Real Bone Research Articles

Generation of a 3D Printed Temporal Bone Model with Internal Fidelity and Validation of the Mechanical Construct

To generate a rapid-prototyped temporal bone model from computed tomography (CT) data with a specific focus on internal anatomic fidelity. Research ethics board-approved prospective cohort study. Current iterations of a rapid-prototyped temporal bone model are complicated by absent void spaces and inconsistent bone density due to limited infiltrant exposure. The creation of a high-fidelity model allows surgical trainees to practice in a standardized and reproducible training environment. This learning paradigm will significantly augment resident understanding of surgical approaches and techniques to prevent adverse outcomes. We describe a technique for generating internally accurate rapid-prototyped anatomical models with solid and hollow structures, including void spaces. The novel slicing algorithm digitally deconstructs a model into segments and permits removal of extraneous print material and allows infiltrant penetration of the entire bone structure. Precise reassembly is facilitated by digitally generated fiducials. Infiltrant of choice was determined by expert assessment and subjected to objective mechanical property assessment with comparison to cadaveric sheep bone. The printed bone models are highly realistic. Void space representation was excellent with 88% concordance between cadaveric bone and the resultant rapid-prototyped temporal bone model. Ultimately, cyanoacrylate with hydroquinone was determined to be the most appropriate infiltrant for both cortical and trabecular simulation. The mechanical properties of all tested infiltrants were similar to real bone. This model serves as an excellent replica of a human temporal bone for training and preoperative surgical rehearsal and can be dissected in a true-to-life fashion.

A new technique for the assessment of the 3D spatial distribution of the calcium/phosphorus ratio in bone apatite

The value and distribution of calcium/phosphorus (Ca/P) ratio in bone vary between healthy and osteoporotic bone. The purpose of this study was the development of a technique for the assessment of the 3D spatial distribution of Ca/P ratio in bone apatite, which could eventually be implemented through a conventional computed tomography (CT) system. A three-material mass-fraction decomposition CT dual energy analysis was optimized. The technique was validated using ten bone phantoms of different, known Ca/P ratio. Their measured average Ca/P ratio showed a mean/maximum deviation from the expected Ca/P ratio of 0.24/0.35. Additionally, three healthy and three inflammation-mediated osteoporotic (IMO) collagen-free rabbit tibia bone samples were assessed, providing promising preliminary results on real bone tissue. The average Ca/P ratios in all IMO samples (1.64–1.65) were found to be lower than in healthy samples (1.67–1.68). Osteoporotic regions in IMO samples were located using Ca/P ratio colour maps and Ca/P ratio values as low as 1.40 ± 0.26 were found. The low Ca/P ratio volume proportion in IMO samples (12.8%–13.9%) was found to be higher than in healthy (5.8%–8.3%) samples. A region growing technique showed a higher homogeneity of Ca/P ratio in healthy than in IMO bone samples.

Measurements of ultrasound velocity and attenuation in numerical anisotropic porous media compared to Biot’s and multiple scattering models

This article quantitatively investigates ultrasound propagation in numerical anisotropic porous media with finite-difference simulations in 3D. The propagation media consist of clusters of ellipsoidal scatterers randomly distributed in water, mimicking the anisotropic structure of cancellous bone. Velocities and attenuation coefficients of the ensemble-averaged transmitted wave (also known as the coherent wave) are measured in various configurations. As in real cancellous bone, one or two longitudinal modes emerge, depending on the micro-structure. The results are confronted with two standard theoretical approaches: Biot’s theory, usually invoked in porous media, and the Independent Scattering Approximation (ISA), a classical first-order approach of multiple scattering theory. On the one hand, when only one longitudinal wave is observed, it is found that at porosities higher than 90% the ISA successfully predicts the attenuation coefficient (unlike Biot’s theory), as well as the existence of negative dispersion. On the other hand, the ISA is not well suited to study two-wave propagation, unlike Biot’s model, at least as far as wave speeds are concerned. No free fitting parameters were used for the application of Biot’s theory. Finally we investigate the phase-shift between waves in the fluid and the solid structure, and compare them to Biot’s predictions of in-phase and out-of-phase motions.

