Real Bone Research Articles

Optimal internal architectures of femoral bone based on relaxation by homogenization and isotropic material design

The influence of the loading conditions on the trabecular architecture of a femur is investigated by using topology optimization methods. The response of the bone to physiological loads results in changes of the internal architecture of bone, reflected by a modification of internal effective density and mechanical properties. The homogenization based optimization model is developed for predicting optimal bone density distribution, wherein bone tissue is assumed to be a composite material consisting of a mixture of material and void. The homogenization scheme treats the geometric parameters of the microstructures and their orientation as design variables and homogenizes the properties in that microstructure, which is generally anisotropic. The penalization of the optimal material density then leads to a classical optimal structure which consists of regions with bone material and regions without bone material. The IMD (Isotropic Material Design) approach is next applied to determine the optimal elasticity tensor in terms of the bulk and shear moduli for the present loading applied to the femoral bone sample. IMD is able to provide both the external shape and topology together with the optimal layout of the isotropic moduli. Both topology optimization methods appear to be complementary. Simulations of the internal bone architecture of the human proximal femur results in a density distribution pattern with good consistency with that of the real bone.

Prediction of apparent properties with uncertain material parameters using high‐order fictitious domain methods and PGD model reduction

SummaryThis contribution presents a numerical strategy to evaluate the effective properties of image‐based microstructures in the case of random material properties. The method relies on three points: (1) a high‐order fictitious domain method; (2) an accurate spectral stochastic model; and (3) an efficient model‐reduction method based on the proper generalized decomposition in order to decrease the computational cost introduced by the stochastic model. A feedback procedure is proposed for an automatic estimation of the random effective properties with a given confidence. Numerical verifications highlight the convergence properties of the method for both deterministic and stochastic models. The method is finally applied to a real 3D bone microstructure where the empirical probability density function of the effective behaviour could be obtained. Copyright © 2016 John Wiley & Sons, Ltd.

MRI-compatible bone phantom for evaluating ultrasonic thermal exposures

ObjectiveThe goal of the proposed study was the development of a magnetic resonance imaging (MRI) compatible bone phantom suitable for evaluating focused ultrasound protocols. Materials and methodsHigh resolution CT images were used to segment femur bone. The segmented model was manufactured with (Acrylonitrile Butadiene Styrene) ABS plastic using a 3-D printer. The surrounding skeletal muscle tissue was mimicked using an agar–silica–evaporated milk gel (2% w/v–2% w/v–40% v/v). MR thermometry was used to evaluate the exposures of the bone phantom to focused ultrasound. ResultsThe estimated agar–silica–evaporated milk gel’s T1 and T2 relaxation times in a 1.5T magnetic field were 776ms and 66ms respectively. MR thermometry maps indicated increased temperature adjacent to the bone, which was also shown in situations of real bone/tissue interfaces. ConclusionDue to growing interest of using MRI guided Focused Ultrasound Surgery (MRgFUS) in palliating bone cancer patients at terminal stages of the disease, the proposed bone phantom can be utilized as a very useful tool for evaluating ultrasonic protocols, thus minimizing the need for animal models. The estimated temperature measured and its distribution near the bone phantom/agar interface which was similar to temperatures recorded in real bone ablation with FUS, confirmed the phantom’s functionality.

Biomechanical competence of six different bone screws for reconstructive surgery in three different transplants: Fibular, iliac crest, scapular and artificial bone.

The goal of this study was to determine a combination of screw and transplantation type that offers optimal primary stability for reconstructive surgery. Fibular, iliac crest, and scapular transplants were tested along with artificial bone substrate. Six different kinds of bone screws (Medartis(©)) were compared, each type utilized with one of six specimens from human transplants (n=6). Controlled screw-in-tests were performed and the required torque was protocolled. Subsequently, pull-out-tests were executed to determine the retention forces. The artificial bone substitute material showed significantly higher retention forces than real bone samples. The self-drilling screws achieved the significantly highest retention values in the synthetic bone substitute material. Cancellous screws achieved the highest retention in the fibular transplants, while self-drilling and cancellous screws demonstrated better retention than cortical screws in the iliac crest. In the scapular graft, no significant differences were found between the screw types. In comparison to the human transplant types, the cortical screws showed the significantly highest values in the fibula and the lowest values in the iliac crest. The best retention was found in the combination of cancellous screws with fibular graft (514.8N+-252.3N). For the flat bones (i.e., scapular and illiac crest) we recommend the cancellous screws.

