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[Display omitted] • Porous bone plates with cubic (C), diamond (BCC) and body-centered cubic (CBCC) structures were prepared. • Axial compression, torsional and bending tests were carried out to check the designs' reliability. • CBCC structure with enhanced performance was used with varying rows' and porosities. • Finite element analysis was used to check the biomechanical performance of bone plates. • Increased porosity enhanced the callus volume but displayed poor mechanical performance. The current study investigates the biomechanical performance of porous bone plates augmented with three different cellular lattice structures, e.g., body-centered cube (BCC), simple cube (SC), and the superposition of simple and body-centered cube (SC-BCC) structures. The SC-BCC cellular structures, exhibiting improved torsional, compression, and bending stiffness, were strategically integrated into the bone plates. Configurations ranging from one to three rows, with porosity ranging from 30% to 90%. Increasing the number of rows and porosity maximized the interfragmentary movement at the fracture site. Specifically, SC-BCC configurations with one, two and three rows at 90% porosity demonstrated callus volume improvements of 31.33%, 42%, and 43.2%, respectively, compared with the lowest callus volume observed with SC-BCC at one row and 30% porosity. Regardless of the improved volume, callus stiffness was highest at 30% and 90% porosity levels across all cases, indicating more mature tissue formation in calluses and better physiological load support. High stresses located at 90% porosity, followed by 50% porosity, discouraged their mechanical performance. Therefore, employing 30% porosity configurations with appropriate vertical rows for desired movement is recommended for optimal biomechanical performance. However, 90% porosity may be suitable in scenarios involving minimal forces and restricted patient movement. [ABSTRACT FROM AUTHOR]

Abstract In recent years, biodegradable materials have garnered increasing attention from researchers for use as orthopedic implants. In this study, the fabrication of unidirectional magnesium alloy (AZ31) wire-reinforced poly(lactic acid) (PLA) composites by lamina stacking is presented for bone fracture healing. The tensile and flexural properties of unidirectional composites with wire volume contents of 20%, 30%, 40%, and 50% were measured. Under the simulated human body temperature of 37 °C and accelerated environment of 50 °C, the degradation behaviors of 50-Mg/PLA composite (50% Mg wires by volume) and pure PLA were evaluated by testing water uptake, mass loss, and pH variation. Scanning electron microscopy helped to understand the fracture mode and degradation of magnesium wires inside the composites. Moreover, energy-dispersive spectroscopy confirmed the formation of an apatite layer that mainly consisted of a Ca-P phase deposited on the composite surface and wires, which is essential for bone healing. [ABSTRACT FROM AUTHOR]

Abstract In this paper, finite element analysis of a fractured tibia with a glass/polypropylene composite implant is introduced. A rejection coefficient algorithm (for callus development) that is sensitive to interfragmentary movement is programmed, calibrated (using experimental in vivo statistics), and successfully implemented on a 3D fractured tibia model. A biphasic mechano-regulation algorithm is implemented to verify healing status under five different screw configurations (C1–C5) using glass/polypropylene composite bone plates and the development of tissue phenotypes in calluses is estimated. A 300% increase in circumferential callus volume is obtained when using the composite bone plate. Furthermore, the C5 configuration of the composite bone plate results in a maximum interfragmentary movement of 4.33% on day one with faster and stronger healing through 95% of bone growth during the final day of healing. [ABSTRACT FROM AUTHOR]

Flexible composite implants are receiving increased attention in this modern era of orthopedics for the stabilization of long bone fractures because they facilitate tissue development in calluses. An endochondral ossification process involves generation of calluses, and it is well known that this significantly affects the stabilization and healing of the broken bones. Therefore, the exact configuration of callus formation is highly important for the accurate simulation of bone healing. In this study, finite element analysis was performed to estimate the external callus shape by using the rejection coefficient (RC) algorithm. Regarding the application of a fractured femur by an intramedullary (IM) nail, the bone healing simulation was conducted by employing the biphasic mechano-regulation algorithm according to the fracture type (transverse (0°) and oblique (35°)), fracture location (proximal, medial, and distal ends), and nail property. The simulation results revealed that a glass/polypropylene fabric composite (Twintex [0] 2nT ) IM nail, which has the similar Young’s modulus to the cortical bone, provided the most appropriate bio-mechanical environment for bone healing. [ABSTRACT FROM AUTHOR]

