Language：Japanese   Publisher：日本臨床バイオメカニクス学会  

変形性膝関節症(膝OA)の異常運動lateral thrust(LT)はOA進行要因として主に歩行解析や筋力との関連で検討される。3次元アライメント評価を行った非OAと進行期OA女性各15例に対し、非荷重位(臥位:CT撮像位)と荷重位(立位:2方向X線画像と骨3DCTモデルのマッチング)間における大腿骨・脛骨間の相対位置変化を冠状面方向で評価した。非OA、OAの両例において非荷重位と立位荷重位を比較すると、荷重により脛骨内側関節面が大腿骨関節面に接近した位置にあり、脛骨は大腿骨に対して外側に位置していた。また、側方への移動量は非OAに比してOAが大きいことを確認した。膝OAのLTは脛骨近位内側関節面への偏荷重を荷重面水平化の方向に位置修正を行い、その際大腿骨内側関節接触点を中心とした脛骨の相対位置移動としての評価が可能なことを示唆した。(著者抄録)

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Language：Japanese   Publisher：日本臨床バイオメカニクス学会  

大規模集団検診(松代膝検診)で確認した変形性膝関節症(膝OA)進行に伴う膝前後単純X線画像上の下腿骨位置や形状の定量的評価で膝OA進行度判定が可能と考え、半自動評価システムを開発した。松代膝検診第5回(2007年)から12年間の5回をすべて受診した対象のうち、任意で抽出した男女各10名の単純X線画像を対象に測定の信頼性を評価および従来の手動デジタイズ法との測定精度と測定時間を比較検討した。測定の信頼性として検者内では級内相関係数:ICC=0.98、検者間ではICC=0.96、従来法との比較でもICC=0.96と高い信頼性を示した。また、評価指標で、脛骨関節面傾斜、関節裂隙幅比の減少、脛骨内側皮質骨幅比の増加、FTAの増加など過去に報告した膝OA進行に伴う変化が算出された。特に、骨の参照軸の自動抽出により測定値の安定とこれによる測定時間が約1/3に短縮した。(著者抄録)

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Language：Japanese   Publisher：日本臨床バイオメカニクス学会  

本研究では、成人10名の上下顎骨を撮影したコーンビームCT画像から骨モデルを三次元再構成し、解剖学的特徴箇所である下顎両側オトガイ孔2点および上顎切歯管1点を利用して口腔内に三次元ワールド座標系を構築し、全ての歯の三次元モデルを作成した。各歯の幾何学的重心(COG)と主成分分析法で計算した歯軸(PC-A)を求め、空間内のCOGとPC-Aを横断面、冠状面および矢状面上に投影して、各平面内でのPC-A角度とCOGによる歯列を示した。その結果、冠状面では、上顎歯は全て頬側に歯が傾き、下顎歯は、中切歯、側切歯、犬歯、第一小臼歯は頬側に向いているが、第二小臼歯、第一、第二大臼歯は舌側を向く。矢状面では、上顎歯は第二大臼歯だけが遠心側に傾いているのに対し、下顎歯は全て近心側に傾くという一般的な正常咬合者の特徴を定量的に明らかにした。さらに、3平面内におけるCOG位置とPC-A角度との関係を表す回帰曲線は、簡潔な多項式で表現できることを示した。(著者抄録)

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Language：Japanese   Publisher：日本臨床バイオメカニクス学会  

変形性膝関節症(膝OA)の異常運動lateral thrust(LT)はOA進行要因として主に歩行解析や筋力との関連で検討される。3次元アライメント評価を行った非OAと進行期OA女性各15例に対し、非荷重位(臥位:CT撮像位)と荷重位(立位:2方向X線画像と骨3DCTモデルのマッチング)間における大腿骨・脛骨間の相対位置変化を冠状面方向で評価した。非OA、OAの両例において非荷重位と立位荷重位を比較すると、荷重により脛骨内側関節面が大腿骨関節面に接近した位置にあり、脛骨は大腿骨に対して外側に位置していた。また、側方への移動量は非OAに比してOAが大きいことを確認した。膝OAのLTは脛骨近位内側関節面への偏荷重を荷重面水平化の方向に位置修正を行い、その際大腿骨内側関節接触点を中心とした脛骨の相対位置移動としての評価が可能なことを示唆した。(著者抄録)

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Language：Japanese   Publisher：日本臨床バイオメカニクス学会  

大規模集団検診(松代膝検診)で確認した変形性膝関節症(膝OA)進行に伴う膝前後単純X線画像上の下腿骨位置や形状の定量的評価で膝OA進行度判定が可能と考え、半自動評価システムを開発した。松代膝検診第5回(2007年)から12年間の5回をすべて受診した対象のうち、任意で抽出した男女各10名の単純X線画像を対象に測定の信頼性を評価および従来の手動デジタイズ法との測定精度と測定時間を比較検討した。測定の信頼性として検者内では級内相関係数:ICC=0.98、検者間ではICC=0.96、従来法との比較でもICC=0.96と高い信頼性を示した。また、評価指標で、脛骨関節面傾斜、関節裂隙幅比の減少、脛骨内側皮質骨幅比の増加、FTAの増加など過去に報告した膝OA進行に伴う変化が算出された。特に、骨の参照軸の自動抽出により測定値の安定とこれによる測定時間が約1/3に短縮した。(著者抄録)

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Language：Japanese   Publisher：日本臨床バイオメカニクス学会  

本研究では、成人10名の上下顎骨を撮影したコーンビームCT画像から骨モデルを三次元再構成し、解剖学的特徴箇所である下顎両側オトガイ孔2点および上顎切歯管1点を利用して口腔内に三次元ワールド座標系を構築し、全ての歯の三次元モデルを作成した。各歯の幾何学的重心(COG)と主成分分析法で計算した歯軸(PC-A)を求め、空間内のCOGとPC-Aを横断面、冠状面および矢状面上に投影して、各平面内でのPC-A角度とCOGによる歯列を示した。その結果、冠状面では、上顎歯は全て頬側に歯が傾き、下顎歯は、中切歯、側切歯、犬歯、第一小臼歯は頬側に向いているが、第二小臼歯、第一、第二大臼歯は舌側を向く。矢状面では、上顎歯は第二大臼歯だけが遠心側に傾いているのに対し、下顎歯は全て近心側に傾くという一般的な正常咬合者の特徴を定量的に明らかにした。さらに、3平面内におけるCOG位置とPC-A角度との関係を表す回帰曲線は、簡潔な多項式で表現できることを示した。(著者抄録)

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Publishing type：Research paper (scientific journal)   Publisher：IOS Press  

BACKGROUND: The patellar and quadriceps tendons are responsible for the extension mechanism of the knee joint and frequently become inflamed during sports. Diagnosis and determination of when an athlete can return to sports following these injuries are usually performed by assessing morphological features and functional outcomes. Nevertheless, mechanical properties are not being assessed. OBJECTIVE: To describe the stiffness characteristics of these two tendons over the range of knee flexion and to test the feasibility of using strain ultrasound elastography (SE). METHODS: SE with an acoustic coupler as the reference was performed for nine healthy males. Relative stiffness measurements were obtained using the strain ratio (SR = target tissue strain/reference strain) by placing the knee in five different flexion angles. Lower SR indicates higher relative stiffness. RESULTS: This study showed reliable measurement with good intra- and inter-rater agreement for SR at 30°. SR of the quadriceps tendon decreases as knee flexion increases, indicating increased relative stiffness. In the patellar tendon, no significant difference was observed between 30° and 60°. Beyond 60°, relative stiffness increased constantly. CONCLUSIONS: SE is a reproducible and feasible tool to monitor relative stiffness of the patellar and quadriceps tendons in routine clinical settings.

DOI： 10.3233/bme-206016

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.jos.2021.03.009

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Language：Japanese   Publisher：金原出版(株)  

＜文献概要＞本解説では,上下顎骨を撮影したコーンビームCT画像を用いてわれわれが考案した個人特有の三次元口腔内ワールド座標系に基づき,歯の形状重心から求めた三次元歯列を表現し,歯の三次元形状から主成分分析法で数学的に求めた歯の長軸方向である三次元歯軸も併せて示す新たな解析方法について述べた。はじめに,コーンビームCT画像の下顎の両側オトガイ孔2点と上顎切歯管1点を用いた解剖学的特徴点から構築した個人ごとの三次元口腔内ワールド座標系を新たに定義した。次に,正常咬合者を対象に歯列曲線や歯軸を口腔内座標系に基づいて定量的に表現した解析結果例より,上下顎歯列に対して,横断面では4次偶多項式,冠状面では6次偶多項式,矢状面では3次多項式でそれぞれの面内の歯列を数学的に表現できることを示した。

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Language：English   Publishing type：Research paper (scientific journal)  

BACKGROUND: Identifying the time course of rotational knee alignment is crucial for elucidating the etiology in knee osteoarthritis. OBJECTIVE: The aim of this study was to propose new rotational indices for calculating the change in relative rotational angles between the femur and tibia in standing anteroposterior (AP) radiographs. METHODS: Forty healthy elderly volunteers (20 women and 20 men; mean age, 70 ± 6 years) were assessed. The evaluation parameters were as follows: (1) femoral rotational index: the distance between the sphere center of the medial posterior femoral condyle and the lateral edge of the patella, and (2) tibial rotational index: the distance between the medial eminence of the tibia and the lateral edge of the fibula head. The indices were standardized by the diameter of the sphere of the medial posterior femoral condyle. This study (1) identified the relationship between changes in rotational indices and the simulated rotational knee angles in the standing position, (2) proposed a regression equation for the change in relative rotational angles between the femur and tibia in standing AP radiographs, and (3) verified the accuracy of the regression equation. RESULTS: The rotational indices increased in direct proportion to simulated rotational knee angles (femoral index: r > 0.9,p < 0.0001; tibial index: r > 0.9, p < 0.0001). Based on the results, the regression equation with the accuracy of 0.45 ± 0.26° was determined. CONCLUSIONS: The proposed regression equations can potentially predict the change in relative rotational angles between the femur and tibia in a pair of standing AP radiographs taken at different dates in longitudinal studies.