Relationship between sample volumes and modulus of human vertebral trabecular bone in micro-finite element analysis

Micro-finite element (μFE) models have been widely used to assess the biomechanical properties of trabecular bone. How to choose a proper sample volume of trabecular bone, which could predict the real bone biomechanical properties and reduce the calculation time, was an interesting problem. Therefore, the purpose of this study was to investigate the relationship between different sample volumes and apparent elastic modulus (E) calculated from μFE model. 5 Human lumbar vertebral bodies (L1–L5) were scanned by micro-CT. Cubic concentric samples of different lengths were constructed as the experimental groups and the largest possible volumes of interest (VOI) were constructed as the control group. A direct voxel-to-element approach was used to generate μFE models and steel layers were added to the superior and inferior surface to mimic axial compression tests. A 1% axial strain was prescribed to the top surface of the model to obtain the E values. ANOVA tests were performed to compare the E values from the different VOIs against that of the control group. Nonlinear function curve fitting was performed to study the relationship between volumes and E values. The larger cubic VOI included more nodes and elements, and more CPU times were needed for calculations. E values showed a descending tendency as the length of cubic VOI decreased. When the volume of VOI was smaller than (7.34mm3), E values were significantly different from the control group. The fit function showed that E values approached an asymptotic values with increasing length of VOI. Our study demonstrated that apparent elastic modulus calculated from μFE models were affected by the sample volumes. There was a descending tendency of E values as the length of cubic VOI decreased. Sample volume which was not smaller than (7.34mm3) was efficient enough and timesaving for the calculation of E.

3D Skull Reconstruction with Selective Laser Sintering for Endoscopic Cranial Base Surgical Simulation and Training

Introduction: The training of surgeons is not dissimilar to that of pilots. Each profession has a responsibility to achieve a minimum safety standard and technical proficiency. This in most instances may only be achieved by many hours of experience, as well as practicing in mock or simulated emergency scenarios. Each quality airline provides its pilots with regular simulator events to train for particular emergency scenarios as well as simulator certification requirements. Surgeons have no such training requirement. Since there is no formal assessment of surgical skills for board and state licensure, surgeons are expected to self-regulate their own training. As advancements in medicine are made, surgeons are expected to know more and to be able to perform more types of procedures. In the USA, increasing restrictions on residency work hours are adding a new hurdle to surgical training. Restrictions on resident work hours means that many residents will not have optimum operating experience once they graduate from residency. For this reason, just as pilots spend hundreds of hours training in simulation suites, surgeons may also augment and complement their technical skills with simulation based training. In fields such as neurosurgery or otolaryngology, the endoscope is used in minimally invasive surgery. Junior residents may not have adequate exposure to this as their time practicing with endoscopes is limited by the dynamics of their residency program and case-load. By being able to train these residents in a realistic scenario, patient safety and quality of care can be improved. Data has shown that surgeons trained with simulation systems have shown improved parameters in the operating room such as technical profiency with the endoscope, as well as faster mean operating time. Materials and Methods: Current 3D printed training models on the market are prohibitively expensive and do not have tactile properties which accurately mimic real bone. Current methods also have difficulty in replicating the bony architecture of the skull base. We have developed a method of producing an anatomically accurate and realistic 3D printed skull with selective later sintering (SLS), using a material made from a polymer of polylactic acid (PLA) and limestone (Fig. 1). Our institute is developing the models around a suite of training features: various pathologies will be included, paired with real patient case histories and imaging for surgeons to review before they embark to practice on the skull model. Discussion: Methods for training surgeons in endoscopic surgery include virtual simulators, cadaveric training, and skull model based training. Virtual simulators are limited by the lack of tactile feedback, and cadaveric training is limited by ethical and cost issues. Training with skull based models has been shown to have comparative tactile feedback to the cadaveric model and actual surgery. Conclusion: Our institution has developed a method of manufacturing accurate 3D printed skull based models as part of an endoscopic surgery training suite.

