicated by failure of fixation. There is a great need for a large-animal model of osteoporosis for controlled studies, which allows the investigation of fracture healing and fracture treatment in weak bone. Eight swiss mountain sheep, 7–9 years old, were divided into four treatment groups of two animals each. Group 1 was ovariectomized and fed a calcium/vitamin D-restricted diet (O+D). Group 2 was ovariectomized and given a daily intramuscular injection of 25 mg methylprednisolone (O+S). Group 3 was ovariectomized, fed a calcium/vitamin D-restricted diet and injected with 25 mg intramuscular methylprednisolone per day (O+D+S). Group 4 was used as an untreated, not sham operated control group. At the beginning of the study and every 2 months for 6 months the bone mineral density (BMD) was determined using quantitative computed tomography (pQCT) at the distal radius. Biopsies were taken after 6 months from vertebral bodies and femoral heads and the bone structure, i.e. trabecular thickness (Tb.Th), trabecular number (Tb.N), trabecular separation (Tb.Sp), bone surface fraction (BS/BV) and bone volume fraction (BV/TV), was determined by micro-CT. In vitro compression testing of the biopsies was performed to determine failure load and stiffness. The control group showed no changes in BMD. The greatest decrease in BMD was seen in group 3 (O+D+S), which had a decline of 58% in cancellous bone and 22% in cortical bone. In the vertebral body biopsies a prominent change in structural parameters was observed (Tb.N, –53%; Tb.Th, –63%, Tb.Sp, +150%). The changes were less pronounced in the femoral head biopsies. In the compression test the vertebral body biopsies of group 3 (O+D+S) had stiffness values 40% lower failure load 70% lower compared with the control group. The most effective method of inducing osteoporosis in sheep was found to be the combined treatment. These results need to be confirmed in a larger number of animals. Received: 4 May 2001 / Accepted: 13 December 2001     

Intravenous Pamidronate as Treatment for Osteoporosis after Heart Transplantation: A Prospective Study

Fractures due to osteoporosis are one of the major complications after heart transplantation, occurring mostly during the first 6 months after the graft, with an incidence ranging from 18% to 50% for vertebral fractures. Bone mineral density (BMD) decreases dramatically following the graft, at trabecular sites as well as cortical sites. This is explained by the relatively high doses of glucocorticoids used during the months following the graft, and by a long-term increase of bone turnover which is probably due to cyclosporine. There is some evidence for a beneficial effect on BMD of antiresorptive treatments after heart transplantation. The aim of this study was to assess prospectively the effect on BMD of a 3-year treatment of quarterly infusions of 60 mg of pamidronate, combined with 1 g calcium and 1000 U vitamin D per day, in osteoporotic heart transplant recipients, and that of a treatment with calcium and vitamin D in heart transplant recipients with no osteoporosis. BMD of the lumbar spine and the femoral neck was measured by dual-energy X-ray absorptiometry in all patients every 6 months for 2 years and after 3 years. Seventeen patients, (1 woman, 16 men) aged 46 ± 4 years (mean ± SEM) received only calcium and vitamin D. A significant decrease in BMD was observed after 6 months following the graft, at the lumbar spine (−6.6%) as well as at the femoral neck (−7.8%). After 2 years, BMD tended to recover at the lumbar spine, whereas the loss persisted after 3 years at the femoral neck. Eleven patients (1 woman and 10 men) aged 46 ± 4 years (mean ± SEM) started treatment with pamidronate on average 6 months after the graft, because they had osteoporosis of the lumbar spine and/or femoral neck (BMD T-score below −2.5 SD). Over the whole treatment period, a continuous increase in BMD at the lumbar spine was noticed, reaching 18.3% after 3 years (14.3% compared with the BMD at the time of the graft). BMD at the femoral neck was lowered in the first year by −3.4%, but recovered totally after 3 years of treatment. In conclusion, a 3-year study of treatment with pamidronate given every 3 months to patients with existing osteoporosis led to a significant increase in lumbar spine BMD and prevented loss at the femoral neck. However, since some of these patients were treated up to 14 months after the transplant, they may already have passed through the phase of most rapid bone loss. In patients who were not osteoporotic at baseline, treatment with calcium and vitamin D alone was not able to prevent the rapid bone loss that occurs immediately after transplantation. Received: 31 June 2000 / Accepted: 23 August 2000     

