- Severe Neurovascular Compromise Associated with Plastic Deformation of Ulna Elastic Nail Following Forearm Re-fracture. [Case Reports]
- CCureus 2019 Mar 28; 11(3):e4340
- We present a case of periprosthetic re-fracture of the forearm in a child with previous intramedullary elastic nailing of the ulna and plate fixation of the radius for a both-bone forearm fracture. I…
We present a case of periprosthetic re-fracture of the forearm in a child with previous intramedullary elastic nailing of the ulna and plate fixation of the radius for a both-bone forearm fracture. In-situ plastic deformation of the ulna elastic nail resulted in persistent angulation and subsequent severe neurovascular compromise. The angulation was resistant to emergent attempts at closed manipulation and therefore nail removal, open reduction, and internal fixation were performed. At final follow-up, fracture union was demonstrated and there was no residual neurological deficit.
- Pneumosinus Dilatans frontalis: a case of incidental autopsy diagnosis. [Journal Article]
- FSForensic Sci Med Pathol 2019 Jun 03
- Pneumosinus Dilatans Frontalis (PDF) is a rare pathologic condition characterized by expansion and hyper aeration of the frontal sinuses. This abnormality has been described in otolaryngology, ophtha…
Pneumosinus Dilatans Frontalis (PDF) is a rare pathologic condition characterized by expansion and hyper aeration of the frontal sinuses. This abnormality has been described in otolaryngology, ophthalmology, neurology, and radiology journals, while only a few autopsy studies are reported in the English literature. The etiology of this condition remains unclear, although multiple theories have been proposed. Clinically, PDF is often an asymptomatic condition, but it can lead to significant bone deformation with esthetic complaints, and even severe associated neurological deficits. In the following case report, a 20-year-old Caucasian male committed suicide by asphyxia due to plastic bag suffocation combined with a vitiated atmosphere as a consequence of helium inhalation. At postmortem an abnormal expansion of the frontal sinuses was detected, involving the frontal bone just above the orbits. The defect showed a multiloculated appearance in the sinus cavities. An incidental diagnosis of PDF was made. A description of the findings and a hypothesis of the clinical relevance of PDF in the reported case are presented.
- Characterization of mechanical and microstructural properties of constrained groove pressed nitinol shape memory alloy for biomedical applications. [Journal Article]
- MSMater Sci Eng C Mater Biol Appl 2019; 102:730-742
- Among shape memory alloys, nitinol alloy is biocompatible in nature and thus widely used in bone tissue engineering, stents, dental and orthopedic implants. To improve mechanical properties and exten…
Among shape memory alloys, nitinol alloy is biocompatible in nature and thus widely used in bone tissue engineering, stents, dental and orthopedic implants. To improve mechanical properties and extend its application window, in this paper, the Ni50.5Ti49.5 (nitinol) sheets are processed by constrained groove pressing (CGP) process, which is one of the effective severe plastic deformation (SPD) techniques for refining microstructure and enhancing mechanical properties in sheet metals. The microstructure and X-ray diffraction studies of CGPed sheets show uniform grain refinement and increase in martensitic variant. Based on tensile and micro-hardness tests on water quenched (WQ) and CGPed nitinol alloy, the results show about up to 2.5 times increment in ultimate tensile strength and yield strength, significant enhancement in micro-hardness and change in strain hardening behavior. For characterizing the strain hardening behavior, Holloman and Voce models have been determined to have strong correlation with the experimental data for WQ and CGPed nitinol alloy respectively. Thus, nitinol alloy after CGP exhibits grain refinement and microstructural evolution, showing an increase in stress induced martensite phase which indicates superior mechanical properties such as high strength, uniform deformation regime and microhardness. These enhancements will help in reduction of other supporting materials generally used for improving structural integrity and load bearing capacity in biomedical applications of nitinol alloy.
