Foam Block Research Articles

Biomechanical comparison of lag screw and non-spiral blade fixation of a novel femoral trochanteric nail in an osteoporotic bone model

There 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. Different 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 density of the polyurethane block, and the maximum torque was recorded; subsequently, 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. For 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 those for Lag Screw. The fixation stability of the blade-type Magnum nail component is better than that of the lag screw type under any test condition. The blade-type nail component may have better fixation stability than the lag screw type in a severe osteoporotic bone model.

Effect of porous blocks on flow development through a serpentine cooling passage under stationary and rotating conditions

This study investigates how the inclusion of porous block influences the flow development in a serpentine passage, which consists of two straight square-sectioned ducts connected with a square-ended bend. Aluminium porous foam blocks have been attached to two opposite walls of the straight sections normal to the bend in a staggered manner, used as turbulence promoters. The investigation considers flows in the passage in stationary conditions, and in orthogonal rotation. Particle image velocimetry (PIV) is used to map out the flow development. The wall static pressure distribution along two sides of the passage (the leading and trailing under rotating conditions) is also provided. Tests are carried out at Reynolds numbers of 16,000, 26,000 and 36,000 and rotation numbers of 0.32 and 0.64. Preliminary tests, in a smooth (without porous blocks) passage of identical geometry, establish the reference conditions and enable the identification and quantification of the effects of the porous blocks on the flow development. PIV results show the meandering manner of the flow both upstream and downstream of the bend region, due to the presence of the porous blocks. Within the bend, in contrast to the case with a smooth upstream section, a single vortex dominates the flow. While rotation does not change the overall flow character, it does force more fluid through the blocks along the trailing (pressure) side of the duct. For both stationary and rotating conditions, the upstream section is long enough for the flow to become periodic over successive rib intervals, which produces very attractive data for CFD validation. These data include mean flow as well as second-moment profiles. The pressure coefficient is found to decrease linearly along the channel, due to the high blockage by the porous blocks. Rotation does not change the shape of the pressure coefficient profile but causes a greater reduction along the passage.

Robust locomotor performance of squirrel monkeys (Saimiri boliviensis) in response to simulated changes in support diameter and compliance.

Arboreal environments require overcoming navigational challenges not typically encountered in other terrestrial habitats. Supports are unevenly distributed and vary in diameter, orientation, and compliance. To better understand the strategies that arboreal animals use to maintain stability in this environment, laboratory researchers must endeavor to mimic those conditions. Here, we evaluate how squirrel monkeys (Saimiri boliviensis) adjust their locomotor mechanics in response to variation in support diameter and compliance. We used high-speed cameras to film two juvenile female monkeys as they walked across poles of varying diameters (5, 2.5, and 1.25 cm). Poles were mounted on either a stiff wooden base ("stable" condition) or foam blocks ("compliant" condition). Six force transducers embedded within the pole trackway recorded substrate reaction forces during locomotion. We predicted that squirrel monkeys would walk more slowly on narrow and compliant supports and adopt more "compliant" gait mechanics, increasing stride lengths, duty factors, and an average number of limbs gripping the support, while the decreasing center of mass height, stride frequencies, and peak forces. We observed few significant adjustments to squirrel monkey locomotor kinematics in response to changes in either support diameter or compliance, and the changes we did observe were often tempered by interactions with locomotor speed. These results differ from a similar study of common marmosets (i.e., Callithrix jacchus, with relatively poor grasping abilities), where variation in diameter and compliance substantially impacted gait kinematics. Squirrel monkeys' strong grasping apparatus, long and mobile tails, and other adaptations for arboreal travel likely facilitate robust locomotor performance despite substrate precarity.

Walking All over COVID-19: The Rapid Development of STRIDE in Your Room, an Innovative Approach to Enhance a Hospital-Based Walking Program during the Pandemic.

Hospitalization is common among older adults. Prolonged time in bed during hospitalization can lead to deconditioning and functional impairments. Our team is currently working with Department of Veterans Affairs (VA) medical centers across the United States to implement STRIDE (assiSTed eaRly mobIlity for hospitalizeD older vEterans), a hospital-based walking program designed to mitigate the risks of immobility during hospitalization. However, the COVID-19 pandemic made in-person, or face-to-face, walking challenging due to social distancing recommendations and infection control concerns. In response, our team applied principles of implementation science, including stakeholder engagement, prototype development and refinement, and rapid dissemination and feedback, to create STRIDE in Your Room (SiYR). Consisting of self-guided exercises, light exercise equipment (e.g., TheraBands, stress ball, foam blocks, pedometer), the SiYR program provided safe alternative activities when face-to-face walking was not available during the pandemic. We describe the methods used in developing the SiYR program; present feedback from participating sites; and share initial implementation experiences, lessons learned, and future directions.