Long bone fractures are primarily treated with internal fixation devices, and intramedullary (IM) nails are the most commonly used. Reamed and unreamed surgical procedures are commonly used to attach IM nails to fractured bones. It is believed that the use of flexible composites contributes to successful fracture healing because of the desirable initial interfragmentary movement (IFM) provided by the material. This finite element study was conducted to understand the influence of initial IFM on the healing process by using various IM nail materials (stainless steel, carbon/epoxy composites (WSN3k [0] 2nT , WSN3k [±30] nT ) and glass/polyprophylene (Twintex [0] 2nT ) composite). Reamed and unreamed IM nails were used to investigate the effects of mesenchymal cell activities, deviatoric strain, and body fluid flow in calluses on bone healing. The results showed that unreamed IM nails promoted healing because of a 40% increase in initial cells supplied to the central callus, compared to reamed nails. The most suitable initial interfragmentary strains (IFS) (18.3% and 6.85%, reamed and unreamed) were provided by the flexible Twintex [0] 2nT IM nail and this induced 38% and 40.33% healing performances by the reamed and unreamed IM nails, respectively. [ABSTRACT FROM AUTHOR]

Complications are common during bone fracture healing owing to incompatibility of the implants. Flexible fibrous composite materials are promising materials that offer excellent biomechanical compatibility. Flexible composite fixation devices provide enough initial fracture stabilization and an adequate environment to promote the desired secondary healing process. Fractures fixed with reamed and unreamed intramedullary (IM) nails exhibit advantages and disadvantages. In this study, the effect of reamed and unreamed IM nails made of stainless steel and various composites (WSN3 k [0] 2nT , WSN3 k [±30] nT , and Twintex [0] 2nT ) on the bone healing process was studied. A finite element model and mechano-regulation algorithm with deviatoric strain and fluid flow were programmed to estimate the healing process. A suitable biophysical environment was predicted for successful bone healing. The Twintex [0] 2nT IM nail contained 19.57% and 33.44% lower stress than that of the stainless steel at day 1, reducing the stress shielding effect. The body weight carried by the bone was 72.8% higher in the Twintex [0] 2nT nail with a maximum relief of 79.8% in stresses relative to the stainless steel IM nail at final day of healing confirming the maximum healing. [ABSTRACT FROM AUTHOR]

[Display omitted] • Three different models of 3D printable titanium cylindrical, pillar and reference metamaterials were prepared. • Design parameters were tuned for axial compression under 20% body weight and examined for torsional and bending tests. • Stable cylindrical metamaterial design was further used into the intramedullary nails to produce 5 ∼ 20% interfragmentary strain at fracture site. • Finite element analysis was used to check the biomechanical performance of metamaterial IM nails for bone union. • Metamaterial IM nail with 10% (S2) interfragmentary strain deformed with only 100 N gave maximum healing performance. Novel metamaterial unit cells with tunable strain were incorporated into titanium intramedullary (IM) nails to overcome problems of dense metallic implants. Three-dimensional (3D) models of cylindrical, pillar, and reference metamaterials were tuned and analyzed for structural authentication. Further, one solid IM nail (S0) and four different cylindrical metamaterial cell IM nails with gap sizes of 0.15 mm, 0.30 mm, 0.45 mm, and 0.60 mm were used to achieve 5% (S1), 10% (S2), 15% (S3), and 20% (S4) strain, respectively, in a 3-mm fracture, to investigate the healing outcomes. The bending stiffness (callus quality) in the S2 metamaterial IM nail increased by 22% between the 7th and 16th iterations, whereas for the S0, S1, S3, and S4 IM nails, the increases were 5.6%, 8.1%, 12.4%, and 9.0%, respectively. The S2 IM nail exhibited the best healing and bending stiffness; however, the S0 IM nail exhibited the worst results. This unique design was customized for different fracture gap sizes according to patient-specific needs. [ABSTRACT FROM AUTHOR]

