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Objective. The purpose of this study was to evaluate the usefulness of preoperative planning of the femurofibular angle (FFA) in medial open-wedge high tibial osteotomy (OWHTO) for mild medial knee osteoarthritis. Methods. Thirty-two patients (32 knees) with mild medial knee OA were retrospectively reviewed. The patients underwent preoperative planning of the FFA for OWHTO. For preoperative planning, a full-length weight-bearing X-ray photograph of the lower limb was opened within Adobe Photoshop Software, and a targeted corrective mechanical axis line of the lower limb and its intersecting point at the lateral tibial plateau surface was drawn using rectangle selection and filling tools. A frame, which encircled the tibia and fibula, was created around the predicted osteotomy plane and then rotated until the ankle center was on the targeted mechanical axis line. Subsequently, a distal femoral condyle line and a proximal fibula axis line were drawn, and the angle between the two lines was measured and defined as the femurofibular angle (FFA). During biplane OWHTO, the preoperatively determined FFA was used to complete the correction of the mechanical axis. During follow-up, the postoperative mechanical weight-bearing line (WBL) of the lower limb, the mechanical femorotibial angle (mFTA), and the FFA were measured and compared with the preoperatively determined values. Results. The mechanical WBL shifted from a preoperative value of 25.36 ± 5.02 % to a postoperative value of 56.19 ± 0.10 % from the medial border along the mediolateral width of the tibial plateau, and it was 56.57 ± 0.08 % at the final follow-up ( P < 0.01 ). The preoperatively determined value was 56.25%, and no significant difference was found compared with postoperative week-one and final follow-up values ( P > 0.05 ). The mFTA was corrected from a preoperative varus of 4.02 ± 0.63 ° to a postoperative week-one valgus of 2.37 ± 0.28 ° , and it had a valgus of 2.48 ± 0.39 ° at the final follow-up ( P < 0.01 ). No significant difference in the valgus was found compared with the postoperative week-one, final follow-up and preoperatively determined valgus of 2.34 ± 0.26 ° ( P > 0.05 ). The postoperative week-one and final follow-up FFAs were 90.34 ± 1.53 ° and 90.33 ± 1.52 ° , respectively, and no significant difference was found compared with the preoperatively determined value of 90.12 ± 1.72 ° and the intraoperative setting value of 90.25 ± 1.67 ° ( P > 0.05 ). All corrected values were within the acceptable range of preoperative planning. Conclusion. Preoperative planning of the FFA may be useful in OWHTO for patients with mild medial knee OA. Satisfactory correction of the postoperative targeted mechanical axis line of the lower limb can be obtained.

The aim of this study was to explore the effect of Chinese herbal SanHuang decoction (SH) on biofilm formation of antibiotic-resistant Staphylococci on titanium surface, and to explore its mechanism. Biofilm-forming ATCC 35984, ATCC 43300 and MRSE 287 were used in this study. The MICs of SH and vancomycin against Staphylococci were determined by the broth microdilution method. Six groups were designed, namely control group (bacteria cultured with medium), 1/8MIC SH group (1MIC SH was diluted by 1/8 using TSB or saline), 1/4MIC SH group, 1/2MIC SH group, 1MIC SH group and vancomycin group (bacteria cultured with 1MIC vancomycin). The inhibitory effect on bacterial adhesion and biofilm formation were observed by the spread plate method, CV staining, SEM, and CLSM. Real-time PCR was performed to determine the effect of SH on the expression levels of ica AD and ica R gene in ATCC 35984 during the biofilm formation. The strains were found to be susceptible to SH and vancomycin with MIC of 38.75 mg/ml and 2.5 μg/ml, respectively. SH with 1 MIC and 1/2 MIC could inhibit the bacteria adhesion, showing only scattered adhesion from SEM. CLSM showed that SH with 1 MIC and 1/2 MIC inhibited the biofilm formation. The quantitative results of the spread plate method and CV staining showed that there was significant differences between the SH groups (P P ica AD decreased, and the expression of ica R increased correspondingly (P Staphylococci. Its probable mechanistic activity may be through the inhibition of polysaccharide intercellular adhesin synthesis by down-regulating the expression of ica AD gene.

