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P-4 Biocompatibility and Bioactivity of Bearing Loaded Metallic Implants
Plenary Lectures / Journal of Biomechanics 43S1 (2010) S3–S14
and macrophages are recruited within the first 24 hours after tendon injury to clean up necrotic materials and cells, and release some growth factors for the initiation of the second phase, proliferation, which starts a few days after the inflammatory phase, and lasts up to six weeks. This is the most crucial phase in connective tissue healing. The size of the local cell population is an important factor influencing the amount of proliferation in the second healing phase. However, the flexor tendon is hypovascular and hypocellular, resulting in a long-term healing process compared to other tissue healing. The most common complications following tendon repair occur during this phase. Strategies to improve tendon healing, therefore, mostly focus on in this phase, including cell-based therapy, growth factors stimulation, platelet rich plasma (PRP) augmentation, and some physical modalities. The last phase of healing, remodeling, is critical for functional tissue regeneration. During this phase, cytokines, such as MMPs, and mechanical stimulation are the most influential parameters. For flexor tendon remodeling, mechanical strength should allow muscle force transmission and also a smooth surface must be restored to enable functional performance. Intrinsic healing indicates that tissues can be directly healed by proliferation of residual cells within injured tissues, which results in superior outcomes. Intrinsic healing of flexor tendons mainly relies on the migration of epitenon cells from the tendon surface into the lacerated tendon ends since the endotenon cells have less capability to proliferate and differentiate. In contrast, extrinsic healing relies on the invasion of cells from the surrounding tissues to bridge tendons together, which leads to adhesion formation between tendon and surrounding tissues, hindering tendon gliding. However, extrinsic healing is faster and more abundant compared to intrinsic healing due to a rich blood supply and high cellularity in the surrounding soft tissues. Elimination or reduction of extrinsic healing has been investigated with the strategies of physicochemical and pharmacological interventions, but at some cost in terms of delayed or impaired tendon intrinsic healing as shown in our recent studies. Postoperative rehabilitation is also an effective therapy to decrease the adhesions formed by extrinsic healing. However, inappropriate motion therapy can also cause gap formation, and even repaired tendon rupture. Maximization of intrinsic healing and minimization of extrinsic healing still remains a great clinical and research challenge. Finally, tendon healing has two patterns of healing, i.e. contact healing and gap healing. Contact healing indicates that lacerated tendon ends directly contact each other; the tendon heals by first intention and is dominated by intrinsic healing. Most connective tissues heal by this phenomenon, such as bone, skin, and other less tensile tissues. However, the tendon, especially flexor tendon healing, primarily follows gap healing, which is similar to wound healing in the secondary intention. The function of tendon is to transmit muscle force to the bone to move joints. Tensile force always exists during joint motion, especially during postoperative rehabilitation, which is often performed to prevent adhesion formation in the early stage following tendon repair. Although lacerated tendon ends can be brought together by surgical repairs, the tensile force often causes the gap formation at the repair site. This gap healing not only elongates the healing phases, but also involves more extrinsic healing. The strategies to eliminate gap healing have been studied for many decades, including strong repair techniques, suture materials, and postoperative rehabilitation protocols, but tendon gap healing still remains an unavoidable problem. In summary, flexor tendon healing, like other connective tissues, has two physical forms (contact and gap healing) and two healing resources (intrinsic and extrinsic healing) through three healing phases (inflammation, proliferation, and remodeling). The fundamental strategies to improve the outcomes of flexor tendon injury and repair should focus primarily on achieving contact healing, secondarily on eliminating extrinsic healing, and then
S5
finally shortening the healing phases. This principle is also applicable to healing of other connective tissues. P-4 Biocompatibility and Bioactivity of Bearing Loaded Metallic Implants A. Zielinski, S. Sobieszczyk, B. Swieczko-Zurek, A. Ossowska, T. Seramak, W. Serbinski. Gdansk University of Technology, Poland The aim of the presented project is to develop the Titanium (Ti) alloy base composite materials possessing better biocompatibility, longer lifetime and bioactivity behavior for bearing loaded implants, e.g. hip joint and knee joint endoprosthesis. The development of such material will be performed through modeling the material behavior in biological environment in long time and develop new procedures for such evaluation; obtain the extremely biocompatible Ti alloy with design porosity; develop the oxidation technology resulting in high corrosion resistance and bioactivity; develop the technologies of deposition of Hydroxyapatite (HA) based composite bioactive coatings; develop the technologies of obtaining the bioactive composite