Although several major progresses have been introduced in the field of bone regenerative medicine during the years, current therapies, such as bone grafts, still have many limitations. Moreover, and in spite of the fact that material science technology has resulted in clear improvements in the field of bone substitution medicine, no adequate bone substitute has been developed and hence large bone defects/injuries still represent a major challenge for orthopaedic and reconstructive surgeons. It is in this context that TE has been emerging as a valid approach to the current therapies for bone regeneration/substitution. In contrast to classic biomaterial approach, TE is based on the understanding of tissue formation and regeneration, and aims to induce new functional tissues, rather than just to implant new spare parts. The present review pretends to give an exhaustive overview on all components needed for making bone tissue engineering a successful therapy. It begins by giving the reader a brief background on bone biology, followed by an exhaustive description of all the relevant components on bone TE, going from materials to scaffolds and from cells to tissue engineering strategies, that will lead to "engineered" bone. Scaffolds processed by using a methodology based on extrusion with blowing agents.

/pdf/bone-tissue-engineering-state-of-the-art-and-future-trends-4x410y8eni.pdf

Bone Tissue Engineering: State of the Art and Future Trends

OBJECTIVE: To describe the functional anatomy of the ankle complex as it relates to lateral ankle instability and to describe the pathomechanics and pathophysiology of acute lateral ankle sprains and chronic ankle instability. DATA SOURCES: I searched MEDLINE (1985-2001) and CINAHL (1982-2001) using the key words ankle sprain and ankle instability. DATA SYNTHESIS: Lateral ankle sprains are among the most common injuries incurred during sports participation. The ankle functions as a complex with contributions from the talocrural, subtalar, and inferior tibiofibular joints. Each of these joints must be considered in the pathomechanics and pathophysiology of lateral ankle sprains and chronic ankle instability. Lateral ankle sprains typically occur when the rearfoot undergoes excessive supination on an externally rotated lower leg. Recurrent ankle sprain is extremely common; in fact, the most common predisposition to suffering a sprain is the history of having suffered a previous ankle sprain. Chronic ankle instability may be due to mechanical instability, functional instability, or most likely, a combination of these 2 phenomena. Mechanical instability may be due to specific insufficiencies such as pathologic laxity, arthrokinematic changes, synovial irritation, or degenerative changes. Functional instability is caused by insufficiencies in proprioception and neuromuscular control. CONCLUSIONS/RECOMMENDATIONS: Lateral ankle sprains are often inadequately treated, resulting in frequent recurrence of ankle sprains. Appreciation of the complex anatomy and mechanics of the ankle joint and the pathomechanics and pathophysiology related to acute and chronic ankle instability is integral to the process of effectively evaluating and treating ankle injuries.

Functional Anatomy, Pathomechanics, and Pathophysiology of Lateral Ankle Instability.

The clinical use of plasma-sprayed hydroxyapatite (HA) coatings on metal implants has aroused as many controversies as interests over the last decade. Although faster and stronger fixation and more bone growth have been revealed, the performance of HA-coated implants has been doubted. This article will initially address the fundamentals of the material selection, design, and processing of the HA coating and show how the coating microstructure and properties can be a good predictor of the expected behavior in the body. Further discussion will clarify the major concerns with the clinical use of HA coatings and introduce a comprehensive review concerning the outcomes experienced with respect to clinical practice over the past 5 years. A reflection on the results indicates that HA coatings can promote earlier and stronger fixation but exhibit a durability that can be related to the coating quality. Specific relationships between coating quality and clinical performance are being established as characterization methods disclose more information about the coating.

Material fundamentals and clinical performance of plasma-sprayed hydroxyapatite coatings: A review

•: Growth factors (bone morphogenetic protein, transforming growth factor-beta, fibroblast growth factor, platelet-derived growth factor, and insulin-like growth factor) are proteins secreted by cells that act on the appropriate target cell or cells to carry out a specific action.

