Estimation of mass apparent density and Young's modulus of femoral neck-head region

Model Properties and Clinical Application in the Finite Element Analysis of Knee Joint: A Review

The knee is the most complex joint in the human body, including bony structures like the femur, tibia, fibula, and patella, and soft tissues like menisci, ligaments, muscles, and tendons. Complex anatomical structures of the knee joint make it difficult to conduct precise biomechanical research and explore the mechanism of movement and injury. The finite element model (FEM), as an important engineering analysis technique, has been widely used in many fields of bioengineering research. The FEM has advantages in the biomechanical analysis of objects with complex structures. Researchers can use this technology to construct a human knee joint model and perform biomechanical analysis on it. At the same time, finite element analysis can effectively evaluate variables such as stress, strain, displacement, and rotation, helping to predict injury mechanisms and optimize surgical techniques, which make up for the shortcomings of traditional biomechanics experimental research. However, few papers introduce what material properties should be selected for each anatomic structure of knee FEM to meet different research purposes. Based on previous finite element studies of the knee joint, this paper summarizes various modeling strategies and applications, serving as a reference for constructing knee joint models and research design.

Feasibility study of femur bone with continuum model

It is known that the geometric structures of bones are very complex. This has made researchers unable to model them with the continuum approach and suffice to model them with simulation or experimental tests. Undoubtedly, provide a simple and accurate continuum model for studying bones is always desirable. In this article, as the first serious endeavour, a suggested beam model is investigated to see whether it is suitable for modelling femur bones or not. If this model gives an acceptable answer, it can be a link to the continuum theories for beams. In other words, the approximated beam model can be formulated with continuum approach to study femur bone. For feasibility study of the approximated model for femur bones, both static and dynamic analysis of them are investigated and compared. It is found that in most cases for vibration analysis, the suggested model has acceptable results but in static analysis, the mean difference between the results is about 16%. This research is hoped to be the first serious step in this category.

Ultrasonic shock wave generated by laser as an alternative method to find different bone properties

Biological materials have been increasingly examined in recent years. What motivates such studies is the need for a comprehensive mechanistic, structural link that will aid future designs of manufactured analogs. Non-destructive laser testing (NDLT) describes the non-damaging material testing method employing a laser. They deny damaging or inducing helpfulness to give information about a material or component and find their physical properties; the experimental study examined bone's physical characteristics for two types (dental and rib) of sheep that is 1 year old. The classical methods depends on microtensile and microhardness compared with NDLT data depending on studying images in high-resolution optical microscopy by studying the laser effect induced by different energies of nanosecond Nd:YAG laser. In laser-induced shock peening (LSP), the forward velocity of the shock wave depends on the bone type related to the rate of ionization of the excited atoms. It noted that the shock measurements at laser intensity 14 GW/cm2 show that the peak pressures typically are 3.1 and 4.1 GPa for dental and rib bones, respectively. The particle velocity for the rib is 962 m/s. In contrast, dental bones are 752 m/s, the shock force for rib bones is 1.9 kN, while dental force is 2 kN. Mechanical properties show that the Young modulus by NDLT is 8.7 GPa for rib and 13.3 GPa for dental bones; it consisted of the classical tensile method, and the hardness measurement by NDLT consisted of Vickers hardness for rib and dental bones. Furthermore, the rib bones show less wear coefficient than the teeth, whose values (4.33 and 5.55 × 10-14 m2/N) for rib and teeth, respectively. Dependent on NDLT and classical results and calculations, the NDLT results have good agreement with classical methods; it is a good technique employed as an alternative method to find acoustic material properties and mechanical properties; NDLT is a suitable, precision, accurate, cheaper, and non-distractive manner applied to examine the acoustic properties of bone and biological materials in the future.

Trajectory of bolt and length of plate in femoral neck system determine the stability of femur neck fracture and risk of subsequent subtrochanteric fracture : a finite element analysis

BACKGROUND

This study aimed to analyze the differences in the stability of fractures, stress distribution around the distal-most screw according to the length of the plate and the trajectory of the bolt in Pauwels type III femoral neck fracture using the femoral neck system (FNS).

METHODS

Finite element models of Pauwels type III femoral neck fractures were established with surgical variations in the trajectory of the bolt (central, inferior, valgus, and varus) and length of the lateral plate (1- and 2-hole plate). The models were subsequently subjected to normal walking and stair-climbing loads.

RESULTS

The screw-holding cortical bone in subtrochanter in the model with a 2-hole plate and the bolt in the inferior trajectory and the models with 1-hole or 2-hole plate and the bolt in valgus trajectory had shown greater maximum principal strain than the models with central or varus trajectories. The gap and sliding distance on the fracture surface were larger with inferior or varus trajectories of the bolt and smaller with the valgus trajectory of the bolt under both loads, compared to those of the central trajectory.

CONCLUSION

For the fixation of Pauwels type III femoral neck fracture, the trajectory of the FNS bolt and the length of the plate affect the mechanical stability of the fracture and the strain of cortical bone around the distal-most screw. The surgical target should stay on the central trajectory of the bolt and the 2-hole plate's mechanical benefits did not exceed the risk.

Computational evaluation of the axis-blade angle for measurements of implant positions in trochanteric hip fractures: A finite element analysis

BACKGROUND

Recently, a novel approach axis-blade angle (ABA) was developed to measure implant positions during trochanteric hip fracture surgery. It was defined as the sum of two angles α and β measured between the femoral neck axis and helical blade axis in anteroposterior and lateral X-ray films, respectively. Although its clinical practicability has been confirmed, the mechanism is yet to be investigated by means of finite element (FE) analysis.

METHODS

Computed tomography images of four femurs and dimensions of one implant at three angles were obtained to construct FE models. For each femur, 15 FE models in an arrangement (intramedullary nails at three angles multiplying five blade positions) were established. Under the simulation of normal walking loads, the ABA, von Mises stress (VMS), maximum/minimum principal strain and displacement were analyzed.

RESULTS

When the ABA increased, all outcome indicators initially decreased till reaching inferior-middle site and then increased while the blade positions within the femoral head shifted from the superior-anterior quadrant toward the inferior-posterior quadrant, where the ABA were higher. Only the peak VMS of implant models in the inferior-posterior quadrant (particularly the inferior-middle site within) with blades in did not reach the yielding (risky) cut-off.

CONCLUSIONS

From the perspective of angles, ABA, this study demonstrated the inferior-posterior quadrant as the relatively stable and safe regions, especially the inferior-middle site within. This was similar but more elaborate compared with previous studies and clinical practice. Therefore, ABA could be employed as a promising approach to anchor the implants into the optimal region.