https://sam.ensam.eu:443 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Mon, 13 Apr 2026 23:27:58 GMT 2026-04-13T23:27:58Z http://hdl.handle.net/10985/15997 Simulating the Remodelling of Bone around Implants FRAME, Jamie C.; CORTÉ, Laurent; ALLENA, Rachele; ROHAN, Pierre-Yves Introduction Improper osseointegration of implants leading to poor mechanical anchoring or embrittlement of neighboring bone is a major concern in orthopedic surgery [1?]. This integration is known to depend on the complex interplay between the mechanical environment and the cell activity in the tissues surrounding the implant. In order to accurately predict the success of an implant a robust description of the remodeling behavior of bone is required. Building upon previous research modeling osteogenesis around implants [2] a mechano-biological Finite Element (FE) model is proposed to describe the remodeling processes involved when bone, cartilage and fibrous tissue are submitted to mechanical loads. Method In this work, we describe the mechanostat (the interrelationship between loading conditions and remodeling) of bone [1] by modelling the net effect of cellular activities at the tissue level. For that, we distinguish the immature tissues resulting from the early proliferation steps (growth and diffusion) from the mature tissues obtained after a consolidation of the extra-cellular matrix (mineralization for bone). In each elementary volume element, the creation of new (immature) tissue is dependent upon the level of applied strain and is described by a reaction-diffusion equation. Results Using these equations a simple cantilever cyclic bending simulation was created and loaded to recreate a range of physiological strains experienced during bone remodeling. Preliminary results for bone tissue only are presented in Figure 1. This shows the cantilever boundary conditions and maximum normalized shear strain distribution which produce the evolution of immature and mature bone tissues over time. As the Young’s modulus increases proportionately with the increase in mature tissue density the strain under constant loading conditions is observed to reduce, therefore altering the generation of new tissue types. The model proposed here may offer numerous perspectives as a predictive tool for implant design or for the new therapies against bone resorption. Sun, 01 Jan 2017 00:00:00 GMT http://hdl.handle.net/10985/15997 2017-01-01T00:00:00Z FRAME, Jamie C. CORTÉ, Laurent ALLENA, Rachele ROHAN, Pierre-Yves Introduction Improper osseointegration of implants leading to poor mechanical anchoring or embrittlement of neighboring bone is a major concern in orthopedic surgery [1?]. This integration is known to depend on the complex interplay between the mechanical environment and the cell activity in the tissues surrounding the implant. In order to accurately predict the success of an implant a robust description of the remodeling behavior of bone is required. Building upon previous research modeling osteogenesis around implants [2] a mechano-biological Finite Element (FE) model is proposed to describe the remodeling processes involved when bone, cartilage and fibrous tissue are submitted to mechanical loads. Method In this work, we describe the mechanostat (the interrelationship between loading conditions and remodeling) of bone [1] by modelling the net effect of cellular activities at the tissue level. For that, we distinguish the immature tissues resulting from the early proliferation steps (growth and diffusion) from the mature tissues obtained after a consolidation of the extra-cellular matrix (mineralization for bone). In each elementary volume element, the creation of new (immature) tissue is dependent upon the level of applied strain and is described by a reaction-diffusion equation. Results Using these equations a simple cantilever cyclic bending simulation was created and loaded to recreate a range of physiological strains experienced during bone remodeling. Preliminary results for bone tissue only are presented in Figure 1. This shows the cantilever boundary conditions and maximum normalized shear strain distribution which produce the evolution of immature and mature bone tissues over time. As the Young’s modulus increases proportionately with the increase in mature tissue density the strain under constant loading conditions is observed to reduce, therefore altering the generation of new tissue types. The model proposed here may offer numerous perspectives as a predictive tool for implant design or for the new therapies against bone resorption. http://hdl.handle.net/10985/17059 A mechano-biological model of multi-tissue