Dense metallic bone plates often cause stress shielding, delayed healing, or bone non-unions. Therefore, three-dimensional models of partially biodegradable titanium/polyglycolic acid (Ti/PGA) composite cubes with strut thicknesses of 0.33–1.25 mm were designed to achieve different mechanical properties, and compressive simulations of these models were performed to construct stress–strain plots. Finite element models of these plates were assembled with tibial bone fractures using six bicortical screws. Callus volumes were predicted using a rejection coefficient algorithm, and a mechanoregulation algorithm based on deviatoric strain and fluid flow was employed to simulate the healing process. The effective Young's moduli were 12.13–84.6 GPa during the first week and 4.4–80 GPa during the sixth week, while the callus volume increased after reducing the Young's modulus of the bone plate. Thus, the additively manufactured design of biodegradable bone plates can be controlled to achieve the appropriate initial Young's modulus and degradation rate. [ABSTRACT FROM AUTHOR]

Abstract: Nostril stenosis is an uncommon deformity and its aetiology is variable. The shape alteration and nostril asymmetry may have negative aesthetic and functional effects on nostril stenosis patients. Five patients were included in this study and followed up for 24 months; four of these had congenital nostril stenosis and one had an acquired deformity. Alar stent dilators were constructed from measured diameter of the affected nostril/s. The congenital nostril stenosis patients initially received a customised chairside soft nasal dilator (CCSND), which were later replaced with a customised laboratory rigid nasal dilators (CLRND). Treatment outcomes were evaluated using a questionnaire and a visual analogue scale to assess improvements in nostril breathing, comfort, appearance and satisfaction of the treatment provided by both types of dilators. There was improvement in nostril diameter with an average expansion of 7mm and this was stable at the desired diameter. The overall number of stents used to expand the tissues to the desired dimension ranged from 3 to 8 stents. Alar stent therapy is a conservative method to expand nostril tissues and has successfully maintained the nostril diameter for both acquired and congenital stenosis. This improvement in all parameters and the patients’ satisfaction would make the custom-made nostril dilator in particular the CLRND a satisfactory treatment modality for congenital and acquired nostril stenosis. [Copyright &y& Elsevier]

This study introduces innovative hybrid-type (Magnesium wire/poly-lactic acid–glass/polypropylene composite (Mg/PLA–Twintex[0] 2nT) and bio glass fibers/poly-lactic acid–glass/polypropylene composite (BGF/PLA–Twintex[0] 2nT)) partially biodegradable composites for comparison with conventional metallic stainless steel (SS) and fully biodegradable composite bone plates (i.e. Mg/PLA and BGF/PLA), as well as for analyzing their effect towards the healing of fractured healthy and diseased bones. Two different diffusion coefficients are introduced as the biological parameter (0.01 and 0.04 mm2/day) to mimic the blood supply of the diseased and healthy bones. The time-dependent tainted mechanical properties of the degradable composites are implemented to the degradable parts of the bone plates. As hypothesised, we found stress alleviations of 72.36%, 58.82%, 64.82%, and 59.71% in the screws with the diseased bones and alleviations of 84.64%, 72.67%, 77.26%, and 70.8% with the healthy bones in the BGF/PLA, Mg/PLA, BGF/PLA–Twintex[0] 2nT , and Mg/PLA–Twintex[0] 2nT composite bone plates, respectively. These results were then compared with those for the SS plates on the 28th day of healing. The maximum healing performance was predicted for the hybrid composites as opposed to the degradable and SS implants, thereby confirming the superiority of the proposed composites. Image 1 • Novel partially bio-degradable hybrid composite bone implants were introduced. • Finite element analysis study coupled with Mechano-bioregulation was performed. • Healthy and diseased blood supply was considered during diaphyseal tibial fractures. • Performance of each implant considering tissue volume and development was studied. • Hybrid composite bone implants provided the best healing performance. [ABSTRACT FROM AUTHOR]