DOI： 10.3233/BME-201138

PubMed

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Language：English   Publishing type：Research paper (scientific journal)  

PURPOSE: The purpose of this study was to three-dimensionally analyse the size and shape of the femoral posterior condyles of the normal knee. METHODS: A total of 62 healthy Japanese volunteers (37 males and 25 females) providing a sample of 124 normal knee joints, who had no knee-related symptoms and no history of major trauma, underwent computed tomography scans of the bilateral femur and tibia. Three-dimensional digital models of the femur were constructed from computed tomography data using visualisation and modelling software. The following parameters were evaluated: (1) the radii of the posterior condyles approximated to spheres and (2) the inclination angle of the posterior condyles in the coronal plane of the femoral coordinate system. RESULTS: The radii of the medial and lateral condyles approximated to spheres were 17.0 ± 1.6 and 17.1 ± 1.8 mm, respectively and were not different. The inclination angles of the medial and lateral condyles in the coronal plane were - 0.6° ± 4.6° and 9.7° ± 5.7°, respectively. The medial condyle was almost vertical, whereas the lateral one was medially tilted. CONCLUSIONS: This study found an asymmetrical inclination between medial and lateral condyles. This may be related to the asymmetrical motion of the knee, which is known as medial pivot motion. This finding provides valuable morphological information and may be useful for implant designs for total knee arthroplasty. LEVEL OF EVIDENCE: IV.

DOI： 10.1007/s00167-020-05856-2

PubMed

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Language：English   Publishing type：Research paper (scientific journal)  

PURPOSE: This study aimed to evaluate the age- and sex-related characteristics in cortical thickness of the tibial diaphysis between non-obese healthy young and elderly subjects as reference data. METHODS: The study investigated 31 young subjects (12 men and 19 women; mean age, 25 ± 8 years) and 54 elderly subjects (29 men and 25 women; mean age, 70 ± 6 years). Three-dimensional estimated cortical thickness of the tibial diaphysis was automatically calculated for 5000-9000 measurement points using the high-resolution cortical thickness measurement from clinical computed tomography data. In 12 assessment regions created by combining three heights (proximal, central, and distal diaphysis) and four areas of the axial plane at 90° (medial, anterior, lateral, and posterior areas) in the tibial coordinate system, the standardized thickness was assessed using the tibial length. RESULTS: As structural characteristics, there were no differences in the medial and lateral thicknesses, while the anterior thickness was greater than the posterior thickness in all groups. The sex-related difference was not shown. As an age-related difference, elderly subjects showed greater or lesser cortical thickness than the young subjects, depending on the regions of the tibia. CONCLUSIONS: Cortical thickness was different depending on sex, age, and regions in the tibia. The results of this study are of clinical relevance as reference points to clarify the causes of various pathological conditions for diseases. LEVEL OF EVIDENCE: Level 3.

DOI： 10.1186/s40634-020-00297-9

PubMed

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Language：English   Publishing type：Research paper (scientific journal)  

PURPOSE: To test the hypothesis that an inclined articular surface on the medial proximal tibia is aligned more parallel to the ground in three-dimensional (3D) space under weight-bearing (WB) conditions (parallel phenomenon) than under non-WB (NWB) conditions in healthy and varus osteoarthritic knees. METHODS: We examined 55 healthy knees (26 women, 29 men; mean age, 70 ± 6 years) and 108 varus osteoarthritic knees (66 women, 16 men; mean age, 74 ± 7 years). For the evaluation under WB conditions, a 3D assessment system was used on biplanar long-leg radiographs and 3D bone models using a 3D-to-2D image registration technique. In addition, the least square method was used to determine the approximation plane. The angles between the normal vector for the approximation plane of an articular surface on the medial proximal tibia and each axis of the tibial or world coordinate system were calculated. RESULTS: Morphologically, the inclination of the approximation plane was steeper in osteoarthritic knees than in healthy knees (p < 0.0001). The approximation plane was aligned more parallel to the ground under WB conditions than under NWB conditions in healthy (p < 0.0001) and osteoarthritic knees (p < 0.0001). CONCLUSIONS: The parallel phenomenon in the medial proximal tibia was confirmed for healthy and varus osteoarthritic knees. The medial proximal tibia plays an important role in the parallel phenomenon, assumingly associated with varus alignment and varus thrust. The inclination of the medial proximal tibia may become a new parameter for imaging investigations. LEVEL OF EVIDENCE: III.

DOI： 10.1007/s00167-019-05829-0

PubMed

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Language：Japanese   Publisher：日本臨床バイオメカニクス学会  

変形性膝関節症の初期における下肢アライメントや骨形態変化を明らかにするために、大規模集団検診(松代膝検診)の第5回から8回目(2007年から2016年)においてK-L分類grade 0および1からgrade 2へと移行した142名237膝(男性65名111膝、女性77名126膝、平均年齢71.2±7.4歳)の立位膝前後X線画像を調査した。1)内外側関節裂隙幅比、2)脛骨軸傾斜角度、3)FTA、4)大腿骨と脛骨間の相対的な回旋角度を縦断的に評価した。その結果、内側関節裂隙の狭小、外側の拡大、FTAの増加、脛骨軸傾斜角度の減少はgradeの進行に伴いすべて有意な変化を示し、加えて大腿骨が脛骨に対して外旋する傾向がみられた。また、脛骨軸傾斜がFTAと外側関節裂隙幅比との相関を示し、脛骨の内側傾斜の増大が膝関節の内反変形の初期変化として、大腿-脛骨間のアライメント変化に影響を及ぼし、内反変形の進行の一因となっていることが示唆された。(著者抄録)

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Language：Japanese   Publisher：日本臨床バイオメカニクス学会  

変形性膝関節症の初期における下肢アライメントや骨形態変化を明らかにするために、大規模集団検診(松代膝検診)の第5回から8回目(2007年から2016年)においてK-L分類grade 0および1からgrade 2へと移行した142名237膝(男性65名111膝、女性77名126膝、平均年齢71.2±7.4歳)の立位膝前後X線画像を調査した。1)内外側関節裂隙幅比、2)脛骨軸傾斜角度、3)FTA、4)大腿骨と脛骨間の相対的な回旋角度を縦断的に評価した。その結果、内側関節裂隙の狭小、外側の拡大、FTAの増加、脛骨軸傾斜角度の減少はgradeの進行に伴いすべて有意な変化を示し、加えて大腿骨が脛骨に対して外旋する傾向がみられた。また、脛骨軸傾斜がFTAと外側関節裂隙幅比との相関を示し、脛骨の内側傾斜の増大が膝関節の内反変形の初期変化として、大腿-脛骨間のアライメント変化に影響を及ぼし、内反変形の進行の一因となっていることが示唆された。(著者抄録)

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Language：English   Publishing type：Research paper (scientific journal)  

INTRODUCTION: Cortical thickness of the femoral diaphysis is assumed to be a preferred parameter in the assessment of the structural adaptation by mechanical use and biological factors. This study aimed to investigate the age- and sex-specific characteristics in cortical thickness of the femoral diaphysis between young and elderly non-obese people. MATERIALS AND METHODS: This study investigated 34 young subjects (21 men and 13 women; mean age: 27 ± 8 years) and 52 elderly subjects (29 men and 23 women; mean age: 70 ± 6 years). Three-dimensional (3D) cortical thickness of the femoral diaphysis was automatically calculated for 5000-8000 measurement points using the high-resolution cortical thickness measurement from clinical CT data. In 12 assessment regions created by combining three heights (proximal, central, and distal diaphysis) and four areas of the axial plane at 90° (medial, anterior, lateral, and posterior areas) in the femoral coordinate system, the standardized thickness was assessed using the femoral length. RESULTS: As per the trends, (1) there were no differences in medial and lateral thicknesses, while the posterior thickness was greater than the anterior thickness, (2) the thickness in men was higher than that in women, and (3) the thickness in young subjects was higher than that in elderly subjects. CONCLUSIONS: The results of this study are of clinical relevance as reference points to clarify the causes of various pathological conditions for diseases of the lower extremities.

DOI： 10.1007/s00774-019-01079-9

PubMed

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japanese Society for Experimental Mechanics  

<p> Trapeziometacarpal joint (TMC joint) of thumb is one of the joints having a complicated shape which enables to generate a wide variation of finger movements in daily life. It is important to clarify the accurate in vivo contact behavior of healthy TMC joint when evaluating post-operative joint movements. Thus, author analyzed TMC joint contact behavior in 4 different finger positions of 8 healthy adult males using magnetic resonance imaging (MRI) system. From MR images, three-dimensional bone models were constructed and a three-dimensional coordinate system was defined by the characteristic shape of each bone model. Then, three bone axial angles and three-dimensional bone motion of each 4 positions in the TMC joint were calculated: abduction-adduction, extension-flexion, pronation-supination, and Euler angles. Furthermore, contact areas of the articular cartilage in each of 4 positions were clarified from MR images. Results have shown that, the contact area changed with changing of the thumb position and it was maximum oat the thumb extension. In addition, it was clarified that the contact area moved according to the thumb position.</p>

DOI： 10.11395/jjsem.20.39

CiNii Article

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

DOI： 10.1299/jbse.19-00616

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Language：Japanese  

J-GLOBAL

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Language：Japanese  

J-GLOBAL

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Language：Japanese  

J-GLOBAL

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Language：Japanese   Publisher：日本臨床バイオメカニクス学会  

二次元X線画像から大腿・脛骨間の相対的な回旋を評価するため、変形性膝関節症疫学調査(松代膝検診)の第5回から8回(2007年から2016年)においてK-L分類grade 0からgrade 2へ移行した26名41膝の立位膝X線像を対象とし、大腿骨内側顆長軸の長さ(M)、大腿骨内側顆長軸から膝蓋骨外側縁までの距離(P)、脛骨内側顆間隆起近位端から腓骨頭外側縁までの距離(F)を用いた「大腿骨回旋指標(P/M)」および「脛骨回旋指標(F/M)」を用いて大腿・脛骨間の相対回旋角度を算出した。その結果、grade 0からgrade 2へと進行する過程で、41膝中31膝(76%)が大腿骨に対して脛骨が内旋傾向であった。健常から早期OAへの過程で大腿骨・脛骨間の相対的な回旋変化がOAの進行の要因の一つとして推察され、内反変形との関連の調査が必要である。(著者抄録)

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Language：Japanese   Publisher：(公社)日本整形外科学会  

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Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1007/s00586-019-06118-7

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BACKGROUND: The inclination of the medial compartment of the proximal tibia (MCT) is assumed to be a critical factor for varus alignment in advanced knee osteoarthritis (OA). This study was aimed at investigating; (1) whether the inclination of MCT is aligned parallel to the ground under weight-bearing (WB) conditions; (2) whether this is associated with the change in alignment and the relative position between the bones; and (3) whether the tibia or femur mainly contributes to the changes. METHODS: We examined 102 knees (84 women, 18 men; mean 75 years). A three-dimensional (3D) assessment system was applied on biplanar whole lower extremity radiographies using 3D-to-2D image registration technique. The evaluation parameters were 1) MCT angle, 2) femorotibial angle (FTA), 3) medial-lateral femoral location to the tibia (M-L femoral location), 4) WB line passing point, and 5) tibial position to WB line (tibial position) and 6) femoral postion to WB line (femoral position). Each parameter was evaluated in non-WB and WB conditions, and the differences (Δ-parameters). RESULTS: MCT angle in the world coordinate system was larger than that in the tibial coordinate system (p <  0.0001). ΔMCT angle was correlated with ΔFTA (p = 0.002) and ΔM-L femoral location (p = 0.004). The tibial position was the more dominant factor for ΔMCT angle (p = 0.001), ΔFTA (p <  0.0001), and ΔWB line passing point (p <  0.0001) . CONCLUSIONS: The inclination in MCT was aligned parallel to the ground under WB conditions (tibial parallel phenomenon). The parallel phenomenon was associated with the change of alignment and the relative position between the bones in the coronal plane. These phenomena were produced mainly by the tibia, not the femur. LEVEL OF EVIDENCE: Level IV.