evolution in bone FRAME, Jamie C.; CORTÉ, Laurent; ALLENA, Rachele; ROHAN, Pierre-Yves Successfully simulating tissue evolution in bone is of significant importance in predicting various biological processes such as bone remodeling, fracture healing and osseointegration of implants. Each of these processes involves in different ways the permanent or transient formation of different tissue types, namely bone, cartilage and fibrous tissues. The tissue evolution in specific circumstances such as bone remodeling and fracturing healing is currently able to be modeled. Nevertheless, it remains challenging to predict which tissue types and organization can develop without any a priori assumptions. In particular, the role of mechano-biological coupling in this selective tissue evolution has not been clearly elucidated. In this work, a multi-tissue model has been created which simultaneously describes the evolution of bone, cartilage and fibrous tissues. The coupling of the biological and mechanical factors involved in tissue formation has been modeled by defining two different tissue states: an immature state corresponding to the early stages of tissue growth and representing cell clusters in a weakly neo-formed Extra Cellular Matrix (ECM), and a mature state corresponding to well-formed connective tissues. This has allowed for the cellular processes of migration, proliferation and apoptosis to be described simultaneously with the changing ECM properties through strain driven diffusion, growth, maturation and resorption terms. A series of finite element simulations were carried out on idealized cantilever bending geometries. Starting from a tissue composition replicating a mid-diaphysis section of a long bone, a steady-state tissue formation was reached over a statically loaded period of 10,000 h (60 weeks). The results demonstrated that bone formation occurred in regions which are optimally physiologically strained. In two additional 1000 h bending simulations both cartilaginous and fibrous tissues were shown to form under specific geometrical and loading cases and cartilage was shown to lead to the formation of bone in a beam replicating a fracture healing initial tissue distribution. This finding is encouraging in that it is corroborated by similar experimental observations of cartilage leading bone formation during the fracture healing process. The results of this work demonstrate that a multi-tissue mechano-biological model of tissue evolution has the potential for predictive analysis in the design and implementations of implants, describing fracture healing and bone remodeling processes. Tue, 01 Jan 2019 00:00:00 GMT http://hdl.handle.net/10985/17059 2019-01-01T00:00:00Z FRAME, Jamie C. CORTÉ, Laurent ALLENA, Rachele ROHAN, Pierre-Yves Successfully simulating tissue evolution in bone is of significant importance in predicting various biological processes such as bone remodeling, fracture healing and osseointegration of implants. Each of these processes involves in different ways the permanent or transient formation of different tissue types, namely bone, cartilage and fibrous tissues. The tissue evolution in specific circumstances such as bone remodeling and fracturing healing is currently able to be modeled. Nevertheless, it remains challenging to predict which tissue types and organization can develop without any a priori assumptions. In particular, the role of mechano-biological coupling in this selective tissue evolution has not been clearly elucidated. In this work, a multi-tissue model has been created which simultaneously describes the evolution of bone, cartilage and fibrous tissues. The coupling of the biological and mechanical factors involved in tissue formation has been modeled by defining two different tissue states: an immature state corresponding to the early stages of tissue growth and representing cell clusters in a weakly neo-formed Extra Cellular Matrix (ECM), and a mature state corresponding to well-formed connective tissues. This has allowed for the cellular processes of migration, proliferation and apoptosis to be described simultaneously with the changing ECM properties through strain driven diffusion, growth, maturation and resorption terms. A series of finite element simulations were carried out on idealized cantilever bending geometries. Starting from a tissue composition replicating a mid-diaphysis section of a long bone, a steady-state tissue formation was reached over a statically loaded period of 10,000 h (60 weeks). The results demonstrated that bone formation occurred in regions which are optimally physiologically strained. In two additional 1000 h bending