Biomechanical supporting effect of tantalum rods for the femoral head with various sized lesions: a finite-element analysis / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Features of necrotic lesions and various interventions could affect the biomechanics of the femoral head. A three-dimensional finite-element analysis was designed to demonstrate necrotic femoral head stress changes with various sizes of necrotic lesions, and evaluate the effect of tantalum rods on preventing femoral head cracking.</p><p><b>METHODS</b>Femoral computed tomography scans were used to build a normal three-dimensional finite-element femoral head model in a computer. Based on the normal model, necrotic models of different lesion diameters (15 mm, 20 mm and 30 mm) were created, as were the repaired models with tantalum rods for each diameter. After a series of meshing and force loading, the von Mises stress distributions, simulating single-legged stance, and stresses on specific points under loaded conditions were determined for each model.</p><p><b>RESULTS</b>Deep exploration into the burdened area of the femoral head indicated that higher stresses to the femoral head were observed with a larger necrotic lesion; the largest stress concentration, 91.3 MPa, was found on the femoral head with a lesion diameter of 30 mm. By contrast, topical stress on the surface of the necrotic regions was lowered following implantation of a tantalum rod, and the changes in stress were significant in models with lesions of 15 mm and 30 mm in diameter, with the best biomechanical benefit from the tantalum rod found with a lesion diameter of 15 mm.</p><p><b>CONCLUSIONS</b>Femoral heads with larger necrotic lesions usually have a higher stress concentration and a higher risk of collapse. Various sized lesions on the femoral head can benefit from the mechanical support offered by the implantation of a tantalum rod; however, femoral heads with smaller sized lesions may benefit more. A thorough evaluation of the lesion size should be conducted prior to the use of tantalum rod implants in the treatment of femoral head necrosis.</p>

Three-dimensional finite element analyses of bone surface stress of two kinds of conjunction implant / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To establish a three-dimension finite element model of mandible with two kinds of dental implant and to study the stress of implant-bone interface.</p><p><b>METHODS</b>Measuring the data of the components of the dental implant and using spiral CT image reconstruction technique to scan the cross section of the mandible. Three-dimension finite element analysis software Unigraphics and MSC. Marc/Mentat were used to build the conjunction model and bone model of two implant systems. Loading 200 N axially and 100 N 30 degrees obliquely on the models respectively, the stress distribution patterns of the bone interface of two implant systems were analyzed.</p><p><b>RESULTS</b>The stress distribution on the bone interface of two implant systems was similar. The peak stress of oblique loading was higher than that of axial loading. The peak stress district of the bone was concentrated on the stricture of the implant cervix, which was more obviously displayed on the Replace Select implant. The peak stresses on the bone interface of Replace Select implant were higher than that of Replace implant in all loadings.</p><p><b>CONCLUSION</b>To Replace Select especially, oblique force should be avoided in clinical practice in case of the bone absorption.</p>