Quantitative metrics of bone quality determined at the distal radius using photon-counting CT.

OBJECTIVE: To determine the accuracy of photon-counting-detector CT (PCD-CT) at deriving bone morphometric indices and demonstrate utility in vivo in the distal radius. METHODS: Ten cadaver wrists were scanned using PCD-CT and high-resolution peripheral quantitative CT (HRpQCT). Correlation between PCD-CT and HRpQCT morphometric indices was determined. Agreement was assessed by Lin's concordance correlation coefficient (Lin's CCC). Wrist PCD-CTs of patients between 02/2022 and 08/2023 were also evaluated for clinical utility. Morphometric indices of the in vivo distal radii were extracted and compared between patients with or without osteoporosis. RESULTS: In cadavers, strong correlation between PCD-CT and HRpQCT was observed for cortical thickness (Spearman correlation, ρ, 0.85), trabecular spacing (ρ = 0.98), and trabecular bone volume fraction (ρ = 0.68). Moderate negative correlation (ρ = - 0.49) was observed for trabecular thickness. PCD-CT shows good agreement to HRpQCT for cortical thickness, trabecular spacing, and trabecular bone volume fraction (Lin's CCC = 0.80, 0.94, and 0.86, respectively) but poor agreement (Lin's CCC = - 0.1) for trabecular thickness. In forty participants (31 adults and 9 pediatric), bone morphometrics indices for cortical thickness, trabecular thickness, trabecular spacing, and trabecular bone volume fraction were 0.99 mm (IQR, 0.89-1.06), 0.38 mm (IQR, 0.25-0.40), 0.82 mm (IQR, 0.72-1.05), and 0.28 (IQR, 0.25-0.33), respectively. Patients with osteoporosis had statistically significantly larger trabecular spacing (p = 0.025) and lower trabecular volumetric bone mineral density (p = 0.042). CONCLUSION: This study demonstrates the agreement of PCD-CT to HRpQCT in cadavers of most cortical and bone morphometrics examined and provide in vivo quantitative metrics of bone microarchitecture from routine clinical PCD-CT images of the distal radius.

Effect of masseter muscle mass on the rate of experimental tooth movement in rats.

BACKGROUND: Previous clinical observational studies have suggested that orthodontic tooth movement (OTM) is related, at least partly, to the mass and/or capabilities of the masticatory muscles. OBJECTIVES: Our study aimed to examine the influence of masticatory muscle mass on the OTM in an animal experimental model in which the masseter muscle was modulated by botulinum neurotoxin type A (BTX) injection. METHODS: Eighteen Wistar rats were equally divided into two groups: BTX injection and control. BTX was injected bilaterally into the masseter muscles. Three days after the injection, the maxillary left first molars were orthodontically moved for 14 days. At the end of the experiment, micro-computed tomography was performed to evaluate the rate of OTM and bone morphometry. The masseter muscles were weighed and prepared for histological analyses. RESULTS: The masseter muscle mass in the BTX group was less than that in the control group, and histological findings showed atrophy of muscle fibres. The rate of OTM was significantly higher in the BTX group than in the control group. Furthermore, a negative correlation was detected between masseter muscle mass and OTM in the BTX group. Bone morphometry showed no difference between the control and BTX groups. CONCLUSION: Decreased masseter muscle mass was found to be closely related to an increase in the rate of OTM in rats using BTX injection to modify the masseter muscle mass. Masseter muscle mass could be a predictive factor for OTM in rats injected with BTX.

Analysis of Bone Histomorphometry in Rat and Guinea Pig Animal Models Subject to Hypoxia.

