Bone Failure Research Articles

Numerical modelling of cancellous bone damage using an orthotropic failure criterion and tissue elastic properties as a function of the mineral content and microporosity

Background and objective: Elastic and strength properties of lamellar tissue are essential to analyze the mechanical behaviour of bone at the meso- or macro-scale. Although many efforts have been made to model the architecture of cancellous bone, in general, isotropic elastic constants are assumed for tissue modelling, neglecting its non-isotropic behaviour. Therefore, isotropic damage laws are often used to estimate the bone failure. The main goals of this work are: (1) to present a new model for the estimation of the elastic properties of lamellar tissue which includes the bone mineral density (BMD) and the microporosity, (2) to address the numerical modelling of cancellous bone damage using an orthotropic failure criterion and a discrete damage mechanics analysis, including the novel approach for the tissue elastic properties aforementioned.Methods: Numerical homogenization has been used to estimate the elastic properties of lamellar bone considering BMD and microporosity. Microcomputed Tomography (μ-CT) scans have been performed to obtain the micro-finite element (μ-FE) model of cancellous bone from a vertebra of swine. In this model, lamellar tissue is orientated by considering a unidirectional layer pattern being the mineralized collagen fibrils aligned with the most representative geometrical feature of the trabeculae network. We have considered the Hashin’s failure criterion and the Material Property Degradation (MPDG) method for simulating the onset and evolution of bone damage.Results: The terms of the stiffness matrix for lamellar tissue are derived as functions of the BMD and microporosity at tissue scale. Results obtained for the apparent yield strain values agree with experimental values found in the literature. The influence of the damage parameters on the bone mechanics behaviour is also presented.Conclusions: Stiffness matrix of lamellar tissue depends on both BMD and microporosity. The new approach presented in this work enables to analyze the influence of the BMD and porosity on the mechanical response of bone. Lamellar tissue orientation has to be considered in the mechanical analysis of the cancellous bone. An orthotropic failure criterion can be used to analyze the bone failure onset instead of isotropic criteria. The elastic property degradation method is an efficient procedure to analyze the failure propagation in a 3D numerical model.

Effect of osteoporosis-related reduction in the mechanical properties of bone on the acetabular fracture during a sideways fall: A parametric finite element approach.

The incidence of acetabular fractures due to low-energy falls is increasing among the geriatric population. Studies have shown that several biomechanical factors such as body configuration, impact velocity, and trochanteric soft-tissue thickness contribute to the severity and type of acetabular fracture. The effect of reduction in apparent density and elastic modulus of bone as well as other bone mechanical properties due to osteoporosis on low-energy acetabular fractures has not been investigated. The current comprehensive finite element study aimed to study the effect of reduction in bone mechanical properties (trabecular, cortical, and trabecular + cortical) on the risk and type of acetabular fracture. Also, the effect of reduction in the mechanical properties of bone on the load-transferring mechanism within the pelvic girdle was examined. We observed that while the reduction in the mechanical properties of trabecular bone considerably affects the severity and area of trabecular bone failure, reduction in mechanical properties of cortical bone moderately influences both cortical and trabecular bone failure. The results also indicated that by reducing bone mechanical properties, the type of acetabular fracture turns from elementary to associated, which requires a more extensive intervention and rehabilitation period. Finally, we observed that the cortical bone plays a substantial role in load transfer, and by increasing reduction in the mechanical properties of cortical bone, a greater share of load is transmitted toward the pubic symphysis. This study increases our understanding of the effect of osteoporosis progression on the incidence of low-energy acetabular fractures. The osteoporosis-related reduction in the mechanical properties of cortical bone appears to affect both the cortical and trabecular bones. Also, during the extreme reduction in the mechanical properties of bone, the acetabular fracture type will be more complicated. Finally, during the final stages of osteoporosis (high reduction in mechanical properties of bone) a smaller share of impact load is transferred by impact-side hemipelvis to the sacrum, therefore, an osteoporotic pelvis might mitigate the risk of sacral fracture.

The role of systemic diseases and local conditions as risk factors.

The role of systemic diseases and local conditions as risk factors.

A review on experimental and numerical investigations of cortical bone fracture.