- Quantification of human bone microarchitecture damage in press-fit femoral knee implantation using HR-pQCT and digital volume correlation. [Journal Article]
- JMJ Mech Behav Biomed Mater 2019 May 04; 97:278-287
- Primary press-fit fixation of femoral knee prostheses is obtained thanks to the inside dimensions of the implant being undersized with respect to the bone cuts created intra-operatively, dictated by …
Primary press-fit fixation of femoral knee prostheses is obtained thanks to the inside dimensions of the implant being undersized with respect to the bone cuts created intra-operatively, dictated by a press-fit specified by the implant design. However, during prostheses press-fit implantation, high compressive and shear stresses at the implant-bone interface are generated, which causes permanent bone damage. The extent of this damage is unknown, but it may influence the implant stability and be a contributing factor to aseptic loosening, a main cause of revisions for knee arthroplasty. The aim of this ex-vivo study was to quantify, using high-resolution peripheral quantitative computed tomography (HR-pQCT) imaging and Digital Volume Correlation (DVC), permanent bone deformation due to press-fit femoral knee implantation of a commonly used implant. Six human cadaveric distal femora were resected and imaged with HR-pQCT (60.7 μm/voxel, isotropic). Femurs were fitted with cementless femoral knee implants (Sigma PFC) and rescanned after implant removal. For each femur, permanent deformation was examined in the anterior, posterior-medial and posterior-lateral condyles for volumes of interest (VOIs) of 10 mm depth. The bone volume fraction (BV/TV) for the VOIs in pre- and post-implantation images was calculated, at increasing depth from the bone surface. DVC was applied on the VOIs pre- and post-implantation, to assess trabecular bone displacements and plastically accumulated strains. The "BV/TVpost/BV/TVpre ratio vs. depth" showed, consistently among the six femurs, three consecutive points of interest at increasing bone depth, indicating: bone removal (ratio<100%), compaction (ratio>100%) and no changes (ratio = 100%). Accordingly, the trabecular bone displacement computed by DVC suggested bone compaction up to 2.6 ± 0.8 mm in depth, with peak third principal strains of -162,100 ± 55,000 με (mean absolute error: 1,000-2,000 με, SD: 200-500 με), well above the yield strain of bone (7,000-10,000 με). Combining 3D-imaging, at spatial resolutions obtainable with clinical HR-pQCT, and DVC, determines the extent of plastic deformation and accumulated compressive strains occurring within the bone due to femoral press-fit implantation. The methods and data presented can be used to compare different implants, implant surface coatings and press-fit values. These can also be used to advance and validate computational models by providing information about the bone-implant interface obtained experimentally. Future studies using these methods can assist in determining the influence of bone damage on implant stability and the subsequent osseointegration.
- Eigenstrain Toughening in Presence of Elastic Heterogeneity with Application to Bone. [Journal Article]
- IJInt J Solids Struct 2018; 144-145:137-144
- Transformation toughening has been used in commercial products for several decades in order to increase the toughness of brittle materials. Composites made from an elastic matrix and elastic-plastic …
Transformation toughening has been used in commercial products for several decades in order to increase the toughness of brittle materials. Composites made from an elastic matrix and elastic-plastic inclusions similarly exhibit increased toughness and R-curve behavior due to the residual stress induced in the wake of the crack tip by the unloaded, plastically deforming fillers. These two mechanisms, in which the eigenstrains in the wake of a major crack lead to toughening, belong to the same class. In this study, we investigate the effect of the elastic heterogeneity of the matrix on such toughening mechanisms and observe that increasing the elastic heterogeneity amplifies the effect. The analysis is relevant for bone, which is a highly heterogeneous hierarchical material, in which localized plastic deformation has been recently shown to occur at dilatational bands. Understanding toughening in bone is a subject of current interest in the context of age-related fragility. The heterogeneity-enhanced eigenstrain toughening effect is of interest for a broad range of engineering applications.
- Analysis of facial skeletal asymmetry during foetal development using μCT imaging. [Journal Article]
- OCOrthod Craniofac Res 2019; 22 Suppl 1:199-206
- CONCLUSIONS: The developing foetal facial skeleton displays variable patterns of low magnitude asymmetry. GM and DBA methods offer unique advantages to assess facial asymmetry quantitatively and qualitatively.
- To Drill or to Densify? Clinical Indications for the Use of Osseodensification. [Journal Article]
- CCCompend Contin Educ Dent 2019; 40(5):276-281; quiz 282
- As highlighted in part 1 of this two-part article, primary mechanical stability in implant dentistry is considered a prerequisite for successful osseointegration. While many surgical techniques have …
As highlighted in part 1 of this two-part article, primary mechanical stability in implant dentistry is considered a prerequisite for successful osseointegration. While many surgical techniques have been conceptualized with the goal of improving implant stability, osseodensification (OD) represents a novel method utilizing the accumulation of autogenous bone within the implant site via the compaction of cancellous bone, which has good viscoelastic and plastic deformation characteristics. The philosophy of this technique runs counter to that of conventional bone drilling in that healthy bone is maintained within the implant osteotomy, especially in regions where bone density is already compromised. This article focuses on the clinical indications of OD. Three cases are presented and include a lateral sinus augmentation procedure, a crestal sinus augmentation in combination with use of a synthetic bone putty, and a socket-shield technique in the esthetic zone. The aim of this article is to provide clinicians a better understanding of OD and methods to optimize the technique. It also highlights favorable clinical outcomes in cases where initial bone density has been compromised.
