Incidence and characteristics of aspiration pneumonia in the Nagasaki Prefecture from 2005 to 2019.

BACKGROUND: Aspiration pneumoniae remains a major health concern, particularly in the older population and has poor prognosis; however, the concept itself remains vague worldwide. This study aimed to determine the actual situation and characteristics of aspiration pneumonia from 2005 to 2019 in Nagasaki Prefecture, Japan. METHODS: Cases of aspiration pneumonia that occurred in the Nagasaki Prefecture between 2005 and 2019 were analyzed using emergency transportation records. The number of occurrences and incidence were analyzed according to age, sex, month, day of the week, and recognition time to clarify the actual situation of aspiration pneumonia. RESULTS: The total number of new aspiration pneumonia cases was 8,321, and the mean age of the patients was 83.0 years. Annual incidence per 100,000 population increased from 12.4 in 2005 to 65.1 in 2019, with the most prominent increase in the ≥ 80-year-old stratum. Males (55.1%) were more commonly affected than females (44.9%), and 82.2% of the cases involved patients aged ≥ 70 years. No significant correlations were observed between the incidence of aspiration pneumonia and season, month, or day of the week. Aspiration pneumonia occurred frequently in houses (39.8%) and facilities for elderly individuals (40.8%). At 7 days after admission, 80.9% of patients were still hospitalized and 6.5% had died. CONCLUSIONS: The incidence of aspiration pneumonia with risks of severity and mortality is increasing among elderly individuals. Valid preventive measures are urgently needed based on the findings that the disease occurs in both household and elderly care facility settings, regardless of the season.

Mirror Therapy Reduces Pain and Preserves Corticomotor Excitability in Human Experimental Skeletal Muscle Pain.

Approaches to preserve corticomotor excitability (CE) are attracting interest as a treatment for pain-induced changes in neural plasticity. We determined the effects of mirror therapy (MT) on skeletal muscle pain. Fifteen healthy adults who received hypertonic saline injections (5.8% NaCl, 0.2 mL) into the first dorsal interosseous (FDI) muscle of the right hand to induce experimental skeletal muscle pain were assigned to either the "MT and injection" or "injection only" group. Post-injection, the "MT and injection" group observed their left index finger abducting and adducting for 4 min, creating the illusion that the right index finger was moving. The "injection only" group remained at rest. CE and pain were assessed by measuring motor-evoked potentials (MEPs) of the right FDI triggered by transcranial magnetic stimulation and the numerical rating scale (NRS), respectively. MEP amplitudes were significantly higher in the "MT and injection" group, a trend that persisted post-MT intervention (MT intervention; p < 0.01, post-1; p < 0.05). The time for the NRS score to reach 0 was notably shorter in the "MT and injection" group (p < 0.05). Our preliminary results suggested that MT decreases CE and pain in skeletal muscles, potentially preventing neural plasticity changes associated with skeletal muscle pain and providing early pain relief.

Mechanical Stress Via Muscle Contractile Exercise Suppresses Atrophic Alterations of Bone-microstructure in Immobilized Rat Femurs.

OBJECTIVES: This study aimed to determine whether mechanical stress via muscle contractile exercise with belt electrode-skeletal muscle electrical stimulation (B-SES) device effectively prevents immobilization-induced bone atrophy. METHODS: Wistar rats were randomly divided into the control (CON) group, immobilization (IM) group (immobilized treatment only), HES and LES groups (immobilized treatment and high or low-intensity electrical muscular stimulation through B-SES device). Bilateral femurs were used for X-ray micro-CT and biomechanical tests. RESULTS: The maximum load value was significantly lower in the IM and HES groups than in the CON group and significantly higher in the LES group than in the IM group. The maximum crushing load was significantly lower in the IM, HES, and LES groups than in the CON group, and significantly higher in the HES and LES groups than that in the IM group. In micro-CT, the mechanical stress by B-SES device did not affect degenerative microstructural changes in the cortical bone, but prevented those changes in the cancellous bone. CONCLUSIONS: Applying mechanical stress via B-SES device suppressed the loss of cancellous bone density and degenerative microstructural changes caused by immobilization, which in turn suppressed the reduction of bone strength. From these findings, muscle contractile exercise may be effective in preventing immobilization-induced bone atrophy.

Comparison of short-term clinical outcomes between open-wedge high tibial osteotomy and tibial condylar valgus osteotomy.