Hypoxia may be associated with alterations in bone remodeling, but the published results are contradictory. The aim of this study was to characterize the bone morphometry changes subject to hypoxia for a better understanding of the bone response to hypoxia and its possible clinical consequences on the bone metabolism. This study analyzed the bone morphometry parameters by micro-computed tomography (µCT) in rat and guinea pig normobaric hypoxia models. Adult male and female Wistar rats were exposed to chronic hypoxia for 7 and 15 days. Additionally, adult male guinea pigs were exposed to chronic hypoxia for 15 days. The results showed that rats exposed to chronic constant and intermittent hypoxic conditions had a worse trabecular and cortical bone health than control rats (under a normoxic condition). Rats under chronic constant hypoxia were associated with a more deteriorated cortical tibia thickness, trabecular femur and tibia bone volume over the total volume (BV/TV), tibia trabecular number (Tb.N), and trabecular femur and tibia bone mineral density (BMD). In the case of chronic intermittent hypoxia, rats subjected to intermittent hypoxia had a lower cortical femur tissue mineral density (TMD), lower trabecular tibia BV/TV, and lower trabecular thickness (Tb.Th) of the tibia and lower tibia Tb.N. The results also showed that obese rats under a hypoxic condition had worse values for the femur and tibia BV/TV, tibia trabecular separation (Tb.Sp), femur and tibia Tb.N, and BMD for the femur and tibia than normoweight rats under a hypoxic condition. In conclusion, hypoxia and obesity may modify bone remodeling, and thus bone microarchitecture, and they might lead to reductions in the bone strength and therefore increase the risk of fragility fracture.

Bone morphology and morphometry of the lateral femoral condyle is a risk factor for ACL injury.

PURPOSE: The purpose of this study was to investigate the influence of the knee lateral compartment bony morphology and morphometry on risk of sustaining an anterior cruciate ligament (ACL) injury. METHODS: A total of 400 age and sex-matched patients (200 ACL-ruptured and 200 ACL-intact) were included. The lateral femoral and tibial bone morphology and morphometric parameters were measured on knee lateral radiographs, taken at 30° of knee flexion with overlapping of the femoral condyles. Radiographic measurements included: anteroposterior-flattened surface of the femur's lateral condyle (XY); femur's diaphysis anteroposterior distance (A); anteroposterior distance of the femur's lateral condyle (B); height of the femur's lateral condyle (C); anteroposterior distance of the tibial plateaus (AB); tibial slope. In addition, three morphological ratios were calculated: B/AB; B/XY; XY/AB (Porto ratio). RESULTS: Most of bone morphological parameters were different between genders (P < 0.05). ACL-ruptured female subjects showed statistical significant smaller condyle heights (C), smaller distances of the flattened surface of the distal femoral condyle (XY), smaller tibial plateau anteroposterior distances (AB), and higher XY/AB ratio (P < 0.05). ACL-ruptured male subjects had statistical significant smaller condyle height (C), anteroposterior distance of the femur's lateral condyle (B), tibial plateau anteroposterior distances (AB), and tibial slope (P < 0.05). Multivariate logistic regression model showed that five morphological parameters (A, XW, XY, XZ, and AB) were significantly associated with ACL rupture (AUC = 0.967, P < 0.001). Calculated ratios (XY/AB; B/AB; B/XY) showed a significant accuracy in identifying individuals with ACL injury (P < 0.001). CONCLUSIONS: The most important finding of this study was that the calculated ratios (XY/AB; B/AB; B/XY) showed a significant accuracy in identifying the individuals with and without an ACL injury. Within this line, a longer flat surface of the lateral femoral condyle or higher Porto ratio (XY/AB) is associated with a lower the risk of ACL injury. Moreover, when considering the combination of five primary bone morphology and morphometric parameters (A, XW, XY, XZ, and AB), the accuracy in identifying these individuals was excellent (AUC = 0.967). These findings may contribute to injury risk assessment, sports participation, and injury prevention counseling and surgical planning refining by identifying high-risk patients who would benefit from the addition of associated procedures to the anatomic ACL reconstruction aiming the improvement of knee stability and decrease the risk of further injuries. LEVEL OF EVIDENCE: III, case-control study.

Comparative Study of Mandible Ramus Morphology Using 3-dimensional CT in Sagittal Split Ramus Osteotomy.

The purpose of the present study was to investigate the relevance of the external morphology of the mandibular ramus, internal bone tissue structure, and maxillofacial morphology at the site for sagittal split ramus osteotomy among different facial skeletal patterns. A total of 80 patients with jaw deformities who underwent sagittal split ramus osteotomy were included in the study. The patients were divided into two groups based on facial skeletal type (skeletal Class II or skeletal Class III). A further 7 patients with no skeletal abnormalities were established as the control group (skeletal Class I). Computed tomography images obtained from these patients were 3-dimensionally reconstructed and the morphology of the mandibular ramus determined. Thickness at the mandibular foramen in Class II was greater than that in Class III, and showed the lowest value at the midpoint of the mandibular foramen and mandibular notch in Class I. Mandibular morphology showed change according to facial skeletal type. Correlations were also observed between the cephalometric analysis values and mandibular morphology.