DOI： 10.1186/s40634-019-0180-x

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Language：Japanese   Publisher：(公社)日本整形外科学会  

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Language：Japanese   Publisher：(公社)日本放射線技術学会  

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BACKGROUND: In vivo evaluation of the elastic properties of the knee joint capsule has not been adequately performed. OBJECTIVES: To establish a methodology to assess the stiffness of the normal knee joint capsule over a range of knee flexion angles using ultrasound elastography. METHODS: Ultrasound elastography with an acoustic coupler was used to assess the stiffness of the anteromedial capsule of the knee joints of 10 male (mean age 22.63 ± 1.02 years) and 10 female (mean age 21.6 ± 0.8 years) subjects at static knee flexion angles of 0°, 45°, 90°, and 120°. Relative stiffness of the capsule was obtained using the strain ratio (SR), defined as the ratio of the strain in the capsule to that in the acoustic coupler. RESULTS: The intraclass correlation coefficient (1, 3) ranged from 0.95 to 0.96, and the correlation coefficient between examiners (2, 3) was 0.94. SR values decreased significantly as the flexion angle increased (P < 0.01). At 90° and 120°, it was significantly higher in female than in male subjects (P < 0.01). CONCLUSIONS: This study established a feasible and reproducible method to obtain the stiffness characteristics of the anteromedial knee joint capsule using ultrasound elastography with an acoustic coupler.

DOI： 10.3233/BME-191046

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmemecj.2019.J02513

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We focus on an elastic contact problem for indentation of a layer-substrate body. An elastic layer assumed to be perfectly bonded to an elastic semi-infinite substrate. The elastic layer is smoothly indented with a flat-ended cylindrical indenter and a spherical indenter. The analytical and exact solutions are obtained by solving an infinite system of simultaneous equations using the method to express a normal contact stress at the upper surface of the elastic layer as an appropriate series. This paper presents not only the axial load but also the distribution of the dimensionless normal contact stress under cylindrical and spherical indentation, the distribution of the dimensionless normal displacement at the upper surface of the elastic layer and the stress singularity factor. Numerical results are given for several combinations of the ratio of shear modulus and Poisson&rsquo;s ratios of the elastic layer and substrate, and the thickness of the elastic layer.

DOI： 10.11345/nctam.64.81

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INTRODUCTION: Posterior tibial slope (PTS) and sagittal alignment are important factors in the etiology of knee osteoarthritis and knee surgery. Clinically, sagittal alignment, which indicates flexion contracture of the knee, contributes to knee function in weight-bearing (WB) conditions. PTS and sagittal alignment under WB conditions in varus osteoarthritic knees are presumed to affect each other, but their association remains unclear. In this study, we aimed to clarify the association. MATERIAL AND METHODS: In total, 140 osteoarthritic varus knees were investigated. Under WB conditions, a three-dimensional (3D) alignment assessment system was applied via biplanar long-leg X-rays, using 3D-to-2D image registration technique. The evaluation parameters were as follows: 1) 3D mechanical flexion angle (3DMFA) in regards to sagittal alignment, 2) passing point in the WB line (PP), and 3) medial and lateral PTS. RESULTS: The medial and lateral PTS showed a positive correlation with 3DMFA and PP, respectively (medial PTS-3DMFA, p = 0.001; medial PTS-PP, p < 0.0001; lateral PTS-3DMFA, p < 0.0001; lateral PTS-PP, p = 0.002). The flexion contracture group with 3DMFA >5° demonstrated greater PTS than non-flexion contracture group (medial PTS, p = 0.006; lateral PTS, p = 0.006). CONCLUSIONS: Both medial and lateral PTS were correlated with sagittal alignment under WB conditions and were larger in the flexion contracture group. This finding can explain the function to take the load articular surface parallel to the ground for holding the balance in WB conditions in the sagittal plane for osteoarthritic knees. Moreover, surgeons may be required to decrease the PTS during knee arthroplasty to restore full extension in knees of patients with fixed flexion contracture.

DOI： 10.1371/journal.pone.0202488

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BACKGROUND: Humans support their bodies exclusively by vertical balance in bipedal locomotion, and the body, especially the lower extremity, generally changes with age. Sex and body constitution are assumed to be associated with lower extremity alignment, but this association remains to be elucidated. This study sought to clarify this association in healthy, elderly, non-obese humans in a Japanese population. METHODS: The present study investigated 55 healthy volunteers (mean age: 70 ± 6 years). A 3D extremity alignment system was applied under weight-bearing conditions on biplane long lower extremities X-rays using a 3D-to-2D image registration technique. The evaluation parameters included 3D hip-knee-ankle angle (3DHKA) alignment in the coronal (coronal alignment) and sagittal planes (sagittal alignment) and rotational alignment between the femur and tibia. The influences of sex and body constitution on all the alignment were analyzed. RESULTS: Multiple linear regression analysis with the dependent variable of each alignment showed that sex was the dominant factor for coronal and rotational alignment (coronal: p <  0.01; rotational: p <  0.01), and body weight was the dominant factor for sagittal alignment (p <  0.01). CONCLUSIONS: The association of sex with coronal and rotational alignment and of body constitution with sagittal alignment were proved in healthy, elderly, non-obese humans in a Japanese population. This finding can lead to further understanding of the etiology of many diseases and age-related changes.

DOI： 10.1186/s40634-018-0147-3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Churchill Livingstone Inc.  

Background: This study aimed to identify the factors affecting postoperative rotational limb alignment of the tibia relative to the femur. We hypothesized that not only component positions but also several intrinsic factors were associated with postoperative rotational limb alignment. Methods: This study included 99 knees (90 women and 9 men) with a mean age of 77 ± 6 years. A three-dimensional (3D) assessment system was applied under weight-bearing conditions to biplanar long-leg radiographs using 3D-to-2D image registration technique. The evaluation parameters were (1) component position
(2) preoperative and postoperative coronal, sagittal, and rotational limb alignment
(3) preoperative bony deformity, including femoral torsion, condylar twist angle, and tibial torsion
and (4) preoperative and postoperative range of motion (ROM). Results: In multiple linear regression analysis using a stepwise procedure, postoperative rotational limb alignment was associated with the following: (1) rotation of the component position (tibia: β = 0.371, P &lt
.0001
femur: β = −0.327, P &lt
.0001), (2) preoperative rotational limb alignment (β = 0.253, P =.001), (3) postoperative flexion angle (β = 0.195, P =.007), and (4) tibial torsion (β = 0.193, P =.010). Conclusion: In addition to component positions, the intrinsic factors, such as preoperative rotational limb alignment, ROM, and tibial torsion, affected postoperative rotational limb alignment. On a premise of correct component positions, the intrinsic factors that can be controlled by surgeons should be taken care. In particular, ROM is necessary to be improved within the possible range to acquire better postoperative rotational limb alignment.

DOI： 10.1016/j.arth.2018.02.009

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<p>Herein, we consider the axisymmetric problem of a penny-shaped crack in an elastic material sandwiched between other materials. It is assumed that the central substance is composed of an elastic layer held between two semi-infinite bodies with different elastic constants, and that the crack is situated in the central plane of the elastic layer and subjected to uniform pressures on its internal surfaces. We consider two contact conditions; perfectly bonded and frictionless contact at the interfaces with the dissimilar materials. Dual integral equations are reduced to an infinite system of simultaneous equations by expressing normal displacements on the crack surfaces as an appropriate series function. Numerical results were obtained to examine the effects of the elastic constants of the layer and semi-infinite bodies and contact conditions on the stress intensity factor at the tip of the penny-shaped crack, the distribution of normal displacement, and stress on the crack plane. Based on the results of these numerical calculations, several conclusions can be made, as follows. 1) The distributions of normal displacement and stress at the crack plane and the stress intensity factor at the tip of the crack become larger than the results for an infinite solid when the ratio of the shear modulus of the layer to that of the semi-infinite bodies is larger than 1. 2) The numerical results for normal displacement and stress, and for stress intensity factors, in the frictionless case are higher than for the perfectly bonded case regardless of the shear modulus ratio and layer thickness ratio. The difference between the perfectly bonded and frictionless cases becomes greater as the layer thickness ratio becomes smaller. 3) There is a slight difference in the stress intensity factor values obtained from the present work and the corresponding results previously reported in the literature.</p>

DOI： 10.1299/mej.18-00125

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<p>Herein, we consider the axisymmetric problem of a penny-shaped crack in an elastic material sandwiched between other materials. It is assumed that the central substance is composed of an elastic layer held between two semi-infinite bodies with different elastic constants, and that the crack is situated in the central plane of the elastic layer and subjected to uniform pressures on its internal surfaces. Dual integral equations are reduced to an infinite system of simultaneous equations by expressing normal displacements on the crack surfaces as an appropriate series function. Numerical results were obtained to examine the effects of the elastic constants of the layer and semi-infinite bodies on the stress intensity factor at the tip of the penny-shaped crack, the distribution of normal displacement, and stress on the crack plane. As a result, there is a slight difference in the stress intensity factor values obtained from the present work and the corresponding results previously reported in the literature.</p>

DOI： 10.1299/jsmemecj.2018.G0300401

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<p>The indentation test has been widely used to evaluate mechanical properties of industrial and biological materials in many studies. In this study, we obtained an analytical solution of axisymmetric contact problem of viscoelastic layer bonded on rigid substrate indented by flat-ended cylindrical punch using elastic-viscoelastic corresponding principle. The relaxation indentation tests were conducted for silicon rubber, Echo PAD which is a soft material used for elastography, and articular cartilage of bovine femoral head. For articular cartilage, fresh articular cartilage was treated by collagenase after a relaxation indentation test and was then used again in same test. The viscoelastic models in this study were selected as three-element model (standard linear solid model) and five-element model (generalized Maxwell model) and viscoelastic parameters of the models were determined by fitting the analytical solution to applied load varying with time collected from the relaxation indentation test. As the results, it was suggested that the five-element model was more appropriate than three-element model to reproduce the behavior of relaxation indentation of silicon rubber, Echo PAD, and articular cartilage. Furthermore, the viscoelastic parameters of treated articular cartilage decreased sufficiently compared with those of fresh articular cartilage. From these results, it was suggested that the method of evaluating the time-dependent mechanical properties of articular cartilage based on the analytical solutions of the relaxation indentation test obtained from this study could be a useful tool for evaluating the state of degenerated cartilage.</p>

