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Nanomechanical and tribological investigation of human knee joints
Track 3. Musculoskeletal systems and Performance-Joint ISB/ESB
$499
4614 We-Th, no. 102 (P57) Which forces must fixations of meniscus implants withstand? L. DiJrselen, B. Pap, T. Wehner, A. Seitz, L. Claes, U. Simon. Institute ef
5232 We-Th, no. 104 (P57) Scapholunate ligament in carpal kinematics: An anatomical study A. Azhar 1, S. Whiten 2, L. Cochrane 3, R. Abboud 3, C. Wigderowitz 1.
Orthopaedic Research and Biomechanics, University of UIm, Germany
1Orthopaedic & Trauma Surgery, University of Dundee, Scotland, UK, 2Department of Anatomy, University of StAndrews, Scotland, UK, 3Institute of Motion Analysis and Research (IMAR), University of Dundee, Scotland, UK
Introduction: Forces acting in the menisci are subject of only few studies [1,2]. For the design of tissue engineered meniscal replacement devices it is important to known the loads menisci are exposed to. Especially the forces acting in the meniscal ligaments must be known to set up adequate requirements for an anchoring system. Insufficient fixation of a meniscus replacement implant would prevent it from reducing the joint contact pressure. Therefore the aim of this Finite Element (FE) study was to calculate the tensile forces acting in the meniscal ligaments. Methods: A finite element model was created using MRI scans of a knee joint of a healthy human subject in extension position. Segmentation was carried out with the visualization software AMIRA (Mercury Computer Systems). The FE model with 23160 tetrahedrons comprised distal femur, proximal tibia, and both menisci. Their ligamentous fixations were modelled as linear springs. We described the interface between the femoral condyles, menisci and tibial surface by frictionless surface contact elements. In this preliminary scenario we assumed linearly elastic, isotropic material behaviour (Moduli: bone 10000 MPa, cartilage 10 MPa, menisci 50 MPa, meniscal ligaments 150450 N/mm depending on length). The investigated load cases were (i) axial joint compression induced by an axial displacement of 0.5 mm, (ii) 2 mm anterior displacement and (iii) 5 mm medial displacement of the femur relative to the tibia. Results: The maximum forces in the meniscal ligaments ranged between 4.8 and 28.5 N depending on load case and horn location. Discussion: The low forces in the meniscal ligaments calculated in this FE study with simplified boundary conditions suggest that fixation systems for meniscal replacement devices do not need to bear high loads. However, introducing e.g. non-linear and non-isotropic material behaviour and friction between the joint and meniscal surfaces and verification by an in vitro experiment will show whether the acquired results are realistic.
The scapholunate area is most vulnerable area to injury in the wrist. The pattern of injury to the wrist ligaments following trauma is still unclear. The different imaging techniques often prove inconclusive which makes the diagnosis difficult and treatment controversial. The aim of this cadaveric wrist study was to evaluate the differences in scapholunate kinematics before and after sectioning the scapholunate interosseous ligament (SLIL) and radioscaphocapitate (RSC) ligament. Fifteen embalmed cadaveric wrists were studied. There were three male and twelve female wrists with an average age of 84 years. The skin, subcutaneous tissue, the extensor and flexors tendons of the wrist were removed leaving the wrist capsule intact. Metal pointers with 1.5 mm diameter were inserted into the scaphoid and lunate. A special jig was used to act as wrist simulator and the wrist was moved through a cycle of flexion, extension, ulnar and radial deviations. All the movements were repeated three times. Photographs were taken and measured with MB-Ruler ® software. Analysis of variance was done using SPSS 12® for Windows. There was no angle between the metal wires when the ligaments were intact but after sectioning SLIL, a significant angle (p<0.001) between the wires appeared in all movements. Subsequent sectioning of the RSC ligament further increased the angle (p <0.001), but this increase in angle was much smaller than that after sectioning SLIL. In conclusion, this study supports the hypothesis that the SLIL is the primary stabilizer of the scapholunate articulation and its damage can cause severe carpal instability. The RSC ligament is a secondary stabilizer with little influence on the carpal stability. Injury to the SLIL is essential to be repaired to avoid further damage to the wrist.
References [1] Haut Donahue. J Biomech 2003; 36: 19-34. [2] Pena. Clin Biomech 2005; 20: 498-507.