This paper comprehensively reviews the various experimental and numerical techniques, which were considered to determine the fracture characteristics of the cortical bone. This study also provides some recommendations along with the critical review, which would be beneficial for future research of fracture analysis of cortical bone. Cortical bone fractures due to sports activities, climbing, running, and engagement in transport or industrial accidents. Individuals having different diseases are also at high risk of cortical bone fracture. It has been observed that osteon orientation influences cortical bone fracture toughness and fracture mechanisms. Apart from this, recent studies indicate that fracture parameters of cortical bone also depend on many factors such as age, sex, temperature, osteoporosis, orientation, location, loading condition, strain rate, and storage facility, etc. The cortical bone regains its fracture toughness due to various toughening mechanisms. Owing to these factors, several experimental, clinical, and numerical investigations have been carried out to determine the fracture parameters of the cortical bone. Cortical bone is the dense outer surface of the bone and contributes to 80%-82% of the skeleton mass. Cortical bone experiences load far exceeding body weight due to muscle contraction and the dynamics of motion. It is very important to know the fracture pattern, direction of fracture, location of the fracture, and toughening mechanism of cortical bone. A basic understanding of the different factors that affect the fracture parameters and fracture mechanisms of the cortical bone is necessary to prevent the failure and fracture of cortical bone. This review has summarized the advancement considered in the various experimental techniques and numerical methods to get complete information about the fracture mechanisms of cortical bone.

Can an Isotropic Crushable Foam Model Predict Failure of a Whole Bone?

Can an Isotropic Crushable Foam Model Predict Failure of a Whole Bone?

Alveolar distraction osteogenesis: possible complications and methods of their treatment

The aim of the study. Analysis of emerging complications during the method of alveolar distraction osteogenesis in patients with jaw defects. A retrospective analysis of foreign and domestic literature was carried out. A systematic literary search was carried out in the electronic bibliographic databases Web of Science (for foreign articles) and Elibrary and Dissercat (for domestic). In the period from 2005 to 2019 in the clinic of the Department of Maxillofacial and Plastic Surgery of the Moscow State Medical University. Evdokimov conducted an examination and comprehensive treatment of 490 patients with primary and secondary adentia of the upper and lower jaws, accompanied by a significant deficiency of bone tissue of the alveolar ridge vertically. A comprehensive dental rehabilitation of patients with jaw defects by the method of distraction osteogenesis was carried out. The most common complications are: exposure of the fixation modules of the distraction apparatus - 24% of cases, failure of bone regenerate - 13%, inflammatory phenomena - 13%, displacement of the distraction vector - 43%, paresthesia - 7%. Based on our analysis of the identified complications during the distraction osteogenesis method, it was found that these complications are not critical in the treatment of patients with jaw bone deficiency and do not jeopardize the success of rehabilitation. With diagnosis and timely approach to treatment, complications are avoidable.

An investigation into the properties of 3D printed Ti6Al4V FCC lattice structures with different strut thicknesses

Metal additive manufacturing of titanium and its alloys can produce complicated geometries cost-effectively while maintaining biocompatibility. It is known that the material property differences between bone and Ti6Al4V cause stress shielding, leading to bone failure around the implant. Using lattice structures is effective at reducing elastic modulus while improving osteointegration. However, it is important first to characterise the as-printed material to investigate the effects of lattice structures on the bulk material properties. Understanding the microstructure, porosity, and related mechanical properties can discern the bulk material properties of the unit cell. The microstructure of printed samples was found to be martensitic. The printed samples contained porosity with strut thickness deviations ranging from the design from 44.29 % (t = 0.50 mm) to 28.43 % (t = 1 mm). It was found that the high amount of porosity resulted in considerable variation in compression material properties.

Parametric Study of Hip Fracture Risk Using QCT-Based Finite Element Analysis

Various parameters such as age, height, weight, and body mass index (BMI) influence the hip fracture risk in the elderly which is the most common injury during the sideways fall. This paper presents a parametric study of hip fracture risk based on the gender, age, height, weight, and BMI of subjects using the subject-specific QCT-based finite element modelling and simulation of single-leg stance and sideways fall loadings. Hip fracture risk is estimated using the strain energy failure criterion as a combination of bone stresses and strains leading to more accurate and reasonable results based on the bone failure mechanism. Understanding the effects of various parameters on hip fracture risk can help to prescribe more accurate preventive and treatment plans for a community based on the gender, age, height, weight, and BMI of the population. Results of this study show an increase in hip fracture risk with the increase of age, body height, weight, and BMI in both women and men under the single-leg stance and the sideways fall configurations.