Subchondral and epiphyseal bone remodeling following surgical transection and noninvasive rupture of the anterior cruciate ligament as models of post-traumatic osteoarthritis.

OBJECTIVE: Animal models are frequently used to study post-traumatic osteoarthritis (PTOA). A common anterior cruciate ligament (ACL) injury model is surgical transection, which may introduce confounding factors from surgery. Noninvasive models could model human injury more closely. The purpose of this study was to compare subchondral and epiphyseal trabecular bone remodeling after surgical transection and noninvasive rupture of the ACL. METHODS: Thirty-six rats were randomized to an uninjured control, surgical transection (Transection), or noninvasive rupture (Rupture). Animals were randomized to 4 or 10 week time points (n = 6 per group). Micro computed tomography (µCT) imaging was performed with an isotropic voxel size of 12 µm. Subchondral and epiphyseal bone was segmented semi-automatically, and morphometric analysis was performed. RESULTS: Transection caused a greater decrease in subchondral bone volume fraction (BV/TV) than Rupture in the femur and tibia. Rupture had greater subchondral bone tissue mineral density (TMD) at 4 and 10 weeks in the femur and tibia. Subchondral bone thickness (SCB.Th) was decreased in the femur in Transection only. Epiphyseal BV/TV was decreased in Transection only, and Rupture exhibited increased femoral epiphyseal TMD compared to both Control and Transection. Rupture exhibited greater femoral epiphyseal trabecular thickness (Tb.Th.) compared to Control and Transection at 4 weeks, and both Rupture and Transection had increased femoral epiphyseal Tb.Th. at 10 weeks. Epiphyseal trabecular number (Tb.N) was decreased in both injury groups at both time points. Femoral and tibial epiphyseal structure model index (SMI) increased in both groups. CONCLUSIONS: The two injury models cause differences in post-injury bone morphometry, and surgical transection may be introducing confounding factors that affect downstream bony remodeling.

Precaudal Vertebrae in the Postcranial Region of Moray Eels Form Ventral Processes.

Fish vertebrae are primarily morphologically classified into precaudal vertebrae jointed to the ribs and caudal vertebrae with hemal spines, through which the caudal artery and veins pass. Moray eels (family Muraenidae) capture prey by directly biting, combining oral and pharyngeal jaw. During feeding motions, they exhibit various head manipulations, such as neurocranial elevation, ventral flexion, and horizontal shaking, with their postcranial region acting like the neck of amniotes. However, the bone morphology supporting these movements remains unclear. In this study, the vertebral morphologies of the Kidako moray (Gymnothorax kidako), starry moray (Echidna nebulosa), pink-lipped moray (Echidna rhodochilus), tidepool snake moray (Uropterygius micropterus), and Seychelles moray (Anarchias seychellensis) were investigated using X-ray computed tomography. These five species exhibited longitudinal ventral processes in the second to approximately 12th precaudal vertebrae with canals for blood vessels, structurally similar to hemal spines. In addition, the morphology of the precaudal vertebrae in three Anguilliformes species closely related to moray eels and two Gasterosteiformes species, including a seahorse that flexes its head ventrally as a feeding motion, was compared with that of moray eels. However, no remarkable ventral processes were observed in their precaudal vertebrae in the postcranial region, suggesting that these structural features in the postcranial vertebrae were preserved in Muraenidae but not necessarily required for the fish to bend its head ventrally. Although the functional significance of the ventral process has yet to be determined, our findings highlight a novel aspect of fish vertebral morphology.

Open the pores - Polydimethylsiloxane influences the porous structure of cancellous bone surrogates for biomechanical testing of osteosyntheses.

