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Kita-ku, Japan

Uetsuki K.,Nakashima Medical Co.
Transactions of Japanese Society for Medical and Biological Engineering | Year: 2014

Many researches, such as wear resistance enhancement and metal surface modification for bone-implant bonding, have been conducted in order to improve the performance and function of artificial joint. In 2010, Nakashima Medical Co., Ltd. has launched Vitamin-E (dl-α-tocopherol) blended UHMWPE as knee joint bearing material that is expected superior durability. And then, as a hip joint bearing material, crosslinked Blend-E was placed on market in 2013. These materials have different properties in consideration of each biomechanics. In this paper, we report about our development of biomaterials, especially of the Vitamin-E blended UHMWPEs, BLEND-E® and BLEND-E® XL. © 2014, Japan Soc. of Med. Electronics and Biol. Engineering. All rights reserved. Source

Uetsuki K.,Okayama University | Uetsuki K.,Nakashima Medical Co. | Kaneda H.,Okayama University | Shirosaki Y.,Okayama University | And 2 more authors.
Materials Science and Engineering B: Solid-State Materials for Advanced Technology | Year: 2010

Titanium and its alloys are employed as artificial joints, bone plates, wires, screws and bone prostheses in orthopedic and dental fields, because of their high corrosion resistance, good mechanical properties, and biocompatibility. Since they cannot directly bond to living bone-tissue through stable chemical interactions, a few surface modification techniques have been proposed for giving materials apatite-forming ability that secures bone-tissue bonding, such as chemical treatment with H2O2 or NaOH, electrochemical oxidation, electrophoretic apatite particle deposition, and UV-irradiation of surface titanium oxide layer. This study examined how the combination of H2O2 chemical treatment and UV-irradiation affected in vitro apatite-formation on TiO2 (anatase phase) layers as UV was irradiated under a few different conditions. TiO2 layer was prepared by the chemical treatment with H2O2 solution and subsequent heat-treatment (CHT). CHT samples were irradiated with UV-light for 1 h in air or in ultra-pure water. They were then soaked in Kokubo's simulated body fluid (SBF; pH 7.4) at 36.5 °C for 1 day. Their surface structure and morphology were examined by using a thin film X-ray diffractometer (TF-XRD), and a scanning electron microscope (SEM). The UV-irradiation of CHT in air reduced the number of active sites for apatite nucleation. On the contrary, however, the UV-irradiation in water increased them. These opposite results indicate that environmental factors of the UV-irradiation are important for controlling the in vitro apatite-forming ability of anatase layer. © 2009 Elsevier B.V. Source

Noyama Y.,Osaka University | Noyama Y.,Nakashima Medical Co. | Miura T.,Osaka University | Ishimoto T.,Osaka University | And 3 more authors.
Materials Transactions | Year: 2012

The present work was aimed at clarifying the stress-shielding effect caused by hip-joint implantation into a femur by using a human cadaver with a cementless hip implant. In particular, bone quality was assessed from the standpoint of preferential c-axis orientation of biological apatite (BAp). Comparing the implanted side to the non-implanted side, a finite element analysis (FEA) indicated that artificial hip-joint implantation had a significant stress-shielding effect on the femur. The results also showed a marked decrease in the degree of preferential BAp orientation as well as bone loss in the medial-proximal femur. This is the first report showing a reduction in the degree of preferential BAp orientation due to a stress-shielding effect after artificial hip-joint implantation. Since preferential BAp orientation is an important index for determining bone mechanical function, these findings should be taken into account in future artificial hip-joint designs, especially those involving the stem component. © 2012 The Japan Institute of Metals. Source

Noyama Y.,Osaka University | Noyama Y.,Nakashima Medical Co. | Nakano T.,Osaka University | Ishimoto T.,Osaka University | And 2 more authors.
Bone | Year: 2013

We proposed a novel surface modification for an artificial hip joint stem from the viewpoint of maintenance and establishment of appropriate bone function and microstructure, represented by the preferred alignment of biological apatite (BAp) and collagen (Col). Oriented grooves were introduced into the proximal medial region of the femoral stem to control the principal stress applied to the bone inside the grooves, which is a dominant factor contributing to the promotion of Col/BAp alignment. The groove angle and the stem material were optimized based on the stress inside the grooves through a finite element analysis (FEA). Only the groove oriented proximally by 60° from the normal direction of the stem surface generated the healthy maximum principal stress distribution. The magnitude of the maximum principal stress inside the groove decreased with increasing the stem Young's modulus, while the direction of the stress did not largely changed. An in vivo implantation experiment showed that this groove was effective in inducing the new bone with preferential Col/BAp alignment along the groove depth direction which corresponded to the direction of maximum principal stress inside the groove. The anisotropic principal stress distribution and the oriented microstructure inside the groove are similar to those found in the femoral trabeculae; therefore, the creation of the oriented groove is a potent surface modification for optimizing implant design for a long-term fixation. © 2012 Elsevier Inc. Source

Nakashima Medical Co. | Date: 2011-01-07

A surgical assistance system for operating on biological tissue using a surgical tool attached to an arm of an automatically-controlled surgical instrument so that an optimal feed rate of the tool is calculated and outputted to the surgical instrument, the system including: a device for storing and voxelizing medical image data obtained from a biological tissue subject to surgery; a device for setting an operative location based on the shape of the biological tissue; a device for calculating a tool path along which the tool travels to perform surgery at an operative location; a device for determining the region of interference between the tool and the voxels; a device for determining the hardness of the biological tissue in the interference region; a device for calculating an optimal tool feed rate corresponding to the hardness; and a device for outputting the feed rate obtained by the calculations to the surgical instrument.

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