We fabricate biodegradable hybrid composites of unidirectional magnesium alloy wires and bioactive glass (BG) fibres inserted as reinforcements inside a polylactic (PLA) matrix by utilising lamina stacking process. The degree of mechanical reinforcement that can be achieved through this hybridisation is determined by examining various composite combinations by volume, i.e. the use of 20% Mg and 30% Mg wires with the BG fibre content varying from 0% to 30%. BG fibre addition up to ~10% by volume affords high tensile strength, which remain nearly constant upon subsequent fibre addition. Hybrids with 30% Mg content exhibit tensile strengths comparable with that of the cortical bone; thus, we perform a seven-day tensile degradation study of the composites in phosphate-buffered saline (PBS) to determine their behaviour under wet conditions as function of immersion time at 37 °C. The least amount of BG fibres (10%) exhibits greater retention strength in PBS than other combinations. [ABSTRACT FROM AUTHOR]

Micro-movements are considered to have strong influence on the secondary healing process of fractured long bones, however, the translational shear movement is assumed to have a negative effect on the healing of such fractures. Numerical simulations were carried out with initially applied individual and combined, axial and shear displacements (ranging 0.1 mm to 1.0 mm for a 3 mm fracture at day 1) for a tibial fracture fastened by flexible composite prostheses. The best individual case of healing was seen with an initial axial displacement of 0.1 mm (86% reduced movement compared to the worst, 1.0 mm translational movement) while in combined cases, 0.1–0.1 mm (axial-shear combination) gave the best healing results (0.000157 mm) at day 56. Moreover, using composite intramedullary (IM) nail and bone plate as a superior implant resulted in 157.81% and 201% improved callus volumes with a promising bending stiffness of 20.62 and 19.03 Nm/θ, respectively, at day 154. But the excessive shear movement for the initial 4–6 weeks using an IM nail delayed fracture healing. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Traditionally, high stiffness hip prostheses are associated with aseptic loosening. Hence, the effects of stiffness, coating length, and interference press fit on load sharing and micro-movements are investigated for a better understanding from a mechanical perspective. A simplified 3D model of the femur and prostheses composed of cobalt chrome (CoCr), titanium (Ti), and glass/polypropylene (Twintex [0] 2nT) composite are constructed. Three interference fits corresponding to 5, 25, and 50 µm are used with half, three-quarter, and full lengths of coating that are used to assemble the prostheses with bones to investigate micro-movements at the bone-prosthesis interfaces, interfacial failure, and stress transfer to the bone. The reaction forces of body weight and muscular forces in the femur are used to simulate the FE model. The results indicate that the CoCr and Ti prostheses exhibit low micro-movements at the proximal end and high micro-movements at the distal end and vice versa for the Twintex [0] 2nT composite prosthesis. Uniformity of stress transfer to the bone along the prosthesis efficiently increases with increases in the coating lengths and interference press fits for all the cases. A fully coated length of Twintex [0] 2nT composite prosthesis with a 50-µm interference press fit provides the most efficient load sharing and stress transfer to the bone and micro-movements at the bone–prosthesis interface. [ABSTRACT FROM AUTHOR]