Optimization of Preparation of Foamed Concrete Based on Orthogonal Experiment and Range Analysis

For the purpose of reducing the energy consumption and construction cost of buildings, the preparation process of geopolymer based foamed concrete, which is a novel material of the wall and roof of building, had been studied in detail. Water glass and sodium hydroxide were used as the alkali activator to excite the mixture consists of slag, fly ash and Kaolin to form the geopolymer matrix, and finally the foams generated using the physical foaming method were filled into the geopolymer matrix to produce geopolymer-based foamed concrete blocks. In the preparation process, firstly one of the four parameters of foam content, water-binder ratio, water glass content, and water glass modulus had been changed separately to study the influence of a single factor on the compressive strength, dry density, thermal conductivity and specific strength of foamed concrete blocks. The experimental results show that the above four factors have different degrees of influence on the concerned performances. Next, some representative combinations of these factors were constructed by orthogonal experiment method, and the influence degree of each combination on the concerned performances was determined by means of range analysis. According to the results of analysis, the most important influencing factor in terms of thermal conductivity was the water-binder ratio, followed by foam content, water glass modulus and water glass content. When the foam content is 1.58%, the water-binder ratio is 0.45, the water glass content is 30%, and the water glass modulus is 1.2, the thermal conductivity of the prepared geopolymer foam concrete reaches 0.044 W/(m·K), which satisfies the expected requirements for heating in severe cold areas.

Anterior Glenoid Reconstruction With Distal Tibial Allograft: Biomechanical Impact of Fixation and Presence of a Retained Lateral Cortex.

Background:Glenoid reconstruction with distal tibial allograft (DTA) is a known surgical option for treating recurrent glenohumeral instability with anterior glenoid bone loss; however, biomechanical analysis has yet to determine how graft variability and fixation options alter the torque of screw insertion and load to failure.Hypothesis:It was hypothesized that retention of the lateral cortex of the DTA graft and the presence of a washer with the screw will significantly increase the maximum screw placement torque as well as the load to failure.Study Design:Controlled laboratory study.Methods:Whole, fresh distal tibias were used to harvest 28 DTA grafts, half of which had the lateral cortex removed and half of which had the lateral cortex intact. The grafts were secured to polyurethane solid foam blocks with a 2-mm epoxy laminate to simulate a glenoid with an intact posterior glenoid cortex. Grafts underwent fixation with 4.0-mm cannulated drills, and screws and washers were used for half of each group of grafts while screws alone were used for the other half, creating 4 equal groups of 7 samples each. A digital torque-measuring screwdriver recorded peak torque for screw insertion. Constructs were then tested in compression with a uniaxial materials testing system and loaded in displacement control at 100 mm/min until at least 3 mm of displacement occurred. Ultimate load was defined as the load sustained at clinical failure.Results:The use of a washer significantly improved the ultimate torque that could be applied to the screws (+cortex and +washer = 12.42 N·m [SE, 0.82]; –cortex and +washer = 10.54 N·m [SE, 0.59]) (P < .0001), whereas the presence of the native bone cortex did not have a significant effect (+cortex and –washer = 7.83 N·m [SE, 0.40]; –cortex and –washer = 8.03 N·m [SE, 0.56]) (P = .181).Conclusion:In a hybrid construct of fresh cadaveric DTA grafts secured to a foam block glenoid model, the addition of washers was more effective than the retention of the lateral distal tibial cortex for both load to failure and peak torque during screw insertion.Clinical Relevance:This biomechanical study is relevant to the surgeon when choosing a graft and selecting fixation options during glenoid reconstruction with a DTA graft.

Transient Finite Element Simulation of a Lithium-Ion Battery Pack Thermal Management System Based on Latent Heat System Materials

