Mechanical Behaviour of Aluminium-Timber Composite Connections with Screws and Toothed Plates

This paper presents an investigation of the load-slip behaviour of aluminium-timber composite connections. Toothed plates with bolts are often used for connecting timber structural members with steel structural members. In this paper, toothed plates (C2-50/M10G, C2-50/M12G or C11-50/M12) have been used as reinforcement in aluminium-timber screwed connections for the first time. The push-out test specimens consisted of laminated veneer lumber slabs, aluminium alloy beams, and hexagon head wood screws (10 mm × 80 mm and 12 mm × 80 mm). Of the specimens, 12 additionally had toothed plates as reinforcement, while 8 had no reinforcement. The load carrying-capacity, the mode of failure and the load-slip response of the strengthened and non-strengthened screwed connections were investigated. The use of toothed plate connectors was found to be effective in increasing the strength of aluminium-timber composite connections and ineffective in improving their stiffness. The examined stiffness and strength of the connections can be used in the design and numerical modelling of aluminium-timber composite beams with reinforced screwed connections.

Analysis of the bamboo construction process in the architecture of Leiko Motomura and Simón Vélez

The interest in the use of natural materials by construction professionals has been growing as the concern with designing buildings with low environmental impact arises. For this reason bamboo is an excellent choice, as this material has a high resistance parallel to the fibers, is light and has a great capacity to incorporate CO². Given the context described above, this article aims to analyze the constructive techniques in bamboo culms in two works of architectural relevance: Max Feffer Cultural Center (Brazil) and Casa Serra Grande (Brazil), by architects Leiko Motomura and Simón Vélez. For this, field visits were made for a better understanding of bamboo connections, analysis of photographs, files, 3D models and bibliographical research regarding the material. The study helps to understand and reflect on the constructive components of bamboo in architectural projects, highlighting the association between the traditional elements of fittings, associated with the technology available today, such as the grout associated with screws, clamps and spacers.

Fenton Syndrome: Diagnosis and Treatment with 3D-Printed Models. An Unusual Case Report

Scaphocapitate syndrome, also called Fenton syndrome, is a rare, complex condition. Since it is often missed on initial evaluation, it is a diagnostic challenge. A high index of suspicion is required for early surgical treatment, avoiding future palliative surgery or sequelae. Cutting-edge diagnostic technologies, including three-dimensional printed models, are becoming essential tools, enabling the treatment of complex trans-scaphocapitate fracture-dislocations using open reduction and internal fixation with screws, with excellent outcomes at a 12-month follow-up period.

Temporal Changes in Reverse Torque of Locking-Head Screws Used in the Locking Plate in Segmental Tibial Defect in Goat Model

The objective of this study was to evaluate changes in peak reverse torque (PRT) of the locking head screws that occur over time. A locking plate construct, consisting of an 8-hole locking plate and 8 locking screws, was used to stabilize a tibia segmental bone defect in a goat model. PRT was measured after periods of 3, 6, 9, and 12 months of ambulation. PRT for each screw was determined during plate removal. Statistical analysis revealed that after 6 months of loading, locking screws placed in position no. 4 had significantly less PRT as compared with screws placed in position no. 5 (p < 0.05). There were no statistically significant differences in PRT between groups as a factor of time (p > 0.05). Intracortical fractures occurred during the placement of 151 out of 664 screws (22.7%) and were significantly more common in the screw positions closest to the osteotomy (positions 4 and 5, p < 0.05). Periosteal and endosteal bone reactions and locking screw backout occurred significantly more often in the proximal bone segments (p < 0.05). Screw backout significantly, negatively influenced the PRT of the screws placed in positions no. 3, 4, and 5 (p < 0.05). The locking plate-screw constructs provided stable fixation of 2.5-cm segmental tibia defects in a goat animal model for up to 12 months.

Experimental Drillable Magnesium Phosphate Cement Is a Promising Alternative to Conventional Bone Cements

Clinically used mineral bone cements lack high strength values, absorbability and drillability. Therefore, magnesium phosphate cements have recently received increasing attention as they unify a high mechanical performance with presumed degradation in vivo. To obtain a drillable cement formulation, farringtonite (Mg3(PO4)2) and magnesium oxide (MgO) were modified with the setting retardant phytic acid (C6H18O24P6). In a pre-testing series, 13 different compositions of magnesium phosphate cements were analyzed concentrating on the clinical demands for application. Of these 13 composites, two cement formulations with different phytic acid content (22.5 wt% and 25 wt%) were identified to meet clinical demands. Both formulations were evaluated in terms of setting time, injectability, compressive strength, screw pullout tests and biomechanical tests in a clinically relevant fracture model. The cements were used as bone filler of a metaphyseal bone defect alone, and in combination with screws drilled through the cement. Both formulations achieved a setting time of 5 min 30 s and an injectability of 100%. Compressive strength was shown to be ~12–13 MPa and the overall displacement of the reduced fracture was <2 mm with and without screws. Maximum load until reduced fracture failure was ~2600 N for the cements only and ~3800 N for the combination with screws. Two new compositions of magnesium phosphate cements revealed high strength in clinically relevant biomechanical test set-ups and add clinically desired characteristics to its strength such as injectability and drillability.

Incidence of Loss of Reduction After Open Reduction Internal Fixation of Metacarpal Shaft Fractures

Background This study compared the incidence of loss of reduction (LOR) between metacarpal fractures fixed with screws alone and those fixed with plates and screws. Secondary aims included identifying patient or fracture characteristics associated with increased risk of LOR. Methods We retrospectively reviewed 138 metacarpal fractures in 106 patients treated with open reduction internal fixation with screws (60 fractures) or plates and screws (78 fractures) with a mean radiographic follow-up of 50 days for evidence of LOR. We compared the incidence of LOR between the screw and plate groups using a χ2 test. We performed logistic regression analysis to determine whether patient age, sex, metacarpal location (index, long, ring, small), the presence of multiple metacarpal fractures, or fracture pattern were associated with increased incidence of LOR. Results Loss of reduction occurred in 19 (13.8%) of 138 fractures, with no statistically significant difference between lag screw (7 of 60, 11.6%) and plate fixation (12 of 78, 15.4%). Neither fracture pattern nor the presence of multiple metacarpal fractures was associated with an increased incidence of LOR, but patients experienced a 7% increase in the risk of LOR for each additional year of age. Loss of reduction occurred most frequently in index metacarpal fractures (4 of 12, 33%), although this did not reach statistical significance. Conclusions We found no difference in LOR incidence between lag screw fixation and plate fixation. The overall incidence of LOR was higher in this study than previously reported and increased with increasing patient age.