Titanium porous cellular microstructures are commonly used in bone mimetic implants. The orientations of the internal strut architectures of these microstructures affect the mechanical performance under various loads; however, poor architectural designs may result in their failure. Three-dimensional (3D) finite element models of cubic, diamond, and body-centered cubic (BCC) geometries were constructed with 1 – 4 numbers of unit cells and 4–10-mm unit cell size. Mechanical testing of the finite models of the cubic, diamond, and BCC structures with porosities of 20–90% was performed under compression, bending, and torsional loads. The BCC structure showed moderate and relatively isotropic mechanical properties compared with those of the diamond and cubic structures. A design space for a BCC porous structure with a porosity of 40–65% was estimated to model a complete porous stem to mimic the bone properties. Furthermore, the stems with the determined porous mechanical properties of the BCC microstructures with 20–90% porosities were tested under physiological loading conditions. It was found that a porosity of 47.3% of the BCC structure exhibits the closest stiffness (469 N/mm) to an intact bone (422 N/mm). This was predicted by our suggested design space of the porosity. [ABSTRACT FROM AUTHOR]

Radial bone shaft fractures are commonly treated with bone plates. Flexible bone plates made of fiber-reinforced polymer composites have advantages over complications, such as stress shielding, corrosion, harmful ions, X-ray artifacts, resulting from metallic bone plates. Postoperative rehabilitation exercise is an important factor influencing the healing outcomes of radial bone fractures. A finite element model of radial shaft fracture was treated with Twintex [0] 2nT composite bone plate and six stainless steel bicortical screws. Axial compression (10 N), bending moment (0.1 Nm), and torsion (0.1 Nm) as single, combined, and alternative loads (10% loads of daily activities) were used in the finite element study. A mechano-regulation algorithm based on deviatoric strain was used to predict the healing of bone fractures. The healing performance and bending stiffness were evaluated and compared to estimate the healing status of bone fractures. The best exercise mode, which gave the highest healing performance (68%) and bending stiffness (89%), was suggested. These results can be successfully utilized for the design of healing devices for the rehabilitation of fractured bones. [ABSTRACT FROM AUTHOR]

Metallic implants with high Young's moduli are used to treat long-bone fractures; however, they cause stress shielding and prevent bones from attaining their original strength. Thus, flexible composite implants have been designed to enhance tissue development without stress shielding. Herein, 3D-printed composite bone plates with different Young's moduli were designed, and their effects on 3D models of long-bone fractures were analysed. A biphasic mechano-regulation algorithm, coupled with cell diffusion and tissue phenotype activities, was developed using a Python script to analyse bone-healing patterns for 112 days after surgery. A composite bone plate (Young's modulus, 40 GPa) showed the best healing performance (100%), compared with a stainless-steel bone plate (70%). Further, cell and tissue development using bone plates with different Young's moduli under different loading conditions are presented. [Display omitted] [ABSTRACT FROM AUTHOR]

• Fatigue study of biodegradable magnesium wire–polylactic acid (Mg/PLA) composites. • Simulated body fluid conditions used, accelerating pitting corrosion. • Mg/PLA composites implants found safe under physiological loading conditions. • Experiment coupled Finite Element Analysis of bone healing used. • Fatigue life can further be improved by using non-degradable material near holes. This study investigated the fatigue life of biodegradable magnesium wire–polylactic acid (Mg/PLA) composite implants during the initial patient rehabilitation period under physiological loads through experimental and finite element methods. Under a simulated body fluid condition, the fatigue life was observed to be completely affected by material degradation, which accelerated the pitting corrosion of the composite bone plate. The mechanical behaviour of Mg/PLA composite bone plate was investigated under physiological loading conditions for the case of a tibial fracture with a 3 mm gap. A three-point bending fatigue test setup was employed to validate the fatigue characteristics of composite specimens. Finally, to alleviate the generated stress and enhance the fatigue resistance of fully biodegradable composites, a hybrid composite bone plate is proposed. At the screw section, the hybrid composite is partly composed of a comparatively more fatigue-safe non-degradable glass–polypropylene composite, which improves the healing performance of the fractured tibia. [ABSTRACT FROM AUTHOR]