Bone mineral density (BMD) and computer tomographic measurements of the equine proximal phalanx in correlation with breaking strength

Despite the fact that bone mineral density (BMD) is an important fracture risk predictor in human medicine, studies in equine orthopedic research are still lacking. We hypothesized that BMD correlates with bone failure and fatigue fractures of this bone. Thus, the objectives of this study were to measure the structural and mechanical properties of the proximal phalanx with dual energy X-ray absorptiometry (DXA), to correlate the data obtained from DXA and computer tomography (CT) measurements to those obtained by loading pressure examination and to establish representative region of interest (ROI) for in vitro BMD measurements of the equine proximal phalanx for predicting bone failure force. DXA was used to measure the whole bone BMD and additional three ROI sites in 14 equine proximal phalanges. Following evaluation of the bone density, whole bone, cortical width and area in the mid-diaphyseal plane were measured on CT images. Bones were broken using a manually controlled universal bone crusher to measure bone failure force and reevaluated for the site of fractures on follow-up CT images. Compressive load was applied at a constant displacement rate of 2 mm/min until failure, defined as the first clear drop in the load measurement. The lowest BMD was measured at the trabecular region (mean +/- SD: 1.52 +/- 0.12 g/cm2; median: 1.48 g/cm2; range: 1.38-1.83 g/cm2). There was a significant positive linear correlation between trabelcular BMD and the breaking strength (P = 0.023, r = 0.62). The trabecular region of the proximal phalanx appears to be the only significant indicator of failure of strength in vitro. This finding should be reassessed to further reveal the prognostic value of trabecular BMD in an in vivo fracture risk model.

Reduced trabecular bone mineral density and cortical thickness accompanied by increased outer bone circumference in metacarpal bone of rheumatoid arthritis patients: a cross-sectional study

Introduction The objective of this study was to assess three-dimensional bone geometry and density at the epiphysis and shaft of the third meta-carpal bone of rheumatoid arthritis (RA) patients in comparison to healthy controls with the novel method of peripheral quantitative computed tomography (pQCT). Methods PQCT scans were performed in 50 female RA patients and 100 healthy female controls at the distal epiphyses and shafts of the third metacarpal bone, the radius and the tibia. Reproducibility was determined by coefficient of varia-tion. Bone densitometric and geometric parameters were compared between the two groups and correlated to disease characteristics. Results Reproducibility of different pQCT parameters was between 0.7% and 2.5%. RA patients had 12% to 19% lower trabecular bone mineral density (BMD) (P ≤ 0.001) at the distal epiphyses of radius, tibia and metacarpal bone. At the shafts of these bones RA patients had 7% to 16% thinner cortices (P ≤ 0.03). Total cross-sectional area (CSA) at the metacarpal bone shaft of pa-tients was larger (between 5% and 7%, P < 0.02), and relative cortical area was reduced by 13%. Erosiveness by Ratingen score correlated negatively with tra-becular and total BMD at the epiphyses and shaft cortical thickness of all measured bones (P < 0.04). Conclusions Reduced trabecular BMD and thinner cortices at peripheral bones, and a greater bone shaft diameter at the metacarpal bone suggest RA spe-cific bone alterations. The proposed pQCT protocol is reliable and allows measuring juxta-articular trabecular BMD and shaft geometry at the metacarpal bone.

Clinical and radiographic outcome of dental implants supporting fixed prostheses: the relevance of cortical bone formation

To evaluate the hard and the soft tissue parameters around implants supporting fixed prostheses over a period of 5 years and the possible association to the increase in periimplant bone density (IPBD).

Effect of animal species and age on plate-induced vascular damage in cortical bone

Plates used for fracture fixation produce vascular injury to the underlying cortical bone. During the recovery of the blood supply, temporary osteoporosis is observed as a result of Haversian remodeling of the necrotic bone. This process temporarily reduces the strength of the bone. We tackled the postulate that quantitative differences exist between animal species, and in different bones within the same species, due to variations in the relative importance of the endosteal and periosteal blood supplies. Using implants scaled to the size of the bone, we found comparable cortical vascular damage in the sheep and in the dog, and in the tibia and femur of each animal. We observed a significant reduction in cortical vascular damage using plates that had a smaller contact area with the underlying bone. No significant difference in cortical vascular damage was noted in animals of different ages.