Track 3
7611 We-Th, no. 103 (P57) Tensile and relaxation properties of healing patellar tendons from biglycan knockout mice H. Fujie 1, W. Ando 2, H. Yamamoto 1, H. Yoshikawa 2, N. Nakamura 2.
1Biomechanics Laboratory, Kogakuin University, Tokyo, Japan, 2Department of Orthopaedic Surgery, Osaka University Medical School, Osaka, Japan Introduction: Tendon proteoglycans (PGs) play important roles for matrix assembly and organization. However, little is known with regard to the effect of the PGs on tendon healing process although it has been determined that the PGs affect the mechanical properties of intact patellar tendon (PT) in knockout mouse studies [1]. We have been investigating the significance of specific PG, biglycan (Bgn), which is overexpressed in healing ligament tissue [2], in the healing process of PTs using Bgn-knockout mice (BKO mice) that hereditarity lack in Bgn [3]. Methods: The BKO mice (C3H/HeN) were subjected to the experiment at the age of 12 weeks. The midsubstance of the PTs of 2 - 3 mm in longitudinal length were surgically removed, followed by cage activity for subseguent 8 weeks. After the sacrifice, the patella-I/3 healing PT-tibia complex was subjected to tensile and relaxation tests in physiological saline solution. For comparison, PTs from normal mice were subjected to the experimental procedure same as that for BKO mice. Results and Discussion: In intact PTs, the absence of Bgn resulted in increased tangent modulus, while leaving the maximum stress to a normal value. In healing PTs, however, the lack in Bgn decreased the maximum stress, while leaving the modulus to a normal value. Note that rupture occurred at tibial insertion site and patellar insertion site in healing PTs of BKO mice. Stress relaxation was smaller in BKO mice than in intact mice for both normal and healing PTs. These results suggest that the Bgn plays important roles for mechanical properties of healing PTs. References [1] Robinson PS, et al. J Biomech Eng. (ASME) 2005; 127: 181-185. [2] Boykew R, et al. Matrix Bio11998; 17: 371-378. [3] Fujie H., et al. Abst. of Annual Meeting of the Japanese Society for Clinical Biomechanics 2004; 217.
Musculoskeletal systems and Performance-Joint ISB/ESB 6788 Mo-Tu, no. 1 (P57) Nanomechanical and tribological investigation of human knee joints B. Ning 1, R. Ribeiro 1, G. Kim 1, M. Usta 2, A.H. Ucisik 3, H. Liang 1. 1Mechanica/
Engineering Department, MS 3123, Texas A&M University, College Station, TX, USA, 2 Gebze Institute of Technology, Department of Materials Science and Engineering, Gebze/Kocaeli, Turkey, 3Begazici University, Institute of Biomedical Engineering, Department of Prostheses, Materials and Artificial Organs, Bebek-lstanbul, Turkey Total joint replacement has improved the quality of life for millions of patients who encounter joint disease or injury. Yet, the replacement faces a limited lifespan due to wear and failure. In order to optimize the performance of joint materials, we investigate the mechanical and tribological properties of real human knees. In this research, we investigate the load bearing capabilities of human bones around a knee joint, femur, tibia, and fibula along with the cartilage. We conducted nanoindentation and tribological investigation using a nanoindentor and a tribometer. Results showed visible viscoelastic behavior of cartilage and less so on bones. The consistent friction coefficient data indicated the modification of contact condition due to stress. 5055 Mo-Tu, no. 2 (P57) One-legged stance - a representative body position for the long term effect of the hip contact stress M. Daniel 1,2, A. Igli~ 3, V. Kralj-lgli~ 3,4,5. 1Faculty ef Mechanical Engineering,
Technical University of Kof,ice, Ko'~ice, Slovakia, 2Faculty of Mechanical Engineering, Czech Technical University in Prague, Prague, Czech Republic, 3Laboratory of Physics, Faculty of Electrical Engineering, University of Ljubljana, Ljubljana, Slovenia, 4Institute of Biophysics, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia, 5Nomadic College, Brussels, Belgium Mathematical models have been widely used to determine contact stress distribution in the human hips [1]. It has been suggested recently that the temporal and spatial aspects of contact stress distribution may be more important for the hip development than the value of the peak stress itself [1]. Based on this presumption, the stress distribution averaged during the hip
$499
4614 We-Th, no. 102 (P57) Which forces must fixations of meniscus implants withstand? L. DiJrselen, B. Pap, T. Wehner, A. Seitz, L. Claes, U. Simon. Institute ef
5232 We-Th, no. 104 (P57) Scapholunate ligament in carpal kinematics: An anatomical study A. Azhar 1, S. Whiten 2, L. Cochrane 3, R. Abboud 3, C. Wigderowitz 1.