Background An arthroscopic narrow posteromedial gap of the knee may cause failure of a meniscus operation. The posteromedial complex (PMC) of the knee, including the posterior part of the medial collateral ligament (MCL) and the posterior oblique ligament (POL), has a restrictive effect on the opening of the posteromedial gap of the knee in the half-extension position. Thus, we evaluated the radiological and clinical results of pie-crusting release of the PMC for arthroscopic meniscal surgery in tight knees. Methods Sixty patients with posterior injury of the medial meniscus were reviewed. All patients accepted arthroscopic pie-crusting release of the PMC. Fourty patients accepted meniscoplasty, and 20 patients accepted meniscal suturing. To evaluate the arthroscopic opening of the medial gap in 20° half-extension under 11-kg valgus stress, the width of the medial space before and after release were measured. During follow-up, the medial stability was evaluated by radiographic measurements of the joint space width (JSW) in 20° half-extension. Magnetic resonance imaging (MRI) was conducted to evaluate healing of the MCL and meniscus. Knee functions were evaluated using VAS (visual analogy score), Lysholm, IKDC (International Knee Documentation Committee) and Tegner scoring systems. Results In all patients, meniscus operations were performed without iatrogenic cartilage injury. After PMC release, the arthroscopic width of the medial space was 5.7 ± 0.5 mm, larger than that before release (2.5 ± 0.5 mm, p 0.05). For sutured meniscus, MRI showed healing in 15 patients while five had two-grade abnormal signals. VAS, Lysholm, IKDC and Tegner scores were 1.80 ± 0.51, 80.08 ± 3.74, 82.17 ± 4.64 and 5.48 ± 0.59, respectively, showing significant differences compared with the preoperative scores (5.57 ± 0.69, 48.17 ± 4.22, 51.42 ± 4.02 and 3.20 ± 0.68, respectively, p

To investigate the clinical efficacy of pre-operative simulation using a three-dimensional (3D) printing model for surgical treatment of old and complex tibial plateau fractures. Forty-two patients with old and complex tibial plateau fractures were retrospectively reviewed from January 2014 to January 2018, which were divided into a conventional planning group (n = 22) and a planning with 3D printing group (n = 20). In the planning with 3D printing group, preoperative equal-ratio fracture models prepared using the 3D printing technique were used to perform pre-operative simulation and guide the real surgical operation. In the conventional planning group, the operation was performed based on pre-operative computed tomography (CT) images. Surgery duration, blood loss and the number of fluoroscopy during operations were recorded. During follow-up, the quality of fracture reduction and complications were also recorded. Knee functions were evaluated using the hospital for special surgery (HSS) scoring system. The operation time, blood loss and the number of fluoroscopy during operation in the planning with 3D printing group were less than that in the conventional planning group (P P = 0.05). The complication rate was 15% in the planning with 3D printing group and 31.82% in the conventional planning group. At the final follow-up evaluation, the mean HSS score was 86.05 ± 7.67 in the planning with 3D printing group and 79.09 ± 6.75 in the conventional planning group (P = 0.003). The rate of excellent results in the planning with 3D printing group was 70% and in the conventional planning group was 45.45% (P = 0.083). In conclusion, pre-operative simulation using a 3D printing model may be helpful for the treatment of old and complex tibial plateau fractures, which may be conducive to the pre-operative planning and to making the surgical procedure accurate and personalized. However, its clinical effectiveness need to be further assessed by a prospective randomized-controlled study.

Distal femoral resection in total knee arthroplasty (TKA) is commonly performed using intramedullary jigs with a pre-operatively planned valgus cut angle (VCA). For valgus knees with lateral femoral condyle hypoplasia, the method of determining the accurate VCA has not been clarified. The aim of the present study is to introduce a method that can accurately determine the distal femoral VCA in the valgus knee arthroplasty. Twenty patients with valgus deformity caused by lateral femoral condylar hypoplasia underwent primary TKA with individually measured VCA. The VCA was defined as the acute crossing angle of the anatomical and mechanical axes of the femur on a pre-operative X-ray film, and the two axes almost always crossed at the distal femoral diaphysis, but not the centre of the knee as generally described. The entry point of the femoral intramedullary guide rod was determined on the extension of the femoral anatomical axis and was usually medial to the centre of the knee. According to the pre- and post-operative X-ray films, the mechanical lateral distal femoral angle (mLDFA), and coronal alignment of the femoral components were measured. The post-operative knee pain and function were evaluated using the Visual Analog Scale and Knee Society Score, respectively. The mean VCA measured according to the above method was 6.4° ± 1.0° (4.7–8.2°), and the femoral entry point was located at a mean distance of 7.4 ± 2.1 mm (4.5–10.9 mm) medial to the centre of the knee joint. The mean mLDFA before and after operation was 77.4° ± 5.7° (74–82°) and 88.4° ± 1.7° (86–90°), respectively, showing a statistically significant difference (P

