Biomechanical effects of cross-pin's diameter in reconstruction of anterior cruciate ligament - A specific case study via finite element analysis

For anterior cruciate ligament reconstruction (ACL-R), one of the crucial aspects of treatment is the fixator selection that could provide initial graft fixation post-operatively. Literature on biomechanical stabilities of different sizes of fixators as femoral graft fixation is limited. Therefore, this study aims to analyse the influence of different diameters of cross-pins on the stability of graft fixations after ACL-R via finite element analysis (FEA). In the methodology, three-dimensional (3D) models of three different diameters of cross-pins were developed, of which anterior tibial loads (ATL) were applied onto the tibia. From the findings, the cross-pin with a smaller diameter (4 mm) provided optimum stability than larger diameter cross-pins, whereby it demonstrated acceptable stresses at the fixators (both cross-pin and interference screw) with a different percentage of 28%, while the stresses at the corresponding bones were favourable for osseointegration to occur. Besides, the strains of the knee joint with 4 mm diameter cross-pin were also superior in providing a good biomechanical environment for bone healing, while the recorded strain values at fixators were comparable with a larger diameter of cross-pins without being inferior in terms of deformation. To conclude, the cross-pin with 4 mm diameter depicted the best biomechanical aspects in graft fixation for ACL-R since it allows better assistance for the osseointegration process and can minimise the possibility of the breakage and migration of fixators. This study is not only useful for medical surgeons to justify their choices of pin diameter to treat patients, but also for researchers to conduct future studies.

Effects of badminton insole design on stress distribution, displacement and bone rotation of ankle joint during single-leg landing: a finite element analysis

Previous research has reported that up to 92% of injuries amongst badminton players consist of lower limb, whereby 35% of foot fractures occurred at the metatarsal bone. In sports, insoles are widely used to increase athletes' performance and prevent many injuries. However, there is still a lack of badminton insole analysis and improvements. Therefore, this study aimed to biomechanically analyse three different insole designs. A validated and converged three-dimensional (3D) finite element model of ankle-foot complex was developed, which consisted of the skin, talus, calcaneus, navicular, three cuneiform, cuboid, five metatarsals and five phalanges. Three existing insoles from the market, (1) Yonex Active Pro Truactive, (2) Victor VT-XD 8 and (3) Li-Ning L6200LA, were scanned using a 3D scanner. For the analysis, single-leg landing was simulated. On the superior surface of the skin, 2.57 times of the bodyweight was axially applied, and the inferior surface of the outsole was fixed. The results showed that Insole 3 was the most optimum design to reduce peak stress on the metatarsals (3.807 MPa). In conclusion, the optimum design of Insole 3, based on the finite element analysis, could be a justification of athletes' choices to prevent injury and other complications.

Stress Distributions and Micromovement of Fragment Bone of Pilon Fracture Treated With External Fixator: A Finite Element Analysis

Osteoporosis and osteoarthritis are common pathological problems of the human bone tissue. There are some cases of pilon fractures associated with these 2 pathological conditions. In terms of treatment, for a normal and healthy bone with pilon fracture, the use of the Delta external fixator is a favorable option because it can allow early mobilization for patients and provide stability for the healing process. However, the stability of the external fixator differs when there is low bone stiffness, which has not been previously investigated. Therefore, this study was conducted to determine the stability of the external fixator to treat pilon fracture associated with osteoporosis and osteoarthritis, particularly to differentiate the stress distribution and micromovement of fracture fragment. Three-dimensional finite element models of the ankle and foot bones were reconstructed based on the computed tomography datasets. The bones consisted of 5 metatarsal, 3 cuneiform, and 1 each of cuboid, navicular, calcaneus, talus, fibula, and tibia bones. They were assigned with linear isotropic behavior. The ankle joint consisted of ligament and cartilage, and they were assigned with the use of linear links and the Mooney-Rivlin model, respectively. During simulation of the gait cycle, 70 N and 350 N were applied axially to the tibia bone to represent the swing and stance phases, respectively. The metatarsal and calcaneus bones were fixed to prevent any movement of the rigid body. The study found that the greatest von Mises stress value was observed at the pin-bone interface for the osteoporosis (108 MPa) model, followed by the osteoarthritis (87 MPa) and normal (44 MPa) models, during the stance phase. For micromovement, the osteoporosis model had the largest value at 0.26 mm, followed by the osteoarthritis (0.09 mm) and normal (0.03 mm) models. In conclusion, the greatest magnitudes of stress and micromovement were observed for the osteoporosis bone and extra care should be taken to treat pilon fracture associated with this pathological condition.

Biomechanical analysis of conventional and locking compression plate for treating fibula fracture: A finite element study

1) Background: Due to questionable effectiveness of malleolar fracture fixation, biomechanical study was conducted to compare the stability of One Third Tubular (OTT) Plate and Locking Compression Plate (LCP); 2) Methods: CT image of bone was used to develop 3D bone model while the plate was constructed in Solidwork with varied number of screws. Further, finite element study was conducted for both models where the bone and plate were defined as homogenous and isotropic material properties; 3) Results: For LCP, the highest VMS observed at the plate for 3 screws was 484 MPa, whereas for 5 screws plate was 667 MPa. Meanwhile, for OTT, the highest VMS at plate was observed for 3 screws was 300.5 MPa, whereas for 5 screw plate was 127.5 MPa. 4) Conclusion: Based on the results, it can be noted that the usage of 3 screw causing a lower VMS at plate compared to 5 screws. However, the relation is only valid for LCP. On the other hand, for OTT, 5-screw constructs giving a low VMS than 3-screw constructs. It can be concluded that the optimum stabilities of OTT and LCP were found at 5 screws and 3 screws, respectively.

Augmented reality experimentation on oxygen gas generation from hydrogen peroxide and bleach reaction

The appreciation and understanding of gas generation through processes is vital in biochemical education. In this work, an augmented reality tool is reported to depict the redox reaction between hydrogen peroxide and sodium hypochlorite solutions, two ubiquitous oxidizing agents, to create oxygen, a combustible gas. As it operates out of smartphones or tablets, students are able to conduct the exercise collaboratively, respond in a manner similar to an actual physical experiment, and able to depict the oxygen volume changes in relation to the volume of hydrogen peroxide of different concentrations used. The tool offers to help students acquire bench skills by limiting handing risks and to mitigate possible student anxiety on handling chemical materials and implements in the laboratory. The feedback received from Year 11 and 12 high school student participants in an outreach exercise indicate the overall effectiveness of this tool. © 2018 by The International Union of Biochemistry and Molecular Biology, 46(3):245-252, 2018.