Synthetic materials used for valid and reliable implant testing and design should reflect the mechanical and morphometric properties of human bone. Such bone models are already available on the market, but they do not reflect the population variability of human bone, nor are they open-celled porous as human bone is. Biomechanical studies aimed at cementing the fracture or an implant cannot be conducted with them. The aim of this study was to investigate the influence of a cell stabilizer on polyurethane-based cancellous synthetic bone in terms of morphology, compressive mechanics, and opening of the cancellous bone structure for bone cement application. Mechanical properties of cylindrical specimens of the bone surrogates were determined by static compression tests to failure. Furthermore, a morphometric analysis was performed using microcomputed tomography. To prove the open-cell nature of the bone surrogates, an attempt was made to apply bone cement. Effects on the mechanical properties of the polyurethane-based bone surrogates were observed by the addition of polydimethylsiloxane. All mechanical parameters like Young's modulus, ultimate stress and yield stress increased statistically significantly with increasing amounts of cell stabilizer (all p > 0.001), except for yield stress. The analysis of morphometric parameters showed a decrease in trabecular thickness, spacing and connectivity density, which was accompanied by an increase in trabecular number and an increase in pore size. The open-cell nature was proven by the application and distribution of bone cement in specimens with stabilizer, which was visualized by X-ray. In conclusion, the results show that by adding a cell stabilizer, polyurethane-based cancellous bone substrates can be produced that have an open-cell structure similar to human bone. This makes these bone surrogates suitable for biomechanical testing of osteosyntheses and for osteosynthesis cementation issues.

Statistical investigation of interdependence of trabecular microarchitectural parameters from micro-computed tomography.

Standard microarchitectural analysis of bone using micro-computed tomography produces a large number of parameters that quantify the structure of the trabecular network. Analyses that perform statistical tests on many parameters are at elevated risk of making Type I errors. However, when multiple testing correction procedures are applied, the risk of Type II errors is elevated if the parameters being tested are strongly correlated. In this article, we argue that four commonly used trabecular microarchitectural parameters (thickness, separation, number, and bone volume fraction) are interdependent and describe only two independent properties of the trabecular network. We first derive theoretical relationships between the parameters based on their geometric definitions. Then, we analyze these relationships with an aggregated in vivo dataset with 2987 images from 1434 participants and a synthetically generated dataset with 144 images using principal component analysis (PCA) and linear regression analysis. With PCA, when trabecular thickness, separation, number, and bone volume fraction are combined, we find that 92 % to 97 % of the total variance in the data is explained by the first two principal components. With linear regressions, we find high coefficients of determination (0.827-0.994) and fitted coefficients within expected ranges. These findings suggest that to maximize statistical power in future studies, only two of trabecular thickness, separation, number and bone volume fraction should be used for statistical testing.

Bone quality following peripubertal growth in a mouse model of transmasculine gender-affirming hormone therapy.

During peri-puberty, bone growth and the attainment peak bone mass is driven predominantly by sex steroids. This is important when treating transgender and gender diverse youth, who have become increasingly present at pediatric clinics. Analogues of gonadotropin-releasing hormone (GnRH) are commonly prescribed to transgender and gender diverse youth prior to starting gender-affirming hormone therapy (GAHT). However, the impact of GnRH agonists on long bones with the addition of GAHT is relatively unknown. To explore this, we developed a trans-masculine model by introducing either GnRHa or vehicle treatment to female-born mice at a pre-pubertal age. This treatment was followed by male GAHT (testosterone, T) or control treatment three weeks later. Six weeks after T therapy, bone quality was compared between four treatment groups: Control (vehicle only), GnRHa-only, GnRHa + T, and T-only. Bone length/size, bone shape, mechanical properties, and trabecular morphology were modulated by GAHT. Independent of GnRHa administration, mice treated with T had shorter femurs, larger trabecular volume and increased trabecular number, higher trabecular bone mineral density, and wider superstructures on the surface of bone (e.g., third trochanters) when compared to control or GnRHa-only mice. In conclusion, prolonged treatment of GnRHa with subsequent GAHT treatment directly affect the composition, parameters, and morphology of the developing long bone. These findings provide insight to help guide clinical approaches to care for transgender and gender diverse youth.

Morphometric analysis of osteonal architecture in bones from healthy young human male subjects using scanning electron microscopy.