Cortical and trabecular bone mineral density in transsexuals after long-term cross-sex hormonal treatment: a cross-sectional study

The aim of this study was to explore the effect of long-term cross-sex hormonal treatment on cortical and trabecular bone mineral density and main biochemical parameters of bone metabolism in transsexuals. Twenty-four male-to-female (M-F) transsexuals and 15 female-to-male (F-M) transsexuals treated with either an antiandrogen in combination with an estrogen or parenteral testosterone were included in this cross-sectional study. BMD was measured by DXA at distal tibial diaphysis (TDIA) and epiphysis (TEPI), lumbar spine (LS), total hip (HIP) and subregions, and whole body (WB) and Z-scores determined for both the genetic and the phenotypic gender. Biochemical parameters of bone turnover, insulin-like growth factor-1 (IGF-1) and sex hormone levels were measured in all patients. M-F transsexuals were significantly older, taller and heavier than F-M transsexuals. They were treated by cross-sex hormones during a median of 12.5 years before inclusion. As compared with female age-matched controls, they showed a significantly higher median Z-score at TDIA and WB (1.7+/-1.0 and 1.8+/-1.1, P < 0.01) only. Based on the WHO definition, five (who did not comply with cross-sex hormone therapy) had osteoporosis. F-M transsexuals were treated by cross-sex hormones during a median of 7.6 years. They had significantly higher median Z-scores at TEPI, TDIA and WB compared with female age-matched controls (+0.9+/-0.2 SD, +1.0+/-0.4 SD and +1.4+/-0.3 SD, respectively, P < 0.0001 for all) and reached normal male levels except at TEPI. They had significantly higher testosterone and IGF-1 levels (p < 0.001) than M-F transsexuals. We conclude that in M-F transsexuals, BMD is preserved over a median of 12.5 years under antiandrogen and estrogen combination therapy, while in F-M transsexuals BMD is preserved or, at sites rich in cortical bone, is increased to normal male levels under a median of 7.6 years of androgen treatment in this cross sectional study. IGF-1 could play a role in the mediation of the effect of androgens on bone in F-M transsexuals.

Microstructural Parameters of Bone Evaluated Using HR-pQCT Correlate with the DXA-Derived Cortical Index and the Trabecular Bone Score in a Cohort of Randomly Selected Premenopausal Women.

BACKGROUND Areal bone mineral density is predictive for fracture risk. Microstructural bone parameters evaluated at the appendicular skeleton by high-resolution peripheral quantitative computed tomography (HR-pQCT) display differences between healthy patients and fracture patients. With the simple geometry of the cortex at the distal tibial diaphysis, a cortical index of the tibia combining material and mechanical properties correlated highly with bone strength ex vivo. The trabecular bone score derived from the scan of the lumbar spine by dual-energy X-ray absorptiometry (DXA) correlated ex vivo with the micro architectural parameters. It is unknown if these microstructural correlations could be made in healthy premenopausal women. METHODS Randomly selected women between 20-40 years of age were examined by DXA and HR-pQCT at the standard regions of interest and at customized sub regions to focus on cortical and trabecular parameters of strength separately. For cortical strength, at the distal tibia the volumetric cortical index was calculated directly from HR-pQCT and the areal cortical index was derived from the DXA scan using a Canny threshold-based tool. For trabecular strength, the trabecular bone score was calculated based on the DXA scan of the lumbar spine and was compared with the corresponding parameters derived from the HR-pQCT measurements at radius and tibia. RESULTS Seventy-two healthy women were included (average age 33.8 years, average BMI 23.2 kg/m(2)). The areal cortical index correlated highly with the volumetric cortical index at the distal tibia (R  =  0.798). The trabecular bone score correlated moderately with the microstructural parameters of the trabecular bone. CONCLUSION This study in randomly selected premenopausal women demonstrated that microstructural parameters of the bone evaluated by HR-pQCT correlated with the DXA derived parameters of skeletal regions containing predominantly cortical or cancellous bone. Whether these indexes are suitable for better predictions of the fracture risk deserves further investigation.

