Category:
Midfoot/Forefoot; Basic Sciences/Biologics
Introduction/Purpose:
Traditional hardware for first MTP arthrodesis procedures are typically made from stainless steel or titanium. While ...postoperative non-weightbearing protocols have enabled successful results with these devices, they are still prone to permanent deformation and associated plantar gapping/joint misalignment following excessive prefusion loading (e.g., patient falling). By leveraging the material properties of NiTiNOL, sustained dynamic compression (SDC) staples have been designed to recover their initial shape after large loading events. As such, implementation of these SDC staples may produce first MTP arthrodesis constructs more robust to early loading events, potentially decreasing patient immobility times and reducing incidences of postoperative joint misalignment. The goal of this study was to characterize the biomechanical performance of first MTP.
Methods:
Solid foam MTP replicas underwent simulated arthrodesis using one of eight constructs (N=6 replicates within each group). Groups consisted of: (1) double 2-leg staple, (2) 4-leg inline staple, (3) 4-leg Y staple, (4) 4-leg inline staple & screw, (5) 4- leg Y staple & screw, (6) double screw, (7) locking plate, and (8) locking plate & screw (Figure A-C). Simulated loading was applied to the samples 23mm distal to the joint line in the dorsiflexion direction. Samples underwent 1,000 nondestructive cycles of loading between 5-15N (replicative of postoperative walking in a recovery boot), followed by simulated overloading (destructive test) that applied 10mm of displacement at the loading point. Plantar gapping was measured using photogrammetry techniques throughout the entire testing protocol. Data were analyzed using a one-way ANOVA (α=0.05) with Dunnett’s post hoc test using the ubiquitous plate and screw group as the control.
Results:
Plantar gapping at simulated walking revealed significantly increased plantar gapping in the locking plate (P=.001) and double 2-leg staple (P .75, Figure D). The double screw and Y staple & screw groups exhibited significantly decreased gapping at 10mm extension as compared to the locking plate & screw group (P=.030 and .049, respectively). All SDC NiTiNOL constructs (both with and without static devices) recovered plantar gapping post-failure, with plantar gaps ≤ 0.29 mm, whereas the locking plate & screw construct group had a mean post-failure plantar gap of 0.85 mm (P <.001, Figure E).
Conclusion:
These data illustrate the ability of newer SDC staples to reduce plantar gapping following excessive pre-fusion loading events as compared to standard plate & screw constructs. Specifically, the four-legged Y staple & static screw construct exhibited similar plantar gapping in simulated walking and nearly eliminated permanent plantar gapping following the excessive pre-fusion loading event. While these biomechanical data do not measure clinical fusion performance, they indicate the suitability of these products in generating equivalent construct stability as compared to the currently used locking plate and screw combination, justifying future clinical studies aimed at assessing their effectiveness.
Data analysis was performed using One-way repeated measures ANOVA with Tukey’s post-hoc correction for multiple comparisons. The SWE stiffness of the repaired supraspinatus tendon increased in a ...curvilinear fashion, healing in 6-months post-arthroscopic rotator cuff repair. ...patients who have undergone rotator cuff repair should not return to activities without restriction until at least 6-months post-operatively. From 6-months, deltoid muscle elastographic stiffness increased, corresponding to the time when the repaired supraspinatus tendon had healed and patients were instructed to return to activities without restriction.
Abstract To address the current problems of low accuracy and poor reliability of the discrete element model of cotton stalks, as well as the difficulty of guiding the design and optimization of the ...equipment through simulations, the discrete element modeling and physical-mechanical tests of cotton stalks in machine harvested film-stalk mixtures are carried out. The peak tensile force $$F_{\rm j}^{\max }$$ F j max , the peak pressure $$F_{\rm y}^{\max }$$ F y max , the peak bending force $$F_{\rm w}^{\max }$$ F w max , the peak shear force $$F_{\rm j}^{\max }$$ F j max , and the force-displacement ( F – x ) curves of cotton stalks are obtained from the physical tests. The discrete element model of double-layer cotton stalks based on the flat-joint model is established with the PFC $$^{\rm 3D}$$ 3 D software. The $$F_{\rm y}^{\max }$$ F y max is taken as the response value, and the microscopic parameters of the cotton stalk model are used as the test factors, then the Plackett–Burman test, the steepest climb test, and the Box–Behnken test are sequentially designed using Design-Expert software. The second-order regression model describing the relationship between the $$F_{\rm y}^{\max }$$ F y max and the microscopic parameters is established. The optimal parameter combinations of the microscopic parameters are obtained, and then they are utilized to construct the compression, bending, and shear models of cotton stalks and to carry out the validation tests. The results confirm that the established discrete element model could accurately characterize the biomechanical properties of cotton stalks and that the parameter calibration method is reasonable, which could provide a reference for the discrete element modeling of cotton stalks and other stalks, and also offer a theoretical basis for the research of the crushing and separation mechanism of the film-stalk mixtures and the development of the equipment.
The potential of biomechanics for improving human health and performance is well established in many parts of the world. However, across most of Africa, biomechanics remains relatively ...underdeveloped. The discussion around biomechanics in the continent has increased in recent times and young African scientists are pursuing career opportunities in biomechanics-related fields within Africa and in other parts of the world. New institutions and programmes that focus on biomechanics teaching and research are also starting up around the continent. The advent of the National Biomechanics Day event, formation of the first formal biomechanics society in South Africa, along with many collaborations with relevant stakeholder organizations around the world underpin the expansion of biomechanics in Africa. This article aims to summarize the current state and describe aspirations for the future of biomechanics in Africa.
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