Subject specific finite element modelling of periprosthetic femoral fractures in different load cases

Periprosthetic femoral fractures (PFF) around total hip replacements are one of the biggest challenges for orthopaedic surgeons. To understand the risk factors and formation of these fractures, the development of a reliable finite element (FE) model incorporating bone failure is essential. Due to the anisotropic and complex hierarchical structure of bone, the mechanical behaviour under large strains is difficult to predict. In this study, a state-of-the-art subject specific FE modelling technique for bone is utilised to generate and investigate PFF. A bilinear constitutive law is applied to bone tissue in subject specific FE models of five human femurs which are virtually implanted with a straight hip stem to numerically analyse PFF. The material parameters of the models are expressed as a function of bone ash density and mapped node wise to the FE mesh. In this way the subject specific, heterogeneous structure of bone is mimicked. For material mapping of the parameters, computed tomography (CT) images of the original fresh-frozen femurs are used. Periprosthetic fractures are generated by deleting elements on the basis of a critical plastic strain failure criterion. The models are analysed under physiological and clinically relevant conditions in two different load cases re-enacting stumbling and a sideways fall on the hip. The results of the analyses are quantified with experimental data from previous work. With regard to fracture pattern, stiffness and failure load the simulations of the load case stumbling delivered the most stable and accurate results. In general, mapping of material properties was found to be an appropriate way to reproduce PFF with finite element models.

Biomechanical Performance of BoneHelix® Compared with Elastic Stable Intramedullary Nailing (ESIN) in a Pediatric Tibia Fracture Model.

Tibial shaft fractures are common injuries in the pediatric and adolescent populations. Elastic stable intramedullary nailing (ESIN) is the treatment of choice for cases that require surgical stabilization. A new intramedullary device, BoneHelix® (BH), may be an alternative for use with fractures that cannot be satisfactorily stabilized with ESIN. This study aimed to assess the biomechanical performance of BH compared with ESIN in a porcine tibia fracture model, observing cyclic fatigue and load to failure. Computed tomography was used to monitor the implant position and to rule out unintended damage. No implant or bone failure occurred during the fatigue testing. An increase in the cumulative plastic displacement was observed in both test groups over the loading cycles applied. Both implant–bone constructs displayed a trend toward closure of the osteotomy gap. During the load-to-failure test, the average loads at failure in specimens instrumented with ESIN and BH were 5364 N (±723) and 4350 N (±893), respectively, which were not statistically significant (p = 0.11). The values of both groups were two to three times higher than the estimated maximal load (2000 N) during physiological weight bearing. The biomechanical results thus indicate equivalent performance and stability by the implants tested.

Arthroscopy Limits on Anterior Shoulder Instability.

Much is discussed about the limits of the treatment of anterior shoulder instability by arthroscopy. The advance in understanding the biomechanical repercussions of bipolar lesions on shoulder stability, as well as in the identification of factors related to the higher risk of recurrence have helped us to define, more accurately, the limits of arthroscopic repair.We emphasize the importance of differentiation between glenoid bone loss due to erosion (GBLE) and glenoid edge fractures, because the prognosis of treatment differs between these forms of glenoid bone failure. In this context, we understand that there are three types of bone failure: a) bone Bankart (fracture); b) combined; and c) glenoid bone loss due to anterior erosion (GBLE), and we will address the suggested treatment options in each situation. Until recently, the choice of surgical method was basically made by the degree of bone involvement. With the evolution of knowledge, the biomechanics of bipolar lesions and the concept of glenoid track , the cutoff point of critical injury, has been altered with a downward trend. In addition to bone failures or losses, other variables were added and made the decision more complex, but a little more objective. The present update article aims to make a brief review of the anatomy with the main lesions found in instability; to address important details in arthroscopic surgical technique, especially in complex cases, and to bring current evidence on the issues of greatest divergence, seeking to guide the surgeon in decision making.

