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Hironobu Koseki,1 Masato Tomita,2 Akihiko Yonekura,2 Takashi Higuchi,1 Sinya Sunagawa,2 Koumei Baba,3,4 Makoto Osaki2 1Department of Locomotive Rehabilitation Science, Unit of Rehabilitation Sciences, 2Department of Orthopedic Surgery, Nagasaki University Graduate School of Biomedical Sciences, Sakamoto, Nagasaki, Japan; 3Industrial Technology Center of Nagasaki, Ikeda, Omura, Nagasaki, Japan; 4Affiliated Division, Nagasaki University School of Engineering, Bunkyo, Nagasaki, Japan Abstract: Metal-on-metal (MoM) bearings have become popular due to a major advantage over metal-on-polymer bearings for total hip arthroplasty in that the larger femoral head and hydrodynamic lubrication of the former reduce the rate of wear. However, concerns remain regarding adverse reactions to metal debris including metallosis caused by metal wear generated at the taper-head interface and another modular junction. Our group has hypothesized that carbon ion implantation (CII) may improve metal wear properties. The purpose of this study was to investigate the wear properties and friction coefficients of CII surfaces with an aim to ultimately apply these surfaces to MoM bearings in artificial joints. CII was applied to cobalt-chromium-molybdenum (Co-Cr-Mo) alloy substrates by plasma source ion implantation. The substrates were characterized using scanning electron microscopy and a 3D measuring laser microscope. Sliding contact tests were performed with a simple geometry pin-on-plate wear tester at a load of 2.5 N, a calculated contact pressure of 38.5 MPa (max: 57.8 MPa), a reciprocating velocity of 30 mm/s, a stroke length of 60 mm, and a reciprocating cycle count of 172,800 cycles. The surfaces of the CII substrates were generally featureless with a smooth surface topography at the same level as untreated Co-Cr-Mo alloy. Compared to the untreated Co-Cr-Mo alloy, the CII-treated bearings had lower friction coefficients, higher resistance to catastrophic damage, and prevented the adhesion of wear debris. The results of this study suggest that the CII surface stabilizes the wear status due to the low friction coefficient and low infiltration of partner materials, and these properties also prevent the adhesion of wear debris and inhibit excessive wear. Carbon is considered to be biologically inert; therefore, CII is anticipated to be applicable to the bearing surfaces of MoM prostheses. Keywords: total hip arthroplasty, metal-on-metal, carbon ion implantation

Tetsuya Hiramatsu,1,2 Hideyuki Kataoka,3 Mari Osaki,4 Hiroshi Hagino3,4 1Department of Speech Pathology and Audiology, Matsue Co-medical College, Matsue, Japan; 2Graduate School of Medical Sciences, Tottori University, 3School of Health Science, Faculty of Medicine, Tottori University, 4Rehabilitation Division, Tottori University Hospital, Yonago, Japan Background/purpose: Dysphagia may worsen due to fatigue of the infrahyoid and suprahyoid muscle groups as a result of repetitive swallowing during a meal. We investigated the hypothesis that meal consumption may reduce tongue strength and endurance in older adults (OAs).Methods: Tongue–palate pressure, oral diadochokinesis, repetitive saliva swallowing, and surface electromyography activity before and after a meal were measured in 23 young adults (YAs) and 23 OA volunteers.Results: There was a statistically significant difference in both tongue pressure and the number of voluntary swallows between YAs and OAs. Peak tongue pressure was significantly lower in OAs than YAs both before and after meal consumption. The most notable finding was that the first time interval (the time from test initiation to the beginning of the first swallow) was prolonged after meal consumption only in OAs, whereas the first time interval showed no difference between YAs and OAs before meal consumption with reference to the repetitive saliva swallowing test. The initiation of swallowing was prolonged by both meal consumption and aging; there was a significant interaction between these two factors. The number of repetitions of the monosyllable/pa/was statistically similar between YAs and OAs before meal consumption, but it was significantly lower in OAs after meal consumption.Conclusion: Aging leads to declining tongue pressure and motor function of the lips. It is possible that swallowing function declines in older individuals when meal consumption is prolonged, especially at the end of mealtime, as a result of their efforts in mastication and swallowing. Keywords: normal adults, dysphagia, fatigue, elderly

Takayuki Shida,1 Hironobu Koseki,1 Itaru Yoda,1 Hidehiko Horiuchi,1 Hideyuki Sakoda,2 Makoto Osaki11Department of Orthopedic Surgery, Graduate School of Medicine, Nagasaki University, Nagasaki, Japan; 2Division of Medical Devices, National Institute of Health Sciences, Tokyo, JapanAbstract: Bacterial adhesion to the surface of biomaterials is an essential step in the pathogenesis of implant-related infections. In this in vitro research, we evaluated the ability of Staphylococcus epidermidis to adhere to the surface of solid biomaterials, including oxidized zirconium-niobium alloy (Oxinium), cobalt-chromium-molybdenum alloy, titanium alloy, commercially pure titanium, and stainless steel, and performed a biomaterial-to-biomaterial comparison. The test specimens were physically analyzed to quantitatively determine the viable adherent density of the S. epidermidis strain RP62A (American Type Culture Collection [ATCC] 35984). Field emission scanning electron microscope and laser microscope examination revealed a featureless, smooth surface in all specimens (average roughness

Hironobu Koseki,1 Tomohiko Asahara,1 Takayuki Shida,1 Itaru Yoda,1 Hidehiko Horiuchi,1 Koumei Baba,2 Makoto Osaki11Department of Orthopedic Surgery, Graduate School of Medicine, Nagasaki University, 2Industrial Technology Center of Nagasaki, Nagasaki, JapanBackground: Pin site infection is the most common and significant complication of external fixation. In this work, the efficacy of pins coated with titanium dioxide (TiO2) for inhibition of infection was compared with that of stainless steel control pins in an in vivo study.Methods: Pins contaminated with an identifiable Staphylococcus aureus strain were inserted into femoral bone in a rat model and exposed to ultraviolet A light for 30 minutes. On day 14, the animals were sacrificed and the bone and soft tissue around the pin were retrieved. The clinical findings and histological findings were evaluated in 60 samples.Results: Clinical signs of infection were present in 76.7% of untreated pins, but in only 36.7% of TiO2-coated pins. The histological bone infection score and planimetric rate of occupation for bacterial colonies and neutrophils in the TiO2-coated pin group were lower than those in the control group. The bone-implant contact ratio of the TiO2-coated pin group was significantly higher (71.4%) than in the control pin group (58.2%). The TiO2 was successful in decreasing infection both clinically and histomorphometrically.Conclusion: The photocatalytic bactericidal effect of TiO2 is thought to be useful for inhibiting pin site infection after external fixation.Keywords: titanium dioxide, external fixation, bactericidal activity, Staphylococcus aureus

Shida T, Koseki H, Yoda I, et al. Int J Nanomed. 2013;8(1):3955–3961.On page 3955, please note that the first affiliation has changed from "Department of Orthopedic Surgery, Graduate School of Medicine, Nagasaki University, Nagasaki, Japan" to "Department of Orthopedic Surgery, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan".Read the original article