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Purpose: The biomechanical performance of a novel engineered porous-structure implant (EPSI) with various porosities and a conventional solid-structure implant (CSSI) was investigated and compared. Materials and Methods: The three-dimensional finite element method was applied to titanium dental implant models placed in a block of bone that included both cortical and medullary bone. Five different pore sizes and porosities of the EPSI (58% porosity [PSI-58], 62% porosity [PSI-62], 71% porosity [PSI-71], 75% porosity [PSI-75], and 79% porosity [PSI-79]), were compared with the CSSI. Equivalent von Mises (EQV) stress, strain energy density, and displacement were examined for each implant design. Results: The maximum EQV stresses exhibited in cortical bone of the EPSI models were lower than those of the CSSI model. Higher EPSI porosity tended to increase the EQV stress. The EPSI appeared to share the load with the cortical bone, as evidenced by lower strain energy density in the cortical bone of EPSI models. High values for displacement were observed at the coronal part of the implant in all models. Slight differences in maximum displacement values were seen between EPSI and CSSI models. Conclusion: The EPSI effectively reduced the maximum EQV stress in the cortical bone and enhanced the load-sharing capacity. A significant amount of energy was absorbed by the implant instead of being transferred to the surrounding cortical bone. Varying the porosity of an implant had less effect on implant displacement. [ABSTRACT FROM AUTHOR]

Lateral condylar prominence is a common problem after corrective osteotomy of the cubitus varus, which is believed to result from unequal opposing cut surfaces of lateral-based wedge osteotomy using a medial hinge. This study investigated this issue using a 3-dimensional CT data set consisting of images of the deformed elbow and the normal elbow of a patient with cubitus varus deformity who was scheduled for corrective osteotomy A CT scan was performed with 3mm slice thickness and a reconstruction was done with 1mm interpolated slice thickness on both the left and right humerus. The CT-data set was then manipulated using reverse engineering software. Three-dimensional models of both the deformed and normal humeri were studied. Several locations or levels of medial hinge placement, each with 4-degree-tilt wedge osteotomy cut options, were then virtually performed and evaluated. The degree of correction was determined from the varus angle plus the normal carrying angle of the normal side. From the study, it was found that the degree of lateral condylar prominence is directly proportional to the distance of placement of the medial hinge above the joint. Differences in the lengths of the osteotomy surfaces have no effect on condylar prominence; only the step-off phenomenon affects condylar prominence. According to our findings, placement of the medial hinge close to the joint with a 10-degree distal osteotomy cut just above the olecranon fossa will result in optimal minimization of condylar prominence or the step-off phenomenon.

This paper proposes a novel method of using an antero-posterior buttress screw at the distal fragment just below the fracture site in conjunction with the sliding hip screw (SHS) to resist excessive femoral medialisation. A virtual assessment of the effectiveness of this new method was performed using the finite element analysis. The results indicate that the use ofa sliding hip screw (SHS) combined with a buttress screw can help resistfemoral medialisation better than using an SHS with no buttress screw. The von Mises equivalent stress (EQ ) was found to be in a safe range, which indicates increased integrity of the lateral wall with the addition of the buttress screw.

Objective: To investigate the optimal entry point for retrograde femoral nailing using medical imaging and reverse engineering technologies., Material and Method: One hundred and eight adult cadaveric femurs were scanned using a computed tomography (CT) scanner. To obtain three-dimensional models, medical imaging and reverse engineering technologies were used. The insertion assessment was performed using computer aided design (CAD) software. The curve representing the mid-line in the intramedullary canal in the mid-shaft region was approximated using regression analysis. The curve was extended tangentially toward the femoral condyle, where the intersection between the curve and the condylar surface is the insertion site. The location of the insertion site was determined using the center of the anterior most of the intercodylar notch as a reference point. The measured distances were presented in medial-lateral and anterior-posterior perspectives from the reference point., Results: Average insertion site for Thai population was 0.56 mm lateral to and 12.67 mm medial to the anterior most of the intercondylar notch. The distance measured from intercondylar notch to the insertion site in the anterior-posterior direction was not significantly different between males and females; however a significant difference in the insertion site was found in medial-lateral directions., Conclusion: The insertion site can be clinically approximated lying on the anterior-posterior axis, since the distance from the anterior-posterior axis to the insertion site is relatively small. The insertion site for the Thai population was found to be 12 mm anterior to the center of the anterior most of the intercondylar notch.

Objective: To study the stress distributions in normal and osteoarthritic knee joints using the finite element method (FEM)., Material and Method: Three normal and three varus knee joints are included in the study. Computed tomography (CT) images of the lower extremities are used to create 3D geometric models consisting of bones, articular cartilages, menisci, and knee ligaments. Each of the lower extremities includes the femur, tibia, fibula, and talus. Each 3D geometric model is adjusted to the normal standing configuration with the help of its corresponding 2D radiographic image. After that, 3D finite element (FE) models are created from the adjusted 3D geometric models. FEM is then used to obtain stress distributions on the articular cartilages. In the analysis, the displacements on the posterior calcaneal articular surface of the talus are fully fixed. A vertical concentrated force equal to the body weight is applied at the femoral head., Results: In the normal knee joints, the maximum normal stresses on the articular cartilages in the lateral compartments are always higher than those in the medial compartments. In the varus knee joints, the opposite results are observed. However, in each normal knee joint, the stress distribution on the whole articular cartilage is moderately uniform. On the contrary, in each varus knee joint, comparatively high magnitudes of the normal stress are found on a large area of the articular cartilage in the medial compartment., Conclusion: Varus knee joints have higher stresses in the medial compartments while normal knee joints have higher stresses in the lateral compartments. This pilot study shows that FE studies are comparable to cadaveric studies. FEM can be used as an alternative method for studying and examining knee joints of patients.

Objective: Investigate the 2D/3D geometry of femoral curvature and femoral length using the advanced technique of computerized tomography combined with reverse engineering techniques., Material and Method: The present study was performed using reverse engineering technique based on CT data of 99 cadaveric femora. The femur was divided into three segments, proximal, mid-shaft, and distal regions by defining 35% and 65% of the femoral total length as a boundary of each region. The intramedullary canal in the mid-shaft region was mainly extracted to determine the set of circular center, which could consequence to approximate the 3D femoral radius of curvature using the 3D least square best fit. The 3D femoral curvature was then projected into A-P and M-L directions to investigate the correlation of 2D/3D femoral curvature as normal radiographic images., Results: It was found that the average 3D Thai femoral curvature was 895.46-mm (SD = 238.06) and the average femoral total length is 421.96-mm (SD = 27.61). In addition, the 2D femoral curvature derived from sagittal radiographic image can be used to determine the 3D femoral curvature with this equation: R3D = RSagittal + 3.67 with r = 0.987., Conclusion: This described technique is a non-destructive method that can effectively assess the internal/ external 3D geometric data of the femur The obtained data is useful to develop a proper design of prosthesis that required inserting into the intramedullary canal. From the present study, it can be concluded that the 2DSagittal femoral curvature derived from standard radiographic image can be represented for the 3D femoral curvature.