Treating skin and soft tissue infections of severe limb traumas can be challenging. Crucial concerns focus on inhibiting biofilm formation by antibiotic‑resistant bacteria, and preventing scar formation by fibroblastic hyperproliferation. The local use of toluidine blue O (TBO)‑mediated photodynamic therapy (PDT) may be a promising strategy for treating such lesions. The present study used Staphylococcus epidermidis (strain ATCC 35984) to assess the effects of TBO‑PDT on bacterial adherence and biofilm formation, using confocal laser scanning microscopy (CLSM), tissue culture plating (TCP) and scanning electron microscopy (SEM). Primary human fibroblast cells were used to evaluate the cytotoxicity of TBO‑PDT using the 3‑(4,5‑dimethylthiazol‑2‑yl)‑2,5‑diphenyltetrazolium bromide (MTT) assay and CLSM. Six different treatment groups were investigated: Medium only [tryptone soy broth (TSB) or Dulbecco's modified Eagle's medium (DMEM)]; red light control (light dose, 30 J/cm2); TBO group (50 mM TBO); TBO‑PDT1 (TBO irradiated with 10 J/cm2); TBO‑PDT2 (TBO irradiated with 20 J/cm2); and TBO‑PDT3 (TBO irradiated with 30 J/cm2). The results of the S. epidermidis adhesion assay indicated that the TSB, light and TBO groups exhibited significant bacterial adherence, compared with the TBO‑PDT groups. Analysis of biofilm formation revealed significant light dose‑dependent differences between the TBO‑PDT groups and the TSB, light, and TBO groups. Furthermore, SEM indicated fewer colony masses in the TBO‑PDT groups compared with the control groups. The MTT assay for fibroblastic cell toxicity demonstrated ~1.1, 4.6, 14.5, 29.7 and 43.4% reduction in optical density for the light, TBO, TBO‑PDT1, TBO‑PDT2 and TBO‑PDT3 groups, respectively, compared with the DMEM control group. There was no difference in toxicity between the light and control groups, however, there were significant differences among the TBO‑PDT groups. Finally, alterations in fibroblast morphology and cell spreading were revealed by CLSM, following TBO‑PDT treatment. TBO‑PDT inhibited bacterial adhesion and biofilm formation, and exhibited significant cytotoxic effects on human fibroblasts. These results indicate that the local use of TBO‑PDT in limb lesions may be a useful treatment method for inhibiting bacterial biofilm formation and fibroblastic hyperproliferation, which may prevent infectious hypertrophic scar formation.

Background Treatments of infections are not always successful because of multi-antibiotic-resistant organisms. It is therefore particularly urgent to provide more effective anti-infective strategy against these organisms. 5-Aminolevulinic acid (ALA), with the chemical structure C5H9NO3, is the only photodynamic therapy agent that is a biochemical precursor of a photosensitizer (protoporphyrin IX [PpIX]), which is naturally produced by the body. 5-Aminolevulinic acid–mediated photodynamic therapy (ALA-PDT) has been shown to have a strong effect on the treatment of localized cancerous and precancerous lesions, and further study demonstrated its efficacy for gram-positive and gram-negative bacteria. However, its effect on biofilm formed by antibiotic-resistant strains has not been reported. Methods In this study, we evaluated the effectiveness of ALA-PDT on biofilms formed by methicillin-resistant Staphylococcus aureus (ATCC 43300) and methicillin-resistant S epidermidis (MRSE 287). The strains were cultured with 40 mM of ALA in 24-well microtiter plates containing coverslips at 37°C for 24 h in the dark. PpIX fluorescence in biofilms formed by the two strains was observed by confocal laser scanning microscopy (CLSM). ALA-treated biofilms were irradiated at different doses (0, 100, 200, and 300 J/cm2) using a semiconductor laser. Biofilm exposed only to Tryptone Soy Broth or irradiation (300 J/cm2) was investigated. Viability determination, CLSM, and scanning electron microscopy were used to investigate the photodynamic inactivation of ALA-PDT. Results ALA was absorbed and converted to PpIX by both methicillin-resistant S aureus and methicillin-resistant S epidermidis. No cell inactivation was detectable in biofilms of either strain incubated with ALA without exposure to light, incubated with Tryptone Soy Broth only, or irradiated with red light only. However, a significant number of cells within biofilms were inactivated during irradiation with different doses of red light in the presence of 40 mM of ALA in a dose-dependent manner. The drastic reduction in cell survival within biofilms and the disruption of biofilms were confirmed by CLSM and scanning electron microscopy. Conclusions ALA-PDT has the potential to eliminate the biofilm of Staphylococcus, especially antibiotic-resistant strains, effectively. It will be suitable for the treatment of superficial local infections such as surface wounds, burns, oral and dental infections, dermatologic infections such as acne and rosacea, and soft tissue and bone infections with bone exposure.