BACKGROUND: This study aimed to compare radiological features and short-term clinical outcomes between open-wedge high tibial osteotomy (OWHTO) and tibial condylar valgus osteotomy (TCVO), to provide information facilitating decision-making regarding those two procedures. METHODS: Twenty-seven cases involving 30 knees that had undergone OWHTO (HTO group) and eighteen cases involving 19 knees that had undergone TCVO (TCVO group) for medial compartment knee osteoarthritis (OA) were retrospectively evaluated. Patient characteristics, severity of knee OA, lower limb alignment, joint congruity and instability were measured from standing full-length leg and knee radiographs obtained before and 1 year after surgery. Range of motion in the knee joint was measured and Knee Injury and Osteoarthritis Outcome Score (KOOS) was obtained to evaluate clinical results preoperatively and 1 year postoperatively. RESULTS: Mean age was significantly higher in the TCVO group than in the HTO group. Radiological features in the TCVO group included greater frequencies of advanced knee OA, varus lower limb malalignment, higher joint line convergence angle, and varus-valgus joint instability compared to the HTO group before surgery. However, alignment of the lower limb and joint instability improved to comparable levels after surgery in both groups. Maximum flexion angles were significantly lower in the TCVO group than in the HTO group both pre- and postoperatively. Mean values in all KOOS subscales recovered similarly after surgery in both groups, although postoperative scores on three subscales (Symptom, Pain, and ADL) were lower in the TCVO group (Symptom: HTO, 79.0; TCVO, 67.5; Pain: HTO, 80.5; TCVO, 71.1; ADL: HTO, 86.9; TCVO, 78.0). CONCLUSIONS: Both osteotomy procedures improved short-term clinical outcomes postoperatively. TCVO appears preferable in cases of advanced knee OA with incongruity and high varus-valgus joint instability. An appropriate choice of osteotomy procedure is important to obtain favorable clinical outcomes.

The interrelationship between lower limb movement, muscle activity, and joint moment during half squat and gait.

Joint moment is the resultant force of limb movements. However, estimation methods for joint moments using surface electromyography frequently use joint angles instead of limb angles. The limb angle in joint moment estimation using electromyography could clarify the effects of muscle activity on the limbs: acceleration, deceleration, or stabilization. No study has quantified the comprehensive relationship between limb movement, muscle activity, and joint moment. This study aimed to determine the influencing factors for ankle-joint moment and knee-joint moment in the sagittal plane among muscle activities and parameters related to limb movements during half squat and gait. This study included 29 healthy adults (16 female participants, 21.1 ± 2.09 years). Using inertial measurement units, thigh, shank, and foot inclination angles and angular accelerations were calculated as the parameters of limb movements. Muscle activations of the biceps femoris long head, rectus femoris, gastrocnemius, and tibialis anterior were measured. Ankle joint moment and knee-joint moment were measured using a three-dimensional motion capture system and two force plates. Regression models showed high accuracy in measuring ankle-joint moment during a half squat and gait (R2f = 0.92, 0.97, respectively) and knee-joint moment during a half squat (R2f = 0.98), but not knee-joint moment during gait (R2f = 0.63). However, only a maximum of five parameters were selected from muscle activities and limb angular information. Tibialis anterior and gastrocnemius activity were the largest contributors to ankle-joint moment during a half squat and gait, respectively, while muscle activities were not directly reflected in the knee-joint moment during either movement. Consideration of the interrelationships among limb movement, muscle activity, and joint moment is required when adjusting joint movements according to the target and aim of the therapeutic interventions.

Progression of microstructural deterioration in load-bearing immobilization osteopenia.

PURPOSE: Immobilization osteopenia is a major healthcare problem in clinical and social medicine. However, the mechanisms underlying this bone pathology caused by immobilization under load-bearing conditions are not yet fully understood. This study aimed to evaluate sequential changes to the three-dimensional microstructure of bone in load-bearing immobilization osteopenia using a fixed-limb rat model. MATERIALS AND METHOD: Eight-week-old specific-pathogen-free male Wistar rats were divided into an immobilized group and a control group (n = 60 each). Hind limbs in the immobilized group were fixed using orthopedic casts with fixation periods of 1, 2, 4, 8, and 12 weeks. Feeding and weight-bearing were freely permitted. Length of the right femur was measured after each fixation period and bone microstructure was analyzed by micro-computed tomography. The architectural parameters of cortical and cancellous bone were analyzed statistically. RESULTS: Femoral length was significantly shorter in the immobilized group than in the control group after 2 weeks. Total area and marrow area were significantly lower in the immobilized group than in the control group from 1 to 12 weeks. Cortical bone area, cortical thickness, and polar moment of inertia decreased significantly after 2 weeks. Some cancellous bone parameters showed osteoporotic changes at 2 weeks after immobilization and the gap with the control group widened as the fixation period extended (P < 0.05). CONCLUSION: The present results indicate that load-bearing immobilization triggers early deterioration of microstructure in both cortical and cancellous bone after 2 weeks.