A Comment on ‘Changes in Bone Mineral Density in Women Following 1-year Gastric Bypass Surgery’ Published by Casagrande DS et al.

Sirs,In a recent issue of Obesity Surgery, a study on longitudinalchanges in bone mineral density (BMD) after gastric bypasssurgery [1] was published. The authors presented severallaboratory data and BMD measurements at the spine andproximal femur at baseline and follow-up. Generally,both laboratory variables and BMD results have changedsignificantly. However, we have comments concerningmethodology of BMD measurements and the way of theirpresentation.Firstly, in a description of densitometry, the authors didnot provide a precision expressed as coefficient of variation(CV%). This information is especially important in a longi-tudinal observation. In each densitometry unit, serial mea-surements should be performed and CV% should beestablished. Moreover, in a prospective study, it is necessaryto calculate the value of the least significant change (LSC)using a common formula: RMS_CV×2×1.41. The use ofLSC allows to establish whether the BMD change in anindividual subject exceed the value of LSC.The authors presented changes in BMD only as meanexpressed in percent. Such way of presentation does notexpress real bone changes in a satisfactory manner. Onemay expect that due to precision error BMD change not ineach patient will exceed the value of LSC. In our recentstudy, we performed measurements in 29 women after lapa-roscopic sleeve gastrectomy, and after 6 months, BMD havedecreased for femoral neck, total hip and spine by 1.24, 6.99and 5.18 %, respectively [2]. We also performed an analysisof changes in individual patients using LSC, and such wayallowstoestablishthatchangeinBMDwasnotpresentinallpatients. For spine, BMD decreased only in 38 % of allwomen, andin three of them BMD even increased. In regardto femoral neck BMD, real decrease was noted in 72 %, andfor total hip BMD, a decrease exceeding the value of LSCwas observed in 82 % of all subjects studied. For hip densi-tometric measurements, an increase was not noted but insome women a decrease was not present.Our analysis confirms that we should not expect thepresence of significant bone changes in all subjects aftersurgical method of treatment of obesity. We recommend forauthorsofthecommentedstudytopresentsuchdatathatwillhelpinbetterunderstandingofbonechangesinsubjectsaftersurgical obesity management.References

High Speed Fracture Fixation: Assessing Resulting Fixation Stability and Fastener Withdrawal Strength

A new method of bone fracture fixation has been developed in which fixation darts (small diameter nails/pins) are driven across a fracture site at high velocity with a pneumatically powered gun. When fixation darts are inserted oblique to one another, kinematic constraints prevent fragment motion and allow bone healing to progress. The primary aim of this study is to determine if fixation darts can provide reasonable fixation stability compared to bone screws, which were used as a benchmark since they represent a simple, yet well-established, surgical technique. The first objective was to evaluate macro-level stability using different numbers of darts inserted parallel and oblique to each other; experimental comparisons were undertaken in a bone analog model. Experimental results showed fixation darts could not be substituted for screws on a one-to-one basis, but that a plurality of fixation darts provided comparable fixation to two bone screws while allowing for faster insertion and damaging less bone. A second objective was to evaluate micro-level stability; a finite element model was created in order to provide a detailed look at the stress state surrounding the fixation darts and the evolution of the fracture gap. Even with relatively weak fixation dart configurations, the fracture gap was maintained below physiological thresholds for bone healing. Most failures of the fixed fractures were attributed to fixation dart pullout from the cancellous structure. The final objective of the study was to characterize this mode of failure with separate fixation dart and screw pullout tests conducted in Sawbones® cancellous foam and fresh porcine cancellous bone. The results showed that the cancellous foam was an acceptable substitute for real bone and provided a conservative estimate of the fixation darts' performance relative to bone screws. A final comparison between experimental and numerically predicted pullout strengths provided confirmation that the model and experiments were consistent.