Background Implantation-associated infections have increased significantly with the recent widespread use of medical implants. Treatments for these infections are not always successful because these infections are sometimes caused by multiantibiotic-resistant organisms. It is therefore particularly urgent to provide doctors with more effective antimicrobial agents against these antibiotic-resistant organisms. Human β-defensin 3 (hBD-3) has been shown to have strong broad-spectrum antibacterial activity. However, its effect on methicillin-resistant Staphylococcus epidermidis (MRSE) and methicillin-resistant Staphylococcus aureus (MRSA) in medical implant biofilm formation has not been reported. Methods In this study, we evaluated the effects of hBD-3 on S epidermidis ATCC 35984 (methicillin-resistant strain), MRSE287, and MRSA (ATCC43300) by evaluating bacterial adhesion, biofilm formation, and maturation. In addition, we used the spread plate method, confocal laser scanning microscopy, scanning electron microscopy, and real-time polymerase chain reaction to evaluate the effect of hBD-3. Results After evaluating biofilm adhesion and formation, we found that the number of each strain on the titanium surface was decreased in those groups exposed to 1MIC (minimum inhibitory concentration) of hBD-3 and was significantly lower than the number of colonies of the control. In the initial maturation of the biofilm, the numbers of each strain on the titanium surface from the 2MIC to 6MIC groups were significantly lower than the control. When the concentrations were further increased, hBD-3 was significantly effective against drug-resistant bacteria from the biofilms. Conclusions HBD-3 has the potential to eliminate the biofilm formation of Staphylococcus , especially antibiotic-resistant strains, effectively.

Titania nanotube-based local drug delivery is an attractive strategy for combating implant-associated infection. In our previous study, we demonstrated that the gentamicin-loaded nanotubes could dramatically inhibit bacterial adhesion and biofilm formation on implant surfaces. Considering the overuse of antibiotics may lead to the evolution of antibiotic-resistant bacteria, we synthesized a new quaternized chitosan derivative (hydroxypropyltrimethyl ammonium chloride chitosan, HACC) with a 27% degree of substitution (DS; referred to as 27% HACC) that had a strong antibacterial activity and simultaneously good biocompatibility with osteogenic cells. Titania nanotubes with various diameters (80, 120, 160, and 200 nm) and 200 nm length were loaded with 2 mg of HACC using a lyophilization method and vacuum drying. Two standard strain, methicillin-resistant Staphylococcus aureus (American Type Culture Collection 43300) and Staphylococcus epidermidis (American Type Culture Collection 35984), and two clinical isolates, S. aureus 376 and S. epidermidis 389, were selected to investigate the bacterial adhesion at 6 h and biofilm formation at 24, 48, and 72 h on the HACC-loaded nanotubes (NT-H) using the spread plate method, confocal laser scanning microscopy (CLSM), and scanning electron microscopy (SEM). Smooth titanium (Smooth Ti) was also investigated and compared. We found that NT-H could significantly inhibit bacterial adhesion and biofilm formation on its surface compared with Smooth Ti, and the NT-H with 160 nm and 200 nm diameters had stronger antibacterial activity because of the extended HACC release time of NT-H with larger diameters. Therefore, NT-H can significantly improve the antibacterial ability of orthopedic implants and provide a promising strategy to prevent implant-associated infections.

