Study of a constrained finite element elbow prosthesis: the influence of the implant placement

Background: The functional results of total elbow arthroplasty (TEA) are controversial and the medium- to long-term revision rates are relatively high. The aim of the present study was to analyze the stresses of TEA in its classic configuration, identify the areas of greatest stress in the prosthesis–bone–cement interface, and evaluate the most wearing working conditions. Materials and methods: By means of a reverse engineering process and using a 3D laser scanner, CAD (computer-aided drafting) models of a constrained elbow prosthesis were acquired. These CAD models were developed and their elastic properties, resistance, and stresses were studied through finite element analysis (finite element method—FEM). The obtained 3D elbow-prosthesis model was then evaluated in cyclic flexion–extension movements (> 10 million cycles). We highlighted the configuration of the angle at which the highest stresses and the areas most at risk of implant mobilization develop. Finally, we performed a quantitative study of the stress state after varying the positioning of the stem of the ulnar component in the sagittal plane by ± 3°. Results: The greatest von Mises stress state in the bone component for the 90° working configuration was 3.1635 MPa, which occurred in the most proximal portion of the humeral blade and in the proximal middle third of the shaft. At the ulnar level, peaks of 4.1763 MPa were recorded at the proximal coronoid/metaepiphysis level. The minimum elastic resistance and therefore the greatest stress states were recorded in the bone region at the apex of the ulnar stem (0.001967 MPa). The results of the analysis for the working configurations at 0° and 145° showed significant reductions in the stress states for both prosthetic components; similarly, varying the positioning of the ulnar component at 90° (− 3° in the sagittal plane, 0° in the frontal plane) resulted in better working conditions with a greater resulting developed force and a lower stress peak in the ulnar cement. Conclusion: The areas of greatest stress occur in specific regions of the ulnar and humeral components at the bone–cement–prosthesis interface. The heaviest configuration in terms of stresses was when the elbow was flexed at 90°. Variations in the positioning in the sagittal plane can mechanically affect the movement, possibly resulting in longer survival of the implant. Level of evidence:

CO-PARENTING FACTORS THAT CONTRIBUTE TO ACADEMIC SUCCESS

This study assessed factors contributed from parents who live in two different households and that lead to academic success. Data were collected from undergraduates enrolled in a Midwestern satellite university. Academic success was defined by university enrollment, grade point average, and standardized testing scores. Co-parenting factors that were hypothesized to lead to academic success included the distance between parents homes (which further influenced time spent with the child, participation in child‘s activities, and participation in decision making) and financial stability (which also influenced participation in decision making and the level of conflict within the family). The original structural equation model revealed that the relationship linking the distance between homes and the time spent with the child was accurately described. Added to the model, after the Lagrange test, was a path from finances to participation in child‘s activities and time spent with the child. The financial stability of a family predicted the participation of the non-custodial parent in the child‘s activities, in the decision-making for the child, conflict, and the time spent with the child. Implications for practitioners who work with families with co-parenting responsibilities are discussed

CO-PARENTING FACTORS THAT CONTRIBUTE TO ACADEMIC SUCCESS

This study assessed factors contributed from parents who live in two different households and that lead to academic success. Data were collected from undergraduates enrolled in a Midwestern satellite university. Academic success was defined by university enrollment, grade point average, and standardized testing scores. Co-parenting factors that were hypothesized to lead to academic success included the distance between parents homes (which further influenced time spent with the child, participation in child‘s activities, and participation in decision making) and financial stability (which also influenced participation in decision making and the level of conflict within the family). The original structural equation model revealed that the relationship linking the distance between homes and the time spent with the child was accurately described. Added to the model, after the Lagrange test, was a path from finances to participation in child‘s activities and time spent with the child. The financial stability of a family predicted the participation of the non-custodial parent in the child‘s activities, in the decision-making for the child, conflict, and the time spent with the child. Implications for practitioners who work with families with co-parenting responsibilities are discussed

The Occurrence of Microplastics in Donax trunculus (Mollusca: Bivalvia) Collected along the Tuscany Coast (Mediterranean Sea)

Microplastics (MPs) (0.1 μm–5 mm particles) have been documented in oceans and seas. Bivalve molluscs (BMs) can accumulate MPs and transfer to humans through the food chain. BMs (especially mussels) are used to assess MPs’ contamination, but the genus Donax has not been thoroughly investigated. The aim of this study was to detect and characterize MPs in D. trunculus specimens collected along the Tuscan coast (Italy), and to assess the potential risk for consumers. The samples (~10 g of tissue and intervalval liquid from 35 specimens) were digested using a solution of 10% KOH, subjected to NaCl density separation, and filtered through 5 μm pore-size filters. All items were morphologically classified and measured, and their mean abundance (MA) was calculated. Furthermore, 20% of them were analyzed by Raman spectroscopy and, based on the obtained results, the MA was recalculated (corrected MA) and the annual human exposure was estimated. In the 39 samples analyzed, 85 items fibers (n = 45; 52.94%) and fragments (n = 40; 47.06%) were found. The MA was 0.23 ± 0.17 items/grww. Additionally, 83.33% of the items were confirmed as MPs (polyethylene and polyethylene terephthalate). Based on the correct MA (0.18 MPs/grww), D. trunculus consumers could be exposed to 19.2 MPs/per capita/year. The health risk level of MPs was classified as level III (moderate)

Microsurgery and external fixation in orthoplastic reconstruction of tibial injuries

Background Orthoplastics is a relatively new approach to lower limb reconstruction, where an integration of both plastic and orthopedic expertise is required, together with the availability of well-equipped facilities. Acute shortening and long-term frames for lengthening are generally considered alternatives to length preservation and soft tissue microsurgical reconstruction, but an integration of external fixation and reconstructive microsurgery is gaining an increasing role with refinements of joint approaches. Material and methods Data on sixteen patients who underwent microsurgical lower limb reconstruction and external fixation with an orthoplastic approach, following acute or chronic tibial injury, were retrospectively reviewed. All patients presented a post traumatic soft tissue defect associated with a Gustilo III tibial fracture or a tibial septic pseudarthrosis. Data on type and timing of bone and soft tissue reconstruction, outcomes, complications and need for re-operation were extrapolated and compared to an historic group of patients treated with an orthopedic-based approach. Results In the orthoplastic group, soft tissues were reconstructed with an ALT flap in most cases; a muscle-sparing VL or ALT-VL chimeric flap was necessary in cases with a very extensive defect. In the orthopedic group, soft tissues were left to heal by second intention or patients were lately referred to plastic surgeons. Statistical comparison between the two groups has showed significant differences on the following data: Time for soft tissue healing, time to bone union, number of reinterventions, post-operative deep infection rate, time to return to work. Conclusion The orthoplastic approach to complex leg defects yields shorter treatment time and better functional results compared to the orthopedic-based approach. External fixation and microsurgical reconstruction are not necessarily alternative procedures but can integrate in an orthoplastic path to address at best both soft tissue and bone reconstruction