Biological Evaluation of Polydimethylsiloxane Modified by Calcium Phosphate Nanoparticles for Potential Application in Spine Surgery

The biological properties of a composite made of polydimethylsiloxane matrix and two kinds of calcium phosphate nanoparticles (hydroxyapatite, beta tricalcium phosphate) were tested by means of in vitro and in vivo investigations. Chemical and phase analyses of the nanoparticles were performed. The effects of different volume fractions of nanoparticles were investigated. Human osteoblast-like cell cultures (MG 63) demonstrated that the addition of 5–15 vol.% of nanoparticles had a significantly positive effect on osteoblast viability, and that high concentration did not support cell proliferation. The highest rates of osteointegration in pig bone were attained for implants modified by 15 vol.% hydroxyapatite and more intensive formation of new bone tissue was observed. Our study indicates that hydroxyapatite probably better imitates the composition and structure of the mineral phase of real bone.

A Dispute Over Superposition: John Wallis, Honoré Fabri, and Giovanni Alfonso Borelli

This paper aims first and foremost to unravel and clarify an interesting 17th century controversy around superposition in projectiles, which allegedly existed between the French Jesuit Honoré Fabri and the Italian physicist and astronomer Giovanni Alfonso Borelli. This conflict – initially described by the English mathematician John Wallis in a letter from 1670 to the secretary of the Royal Society – has been erroneously identified with Fabri's Dialogi physici (1669), a work written in response to Borelli's De vi percussionis (1669). In fact, this “conflict” was nothing but Wallis's account of a contradiction between Borelli's above mentioned work and Fabri's Tractatus physicus de motu locali from 1646, while Fabri's 1669 work expressed views very different from those contained in his Tractatus physicus. I will try here to reconstruct Fabri's change of heart between 1646 and 1669 concerning projectiles and superposition, while tracing the real bone of contention between (the later) Fabri and Borelli – superimposing contrary motions – to its Aristotelian origins. My analysis will lead me to problematize the way modern historians usually interpret the relation between Aristotle's physical thinking and projectile theories of early modern theoreticians (e.g. Nicollò Tartaglia's).

3D Finite-Element Modelling of Drilling Cortical Bone: Temperature Analysis

Bone drilling is a key part of major orthopaedic surgeries for fixing fractured bones and replacing damaged joints. One of the main problems in bone drilling is thermal necrosis of tissue, which can occur due to elevated temperatures in the drilling zone. Investigation of the temperatures arising in bone drilling is necessary to analyse the extent of bone necrosis. This paper presents a three-dimensional thermo-mechanical finite-element model of a bone-drilling process to study the effect of drilling parameters (cutting speed and feed rate) and cooling conditions (air and saline solution) on the temperature in drilled bone. The drilling speed was found to have a higher effect compared to that of the feed rate in inducing thermal necrosis in bone for the tested cooling environments. The level of necrosis penetration into bone was strongly affected by the drilling speed and the application of saline cooling (irrigation) in the drilling zone. A considerable extent of necrosis was predicted even at lower drilling speeds when no cooling was used. Drilling experiments were performed on real cortical bone to measure temperatures near the immediate vicinity of the drill. Calculated temperatures were compared with experimental values and were found to be in good agreement with them.

Modelling and static analysis of femur bone by using different implant materials

Femur is leg bone of the human body Undergoing more deformation. Biomechanics is the theory of how tissues, cells, muscles, bones, organs and the motion of them and how their form and function are regulated by basic mechanical properties. The aim of this study is to create a model of real proximal human femur bone and the behavior of femur bone is analyzed in ANSYS under physiological load conditions. A finite element model of bones is generated by using CT scan data are being widely used to make realistic investigations on the mechanical behavior of bone structures. . Orthopedic implantation is done in case of failure. Before implantation it is necessary to analyze the perfectness in case of its material property, size and shape, surface treatment, load resistance and chances of failure. Analysis is done for the stresses formed in different femur implant materials under static loading condition using ANSYS software. Analysis is done on different materials like structural steel, and Ti-6Al-4V implant materials. Since each femur carries 1/2 the body weight , analysis is done for 550kg,650kg, 750kg load, including the cases of patient carrying certain weight. And based on the analysis it can be concluded that, while comparing these two implant materials Ti-6Al-4V gave less deformation on static load conditions. TI-6AL4V is a low density material, which has excellent bio compatible and mechanical properties, it is ideal for the use of an implant in surgeries. Finally the success of implantation depends on implant material and size, implantation method and its handling by the patient.