The Effect of Reference Electrode Position in Cochlear Implants

This study aims to evaluate the increase in power of cochlear implants (CI) as the reference electrode (RE) position changes. Patients in whom it is necessary to use the full power of the device to achieve the desired stimulation levels, this strategy will ensure that stimulation capability is maximized. The variability in RE placement in the temporal bone has a measurable effect on the electrical current, impedance, and power consumption, and if the electrode position has a functional effect on the stimulation intensity. The following three approaches were used: 1) classical circuit analysis, 2) 2-dimensional numerical simulations, and 3) real temporal bone measurements using a purpose-made CI. The three approaches demonstrate a significant decrease in the current intensity and electrical resistance for distances that are closer to the intra-cochlear electrode. The results also demonstrate that to maintain a constant current, shorter distances require 33% less power. Reference electrode position during surgery can make significant differences in CI power consumption and threshold intensity, which allows a more powerful stimulation in complicated patients (i.e., those with otosclerosis). This study presents an attractive perspective to surgeons, as it shows a way to decrease consumption that might result in a longer battery life or more power to be devoted to coding strategy performance.

Stress Distribution on Short Implants at Maxillary Posterior Alveolar Bone Model With Different Bone-to-Implant Contact Ratio: Finite Element Analysis.

The aim of this study was to evaluate the stress distribution of the short dental implants and bone-to-implant contact ratios in the posterior maxilla using 3-dimensional (3D) finite element models. Two different 3D maxillary posterior bone segments were modeled. Group 1 was composed of a bone segment consisting of cortical bone and type IV cancellous bone with 100% bone-to-implant contact. Group 2 was composed of a bone segment consisting of cortical bone and type IV cancellous bone including spherical bone design and homogenous tubular hollow spaced structures with 30% spherical porosities and 70% bone-to-implant contact ratio. Four-millimeter-diameter and 5-mm-height dental implants were assumed to be osseointegrated and placed at the center of the segments. Lateral occlusal bite force (300 N) was applied at a 25° inclination to the implants long axis. The maximum von Mises stresses in cortical and cancellous bones and implant-abutment complex were calculated. The von Mises stress values on the implants and the cancellous bone around the implants of the 70% bone-to-implant contact group were almost 3 times higher compared with the values of the 100% bone-to-implant contact group. For clinical reality, use of the 70% model for finite element analysis simulation of the posterior maxilla region better represents real alveolar bone and the increased stress and strain distributions evaluated on the cortical and cancellous bone around the dental implants.

Experimental observation of ultrasound fast and slow waves through three-dimensional printed trabecular bone phantoms.

In this paper, ultrasound measurements of 1:1 scale three-dimensional (3D) printed trabecular bone phantoms are reported. The micro-structure of a trabecular horse bone sample was obtained via synchrotron x-ray microtomography, converted to a 3D binary data set, and successfully 3D-printed at scale 1:1. Ultrasound through-transmission experiments were also performed through a highly anisotropic version of this structure, obtained by elongating the digitized structure prior to 3D printing. As in real anisotropic trabecular bone, both the fast and slow waves were observed. This illustrates the potential of stereolithography and the relevance of such bone phantoms for the study of ultrasound propagation in bone.

THE TIBIAL APERTURE SURFACE ANALYSIS IN ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION PROCESS.

