Shuichi Eto

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.

Problems and Management of Venous Thromboenbolism Following Primary Total Hip Arthroplasty

対象は2008年4月から2010年4月まで当院にて施行した初回THA中，術後2日目，7日目に下肢静脈エコーを施行し術後6日目にD-ダイマーを施行した185例．男性38例，女性147例．平均年齢65.0歳．基本的にメドマーを術直後から開始し低分子ヘパリンを硬膜外チューブ抜去後から開始した．DVTを22例（11.9％）に認めたが症候性のPEは認めなかった．統計学的に術後6日目D-ダイマーのカットオフ値10μg/mlはDVT検出に有効であった．また術後7日目に初めてDVTを発症した5例はすべて術後6日目D-ダイマーが10μg/ml以上であった．当院における術後DVT発生率は11.9％であり他の研究と比較して遜色はなかった．今後も致死性のPEを防ぐため注意深く予防と検査を進めていく必要がある．

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．