The biomechanical analysis of three plating fixation systems for periprosthetic femoral fracture near the tip of a total hip arthroplasty

<p>Abstract</p> <p>Background</p> <p>A variety of techniques are available for fixation of femoral shaft fractures following total hip arthroplasty. The optimal surgical repair method still remains a point of controversy in the literature. However, few studies have quantified the performance of such repair constructs. This study biomechanically examined 3 different screw-plate and cable-plate systems for fixation of periprosthetic femoral fractures near the tip of a total hip arthroplasty.</p> <p>Methods</p> <p>Twelve pairs of human cadaveric femurs were utilized. Each left femur was prepared for the cemented insertion of the femoral component of a total hip implant. Femoral fractures were created in the femurs and subsequently repaired with Construct A (Zimmer Cable Ready System), Construct B (AO Cable-Plate System), or Construct C (Dall-Miles Cable Grip System). Right femora served as matched intact controls. Axial, torsional, and four-point bending tests were performed to obtain stiffness values.</p> <p>Results</p> <p>All repair systems showed 3.08 to 5.33 times greater axial stiffness over intact control specimens. Four-point normalized bending (0.69 to 0.85) and normalized torsional (0.55 to 0.69) stiffnesses were lower than intact controls for most comparisons. Screw-plates provided either greater or equal stiffness compared to cable-plates in almost all cases. There were no statistical differences between plating systems A, B, or C when compared to each other (p > 0.05).</p> <p>Conclusions</p> <p>Screw-plate systems provide more optimal mechanical stability than cable-plate systems for periprosthetic femur fractures near the tip of a total hip arthroplasty.</p

A biomechanical assessment of modular and monoblock revision hip implants using FE analysis and strain gage measurements

<p>Abstract</p> <p>Background</p> <p>The bone loss associated with revision surgery or pathology has been the impetus for developing modular revision total hip prostheses. Few studies have assessed these modular implants quantitatively from a mechanical standpoint.</p> <p>Methods</p> <p>Three-dimensional finite element (FE) models were developed to mimic a hip implant alone (Construct A) and a hip implant-femur configuration (Construct B). Bonded contact was assumed for all interfaces to simulate long-term bony ongrowth and stability. The hip implants modeled were a Modular stem having two interlocking parts (Zimmer Modular Revision Hip System, Zimmer, Warsaw, IN, USA) and a Monoblock stem made from a single piece of material (Stryker Restoration HA Hip System, Stryker, Mahwah, NJ, USA). Axial loads of 700 and 2000 N were applied to Construct A and 2000 N to Construct B models. Stiffness, strain, and stress were computed. Mechanical tests using axial loads were used for Construct A to validate the FE model. Strain gages were placed along the medial and lateral side of the hip implants at 8 locations to measure axial strain distribution.</p> <p>Results</p> <p>There was approximately a 3% average difference between FE and experimental strains for Construct A at all locations for the Modular implant and in the proximal region for the Monoblock implant. FE results for Construct B showed that both implants carried the majority (Modular, 76%; Monoblock, 66%) of the 2000 N load relative to the femur. FE analysis and experiments demonstrated that the Modular implant was 3 to 4.5 times mechanically stiffer than the Monoblock due primarily to geometric differences.</p> <p>Conclusions</p> <p>This study provides mechanical characteristics of revision hip implants at sub-clinical axial loads as an initial predictor of potential failure.</p

SESQUITERPENE LACTONES FROM PERITYLE EMORYI

Abstract-The extract of the aerial parts of Perityle emoryi gave, in addition to seven known sesquiterpene lactones, six new germacranolides and a guaianolide as well as a further thymol derivative together with several known ones and two labdanes. The structures were elucidated by high field &apos;H NMR spectroscopy. The chemotaxonomic aspects are discussed briefly

Biomechanical Measurement Error Can Be Caused by Fujifilm Thickness: A Theoretical, Experimental, and Computational Analysis