The shape and structure of bones is a topic that has been studied for a long time by morphologists and biologists with the goal of explaining the laws governing their development, aging and pathology. The osteonal architecture of tibial and femoral mid-diaphyses was examined morphometrically with scanning electron microscopy in four healthy young male subjects. In transverse sections of the mid-diaphysis, the total area of the anterior, posterior, lateral and medial cortex sectors was measured and analysed for osteonal parameters including osteon number and density, osteon total and bone area and vascular space area. Osteons were grouped into four classes including cutting heads (A), transversely cut osteons (B), longitudinally cut osteons (C) and sealed osteons (D). The morphometric parameters were compared between the inner (endosteal) and outer (periosteal) half of the cortex. Of 5927 examined osteons, 24.4% cutting heads, 71.1% transversely cut osteons, 2.3% longitudinally cut osteons and 2.2% sealed osteons were found. The interosteonic bone (measured as the area in a lamellar system that has lost contact with its own central canal) corresponded to 51.2% of the endosteal and 52.4% of the periosteal half-cortex. The mean number of class A cutting heads and class B osteons was significantly higher in the periosteal than in the endosteal half-cortex (P < 0.001 and P < 0.05, respectively), whereas there was no significant difference in density. The mean osteon total area, osteon bone area and vascular space area of both classes A and B were significantly higher (P < 0.001 for all three parameters) in the endosteal than in the periosteal half-cortex. The significant differences between the two layers of the cortex suggest that the osteoclast activity is distributed throughout the whole cortical thickness, with more numerous excavations in the external layer, but larger resorption lacunae closer to the marrow canal. A randomly selected population of 109 intact class B osteons was examined at higher magnification (350×) to count osteocyte lacuna and to analyse their relationship with osteon size parameters. The distribution frequency of the mean number of osteocyte lacunae increased with the increment in the sub-classes of osteon bone area, whereas the density did not show significant differences. The number of osteocyte lacunae had a direct correlation with the osteon bone area and the mean osteon wall thickness, as well as the mean number of lamellae. The osteocyte lacunae density showed an inverse relationship. These data suggest a biological regulation of osteoblast activity with a limit to the volume of matrix produced by each cell and proportionality with the number of available cells in the space of the cutting cone (total osteon area). The collected data can be useful as a set of control parameters in healthy human bone for studies on bone aging and metabolic bone diseases.

Effects of Radiotherapy Upon Bone Structure-Strength Relationships Vary With Sex and Fractionation of Dosing.

Background: Radiotherapy for tumor treatment in or near bones often causes osteopenia and/or osteoporosis, and the resulting increased bone fragility can lead to pathologic fractures. Bone mineral density (BMD) is often used to screen for fracture risk, but no conclusive relationship has been established between BMD and the microstructural/ biomechanical changes in irradiated bone. Understanding the effects of radiation dosing regimen on the bone structure-strength relationship would improve the ability to reduce fracture-related complications resulting from cancer treatment. Methods: Thirty-two C57B6J mice aged 10 - 12 weeks old were randomized to single dose (1 x 25 Gy) and fractionated dose (5 x 5 Gy) irradiation groups. Right hindlimbs were irradiated while the contralateral hindlimbs served as the non-irradiated control. Twelve weeks after irradiation, BMD and bone microstructure were assessed with micro-computed tomography, and mechanical strength/stiffness was assessed with a torsion test. The effects of radiation dosing regimen on bone microstructure and strength were assessed using ANOVA, and bone strength-structure relationships were investigated through correlation analysis of microstructural and mechanical parameters. Results: Fractionated irradiation induced significantly greater losses in BMD in the femur (23% - male mice, p=0.016; 19% - female mice) and the tibia (18% - male mice; 6% - female mice) than the single-dose radiation. The associated reductions in trabecular bone volume (-38%) and trabecular number (-34% to -42%), and the increase in trabecular separation (23% to 29%) were only significant in the male mice with fractionated dosing. There was a significant reduction in fracture torque in the femurs of male (p=0.021) and female (p=0.0017) mice within the fractionated radiation group, but not in the single dose radiation groups. There was moderate correlation between bone microstructure and mechanical strength in the single-dose radiation group (r = 0.54 to 0.73), but no correlation in the fractionated dosing group (r=0.02 to 0.03). Conclusion: Our data indicate more detrimental changes in bone microstructure and mechanical parameters in the fractionated irradiation group compared to the single dose group. This may suggest the potential for protecting bone if a needed therapeutic radiation dose can be delivered in a single session rather than administered in fractions.