Battery packs in high-intensity use run the risk of overheating, potentially inducing catastrophic thermal runaway. Thermal runaway occurs when an individual cell in a connected system fails and subsequently applies increased stress on the remaining cells, leading to cascading failures and destruction of the battery pack as a whole. One method for controlling battery temperature during usage is utilizing the battery pack casing as a latent heat system (LHS), specifically incorporating phase-change materials (PCMs). Using this method, the transient thermal response of a 84-cell, 270 V lithium-ion battery pack for an aircraft application was simulated using ANSYS FLUENT. Heat generation rates and specific heat capacity of a single cell were experimentally measured and used as input to the thermal and mechanical model. A heat generation load was applied to the entire battery pack, and natural convection film boundary conditions were applied to the exterior of the enclosure. The maximum temperature of the battery pack without any casing reached 69.8 ᵒC after 800 s of usage at a simulated peak power draw of 1013 W or 16 A. This exceeds the manufacturer’s maximum recommended operating temperature of 60 ᵒC. For other materials, we found the maximum temperature of the batteries reached 57.0 ᵒC with plastic casing and 45.0 ᵒC with aluminum casing. We present a design of the pack that incorporates a passive thermal management system using a composite material consisting of phase-changing material, Puretemp60®, mixed with expanded graphite (EG). Simulations of the battery pack showed a decrease in the maximum temperature with the Puretemp60® as the sole material reaching a maximum of 54.2 ᵒC and the Puretemp EG composite matrix having a maximum temperature of 51.1 ᵒC, both after 800 s at the same power draw.The optimal material combination was then determined through evaluating several PCM and EG composites in several ratios using ANSYS FLUENT, followed by experimental testing. The mixture was cost effective, easy to mix, and demonstrated good mechanical properties. Results illustrated that a mixture of 25% expanded graphite with 75% Puretemp60® (PCM) was capable of maintaining battery temperatures within the acceptable operating range under moderate load conditions and therefore preventing thermal runaway. A resulting weight reduction of about 23.5% was also achieved using the Puretemp EG composite matrix in comparison to aluminum casing, and about a 7.2% reduction compared to plastic casing.Differential scanning calorimetry (DSC) was utilized to determine the phase transformation of the composites. The addition of expanded graphite minimally affected the phase transformation temperature, while decreasing the latent heat of transformation by about 40%. Scanning electron microscope (SEM) pictures visualized the morphology of the graphite during each stage of the composite fabrication process. The Puretemp60® and expanded graphite were easily mixed and the backscattering electron images indicated the composition was homogenous.The heat generation rate of the battery was calculated using the q̇gen= mCp(dT/dt) + UA∆T. The change in temperature with respect to time was experimentally determined from a series of discharges. Heat generation in the batteries was modeled as uniformly distributed. The average of the experimentally measured heat generation rates for a 1P constant power discharge were divided by the volume of the battery to yield a curve for the average body heat flux load in W/m3 over the discharge of the battery. A polynomial curve fit to the average heat generation rates was applied as a heat load to each battery in the simulation. The heat generation due to discharge was tested with a setup where the battery was insulated in polyurethane foam in order to reduce convection heat transfer during the experiments. A polyurethane foam block was cut such that the battery could be placed in the center, along with three T-type thermocouples to measure the surface temperature and external air temperatures. Two metal cylinders, one consisting of copper and the other of 6061 aluminum, were machined to the same cylindrical dimensions as the battery. These cylinders were then used to determine the heat loss, or UA value, of the foam insulation block setup. A National instruments NI 9147, Chroma Programmable DC Power Supply, and LabView software were used for the experiments. Figure 1

Underwater multilateral tele-operation control with constant time delays

In the complex underwater environment, it is difficult to complete teleoperation tasks due to dynamic environments. Through cooperation among manipulators, a multilateral teleoperation system has the potential to achieve better performance than conventional bilateral teleoperation systems. In this paper, we propose a multilateral teleoperation control method that can be easily applied for underwater grasping tasks. Specifically, a new structure involving two (or multiple) masters and a single slave is investigated, which is treated as a linear combination of multiple subsystems under time delays. A control method based on linear matrix inequality exponential convergence and nonlinear disturbance is presented to estimate the model uncertainties of the system and unknown external disturbances during grasping process. The asymptotic stability is analyzed using the established Lyapunov–Krasovskii functional. Numerical simulations and real experiments performed for the task of grasping a plastic foam block are reported to verify the proposed control method in real applications.

Biomechanical Stability of the Sacroiliac Joint with Differing Implant Configurations in a Synthetic Model.

The sacroiliac joint (SIJ) is responsible for 15%-30% of chronic low back pain and fusion is increasingly used to alleviate chronic SIJ pain in adults. However, questions remain as to the most effective implant patterns to stabilize the joint. The objective of this biomechanical study was to evaluate how different implant spacing, configuration and quantity effect range of motion (ROM) of a synthetic foam SIJ model. Triangular SIJ fusion implants were tested in six patterns using three implants, and two patterns with two implants (n = 5/pattern). Linear, triangular, and angled (10° or 20°) implant patterns were used with spacing of 13 or 22 mm between implants. Implants were placed through a denser polyurethane foam block (0.32 g/cm3) representing the ilium and into a less dense block representing the sacrum (0.16 g/cm3) to a depth 30 mm with a 2-mm gap between blocks. Cyclic torsion and shear testing were conducted for 10,000 cycles and ROM was recorded. Pullout testing was conducted on non-cycled (n = 10) implants and individually on all implants after construct cycling. ROM was significantly lower for all 22-mm implant patterns compared to the 13 mm linear pattern after cyclic loading in both torsion and shear. The use of three implants provided 60% and 86% greater stability, respectively, than two implants with spacing of 22 and 13 mm. Pullout resistance followed similar trends with the lowest forces occurring in closely spaced patterns that used two implants. This study demonstrated that the use of three implants and maximizing the spacing between implants might provide greater stability to the SIJ. If implants must be placed closely, then nonlinear patterns may improve construct stability.

