Aims

The aim of this study was to determine the clinical outcomes and factors contributing to failure of transposition osteotomy of the acetabulum (TOA), a type of spherical periacetabular osteotomy, for advanced osteoarthritis secondary to hip dysplasia.

Aims

To clarify the mid-term results of transposition osteotomy of the acetabulum (TOA), a type of spherical periacetabular osteotomy, combined with structural allograft bone grafting for severe hip dysplasia.

Aims

The aims of this study were to validate the Forgotten Joint Score-12 (FJS-12) in the postoperative evaluation of periacetabular osteotomy (PAO), identify factors associated with joint awareness after PAO, and determine the FJS-12 threshold for patient-acceptable symptom state (PASS).

Aims

The risk of postoperative complications after resection of soft-tissue sarcoma in the medial thigh is higher than in other locations. This study investigated whether a vessel sealing system (VSS) could help reduce the risk of postoperative complications after wide resection of soft-tissue sarcoma in the medial thigh.

Aims

Biofilm formation is intrinsic to prosthetic joint infection (PJI). In the current study, we evaluated the effects of silver-containing hydroxyapatite (Ag-HA) coating and vancomycin (VCM) on methicillin-resistant Staphylococcus aureus (MRSA) biofilm formation.

Background

The purpose of this study was to analyze the effect of femorotibial alignment (FTA), femoral and tibial component alignment, correction of malalignment, and thickness of tibial osteotomy on implant loosening following total knee replacement.

Problems

Biofilm infections are increasingly associated with orthopedic implants. Bacteria form biofilms on the surfaces of orthopedic devices. The biofilm is considered to be a common cause of persistent infections at a surgical site. The growth and the maturation of biofilm are enhanced by the flow of broth in culture environment. In order to reduce the incidence of implant-associated infections, we developed a novel coating technology of hydroxyapatite (HA) containing silver (Ag). We previously reported that the Ag-HA coating inhibits biofilm formation under flow condition of Trypto Soy Broth + 0.25% glucose for 7 days. In this study, we evaluated whether the Ag-HA coating continuously inhibits the biofilm formation on its surface under flow condition of fetal bovine serum, which contains many in vivo substrates such as proteins.

Background

Subtrochanteric femoral shortening and corrective osteotomy are considered to be an integral part of total hip arthroplasty for a completely dislocated hip or severe deformity of the proximal femur. A number of alternative femoral osteotomy techniques, transverse, oblique, step-cut, and V-shaped, have been described. Becker and Gustilo reported the “double-chevron subtrochanteric shortening derotational femoral osteotomy,” which is reasonable in that the osteotomy site is torsionally more stable and can be stabilized with a shorter stem. We have simplified this procedure, and performed it without a trochanteric osteotomy. We describe a simplified double-chevron osteotomy and provide the clinical results from a series of 22 successful procedures.

The objective of this study is to investigate the effect of the tensile force ratio between the two extensor muscles for the hip joint on the forces acting on the knee joint. We have created a mathematical model of lower limb and have performed some simulations to introduce the forces acting on the knee joint for various daily activities. With only one exception, our results for knee joint forces were in good or close agreement involving all range of knee flexion either with the in vivo data or other literature data. The exception was that, at high knee flexion angle (knee bend), the tangential components of knee joint force became pretty larger than those from the in vivo data, while the normal components did not differ much with each other though as shown in Fig. 1.

We considered that the above mentioned discrepancy was attributed to the fact that in order to solve an indeterminate problem, we had assumed the hamstrings and the gluteus maximus work together with the same force with each other, thereby introducing the hamstrings force too great. Then we expected that the above discrepancy could be eliminated if we change the tensile force ratio between the hamstrings and the gluteus maximus basing upon a certain biomechanical criterion, for example the biological cross-sectional areas.

Thus we modified our model so that we could introduce the knee joint forces as a function of the tensile force ratio. Simulation was performed for the various tensile ratio values and it was found that the knee joint force was sensitively affected by the tensile ratio and the above mentioned discrepancy between the simulation results and the in vivo data could be eliminated if the ratio value was appropriately chosen. Figure 2 shows the situation; Variations of F_n and F_t as a function of knee angle q for the various tensile force ratio r between the hamstrings and the gluteus maximus. Where, r=1.56 was determined from the biological cross-sectional areas of the hamstrings and the gluteus maximus and r=4.5 was determined so that the simulation results best fit to the in vivo data.