Preparation and Characterization of Porous Nanosized Hydroxyapatite/Collagen Composite as Bone Scaffold

Inorganic-organic composites could mimic the composite nature of real bone and combine the toughness of a polymer with the strength of an inorganic one to generate bioactive materials with improved mechanical properties and degradation profiles. In this paper, HAp/Col porous scaffold was prepared based on inorganic nano-sized hydoroxyapatite (nHAp) and organic collagen (Col) by solvent casting/particulate leaching. Sodium chloride (NaCl) and ethyl cellulose (EC) were performed as the porogenic agent and binding agent, respectively. The physical, chemical and biodegradation property of this scaffold were investigated in vitro and its co-culture with cells was also studied. The results showed that the scaffold had good mechanical property with the average pore sizes about 150 μm and porosities as high as 75%. This nHAp/Col porous scaffold had no cytotoxicity to mouse pre-osteoblast MC3T3-E1 and the content of alkaline phosphatase (ALP) was ascending with the extension of culture time. The results of mineralization indicated that HAp/Col scaffold could promote the proliferation, differentiation and biological mineralization of MC3T3-E1.

Effect of Screws Placement on Locking Compression Plate for Fixating Medial Transverse Fracture of Tibia

Locking Compression Plates (LCP) are useful fixation devices for tibia and other human long bones. Orthopedists use LCPs with various numbers of holes to fix bone fractures (1) . Not all of holes on plates are often used with Screws so various screw positioning is possible in operations. In this research, a 3D model of tibia is created with the exact geometry of the real bone by using CT scan images of the human right leg .It was materialized by MIMIX and developed in ABAQUS software. This was done considering whole bone material including bone marrow and cancellous bone that have been mostly ignored in previous researches (2) . The model is mechanically validated and verified in comparison with response and behavior of previous cadaveric bone studies (3) . Comparing the stress and stiffness in various positioning of screws on a stainless steel 11 holes LCP used for fixating tibia with a medial transverse fracture in various treatments and finding the optimized screw omission, was the purpose of this paper which can help orthopedists to choose the suitable cases of screws positioning of fixation devices.

The feasibility of wavelength dispersive X-ray fluorescence spectrometry for the assessment of lead concentration in animal bone powder

This work demonstrates the feasibility of wavelength dispersive X-ray fluorescence for the assessment of lead in animal bone powder. When applied to real bone samples, this analytical procedure produced results compatible with current knowledge of lead metabolism, emerging as an important tool in the investigation of relevant issues in Public Health.

Could BMD Reflect the Real Change in Human Bone Mineral?

Background: Bone mineral density (BMD) is an important index in diagnosing osteoporosis and other metabolic bone diseases, predicting fractures, and monitoring treatment. Dual-energy X-ray absorptiometry (DXA) is most widely used technique for assessments of BMD and considered as the gold standard for the minumum exposure to radiation, low cost, high reproducibility, and ease of use. Author performed an experimental study to determine the relationship between the change in BMD measured by DXA and real change in mineral of human long bone. Materials and Methods: A pair of humeri and femora from one male cadaver was cut into specimen about half in length. Three specimens from a pair of humerus and 4 specimens from a pair of femur were immersed into 1N HCl from 10 minutes to maximum 70 minutes with 10 minutes’ interval for different level of demineralization. All 7 specimens were checked with BMD using by DXA (GE-Lunar Prodigy) and analysed respectively. The amount of calcium and phosphorus both from demineralized and normal area were measured and expressed in percentage of demineralizatioin. Results: As demineralization was going on with time of immersion into HCl, there was statistically significant correlation between the change of BMD and real change of calcium amount (?50.65) in humerus, and also in femur (?50.63). There was statistically significant correlation only in femur between BMD and phosphorus (?50.77), and not in humerus (?50.42). In summary, there was a high linear regression between BMD and real bone mineral with minimum of 89% and maximum of 97% as coefficient of determination (R-Square; R2) (p! 0.05). Through correlation analysis, correlation coefficient (?) between BMD measured by DXA and mineral of human long bone showed a high correlation as maximum of 0.84 (p!0.05). Conclusions: Our study showed a statistically significant high relationship between BMD measured by DXA and mineral of human long bone. Therefore, the measurement of DXA is considered to reflect the real change of mineral in human long bone as well as that of BMD. The limitation of this study was that it was based on artificially induced demineralization only one pair of cadaveric humerus and femur so that vertebrae were excluded.