© 2017 Ahmed Sarwar et al. This is the first study to quantify the measurement error due to the physical thickness of Fujifilm for several material combinations relevant to orthopaedics. Theoretical and experimental analyses were conducted for cylinder-on-flat indentation over a series of forces (750 and 3000 N), cylinder diameters (0 to 80 mm), and material combinations (metal-on-metal, MOM; metal-on-polymer, MOP; metal-on-bone, MOB). For the scenario without Fujifilm, classic Hertzian theory predicted the true line-type contact width as WO={(8FDcyl)/(πLcyl)[(1-cyl2)/Ecyl+(1-flat2)/Eflat]}1/2, where F is compressive force, Dcyl is cylinder diameter, Lcyl is cylinder length, cyl and flat are cylinder and flat Poisson\u27s ratios, and Ecyl and Eflat are cylinder and flat elastic moduli. For the scenario with Fujifilm, experimental measurements resulted in contact widths of WF=0.1778×F0.2273×D0.2936 for MOM tests, WF=0.0449×F0.4664×D0.4201 for MOP tests, and WF=0.1647×F0.2397×D0.3394 for MOB tests, where F is compressive force and D is cylinder diameter. Fujifilm thickness error ratio WF/WO showed a nonlinear decrease versus cylinder diameter, whilst error graphs shifted down as force increased. Computational finite element analysis for several test cases agreed with theoretical and experimental data, respectively, to within 3.3% and 1.4%. Despite its wide use, Fujifilm\u27s measurement errors must be kept in mind when employed in orthopaedic biomechanics research

Salt-induced changes in the antioxidant system and viability of oilseed rape

This work was aimed to investigate the effect of salt (NaCl) stress on three oilseed rape (Brassica napus L.) cultivars: 'Banacanka', 'Jasna' and 'Kata'. The following parameters were determined: antioxidant enzymes superoxide dismutase (SOD) and guaiacol peroxidase (GPX), reduced glutathione (GSH) quantity, lipid peroxidation (LP) intensity, radical-scavenging capacity (DPPH-RSC), hydroxyl radical scavenging ((OH)-O-center dot radicals) and ferric reducing antioxidant power (FRAP). Seed viability was determined using the standard laboratory test for germination as well as the seed accelerated aging test measuring the germination, shoot and root length. The plants were subjected to three salt treatments: 0, 100, 150 and 200 mmol dm(-3) NaCl for 7 days. All three cultivars responded with an increase of lipid peroxidation in seedlings and with a decrease of GPX activity. 'Banacanka' was found to be the most vulnerable cultivar, with an increase of 237% of LP intensity in comparison to the control at the highest NaCl concentration. The induction of the SOD activity was observed for all three cultivars by different NaCl concentrations. The antioxidant capacity measured by FRAP, DPPH-RSC and (OH)-O-center dot radicals was also induced, especially FRAP at the highest concentration in the cultivar 'Jasna' (by 282%). Germination, shoot and root length decreased for all investigated cultivars. Our results showed that cultivar 'Jasna' is the most adapted to salt stress because of the highest SOD activity and accumulation of antioxidants. Furthermore, this research suggests that some of the antioxidant parameters can be useful biochemical markers for the selection of oilseed rape tolerant cultivars under the conditions of salinity

“In small places, close to home”: urban environmental impacts on child rights across four global cities

Urban environments influence child behaviours, exposures and experiences and may affect health, development, achievement and realization of fundamental human rights. We examined the status of eleven UN Convention on the Rights of the Child articles, in a multi-case study across four global cities. Within all study cities, children experienced unequal exposure to urban environmental risks and amenities. Many violations of child rights are related to car-based transportation systems and further challenged by pressures on urban systems from rapid population increases in the context of climate change. A child rights framework provides principles for a collective, multi-sectoral re-imagination of urban environments that support the human rights of all citizens