Orthopaedic Research and Biomechanics, University of UIm, Germany
1Orthopaedic & Trauma Surgery, University of Dundee, Scotland, UK, 2Department of Anatomy, University of StAndrews, Scotland, UK, 3Institute of Motion Analysis and Research (IMAR), University of Dundee, Scotland, UK
Introduction: Forces acting in the menisci are subject of only few studies [1,2]. For the design of tissue engineered meniscal replacement devices it is important to known the loads menisci are exposed to. Especially the forces acting in the meniscal ligaments must be known to set up adequate requirements for an anchoring system. Insufficient fixation of a meniscus replacement implant would prevent it from reducing the joint contact pressure. Therefore the aim of this Finite Element (FE) study was to calculate the tensile forces acting in the meniscal ligaments. Methods: A finite element model was created using MRI scans of a knee joint of a healthy human subject in extension position. Segmentation was carried out with the visualization software AMIRA (Mercury Computer Systems). The FE model with 23160 tetrahedrons comprised distal femur, proximal tibia, and both menisci. Their ligamentous fixations were modelled as linear springs. We described the interface between the femoral condyles, menisci and tibial surface by frictionless surface contact elements. In this preliminary scenario we assumed linearly elastic, isotropic material behaviour (Moduli: bone 10000 MPa, cartilage 10 MPa, menisci 50 MPa, meniscal ligaments 150450 N/mm depending on length). The investigated load cases were (i) axial joint compression induced by an axial displacement of 0.5 mm, (ii) 2 mm anterior displacement and (iii) 5 mm medial displacement of the femur relative to the tibia. Results: The maximum forces in the meniscal ligaments ranged between 4.8 and 28.5 N depending on load case and horn location. Discussion: The low forces in the meniscal ligaments calculated in this FE study with simplified boundary conditions suggest that fixation systems for meniscal replacement devices do not need to bear high loads. However, introducing e.g. non-linear and non-isotropic material behaviour and friction between the joint and meniscal surfaces and verification by an in vitro experiment will show whether the acquired results are realistic.
The scapholunate area is most vulnerable area to injury in the wrist. The pattern of injury to the wrist ligaments following trauma is still unclear. The different imaging techniques often prove inconclusive which makes the diagnosis difficult and treatment controversial. The aim of this cadaveric wrist study was to evaluate the differences in scapholunate kinematics before and after sectioning the scapholunate interosseous ligament (SLIL) and radioscaphocapitate (RSC) ligament. Fifteen embalmed cadaveric wrists were studied. There were three male and twelve female wrists with an average age of 84 years. The skin, subcutaneous tissue, the extensor and flexors tendons of the wrist were removed leaving the wrist capsule intact. Metal pointers with 1.5 mm diameter were inserted into the scaphoid and lunate. A special jig was used to act as wrist simulator and the wrist was moved through a cycle of flexion, extension, ulnar and radial deviations. All the movements were repeated three times. Photographs were taken and measured with MB-Ruler ® software. Analysis of variance was done using SPSS 12® for Windows. There was no angle between the metal wires when the ligaments were intact but after sectioning SLIL, a significant angle (p<0.001) between the wires appeared in all movements. Subsequent sectioning of the RSC ligament further increased the angle (p <0.001), but this increase in angle was much smaller than that after sectioning SLIL. In conclusion, this study supports the hypothesis that the SLIL is the primary stabilizer of the scapholunate articulation and its damage can cause severe carpal instability. The RSC ligament is a secondary stabilizer with little influence on the carpal stability. Injury to the SLIL is essential to be repaired to avoid further damage to the wrist.
References [1] Haut Donahue. J Biomech 2003; 36: 19-34. [2] Pena. Clin Biomech 2005; 20: 498-507.