simulations both cartilaginous and fibrous tissues were shown to form under specific geometrical and loading cases and cartilage was shown to lead to the formation of bone in a beam replicating a fracture healing initial tissue distribution. This finding is encouraging in that it is corroborated by similar experimental observations of cartilage leading bone formation during the fracture healing process. The results of this work demonstrate that a multi-tissue mechano-biological model of tissue evolution has the potential for predictive analysis in the design and implementations of implants, describing fracture healing and bone remodeling processes. http://hdl.handle.net/10985/17055 Optimal bone structure is dependent on the interplay between mechanics and cellular activities FRAME, Jamie C.; CORTÉ, Laurent; ALLENA, Rachele; ROHAN, Pierre-Yves Bone is a tissue with the remarkable capacity to adapt its structure to an optimized microstructural form depending on variations in the loading conditions. The remodeling process in bone produces distinct tissue distributions such as cortical and trabecular bone but also fibrous and cartilage tissues. Although it has been demonstrated that mechanical factors play a decisive role in the architectural optimization, it may also follow that biological factors have an influence. This interplay between loading and physiology has not been previously reported but is paramount for a proper assessment of bone remodeling outcomes. In this work we present a mechanostat model for bone remodeling which is shown to predict the mechanically driven homeostasis. It is further demonstrated that the steady-state reached is innately dependent upon the loading magnitudes and directions. The model was then adjusted to demonstrate the influence of specific biological factors such as cell proliferation, migration and resorption. Furthermore, two scenarios were created to replicate the physiological conditions of two bone disorders – osteoporosis and osteopetrosis – where the results show that there is a significant distinction between the homeostatic structures reached in each case and that the tissue adaptations follow similar trends to those observed in clinical studies. Mon, 01 Jan 2018 00:00:00 GMT http://hdl.handle.net/10985/17055 2018-01-01T00:00:00Z FRAME, Jamie C. CORTÉ, Laurent ALLENA, Rachele ROHAN, Pierre-Yves Bone is a tissue with the remarkable capacity to adapt its structure to an optimized microstructural form depending on variations in the loading conditions. The remodeling process in bone produces distinct tissue distributions such as cortical and trabecular bone but also fibrous and cartilage tissues. Although it has been demonstrated that mechanical factors play a decisive role in the architectural optimization, it may also follow that biological factors have an influence. This interplay between loading and physiology has not been previously reported but is paramount for a proper assessment of bone remodeling outcomes. In this work we present a mechanostat model for bone remodeling which is shown to predict the mechanically driven homeostasis. It is further demonstrated that the steady-state reached is innately dependent upon the loading magnitudes and directions. The model was then adjusted to demonstrate the influence of specific biological factors such as cell proliferation, migration and resorption. Furthermore, two scenarios were created to replicate the physiological conditions of two bone disorders – osteoporosis and osteopetrosis – where the results show that there is a significant distinction between the homeostatic structures reached in each case and that the tissue adaptations follow similar trends to those observed in clinical studies. http://hdl.handle.net/10985/17060 Functional evaluation of anterior cruciate ligagment autografts in pre-clinical animal models SKALLI, Wafa; TRNKA, Julien; MANASSERO, Mathieu; VIATEAU, Véronique; CAROUX, Julien; CORTÉ, Laurent; ROHAN, Pierre-Yves; PILLET, Helene Introduction Rupture of the Anterior Cruciate Ligament (ACL) affects about 1 person over 3000 every year. The current standard care is based on ligament reconstruction by autograft from tendon tissues and is considered as the gold standard. Yet, autograft reconstruction presents serious limitations. Recent developments in artificial ligaments are promising and could potentially address the currently growing demand from surgeons and patients for an off-the-shelf alternate solution. However, before these can be commonly used in clinical routine, their biocompatibility and biomechanical performance for the short and long terms must be studied in