The absorbed dose in femur exposed to diagnostic radiography

A femur phantom made of wax and a real human bone was used to study the dose during radiographical procedures. The depth dose inside the phantom was determined using DOSXYZnrc, a Monte Carlo simulation software. The results were verified with measurements using TLD-100H. It was found that for 2.5 mm aluminium filtered 84-kVp X-rays, the radiation dose in the bone reached 57 % higher than the surface dose, i.e. 3.23 mGy as opposed to 2.06 mGy at the surface. The use of real bone introduces variations in the bone density in the DOSXYZnrc model, resulting in a lower attenuation effect than expected from solid bone tissues.

3D Reconstruction to Detect Fish Bones in Foreign Body Models

Objective: When fish bones are impacted in pharynx or in esophagus, it’s hard to find them with simple radiography. We designed foreign body models with fish bones and used their computed tomogram data to make 3D reconstructed images. Various modifications of 3D data were tested for foreign body detection. Method: Bones from 3 species of fishes frequently consumed in Korea were used as foreign body models. Fish bones were sandwiched between plates of fish paste. Computed tomograms taken were converted into 3D images. Multi-planar reconstruction, volume rendering, and virtual endoscopy were used to determine the characteristics of fish bones. Results: Shapes of the bones are easily reconstructed for the mandible. Gill cover and spine cannot be reconstructed perfectly. The shape could be figured out in every reconstructed image in volume rendered images after removal of soft tissue data. In measuring size, plane CT are useful in detecting margins. Volume rendered images also were suitable in measuring the size. The location of the foreign bodies could be easily measured if the reference point is given. The axial CT image or 3D images are both useful in calculating distance from the reference point. In view of orientation, 3D images are best of all. Conclusion: Searching for fish bones and gathering information about them are difficult tasks in esophageal foreign body cases. Fish bone foreign body models and their reconstructed images are useful in getting information about size, shape, location, and orientation. This technique could be applied in finding real fish bone foreign bodies.

Trabecular Level Analysis of Bone Cement Augmentation: A Comparative Experimental and Finite Element Study

The representation of cement–augmented bone in finite element (FE) models of vertebrae following vertebroplasty remains a challenge, and the methods of the model validation are limited. The aim of this study was to create specimen-specific FE models of cement–augmented synthetic bone at the microscopic level, and to develop a new methodology to validate these models. An open cell polyurethane foam was used reduce drying effects and because of its similar structure to osteoporotic trabecular bone. Cylindrical specimens of the foam were augmented with PMMA cement. Each specimen was loaded to three levels of compression inside a micro-computed tomography (μCT) scanner and imaged both before compression and in each of the loaded states. Micro-FE models were generated from the unloaded μCT images and displacements applied to match measurements taken from the images. A morphological comparison between the FE-predicted trabecular deformations and the corresponding experimental measurements was developed to validate the accuracy of the FE model. The predicted deformation was found to be accurate (less than 12% error) in the elastic region. This method can now be used to evaluate real bone and different types of bone cements for different clinical situations.