Visualization of Airborne Particles as a Risk for Microbial Contamination in Orthopedic Surgery.

Background: The operating theater is recognized to involve a high frequency of occupational blood and body fluid contacts. Objectives: This study aimed to visualize the production of blood and body fluid airborne particles by surgical procedures and to investigate risks of microbial contamination of the conjunctival membranes of surgical staff during orthopedic operations. Methods: Two physicians simulated total knee arthroplasty (TKA) and total hip arthroplasty (THA) in a bio-clean theater using model bones. The generation and behaviors of airborne particles were filmed using a fine particle visualization system, and numbers of airborne particles per 2.83 L of air were counted at the height of the operating and instrument tables. Each action was repeated five times, and particle counts were evaluated statistically. Results: Numerous airborne particles were dispersed to higher and wider areas while "cutting bones in TKA" and "striking and driving the cup component on the pelvic bone in THA" compared to other surgical procedures. The highest particle counts were detected while "cutting bones in TKA" under unidirectional laminar air flow. Discussion: These results provide a clearer image of the dispersion and distribution of airborne particles and identified higher-risk surgical procedures for microbial contamination of the conjunctival membranes. Surgical staff including surgeons, nurses, anesthesiologists, and visitors, should pay attention to and take measures against occupational infection particularly in high-risk surgical situations.

Effects of attentional bias modification on chronic low back pain in older outpatients: A randomized crossover trial (pilot study).

OBJECTIVES: In the present study, the effect of attentional bias modification (ABM) on older outpatients, with chronic low back pain, was examined. DESIGN: This was a single-center, randomized, single-blinded, crossover trial and patients were randomly divided in a 1:1 allocation ratio into two groups: an ABM Leading group and an ABM Trailing group. PARTICIPANTS: Forty-three outpatients with chronic low back pain participated. INTERVENTIONS: Patients were evaluated four times and the treatments were ABM + Normal intervention or Normal intervention only. OUTCOMES: Outcome measures included pain intensity on the Numerical Rating Scale, the Pain Catastrophizing Scale, Fear-Avoidance Beliefs Questionnaire, Hospital Anxiety and Depression Scale, Somatic Symptom Scale-8, and EuroQol 5 Dimension-3 levels questionnaire. In addition, we performed the 30-second Chair-Stand test and the Timed Up & Go test for physical function evaluations. RESULTS: There was no change in pain intensity due to ABM. However, the total Pain Catastrophizing Scale score was significantly decreased, and the EuroQol 5 Dimension-3 levels questionnaire and 30-second chair-stand test were significantly improved (P <.05). TRIAL REGISTRATION: The Health Science Ethics Committee, Graduate School of Biomedical Sciences, Nagasaki University (permit number: 17060861), and the clinical trial was registered with UMIN (UMIN000029424).

Incidence of and risk factors for hip fracture in Nagasaki, Japan from 2005 to 2014.

The annual incidence of new hip fractures increased from 2005 to 2014 in Nagasaki and females were much more affected. High-risk factors were identified as age ≥ 80 years, winter, indoors, living room, Monday, and early morning. Seven days after admission, most patients remained hospitalized and had been treated surgically. INTRODUCTION: Hip fractures are major osteoporotic fractures that reduce quality of life. In Japan, the incidence of hip fractures increased steadily from 1986 to 2014 and the number of hip fractures could be 7.3-21.3 million by 2050. This study aimed to determine the incidence of hip fractures from 2005 to 2014 in Nagasaki Prefecture and to analyze the characteristics of and risk factors for hip fracture. METHODS: Hip fractures that occurred in Nagasaki Prefecture between 2005 and 2014 were analyzed using emergency transportation records. Fracture type, age, sex, location in which fracture occurred, and risk factors for hip fracture were clarified. RESULTS: The total number of new hip fractures among individuals ≥ 35 years old was 17,395 (mean age, 82.6 years old) and the annual incidence per 100,000 population increased from 147.9 in 2005 to 235.0 in 2014. Females (79.6%) were much more commonly affected than males (20.4%) and cervical fractures were more common than trochanteric fractures in all age groups. Hip fracture tended to be associated with age ≥ 80 years, winter rather than summer, indoors rather than outdoors, and living room rather than the bathroom or toilet. Other high-risk factors were Monday as day of the week, and early morning as the time of day. Seven days after admission, 97.3% of patients were hospitalized and 78.1% of hip fractures had been treated surgically. CONCLUSION: Information on actual situations and valid preventive measures relevant to hip fracture are urgently needed.