Vitamin D Receptor Gene Polymorphisms, Bone Mass, Bone Loss and Prevalence of Vertebral Fracture: Differences in Postmenopausal Women and Men

Bone mineral density (BMD), the major determinant of fracture risk, is under strong genetic control. Although polymorphisms of the vitamin D receptor (VDR) gene have been suggested to account for some of the genetic variation in bone mass, the influence of VDR genotypes on osteoporosis remains controversial. Previous published studies have focused mainly on women, but the pattern of response in men has not been determined. Using the BsmI restriction enzyme, we studied the influence of the different VDR genotypes on bone mass, bone loss and the prevalence of vertebral fractures in a population-based sample of both sexes (n = 326). BMD was measured at the lumbar spine and femoral neck, with a 4-year interval, using dual-energy X-ray absorptiometry. Vertebral fractures were assessed by two lateral radiographs at the beginning and end of the study. The prevalence of the three possible VDR genotypes was similar to those in other Caucasian populations and no differences were found between men and women. Women with the favorable bb genotype showed significantly higher BMD values at the lumbar spine and femoral neck, and a positive rate of BMD change at the femoral neck compared with women with the BB and Bb genotypes. Moreover, women with the bb genotype showed a trend toward a lower prevalence and incidence of vertebral fractures (p= 0.07). We have not found any differences between VDR genotypes in men. In conclusion, VDR gene polymorphisms are related to bone mass and bone loss in women; also a trend in the prevalence of vertebral fractures was observed in postmenopausal women but not in men. Received: 8 June 1998 / Accepted: 7 December 1998     

Contact Quantitative Ultrasound: An Evaluation of Precision, Fracture Discrimination, Age-Related Bone Loss and Applicability of the WHO Criteria

The aim of this study was to assess a dry calcaneal quantitative ultrasound (QUS) device by examining: (i) short- and long-term precision; (ii) the ability of the ultrasound parameters to identify women with vertebral fractures; (iii) age- and menopause-related bone loss; (iv) applicability of the WHO criteria in scan interpretation. The study group consisted of 422 healthy women with no risk factors associated with osteoporosis (227 premenopausal and 195 postmenopausal) and 93 women with one or more vertebral fractures. All women had calcaneal QUS and bone mineral density (BMD) measurements of the lumbar spine and hip performed. Broadband ultrasound attenuation (BUA) and speed of sound (SOS) measurements in the heel were combined and expressed as estimated heel BMD. Short-term precision studies yielded coefficient of variations of 0.3% for SOS, 4% for BUA and 3.3% for estimated heel BMD. Standardized short-term precision values were approximately 0.2 SD. Long-term standardized precision errors ranged from 0.17 to 0.38 SD. All the QUS and BMD measurement parameters showed significant negative relationships with age in the postmenopausal group. Annual losses were 0.35 dB/MHz per year for BUA, 0.56 m/s per year for SOS and 0.002 g/cm² per year for estimated heel BMD. All the QUS and BMD parameters were able to discriminate between healthy postmenopausal women and women with vertebral fracture. Age-adjusted odds ratios for each SD decline in QUS measurements were 3.63, 5.25 and 4.79 for BUA, SOS and estimated heel BMD respectively. Corresponding odds ratios for BMD at the lumbar spine, femoral neck and total hip were 2.39, 2.51 and 2.95 respectively. When the QUS and BMD parameters were expressed as T-scores, estimated heel BMD showed the least age-related decline, while femoral neck BMD displayed the greatest decrease with age. The mean T-score and prevalence of osteoporosis (T<−2.5) for a Caucasian woman aged 60–65 years were −1.35 and 21% respectively for the lumbar spine compared with −0.59 and 2% for estimated heel BMD. In conclusion, this study revealed that contact ultrasound can detect age- and menopause-related influences on bone status and was able to discriminate between healthy individuals and women with vertebral fracture. However, the widely accepted threshold of a T-score of less than −2.5 for the definition of osteoporosis may need modifying for the interpretation of QUS scans. Received: 8 February 1999 / Accepted: 5 May 1999     