The tibial tunnel aperture in the anterior cruciate ligament reconstruction is usually analyzed as an ellipse, generated as an intersection between a tibial plateau and a tibial bone tunnel. The aim of this study is to show that the tibial tunnel aperture, which utilizes 3D tibial surface bone model, differs significantly from common computations which present the tibial tunnel anterior cruciate ligament aperture surface as an ellipse. An interactive program system was developed for the tibial tunnel aperture analysis which included the real tibia 3D surface bone model generated from a series of computed tomography images of ten male patients, their mean age being 25 years. In aperture calculation, the transverse drill angle of 10 degrees was used, whereas sagittal drill angles of 40 degrees, 50 degrees and 60 degrees were used with the drill-bit diameter set to 10 mm. The real 3D and 2D tibial tunnel aperture surface projection was calculated and compared with an ellipse. According to the calculations, generated 3D aperture surfaces were different for every patient even though the same drill parameters were used. For the sagittal drill angles of 40 degrees, 50 degrees and 60 degrees, the mean difference between the projected 3D and 2D area on the tibial plateau was 19.6 +/- 5.4%, 21.1 +/- 8.0% and 21.3 +/- 9.6%, respectively. The difference between the projected 3D area on the tibial plateau and ellipse surface was 54.8 +/- 16.3%, 39.6 +/- 10.4% and 25.0 +/- 8.0% for sagittal drill angles of 40 degrees, 50 degrees and 60 degrees, respectively. The tibial tunnel aperture surface area differs significantly from the ellipse surface area, which is commonly used in the anterior cruciate ligament reconstruction analysis. Inclusion of the 3D shape of the tibial attachment site in the preoperative anterior cruciate ligament reconstruction planning process can lead to a more precise individual anatomic anterior cruciate ligament reconstruction on the tibial bone. Both tibial aperture area generated in 3D and its projection on a tibial plateau are larger than the ellipse surface; therefore, individual characteristics of each patient have to be taken into consideration.

Virtual Methods Applied to Human Bones and Joints Re-Construction Used for Orthopedic Systems

In the first stage of research, real bone components were analyzed to determine the main visual geometric shapes. After that, it was used a CT or MRI device to get parallel sections of studied bone components. In the third stage, the images were transferred to a 2D CAD software like AutoCAD, where the outer and inner contours of the bone were approximated by polygonal lines composed of multiple segments. To obtain virtual bones was used a parametric CAD software that allows defining models with a high degree of difficulty. The contours were transferred to a 3D CAD software, which, step by step, each section was used to define each virtual component of bone. For some components, such as vertebrae, bones of the jaw, the skull bones, was used in a preliminary model consists of curves in parallel planes. Based on this model can be defined the main curves for the final virtual 3D solid model. Also, were defined innovative orthopedic metal components as tibia nail, plates and screws or prosthetic elements. Were defined simulations to determine the behavior of the new orthopedic models through FEA method.

Mechanical strength and mechano-compatibility of tissue-engineered bones

Current artificial bones made of metals and ceramics may be replaced around a decade after implantation due to its low durability, which is brought on by a large difference from the host bone in mechanical properties, i.e., low mechano-compatibility. On the other hand, tissue engineering could be a solution with regeneration of bone tissues from stem cells in vitro. However, there are still some problems to realize exactly the same mechanical properties as those of real bone. This paper introduces the technical background of bone tissue engineering and discusses possible methods for installation of mechano-compatibility into a regenerative bone. At the end, future directions toward the realization of ideal mechano-compatible regenerative bone are proposed.

Finite Element Analysis of Porous Medical Grade Cobalt Chromium Alloy Structures Produced by Selective Laser Melting

The recent introduction of selective laser melting (SLM) for the processing of medical grade cobalt chromium (CoCr) alloy has led to a complex shape fabrication of porous custom CoCr alloy implants with controlled porosity to meet the requirements of the anatomy and functions at the region of implantation. This paper discusses finite element (FE) analysis and mechanical characterization of porous medical grade CoCr alloy in cubical structures with volume based porosity ranging between 60% and 80% produced using SLM rapid manufacturing process. Analysis by FE is considered beneficial to predict the effective mechanical properties of the porous structures manufactured by SLM due to minimization of the need for expensive and time consuming physical testing. Cellular structures modelling for fabrication with Direct Metal Laser Sintering machine were designed to vary between 60% and 80% to study the effect of structural variation on mechanical properties of the cellular porous structure. ANSYS 14.0 FE modelling software was used to predict the effective elastic modulus of the samples and comparisons were made with the experimental data. FE results show that with the material properties in the functions of porosities, minimum mesh size of 0.2 mm for triangular shape mesh and boundary as well as load conditions as applied in this study, agreement in equivalent stress, strain and deformation with the experimental results can be achieved to some extent. The technique for FE in this study can be used to investigate stress distribution in three dimensional model of real bone.