Effects of Various Copper Sources and Concentrations on Performance, Skeletal Growth, and Mineral Content of Excreta in Broiler Chickens.

The experiment was designed to study the effect of supplemental sources and concentrations of copper on the performance and development and mineralization of tibia bones in broiler chickens. A 42-day feeding experiment was conducted utilising three copper sources, including copper sulphate (CuS), copper chloride (CuCl), and copper propionate (CuP), each with four different concentrations, i.e. 8, 100, 150, and 200 mg/kg. The body weight gain with 200 mg Cu/kg food was noticeably higher during the first 4-6 weeks of age. Due to the interaction between Cu sources and levels, there was no significant change in the body weight gained. The feed intake during various growing phases did differ significantly neither the main effect nor the interaction between different copper sources and levels. A CuP-supplemented diet (200 mg/kg food) considerably (P ≤ 0.05) improved the feed conversion ratio between 4-6 and 0-6 weeks. At the end of the experiment, a total of 72 tibia bones, i.e. six for each treatment were collected. A metabolic trial was conducted to look into mineral retention in broiler chickens on the final 3 days of the trial (40-42 days). Increased tibia bone zinc (Zn) levels were seen with the addition of 8 mg Cu/kg of Cu chloride, 100 mg Cu/kg of Cu propionate, 8 mg Cu/kg of Cu sulphate, and 8 mg/kg of Cu propionate to the diet. At higher levels of Cu (150 and 200 mg/kg diet), there was a significantly (P ≤ 0.01) reduced tibia Zn content. Cu sulphate treatment group had higher (P ≤ 0.01) tibia Cu content (8 mg Cu/kg diet). Cu sulphate supplemented diet had a greater excreta Zn content (P ≤ 0.01) than Cu chloride supplemented diet, and Cu propionate supplemented diet had the lowest excreta Zn content. Excreta with a higher Fe concentration were found in diets supplemented with copper sulphate and copper chloride (P ≤ 0.05) than in diets supplied with copper propionate. Thus, it may be concluded that feeding dietary Cu concentrations up to 200 mg Cu/kg diet, regardless of the different sources, had no negative effects on bone morphometry and mineralization parameters with the exception of a decrease in the tibia's zinc content.

Simultaneous bilateral basicervical femoral neck fractures in a patient with osteomalacia: A case report and literature review.

A thin patient with a history of eating disorders developed basicervical femoral neck fracture bilaterally and simultaneously due to vitamin D deficiency osteomalacia. A careful evaluation in thin patients with thigh pain, including bone biopsy, is required to avoid overlooking osteomalacia.

The influence of zinc and iron intake on osteoarthritis patients' subchondral sclerosis progression: A prospective observational study using data from the osteoarthritis Initiative.

Objective: The purpose of this investigation was to elucidate the relationship between the zinc and iron intake and the advancement of subchondral sclerosis among patients with osteoarthritis (OA). The goal was to establish personalized, nutritionally-informed strategies designed to retard the progression of subchondral sclerosis and conserve joint structure. Methods: For the purposes of this research, we derived data from the Bone Ancillary Study (BAS), a constituent study of the Osteoarthritis Initiative (OAI). The intake of zinc and iron was evaluated via a food frequency questionnaire. Magnetic Resonance Imaging trabecular morphometry was employed to ascertain the microarchitecture of the subchondral bone. For the analysis of collected data, we employed logistic regression along with generalized additive models (GAMs). Results: The participant cohort was comprised of 474 OA patients (216 females, 258 males, mean [SD] age 64.1[9.2]). Notably, an increment in zinc consumption was linked with a significantly reduced likelihood of deterioration in Tb.N (OR = 0.967, 95 % CI, 0.939-0.996, P-value = 0.026), Tb.Th (OR = 0.958, 95 % CI, 0.929-0.989, P-value = 0.008), and Tb.Sp (OR = 0.967, 95 % CI, 0.939-0.996, P-value = 0.013). An elevation in iron intake seemed to enhance the risk of subchondral sclerosis, as indicated by the GAM. Subgroup analysis revealed an interaction between the effectiveness of zinc intake and factors such as gender, age, radiographic severity, and macronutrient consumption. An increased intake of calcium amplified the beneficial impact of zinc on subchondral sclerosis. Conclusions: Our findings indicate a positive association between elevated zinc intake and a slowdown in the progression of subchondral sclerosis in OA patients, notably among females, middle-aged individuals, and those with higher calcium and magnesium intake. Conversely, a higher iron intake might intensify subchondral sclerosis. These results suggest that personalized, diet-based interventions focusing on zinc consumption, in tandem with adequate calcium intake, could potentially decelerate the progression of subchondral sclerosis in individuals afflicted with OA.

