Design modifications and evaluation of the silicone artificial finger joints.

BACKGROUND: There are many reasons that could lead to finger joint arthroplasty, and the most familiar reason is osteoarthritis. Silicone finger joint are the most commonly used implants. However, these implants might fracture with time and cause wear which will lead to chronic inflammation and synovitis for the patient and then implant failure. OBJECTIVE: The aim of this study is to improve the design of the silicone finger joint and simulate the different designs using finite element analysis (FEA) simulation. METHOD: Three different designs were drawn and FEA has been used in this study using Solidworks software. The first design is the silicone finger joint design without any modification, the second one is modified design with added ribs to the junction of distal stem and hinge and the third design was added filler material inside the body of the artificial joint. An axial force with 625 N that was applied on the upper part of the distal stem which is nearly represents the maximum value of the grip strength for normal males. RESULTS: The results showed improvement on the design in which the concentrated stress at the junction of the distal stem and hinge of the design was distributed. In addition, the Von Mises stress was stable for the modified design with added ribs and the added filler material designs after 15°. CONCLUSION: The design modification could improve the stress distribution and stability of the artificial finger joint and increase the lifetime expectancy of these implants.

A multi-bundle concentric coil wirelessly transferring power to in vivo implantable devices.

Biomedical devices implanted inside the human body have a heavy demand on battery power. The internal batteries are charged wirelessly through two coils. The primary is placed outside the chest and is fed with an electromagnetic field, while the implanted secondary delivers current to the batteries. Increasing the number of turns in the internal secondary induces an increased amount of localized heat. A new approach proposed by the authors involves implanting a specifically designed multi-bundle concentric coil inside the body. It is shown that this newly proposed coil produces less localized heat. The total number of turns in the proposed coil is the same as that in the single-bundle coil except that it is divided into four equal bundles. Each bundle has a different diameter and is spatially concentric. Since the turns are divided into thinner bundles, they are easier to isolate with a biocompatible material and offer much better heat dissipation and fewer hotspots. Electromagnetic simulation using finite element analysis proved that the performance of the proposed coil is no lower than the single-bundle ordinary coil. Thermal simulation showed the improvement of temperature distribution using the multi-bundle coil, compared to the single-bundle coil.

An effective method for skin blood flow measurement using local heat combined with electrical stimulation.

Electrical stimulation (ES) is a modality used to increase skin blood flow (SBF) and to aid in wound healing. A greater SBF in non wounded skin is induced if ES is used in a warm environment compared to a thermoneutral environment, where ES is usually applied. Therefore, in this paper, a method to investigate the effect of local heating and ES on the SBF is developed. A total of 33 males (18-40 years) were divided into group G (n = 15) who received the ES during a global heating protocol and group L (n = 18) who received ES during a local heating protocol. In the global heating protocol, ES (30 Hz, 250 micros) was applied for 15 min on the subject's thigh in thermoneutral (25 +/- 0.5 degrees C) and warm (35 +/- 0.5 degrees C) environments. In the local heating protocol, ES was applied for 15 minutes at 25 degrees C, 35 degrees C and 40 degrees C local skin temperatures. A laser Doppler imager measured the SBF in both protocols pre, during, and post ES. The results of the experiment showed the significant differences in the SBFs were found at pre, during, and post ES in a thermoneutral environment or when the skin was locally cooled to 25 degrees C. The SBFs were significantly increased during and post ES after global heating or during local heating at 35 degrees C and 40 degrees C. There were no significant differences in SBFs between the warm environment and at 35 degrees C of local heating. However, the SBF response to ES was the highest at 40 degrees C of local heating. Thus, ES during local heating of the skin, as well as during global heating is an effective method to increase SBF.