Comparison of radiological features of high tibial osteotomy and tibial condylar valgus osteotomy.

BACKGROUND: The purpose of this study was to compare radiological features between high tibial osteotomy (HTO) and tibial condylar valgus osteotomy (TCVO), in order to define the radiological indication criteria for TCVO. METHODS: Thirty-two cases involving 35 knees that had undergone HTO and the same number that had undergone TCVO for knee osteoarthritis were retrospectively evaluated. Characteristics of both groups did not differ significantly. Lower limb alignment, bone morphology, joint congruity, and joint instability were measured in standing full-length leg and knee radiographs obtained before and after surgery. RESULTS: Radiological features in the TCVO group included greater frequencies of advanced knee OA grade, varus lower limb malalignment, depression of the medial tibial plateau, and varus-valgus joint instability compared to the HTO group before surgery. However, tibial morphology, alignment of the lower limb, and joint instability improved to comparable levels after surgery in both groups. CONCLUSIONS: TCVO appears preferable in cases with advanced knee OA, destroyed or inclined medial tibial plateau, widened and subluxated lateral joint, and high varus-valgus joint instability.

Factors contributing to airborne particle dispersal in the operating room.

BACKGROUND: Surgical-site infections due to intraoperative contamination are chiefly ascribable to airborne particles carrying microorganisms. The purpose of this study is to identify the actions that increase the number of airborne particles in the operating room. METHODS: Two surgeons and two surgical nurses performed three patterns of physical movements to mimic intraoperative actions, such as preparing the instrument table, gowning and donning/doffing gloves, and preparing for total knee arthroplasty. The generation and behavior of airborne particles were filmed using a fine particle visualization system, and the number of airborne particles in 2.83 m3 of air was counted using a laser particle counter. Each action was repeated five times, and the particle measurements were evaluated through one-way analysis of variance multiple comparison tests followed by Tukey-Kramer and Bonferroni-Dunn multiple comparison tests for post hoc analysis. Statistical significance was defined as a P value ≤ .01. RESULTS: A large number of airborne particles were observed while unfolding the surgical gown, removing gloves, and putting the arms through the sleeves of the gown. Although numerous airborne particles were observed while applying the stockinet and putting on large drapes for preparation of total knee arthroplasty, fewer particles (0.3-2.0 µm in size) were detected at the level of the operating table under laminar airflow compared to actions performed in a non-ventilated preoperative room (P < .01). CONCLUSIONS: The results of this study suggest that surgical staff should avoid unnecessary actions that produce a large number of airborne particles near a sterile area and that laminar airflow has the potential to reduce the incidence of bacterial contamination.

Effect of carbon ion implantation on the tribology of metal-on-metal bearings for artificial joints.

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.

11. Bactericidal Activity of Photocatalytic TiO2 Excited by Low Intensity Pulsed Ultrasound (LIPUS): An In Vitro Study.

Photocatalysis with anatase-type titanium dioxide (TiO2) under ultraviolet has a well-recognized bactericidal effect. The purpose of the present study was to evaluate the photocatalytic bactericidal effects of TiO2 on Staphylococcus epidermidis (ATCC35984) caused by Low Intensity Pulsed Ultrasound (LIPUS) associated with bio-implant-related infections. The photocatalytic properties of the TiO2 films were confirmed by the degradation of an aqueous solution of methylene blue. The disks were seeded with cultured Staphylococcus epidermidis and irradiated by LIPUS. The bactericidal effect of the TiO2 films was evaluated by counting the surviving colonies. The viability of the bacteria on the photocatalytic TiO2 film coated titanium was suppressed significantly to 63% after 2 hours of LIPUS treatment (P < 0.05). The photocatalytic bactericidal effect of TiO2 under LIPUS is useful for sterilizing the contaminated and infected surfaces of metal bio-implants.