An unusual oral squamous cell carcinoma of the mandible, mimicked inflammatory hyperplastic lesions: A case report

Abstract Squamous cell carcinoma (SCC) is the most common malignant tumors of oral cavity. The ratio of men to women is about 2: 1. Generally, it is admitted that 60% of carcinoma of the mandibular gingival are located in the posterior of premolars. Gingiva is one of the less common sites of oral squamous cell carcinoma (OSCC). Due to the variable clinical and behavioral presentations, it can easily be misdiagnosed as benign neoplasms or other inflammatory reactions. We encountered a 76-year-old woman with an unusual OSCC on the anterior mandibular ridge, imitating inflammatory hyperplastic (IH) lesion in May 2013. She complained that her denture was not seated suitably because of a mandibular lesion. After biopsy of the lesion, the surgeon noticed that real bone resorption was not visible in the x-ray image. Then histopathological evaluation detected the OSCC. Patient was referred to the CT-Scan and MRI. Three months later, the lesion recurred, enlarged and extended rapidly and she was emphasized the importance of a secondary surgery in a timely fashion.. She did not accept and then underwent radiotherapy and chemotherapy. In November 2013, the patient passed away because of the progress of OSCC. This case reminded us to keep the possibility of oral SCC in mind while examining every intra-oral lesion.

A novel additive manufacturing-based technique for developing bio-structures with conformal channels and encapsulated voids

A novel additive manufacturing-based technique for developing bio-structures with conformal channels and encapsulated voids. The network of macro-channels in the structure of cortical bone is crucial, particularly for nutrition. Therefore, a successful bone implant should simulate the real bone architecture by including such channels in its structure. The introduction of additive manufacturing (AM) techniques in the orthopedic implant industry brings the potential of producing customized bone implants that mimic the structure of real bone. However, the depowdering issue in the powder bed AM technique has hindered the creation of macro-sized channels in bone implants composed of biocompatible materials. In this study, we introduce a new method for manufacturing implants which is composed of titanium and includes networks of channels. This technique is primarily based on printing individual components of a sliced structure, followed by depowdering and assembling the components before the sintering process. This new technique has the potential to control the internal features of 3D printed structures. A set of comparative physical and mechanical tests were conducted to characterize the resulting structures. Experimental characterization results showed that the shear strength of the sample that was made by the new technique was reduced by 24%–30%, where the porosity was slightly lower (∼2%) than that of a comparable control sample. However, the new technique had no effect on the compressive strength of the structure.

A Hybrid Nonlinear ANC for Speech Recovery Using Both Bone- and Air-Conducted Measurements

<div class=""abs_img""> <img src=""[disp_template_path]/JRM/abst-image/00270005/08.jpg"" width=""300"" /> Denoising nonlinear filter</div> Speech recovery in the presence of very harsh noise is calling for R&D that take approaches different from those established to date, as the conventional systems and algorithms for speech denoising may suffer from serious performance degradation. In this paper, we propose a hybrid nonlinear adaptive noise canceller (ANC) to perform the speech enhancement task using both bone- and air-conducted measurements. In the proposed ANC, the bone-conducted speech serves as a reference signal while the air-conducted measurement with very large additive noise is adopted as a primary noise. A Volterra filter and a functional link artificial neural network (FLANN) are placed in parallel, forming a hybrid nonlinear ANC. Simulations using real bone- and air-conducted speech measurements are provided to demonstrate that the proposed system outperforms ANCs equipped with FIR filter or Volterra filter or FLANN alone. </span>

A novel method for production of foamy core@compact shell Ti6Al4V bone-like composite

This paper presents a novel method for fabrication of bone-like Ti6Al4V foamy core@compact shell composite for utilization as substitutive implant for cortical bone having porous core. Seven prototypes with core-diameters of 0, 6, 8, 10, 12, 14 and 16 mm surrounded by dense shells of respective thicknesses 8, 5, 4, 3, 2, 1 and 0 were produced by an innovative two-stage packing/compaction sintering method. Density, porosity, Young's modulus and compression strength of the prototypes depended on the core diameter. Mechanical strength and Young's modulus of 10@16 (10 mm core, 16 mm diameter prototypes) resembled that of the human ulna bone. Creation of foam at the center was achieved by carbamide powder space holder. Sintering potential model of porous spaces was a basis for heat treatment. Yield strength and Young's modulus of the prototypes ranged from 501 MPa to 46 GPa in the compact shells and 7 MPa to 2 GPa in the foamy cores of the composite samples. Final products contained 8–65% porosity with 1.45–2.84 g/cm3 theoretical density which were within the range of the real human bone.