DOI： 10.1299/jsmemm.2018.OS0604

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Language：Japanese   Publisher：日本臨床バイオメカニクス学会  

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立位膝前後X線像から大腿骨と脛骨の相対的かつ経時的な回旋変化を評価するための指標を求める目的で、膝OA患者2例(男性1例、女性1例)のデータを用いて解析を行った。結果、標準化指標として「大腿骨内側顆における長軸の長さ」、大腿骨回旋指標として「内顆長軸から膝蓋骨外縁までの距離」、脛骨回旋指標として「脛骨内側顆間隆起先端から腓骨頭外側縁までの距離」を使用することで回旋位置変化を相対的に定量化できると考えられ、三次元CT骨モデルを用いたシミュレーションによってその妥当性が示された。

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER JAPAN KK  

Introduction: The relative torsional angle of the distal tibia is dependent on a deformity of the proximal tibia, and it is a commonly used torsional parameter to describe deformities of the tibia; however, this parameter cannot show the location and direction of the torsional deformity in the entire tibia. This study aimed to identify the detailed deformity in the entire tibia via a coordinate system based on the diaphysis of the tibia by comparing varus osteoarthritic knees to healthy knees.
Methods: In total, 61 limbs in 58 healthy subjects (age: 54 18 years) and 55 limbs in 50 varus osteoarthritis (OA) subjects (age: 72 7 years) were evaluated. The original coordinate system based on anatomic points only from the tibial diaphysis was established. The evaluation parameters were 1) the relative torsion in the distal tibia to the proximal tibia, 2) the proximal tibial torsion relative to the tibial diaphysis, and 3) the distal tibial torsion relative to the tibial diaphysis.
Results: The relative torsion in the distal tibia to the proximal tibia showed external torsion in both groups, while the external torsion was lower in the OA group than in the healthy group (p &lt; 0.0001). The proximal tibial torsion relative to the tibial diaphysis had a higher external torsion in the OA group (p = 0.012), and the distal tibial torsion relative to the tibial diaphysis had a higher internal torsion in the OA group (p = 0.004) in comparison to the healthy group.
Conclusion: The reverse torsional deformity, showing a higher external torsion in the proximal tibia and a higher internal torsion in the distal tibia, occurred independently in the OA group in comparison to the healthy group. Clinically, this finding may prove to be a pathogenic factor in varus osteoarthritic knees. Level of evidence: Level Ill. (C) 2017 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jos.2017.01.002

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To characterize femoral deformities and determine sex differences in varus knee osteoarthritis (OA), femoral morphology and limb alignment were evaluated by using three-dimensional (3D) assessment, comparing healthy, elderly volunteers with osteoarthritic knees.
A total of 178 lower limbs of 169 subjects with knee osteoarthritis (136 women, 33 men; mean age 74.9 +/- 5.2 years) and 80 lower limbs of 45 healthy, elderly subjects (24 women, 21 men; mean age 65 +/- 4.9 years) were examined. A 3D extremity alignment assessment system was used to examine the subjects under weight-bearing conditions on biplanar long-leg radiographs using a 3D-to-2D image registration technique. The evaluation parameters were (1) femoral bowing in the coronal plane, (2) femoral bowing in the sagittal plane, (3) femoral neck anteversion, (4) hip-knee-ankle angle, and (5) femoral torsion.
Higher femoral lateral bowing and slightly higher femoral internal torsion in the proximal diaphysis were observed in women with OA compared with healthy subjects. No difference in the higher varus malalignment, no alteration in the femoral anterior bowing, and no difference in the lower femoral neck anteversion were found between men and women when comparing healthy and OA subjects.
The higher femoral lateral bowing and slightly higher femoral internal torsion in the proximal diaphysis in women are possibly a structural adaptation to mechanical use. The clinical significance is that the femoral deformities and the sex differences in knee OA have the potential to improve the understanding of the aetiology of primary varus knee OA.
IV.

DOI： 10.1007/s00167-016-4166-2

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膝関節は可動域が広い関節で、成長軟骨板(GP)にも圧縮力や剪断力が加わるため、GP障害の治療では、荷重環境とGP形態との関連性の把握が重要である。しかし、両者の関連性に関する報告は見られないことから、膝関節の治療目的で通院中の男性6名(年齢10.8±1.3歳)6膝を対象に、MRI撮影および2方向からのコンピューターX線撮影(CR)を行い、GPの三次元形態と荷重環境との関連について定量的に検討した。MRIでは膝関節を撮像し、CRでは三次元アライメント評価法にしたがって下肢全体を撮影した。次に、GPにおける下肢荷重線の通過位置を求め、GPの規格化および補間、GP形態の分析を行った。その結果、正常な下肢アライメントの場合、冠状面ではGPの顆間部に最も荷重がかかり、この部分のGPは平坦度が高く、わずかに前傾しており、これにより、荷重応力の集中を低減し、剪断力を低くしていると推定された。

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Background: Anterior cruciate ligament (ACL) injury often leads to symptoms of instability, which may cause meniscus injury, osteochondral lesions, and degenerative changes. For thorough evaluation of the effects of abnormal motion of ACL-deficient (ACLD) knees on the meniscus and articular cartilage, it is necessary to assess tibiofemoral motion in the medial and lateral compartments separately. Our aim was to determine if in vivo three-dimensional (3D) dynamic motion of ACLD knees differs from that of contra lateral uninjured knees by assessing knee motion in the medial and lateral compartments respectively.
Methods: A total of 22 patients with an isolated ACL-injured knee were examined. 3D to two-dimensional registration was used to determine 3D knee motion during squatting from full knee extension to full flexion for both ACLD and contralateral uninjured knees. The knee motion was evaluated by the movement of the geometric center axis of the femur projected onto the tibial axial plane.
Results: In ACLD knees the lateral femoral condyle was located significantly more posteriorly during nearly full extension than in contralateral uninjured knees. The range of anteroposterior translation of the medial femoral condyle was significantly greater than those of contralateral uninjured knees. Almost all of the contralateral uninjured knees demonstrated medial pivot motion, while the ACLD knees showed higher variance.
Conclusions: The ACLD knees exhibited a motion pattern different from those of contralateral uninjured knees with higher variance. During nearly full extension of the ACLD knees, the lateral femoral condyle translated posteriorly and the screw-home movement seemed to be impaired. The ACL might have an important role in maintaining normal knee function, especially during the early flexion phase. The larger range of anteroposterior translation of the medial femoral condyle in ACLD knees may be associated with a risk of secondary meniscal injury and degenerative change in the articular cartilage. Level of evidence: Level IV. (C) 2015 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jos.2015.11.001

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In the clinical, it is difficult to carry out the motion analysis because it requires a large place. The purpose of this study is to examine the gait analysis method by one direction frontal video that can be easily measured in clinical. The subjects were five healthy persons attached four markers at both shoulders and both anterior superior iliac spine (ASIS). The walking motion of each subject toward a camera was analyzed. Body trunk tilt and centroid sway of the upper body part were calculated and compared with the results of three-dimensional gait analysis methods. The result showed the same tendency of the body trunk tilt and the centroid sway changes based on each method. The result suggested that the gait analysis by one direction frontal video could evaluate the large abnormal gait. Further, authors evaluated OA knee joint thrust using one direction frontal video. The change of the knee joint alignment and the distance between the loading axis of lower extremity and knee joint center were calculated as knee joint thrust. Results showed that knee adduction angle and distance of knee joint center from lower limb loading axis of OA patient were increased. The result suggested that this method could evaluate the knee joint thrust of OA patient.

DOI： 10.11395/jjsem.16.116

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The posterior cruciate ligament (PCL) functions as the primary restraint to posterior tibial movement and the stabilizer for axial rotation of the knee joint. It is, therefore, important to know the mechanical characteristics of the PCL. The objective of this study was to evaluate the in vivo characteristics of the three-dimensional (3D) deformation and orientation of the PCL during knee flexion using magnetic resonance imaging (MRI). Ten normal knees were visualized using MRI at full extension (FE), 10°, 20°, 30° and 60° of static knee flexion. The length, strain, elevation and deviation of the PCL were measured using the 3D models of the femur, tibia and PCL reconstructed from the MR images. The PCL length was measured in three portions (Medial: M, Central: C, Lateral: L) to consider its 3D shape. Tendencies of the PCL elongation and strain during knee flexion were different among these 3 portions. The PCL length in M portion was shortest in 10° or 20° and extended in FE and 60°. The PCL length in L portion, on the other hand, extended from FE to 60°. These 3D deformation characteristics were consisted with the changes in the elevation and deviation of the PCL during knee flexion.

DOI： 10.11395/jjsem.16.127

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The purpose of this study was to develop a method for evaluation of the three-dimensional (3D) alignment and position of the artificial knee joint using a biplanar slot radiography (SR) system and 3D models. A SR system uses collimated fan beam x-rays synchronized with the movement of a flat-panel detector. This system allows to obtain a full length x-ray image of the body with reduced dose and smaller image distortion compared with conventional x-ray systems. The biplanar SR system used a rotation table positioned at 0 deg and 60 deg relative to the optical axis of an X-ray source. Camera calibration was performed using an acrylic frame with 72 radiopaque markers. The femoral and tibial components of a total knee replacement system were immobilized and imaged using the biplanar SR system. Then, the femoral component was installed on a sawbone femur and imaged again. The 3D positions of the components and femur were recovered using an interactive 2D to 3D image registration method. Overall, the largest estimation errors were within 1 mm in translation and 1 deg in rotation, demonstrating that this method has an adequate accuracy for the clinical usage.

DOI： 10.11395/jjsem.16.134

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The action of the forearm is to transfer force and torque across the elbow and wrist, resulting in axial rotation at the distal and proximal radioulnar joints, called pronation and supination. Pronation and supination are important functions as they allow many kinds of activities of daily living. Three-dimensional (3D) motion analysis of pronation and supination is essential for a better understating of the biomechanics of the forearm to describe the physiological range of motion and optimize clinical options for disorders of the forearm. Although numerous in vitro studies have contributed to gain insights into the forearm pronation and supination, in vivo investigations are still limited. In this study, three-dimensional (3D) motion of the distal radioulnar joint (DRUJ) during forearm pronation and supination was analyzed in vivo using biplanar radiography and 3D models of the ulna and radius. Twelve healthy subjects (6 men and 6 women) were recruited for the study. Each subject's right forearm (dominant hand) underwent a computed tomography (CT) scan to create 3D surface models of the ulna and radius. Each subject was imaged using a calibrated biplanar radiographic system at 90° pronation, 45° pronation, neutral, 45° supination, and 90° supination while the elbow was in extension or flexion. The 3D positions of the radius and ulna were obtained using a 2D-to-3D image registration method. The relative translations of the radius in the radioulnar, dorsopalmar, and proximodistal directions and the relative rotations of the radius about the radioulnar, dorsopalmar, and proximodistal axes were evaluated with respect to the ulna during pronation and supination. In general, the radius translated towards the ulnar side throughout forearm rotation, and moved towards the palmar side as pronation increased and moved dorsally as supination increased, and was positioned proximally during pronation and distally during supination. The rotation of the radius was dominant about the proximodistal axis. These kinematic variables were affected by elbow position and sex of the subject. The current findings regarding the 3D kinematics of the DRUJ during forearm pronation and supination may contribute to further understanding of the physiological biomechanics of the upper limb.