Biomaterial-associated infections remain a serious complication in orthopaedic surgery. Treatments, including the local use of antibiotic-loaded polymethylmethacrylate (PMMA) bone cement, are not always successful because of multiantibiotic-resistant organisms. In this study, we synthesised a new quaternised chitosan derivative (hydroxypropyltrimethyl ammonium chloride chitosan, HACC) that contains a series of substitutions of quaternary ammonium and demonstrated that HACC with a 26% degree of substitution (DS; referred to as 26%HACC) had a strong antibacterial activity and simultaneously good biocompatibility with osteogenic cells. We loaded 26%HACC at 20% by weight into PMMA bone cement to investigate whether HACC in PMMA prevents bacterial biofilm formation on the surface of bone cements. Chitosan-loaded PMMA (at the same weight ratio), gentamicin-loaded PMMA and PMMA with no antibiotic were also investigated and compared. Two clinical isolates, Staphylococcus epidermidis 389 and methicillin-resistant S. epidermidis (MRSE287), and two standard strains, S. epidermidis (ATCC35984) and methicillin-resistant Staphylococcus aureus (ATCC43300), were selected to evaluate the bacterial biofilm formation at 6, 12 and 24 h using the spread plate method, confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). The results showed that 26%HACC-loaded PMMA inhibited biofilm formation on its surface, while the PMMA control and chitosan-loaded PMMA were unable to inhibit biofilm formation. The gentamicin-loaded PMMA decreased the number of viable methicillin-resistant Staphylococcus strains, but its ability to inhibit biofilm formation was lower than 26%HACC-loaded PMMA. Real-time PCR demonstrated that 26%HACC-loaded PMMA markedly downregulated the expression of icaAD, which encodes essential enzymes for polysaccharide intercellular adhesion (PIA) biosynthesis, upregulated the expression level of icaR, which negatively mediates icaAD expression, and also downregulated the expression of MecA, which encodes membrane-bound enzymes known to be penicillin-binding proteins. Our study indicates that 26%HACC-loaded PMMA prevents biofilm formation of Staphylococcus, including antibiotic-resistant strains, on the surface of bone cement, and downregulates the virulence-associated gene expression of antibiotic-resistant staphylococcus, thus providing a promising new strategy for combating implant infections and osteomyelitis.

Rui Ma,1 Songchao Tang,2 Honglue Tan,1 Wentao Lin,1 Yugang Wang,1 Jie Wei,2 Liming Zhao,2 Tingting Tang1 1Shanghai Key Laboratory of Orthopedic Implants, Department of Orthopedic Surgery, Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, 2Key Laboratory for Ultrafine Materials of Ministry of Education and The State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, People’s Republic of China Abstract: A bioactive composite was prepared by incorporating 40 wt% nano-­hydroxyapatite (nHA) into polyetheretherketone (PEEK) through a process of compounding, injection, and molding. The mechanical and surface properties of the nHA/PEEK composite were characterized, and the in vitro osteoblast functions in the composite were investigated. The mechanical properties (elastic modulus and compressive strength) of the nHA/PEEK composite increased significantly, while the tensile strength decreased slightly as compared with PEEK. Further, the addition of nHA into PEEK increased the surface roughness and hydrophilicity of the nHA/PEEK composite. In cell tests, compared with PEEK and ultra-high-molecular-weight polyethylene, it was found that the nHA/PEEK composite could promote the functions of MC3T3-E1 cells, including cell attachment, spreading, proliferation, alkaline phosphatase activity, calcium nodule formation, and expression of osteogenic differentiation-related genes. Incorporation of nHA into PEEK greatly improved the bioperformance of PEEK. The nHA/PEEK composite might be a promising orthopedic implant material. Keywords: polyetheretherketone, nano-hydroxyapatite, biocomposite, osteoblast functions, orthopedic implant material