The biomechanical profile of an osseo-integrated rectangular block implant: A pilot in vivo experimental study.

A novel implant design, the rectangular block implant (RBI), was investigated as a possible solution to the restoration of the posterior resorbed ridge. To maximally load test the osseo-integrated RBI in shear and tensile loads and relate these findings to known human masticatory loads as biomechanical proof of the study concept. Twelve RBIs were design-manufactured and placed into posterior mandibular saddles in 3mature greyhound dogs.-2 per left and right. After 12weeks of healing, osseo-integration was confirmed using resonance frequency analysis (RFA) and wrench torque tests. Three bone blocks each with two RBIs were dissected and mounted in acrylic. Micro-computerized tomography (μ-CT) was performed to assess bone to implant contact (BIC), and load analysis was performed using a Universal Test System. Three force applications were conducted until failure: pull-out (tensile), buccal push from the lingual (shear) and distal push from the mesial (shear). The osteotomy sites were examined using light magnification and scanning electron microscopy (SEM). Pull-out, buccal and distal force failures occurred at differing levels. Post-detachment sites showed complex patterns of bone failure, including trabecular and cortical fracture, as well as shearing at varying distances from the BIC. Interfacial shear strength was calculated at 14.4MPa. The osseo-integrated RBIs were able to withstand simulations of the demanding axially, bucco-lingually and mesio-distally oriented biomechanical challenges of the posterior saddle, under conditions of reduced bone volume. These values exceeded equivalent force components of maximal masticatory loads in humans.

Computational homogenisation based extraction of transverse tensile cohesive responses of cortical bone tissue.

The numerical assessment of fracture properties of cortical bone is important in providing suggestions on patient-specific clinical treatments. We present a generic finite element modelling framework incorporating computational fracture approaches and computational homogenisation techniques. Finite element computations for statistical volume elements (SVEs) at the microscale are performed for different sizes with random osteon packing with a fixed volume fraction. These SVEs are loaded in the transverse direction under tension. The minimal SVE size in terms of ensuring a representative effective cohesive law is suggested to be 0.6 mm. Since cement lines as weak interfaces play a key role in bone fracture, the effects of their fracture properties on the effective fracture strength and toughness are investigated. The extracted effective fracture properties can be used as homogenised inputs to a discrete crack simulation at macroscopic or structural scale. The extrinsic toughening mechanisms observed in the SVE models are discussed with a comparison against experimental observations from the literature, giving beneficial insights to cortical bone failure.

Development of castor polyurethane scaffold (Ricinus communis L.) and its effect with stem cells for bone repair in an osteoporosis model

The development of ‘smart’ scaffolds has achieved notoriety among current prospects for bone repair, especially for chronic osteopathy, such as osteoporosis. Millions of individuals in the world suffer from poor bone healing due to osteoporosis. The objective of this work was to produce and characterize castor polyurethane (PU) scaffolds (Ricinus communis L.) and evaluate its in vitro biocompatibility with stem cells and osteoinductive effect in vivo on bone failures in a leporid model of osteoporosis. The material was characterized using Fourier-transform infrared spectroscopy, thermogravimetric analysis, SEM, and porosity analysis. Then, the biocompatibility was assessed by adhesion using SEM and cytotoxicity in a 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2H-tetrazolium assay. The osteoinductive effect in vivo was determined in bone defects in rabbit tibias (Oryctolagus cuniculus) submitted to castor PU scaffold, castor PU scaffold associated with stem cells, and negative control, after four and eight weeks, evaluated by computed microtomography and histopathology. The scaffolds were porous, with an average pore size of 209.5 ± 98.2 µm, absence of cytotoxicity, and positive cell adhesiveness in vitro. All the animals presented osteoporosis, characterized by multifocal osteoblastic inactivity and areas of mild fibrosis. There were no statistical differences between these treatments in the fourth week of treatment. In the eighth week, the treatment with castor PU scaffold alone induced more significant bone formation when compared to the other groups, followed by treatment with an association between castor PU scaffold and stem cells. The castor PU scaffold was harmless to cell culture, favoring cell adhesiveness and proliferation, in addition to inducing bone neoformation in osteoporotic rabbits.