Synthesis and characterization of hydroxyapatite nanocrystal and gelatin doped with Zn2+ and cross linked by glutaraldehyde

Different nanocrystals of hydroxyapatite-[HAp]-gelatin [GEL], HAp/GEL/Glutaraldehyde (GA), HAp/GEL/Zn and HAp/GEL/GA/Zn were prepared using the biomimetic process. The nanocrystals were characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and X-ray diffraction analysis (XRD). The FT-IR spectra of HAp/GEL nanocrystal materials are similar to the spectrum of real bone. Nanocrystals show (002), (222), (211), and (112) planes, which confirm formation of hydroxyapatite phase. Lattice parameters from X-ray diffraction spectra showed that the metal cation was incorporated into the hydroxyapatite structure and has substituted for calcium in the HAp crystal structure and all of the doped HAp formulations were biphasic and crystalline. The hydroxyapatite/gelatin/zinc (HAp/GEL/Zn) composite sintered in 900°C demonstrated that the c-axes of HAp nanocrystals were regularly aligned along collagen fibers. Key words: Hydroxyapatite, Nanocomposite, Zinc.

Adaptive diffuse domain approach for calculating mechanically induced deformation of trabecular bone

Remodelling of trabecular bone is essentially affected by the mechanical load of the trabeculae. Mathematical modelling and simulation of the remodelling process have to include time-consuming calculations of the displacement field within the complex trabecular structure under loading. We present an adaptive diffuse domain approach for calculating the elastic bone deformation based on micro computer tomogram data of real trabecular bone structures and compared it with a conventional voxel-based finite element method. In addition to allowing for higher computational efficiency, the adaptive approach is characterised by a very smooth representation of the bone surface, which suggests that this approach would be suitable as a basis for future simulations of bone resorption and formation processes within the trabecular structure.

Tuning the Biomineralization Process for Controlling the Nucleation and Oriented Growth of Ca–P Crystals onto Functionalized Carbon Nanotubes

Herein we present a biosynthetic approach for the control of the nucleation and oriented growth of Ca–P crystals onto carbon nanotubes. This method based on the adequate modification of a biomimetic process allows the Ca–P growth from amorphous to crystalline phases. Interestingly, carbon nanotube walls have been shown to drive the growth orientation of the inorganic crystals. Furthermore, the growth of these Ca–P crystals occurs from a Ca-rich disorder interface, which is formed on carbon nanotubes during the first incubation steps. These findings are critical and have shown the potential of carbon nanotubes for the production of superior Ca–P structures to mimic the real bone properties.

Evidence Based Development of a Novel Lateral Fibula Plate (VariAx Fibula) Using a Real CT Bone Data Based Optimization Process During Device Development

Development of novel implants in orthopaedic trauma surgery is based on limited datasets of cadaver trials or artificial bone models. A method has been developed whereby implants can be constructed in an evidence based method founded on a large anatomic database consisting of more than 2.000 datasets of bones extracted from CT scans. The aim of this study was the development and clinical application of an anatomically pre-contoured plate for the treatment of distal fibular fractures based on the anatomical database.48 Caucasian and Asian bone models (left and right) from the database were used for the preliminary optimization process and validation of the fibula plate. The implant was constructed to fit bilaterally in a lateral position of the fibula. Then a biomechanical comparison of the designed implant to the current gold standard in the treatment of distal fibular fractures (locking 1/3 tubular plate) was conducted. Finally, a clinical surveillance study to evaluate the grade of implant fit achieved was performed. The results showed that with a virtual anatomic database it was possible to design a fibula plate with an optimized fit for a large proportion of the population. Biomechanical testing showed the novel fibula plate to be superior to 1/3 tubular plates in 4-point bending tests. The clinical application showed a very high degree of primary implant fit. Only in a small minority of cases further intra-operative implant bending was necessary. Therefore, the goal to develop an implant for the treatment of distal fibular fractures based on the evidence of a large anatomical database could be attained. Biomechanical testing showed good results regarding the stability and the clinical application confirmed the high grade of anatomical fit.