pre-clinical animal models. Building upon the work of [1], we propose in this contribution a methodology for assessing the biomechanical performance of artificial ligaments, and to provide reference data (autografts) using an animal model (sheep) at 3 months after implantation. Materials and Methods Surgery and specimen preparation 14 fresh frozen lower limbs were used in this study, seven left (autograft implantation) and seven right (contralateral) knees. These were harvested from seven sheep sacrificed 3 months after implantation. The biomechanical analysis of the knees consisted of four successive in vitro experiments: three kinematics tests (flexion-extension, varus-valgus laxity and anterior drawer tests) and a pull-out destructive test. Kinematics analysis: flexion-extension and laxity tests The kinematic analysis was performed using specific motorized devices adapted from previously described and validated ones [1]. The protocol combined motion analysis of tripods screwed in the bony structures and 3D personalized reconstruction (figure 1) from low-dose X-ray system (EOS, EOS Imaging, Paris, France) [1,2,3,4]. Pull-out destructive tests The pull-out tests were performed using an INSTRON 5566 testing machine (Instron Ltd., Buckingham-shire, England) instrumented with a 5 kN load cell. After conditioning, a tension load was applied to the specimen (5 mm/min) until total failure. Data analysis: mobility assessment and statistical tests The following parameters were extracted to allow the comparison with the literature [1] (i) Internal rotation Ry (°) value for a 40° flexion angle (Ry_40), (ii) Anterior Tibial Translation (mm) for 100 N loading (ATT_100), (iii) Varus Valgus amplitude (°) at 4 Nm loading (VV_4) and (iv) the Failure load (N) (FL). Results and discussion The results shows a good consistency for kinematic parameters of the contralateral knees. The failure load was clearly different due to the interindividual variability. As concerns the autograft, a reduction of internal rotation during the flexion motion and an increase of the laxity in ATT could be observed. The failure load was also decreased for the grafted knee. Sun, 01 Jan 2017 00:00:00 GMT http://hdl.handle.net/10985/17060 2017-01-01T00:00:00Z SKALLI, Wafa TRNKA, Julien MANASSERO, Mathieu VIATEAU, Véronique CAROUX, Julien CORTÉ, Laurent ROHAN, Pierre-Yves PILLET, Helene Introduction Rupture of the Anterior Cruciate Ligament (ACL) affects about 1 person over 3000 every year. The current standard care is based on ligament reconstruction by autograft from tendon tissues and is considered as the gold standard. Yet, autograft reconstruction presents serious limitations. Recent developments in artificial ligaments are promising and could potentially address the currently growing demand from surgeons and patients for an off-the-shelf alternate solution. However, before these can be commonly used in clinical routine, their biocompatibility and biomechanical performance for the short and long terms must be studied in pre-clinical animal models. Building upon the work of [1], we propose in this contribution a methodology for assessing the biomechanical performance of artificial ligaments, and to provide reference data (autografts) using an animal model (sheep) at 3 months after implantation. Materials and Methods Surgery and specimen preparation 14 fresh frozen lower limbs were used in this study, seven left (autograft implantation) and seven right (contralateral) knees. These were harvested from seven sheep sacrificed 3 months after implantation. The biomechanical analysis of the knees consisted of four successive in vitro experiments: three kinematics tests (flexion-extension, varus-valgus laxity and anterior drawer tests) and a pull-out destructive test. Kinematics analysis: flexion-extension and laxity tests The kinematic analysis was performed using specific motorized devices adapted from previously described and validated ones [1]. The protocol combined motion analysis of tripods screwed in the bony structures and 3D personalized reconstruction (figure 1) from low-dose X-ray system (EOS, EOS Imaging, Paris, France) [1,2,3,4]. Pull-out destructive tests The pull-out tests were performed using an INSTRON 5566 testing machine (Instron Ltd., Buckingham-shire, England) instrumented with a 5 kN load cell. After conditioning, a tension load was applied to the specimen (5 mm/min) until total failure. Data analysis: mobility assessment and statistical tests The following parameters were extracted to allow the comparison with the literature [1] (i) Internal rotation Ry (°) value for a 40° flexion angle (Ry_40), (ii) Anterior Tibial