Masatsugu Tsukamoto

Silver oxide-containing hydroxyapatite coating has in vivo antibacterial activity in the rat tibia

Bacterial infection is a serious postoperative complication of joint replacement. To prevent infections related to implantation, we have developed a novel antibacterial coating with Ag‐containing hydroxyapatite (Ag‐HA). In the present study, we examined the antibacterial activity of Ag‐HA implant coatings in the medullary cavity of rat tibiae. Forty 10‐week‐old rats received implantation of Ag‐HA‐ or HA‐coated titanium rods, then were inoculated with ∼1.0 × 102 colony‐forming units of methicillin‐resistant Staphylococcus aureus. Bacterial counts were calculated for rats euthanized at 24, 48, and 72 h postoperatively. Serum levels of Ag (in the Ag‐HA group only) were calculated for rats euthanized at 24, 48, 72 h and 4 weeks. Radiographic evaluations of bone infection were also performed at 4 weeks. Tibiae from both groups showing infection were evaluated histologically. Significant differences in bacterial counts were seen at 24, 48, and 72 h. Mean concentrations of Ag in serum peaked about 48 h after implantation, then gradually decreased. Mean radiographic scores for infection were significantly lower with Ag‐HA implants than with HA implants. Histological examination showed better results for abscesses, bone resorption, and destruction of cortical bone around Ag‐HA‐coated implants. These results indicate that Ag‐HA coatings may help prevent surgical‐site infections associated with joint replacement.

Silver oxide-containing hydroxyapatite coating supports osteoblast function and enhances implant anchorage strength in rat femur.

Antibacterial silver with hydroxyapatite (Ag–HA) is a promising coating material for imparting antibacterial properties to implants. We previously reported that 3% (w/w) silver with HA (3% Ag–HA) has both antibacterial activity and osteoconductivity. In this study, we investigated the effects of Ag–HA on the in vitro osteoblast function and the in vivo anchorage strength and osteoconductivity of implants. Production of the osteoblast marker alkaline phosphatase, but not cytotoxicity, was observed in cells of the osteoblast cell line MC3T3‐E1 cultured on the 3% Ag–HA‐coated surface. These results were similar to those observed with silver‐free HA coating. In contrast, a significant high level of cytotoxicity was observed when the cells were cultured on a 50% Ag–HA‐coated surface. The anchorage strength of implants inserted into the femur of Sprague–Dawley (SD) rats was enhanced by coating the implants with 3% Ag–HA. On the 3% Ag–HA‐coated surface, both metaphyseal and diaphyseal areas were largely covered with new bone and had adequate osteoconductivity. These results suggest that 3% Ag–HA, like conventional HA, promotes osteogenesis by supporting osteoblast viability and function and thereby contributes to sufficient anchorage strength of implants. Application of 3% Ag–HA, which combines the osteoconductivity of HA and the antibacterial activity of silver, to prosthetic joints will help prevent postoperative infections.

Silver-Containing Hydroxyapatite Coating Reduces Biofilm Formation by Methicillin-Resistant Staphylococcus aureus In Vitro and In Vivo

Biofilm-producing bacteria are the principal causes of infections associated with orthopaedic implants. We previously reported that silver-containing hydroxyapatite (Ag-HA) coatings exhibit high antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). In the present study, we evaluated the effects of Ag-HA coating of implant surfaces on biofilm formation. Titanium disks (14-mm diameter, 1-mm thickness), one surface of which was coated with HA or 0.5%–3.0% Ag-HA with a thermal spraying technique, were used. In vitro, the disks were inoculated with an MRSA suspension containing 4 × 105 CFU and incubated for 1-2 weeks. In vivo, MRSA-inoculated HA and 3% Ag-HA disks (8.8–10.0 × 108 CFU) were implanted subcutaneously on the back of rats for 1–7 days. All disks were subsequently stained with a biofilm dye and observed under a fluorescence microscope, and biofilm coverage rates (BCRs) were calculated. The BCRs on the Ag-HA coating were significantly lower than those on the HA coating at all time points in vitro (p < 0.05). Similar results were observed in vivo (p < 0.001) without argyria. Ag-HA coating reduced biofilm formation by MRSA in vitro and in vivo; therefore, Ag-HA coating might be effective for reducing implant-associated infections.

Acute and subacute toxicity in vivo of thermal-sprayed silver containing hydroxyapatite coating in rat tibia.

To reduce the incidence of implant-associated infection, we previously developed a novel coating technology using hydroxyapatite (HA) containing silver (Ag). This study examined in vivo acute and subacute toxicity associated with the Ag-HA coating in rat tibiae. Ten-week-old rats received implantation of HA-, 2% Ag-HA-, or 50% Ag-HA-coated titanium rods. Concentrations of silver in serum, brain, liver, kidneys, and spleen were measured in the acute phase (2–4 days after treatment) and subacute phase (4–12 weeks after treatment). Biochemical and histological examinations of those organs were also performed. Mean serum silver concentration peaked in the acute phase and then gradually decreased. Mean silver concentrations in all examined organs from the 2% Ag-HA coating groups showed no significant differences compared with the HA coating group. No significant differences in mean levels of glutamic-oxaloacetic transaminase, glutamic-pyruvic transaminase, lactate dehydrogenase, creatinine, or blood urea nitrogen were seen between the three groups and controls. Histological examinations of all organs revealed no abnormal pathologic findings. No acute or subacute toxicity was seen in vivo for 2% Ag-HA coating or HA coating. Ag-HA coatings on implants may represent biologically safe antibacterial biomaterials and may be of value for reducing surgical-site infections related to implantation.

Minimally Invasive Endoscopic Approach to the Cervicothoracic Junction for Vertebral Osteomyelitis

The selection of an anterior, lateral, or posterior approach to the cervicothoracic junction for surgical treatment of vertebral osteomyelitis is still a matter of debate. These ordinary approaches generally require an extensile exposure. This article describes a less invasive approach case of a vertebral osteomyelitis of T2/3 using a video-assisted operating technique of thoracic surgery (VATS). A 78-year-old female underwent anterior debridement and interbody fusion with bone graft at T2/3 using a lateral surgical approach through a right thoracotomy with VATS. The VATS through two small skin incisions in the axillary region provides a good view without requiring elevation of the scapula with extensile muscle dissection and rib resection. There was no complication without partial lobectomy due to pleural adhesion during the perioperative period. Currently, at 1 year after operation, the patient has no back pain with neurologically normal findings and no inflammation findings (CRP was 0.01 mg/dl). Although the operating field of the upper thoracic level in the lateral approach is generally deep and narrow, the VATS provides a good view and allows us to perform adequate debridement and bone fusion at the T2/3 level with a less invasive approach than those previously described anterior or laterally or posterior approach.

Effects and Problems of DPC (Diagnosis Procedure Combination): A Study on Femoral Neck Fractures

日本において，診断群分類に基づく包括点数評価（以下DPC）を導入している病院は，増加している．DPCの特徴は，医療情報の標準化・透明性にあり，このツールで各病院間を解析し医療の質の向上を図ることが目的とされている．我々は，DPC導入直後と，DPC導入後3年経過時，平均年齢（才），診療報酬点数（点），平均在院日（日），術前待機期間（日），再入院の有無について調査した．結果として，DPC導入後3年経過時に，平均在院日数は50％に減少，術前待機期間は約30％に減少，診療報酬点数は70％に減少した．医療経済学的な面からDPCの効果ありと判断した．しかし点数設定の決定過程はブラックボックスにあり，専門医学会からの監視が必要で今後検討の余地がある．