DOI： 10.1299/jbse.15-00364

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

The purpose of this study was to investigate the hypothesis that a medial unicompartmental knee arthroplasty might restore the functional flexion axis of a knee to normal. The flexion axis can be indirectly identified by tracking the vertical translation of anatomic landmarks that basically move around the flexion axis during a knee motion. If a unicompartmental knee could help restore the normal flexion axis, the anatomic landmarks after the arthroplasty would show the vertical translation similar to those of normal knees during a knee flexion.
While performing a squatting motion, the kinematics of 17 knees were determined before and after a medial unicompartmental arthroplasty to calculate the vertical translation of a clinical epicondylar axis, using a three- to two-dimensional registration technique through a single-plane fluoroscopic system incorporating a biplanar static radiography. The results were compared with a normal data, and a statistical analysis including a two-way repeated-measured analysis of variance was performed.
For the medial end, from 10A degrees to 100A degrees knee flexion, normal, osteoarthritic, and unicompartmental knees had the average superior vertical translation of 7.3 +/- A 4.2, 4.3 +/- A 7.2, and 2.4 +/- A 3.1 mm, respectively, with statistical significance between normal and unicompartmental knees (p &lt; 0.001). The vertical translation did not return to normal post-implantation.
A unicompartmental knee could not reproduce the normal flexion axis. As for clinical relevance, the changes of the implant design and surgical procedure may be necessary to obtain the normal flexion axis reproducing a normal motion.
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DOI： 10.1007/s00167-014-3296-7

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Language：Japanese   Publisher：日本臨床バイオメカニクス学会  

車いすハンドル高さと降坂移送をする介助者の上肢負担について検討した。身長の異なる健常者5例を対象とした。坂前進下りにおいて、介助者はハンドルを引きながら車いすの前進下りをし、上肢の負荷が少ないハンドル高さは関節モーメントの最小値から肘関節の最大モーメントが0となるハンドル高さ割合80%付近であると考えられた。坂後進下りにおいて、介助者はハンドルを押しながら車いすの後進下りをし、上肢の負荷が少ないハンドル高さは関節モーメントの最小値からハンドル高さ割合90%前後であると考えられた。ハンドル高さ割合90%とは、100%で移送者の肩高さに相当することから、移送者の胸よりも少し高い位置に相当した。坂路降坂における介助者の上肢負担は移送方法により大きく異なることが判明し、適切なハンドル高さも異なっていた。

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Other Link： http://search.jamas.or.jp/link/ui/2016096444

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We recently developed a new method for three-dimensional evaluation of mechanical factors affecting knee joint in order to help identify factors that contribute to the progression of knee osteoarthritis (KOA). This study aimed to verify the clinical validity of our method by evaluating knee joint dynamics during gait. Subjects were 41 individuals (14 normal knees; 8 mild KOAs; 19 severe KOAs). The positions of skin markers attached to the body were captured during gait, and bi-planar X-ray images of the lower extremities were obtained in standing position. The positional relationship between the markers and femorotibial bones was determined from the X-ray images. Combining this relationship with gait capture allowed for the estimation of relative movement between femorotibial bones. We also calculated the point of intersection of loading axis of knee on the tibial proximal surface (LAK point) to analyze knee joint dynamics. Knee flexion range in subjects with severe KOA during gait was significantly smaller than that in those with normal knees (p = 0.011), and knee adduction in those with severe KOA was significantly larger than in those with mild KOA (p &lt; 0.000). LAK point was locally loaded on the medial compartment of the tibial surface as KOA progressed, with LAK point of subjects with severe KOA rapidly shifting medially during loading response. Local loading and medial shear force were applied to the tibial surface during stance phase as medial KOA progressed. Our findings suggest that our method is useful for the quantitative evaluation of mechanical factors that affect KOA progression. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.gaitpost.2015.04.018

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DOI： 10.11395/jjsem.14.s291

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It is common to assert that restoration of normal knee kinematics is essential for the best functional result after knee arthroplasty. Previous studies using the progression of the geometric centre axis have suggested that kinematics after unicompartmental arthroplasty is markedly different from the normal. For this study, the transepicondylar axis was used because this axis is closer to the flexion axis and should be a better reference for motion. The following hypothesis was tested: the transepicondylar axis would again show that the postoperative kinematics does not restore normal motion and is closer to that before replacement.
Seventeen osteoarthritic knees were tested before and after unicompartmental arthroplasty using a three-dimensional to two-dimensional registration technique tracking the transepicondylar axis to calculate translation and rotation of this axis. Results were compared for the seventeen knees before and after arthroplasty and were compared to the normal knee as measured in our previous study.
Similar motion patterns in the pre- and postoperative knees were shown but both the pre- and postoperative motion were markedly different from the normal knee.
This result supported our hypothesis. The clinical relevance is that medial unicompartmental arthroplasty cannot restore the motion of the knee to normal in the living knee. Therefore, it would be expected that the patient for unicompartmental knee might not feel normal. It may not be possible depending on ligaments alone to restore the knee to normal, and the changes in the articular shapes and the surgical procedure may also be necessary.
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DOI： 10.1007/s00167-013-2767-6

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The functional flexion axis (FFA) is the principal axis around which the knee moves and thus, by definition, does not move in vertical displacement relative to the tibia. The transepicondylar axis (TEA) has been reported to coincide with the FFA. If that is not true, the TEA should show vertical displacement during motion, and this hypothesis was investigated.
Three-dimensional knee kinematics of 20 healthy volunteers were determined during a squatting motion via a 3-dimensional to 2-dimensional image registration technique by calculating the vertical displacement of the clinical epicondylar axis (CEA) through the full range of motion.
From 0A degrees to 90A degrees knee flexion, the average vertical displacement of the lateral end of the CEA was &lt; 3 mm, whereas that of the medial end was large (7.6 mm).
The large vertical displacement of the medial end of the CEA suggests that the CEA is not the FFA. This finding implies that the CEA may not be an appropriate axis for a TKA prosthesis having a "single radius" design.
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DOI： 10.1007/s00776-014-0536-0

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DOI： 10.1016/j.jbiomech.2013.12.013

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

The range of motion (ROM) resulting from total hip arthroplasty (THA) depends on the relative orientation of the femoral and acetabular components, and malpositioning of components is a possible cause of several complications. The purpose of this study was to validate a 3-dimensional (3D) lower extremity alignment assessment system (3D LAAS) for the measurement of alignment of natural and implanted hip joints and implant position with respect to the target bone with the subject in a standing position. Sawbone femur and pelvis and femoral and acetabular components of a total hip arthroplasty system were used. Three spherical markers were attached to each sawbone and each component to define the local coordinate system. Outlines of the 3D bone models and component computer-aided design models were projected onto extracted contours of the femur, pelvis, and implants in calibrated frontal and oblique X-ray images. The 3D position of each model was recovered by minimizing the differences between projected outlines and contours. Mean absolute errors were less than 1.27 ± 0.79 mm and 0.99 ± 0.52° for femur and pelvis, 1.64 ± 0.66 mm and 1.54 ± 0.39° for femoral and acetabular components, 1.58 ± 0.29 mm and 1.75 ± 0.69° for femur and femoral component, and 1.51 ± 0.49 mm and 1.24 ± 0.14° for pelvis and acetabular component, indicating that the 3D LAAS is applicable to measure the alignment of natural and implanted hip joints and implant position after THA.

DOI： 10.1299/jbse.13-00162

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The transepicondylar axis (TEA) has been used as a flexion axis of the knee and a reference of the rotational alignment of the femoral component. However, no study has showed dynamic normal knee kinematics employing TEA as the evaluation parameter throughout the full range of motion in vivo. The purpose of this study was to analyze dynamic kinematics of the normal knee through the full range of motion via the 3-dimensional to 2-dimensional registration technique employing TEA as the evaluation parameter.
Dynamic motion of the right knee was analyzed in 20 healthy volunteers (10 female, 10 male; mean age 37.2 years). Knee motion was observed as subjects squatted from standing with knee fully extended to maximum flexion. The following parameters were determined: (1) Anteroposterior translations of the medial and lateral ends of the TEA; and (2) changes in the angle of the TEA on the tibial axial plane (rotation angle).
The medial end of the TEA demonstrated anterior translation (3.6 +/- A 3.0 mm) from full extension to 30A degrees flexion and demonstrated posterior translation (18.1 +/- A 3.7 mm) after 30A degrees, while the lateral end of the TEA demonstrated consistent posterior translation (31.1 +/- A 7.3 mm) throughout knee flexion. All subjects exhibited femoral external rotation (16.9 +/- A 6.2A degrees) relative to the tibia throughout knee flexion.
Compared to previously used parameters, the TEA showed bicondylar posterior translation from early flexion phase. These results provide control data for dynamic kinematic analyses of pathologic knees in the future and will be useful in the design of total knee prostheses.

DOI： 10.1007/s00167-012-2010-x

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While various factors have been assumed to affect knee joint biomechanics, few data have been reported on the function of the extensor mechanism in deep flexion of the knee. This study analyzed the patellofemoral joint contact kinematics and the ratio of the quadriceps and patellar tendon forces in living subjects when they performed a single leg lunge up to 150 deg of flexion. The data revealed that in the proximal-distal direction, the patellofemoral articular contact points were in the central one-third of the patellar cartilage. Beyond 90 deg of flexion, the contact points moved towards the medial-lateral edges of the patellar surface. At low flexion angles, the patellar tendon and quadriceps force ratio was approximately 1.0 but reduced to about 0.7 after 60 deg of knee flexion, implying that the patella tendon carries lower loads than the quadriceps. These data may be valuable for improvement of contemporary surgical treatments of diseased knees that are aimed to achieve deep knee flexion.