A Comparative Study of Computed Digital Absorptiometry and Conventional Dual-Energy X-ray Absorptiometry in Postmenopausal Women

The aim of the study was to evaluate whether computed digital absorptiometry (CDA) of the hand might be a useful screening technique for identifying patients with postmenopausal osteoporosis and to compare the results of CDA with those of dual-energy X-ray absorptiometry (DXA) of the lumbar spine and femoral neck. We studied 230 postmenopausal women (mean age 58.4 ± 7.9 years). For CDA, bone mineral density (BMD) was measured with an AccuDEXA Schick densitometer in the third middle phalanx of the nondominant hand. For DXA, BMD of the lumbar spine and upper femur was assessed using a DXA Hologic QDR-1000 densitometer. We did a comparative analysis (ANOVA) and linear correlation tests. Sensitivity and specificity of CDA and receiver operating characteristic (ROC) curves for the diagnosis of osteoporosis were calculated. The mean BMD with CDA was 0.445 ± 0.084 (T-score: −1.27 ± 1.29). The mean BMD (g/cm²) with DXA at the lumbar spine was 0.877 ± 0.166 (T-score: −1.52 ± 1.59) and 0.708 ± 0.127 at the femoral neck (T-score: −1.12 ± 1.25). BMD at the lumbar spine and femoral neck correlated positively with CDA of the hand (r= 0.66 and r= 0.65 respectively, p<0.001). When using as cut-off a T-score of −2.5, according to WHO criteria, 76 women (33%) had osteoporosis of the lumbar spine and/or femoral neck with DXA and 42 (18%) with CDA (p<0.001). The kappa score for osteoporosis was 0.33 for CDA versus spinal DXA and 0.35 for CDA versus femoral DXA. With the cut-off level used, sensitivity and specificity of CDA in detecting osteoporosis at the lumbar spine were 0.39 and 0.90, respectively; sensitivity and specificity of CDA in identifying osteoporosis at the femoral neck were 0.58 and 0.87, respectively. The positive predictive value of CDA for osteoporosis was 69% and the negative predictive value was 75%. The area under the ROC curve for osteoporosis was 0.822 ± 0.028. We conclude that: (a) CDA assessment has a moderate correlation with BMD measured by DXA at the lumbar spine and femoral neck; (b) CDA has a low sensitivity for the diagnosis of osteoporosis compared with spinal and femoral DXA; and (c) predictive values for osteoporosis at both the lumbar spine and femoral neck are acceptable. Received: September 2000 / Accepted: January 2001     

Intermittent Oral Disodium Pamidronate in Established Osteoporosis: A 2 Year Double-Masked Placebo-Controlled Study of Efficacy and Safety

The effect of oral pamidronate on bone mineral density and its adverse effect profile was investigated by a double-masked placebo-controlled study of 122 patients aged 55–75 years with established vertebral osteoporosis. Patients on active therapy received disodium pamidronate 300 mg/day (group A) for 4 weeks every 16 weeks, 150 mg/day (group B) for 4 weeks every 8 weeks or placebo (group C). All patients additionally received 500 mg of calcium and 400 IU vitamin D daily. Dual-energy X-ray absorptiometry measurements of the spine, hip, forearm and total body were performed at baseline and 6-monthly for 2 years using a Hologic QDR 1000 device at two sites. Serum osteocalcin and urinary deoxypyridinoline were measured at the above visits and at 3 months. The percentage change (SEM) in spine bone mineral density (BMD) at 2 years based on intention-to-treat analysis was 4.64 (1.01) in group A, 6.10 (0.87) in group B and 1.13 (1.32) in group C. Analysis of variance showed significant increases in group A and B compared with placebo (p<0.01). There were also significant rises in femoral neck BMD for group A (p = 0.005), trochanter BMD for groups A and B (p<0.01) and total-body BMD for groups A and B (p<0.001). There was a significant reduction in serum osteocalcin and urinary deoxypyridinoline for groups A and B (p<0.01). There was an excess of gastrointestinal side-effects in the treated groups, particularly group A. We conclude that intermittent pamidronate therapy can prevent bone loss at both the lumbar spine and femoral neck in patients with established vertebral osteoporosis, although due to gastrointestinal side-effects the 300 mg dose in particular does not appear suitable for clinical usage. Received: 12 January 1999 / Accepted: 30 August 1999     