Reliability and Correlation of Different Devices for the Evaluation of Primary Implant Stability: An In Vitro Study

Our aim was to analyze the correlation between the IT evaluated by a surgical motor and the primary implant stability (ISQ) measured by two RFA devices, Osstell and Penguin, in an in vitro model. This study examines the effect of bone type (soft or dense), implant length (13 mm or 8 mm), and implant design (CC: conical connection; IH: internal hexagon), on this correlation. Ninety-six implants were inserted using a surgical motor (IT) into two types of synthetic foam blocks. Initial measurements for both the peak IT and ISQ were recorded at the point when implant insertion was stopped by the surgical motor, and the final measurements were recorded when the implant was completely inserted into the synthetic blocks using only the RFA devices. Our null hypothesis was that there is a good correlation between the devices, independent of the implant length, design, or bone type. We found a positive, significant correlation between the IT, and the Osstell and Penguin devices. Implant length and bone type did not affect this correlation. The correlation between the devices in the CC design was maintained; however, in the IH design it was maintained only between the RFA devices. We concluded that there is a high positive correlation between the IT and ISQ from a mechanical perspective, which was not affected by bone type or implant length but was affected by the implant design.

An In Vitro Analysis on Polyurethane Foam Blocks of the Insertion Torque (IT) Values, Removal Torque Values (RTVs), and Resonance Frequency Analysis (RFA) Values in Tapered and Cylindrical Implants

Background: Several different dental implant microgeometries have been investigated in the literature for use in low-density bone sites. The polyurethane solid rigid blocks represent an optimal in vitro study model for dental implants, because their composition is characterized by symmetrical linear chains of monomers of hexa-methylene sequences producing a self-polymerization process. The aim of the present investigation was to evaluate the primary stability of cylindrical and tapered implants positioned into low-density polyurethane solid rigid blocks. Materials and Methods: Two different macrogeometries, cylindrical (4 mm diameter and 10 mm length) and tapered dental implants (4.20 mm diameter and 10 mm length), were investigated in the present study. The implants were inserted into 10 PCF and 20 PCF polyurethane blocks, with and without an additional cortical layer. The insertion torque (IT) values, the removal torque values (RTVs), and the resonance frequency analysis (RFA) values were measured and recorded. Results: A total of 80 sites were tested, and a significant increased primary stability (PS) was detected in favour of tapered dental implants when compared to cylindrical implants in all experimental conditions (p < 0.05). Higher IT, RT, and RFA values were measured in tapered implants in 10 and 20 PCF polyurethane blocks, both with and without the additional cortical layer. Conclusions: Both implants showed sufficient primary stability in poor density substrates, while, on the other hand, the tapered microgeometry showed characteristics that could also lead to clinical application in low-density posterior maxillary sites, even with a drastically decreased bone cortical component.

Assessment of trapezial prosthetic cup migration: A biomechanical study

We performed a biomechanical study using 60 Sawbones® rigid foam blocks of two simulated densities (osteoporotic, n = 30 and non-osteoporotic, n = 30) and 10 cadaveric trapezium bones from fresh-frozen, unembalmed adult cadaver hands to assess the trapezial prosthetic cup migration with progressively greater compression loads (10–40 kg). Two cups from the Touch® prosthesis were compared: 9-mm conical cup and 9-mm spherical cup. Uniaxial compression tests were carried out using an MTS Criterion® Series 40 Electromechanical Testing System. Cup migration was measured in millimeters (mm) at 10, 20, and 40 kg of compression load. Median cup migration values were similar in the cadaveric trapezium bones and Sawbones® non-osteoporotic blocks, and higher in the Sawbones® osteoporotic blocks. In the cadaveric trapezium bones and the Sawbones® non-osteoporotic blocks, migration values were less than or equal to 0.1 mm for 10 and 20 kg loads; it was 0.2 mm for 40 kg load. In the Sawbones® osteoporotic blocks, migration values were less than or equal to 0.3 mm for 10 and 20 kg loads; it was 0.4–0.5 mm for 40 kg load. There was no significant difference between the two cup shapes in both cadaveric trapezium bones and Sawbones® non-osteoporotic blocks. In Sawbones® osteoporotic blocks, the largest difference between the two cup shapes was 0.1 mm for loads up to 40 kg, which corresponded to our measurement accuracy. Our findings indicate that the trapezial component of total trapeziometacarpal joint arthroplasty undergoes very weak migration for axial compression loads up to 40 kg, presumably below the threshold of clinical relevance. The cup shape did not have an obvious influence; however, low bone mineral density may result in greater cup migration.