DOI： 10.1115/1.4024284

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Language：Japanese   Publisher：(一社)日本関節鏡・膝・スポーツ整形外科学会  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

This study quantified in-vivo 3D patellar tendon kinematics during weight-bearing deep knee bend beyond 150 degrees. Each knee was MRI scanned to create 3D bony models of the patella, tibia, femur, and the attachment sites of the patellar tendon on the distal patella and the tibial tubercle. Each attachment site was divided into lateral, central, and medial thirds. The subjects were then imaged using a dual fluoroscopic image system while performing a deep knee bend. The knee positions were determined using the bony models and the fluoroscopic images. The patellar tendon kinematics was analyzed using the relative positions of its patellar and tibial attachment sites. The relative elongations of all three portions of the patellar tendon increased similarly up to 60 degrees Beyond 60 degrees, the relative elongation of the medial portion of the patellar tendon decreased as the knee flexed from 60 degrees to 150 degrees while those of the lateral and central portions showed continuous increases from 120 degrees to 150 degrees. At 150 degrees, the relative elongation of the medial portion was significantly lower than that of the central portion. In four of seven knees, the patellar tendon impinged on the tibial bony surface at 120 degrees and 150 degrees of knee flexion. These data may provide useful insight into the intrinsic patellar tendon biomechanics during a weight-bearing deep knee bend and could provide biomechanical guidelines for future development of total knee arthroplasties that are intended to restore normal knee function. (c) 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:15961603, 2012

DOI： 10.1002/jor.22126

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人工膝単顆置換術を施行した内側型変形性膝関節症9例11膝(男3膝、女9膝、平均75.3歳)を対象に、術前後の下肢アライメント変化と置換側コンパートメントJoint line変化との関係について検討した。下肢アライメント変化は、三次元下肢アライメント測定システムを使用し、術前のCTから三次元モデルを構築して座標軸を設定後、下肢全長立位2方向CR像に三次元骨形成モデルを重ね合わせて評価した。大腿骨および脛骨のmechanical axisのなす角であるHip Knee Ankle angle(HKA)は、術前平均188.1°が術後184.2°に、荷重軸%通過位置は内側66.3%が35.5%に変化し、アライメントは術後有意に外反化していた。置換側コンパートメントの脛骨joint line変化量は、平均2.1mm、最大6.4mm上昇していた。術前後のHKA変化量および荷重軸%通過位置の変化量と、脛骨joint line変化量とは有意な相関が認められた。

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Analysis of the movement of anatomically defined reference axes at the femoral condyles relative to the tibia is appropriate for evaluating knee kinematics. However, such parameters have been previously employed only in studies utilizing stop-motion techniques. The purpose of this study was to evaluate in vivo dynamic kinematics for full range of motion in normal knees using the three-dimensional to two-dimensional registration technique and to compare them with previously reported normal knee kinematics obtained via stop-motion techniques.
Dynamic motion of the right knee was analyzed in 20 healthy volunteers (10 female, 10 male; mean age 37.2 years). Knee motion was observed when subjects squatted from standing with the knee fully extended to maximum flexion. We determined the following parameters: (1) changes to angles of the geometric center axis (GCA) on the tibial axial plane (rotation angle); (2) anteroposterior translations of the medial and lateral ends of the GCA; and (3) motion patterns in each phase during knee flexion.
All subjects exhibited femoral external rotation (26.1A degrees) relative to the tibia throughout knee flexion. The medial femoral condyle demonstrated anterior translation (5.5 mm) from full extension to 100A degrees flexion, and demonstrated posterior translation (3.9 mm) after 100A degrees, while the lateral femoral condyle demonstrated consistent posterior translation (15.6 mm) throughout knee flexion. All subjects showed medial pivot motion from full extension to nearly 120A degrees flexion. From 120A degrees flexion, bicondylar rollback motion was observed.
Although the behavior of the medial femoral condyle in our analysis differed somewhat from that seen in previous cadaver studies, the results obtained using dynamic analysis were generally equivalent to those obtained in previous studies employing stop-motion techniques. These results provide control data for future dynamic kinematic analyses of pathological knees.

DOI： 10.1007/s00776-011-0149-9

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japanese Society for Experimental Mechanics  

This paper deals with the applicability of the near infrared (NIR) spectroscopy to quantitative measurement of the water content in human articular cartilage using gelatin model. We developed the device using NIR light at a wave length of 970nm, and investigated whether or not the device was useful for the measurement of the water content in articular cartilage. The gelatin was used as materials for the specimens with single, two- and three-layers. The absorbance defined as the intensity ratio between emitting and receiving NIR lights, the variation of receiving light intensity with the water content, and that with the distance between two probes of the light source and sensor were measured. The absorbance increased with increasing water content and with increasing probe distance (R<SUP>2</SUP>=0.86&sim;0.91). In the layered specimens, the light was supposed to pass through the surface layer and then reach the adjacent layer. These results showed that the device was useful for the measurement of the water content in the single and layered specimens. This study suggested that the device developed in this study have some possibilities of acquiring the quantitative data of water content at any point from the surface of articular cartilage.

DOI： 10.11395/jjsem.11.s239

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Other Link： http://hdl.handle.net/10191/26369

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DOI： 10.1115/SBC2011-53521

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従来の方法で人工膝関節全置換術(TKA)を施行した大腿骨における、大腿骨上顆軸(TEA)からみた三次元的な関節表面までの距離とインプラントの三次元的設置角度を評価し、Single radius型のインプラント設置法を再検討した。TKAを施行した40例40膝を対象とした。TKA後、下肢全長2方向CR像に骨とインプラントの三次元形状モデルを重ね合わせ、実際の設置状態を正確に再現した骨-インプラントの三次元モデル複合体を生成した。術後の大腿骨インプラント内外側穎部最遠位点からTEAまでの距離(遠位径)と同最後方点からのTEAまでの距離(後方径)と、インプラント三次元設置角度を評価した。内側においては遠位径-後方径間に有意差は認めなかったが、外側においては後方径が遠位径に比して有意に短かった。内外反・屈曲伸展は概ね良好であったが、回旋角度がTEAに対して内旋傾向であった。

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japanese Society for Experimental Mechanics  

Estimation of the artificial hip joint contact area and pressure distribution during motions of daily life is important in predicting joint degeneration mechanism and implant wear. The purpose of this study was to develop a method of applying discrete element analysis (DEA) based on a rigid body spring model to artificial hip joint, and to analyze contact area and pressure distribution during different motions. Post-operative motion analyses of four basic motions, such as fast walking, slow walking, standing up and sitting down were performed by using VICON system and Kistler force plate. Implant orientation was obtained by matching the contours of 3D bone model and implant CAD model to those of the biplanar CR images. Triangular mesh at interior surface of cup model was considered as liner surface and used for applying DEA to artificial hip joint.Because stem model was considered to be a rigid body and consequential transformations occurred only inside the liner model, triangular mesh was considered to be a compressive spring respectively.The change of contact area and the pressure distribution under dynamic condition were calculated easily through these considerations, and rapid increase accompanied with change of area was observed in knee bending motions.

DOI： 10.11395/jjsem.10.s251

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DOI： 10.11395/jjsem.10.s234

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japanese Society for Experimental Mechanics  

Currently, stem insertion during total hip arthroplasty (THA) is not well controlled. The present study investigated a method for improving stem setting in accordance with preoperative planning using a three-dimensional (3-D) computed tomography (CT) model of the femur and RGB images of the excised femoral head. We utilized three femoral heads removed during THA and modeled each head using three spherical acrylic markers. Each femoral head was osteotomized using a parallel jig and three rectangular images of the osteotomized head were taken using a CCD camera. Each femoral head was then set on a camera base and RGB images were taken from three orthogonal directions using the CCD camera. The B-images of the femoral head and the 3-D bone model were processed through image-matching software using an automatic outline extraction and downhill simplex method. The position of the contralateral side of the jig, related to the femur, was measured using a 3-D measuring system in order to validate the accuracy of the image-matching. However, since validation of the accuracy of the image-matching is difficult once the femoral head is excised, a six-degree-of-freedom board was used to facilitate the accuracy validation.

DOI： 10.11395/jjsem.10.s247

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japanese Society for Experimental Mechanics  

The wrist joint is condyloid and capable of movement through two axes: palmar/dorsal flexion and radial/ulnar deviation. Knowledge of <i>in vivo</i> joint mechanics is important for understanding pathological mechanisms and the treatment of various joint problems. The purpose of this study was to investigate the <i>in vivo</i> wrist joint mechanism during wrist motion. <i>In vivo</i> wrist joint contact and the kinematics of the scaphoid and lunate during palmar/dorsal flexion and radial/ulnar deviation were examined using magnetic resonance imaging (MRI). The wrist joints of 15 healthy young volunteers were scanned at 8 positions (.30 deg of palmar flexion; neutral; 30, 60, and 90 deg of dorsal flexion; .20 deg of radial deviation; neutral; and 20 deg of ulnar deviation). Contact of the wrist joint was estimated quantitatively from the derived MR images. Using three-dimensional surface models of the carpal bones, the kinematics of the scaphoid and lunate were analyzed three-dimensionally.

DOI： 10.11395/jjsem.10.s261

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Although assessment of lower extremity alignment is important for the treatment and evaluation of diseases that present with malalignment of the lower extremity, it has generally been performed using only plain radiographs seen in two dimensions (2D). In addition, there is no consensus regarding the criteria for quantitative three-dimensional (3D) evaluation of the relative angle between the femur and tibia. The purpose of this study was to establish assessment methods and criteria for quantitatively evaluating lower extremity alignment in 3D and to obtain reference data from normal elderly subjects.
The normal alignment of 82 limbs of 45 healthy elderly subjects (24 women, 21 men; mean age 65 years, range 60-81 years) was analyzed in 3D with regard to flexion, adduction-abduction, and rotational angle of the knee in the weight-bearing, standing position. The obtained computed tomography (CT) and biplanar computed radiography (CR) data were used to define several anatomical axes of the femur and tibia as references.
In the sagittal plane, the mean extension-flexion angle was significantly more recurvatum in women than in men. In the coronal plane, the mean 3D hip-knee-ankle angle was more varus by several degrees in this Japanese series than that in a Caucasian series reported previously. Regarding rotational alignment, the mean angle between the anteroposterior axis of the tibia and the transepicondylar axis of the femur in this series was slightly larger (externally rotated) than that of previously reported Japanese series examined in the supine position.
These data are believed to represent important references for 3D evaluation of morbid lower extremity alignment in the weight-bearing, standing position and are important for biomechanical research (e.g., 3D analyses of knee kinematics) because the relative angles between the femur and tibia are assessed three-dimensionally.