Influence of Screw-Hole Defect Size on the Biomechanical Properties of Feline Femora in an Ex Vivo Model.

The study aims to evaluate the biomechanical properties of feline femora with craniocaudal screw-hole defects of increasing diameter, subjected to three-point bending and torsion to failure at two different loading rates. Eighty femoral pairs were harvested from adult cat cadavers. For each bending and torsional experiment, there were five groups (n = 8 pairs) of increasing craniocaudal screw-hole defects (intact, 1.5 mm, 2.0 mm, 2.4 mm, 2.7mm). Mid-diaphyseal bicortical defects were created with an appropriate pilot drill-hole and tapped accordingly. Left and right femora of each pair were randomly assigned to a destructive loading protocol at low (10 mm/min; 0.5 degrees/s) or high rates (3,000 mm/min; 90 degrees/s) respectively. Stiffness, load/torque-to-failure, energy-to-failure and fracture morphology were recorded. Defect size to bone diameter ratio was significantly different between defect groups within bending and torsional experiments respectively (intact [0%; 0%], 1.5 mm [17.8%; 17.1%], 2.0 mm [22.8%; 23.5%], 2.4 mm [27.8%; 27.6%], 2.7 mm [31.1%; 32.4%]) (p < 0.001). No significant differences in stiffness and load/torque-to-failure were noted with increasing deficit sizes in all loading conditions. Screw-hole (2.7 mm) defects up to 33% bone diameter had a maximum of 20% reduction in bending and torsional strength compared with intact bone at both loading rates. Stiffness and load/torque-to-failure in both bending and torsion were increased in bones subjected to higher loading rates (p < 0.001). Screw-hole defects up to 2.7 mm did not significantly reduce feline bone failure properties in this ex vivo femoral study. These findings support current screw-size selection guidelines of up to 33% bone diameter as appropriate for use in feline fracture osteosynthesis.

Biomechanics of the Femoral Head Cartilage and Subchondral Trabecular Bone in Osteoporotic and Osteopenic Fractures

This study aimed to investigate the relationship between the micro structural properties of the subchondral trabecular bone (STB) and the macro mechanical properties of the articular cartilage (AC) in patients with osteoporotic (OP) and osteopenic (OPE) fractures. Sixteen femoral head samples (OP;OPE, n = 8 each) were obtained from female patients who underwent hip hemiarthroplasty. STB and AC specimens were harvested from those heads. Bone specimens were scanned using µ-CT to determine the micro structural properties. In-situ nondestructive compressive tests were performed for the cartilages to obtain elastic properties. The finite element technique was implemented on STB models created from µ-CT data to compute apparent elastic modulus. In addition, dynamic cyclic destructive tests were performed on STB and AC specimens to assess failure cycles. The results demonstrated that STB specimens in OPE group have more interconnected structure and higher cyclic dynamic strength than those in OP group. Furthermore, bone mineral density, failure cycle, and trabecular number of STB were positively correlated with the cartilage failure cycle, which indicates that STB alteration may affect the macroscopic mechanical properties of AC. The findings suggest that STB loss correlates with a decrease in cartilage strength and that improving of bone quality may prevent cartilage weakness.

Comparision of the Stress Distribution Between High-Heeled and Flat Shoes on The First Metatarsal Bone

The aim of this study is to examine the effects of the wearing high-heeled shoes (HHS) by comparing the wearing the flat shoes on the first metatarsal bone using the finite element method. The first metatarsal bone is modeled from computerized tomography (CT) image as 3D and imported to ANSYS Workbench Software. Body weight (BW) and muscle forces were applied to the first metatarsal bone. The bone was fixed at the proximal region of the bone for the boundary conditions. Three evaluation criteria were examined for the results as the stresses, the total deformations and the strain values on the bone. The stress and strain distributions of the bone were evaluated for the bone failure. The deformation of the bone were evaluated for the bone stabilitiy. As a result, the wearing HHS increases the stress values on the first metatarsal bone approximately %54 compared to the flat shoes. The strain values showed that the bone crack or failure was not occured. The deformation of the bone was increased when wearing the HHS shoes. The conclusion of the study is that the wearing HHS negatively affects the first metatarsal bone. Hence, the frequency of the wearing HHS in daily life should be reduced and heeled shoe designs should be made taking into account the stresses occured on the bone.