P3. Total implant contact area versus contact surface topology: Which one has a greater role on subsidence resistance of an interbody device, comparison of two 3D-printed titanium anterior lumbar spine fixation devices

<h3>BACKGROUND CONTEXT</h3> Anatomical loads in combination with poor bone quality may lead to interbody fixation device subsidence. Severe subsidence can often cause nerve compression and pain that may require revision surgery. It is often believed that the total contact area or footprint size of the implant has a direct impact on subsidence resistance of the interbody device. Traditionally, it was believed that cages with larger contact area have low incidence and severity of subsidence versus cages with smaller total contact area at bone-implant interface. With the advancement in additive manufacturing, we are able to create implants with advanced structural designs and surface topology that can improve subsidence resistance of the interbody device. These new designs focus on architecture and load distribution at the bone implant interface rather than overall dimensional design specifications. <h3>PURPOSE</h3> This study is aimed to evaluate subsidence resistance of two 3D-printed titanium ALIF interbody devices of the same size, but with different contact surface topology. <h3>STUDY DESIGN/SETTING</h3> Mechanical testing using foam blocks. <h3>OUTCOME MEASURES</h3> Subsidence rate of different interbody constructs. <h3>METHODS</h3> Two ALIF 3D-printed titanium interbody fixation devices were used. The first device had a truss design that spans throughout the entire construct and contains a snowshoe style bone interface and the other had two cylindrical holes through the center with micro lattice truss structure filling the rest of the volume. Both interbody devices were the same dimensions (36mm x 25mm, width x depth and 18mm tall). The truss device had the total graft volume of 7cc whereas the predicate device had the overall graft volume of 1cc. The total metal-to-bone contact area at the endplate was 401mm2 for the truss device versus 620mm2 for the predicate device. To mimic mechanical properties similar to human bone density (osteoporotic through normal), 5, 10, 15 and 20 PCF SawBone® foam blocks were utilized for testing. To mimic clinical subsidence, the interbody device was placed over the foam block and compressive displacement was applied to push the device into the foam substrate at the rate of 5mm/min. The test was repeated 6 times for each block/implant combination. The subsidence load at 1 and 2mm displacement was collected for each test combination. To calculate the modulus/stiffness, the ratio of load (normalized to contact area) to axial compression rate of the cage-only construct was calculated. Two-way ANOVA with Sidak-Bonferroni Posthoc was used for multiple comparisons and analysis of statistical significance. <h3>RESULTS</h3> The truss interbody device had subsidence resistance significantly greater than the generic titanium device at both 1mm and 2mm subsidence rates (p<0.05) across all density blocks. In foam representing osteoporotic bone (5pcf), the truss cage had subsidence resistance load of 238.3N±25.6N vs 172.2N ±13N in the predicate cage at 1mm displacement respectively. The corresponding numbers at in rigid bone (20PCF) were 1774N±174N vs 1428N ±66N. <h3>CONCLUSIONS</h3> The truss device with snowshoe design had metal-to-bone contact area of 60% of the predicate device and had total graft volume of 7 times of the predicate device; nevertheless, the truss device demonstrated significantly better resistance to subsidence for all foam densities including those that mimic osteoporotic bone compared to the same size predicate titanium device. The subsidence resistance of the truss cage, despite its smaller contact area for the same footprint size, may be due to the a more efficient distribution of load across the bone/implant interface where the load is uniformly distributed across more of the interbody footprint. The data suggests that the implant's surface contact topology at the endplate plays a greater role than the overall contact area for resisting subsidence. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

76. Effect of implant endplate surface topology on subsidence resistance in cervical interbody fixation: comparison of two 3D printed titanium cervical spine fixation devices