Track 3
7611 We-Th, no. 103 (P57) Tensile and relaxation properties of healing patellar tendons from biglycan knockout mice H. Fujie 1, W. Ando 2, H. Yamamoto 1, H. Yoshikawa 2, N. Nakamura 2.
1Biomechanics Laboratory, Kogakuin University, Tokyo, Japan, 2Department of Orthopaedic Surgery, Osaka University Medical School, Osaka, Japan Introduction: Tendon proteoglycans (PGs) play important roles for matrix assembly and organization. However, little is known with regard to the effect of the PGs on tendon healing process although it has been determined that the PGs affect the mechanical properties of intact patellar tendon (PT) in knockout mouse studies [1]. We have been investigating the significance of specific PG, biglycan (Bgn), which is overexpressed in healing ligament tissue [2], in the healing process of PTs using Bgn-knockout mice (BKO mice) that hereditarity lack in Bgn [3]. Methods: The BKO mice (C3H/HeN) were subjected to the experiment at the age of 12 weeks. The midsubstance of the PTs of 2 - 3 mm in longitudinal length were surgically removed, followed by cage activity for subseguent 8 weeks. After the sacrifice, the patella-I/3 healing PT-tibia complex was subjected to tensile and relaxation tests in physiological saline solution. For comparison, PTs from normal mice were subjected to the experimental procedure same as that for BKO mice. Results and Discussion: In intact PTs, the absence of Bgn resulted in increased tangent modulus, while leaving the maximum stress to a normal value. In healing PTs, however, the lack in Bgn decreased the maximum stress, while leaving the modulus to a normal value. Note that rupture occurred at tibial insertion site and patellar insertion site in healing PTs of BKO mice. Stress relaxation was smaller in BKO mice than in intact mice for both normal and healing PTs. These results suggest that the Bgn plays important roles for mechanical properties of healing PTs. References [1] Robinson PS, et al. J Biomech Eng. (ASME) 2005; 127: 181-185. [2] Boykew R, et al. Matrix Bio11998; 17: 371-378. [3] Fujie H., et al. Abst. of Annual Meeting of the Japanese Society for Clinical Biomechanics 2004; 217.
Musculoskeletal systems and Performance-Joint ISB/ESB 6788 Mo-Tu, no. 1 (P57) Nanomechanical and tribological investigation of human knee joints B. Ning 1, R. Ribeiro 1, G. Kim 1, M. Usta 2, A.H. Ucisik 3, H. Liang 1. 1Mechanica/
Engineering Department, MS 3123, Texas A&M University, College Station, TX, USA, 2 Gebze Institute of Technology, Department of Materials Science and Engineering, Gebze/Kocaeli, Turkey, 3Begazici University, Institute of Biomedical Engineering, Department of Prostheses, Materials and Artificial Organs, Bebek-lstanbul, Turkey Total joint replacement has improved the quality of life for millions of patients who encounter joint disease or injury. Yet, the replacement faces a limited lifespan due to wear and failure. In order to optimize the performance of joint materials, we investigate the mechanical and tribological properties of real human knees. In this research, we investigate the load bearing capabilities of human bones around a knee joint, femur, tibia, and fibula along with the cartilage. We conducted nanoindentation and tribological investigation using a nanoindentor and a tribometer. Results showed visible viscoelastic behavior of cartilage and less so on bones. The consistent friction coefficient data indicated the modification of contact condition due to stress. 5055 Mo-Tu, no. 2 (P57) One-legged stance - a representative body position for the long term effect of the hip contact stress M. Daniel 1,2, A. Igli~ 3, V. Kralj-lgli~ 3,4,5. 1Faculty ef Mechanical Engineering,
Technical University of Kof,ice, Ko'~ice, Slovakia, 2Faculty of Mechanical Engineering, Czech Technical University in Prague, Prague, Czech Republic, 3Laboratory of Physics, Faculty of Electrical Engineering, University of Ljubljana, Ljubljana, Slovenia, 4Institute of Biophysics, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia, 5Nomadic College, Brussels, Belgium Mathematical models have been widely used to determine contact stress distribution in the human hips [1]. It has been suggested recently that the temporal and spatial aspects of contact stress distribution may be more important for the hip development than the value of the peak stress itself [1]. Based on this presumption, the stress distribution averaged during the hip