It has been criticized that there exist large variations of knee joint forces obtained from model analyses. And the reasons for this have been attributed to for example such facts that the model is 2D and the parameter values are incorrect. Yet, another important issue may be to find out the way how to determine the value of the synergetic muscles' force ratio with reflecting a biological rationality.

Background

Dislocation is one of the commonest complications of total hip arthroplasty (THA) with incidence of between 0.3 and 10% in primary, and from 15 % to 30% of revision cases. Despite this, little is known of the outcome of treatment strategies for dislocation. In this study, we evaluated clinical results in patient undergoing revision THA for recurrent dislocation.

The objective of this study is to determine the knee joint forces when rising from a kneeling position. We have developed a new type of knee prosthesis which is capable of attaining Japanese style sitting. To run the simulations and experiments needed to assess the performance of this prosthesis, it is necessary to know what forces act on the knee during deep flexion. Because these data are lacking, we created a 2D mathematical model of the lower leg to help determine knee joint forces during deep flexion. Healthy subjects of ten males (age of 25±4years, height of 170.3±9.1cm, and weight of 67.0±22.2kg) and five females (25±3years, 161±7.1cm, 47.7±6.2kg) participated in the experiment. Ground reaction force and joints angles were measured using a force plate and a motion recording system respectively. The collected data were entered into our mathematical model, and the muscle forces and the knee joint forces were calculated. To verify our model, we first used it to run simulation of middle and high flexions of the knee joint. In vivo data for these actions are available in the literature, and the results from our simulation were in good agreement with these data. We then collected the data and run simulation when rising from a kneeling position under the conditions shown in Fig. 1. They were a) double leg rising (both legs are aligned) without using the arms, b) ditto but using the arms, c) single leg rising (legs are in the front and the rear respectively) without using the arms, and d) ditto but using the arms. We obtained the following results. The statistics of the maximum values on the single knee joint for each condition were; a) F_max=5.1±0.4 [BW: (force on the knee joint)/(body weight)] at knee flexion angle of Q=140±8°, b) F_max=3.2±0.9[BW] at Q=90±10°, c) F_max-d=5.4±0.5[BW] at Q_d=62±20° for the dominant leg and F_max-s=3.0±0.5[BW] at Q_s=138±6° for the supporting leg respectively, and d) F_max-d=3.9±1.5[BW] at Q_d=70±17° for the dominant, and F_max-s=2.1±0.5 [BW] at Q_s=130±11° for the supporting. We may conclude that the single leg rising should be recommended since the maximum knee joint force did not become large as long as the knee was at deep flexion. The values introduced in this study could be used to assess the strength of the knee prosthesis at deep flexion. To obtain more realistic values of the joint forces, it is necessary to determine the ratio of the forces exerted by the mono-articular and the bi-articular joint muscles.

Bacterial infection related to prosthetic replacement is one of the serious types of complications. Recently, there has been a greater interest in antibacterial biomaterials. In order to reduce the incidence of replacement-associated infections, we developed a novel coating technology of Hydroxyapatite (HA) containing silver (Ag). We reported the Ag-HA coating showed high antibacterial activity against E. coli, S. aureus and methicillin-resistant S. aureus (MRSA) under static condition. However, human bodies have a circulating body fluid, which is not a static condition. And the growth and the maturation of biofilm, which is said that a common course of persistent infections at a surgical site, are enhanced by the flow of broth in culture environment. Therefore, we evaluated whether the Ag-HA coating inhibits the biofilm formation on its surface or not by a biofilm-forming test under flow condition in this study.

Ag-HA or HA powder was sprayed onto the commercial pure titanium disks using a flame spraying system. The HA coating disks were used as negative control. The biofilm-forming methicillin sensitive S. aureus (BF-MSSA; Seattle 1945) strain and the BF-MRSA (UOEH6) strain were used. The pre-culture bacterial suspension (about 10⁵ colony forming units; CFU) was inoculated onto the Ag-HA and HA coating disks. After cultivation at 37 °C for 1 h, the disks were rinsed twice with 500 μL sterile PBS (-) to eliminate the non-adherent bacteria. The number of the adherent bacteria on these disks was counted using culture method. After rinsing, the disks were transferred into petri-dish containing Trypto–Soy Broth (TSB) + 0.25% glucose with a stirring bar on the magnetic stirrer and they were cultured at 37°C for 7 days. In the meantime, the stirring bar was spun at 60 rounds per minute. Then, the disks were immersed in a fluorescent reagent to stain the biofilm. Finally, the biofilm on each disk was observed by a fluorescence microscope and the biofilm-covered rate on the surfaces of them was calculated using the NIH image software.