<h3>BACKGROUND CONTEXT</h3> Subsidence has become a major concern with the use of interbody fixation devices for single- or multi-level stabilization of cervical spine. Several studies have reported a higher rate of subsidence with titanium vs PEEK devices. Although a known complication whether or not subsidence affects long-term outcomes is not clear. Traditionally, it was believed that increasing the total bone-implant contact area would result in lower incidence and severity of subsidence. With the advent of advance manufacturing technologies we are able to create implants with advanced structural designs and surface topology that can improve subsidence resistance of the interbody device. <h3>PURPOSE</h3> This study is aimed to evaluate subsidence resistance of two 3D-printed titanium cervical interbody devices of the same footprint size, but with different contact surface topology. <h3>STUDY DESIGN/SETTING</h3> Mechanical testing using foam blocks. <h3>OUTCOME MEASURES</h3> Subsidence rate of different interbody constructs. <h3>METHODS</h3> Two cervical 3D-printed titanium interbody fixation devices were used. The first device had a truss design that spans throughout the entire construct and contains a snowshoe style bone interface and the other was an annular interbody device with a large void at the middle of the cage. Both interbody devices were the same dimensions (17mm x 14mm, width x depth). The Truss-based cervical device had 30% less total implant-to-bone contact area compared to the annular device.To mimic mechanical properties similar to human bone density (osteoporotic through normal), 5, 10, 15 and 20 PCF SawBone® foam blocks were utilized for testing. To mimic clinical subsidence, the interbody device was placed over the foam block and compressive displacement was applied to push the device into the foam substrate at the rate of 5mm/min.The test was repeated 6 times for each block/implant combination. The subsidence load at 1 and 2mm displacement was collected for each test combination. To calculate the modulus/stiffness, the ratio of load (normalized to contact area) to axial compression rate of the cage-only construct was calculated. Two-way ANOVA with Sidak-Bonferroni Posthoc was used for multiple comparisons and analysis of statistical significance. <h3>RESULTS</h3> The truss-based interbody device had significantly greater subsidence resistance compared to the annular device at both 1mm and 2mm subsidence rates (p<0.05) across all density blocks. In foam representing osteoporotic bone (5pcf), the truss cage had subsidence resistance load of 212.3N±5N vs 190N ±6N in the predicate cage at 1mm displacement respectively. The corresponding numbers at in rigid bone (20PCF) were 1290N±27N vs 1174N ±8N. <h3>CONCLUSIONS</h3> The truss device with snowshoe design had metal-to-bone contact area of 30% less than the predicate; nevertheless, the truss device demonstrated significantly better resistance to subsidence for all foam densities including those that mimic osteoporotic bone compared to the same size predicate titanium device. The subsidence resistance of the truss cage, despite its smaller contact area for the same footprint size, may be due to the a more efficient distribution of load across the bone / implant interface where the load is uniformly distributed across more of the interbody footprint. The data suggests that the implant's surface contact topology at the endplate plays a greater role than the overall contact area for resisting subsidence. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

16. Evaluation of the cage subsidence performance of three porous lateral cage designs

<h3>BACKGROUND CONTEXT</h3> Interbody cage subsidence remains a major complication after lumbar spine fusion surgery, particularly in lateral or other procedures that rely on indirect decompression. Porous cages are believed to reduce the risk of cage subsidence. Multiple porous cage designs exist, including 3D printed (3DP) titanium cages with body lattice and microporous endplates, 3DP titanium cages with a truss structure, and PEEK cages with surface porosity. Currently, there is a lack of carefully-controlled biomechanics studies to evaluate their relative performance. <h3>PURPOSE</h3> To evaluate the resistance to subsidence of three representative porous cage designs using ASTM standardized testing methods, as well as clinically relevant dynamic subsidence testing methods. <h3>STUDY DESIGN/SETTING</h3> Mechanical testing using foam blocks. <h3>PATIENT SAMPLE</h3> Three porous cage designs were included: a 3DP cage with stress-optimized body lattice and microporous endplates (stress-optimized titanium cage), a 3DP titanium cage with truss structure (truss titanium cage) and a PEEK cage with surface porosity (porous PEEK cage). All cage designs have the similar dimensions. N=5 testing constructs were used per cage design/loading mode. For titanium cages, one single cage was reused for all constructs. For PEEK cages, a new cage was used in each construct. <h3>OUTCOME MEASURES</h3> For ASTM F2267 static subsidence testing, the block stiffness at the implant-foam interface was reported. The greater the block stiffness, the more force was required to generate the same displacement. For the clinically relevant dynamic subsidence testing, the post-test subsidence displacement was reported, measured as the amount of displacement that each cage sank into the test block surface after a simulated 3-month period of physiologically relevant loading. <h3>METHODS</h3> Static subsidence testing per the ASTM F2267 standard, and novel dynamic subsidence testing, consisting of a physiologically relevant cyclic compressive load, were performed for each cage design to evaluate subsidence performance. Surface-conforming polyurethane foam test blocks that simulated the adjacent vertebral bodies were used in both the static and dynamic subsidence tests. All testing was performed on a calibrated servohydraulic load frame. Testing results were compared between three designs using one-way ANOVA with Bonferroni correction for post-hoc analysis. <h3>RESULTS</h3> In ASTM F2267 static compression testing, the stress-optimized titanium cage showed a significantly greater (27%) block stiffness of 2690.9 ± 92.7 N/mm than that of the truss titanium cage (2118.3 ± 19.9 N/mm, p<0.001), as well as 17.7% greater than that of the porous PEEK cage (2284.7 ± 64.5 N/mm, p=0.001). The porous PEEK cage also significantly outperformed the truss titanium cage (p=0.001) by 8%. In the clinically relevant dynamic subsidence testing, the truss Ti-cage showed the greatest amount of subsidence displacement of 0.141±0.007mm, significantly greater than that of the stress-optimized titanium cage by 153.3% (0.056±0.008mm, p<0.001) and that of the porous PEEK cage by 65.6% (0.085±0.004mm, p<0.001). The stress-optimized titanium cage showed a significantly lower subsidence displacement than that of the porous PEEK (p<0.001) by 34.6%. <h3>CONCLUSIONS</h3> Despite the common conception that porous cage design can reduce the risk of subsidence, the specific design rationale is worthy of rigorous investigation. Under the ASTM F2267 standard static subsidence testing and clinically relevant dynamic subsidence testing conditions, a 3DP titanium cage with a stress-optimized body lattice and microporous endplates showed the best subsidence performance, followed by the porous PEEK cage, and then the 3DP truss titanium cage design. <h3>FDA DEVICE/DRUG STATUS</h3> Modulus XLIF (Approved for this indication), Cohere XLIF (Approved for this indication), LATERAL SPINE TRUSS SYSTEM (Approved for this indication)