Infection of open tibial fractures with contamination remains a challenge for orthopedic surgeons. Local use of antibiotic-impregnated polymethylmethacrylate (PMMA) beads and blocks is a widely used procedure to reduce the risk of infection. However, the development of antibiotic-resistant organisms make the management of infection more difficult. Our in vitro study demonstrated that quaternized chitosan (hydroxypropyltrimethyl ammonium chloride chitosan [HACC])-loaded PMMA bone cement exhibits strong antibacterial activity toward antibiotic-resistant bacteria. Therefore, the present study aimed to investigate the in vivo antibacterial activity of quaternized chitosan-loaded PMMA. Twenty-four adult female New Zealand White rabbits were used in this study. The right proximal tibial metaphyseal cavity was prepared, 10 7 CFU of methicillin-resistant Staphylococcus epidermidis was inoculated, and PMMA-only, gentamicin-loaded PMMA (PMMA-G), chitosan-loaded PMMA (PMMA-C), or HACC-loaded PMMA (PMMA-H) bone cement cylinders were inserted. During the follow-up period, the infections were evaluated using X rays on days 21 and 42 and histopathological and microbiological analyses on day 42 after surgery. Radiographic indications of bone infections, including bone lysis, periosteal reactions, cyst formation, and sequestral bone formation, were evident in the PMMA, PMMA-G, and PMMA-C groups but not in the PMMA-H group. The radiographic scores and gross bone pathological and histopathological scores were significantly lower in the PMMA-H group than in the PMMA, PMMA-G, and PMMA-C groups ( P < 0.05). Explant cultures also indicated significantly less bacterial growth in the PMMA-H group than in the PMMA, PMMA-G, and PMMA-C groups ( P < 0.01). We concluded that PMMA-H bone cement can inhibit the development of bone infections in this animal model inoculated with antibiotic-resistant bacteria, thereby demonstrating its potential application for treatment of local infections in open fractures.

Chondroblastoma of the patella is rare. Aneurysmal bone cysts, which develop from a prior lesion such as a chondroblastoma, are seldom seen in the patella. The authors report a case of a 36-year-old man who presented with 2 years of right knee pain without calor, erythema, pain on palpation, or abnormal range of motion. Radiological studies suggested aneurysmal bone cyst. The lesion was excised with curettage and the residual cavity filled with autogenous bone graft. Histopathology revealed chondroblastoma associated with a secondary aneurysmal bone cyst. In the follow-up period, the patient demonstrated normal joint activities with no pain. Normal configuration of the patella and bone union were shown on plain radiographs. The authors present a review of the literature of all cases of patellar chondroblastoma with aneurysmal bone cyst. This case is the 14th report of aneurysmal bone cyst arising in a chondroblastoma of the patella. According to the literature, computed tomography and magnetic resonance imaging are useful in the study of these lesions. The pathologic diagnosis is based on the presence of chondroblastoma and aneurysmal bone cyst. Treatment of this lesion includes patellectomy, curettage alone, and curettage with bone grafting. Despite the risk of recurrence of this lesion in the patella, the authors first recommend curettage followed by filling the cavity with bone graft. To protect the anterior tension of the patella intraoperatively, the bone window should be made at the medial edge of the patella to perform the curettage and bone grafting.

Wen-tao Lin,1 Hong-lue Tan,1 Zhao-ling Duan,2 Bing Yue,1 Rui Ma,1 Guo He,2 Ting-ting Tang1 1Shanghai Key Laboratory of Orthopedic Implants, Department of Orthopedic Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China; 2State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, People's Republic of China Abstract: Titania nanotubes loaded with antibiotics can deliver a high concentration of antibiotics locally at a specific site, thereby providing a promising strategy to prevent implant-associated infections. In this study we have fabricated titania nanotubes with various diameters (80, 120, 160, and 200 nm) and 200 nm length via electrochemical anodization. These nanotubes were loaded with 2 mg of gentamicin using a lyophilization method and vacuum drying. A standard strain, Staphylococcus epidermidis (American Type Culture Collection 35984), and two clinical isolates, S. aureus 376 and S. epidermidis 389, were selected to investigate the anti-infective ability of the gentamicin-loaded nanotubes (NT-G). Flat titanium (FlatTi) and nanotubes with no drug loading (NT) were also investigated and compared. We found that NT-G could significantly inhibit bacterial adhesion and biofilm formation compared to FlatTi or NT, and the NT-G with 160 nm and 200 nm diameters had stronger antibacterial activity because of the extended drug release time of NT-G with larger diameters. The NT also exhibited greater antibacterial ability than the FlatTi, while nanotubes with 80 nm or 120 nm diameters had better effects. Furthermore, human marrow derived mesenchymal stem cells were used to evaluate the effect of nanotubular topographies on the osteogenic differentiation of mesenchymal stem cells. Our results showed that NT-G and NT, especially those with 80 nm diameters, significantly promoted cell attachment, proliferation, spreading, and osteogenic differentiation when compared to FlatTi, and there was no significant difference between NT-G and NT with the same diameter. Therefore, nanotube modification and gentamicin loading can significantly improve the antibacterial ability and osteogenic activity of orthopedic implants. Keywords: titania nanotubes, gentamicin, bacteria adhesion, biofilm formation, osteogenic activity