Cortical bone loss at the tibia in postmenopausal women with osteoporosis is associated with incident non-vertebral fractures: Results of a randomized controlled ancillary study of HORIZON

BACKGROUND In postmenopausal women, yearly intravenous zoledronate (ZOL) compared to placebo (PLB) significantly increased bone mineral density (BMD) at lumbar spine (LS), femoral neck (FN), and total hip (TH) and decreased fracture risk. The effects of ZOL on BMD at the tibial epiphysis (T-EPI) and diaphysis (T-DIA) are unknown. METHODS A randomized controlled ancillary study of the HORIZON trial was conducted at the Department of Osteoporosis of the University Hospital of Berne, Switzerland. Women with ≥1 follow-up DXA measurement who had received ≥1 dose of either ZOL (n=55) or PLB (n=55) were included. BMD was measured at LS, FN, TH, T-EPI, and T-DIA at baseline, 6, 12, 24, and 36 months. Morphometric vertebral fractures were assessed. Incident clinical fractures were recorded as adverse events. RESULTS Baseline characteristics were comparable with those in HORIZON and between groups. After 36 months, BMD was significantly higher in women treated with ZOL vs. PLB at LS, FN, TH, and T-EPI (+7.6%, +3.7%, +5.6%, and +5.5%, respectively, p<0.01 for all) but not T-DIA (+1.1%). The number of patients with ≥1 incident non-vertebral or morphometric fracture did not differ between groups (9 ZOL/11 PLB). Mean changes in BMD did not differ between groups with and without incident fracture, except that women with an incident non-vertebral fracture had significantly higher bone loss at predominantly cortical T-DIA (p=0.005). CONCLUSION ZOL was significantly superior to PLB at T-EPI but not at T-DIA. Women with an incident non-vertebral fracture experienced bone loss at T-DIA.

Implant-supported mandibular overdentures and cortical bone formation: clinical and radiographic results

PURPOSE: The aim of this study was to evaluate the hard and soft tissue parameters around implants supporting overdentures and the possible influence of increased periimplant bone density (IPBD) on implant success. MATERIALS AND METHODS: A total of 44 dental implants placed in the mandible of 12 patients were included in the study. Implants were divided in 2 groups in relation to the optically detected IPBD. Periimplant clinical and radiographic variables were collected over the period of 5 years. RESULTS: Periimplant clinical and radiographic parameters for all implants did not change significantly throughout the observation period (P > 0.05). Significant differences were observed between implants with and without IPBD for periimplant soft tissue parameters and Periotest values (P < 0.05). Implants with and without IPBD at 5-year control showed mean bone loss of 0.04 ± 0.48 mm and 0.55 ± 0.96 mm, respectively (P = 0.026). All density values decreased throughout the observation period, except maximal values for implants with IPBD that overcome the initial values at the 5-year control. CONCLUSIONS: Implants supporting overdentures were clinically successful over the period of follow-up. IPBD may be related to the maintenance of the periimplant bone level.

Abnormal bone geometry at the metacarpal bone shaft of rheumatoid arthritis patients with maintained muscle-bone relationship

OBJECTIVES:: Metacarpal juxta-articular bone is altered in Rheumatoid Arthritis (RA). However, a detailed analysis of disease related geometrical adaptations of the metacarpal shaft is missing. The aim of the present study was to assess the role of RA disease, forearm muscle cross-sectional area (CSA), age and sex on bone geometry at the metacarpal shaft. METHODS:: In 64 RA patients and 128 control subjects geometric properties of the third metacarpal bone mid-shaft and forearm muscle CSA were measured by peripheral quantitative computed tomography (pQCT). Linear models were performed for cortical CSA, total bone CSA, polar stress-strain Index (polar SSI, a surrogate for bone's resistance to bending and torsion), cortical thickness and Metacarpal Index (MI=cortical CSA/total CSA) with explanatory variables muscle CSA, age, RA status and sex. RESULTS:: Forearm muscle CSA was associated with cortical and total metacarpal CSA, and polar SSI. RA group status was associated with all bone parameters except cortical CSA. There was a significant interaction between RA status and age, indicating that the RA group had a greater age-related decrease in cortical CSA, cortical thickness and MI. CONCLUSIONS:: Bone geometry of the metacarpal shaft is altered in RA patients compared to healthy controls. While bone mass of the metacarpal shaft is adapted to forearm muscle mass, cortical thickness and MI are reduced but outer bone shaft circumference and polar SSI increased in RA patients. These adaptations correspond to an enhanced aging pattern in RA patients.