Fixation of an orthodontic anchor screw using beta-tricalcium phosphate in a screw-loosening model in rats.

OBJECTIVES: To create an orthodontic anchor screw (OAS)-loosening model and to investigate whether filling the bone hole with beta-tricalcium phosphate (ß-TCP) can fix the OAS against orthodontic force. MATERIALS AND METHODS: Bone holes with different diameters (1.6, 2.1, or 2.5 mm) were drilled in the tibias of 11-week-old male Wistar rats, and an OAS (3.0 mm in length and 1.2 mm in diameter) was inserted. After a healing period of 2 or 4 weeks, orthodontic force was applied, and the diameter of the bone hole appropriate for the loosening model was determined. Subsequently, under the loosening model, the bone hole was filled with ß-TCP, orthodontic force was applied, and movement of the OAS and surrounding tissue changes were evaluated by micro-computed tomography images and histological specimen analysis. RESULTS: The bone hole of 1.6 mm in diameter was employed as the OAS-loosening model. When ß-TCP was inserted into the bone hole, the linear distance and mesial tipping angle of the OAS movement decreased markedly. Furthermore, the values of bone morphometry significantly increased with ß-TCP filling. CONCLUSIONS: An OAS-loosening model was established in rats and demonstrated that the loosening OAS was stabilized by ß-TCP filling through bone formation. ß-TCP may be useful for fixation of a loosening OAS.

Spatiotemporal responses of trabecular and cortical bone to complete spinal cord injury in skeletally mature rats.

Objective: Characterise the spatiotemporal responses of trabecular and cortical bone to complete spinal cord injury (SCI) in the skeletally mature rat in the acute (4-week) period following injury. Methods: The spinal cord of 5-month old male rats was transected at the T9 level. Outcome measures were assessed using micro-computed tomography, three-point bending and serum markers at 1-, 2-, and 4-weeks post-transection. Comparison was made with time-0 and sham animals. Results: Lower levels of circulating serum bone formation markers and higher bone resorption markers suggested uncoupled bone turnover as early at 1-week post-transection. Micro-computed tomography showed metaphyseal and epiphyseal trabecular bone loss was observed only at 4-weeks post-transection. The bone loss was site-specific with a more severe reduction in trabecular BV/TV observed in the metaphyseal (50%) relative to epiphyseal (19%) region. Metaphyseal trabecular bone exhibited a 54% reduction in connectivity density while the epiphyseal trabecular bone was unaffected. Cortical bone deficits were not seen over the time periods examined. Conclusions: The study demonstrates that the skeletally mature spinal cord transected rat model replicates the biphasic pattern of osteoporotic changes observed in the human SCI population, providing a relevant model for testing the efficacy of interventions against SCI-induced osteoporosis.

Mechanical and morphometric characterization of custom-made trabecular bone surrogates.