Experimental investigation of the effect of bone surface macro-groove preparation on the strength of bone-cement interface

This study aims to determine the effect of bone surface macro-groove preparation on the strength of the bone-cement interface. Polymethyl methacrylate (PMMA) was considered as bone cement, and cancellous bone was extracted from the bovine femur to prepare the bone-cement specimen. A total of seventy-eight (78) bone-cement specimens were prepared, which consist of different shapes of the groove, size of groove, number of grooves, and distance between two grooves (pitch distance) and tested using the universal testing machine (UTM) by applying mode-II and mixed-mode (mode-I + mode-II) loading. Rectangular and semi-circular shape grooves were considered to determine the effect of the shape of the groove on the strength of the bone-cement interface. For semi-circular grooves, single and double semi-circular grooves with two different sizes (4 mm and 6 mm) were considered. In the double semi-circular groove, apart from two different sizes (4 mm and 6 mm), two different pitch distances (8 mm and 9 mm) between two grooves were considered to understand the effect of pitch distance on bone-cement interfacial strength. Bone-cement interfacial strength was measured in terms of the maximum load, energy absorbed before failure, and strength of the bone-cement specimen. Results indicated that rectangular grooves performed better in terms of strength; however, local cancellous bone failure was observed, which restricted the use of rectangular grooves for bone-cement fixation. Maximum load, energy absorbed before failure, and strength of the bone-cement specimen were found to be increased as the size, pitch distance, and the numbers of the groove increases. Results of our study also indicated that a single large groove at the bone-cement interface was found to be more effective than the two small grooves to increase the strength of the bone-cement interface. Apart from these, pitch distance also plays an important role in increasing the strength of the bone-cement interface.

Bringing Mechanical Context to Image-Based Measurements of Bone Integrity.

Image-based measurements of bone integrity are used to estimate failure properties and clinical fracture risk. This paper (1) reviews recent imaging studies that have enhanced our understanding of the mechanical pathways to bone fracture and (2) discusses the influence that inter-individual differences in image-based measurements may have on the clinical assessment of fracture risk RECENT FINDINGS: Increased tissue mineralization is associated with improved bone strength but reduced fracture toughness. Trabecular architecture that is important for fatigue resistance is less important for bone strength. The influence of porosity on bone failure properties is heavily dependent on pore location and size. The interaction of various characteristics, such as bone area and mineral content, can further complicate their influence on bone failure properties. What is beneficial for bone strength is not always beneficial for bone toughness or fatigue resistance. Additionally, given the large amount of imaging data that is clinically available, there is a need to develop effective translational strategies to better interpret non-invasive measurements of bone integrity.

Influence of osteoporosis on the compressive properties of femoral cancellous bone and its dependence on various density parameters

Data collection of mechanical parameters from compressive tests play a fundamental role in FE modelling of bone tissues or the developing and designing of bone implants, especially referring to osteoporosis or other forms of bone loss. A total of 43 cylindrical samples (Ø8 × 16 mm) were taken from 43 freshly frozen proximal femora using a tenon cutter. All femora underwent BMD measurement and additionally apparent- and relative- and bulk density (ρapp, ρr, ρb) were determined using samples bordering the compressive specimen on the proximal and distal regions. All samples were classified as "normal", "osteopenia" and "osteoporosis" based on the DEXA measurements. Distal apparent density was most suitable for predicting bone strength and BMD. One novel aspect is the examination of the plateau stress as it describes the stress at which the failure of spongious bone progresses. No significant differences in mechanical properties (compressive modulus E; compressive stress σmax and plateau stress σp) were found between osteopenic and osteoporotic bone. The results suggest that already in the case of a known osteopenia, actions should be taken as they are applied in the case of osteoporosis A review of the literature regarding extraction and testing methods illustrates the urgent need for standardized biomechanical compressive material testing.