Production of tomato seedlings using seeds pelleted with Natrum muriaticum and submitted to saline stress

The development and yield of plants is directly related to the effects of salinity. There are several reports in scientific studies of significant reduction in the growth and production of tomato in soils with high electrical conductivity. The correction or recovery of salinized soils, although technically possible, is a slow and very expensive process, making it necessary to develop new technologies. The objective of this study is to evaluate the production of tomato (Solanum lycopersicon L.) seedlings using seeds pelleted with a homeopathic preparation of Natrum muriaticum (Nat-m) submitted to saline stress. The treatments consisted of the pelletization of tomato seeds with six dynamizations of Nat-m (3cH, 5cH, 7cH, 9cH, 11cH and 13cH). Coated or uncoated seeds (controls) were placed in phenolic foam blocks, kept in plastic trays previously moistened with 50 mM NaCl saline solution (2.922 g.L-1 of NaCl, electrical conductivity = 4.5 dSm-1) and nutrient solution (0.15 dS.m-1) at half the ionic strength, containing 4, 1, 2, 1, 0.5 and 0.5 mmol.L-1 of N, P, K, Ca, Mg and S, and 17.5, 9.5, 10.5, 2, 0.45 and 0.35 mmol.L-1 of Fe, Mn, Zn, Cu and Mo, respectively. The variables evaluated were germination percentage, germination speed index, shoot length, leaf area, number of leaves, root volume, root dry matter, and shoot dry matter. The treatments pelleted seeds/talc Nat-m 5cH and pelleted seeds/talc Nat-m 7cH increased all variables evaluated. They differed statistically from the controls, with a positive response for the development of tomato seedlings under disequilibrium conditions.

Evaluations of pretensioner activation in rear impacts

Objective Occupant kinematics and biomechanical responses are assessed with and without pretensioning of normally seated and out-of-position front-seat occupants in rear sled tests. The results are compared to recent studies. Methods Three series of rear sled tests were conducted at 24 and 40 km/h with a 2001 Ford Taurus. Series I consisted of two sled tests with a lap-shoulder belted 50th Hybrid III in the driver seat. Series II included four sled tests with a lap-shoulder belted 50th Hybrid III in both front seats. Two soft foam blocks were added, one was placed on the chest centerline under the shoulder belt and one on the pelvis under the lap belt providing additional webbing. Series III consisted of 8 runs and 16 ATD tests to assess the effect of pretensioning with out-of-positioned (OOP) occupants. The biomechanical responses were normalized with Injury Assessment Reference Values (IARV) for head, neck and chest. Results The ATD kinematics and biomechanical responses were similar in the yielding phase when the occupant was normally seated with and without pretensioning. The rebound displacement was greater with pretensioning in the 40 km/h tests due to the shoulder belt slipping off the shoulder. The hip displacement was similar, irrespective of pretensioning. All biomechanical responses were below IARVs. The highest response was for lower neck extension. The normalized response was at about 32% for the 24 km/h tests, irrespective of pretensioning. It was up to 59% in the 40 km/h tests with pretensioning. With the OOP occupants, there were no differences in the kinematics and biomechanical response with pretensioning. Conclusions Testing of the effect of retractor pretensioning with out-of-position occupants and additional belt webbing in moderate to high-speed rear sled tests shows no effect on occupant kinematics and biomechanical responses. The displacement of the hips in a rear impact depends on the compliance of the seatback and amount of pocketing, the stiffness of the seat frame limiting rearward rotation, and the dynamic friction between the occupant and the seatback.