Biofilm-forming Staphylococcus epidermidis expressing vancomycin resistance early after adhesion to a metal surface.

We investigated biofilm formation and time of vancomycin (VCM) resistance expression after adhesion to a metal surface in Staphylococcus epidermidis. Biofilm-forming Staphylococcus epidermidis with a VCM MIC of 1 µg/mL was used. The bacteria were made to adhere to a stainless steel washer and treated with VCM at different times and concentrations. VCM was administered 0, 2, 4, and 8 hours after adhesion. The amount of biofilm formed was evaluated based on the biofilm coverage rates (BCRs) before and after VCM administration, bacterial viability in biofilm was visually observed using the fluorescence staining method, and the viable bacterial count in biofilm was measured. The VCM concentration required to decrease BCR significantly compared with that of VCM-untreated bacteria was 4 µg/mL, even in the 0 hr group. In the 4 and 8 hr groups, VCM could not inhibit biofilm growth even at 1,024 µg/mL. In the 8 hr group, viable bacteria remained in biofilm at a count of 10(4) CFU even at a high VCM concentration (1,024 µg/mL). It was suggested that biofilm-forming Staphylococcus epidermidis expresses resistance to VCM early after adhesion to a metal surface. Resistance increased over time after adhesion as the biofilm formed, and strong resistance was expressed 4-8 hours after adhesion.

Epidemiology of Kienböck's disease in middle-aged and elderly Japanese women.

Little research has been done on the prevalence of Kienböck's disease, and there is no consensus on the relationship between Kienböck's disease and negative ulnar variance. The goal of this cross-sectional study was to determine the prevalence of Kienböck's disease in middle-aged and elderly Japanese women and to clarify the relationship between Kienböck's disease and negative ulnar variance. The authors analyzed plain radiographs of both hands in women 40 years and older residing in the community to investigate the prevalence of Kienböck's disease and the relationship between Kienböck's disease and negative ulnar variance. Kienböck's disease was seen in 7 of the 572 participants. In the group with Kienböck's disease, ulnar variance did not differ significantly between affected (0.3 mm; SD, 1.5) and unaffected (0.3 mm; SD, 1.0; P=.285) sides. No significant difference was seen in ulnar variance values between the affected side in the group with Kienböck's disease and the normal group (P=.118). The number or proportion of participants with negative ulnar variance did not differ significantly between the affected side in the group with Kienböck's disease (3 of 7) and the unaffected side in the group with Kienböck's disease (1 of 7; P=.237) and between the affected side in the group with Kienböck's disease and the normal group (111 of 504; P=.189) by chi-square test. The prevalence of Kienböck's disease was 1.2% in middle-aged and elderly Japanese women. Negative ulnar variance is not a contributing factor to Kienböck's disease.

Early staphylococcal biofilm formation on solid orthopaedic implant materials: in vitro study.

Biofilms forming on the surface of biomaterials can cause intractable implant-related infections. Bacterial adherence and early biofilm formation are influenced by the type of biomaterial used and the physical characteristics of implant surface. In this in vitro research, we evaluated the ability of Staphylococcus epidermidis, the main pathogen in implant-related infections, to form biofilms on the surface of the solid orthopaedic biomaterials, oxidized zirconium-niobium alloy, cobalt-chromium-molybdenum alloy (Co-Cr-Mo), titanium alloy (Ti-6Al-4V), commercially pure titanium (cp-Ti) and stainless steel. A bacterial suspension of Staphylococcus epidermidis strain RP62A (ATCC35984) was added to the surface of specimens and incubated. The stained biofilms were imaged with a digital optical microscope and the biofilm coverage rate (BCR) was calculated. The total amount of biofilm was determined with the crystal violet assay and the number of viable cells in the biofilm was counted using the plate count method. The BCR of all the biomaterials rose in proportion to culture duration. After culturing for 2-4 hours, the BCR was similar for all materials. However, after culturing for 6 hours, the BCR for Co-Cr-Mo alloy was significantly lower than for Ti-6Al-4V, cp-Ti and stainless steel (P<0.05). The absorbance value determined in the crystal violet assay and the number of viable cells on Co-Cr-Mo were not significantly lower than for the other materials (P>0.05). These results suggest that surface properties, such as hydrophobicity or the low surface free energy of Co-Cr-Mo, may have some influence in inhibiting or delaying the two-dimensional expansion of biofilm on surfaces with a similar degree of smoothness.