The number of the bacteria on these disks was not so different between Ag-HA and HA coating after rinsing. After biofilm-forming test, the coverage of the biofilm of BF-MSSA was 2.1% and 81.0% on the Ag-HA and HA coatings, respectively. Similarly, in the case of BF-MRSA, it was 7.7% and 72.0% on the Ag-HA and HA coatings, respectively. Though bacteria slightly adhered, biofilm was hardly observed on the Ag-HA coating. The biofilm on the HA coating was extensive and mature. The inhibition effect of biofilm formation on the Ag-HA coating might be ascribed to the antibacterial effect by Ag ions released from the coating. Because Ag ions have a broad spectrum of antibacterial activity against pathogens, including biofilm forming bacteria, they inhibited the biofilm formation on the Ag-HA coating by killing adherent bacteria. Even in a flow condition, it was suggested that the AgHA shows the antibacterial activity, though the conditions in this work are different from those in living body.

The objective of this study is to introduce the forces acting on the knee joint while ascending from kneeling. Our research group has developed a new type of knee prosthesis which is capable of attaining complete deep knee flexion such as a Japanese style sitting, seiza. Yet we could not set up various kinds of simulation or experiment to assess the performance of our prosthesis because the data about joints' forces during the ascent from deep knee flexion are lacking. Considering this circumstance, we created a 2D mathematical model of lower limb and determined knee joint force during ascent from kneeling to apply them for the assessment of our prosthesis.

Ten male and five female healthy subjects participated in the measurement experiment. Although the measurement of subjects' physical parameters was non-invasive and direct, some parameters had to be determined by referring to the literature. The data of ground reaction force and each joint's angle during the motion were collected using a force plate and video recording system respectively. Then the muscle forces and the joints' forces were calculated through our mathematical model. In order to verify the validity of our model approach, we first introduced the data during the activities with small/middle knee flexion such as level walking and rising from a chair; these kinds of data are available in the literature. Then we found our results were in good agreement with the literature data. Next, we introduced the data during the activities with deep knee flexion; double leg ascent [Fig.1 (a)] and single leg ascent [Fig.1 (b)] from kneeling without using the upper limbs.

The statistics of the maximum values on the single knee joint for all the subjects were; during double leg ascent, F_max = 4.6±0.6 (4.3-5.2) [BW: (force on the knee joint)/(body weight)] at knee flexion angle of b =140±8 (134-147)°, during double leg ascent, F_max = 4.9±0.5 (4.0-5.6) [BW] at b = 62±33 (28-110)° for the dominant leg, and F_max = 3.0±0.5 (22.2-3.8) [BW] at b = 138±6 (130-150)° for the supporting leg respectively. We found that the moment arm length, i.e., the location of muscle insertion significantly affected the results, while ascending speeds did not affect the results much. We may conclude that the single leg ascent should be recommended since F_maxdid not become large while deep knee flexion. The values could be used for assessing the strength of our knee prosthesis from the risk analysis view point.

A silver-containing hydroxyapatite (Ag-HA) coating has been developed using thermal spraying technology. We evaluated the osteoconductivity of this coating on titanium (Ti) implants in rat tibiae in relation to bacterial infection in joint replacement.

At 12 weeks, the mean affinity indices of bone formation of a Ti, an HA, a 3%Ag-HA and a 50%Ag-HA coating were 97.3%, 84.9%, 81.0% and 40.5%, respectively. The mean affinity indices of bone contact of these four coatings were 18.8%, 83.7%, 77.2% and 40.5%, respectively. The indices of bone formation and bone contact around the implant of the 3%Ag-HA coating were similar to those of the HA coating, and no significant differences were found between them (bone formation, p = 0.99; bone contact, p = 0.957). However, inhibition of bone formation was observed with the 50%Ag-HA coating.

These results indicate that the 3%Ag-HA coating has low toxicity and good osteoconductivity, and that the effect of silver toxicity on osteoconductivity depends on the dose.