Distraction osteogenesis device to estimate the axial stiffness of the callus in Vivo

Knowing the evolution of callus stiffness is very important in distraction osteogenesis and bone healing. It allows the characterization of the bone maturation process and the assessment of the moment to retire the fixator. A new distractor device that monitors the callus axial stiffness is presented in this study. It quantifies the callus stiffness during the bone transport process with some advantages over previous methods to assess stiffness during simple distraction and bone healing. This device avoids a misalignment between bone segments, uses real load conditions, monitors forces continuously, does not involve radiation for patients, and allows the study of the complete distraction process, i.e., the distraction and consolidation phases. The device was calibrated in vitro simulating different real bone load conditions depending on the stage of the process. The stiffness of the callus could be estimated for values between 4.2 N/mm and 9066.8 N/mm. The average relative error in measurements carried out in in vitro calibration tests was 7.8% during the distraction phase and 9.5% during the consolidation phase. These results improve the accuracy and increase the callus stiffness range of estimation with respect to other devices in the literature. In addition, the device was used successfully in vivo in a preliminary experiment.

MATERIALS SELECTION FOR HIP PROSTHESIS BY THE METHOD OF WEIGHTED PROPERTIES

Process of materials selection for an artificial part, which is planted in vivo, has been always a vital procedure. Production and construction requirements for implants would involve a wide variety of considerations from mechanical specifications to medical limitations. From mechanical point of view, it is desired the implant exhibits mechanical properties of the missing bone as close as possible to reduce the risk of failure and provide a high level of comfort to the patient. The most bolded medical trait that prostheses must possess is the quality of biocompatible being; meaning that, they have to be accepted by the body’s living organisms. In this paper, five common biocompatible materials as candidates for hip prostheses production namely, 316L St Steel (cold worked, ASTM F138), Co–28Cr–6Mo (cast, ASTM F75), Ti–6Al–4V (hot forged, ASTM F620), Zirconia (ceramic, 3Y-TZP) and Alumina (ceramic, ZTA) are selected and evaluated by the method of weighted properties, in order to narrow down the search to find the candidate which best fit the real bone’s mechanical traits. For the analysis, six attributes were considered and weighted against each other namely, elastic modulus, yield strength, tensile strength, fatigue strength, corrosion rate and density. From the results, alumina and stainless steel show highest performance indexes but as it is discussed, due to the importance of biocompatibility required in practical, materials ranked on position 4th and 5th which are respectively of cobalt and titanium alloys–although are less mechanically similar to the real bone, are the most desirable choices in the industry. It will be concluded that in the process of materials selection for implants,

Femoral cortical index: an indicator of poor bone quality in patient with hip fracture.

Osteoporosis is a common disease in elderly, characterized by poor bone quality as a result of alterations affecting trabecular bone. However, recent studies have described also an important role of alterations of cortical bone in the physiopathology of osteoporosis. Although dual-energy X-ray absorptiometry (DXA) is a valid method to assess bone mineral density, in the presence of comorbidities real bone fragility is unable to be evaluated. The number of hip fractures is rising, especially in people over 85 years old. The aim is to evaluate an alternative method so that it can indicate fracture risk, independent of bone mineral density (BMD). Femoral cortical index (FCI) assesses cortical bone stock using femur X-ray. A retrospective study has been conducted on 152 patients with hip fragility fractures. FCI has been calculated on fractured femur and on the opposite side. The presence of comorbidities, osteoporosis risk factors, vitamin D levels, and BMD have been analyzed for each patient. Average values of FCI have been 0.42 for fractured femurs and 0.48 at the opposite side with a statistically significant difference (p = 0.002). Patients with severe hypovitaminosis D had a minor FCI compared to those with moderate deficiency (0.41 vs. 0.46, p < 0.011). 42 patients (27.6%) with osteopenic or normal BMD have presented low values of FCI. A significant correlation among low values of FCI, comorbidities, severe hypovitaminosis D. and BMD in patients with hip fractures has been found. FCI could be a useful tool to evaluate bone fragility and to predict fracture risk even in the normal and osteopenic BMD patients.