Characterization of individuals with sacroiliac joint bridging in a skeletal population: analysis of degenerative changes in spinal vertebrae.

The aim of this study was to characterize the individuals with sacroiliac joint bridging (SIB) by analyzing the degenerative changes in their whole vertebral column and comparing them with the controls. A total of 291 modern Japanese male skeletons, with an average age at death of 60.8 years, were examined macroscopically. They were divided into two groups: individuals with SIB and those without bridging (Non-SIB). The degenerative changes in their whole vertebral column were evaluated, and marginal osteophyte scores (MOS) of the vertebral bodies and degenerative joint scores in zygapophyseal joints were calculated. SIB was recognized in 30 individuals from a total of 291 males (10.3%). The average of age at death in SIB group was significantly higher than that in Non-SIB group. The values of MOS in the thoracic spines, particularly in the anterior part of the vertebral bodies, were consecutively higher in SIB group than in Non-SIB group. Incidence of fused vertebral bodies intervertebral levels was obviously higher in SIB group than in Non-SIB group. SIB and marginal osteophyte formation in vertebral bodies could coexist in a skeletal population of men. Some systemic factors might act on these degenerative changes simultaneously both in sacroiliac joint and in vertebral column.

Effect of surface roughness of biomaterials on Staphylococcus epidermidis adhesion.

BACKGROUND: Implant-related infections are caused by adhesion of bacteria to the surface of biomaterials. In this in vitro research, we evaluated the ability of Staphylococcus epidermidis (ATCC35984) to adhere to the surface of solid biomaterials at different levels of roughness below 30 nm Ra and investigated the minimum level of roughness required to promote bacterial adhesion on five kinds of biomaterials: oxidized zirconium-niobium alloy (Oxinium), cobalt-chromium-molybdenum alloy (Co-Cr-Mo), titanium alloy (Ti-6Al-4 V), commercially pure titanium (Cp-Ti) and stainless steel (SUS316L), samples of which were categorized into a fine group and a coarse group according to surface roughness. The test specimens were physically analyzed and the viable bacterial density of the adhered bacteria was quantitatively determined (n = 20). RESULTS: The amount of bacteria that adhered to the biomaterials in the coarse group was higher than those in the fine group. Oxinium, Ti-6Al-4 V and SUS316L in particular demonstrated statistically significant differences between the two groups (P < 0.05). Of the materials, the Co-Cr-Mo specimens exhibited significantly lower amounts of adhered bacteria than the Ti-6Al-4 V, Cp-Ti and SUS316L specimens in the fine group. Similarly, the Co-Cr-Mo specimens in the coarse group exhibited significantly lower values than the other four materials. CONCLUSIONS: These results suggest that minimum level of roughness affecting initial bacterial adherence activity differs according to the type of biomaterial used, and that even a surface roughness of below 30 nm Ra in Oxinium, Ti-6Al-4 V and SUS316L can promote bacterial adhesion. Relative hydrophobic Co-Cr-Mo surfaces were less susceptible to bacterial adherence.

Potentiation of osteoclastogenesis by adipogenic conversion of bone marrow-derived mesenchymal stem cells.

Bone marrow-derived mesenchymal stem cells (BMSCs) are the indispensable component of the bone marrow, being the common precursors for adipocytes and osteoblasts. We show here that adipogenic differentiation resulted in increase in the production of adipocyte markers, such as adiponectin,fatty-acid binding proteins (FABP4), peroxisome proliferator-activated receptor γ (PPARγ), as well as the receptor activator of nuclear-κB ligand (RANKL). Co-culture of osteoclast precursors (OCPs) with BMSCs-derived adipocytes significantly enhanced osteoclast differentiation with low-dose RANKL, whose levels alone could not promote osteoclastogenesis. These results demonstrate for the first time that adipogenic differentiation of BMSCs plays a pivotal role in maintaining bone homeostasis.

Adherence ability of Staphylococcus epidermidis on prosthetic biomaterials: an in vitro study.

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 <10 nm). The amounts of S. epidermidis that adhered to the biomaterial were significantly lower for Oxinium and the cobalt-chromium-molybdenum alloy than for commercially pure titanium. These results suggest that Oxinium and cobalt-chromium-molybdenum alloy are less susceptible to bacterial adherence and are less inclined to infection than other materials of a similar degree of smoothness.