Relative Contributions of Osteogenic Tissues to New Bone Formation in Periosteal Distraction Osteogenesis: Histological and Histomorphometrical Evaluation in a Rat Calvaria

Background: The relative contributions of different, potential factors to new bone formation in periosteal distraction osteogenesis are unknown. Purpose: The aim of the present study was to assess the influence of original bone and periosteum on bone formation during periosteal distraction osteogenesis in a rat calvarial model by means of histology and histomorphometry. Methods: A total of 48 rats were used for the experiment. The contribution of the periosteum was assessed by either intact or incised periosteum or an occlusive versus a perforated distraction plate. The cortical bone was either left intact or perforated. Animals were divided in eight experimental groups considering the three possible treatment modalities. All animals were subjected to a 7-day latency period, a 10-day distraction period and a 7-day consolidation period. The newly formed bone was analyzed histologically and histomorphometrically. Results: New, mainly woven bone was found in all groups. Differences in the maximum height of new bone were observed and depended on location. Under the distraction plate, statistically significant differences in maximum bone height were found between the group with perforations in both cortical bone and distraction plate and the group without such perforations. Conclusions: If the marrow cavities were not opened, the contribution to new bone formation was dominant from the periosteum. If the bone perforations opened the marrow cavities, a significant contribution to new bone formation originated from the native bone.

Denosumab Significantly Increases DXA BMD at Both Trabecular and Cortical Sites: Results From the FREEDOM Study

Denosumab is an approved therapy for postmenopausal women with osteoporosis at high or increased risk for fracture. In the FREEDOM study, denosumab reduced fracture risk and increased bone mineral density (BMD). We report the spine and hip dual-energy X-ray absorptiometry (DXA) BMD responses from the overall study of 7808 women and from a substudy of 441 participants in which more extensive spine and hip assessments as well as additional skeletal sites were evaluated. Significant BMD improvements were observed as early as 1mo at the lumbar spine, total hip, and trochanter (all p<0.005 vs placebo and baseline). BMD increased progressively at the lumbar spine, total hip, femoral neck, trochanter, 1/3 radius, and total body from baseline to months 12, 24, and 36 (all p<0.005 vs placebo and baseline). BMD gains above the least significant change of more than 3% at 36 months were observed in 90% of denosumab-treated subjects at the lumbar spine and 74% at the total hip, and gains more than 6% occurred in 77% and 38%, respectively. In conclusion, denosumab treatment resulted in significant, early, and continued BMD increases at both trabecular and cortical sites throughout the skeleton over 36mo with important gains observed in most subjects.

Characteristics and dimensions of the Schneiderian membrane and apical bone in maxillary molars referred for apical surgery: a comparative radiographic analysis using limited cone beam computed tomography

The purpose of the present study was to evaluate the thickness and the anatomic characteristics of the Schneiderian membrane and cortical bone using limited cone beam computed tomography (CBCT) scannning in patients referred for planning of apical surgery of maxillary molars.

Underneath the cerclage: an ex vivo study on the cerclage-bone interface mechanics

Cerclages regain interest due to a rising number of periprosthetic fractures. The contact distribution at the circumferential cerclage-bone interface is still unknown. Local interface pressure depends on the amount of contact area. Cortical damage at the interface would provoke cerclage loosening. Therefore, the contact area, the bone pressure along the interface and the cortical resistance underneath loaded cerclages were determined in an ex vivo model.