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An automated image-matching technique is presented to assess alignment of the entire lower extremity for normal and implanted knees and the positioning of implants with respect to bone. Sawbone femur and tibia and femoral and tibial components of a total knee arthroplasty system were used. Three spherical markers were attached to each sawbone and each component to define the local coordinate system. Outlines of the three-dimensional (3D) bone models and component computer-aided design (CAD) models were projected onto extracted contours of the femur, tibia, and implants in frontal and oblique X-ray images. Three-dimensional position of each model was recovered by minimizing the difference between the projected outline and the contour. Median values of the absolute error in estimating relative positions were within 0.5 mm and 0.6 degrees for the femur with respect to the tibia, 0.5 mm and 0.5 degrees for the femoral component with respect to the tibial component, 0.6 mm and 0.6 degrees for the femoral component with respect to the femur, and 0.5 mm and 0.4 degrees for the tibial component with respect to the tibia, indicating significant improvements when compared to manually obtained results. (C) 2009 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jbiomech.2009.08.022

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Language：Japanese   Publisher：Japanese Society of Radiological Technology  

Elevated contact stress on the articular joints has been hypothesized to contribute to articular cartilage wear and joint pain. However, given the limitations of using contact stress and areas from human cadaver specimens to estimate articular joint stress, there is need for an &lt;i&gt;in vivo&lt;/i&gt; method to obtain such data. Magnetic resonance imaging (MRI) has been shown to be a valid method of quantifying the human joint contact area, indicating the potential for &lt;i&gt;in vivo&lt;/i&gt; assessment. The purpose of this study was to describe a method of quantifying the tibiofemoral joint contact area using MRI. The validity of this technique was established in porcine cadaver specimens by comparing the contact area obtained from MRI with the contact area obtained using pressure-sensitive film (PSF). In particular, we assessed the actual condition of contact by using the ratio of signal intensity of MR images of cartilage surfaces. Two fresh porcine cadaver knees were used. A custom loading apparatus was designed to apply a compressive load to the tibiofemoral joint. We measured the contact area by using MRI and PSF methods. When the ratio of signal intensity of the cartilage surface was 0.9, the error of the contact area between the MR image and PSF was about 6%. These results suggest that this MRI method may be a valuable tool in quantifying joint contact area&lt;i&gt; in vivo&lt;/i&gt;.

DOI： 10.6009/jjrt.65.1407

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DOI： 10.11395/jjsem.9.s167

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DOI： 10.11395/jjsem.9.s162

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japanese Society for Experimental Mechanics  

Dynamic nanoindentation was used to determine microstructural viscoelastic properties of single osteons and interstitial lamellae of rat cortical bone tissue. The effects of mineral, organic and water contents on macrostructural viscoelastic properties were also investigated. Compared to interstitial lamellae, the storage moduli of osteons were significantly lower; however, loss tangents were higher. The storage modulus and mineral content were correlated, and the loss tangent and the organic and water contents were linearly correlated.

DOI： 10.11395/jjsem.9.s151

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The purpose of the present study is to develop a direct and accurate method for measuring knee kinematics by using single-plane fluoroscopy. The study was carried out on a human cadaver femur. Computed tomography (CT) scan data of the femur was taken in order to construct 3D bone volume model of the femur. The femur was placed on an acrylic holder that was attached to a micromanipulator. The femur was rotated about in each orthogonal axis of the micromanipulator over a range of ±2° in 1° increments and then translated along each orthogonal axis over a range of ±2 mm in 1-mm increments. The 3-dimensional (3D) position of the femur (in other words, the 6 degree-of-freedom (DOF) parameters) was recovered by matching the digitally reconstructed radiographs (DRRs) generated from the 3D volume model of the femur and single-plane fluoroscopic images taken from the 25 positions generated by using the micromanipulator. The root-mean-square error (RMSE) of the overall rotation parameters was within 1.4°. For the translation parameters RMSE took its maximal value of 7.8 mm in the out-of-plane direction. This indicates that the present method has potential for clinical application. Copyright © 2009 by The Japan Society of Mechanical Engineers.

DOI： 10.1299/jbse.4.192

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DOI： 10.11395/jjsem.8.121

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DOI： 10.11396/jjsndi.57.89

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The effects of low-gamma irradiation on the impact compressive properties of ultra high molecular weight polyethylene (UHMWPE) were investigated. Gamma irradiation was performed at 30kGy in nitrogen or at 29kGy in air without post-irradiation treatment. Impact compressive tests using the split-Hopkinson pressure-bar (SHPB) technique were performed to measure stress&amp;ndash;strain relations up to a true strain of 8% at a strain rate of 260s&lt;SUP&gt;-1&lt;/SUP&gt;. Gamma irradiation in air significantly increased the Young&#039;s modulus and the 0.5% yield stress, and gamma irradiation in N&lt;SUB&gt;2&lt;/SUB&gt; significantly increased the 0.5% yield stress, as determined by impact compressive testing. The impact stress-strain behaviors of both unirradiated and gamma irradiated UHMWPE specimens were compared by the elasto-viscoplastic model proposed by Bergstr&amp;ouml;m [Biomaterials Vol.23 p.2329 (2002)]. We found that the elasto-viscoplastic model had a potential to predict the observed impact stress-strain responses.

DOI： 10.2472/jsms.57.882

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DOI： 10.11345/nctam.56.15

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DOI： 10.11345/nctam.55.61

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This study analyzed tibio-femoral joint kinematics and contact area during knee flexion at 0ｰ, 30ｰ, 60ｰ, 90ｰ and 135ｰ using magnetic resonance imaging with a 3D-fat-suppressed fast low angle shot sequence (3D-FLASH). At a 200N loading situation, knee flexion angles were chosen to be 0ｰ, 30ｰand 60ｰ. Sagittal and coronal images were obtained under the loading and unloading situations from 6 healthy male Japanese volunteers. At unloading situation, from 0ｰ to 90ｰ the centroids of the medial and lateral contact areas translated backward and outside. From 90ｰ to 135ｰ the centroids of the medial and lateral contact areas translated backward and inside. The contact areas tended to decrease, but from 60ｰ to 135ｰ knee flexion the medial contact area was not changed generally. At loading situation, almost the same results as observed at unloading situation for each translation were obtained. However, the translation of centroids of the medial and lateral contact areas decreased with an increase of knee flexion, and the centroids moved roughly straight backward as well. The contact areas increased at each knee flexion angle as compared to unloading situation. These results showed good correlation with previous ones found in the other studies of knee kinematics.

DOI： 10.11395/jjsem.6.31

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This study analyzed tibio-femoral(TF) joint kinematics and contact area(CA) during knee flexion at 0 degrees, 30 degrees, 60 degrees, 90 degrees and 135 degrees using MRI. At a 200N loading situation, knee flexion angles were chosen to be 0 degrees, 30 degrees and 60 degrees. At unloading situation, from 0 to 90 the centroids of the medial and lateral CAs were translated backward and outside. From 90 degrees to 135 degrees, the centroids of both CAs translated backward and inside. The CAs tended to decrease, but from 60 degrees to 135 degrees knee flexion the medial CA was not changed generally. At loading situation, almost the same results as observed at unloading situation for each translation were obtained. However, the translation of the centroids of both CAs decreased with an increase of knee flexion. The CAs increased at each knee flexion angle as compared to unloading situation.

DOI： 10.11395/jjsem.6.31

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DOI： 10.11345/nctam.54.3

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DOI： 10.11395/jjsem.5.40

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The mechanical properties of cortical bone are a consequence of the interaction between the mineral and collagen components. Small variations in the amount of mineral present in a section of bone can have a large influence on its mechanical properties. Studies have shown the correlations between Vickers microhardness and mineral content, and Vickers microhardness and elastic modulus using three-point and four-point bending tests. However, the precise nature of statistical relationship has yet to be established. Nanoindentation, which evolved from Vickers microhardness test, allows for measurement of mechanical properties of cortical bone at the nanometer scale. The nanoindentation technique has been applied to estimate mechanical properties of bone at a microscopic length scale, overcoming the limitations of traditional mechanical tests for small specimens. In this study, the relationships between mechanical properties measured by nanoindentation and volumetric Bone Mineral Density (vBMD) measured by peripheral Quantitative Computed Tomography (pQCT) in femoral cortical bone from a variety of ages of rats were investigated. The specimen of rat cortical bone used here was Haversian bone. Experimentally measured elastic modulus was correlated with vBMD (r=0.80). It was found that a good correlation also existed between hardness and vBMD (r=0.81).

DOI： 10.11395/jjsem.5.40

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DOI： 10.11345/nctam.53.27

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DOI： 10.11395/jjsem2001.3.225

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DOI： 10.11395/jjsem2001.2.117

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DOI： 10.11345/nctam.50.91

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Dynamic compressive behaviour of bovine trabecular bone was investigated. Compression tests on cylindrical specimens of bovine distal femurs were carried out using the split-Hopkinson pressurebar (SHPB) technique at strain rates ranging from 100 to 700 s&lt;SUP&gt;-1&lt;/SUP&gt;. Quasi-static compression tests were also performed using an Instron-type materials testing machine at strain rates of 2&amp;times;10&lt;SUP&gt;-4&lt;/SUP&gt; and 2&amp;times;10&lt;SUP&gt;-3&lt;/SUP&gt; s&lt;SUP&gt;-1&lt;/SUP&gt;. Stiffness and ultimate strength were greater at greater apparent density and at higher strain rate. Both stress relaxation and creep functions were determined based on stress-time and strain-time relations obtained by the SHPB tests. Relaxation time and retardation time had no correlation with apparent density. The three-element standard linear solid model was then validated by these functions. The elastic spring stiffness of the model, E&lt;SUB&gt;1&lt;/SUB&gt;, had a strong positive correlation with apparent density, while the elastic spring stiffness, E&lt;SUB&gt;2&lt;/SUB&gt;, and the viscosity coefficient, &amp;eta;, showed less correlation with apparent density. No significant differences in the relaxation and retardation times, the elastic spring stiffnesses, E&lt;SUB&gt;1&lt;/SUB&gt;, E&lt;SUB&gt;2&lt;/SUB&gt;, and the viscosity coefficient, &amp;eta;, were observed between the specimens with and without marrow.

DOI： 10.1299/kikaia.63.2624

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A non-linear model is proposed to characterize the mechanical behaviour of compact bone and has been validated by mechanical tests on bovine femoral compact bone. The model consists of a non-linear spring and a non-linear dashpot in parallel. The method of identifying the viscoelastic parameters in the model is discussed. Impact and quasi-static compressive mechanical tests have shown that the model can be applied to bone to represent its mechanical behaviour at strain rates up to 100 s-1. The directional dependence of the viscoelastic parameters for the bone are determined and discussed. © 1994 Chapman &amp
Hall.