core materials placed within the pores. The examinations of degradation of Ti implants are carried out in order to recognize the sources of both short allergies and inflammation, and long term degradation. The theoretical assessment of corrosion is made assuming as caused by three processes: Electrochemical dissolution through imperfections of anodic oxide layer, diffusion the metallic ions through oxides, and dissolution of oxides themselves. In order to increase the biocompatibility the toxic elements, Aluminum (Al) and Vanadium (V) are eliminated. The experiments have shown that titanium–zirconium–niobium (Ti-Zr-Nb) alloy may be such a material that can also be prepared by powder metallurgy (P/M) technique. The porous (scaffold) Ti-Zr-Nb alloy is obtained by powder metallurgy, classical and with spacing holders used before melting and decomposed, or used during melting and removed by subsequent water dissolution. The oxidation of porous materials will be performed by electrochemical technique in special electrolytes in order to obtain the oxide layers well adjacent to an interface, preventing the base metal against corrosion and bioactive because of nanotubular structure, permitting injection of antibiotics into the pores. The Calcium (Ca), Oxygen (O) and Nitrogen (N) ion implantation or deposition of Zirconia sublayers will be explored to increase the biocompatibility and bioactivity. The HA coating obtained by electrophoretic deposition will result in gradient structure similar to bone structure, and biomimetic HA deposition will have an effect of bioactivity. The core material of the porous material likely composed of HA and organic polymer and other compounds will result in slowly degraded bioactive material, allowing slower dissolution followed by stepwise growth of bone tissue and angiogenesis, preventing the local inflammation processes, sustaining the mechanical strength close to that of non-porous material. P-5 Paradigms and Progress in Trauma and Orthopaedics M. Kimmons. CEO British Orthopaedic Association, UK The prevailing worldview in any organisation or culture determines not only the kinds of questions we ask but also the answers we expect. When an individual crosses from one culture to another it provides a unique, and sometimes traumatic, opportunity to both challenge and enrich the new from the perspectives of the old. The military world has clarity of purpose which is vital to not only the success of its mission but also the safety of its stakeholders. In this session a former Royal Navy Rear Admiral with 35 years of experience in the complexities of military organisation, reflects on both the benefits of his previous experience and the values that underpin his new situation. The British Orthopaedic Association (BOA) brings together a unique clinical community with academic and industrial partners in an
and macrophages are recruited within the first 24 hours after tendon injury to clean up necrotic materials and cells, and release some growth factors for the initiation of the second phase, proliferation, which starts a few days after the inflammatory phase, and lasts up to six weeks. This is the most crucial phase in connective tissue healing. The size of the local cell population is an important factor influencing the amount of proliferation in the second healing phase. However, the flexor tendon is hypovascular and hypocellular, resulting in a long-term healing process compared to other tissue healing. The most common complications following tendon repair occur during this phase. Strategies to improve tendon healing, therefore, mostly focus on in this phase, including cell-based therapy, growth factors stimulation, platelet rich plasma (PRP) augmentation, and some physical modalities. The last phase of healing, remodeling, is critical for functional tissue regeneration. During this phase, cytokines, such as MMPs, and mechanical stimulation are the most influential parameters. For flexor tendon remodeling, mechanical strength should allow muscle force transmission and also a smooth surface must be restored to enable functional performance. Intrinsic healing indicates that tissues can be directly healed by proliferation of residual cells within injured tissues, which results in superior outcomes. Intrinsic healing of flexor tendons mainly relies on the migration of epitenon cells from the tendon surface into the lacerated tendon ends since the endotenon cells have less capability to proliferate and differentiate. In contrast, extrinsic healing relies on the invasion of cells from the surrounding tissues to bridge tendons together, which leads to adhesion formation between tendon and surrounding tissues, hindering tendon gliding. However, extrinsic healing is faster and more abundant compared to intrinsic healing due to a rich blood supply and high cellularity in the surrounding soft tissues. Elimination or reduction of extrinsic healing has been investigated with the strategies of physicochemical and pharmacological interventions, but at some cost in terms of delayed or impaired tendon intrinsic healing as shown in our recent studies. Postoperative rehabilitation is also an effective therapy to decrease the adhesions formed by extrinsic healing. However, inappropriate motion therapy can also cause gap formation, and even repaired tendon rupture. Maximization of intrinsic healing and minimization of extrinsic healing still remains a great clinical and research challenge. Finally, tendon healing has two patterns of healing, i.e. contact