Synthetic bones for biomechanical testing and surgeon training have become more important due to their numerous advantages compared to human bones. Several bone models are already available on the market, but most of them do not reflect the full range of versatile properties that characterize human bone like population-level influences, size, stiffness, bone-implant-interface or morphometry. Thus, the objectives of this study were to develop synthetic trabecular bone surrogates from polyurethane and varying additives and to determine their elastic and plastic mechanical compressive and additionally morphometric properties. Another aim was to investigate the influence of varying additives on aforementioned properties and finally compare the results with published data from human trabecular bone. Additives used were blowing agents to create a porous structure, mineral fillers to manipulate the basic polyurethane resin, and cell stabilizers to achieve an open porous composition. Mechanical properties were obtained from static compression tests until failure while morphometric analysis was carried out using microcomputed tomography. Thereby, the blowing agent showed the strongest influence on mechanical and morphometric properties with mean Young's moduli ranging from 627 ± 37 MPa (0% blowing agent) to 154 ± 15 MPa (0.25% blowing agent) while the variation of mineral filler content resulted in small standard deviations of approximately 10-20 MPa with a constant proportion of blowing agent. The achieved mechanical properties of the developed synthetic bones, such as the Young's modulus, ultimate stress and yield stress were in accordance with human trabecular bone, while yield strain for all groups was noticeably higher compared to human trabecular bone. Additionally, morphometric analysis showed results indicating similar morphometry of the custom-made synthetic bone and human cancellous bone. Although recreating bone structures in physiological conditions is not simple, the results of the current study show the possibility of developing synthetic bone materials with characteristics like human trabecular bone.

High doses of zoledronic acid induce differential effects on femur and jawbone microstructure.

OBJECTIVES: The aim of this study is to investigate the long-term effects on jaw and femur bone induced by oncologic doses of zoledronic acid in a young rat model. MATERIAL AND METHODS: Six 12-week-old male Wistar rats received zoledronic acid (0.6 mg/kg) and six control rats received saline solution in the same volume. Compounds were administered intraperitoneally in five doses every 28 days. Euthanasia was performed 150 days after therapy onset. After animal sacrifice, their mandibles and femurs were scanned ex vivo using a high-resolution (14 µm) micro-computed tomography. Morphometric bone parameters were calculated using CT-Analyzer (Bruker, Belgium) between the first and second mandibular molars and in the distal femur metaphysis and epiphysis. RESULTS: The treatment group as compared to the controls showed a significantly (p < .05) increased bone quantity (↑BV/TV, ↓Po[Tot], ↑Tb.Th), bone density (↑TMD, ↑BMD), and osteosclerosis of the trabecular bone (↓Tb.Sp, ↓Conn.Dn, ↓Tb.Pf, ↓SMI) in all anatomical sites. Bone remodeling suppression due to zoledronic acid treatment was more pronounced (p < .05) in the femoral metaphysis relative to the mandible and epiphysis. The exploratory linear discriminant analysis showed that for the mandible, it was mainly the bone quantity-related morphometric indices (BV/TV and Tb.Th), while for the femoral epiphysis and metaphysis, it was bone structure-related (Tb.Pf and Tb.N), which are of primary importance to study the treatment effect. CONCLUSION: High doses of bisphosphonates can differently affect the bone quantity, density, and structure in long bones and jawbones. In the metaphysis, bone changes were primarily concentrated in the region of the growth plate. Future studies may consider the use of bone morphometric indices to evaluate the effect of bisphosphonates.

Correlations between radiological and histological findings of bone remodelling and root resorption in a rodent cleft model.

BACKGROUND: The evaluation of bone remodelling and dental root resorption can be performed by histological techniques or micro-computed tomography (micro-CT). The present study aimed to evaluate the relationship between these two procedures in the context of cleft repair in a rat model. METHODS: The reconstructed maxillae and the orthodontically-moved first molar of 12 rats were analysed for correlations between the histological and radiological findings retrospectively. The alveolar cleft repairs were performed using bone autografts or (human) xenografts. Four weeks after the operation, the intervention of the first molar protraction was initiated and lasted for eight weeks. The newly formed bone and the root resorption lacunae were determined via histology. In the micro-CT analysis, the average change of bone mineral density (BMD), bone volume fraction (BV/TV), trabecular thickness and trabecular separation of the jaw, as well as the volume of the root resorptions were determined. The Pearson correlation coefficient was applied to study the associations between groups. RESULTS: Positive correlations were found only between the newly formed bone (histology) and BMD changes (micro-CT) in the autograft group (r = 0.812, 95% CI: 0.001 to 0.979, p = 0.05). The relationship of newly formed bone and BV/TV was similar but not statistically significant (r = 0.691, 95% CI: -0.274 to 0.963, p = 0.013). Regarding root resorption, no significant correlations were found. CONCLUSIONS: Due to the lack of correlation between histological and radiological findings of bone remodelling and the development of root resorptions, both methods should be combined in this cleft model in rats for a comprehensive analysis.