Surgical site infection related to orthopaedic implants is one of the serious complications. In the previous works, we developed a novel thermal spraying technology combined silver with hydroxyapatite (HA) in order to resolve such problems, and reported the property and antibacterial effect of them in vitro. However, no previous reports have investigated in vivo. Therefore, we monitored serum silver level in rats to clarify in vivo kinetics of silver released from the coating.

HA loaded with 3 wt % of silver oxide (HA-Ag) and plain HA powder were sprayed on surface of titanium disks (20 mm diameter × 1 mm thick) by the flame spraying, which is a kind of thermal spraying method with acetylene torch. All these test pieces were obtained from Japan Medical Materials Corporation (JMM, Osaka, Japan). Both samples were implanted singly into the back subcutaneous pockets of male Sprague-Dawley rats (150–200 g). Rats were housed individually and given ad libitum access to food and water. After 24 h, 48 h, 7 d, 14 d and 28 d, the rats were sacrificed, and then the blood was drawn from common iliac vein. All procedures were operated under anesthesia. These blood samples were spun down and serum silver levels were measured by an inductively coupled plasma mass spectrometry.

The average serum silver level in HA-Ag group had increased to more than 40 ppb until 48 h after implantation, and then decreased rapidly to normal level. There were significant differences (p < 0.05) between HA-Ag and HA group, at each measurement period.

This is the first report to elucidate the serum silver level in rats implanted HA-Ag coatings. To date, reported coating technologies have included direct-loading antibacterial agents or heavy metals including silver with prosthesis base. The combine technology HA with silver would be effective in not only antibacterial but also osteoconductive respect. Our experimental results highlight the following 2 features: the serum silver levels peaked relatively early, and the levels reduced immediately to normal level after the peak. Therefore, we speculate that the released silver would not be accumulated generally, which not contribute long-term toxicity, and the coating would be suitable for prevention of early surgical site infections.

This study provides novel and important information on in vivo release- property for HA-Ag coating, and suggests this coating is effective against not late but rather early infection related to orthopaedic implants.

Bacterial infections related to orthopaedic implants is one of the serious types of complications. Recently, there has been a greater interest in antibacterial biomaterials. However, antibacterial evaluations of each material are inconsistant, so intercomparison of the antibacterial performance is difficult. This study focused on the Japanese Industrial Standards test (JIS Z2801), which is used for antibacterial evaluation of commodities. The study investigated a suitable evaluation method for in vitro antibacterial activity of biamaterials. In 2007, JIS Z2801 test was approved as international standard ISO 22196.

Hydroxyapatite (HA) powder containing 3 wt % of silver oxide (Ag) was sprayed on the surface of titanium disks with the thermal spraying method, using an acetylene torch. This coating has been proved to generate strong antibacterial activity in previous studies. The antibacterial activity was examined with the JIS Z 2801 test and modified JIS Z2801 test. The bacterial strains used in JIS Z2801 test were Escherichia coli (E.coli), Staphylococcus aureus (S.aureus). Bacterial culture medium was instilled onto the surface of the test disks (about 106 cells/ml) and covered with polystyrene films. After cultivation in 1/500 Nutrient Broth for 24 h at 35°C, the bacteria was washed out with the broth. The numbers of viable bacteria in the broth were counted with the agar plate culture method. Additionally, Modified JIS Z2801 test was performed. Modified points were added to the bacterial strain of biofilm-forming methicillin-resistant S.aureus (BF-MRSA), using Fetal Bovine Serum (FBS) as a culture medium, and cultivated at 37°C.

In the JIS Z2801 test, Antibacterial activity values of the HA-Ag disk were composed against E.coli 4.1 and S.aureus 5.0. In the modified JIS Z2801 test, antibacterial activity values against E.coli, S.aureus and BF-MRSA were 8.2, 5.5, and 7.1. When this value is greater than 2.0, it shows there is antibacterial activity. The titanium disk coated with HA-Ag showed antibacterial activity in both tests.

The JIS Z2801 test is designed to evaluate comodities in poor nutritional environment. However, the environment in the body is eutrophic. It is easy to make bacterial growth. For this reason, it is necessary to consider evaluating for biomaterials with suitable method considered in vivo. In this study, to examine the condition like that found in the body, we cultivated FBS at 37°C. In addition, the antibacterial activity against BF-MRSA was examined to consider the bacterial infection related to orthopaedic implants. The modified JIS Z2801 test showed that it is a suitable evaluation method for in vitro antibacterial activity of biomaterials.