healing and gap healing. Contact healing indicates that lacerated tendon ends directly contact each other; the tendon heals by first intention and is dominated by intrinsic healing. Most connective tissues heal by this phenomenon, such as bone, skin, and other less tensile tissues. However, the tendon, especially flexor tendon healing, primarily follows gap healing, which is similar to wound healing in the secondary intention. The function of tendon is to transmit muscle force to the bone to move joints. Tensile force always exists during joint motion, especially during postoperative rehabilitation, which is often performed to prevent adhesion formation in the early stage following tendon repair. Although lacerated tendon ends can be brought together by surgical repairs, the tensile force often causes the gap formation at the repair site. This gap healing not only elongates the healing phases, but also involves more extrinsic healing. The strategies to eliminate gap healing have been studied for many decades, including strong repair techniques, suture materials, and postoperative rehabilitation protocols, but tendon gap healing still remains an unavoidable problem. In summary, flexor tendon healing, like other connective tissues, has two physical forms (contact and gap healing) and two healing resources (intrinsic and extrinsic healing) through three healing phases (inflammation, proliferation, and remodeling). The fundamental strategies to improve the outcomes of flexor tendon injury and repair should focus primarily on achieving contact healing, secondarily on eliminating extrinsic healing, and then
S5
finally shortening the healing phases. This principle is also applicable to healing of other connective tissues. P-4 Biocompatibility and Bioactivity of Bearing Loaded Metallic Implants A. Zielinski, S. Sobieszczyk, B. Swieczko-Zurek, A. Ossowska, T. Seramak, W. Serbinski. Gdansk University of Technology, Poland The aim of the presented project is to develop the Titanium (Ti) alloy base composite materials possessing better biocompatibility, longer lifetime and bioactivity behavior for bearing loaded implants, e.g. hip joint and knee joint endoprosthesis. The development of such material will be performed through modeling the material behavior in biological environment in long time and develop new procedures for such evaluation; obtain the extremely biocompatible Ti alloy with design porosity; develop the oxidation technology resulting in high corrosion resistance and bioactivity; develop the technologies of deposition of Hydroxyapatite (HA) based composite bioactive coatings; develop the technologies of obtaining the bioactive composite core materials placed within the pores. The examinations of degradation of Ti implants are carried out in order to recognize the sources of both short allergies and inflammation, and long term degradation. The theoretical assessment of corrosion is made assuming as caused by three processes: Electrochemical dissolution through imperfections of anodic oxide layer, diffusion the metallic ions through oxides, and dissolution of oxides themselves. In order to increase the biocompatibility the toxic elements, Aluminum (Al) and Vanadium (V) are eliminated. The experiments have shown that titanium–zirconium–niobium (Ti-Zr-Nb) alloy may be such a material that can also be prepared by powder metallurgy (P/M) technique. The porous (scaffold) Ti-Zr-Nb alloy is obtained by powder metallurgy, classical and with spacing holders used before melting and decomposed, or used during melting and removed by subsequent water dissolution. The oxidation of porous materials will be performed by electrochemical technique in special electrolytes in order to obtain the oxide layers well adjacent to an interface, preventing the base metal against corrosion and bioactive because of nanotubular structure, permitting injection of antibiotics into the pores. The Calcium (Ca), Oxygen (O) and Nitrogen (N) ion implantation or deposition of Zirconia sublayers will be explored to increase the biocompatibility and bioactivity. The HA coating obtained by electrophoretic deposition will result in gradient structure similar to bone structure, and biomimetic HA deposition will have an effect of bioactivity. The core material of the porous material likely composed of HA and organic polymer and other compounds will result in slowly degraded bioactive material, allowing slower dissolution followed by stepwise growth of bone tissue and angiogenesis, preventing the local inflammation processes, sustaining the mechanical strength close to that of non-porous material. P-5 Paradigms and Progress in Trauma and Orthopaedics M. Kimmons. CEO British Orthopaedic Association, UK The prevailing worldview in any organisation or culture determines not only the kinds of questions we ask but also the answers we expect. When an individual crosses from one culture to another it provides a unique, and sometimes traumatic, opportunity to both challenge and enrich the new from the perspectives of the old. The military world has clarity of purpose which is vital to not only the success of its mission but also the safety of its stakeholders. In this session a former Royal Navy Rear Admiral with 35 years of experience in the complexities of military organisation, reflects on both the benefits of his previous experience and the values that underpin his new situation. The British Orthopaedic Association (BOA) brings together a unique clinical community with academic and industrial partners in an