Investigation on biomechanics behavior using three-dimensional finite element analysis for femur shaft fracture treated with locking compression plate / 生物医学工程学杂志

Based on the CT data and the structure characteristics of the femoral fractures during different healing stages, medical FE models of fractured femur treated with locking compression plate (LCP)were built. Under the physiological load of a standard body weight (70 kg) and the constraint condition, the stress distributions of LCP and fractured femur during healing were calculated by means of three-dimensional finite element analysis (3D-FEA). The results showed that the stress distribution in the LCP and the fractured femur was similar, during the initial stage which there was no newly formed bone or soft tissue in fracture site. The maximum von Mises stress (371.23,272.76 MPa) in the fractured femur was much higher than that in natural femur, and the intensive stress was concentrated mainly in the proximal area of the fractured femur. With the growth of bony callus bone in fracture site, the intensity of stress in proximal femur decreased. Contrasted to the two cases mentioned above, the value of the maximum von Mises stress (68. 17 MPa) in bony callus bone stage decreased significantly, and was lower than the safe strength of natural bone. Therefore, appropriate training which is benefitial for the growth to new bone could be arranged for the better rehabilitation.

Synthesis of strontium-containing porous hydroxyaptite ceramics and study of its biological properties / 生物医学工程学杂志

Strontium added into porous hydroxyaptite ceramics has the functions of improving its osseointegration, decreasing its dissolution rate and improving the bone density. Strontium-containing hydroxyaptite (Sr-HA) ceramics has been used as bone replacement and scaffold to treat the osteoporosis and bone default in clinic, but the mechanism of interfacial tissue response caused by the trace element Sr in Sr-HA ceramics still remains to be further studied. Four types of Sr-HA ceramic samples with different contents of Sr were prepared by microwave plasma sintering for testing the response of the soft tissue implanted in dog muscles in our laboratory. The contents of Sr element in the samples are 0 mol%, 1 mol%, 5 mol%, and 7 mol%, respectively. The samples were implanted in the muscle of the dogs for 4 weeks, 8 weeks and 12 weeks, respectively. The histological observations at the end of each period showed that the irritant ranking increased with the content of Sr in Sr-HA ceramics at the end of 12 weeks, and there were rich bone tissue in Sr-HA ceramic samples with 5 mol% Sr element. The overdose of element Sr is harmful to soft tissues. When the content of Sr in Sr-HA ceramic was below 5 mol%, the soft tissue response was very slight and the new bones were induced to grow well.

Three-dimensional finite element analysis of bone stress distribution around the hip joint prosthesis with stepped stem / 生物医学工程学杂志

Based on the CT data, a medical treatment FE model of hip joint prosthesis with stepped stem was rebuilt according the anatomy of the hip joint. Under the loads of 1.5 times standard body weight (70kg), the mechanical behavior of the treatment model was calculated, and the influence of step structure and distribution for stepped stem on femur stress and stability of total hip replacement were analyzed by three-dimensional finite element analysis (3D-FEA). The results show that the step structure changs the bone stress transmission on the interface of stepped stem and femur, and benefits to reduce stress-shielding in the femur. For the same distribution of step, the reduction of stress-shielding for raised stepped stem is better than that for concave stepped stem. The raised stepped stem of which the steps is distributed one of third part of the stem is of the best effect of reduction of stress shielding in all of the analysis models, and is a beneficial mechanical design to relieves osteoporosis or osteopenia of femur caused by stress-shielding and improve the reliability of it in clinic.

Three-dimensional finite element analysis and biomechanical study on reconstruction of the large defect of proximal femur with allograft prosthesis composite in clinical bone-healing phase / 生物医学工程学杂志

Three-dimensional finite element models of the large defect of proximal femur were reconstructed with allograft prosthesis composite in clinical bone-healing phase; current model was under the given conditions of 138mm-intramedullary stem-length of host bone and 135mm defect-length of proximal femur. The femur was constructed with efilm software from CT data, then three-dimensional concrete models were created by using Proe-Wildfire software; the three-dimensional finite element models of allograft prosthesis composite were made in ANSYS11 software. Loads were simulated using the peaking values during stance walking. The stress on femur-cement-callus-prostheses and the influence of stress on the clinical bone-healing phase were analysed. The highest stress value of femur is on the medial side of the tip of the prostheses. The highest stress value of cement mantle is on the medical side of the cement mantle at the tip of the stem. The highest stress value of the prostheses is on the medial side near the upper 4cm of the stem tip. The highest stress value on the callus is at the medial side of the callus layer. The highest stress value on every part is under the corresponding fatigue strength. Clinical bone-healing phase model is well enough for stance walking.

Biological evaluation of new percutaneous implanting materials / 生物医学工程学杂志

According to ISO 10993 standard series, the biological safety of surface modified pure titanium was studied as a percutaneous device by the test of cytotoxicity in vitro, as well as by the tests of irritation and sensitization. The result from the examination of cytotoxicity in vitro was negative, the skin irritation response was negligible, and the result of test on skin sensitization in guinea pigs was also negligible. So the surface modified pure titanium in this study can be safely used as percutaneous implanting materials.

3D finite element analysis of bone stress around distally osseointegrated implant for artificial limb attachment / 生物医学工程学杂志

Using the CT data, we have constructed the finite element models of human femur distally amputated at high-position, middle-position and low-position, along with distally osseointegrated implant under the maximal load during a normal walking cycle. Results of finite element analysis revealed: the maximal stress of implant is produced near the exit of the amputated limb, where the fatigue breakpoint caused by cyclic stress would take place. With the ascending of truncated position, the peri-implant interfacial stress of bone increases. There is severe stress-shielding at the bone-implant interface, and there is concentration of stress at the end of implant and at the 3/4 point of femur, which would lead to bone loss and bone resorption and would shorten the longevity of implant. The results also showed that the curvature of natural bone has notable effect on the stress distribution, which should not be neglected. These data may provide reliable reference for the design and research of osseointegarted artificial limb.

Stress distribution in bone around dental implants studied by three-dimensional finite element analysis / 实用口腔医学杂志

Objective:To study the stress distribution in bone with different densities around dental implants in different shape.Methods:Dental implants in the shape of cylinder,thread and steps were implanted into the mandibular bone at the position of the first molar with 4 different densities respectively.Three-dimension finite element models were rebuilt and stress distribution in the bone around implants were investigated. Results:In the same load and bone density conditions, cylindrical implant resulted in lowest peak stress value,the same implant in mandibular bone with higher density produced lower stress peak value.Conclusion:Dental implatns in the shape of cylinder and higher density of the bone around the implant may reduce stress concentration.