The infection of orthopedic implantation devices with Staphylococcus is a serious concern within the biomaterial community. Treatments are not always successful because of antibiotic-resistant bacteria and serious biofilm infections. Human β-defensin 3 (hBD-3) is considered to be the most promising class of defensin antimicrobial peptides and its effect on antibiotic-resistant Staphylococcus biofilms, combined with ultrasound (US)-targeted microbubble (MB) destruction (UTMD), has not been reported. In the study, we found that biofilm densities, the percentage of live cells and the viable counts of two tested Staphylococcus recovered from the biofilm were significantly decreased in the maximum concentration hBD-3 combined with UTMD compared with those of any other groups. Furthermore, results suggested that UTMD could also enhance 1MIC hBD-3 activity inhibiting the biofilm-associated genes expression of icaAD and the methicillin-resistance genes expression of MecA by simultaneously promoting the icaR expression. UTMD may have great potential for improving antibiotic activity against biofilm infections.

Despite improvements in intraoperative antimicrobial procedures, in surgical techniques and in implant design for joint replacement, periprosthetic infection after arthroplasty is still one of the most challenging problems encountered by orthopedic surgeons. Systemic antibiotics are not sufficiently effective to eradicate such deep infections because of the impaired blood circulation and low antibiotic concentration at the implantation site. As a local drug delivery system, antibiotic-impregnated PMMA (polymethylmethacrylate) bone cements have been widely used for prophylaxis or treatment of deep infections after total joint replacement. However, the effectiveness of antibiotic-loaded PMMA in preventing infections after arthroplasty is still controversial. Furthermore, the outcomes of established deep infections treated with this technique are not consistent. The local use of antibiotics has led to the emergence of antibiotic-resistant bacterial strains and has adverse effects on the function of osteogenic cells. Recently, many efforts have been made to identify new antibacterial agents that can be loaded into PMMA. These antimicrobial agents should exhibit good antibacterial activity against antibiotic-resistant strains and should simultaneously enhance osteointegration between the PMMA and the bone tissue. PMMA loaded with chitosan or chitosan derivatives has been demonstrated to induce improved osteogenic activity and to exhibit antibacterial activity in a preclinical study.

Summary Our previous studies have demonstrated that the quaternised chitosan-loaded polymethylmethacrylate (PMMA) is a promising new antibacterial bone cement. The aim of this study was to evaluate biomechanical properties of quaternised chitosan-loaded PMMA in vitro and interface histology between cement and bone in vivo. In this study, hydroxypropyltrimethyl ammonium chloride chitosan (HACC) with 26% degree of substitution (referred to as 26% HACC) was loaded into PMMA bone cement at a 20% mass ratio, and the specimens of 26% HACC-loaded PMMA bone cement (PMMA–H) were prepared for compressive and bending mechanical test according to ISO 5883-2002 standard prior to and after the 4-week immersion in PBS. The chitosan-loaded PMMA bone cement (PMMA–C) at the same mass ratio, pure PMMA, and gentamicin-loaded PMMA (PMMA–G) were also prepared and tested as controls. Then each of four kinds of bone cements was implanted into the rabbit femoral condyle and the osseointegration of the cement–bone interface was evaluated after its implantation over 6 weeks. The results show that biomechanical properties of both PMMA–C and PMMA–H were reduced significantly compared with the PMMA or PMMA–C, and the elastic modulus of PMMA–H was close to that of human cancellous bone. Histological observation in animal studies indicates that there was better osseointegration at the cement–bone interface in the PMMA–H group than that in the PMMA, PMMA–G, or PMMA–C groups. More new bone formation was found around PMMA–H bone cement as compared with that in the other three groups. Our findings indicated that the biomechanical properties of PMMA–H were reduced but close to that of neighbouring bone. The PMMA–H had good biocompatibility and osseointegration potential, implying its suitability for vertebral augmentation of osteoporotic vertebral compression fractures and fixation of prosthesis in cemented joint replacement.