Identification of Women with Reduced Bone Density at the Lumbar Spine and Femoral Neck using BMD at the Os Calcis

We assessed the clinical usefulness of bone density measurements at the os calcis as a screening tool to identify patients with low bone density at the lumbar spine and femoral neck. Bone mineral density (BMD) was recorded in 443 women (mean age 60 years) referred to a bone densitometry service. Measurements were made at the lumbar spine and femoral neck using a Lunar DPXL and at the right os calcis using a Peripheral Instantaneous X-ray Imaging (PIXI) dual-energy X-ray absorptiometry system. Average T-scores derived using the manufacturer”s data were: 1.59 for the lumbar spine, −1.41 for the femoral neck and −0.87 for the os calcis. The prevalence of osteoporosis using WHO criteria (T-scores of −2.5 or less) was 36% for the lumbar spine or femoral neck but only 9.7% for the os calcis. BMD of the os calcis correlated with that at the lumbar spine (r= 0.69, p<0.001) and femoral neck (r= 0.67, p<0.001). The area under the receiver operator characteristics curve was 0.836 (standard error 0.020) for the os calcis related to osteoporosis at the lumbar spine or femoral neck. Optimal accuracy was obtained at a T-score of ≤−1.3 (BMD 0.39 g/cm²) when the sensitivity was 69.6% (95% confidence interval 65.3, 73.9%) and specificity 82.6% (95% confidence interval 79.1, 86.1%). However, the probability of diagnosing low bone density from a given BMD at the os calcis varied by age and site scanned. Accordingly, for informing management strategies, the choice of a single cutoff BMD at the os calcis may not be appropriate and several thresholds may be adopted based on age, the site of interest (lumbar spine or femoral neck) and consideration of associated clinical features. Thus, the use of heel bone density scanners could reduce the number of axial bone density measurements required. The advantages of portability, low cost and shorter scan times should reduce the cost of detection and provide a greater opportunity for identification of women at risk of fracture. Received: 18 June 1999 / Accepted: 30 March 2000     

Estimation of the Prevalence of Low Bone Density in Canadian Women and Men Using a Population-Specific DXA Reference Standard: The Canadian Multicentre Osteoporosis Study (CaMos)

The Canadian Multicentre Osteoporosis Study (CaMos) is a prospective cohort study which will measure the incidence and prevalence of osteoporosis and fractures, and the effect of putative risk factors, in a random sample of 10 061 women and men aged ≥25 years recruited in approximately equal numbers in nine centers across Canada. In this paper we report the results of studies to establish peak bone mass (PBM) which would be appropriate reference data for use in Canada. These reference data are used to estimate the prevalence of osteoporosis and osteopenia in Canadian women and men aged ≥50 years. Participants were recruited via randomly selected household telephone listings. Bone mineral density (BMD) of the lumbar spine and femoral neck were measured by dual-energy X-ray absorptiometry using Hologic QDR 1000 or 2000 or Lunar DPX densitometers. BMD results for lumbar spine and femoral neck were converted to a Hologic base. BMD of the lumbar spine in 578 women and 467 men was constant to age 39 years giving a PBM of 1.042 ± 0.121 g/cm² for women and 1.058 ± 0.127 g/cm² for men. BMD at the femoral neck declined from age 29 years. The mean femoral neck BMD between 25 and 29 years was taken as PBM and was found to be 0.857 ± 0.125 g/cm² for women and 0.910 ± 0.125 g/cm² for men. Prevalence of osteoporosis, as defined by WHO criteria, in Canadian women aged ≥50 years was 12.1% at the lumbar spine and 7.9% at the femoral neck with a combined prevalence of 15.8%. In men it was 2.9% at the lumbar spine and 4.8% at the femoral neck with a combined prevalence of 6.6%. Received: 23 April 1999 / Accepted: 14 April 2000     