DOI： 10.1007/BF00058972

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMERICAN SOCIETY TESTING AND MATERIALS  

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Myofibrous organization was studied in human quadriceps femoris muscles (rectus femoris ; RF, vastus lateralis ; VL, vastus medialis ; VM, vastus intermedius ; VI) in 10 human subjects (5 males and 5 females, ages 44-86 years) . Muscle samples were embedded in celloidin and sections were stained with hematoxylin and eosin. The following results were obtained. 1) Muscle weights and cross-sectional areas were most predominant in VL, followed in order by VM, VI and RF. 2) Number of muscle fiber per sq mm was most predominant in RF (758), followed by VL (562), VM (474) and VI (461) . There was no difference between males and females. 3) VL had the most fibers in cross section, followed by VM, RF and VI. 4) Fiber sizes in VI, VM and VL were about 1300 μm<SUP>2</SUP> and differences among those muscles were small. Fibers in RF (about 1000 μm<SUP>2</SUP>) were smaller than those in the other three muscles. Quadriceps femoris muscle had larger muscle fiber size than other human muscles. 5) Density of muscle fibers was highest in RF (71%), and in other muscles were about 60%. The results suggest that VL, which had the largest cross-sectional area and total fiber number, functions most predominantly for knee extention.

DOI： 10.14930/jsma1939.51.186

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&lt;p&gt;Knowledge of the behavior of articular cartilage contact is one of the requirements in designing artificial joints that reproduce precise finger functions. The thumb has a different role from the other fingers, and when one of the other fingers moves, the thumb moves to the opposite position, enabling pinching and grasping, which are essential to activities of daily living (ADLs). The interphalangeal (IP), metacarpophalangeal (MCP), and trapeziometacarpal (TMC) joints give the thumb more degrees of freedom than the other fingers. The purpose of the present in vivo study was to clarify the static three-dimensional articular cartilage contact behavior of the thumb IP and MCP joints in positions of the thumb commonly used in ADLs (i.e., pinch and grasp positions) and also to analyze the changes of the articular cartilage contact area and movements three-dimensionally using magnetic resonance imaging.&lt;/p&gt;

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&lt;p&gt;Viscoelastic models are necessary to simulate the behavior of time-dependency materials such as polymer industrial products and biological tissues. Indentation test have been widely used in the many study because of its simplicity for estimate of local mechanical properties of bulk materials. This study obtained analytical solution of relaxation indentation problem of viscoelastic thin layer bonded on rigid substrate indented by flat-ended cylindrical punch using elastic-viscoelastic corresponding principle for axisymmetric elastic contact problem. The relaxation indentation test is conducted for two different polymer materials which are polymethyl methacrylate (PMMA) and polyvinyl chloride (PVC) and bovine articular cartilage of the femoral head. For bovine articular cartilage, normal cartilage treated by collagenase after relaxation indentation test and test is conducted again. The standard linear solids model is chosen as viscoelastic model in this study, then viscoelastic parameters of the model are determined by fitting experimental data collected from the relaxation indentation test. As results, the values of Root Mean Squared Error (RMSE) which indicate the error between experimental data and analytical solution show 0.59, 0.37 for respectively PMMA, PVC and 0.78, 0.52 for respectively normal and treated bovine articular cartilage. The results indicate articular cartilage needs more complicated viscoelastic model than the standard linear solid model. The analysis provide a fundamental basis for evaluating viscoelastic parameters of thin layer with the relaxation indentation test.&lt;/p&gt;

DOI： 10.1299/jsmemm.2017.OS1102

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&lt;p&gt;Assessment of in vivo articular contact behavior at the wrist joint are important for understanding the biomechanical functions under physiological and pathological loading. The objective of this study was to evaluate in vivo articular contact behavior between the radius and scaphoid and between the radius and lunate using a two-dimensional to three-dimensional image matching technique. Two normal male subjects were enrolled in this study. Biplanar X-ray images were taken during dosal flexion/palmar flexion and ulnar/radial deviation of the wrist joint. The articular contact was estimated from the joint space distance smaller than the cartilage layer thickness measured using a MRI scanner. The distributions of estimated contact area and the contact locations varied markedly with wrist position. The present result would be able to provide a fundamental knowledge about the biomechanics of the wrist joint.&lt;/p&gt;

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&lt;p&gt;The interphalangeal (IP) joint of the thumb are formed by the articulation between the proximal phalanges head (PPH) and the distal phalanges base (DPB). The measurement of the contact behavior, i.e., distribution and magnitude of the joint contact area with motion is necessary to understand the effects of loading on articular cartilage. The purpose of this study is to determine the in vivo contact behavior of the IP joint of thumb using the MRI. Five normal right thumbs from 5 healthy subjects were examined. Subjects were scanned with their dominant hand in three positions. Contact area was determined by measuring the length of contact between the PPH and DPB in each slice, multiplying this length by slice thickness of 1-mm, and summing these values. We found that the average cartilage contact area attains a minimum value in the neutral position. We also found that the distal phalanx of thumb IP joint was caused internal rotation on the distal phalanx with flexion.&lt;/p&gt;

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&lt;p&gt;The tooth axis is important as a morphological reference axis; however, a general definition of the tooth axis has not been established. This study presented a novel method of automatically calculating three-dimensional tooth axes on in vivo Cone-Beam Computed Tomography (CBCT) images. In this study, 36 teeth were obtained from 12 central and lateral incisors, and canines of 3 human subjects, respectively. Human in vivo images were obtained using a CBCT at a spatial resolution of 0.183 mm&lt;sup&gt;3&lt;/sup&gt; . The automatically tooth axis (PC-A) was calculated using principal component (PC) analysis of the segmented tooth and mandible. In experimental results using 36 teeth, the average relative angular errors between the tooth axes T-A manually specified by three dentists and the PC-A automatically calculated by the proposed method were 2.2 ± 1.4° for central incisors, 1.7 ± 1.0° for lateral incisors, 2.3 ± 1.4° for canines, respectively. The relative distance errors between the T-A and the PC-A were 0.39 ± 0.17 mm, 0.39 ± 0.21 mm and 0.63 ± 0.34 mm for central incisors, lateral incisors and canines, respectively. The experimental results of this study demonstrate that the proposed method of CBCT can accurately and automatically identify individual three-dimensional tooth axes.&lt;/p&gt;

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&lt;p&gt;Although the trajectories of skin markers tracked with an optical motion capture system have widely been used as the estimates of the underlying bone motions, the reliability of the kinematics parameters derived from the skin marker-based technique has often questioned due to soft tissue artefact. The objective of this study was to evaluate soft tissue artefact associated with knee flexion. One healthy female subject participated in this study. The subject underwent CT scan to reconstruct 3D femoral and tibial bone models. Twenty two polymeric markers with radio-opaque beads in its center were attached to the thigh and the shank. The initial coordinate transformation matrices were determined between skin marker cluster and the femur or the tibia using an image registration technique at extension of the knee. The movements of the femur and tibia from extension to 90° of flexion of the knee were recovered using two methods: 1) Placing the bone models according to the initial coordinate transformation matrices. 2) Placing the bone models using updated coordinate transformation matrices at every time step by a point-cluster technique. Although the latter method created more realistic bony movements especially at large knee flexion angles, a certain amount of soft tissue artefact still remained.&lt;/p&gt;

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&lt;p&gt;We consider an elastic contact problem for indentation test of layer-substrate body. An elastic layer assumed to be perfectly bonded to an elastic semi-infinite substrate. This problem called Boussinesq&#039;s problem which is axisymmetric mixed boundary value problem in elasticity theory. The elastic layer is smoothly indented by a flat-ended cylindrical and spherical indenter. The analytical solutions are obtained by solving an infinite system of simultaneous equations using the method of expressing a normal contact stress at the upper surface of the elastic layer as an appropriate series. Convergence can be achieved using less than 10 terms of the series. The accuracy of values of present numerical results is verified by comparing the dimensionless axial load of present results with results of some previous literatures. Additionally, this paper presents not only distribution of the dimensionless normal contact stress under cylindrical and spherical indenters but also distribution of the dimensionless normal displacement at the upper surface of the elastic layer. Numerical results are given for several combinations of the ratio of shear modulus, Poisson&#039;s ratio of elastic layer and substrate and the thickness of elastic layer. These results may establish the foundation for indentation test of layer-substrate composite and provide guideline for design of mechanical property of layered materials.&lt;/p&gt;

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The proximal interphalangeal (PIP) joint of the finger are formed by the articulation between the proximal phalanges head (PPH) and the middle phalanges base (MPB). The PPH has two rounded condyles, separated by a shallow central groove. The opposing surface of the MPB has two shallow concave facets separated by a central ridge. Determination of distribution of joint contact and joint motion are necessary to understanding the progression of joint deterioration and to the design of appropriate implants for finger joint arthroplasty. Traditionally, such data have been obtained from in vitro study of cadaveric specimens. Magnetic resonance imaging (MRI) has recently been shown to be a valid method of quantifying the joint contact area, indicating the potential for in vivo assessment. In the present study, we adapted an MRI system to study the three-dimensional in vivo articular cartilage contact areas and contact distributions of the PIP joint of the index finger on adopting three flexion angles.

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The tooth axis is an important as a morphological reference axis; however general definition of the tooth axis has not been established. This study presented a novel method of automatically calculating three-dimensional teeth axes in micro-CT images. In this study, 20 teeth specimens were obtained from five incisors, canines, premolars and molars, respectively. X-ray images were obtained using a micro-CT scanner at a spatial resolution of 33×33×33μm^3. The tooth axis was calculated using a principal component (PC) analysis on the segmented soft pulp and dentin. The teeth axes of PC-A_+ and PC-A__ were defined as the including of the pulp and not, respectively. No significant differences were noted in the experimental results between PC-A_+ and PC-A__. In experimental results using 20 teeth, the average relative angular errors between the teeth axes T-A manually specified by five dentists and automatically calculated PC-A_+ by the proposed method were 1.14±0.11 deg for incisor, 1.74±0.74 deg for canine, 3.51±0.43 deg for premolar and 2.90±0.57 deg for molar, respectively.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Articular cartilage provides joints with low friction and wear resistance essential for repetitive gliding motion and shock absorption, while evenly spreading the applied load onto the underlying bone. Mechanical factors are strongly implicated in the development of osteoarthritis, although the exact mechanisms are still not known. To aid in understanding whether mechanical factors are primary or secondary in the evolution of the degeneration of joint, knowledge of the contact stress distribution on the joint surface is needed. In this study, the static stress distribution on the surface of contact of two rigid spheres coated with elastic layers is estimated utilizing a mechanical model to simulate a diarthrodial joint. The problem is equivalent to the mixed boundary-value problem of the three-dimensional theory of elasticity. The dual integral equations are reduced to infinite systems of simultaneous equations by using the technique of expanding the normal contact stress with infinite series. The exact and complete analytical solution of contact stress is obtained. Numerical results are obtained with indication of the effect of the cartilage layer thickness, elastic modulus, Poisson&#039;s ratio and joint conformity on the contact stress distribution.

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Language：Japanese   Publisher：Japanese Society for Engineering Education  

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

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Language：Japanese   Publisher：日本実験力学会  

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Language：Japanese   Publisher：日本実験力学会  

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

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