Bacterial infection related to orthopaedic implants is a significant complication today. One of the ways to reduce the incidence of implant-associated infections is assumed to give antibacterial activity to surface of implant itself. We focused attention on Ag, because it has a broad antibacterial spectrum, strong antimicrobial activity and low toxicity. In the previous works, sputtering, electrochemically deposition and sol-gel coating of Ag-containing hydroxyapatite (HA) have been reported. However, since practical technique of HA coating widely used for medical and dental implants has been the “thermal spraying” technique over the last two decades, we aimed at developing the novel thermal spraying technology for Ag-HA coating with antibacterial activity. In this study, physical and chemical properties, in vitro antibacterial activity, inhibition activity of bacterial attachment, HA-forming ability, cytotoxicity and release of Ag ions of the thermal-sprayed Ag-HA coating were evaluated.

HA powder containing 3wt % of silver oxide (Ag2O) was sprayed on surface of titanium disks by the thermal spraying method using acetylene torch. SEM images showed a typical structure of the thermal-sprayed coating and the X-ray diffraction (XRD) pattern of the coating showed an amorphous structure. Ag residue in the coating was determined by the elementary analysis. The coating showed strong antibacterial activity and inhabitation activity of bacterial attachment to the methicillin-resistant Staphylococcus aureus (MRSA) in fetal bovine serum (FBS). On the other hand, the coating showed fast HA-forming ability in simulated body fluid (SBF) and no cytotoxicity related to Ag contained in the coating. Therefore, it is expected that the thermal-sprayed Ag-HA coating provides antibacterial and bone-bonding ability on the surface of the implant itself. In addition, though the HA coating is generally liable to adhere bacteria, the thermal-sprayed Ag-HA coating overcomes this problem.

Pre-evaluation of release of Ag ions from the Ag-containing ceramic powders indicated that the releasing behavior of Ag ions in SBFs is dependent on the existing form of Ag in the Ag-containing material. It is assumed that most of Ag components in the Ag-HA coating are not retained as metallic Ag but as Ag2O in the amorphous layer. Time-course release tests of Ag ions from the coating in FBS showed a large release rate of Ag ions until 24 h after the immersion. It is expected that the Ag-HA coating could show strong antibacterial activity at the early post-operative stage. In the repeated release testing, the amount of released Ag ions was about 6500 ppb for the first release test, after which it gradually decreased. However, a significant release amount of Ag ions was observed even after the sixth repeat test. Therefore, it was assumed that the thermal-sprayed Ag-HA coating has a slow-release property of Ag ions in FBS.

Using thermal spraying technique, we developed a novel titanium material coated with hydroxyapatite (HA) containing silver (Ag). In this study, antibacterial activities of the material were examined both in vitro and in vivo.

Two different titanium test pieces were prepared. One is the test piece that was coated by HA containing Ag (HA-Ag) and the other is that was coated by HA only, used as a negative control. Antibacterial activity and efficacy of HA-Ag against Staphylococcus aureus, Escherichia coli, and biofilm-forming methicillin-resistant S. aureus (BF-MRSA) was examined by using the Japanese Industrial Standards test (JIS Z2801). Furthermore, surface area where BF-MRSA was attached and proliferated on the test pieces after 24 hours of incubation was calculated by means of scanning electron microscope (SEM). To investigate the antibacterial activity in vivo, the test pieces were inserted subcutisly into the back of SD rats, and BF-MRSA was inoculated into the inserted pieces. On the 7th day after the inoculation, the numbers of adherent bacteria to the pieces were countered by a sterile cotton-tipped swabs method.

By the JIS Z2801 test, HA-Ag showed 104 to 105 times stronger antibacterial activity than HA against all bacteria tested in this study. SEM studies revealed the HA-Ag coated material had 30 to 50 times smaller area of attached bacteria than control. In vivo study showed that viable bacterial numbers on surfaces of HA-Ag were 1000 times less than control. These results indicated that the HA-Ag coated materials have antibacterial activities both in vitro and in vivo.

Titanium coated with HA containing Ag has a possibility to be a novel antibacterial biomaterial.