Stress Distribution Along the Implant-Bone Interface: A Pilot Study using Finite Element Analysis to Compare Tilted and Non-Tilted Implants under Different Loads

Introduction: This study used finite element analysis to evaluate stress distribution of implants placed at different angulations under two loadings. Stress was measured at the implant-bone interface. Methods: Four models of implant and bone were manufactured via three-dimensional optical scanning and point cloud data extraction. They included implants placed: 1) Without tilt 2) tilted at 15o, 3) tilted at 30o, and 4) tilted at 45o. A tissue-level implant was scanned, and a mandible bone model was extracted from cone-beam computed tomography systems. A 3D model of the implants in the mandible were constructed. The finite element analyses were carried out using simulation software. The physical interaction at implant-bone interfaces during loading were considered through bonded surface-to-surface contacts. Static loading (with axial forces of 150N and 300N) were applied to evaluate the implant-bone model. Results: The amount of stress along the implant-bone interface was greater under 300N loading than 150N loading. The stress along tilted implants were greater than that of non-tilted implants under both 150N and 300N. There was no significant variance among the various angles of implants. The displacements along the tilted implants were larger than those of nontilted implants. The stress distribution along the implant-bone interface increased when the loading increased. Conclusion: The tilted implants presented greater stress distribution. The in vitro stress distribution analysis using FEA will provide clinical guidance for implant placement.

Biomechanical Comparison of Lag Screw and Non-spiral Blade Fixation of a Novel Femoral Trochanteric Nail in an Osteoporotic Bone Model

PurposeThere is no consensus regarding the advantages of the lag screw type over the blade type for treating femoral trochanteric fractures. We aimed to investigate whether non-spiral blade (Conventional-Blade, Fid-Blade) nails provide better biomechanical fixation than lag screws in a severe osteoporotic bone model.MethodsDifferent severities of osteoporotic cancellous bone were modelled using polyurethane foam blocks of three densities (0.24, 0.16, and 0.08 g/cm3). Three torsional tests were performed using each component for each bone density and the maximum torque was recorded, and the energy required to achieve 30° rotation was calculated. Using a push-in test, the maximum force was recorded, and the energy required to achieve 4-mm displacement was calculated. ResultsFor 0.08-g/cm3 density, the peak torques to achieve 30° rotation, energy required to achieve 30° rotation, peak force to achieve 4-mm displacement, and energy required to achieve 4-mm displacement were significantly greater for Conventional-Blade and Fid-Blade than for Lag Screw. ConclusionsConventional-Blade and Fid-Blade nails exhibited significantly higher values than Lag Screw under any test condition. The blade-type nail component may have a better fixation capability than the lag screw type in a severe osteoporotic bone model.

Modeling In Vitro Osteoarthritis Phenotypes in a Vascularized Bone Model Based on a Bone-Marrow Derived Mesenchymal Cell Line and Endothelial Cells

The subchondral bone and its associated vasculature play an important role in the onset of osteoarthritis (OA). Integration of different aspects of the OA environment into multi-cellular and complex human, in vitro models is therefore needed to properly represent the pathology. In this study, we exploited a mesenchymal stromal cell line/endothelial cell co-culture to produce an in vitro human model of vascularized osteogenic tissue. A cocktail of inflammatory cytokines, or conditioned medium from mechanically-induced OA engineered microcartilage, was administered to this vascularized bone model to mimic the inflamed OA environment, hypothesizing that these treatments could induce the onset of specific pathological traits. Exposure to the inflammatory factors led to increased network formation by endothelial cells, reminiscent of the abnormal angiogenesis found in OA subchondral bone, demineralization of the constructs, and increased collagen production, signs of OA related bone sclerosis. Furthermore, inflammation led to augmented expression of osteogenic (alkaline phosphatase (ALP) and osteocalcin (OCN)) and angiogenic (vascular endothelial growth factor (VEGF)) genes. The treatment, with a conditioned medium from the mechanically-induced OA engineered microcartilage, also caused increased demineralization and expression of ALP, OCN, ADAMTS5, and VEGF; however, changes in network formation by endothelial cells were not observed in this second case, suggesting a possible different mechanism of action in inducing OA-like phenotypes. We propose that this vascularized bone model could represent a first step for the in vitro study of bone changes under OA mimicking conditions and possibly serve as a tool in testing anti-OA drugs.

Comparison of three intraosseous access devices for resuscitation of term neonates: a randomised simulation study

ObjectivesTo compare the success rates and ease of use of three intraosseous (IO) access devices used in term neonates.DesignA three-arm randomised controlled simulation study was conducted.SettingA simulation laboratory.ParticipantsSeventy-two paediatric residents completing their emergency department rotation as part of their residency training, and 20 paediatric specialists.InterventionUsing an animal bone model, the one-attempt success rate of the EZ-IO drill, the NIO-I needle and the Jamshidi needle was compared. Uncooked Cornish Hen bones were used because of their similarity in length and diameter to the bones of neonates. Participants were asked to record the perceived ease of use of their assigned device using a 5-point Likert Scale.Main outcome measureThe main outcome was the visualisation of flow emerging from the distal end of the bone, and perceived ease of use of the three IO devices.ResultsThe EZ-IO, NIO-I and Jamshidi groups included 30, 31 and 31 participants, respectively, with median (IQR) years of experience of 3 (2–5), 3 (2–6) and 4 (3–5) years. Participants had significantly lower one-attempt success rates with the EZ-IO drill than with the NIO-I and the Jamshidi needles (14 of 30 (46.7%) vs 24 of 31 (77.4%); p=0.016, and 14 of 30 (46.7%) vs 25 of 31 (80.7%); p=0.007, respectively). The median (IQR) ease-of-use score of the EZ-IO drill was higher than that of the NIO-I and Jamshidi needles (5 (4–5) vs 4 (4–5); p=0.008, and 5 (4–5) vs 4 (3–4); p=0.0004, respectively).ConclusionsAlthough easier to use, the EZ-IO drill demonstrated lower success rates than the IO needles in establishing IO access on a neonatal bone model.