- Deformation behavior of porous PHBV scaffold in compression: A finite element analysis study. [Journal Article]
- JMJ Mech Behav Biomed Mater 2019; 96:1-8
- Macroscopic mechanical properties of porous PHBV bone TE scaffolds have been well studied. However, their mechanical behavior at microscopic level has yet to be explored. In this study, the micro-mec…
Macroscopic mechanical properties of porous PHBV bone TE scaffolds have been well studied. However, their mechanical behavior at microscopic level has yet to be explored. In this study, the micro-mechanical behavior of a PHBV bone scaffold under compression was investigated using a numerical method that combines micro-computed tomography (μ-CT) and finite element analysis (FEA). It was found that the use of a linear-elastic model resulted in an overestimation of the stiffness of the scaffold, whereas a more realistic estimation of the scaffold's deformation behavior was obtained by utilizing a bilinear material model. The onset of plastic deformation occurred in the very early stage of loading resulting in significantly reduced stiffness of the scaffold. The non-uniform and arbitrary microstructure of the scaffold led to a heterogeneous stress distribution within the porous construct, which was subjected to a mixture of compressive and tensile stresses. Nevertheless, the resultant stress contours showed that the scaffold experienced primarily elastic deformation when it was loaded up to 0.003 strain, while localized plastic deformation occurred at sharp corners and necked regions of the micro-struts. The scaffold expanded slightly in the horizontal direction as it was compressed and the change in geometries of pores within the scaffold was insignificant. The proposed method provides a valuable tool to study the localized mechanical behavior of bone scaffolds in micrometer scale with arbitrary porous architecture. This approach could prove highly useful for guiding the fabrication of scaffolds that have anatomy specific mechanical properties and porous architecture.
- Fluid Cartilage as New Autologous Biomaterial in the Treatment of Minor Nose Defects: Clinical and Microscopic Difference Amongst Diced, Crushed, and Fluid Cartilage. [Journal Article]
- MMaterials (Basel) 2019 Mar 31; 12(7)
- Developing cartilage constructs with injectability, appropriate matrix composition, and persistent cartilaginous phenotype remains an enduring challenge in cartilage repair. Fourteen patients with mi…
Developing cartilage constructs with injectability, appropriate matrix composition, and persistent cartilaginous phenotype remains an enduring challenge in cartilage repair. Fourteen patients with minor contour deformity were treated with fluid cartilage filler gently injected as autologous fluid graft in deep planes of defect of the nose that were close to the bone or the cartilage. A computerized tomographic scan control was performed after 12 months. Pearson's Chi-square test was used to investigate differences in cartilage density between native and newly formed cartilages. The endpoints were the possibility of using fluid cartilage as filler with aesthetic and functional improvement and versatility. Patients were followed up for two years. The constructs of fluid cartilage graft that were injected in the deep plane resulted in a persistent cartilage tissue with appropriate morphology, adequate central nutritional perfusion without central necrosis or ossification, and further augmented nasal dorsum without obvious contraction and deformation. This report demonstrated that fluid cartilage grafts are useful for cartilage regeneration in patients with outcomes of rhinoplasty, internal nasal valve collapse, and minor congenital nose aesthetics deformity.
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- Mechanical and Biological Advantages of a Tri-Oval Implant Design. [Journal Article]
- JCJ Clin Med 2019 Mar 28; 8(4)
- Of all geometric shapes, a tri-oval one may be the strongest because of its capacity to bear large loads with neither rotation nor deformation. Here, we modified the external shape of a dental implan…
Of all geometric shapes, a tri-oval one may be the strongest because of its capacity to bear large loads with neither rotation nor deformation. Here, we modified the external shape of a dental implant from circular to tri-oval, aiming to create a combination of high strain and low strain peri-implant environment that would ensure both primary implant stability and rapid osseointegration, respectively. Using in vivo mouse models, we tested the effects of this geometric alteration on implant survival and osseointegration over time. The maxima regions of tri-oval implants provided superior primary stability without increasing insertion torque. The minima regions of tri-oval implants presented low compressive strain and significantly less osteocyte apoptosis, which led to minimal bone resorption compared to the round implants. The rate of new bone accrual was also faster around the tri-oval implants. We further subjected both round and tri-oval implants to occlusal loading immediately after placement. In contrast to the round implants that exhibited a significant dip in stability that eventually led to their failure, the tri-oval implants maintained their stability throughout the osseointegration period. Collectively, these multiscale biomechanical analyses demonstrated the superior in vivo performance of the tri-oval implant design.