Translation (mm) for 100 N loading (ATT_100), (iii) Varus Valgus amplitude (°) at 4 Nm loading (VV_4) and (iv) the Failure load (N) (FL). Results and discussion The results shows a good consistency for kinematic parameters of the contralateral knees. The failure load was clearly different due to the interindividual variability. As concerns the autograft, a reduction of internal rotation during the flexion motion and an increase of the laxity in ATT could be observed. The failure load was also decreased for the grafted knee. http://hdl.handle.net/10985/22575 A wear model to predict damage of reconstructed ACL MAEZTU REDIN, Deyo; CAROUX, Julien; ROHAN, Pierre-Yves; PILLET, Helene; CERMOLACCE, Alexia; TRNKA, Julien; MANASSERO, Mathieu; VIATEAU, Véronique; CORTÉ, Laurent Impingement with surrounding tissues is a major cause of failure of anterior cruciate ligament reconstruction. However, the complexity of the knee kinematics and anatomical variations make it difficult to predict the occurrence of contact and the extent of the resulting damage. Here we hypothesise that a description of wear between the reconstructed ligament and adjacent structures captures the in vivo damage produced with physiological loadings. To test this, we performed an in vivo study on a sheep model and investigated the role of different sources of damage: overstretching, excessive twist, excessive compression, and wear. Seven sheep underwent cranial cruciate ligament reconstruction using a tendon autograft. Necropsy observations and pull-out force measurements performed postoperatively at three months showed high variability across specimens of the extent and location of graft damage. Using 3D digital models of each stifle based on X-ray imaging and kinematics measurements, we determined the relative displacements between the graft and the surrounding bones and computed a wear index describing the work of friction forces underwent by the graft during a full flexion-extension movement. While tensile strain, angle of twist and impingement volume showed no correlation with pull-out force (ρ = −0.321, p = 0.498), the wear index showed a strong negative correlation (r = −0.902, p = 0.006). Moreover, contour maps showing the distribution of wear on the graft were consistent with the observations of damage during the necropsy. These results demonstrate that wear is a good proxy of graft damage. The proposed wear index could be used in implant design and surgery planning to minimise the risk of implant failure. Its application to sheep can provide a way to increase preclinical testing efficiency. Thu, 01 Sep 2022 00:00:00 GMT http://hdl.handle.net/10985/22575 2022-09-01T00:00:00Z MAEZTU REDIN, Deyo CAROUX, Julien ROHAN, Pierre-Yves PILLET, Helene CERMOLACCE, Alexia TRNKA, Julien MANASSERO, Mathieu VIATEAU, Véronique CORTÉ, Laurent Impingement with surrounding tissues is a major cause of failure of anterior cruciate ligament reconstruction. However, the complexity of the knee kinematics and anatomical variations make it difficult to predict the occurrence of contact and the extent of the resulting damage. Here we hypothesise that a description of wear between the reconstructed ligament and adjacent structures captures the in vivo damage produced with physiological loadings. To test this, we performed an in vivo study on a sheep model and investigated the role of different sources of damage: overstretching, excessive twist, excessive compression, and wear. Seven sheep underwent cranial cruciate ligament reconstruction using a tendon autograft. Necropsy observations and pull-out force measurements performed postoperatively at three months showed high variability across specimens of the extent and location of graft damage. Using 3D digital models of each stifle based on X-ray imaging and kinematics measurements, we determined the relative displacements between the graft and the surrounding bones and computed a wear index describing the work of friction forces underwent by the graft during a full flexion-extension movement. While tensile strain, angle of twist and impingement volume showed no correlation with pull-out force (ρ = −0.321, p = 0.498), the wear index showed a strong negative correlation (r = −0.902, p = 0.006). Moreover, contour maps showing the distribution of wear on the graft were consistent with the observations of damage during the necropsy. These results demonstrate that wear is a good proxy of graft damage. The proposed wear index could be used in implant design and surgery planning to minimise the risk of implant failure. Its application to sheep can provide a way to increase preclinical testing efficiency.