Design and Mechanical Evaluation of Sutureless Implants for the Surgery Treatment of Rotator Cuff Tears.

Rotator cuff (RC) tears cause pain and functional disability of the shoulder. Despite advances in suture anchors, there are still reports about the incidence of surgical-related injuries to RC mainly associated with sutures. The purpose of this study was to design and evaluate the mechanical behavior of sutureless implants to repair RC tears. We hypothesized that the implants present mechanical characteristics suitable for the surgical treatment of RC tears as suture anchors. Three different implants (T1, T2, T3) were designed and fabricated with titanium: T1 has two rods and rectangular head; T2 has two rods with a small opening and enlarged rectangular head; and T3 has three rods and a circular head. The implants were fixed in rigid polyurethane foam blocks by a series of blows, and the applied mechanical loads along with the number of blows were quantified. Pullout tests using tapes fixed between the implant head and testing machine grip were conducted until implant failure. The maximum pullout strength and displacement of the implant relative to the rigid foam block were computed. Statistical significance was set at p < 0.05. Owing to its geometric configuration, implant T2 presented the best characteristics related to stability, strength, and ease of insertion. Implant T2 confirms our hypothesis that its mechanical behavior is compatible with that of suture anchors, which could lead to the reduction of RC repair failures and simplify the arthroscopic procedure.

Lateral migration resistance of screw is essential in evaluating bone screw stability of plate fixation

Conventional evaluation of the stability of bone screws focuses on pullout strength, while neglecting lateral migration resistance. We measured pullout strength and lateral migration resistance of bone screws and determined how these characteristics relate to screw stability of locking plate (LP) and dynamic compression plate (DCP) fixation. Pullout strength and lateral migration resistance of individual bone screws with buttress, square, and triangular thread designs were evaluated in polyurethane foam blocks. The screw types with superior performance in each of these characteristics were selected. LP and DCP fixations were constructed using the selected screws and tested under cyclic craniocaudal and torsional loadings. Subsequently, the association between individual screws’ biomechanical characteristics and fixation stability when applied to plates was established. Screws with triangular threads had superior pullout strength, while screws with square threads demonstrated the highest lateral migration resistance; they were selected for LP and DCP fixations. LPs with square-threaded screws required a larger force and more cycles to trigger the same amount of displacement under both craniocaudal and torsional loadings. Screws with triangular and square threads showed no difference in DCP fixation stability under craniocaudal loading. However, under torsional loading, DCP fixation with triangular-threaded screws demonstrated superior fixation stability. Lateral migration resistance is the primary contributor to locking screw fixation stability when applied to an LP in resisting both craniocaudal and torsional loading. For compression screws applied to a DCP, lateral migration resistance and pullout strength work together to resist craniocaudal loading, while pullout strength is the primary contributor to the ability to resist torsional loading.

Mechanical performance of thoracolumbosacral pedicle screw systems: An analysis of data submitted to the Food and Drug Administration

Thoracolumbosacral pedicle screw systems (TPSSs) are spinal implants commonly utilized to stabilize the spine as an adjunct to fusion for a variety of spinal pathologies. These systems consist of components including pedicle screws, rods, hooks, and various connectors that allow the surgeon to create constructs that can be affixed to a wide range of spinal anatomy. During the development and regulatory clearance process, TPSSs are subjected to mechanical testing such as static and dynamic compression bending per ASTM F1717, axial and torsional grip testing per ASTM F1798, and foam block pullout testing per ASTM F543. In this study, design and mechanical testing data were collected from 200 premarket notification (510(k)) submissions for TPSSs submitted to FDA between 2007 and 2018. Data were aggregated for the most commonly performed mechanical tests, and analyses were conducted to assess differences in performance based on factors such as component type, dimensions, and materials of construction. Rod material had a significant impact on construct stiffness in static compression bending testing with cobalt chromium rods being significantly stiffer than titanium rods of the same diameter. Pedicle screw type had an impact on compression bending yield strength with monoaxial screws having significantly higher yield strength as compared to polyaxial or uniplanar screws. Axial and torsional gripping capacities between components and the rods were significantly lower for cross-connectors than the other component types. The aggregated data presented here can be utilized for comparative purposes to aid in the development of future TPSSs.