Bone Mineral Density and Vertebral Fractures in Men

In women, many studies indicate that the risk of vertebral fragility fractures increases as bone mineral density (BMD) declines. In contrast, few studies are available for BMD and vertebral fractures in men. It is uncertain that the strength of the relationship between BMD and fractures is similar in magnitude in middle-aged men and in postmenopausal women. In the present study, 200 men (mean age 54.7 years) with lumbar osteopenia (T-score <−1.5) were recruited to examine the relationships between spine BMD and hip BMD and the associations of BMD with vertebral fractures. Lumbar BMD was assessed from L2 to L4, in the anteroposterior view, using dual-energy X-ray densitometry. At the upper left femur, hip BMD was measured at five regions of interest: femoral neck, trochanter, intertrochanter, Ward’s triangle and total hip. Spinal radiographs were analyzed independently by two trained investigators and vertebral fracture was defined as a reduction of at least 20% in the anterior, middle or posterior vertebral height. Spinal radiographs evidenced at least one vertebral crush fracture in 119 patients (59.5%). The results of logistic regression showed that age, femoral and spine BMDs were significant predictors of the presence of a vertebral fracture. Odds ratios for a decrease of 1 standard deviation ranged from 1.8 (1.3–2.8) for spine BMD to 2.3 (1.5–3.6) for total hip BMD. For multiple fractures odds ratios ranged from 1.7 (1.1–2.5) for spine BMD to 2.6 (1.7–4.3) for total hip BMD. In all models, odds ratios were higher for hip BMD than for spine BMD, particularly in younger men, under 50 years. A T-score <−2.5 in the femur (total femoral site) was associated with a 2.7-fold increase in the risk of vertebral fracture while a T-score <−2.5 in the spine was associated with only a 2-fold increase in risk. This study confirms the strong association of age and BMD with vertebral fractures in middle-aged men, shows that the femoral area is the best site of BMD measurement and suggests that a low femoral BMD could be considered as an index of severity in young men with lumbar osteopenia. Received: 27 October 1998 / Accepted: 22 February 1999     

Sheep model for fracture treatment in osteoporotic bone: a pilot study about different induction regimens

OBJECTIVE: Various regimens to induce osteoporosis in sheep were compared to establish a large animal model for further studies of fracture healing and fracture treatment in severe osteoporosis. DESIGN: Prospective, randomized animal study (six months' duration). PARTICIPANTS: Eight sheep (seven to nine years old) were divided into four treatment groups of two animals each. INTERVENTION: Group 1: Ovariectomy (OVX) + calcium/vitamin D-restricted diet (O + D); Group 2: Ovariectomy + daily injection of steroids (O + S); Group 3: Ovariectomy + daily injection of steroids + calcium/vitamin D-restricted diet (O + D + S); Group 4: Control, untreated. MAIN OUTCOME MEASUREMENTS: Preoperatively and every 2 months, the bone mineral density (BMD) was determined by quantitative computed tomography (QCT) bilaterally at the distal tibia. Bone structural parameters were determined from iliac crest biopsy specimens using micro-CT. In vitro torsional stiffness of tibia segments was measured. RESULTS: The control group showed a slight increase in BMD with time. The greatest decrease in BMD was seen in Group 3, with a decrease of 55 percent in cancellous bone and 7 percent in cortical bone. In the iliac crest biopsy specimens, trabecular number decreased 19 percent, trabecular thickness decreased 22 percent, and bone volume fraction decrased 37 percent during the 6 months. The torsional strength and stiffness of the tibia showed a difference of approximately 50 percent between Group 3 and the control group. CONCLUSIONS: The induction of severe osteoporosis in sheep is best possible by combined treatment with ovariectomy, calcium/vitamin D-restricted diet, and steroids. There is a good relationship between density, structural parameters, and mechanical properties of bone.