•: Because growth factors are expressed during different phases of fracture-healing, it has been thought that they may serve as potential therapeutic agents to enhance bone repair.

•: The selection of an appropriate carrier or delivery system for a particular growth factor is essential in order to induce a specific biologic effect.

•: There are a number of potential clinical applications for growth factors in the enhancement of bone repair, including acceleration of fracture-healing, treatment of established nonunions, enhancement of primary spinal fusion or treatment of established pseudarthrosis of the spine, and as one element of a comprehensive tissue-engineering strategy that could include gene therapy to treat large bone-loss problems.

Growth factors are proteins that serve as signaling agents for cells. They function as part of a vast cellular communications network that influences such critical functions as cell division, matrix synthesis, and tissue differentiation. The results of experimental studies have established that growth factors play an important role in bone and cartilage formation, fracture-healing, and the repair of other musculoskeletal tissues. Recently, with the advent of recombinant proteins, there has been considerable interest in the use of growth factors as therapeutic agents in the treatment of skeletal injuries. As growth factors become available as therapeutic agents, it is essential that orthopaedic surgeons understand their biological characteristics and clinical potential. The purpose of this review is to define the mechanisms of action, functions, and potential clinical applications of a variety of growth factors that may be used clinically to treat problems associated with the repair of bone.

Growth factors are proteins secreted …

The role of growth factors in the repair of bone. Biology and clinical applications.

Background:Bone morphogenic proteins (BMPs) are known to promote osteogenesis, and clinical trials are currently underway to evaluate the ability of certain BMPs to promote fracture-healing and spinal fusion. The optimal BMPs to be used in different clinical applications have not been elucidated, an

Osteogenic activity of the fourteen types of human bone morphogenetic proteins (bmps)

The ability of exogenous Transforming Growth Fac- densitometry. Increased maximal bending strength tor4 (TGF-D) to stimulate bone formation in fracture and callus formation were demonstrated in the healing was investigated. TGF-O was continuously groups receiving TGF-O. TGF-D had no effect on applied in doses of 1 and 10 pg/day for 6 weeks to 2 bending-stiffness, bone mineral content, cortical groups of adult rabbits with unilateral plated midtibial thickness or haversian canal diameter. We conclude osteotomies. A group receiving solvent without TGF- that local application of exogenous TGF-O may O served as control. Fracture healing was evaluated enhance fracture healing in rabbits. by mechanical tests, bone morphometry and bone

https://www.tandfonline.com/doi/pdf/10.3109/17453679308993691

Transforming growth factor-β enhances fracture healing in rabbit tibiae

In vivo study of the effect of RGD treatment on bone ongrowth on press-fit titanium alloy implants

Background Approximately 12,000 hip and knee replacements were performed in Denmark in 2005. Accelerated perioperative interventions are currently implemented, but there is conflicting evidence regarding the effect. We therefore performed an efficacy study of an accelerated perioperative care and rehabilitation intervention in patients receiving primary total hip replacement, and both total and unicompartmental knee replacement.Methods A randomized clinical trial was undertaken in which 87 patients were randomized to either a control group receiving the current perioperative procedure, or an intervention group receiving a new accelerated perioperative care and rehabilitation procedure. Outcome measures were length of stay (LOS) in hospital, and gain in quality of life (QOL) using EQ-5D from baseline to 3-month follow-up.Results Mean LOS was reduced (p < 0.001) from 8 days (95% CI: 7.1–8.4) in the control group to 5 days (95% CI: 4.2–5.6) in the intervention group. This was accompanied by a greater gain in...

https://www.tandfonline.com/doi/pdf/10.1080/17453670710014923

Accelerated perioperative care and rehabilitation intervention for hip and knee replacement is effective: A randomized clinical trial involving 87 patients with 3 months of follow-up

During prosthetic implantation, gaps between the implant surface and the surrounding bone may occur resulting in reduced implant stability. In these instances bone-conductive materials might augment the formation of hosting bone into the pores of the implant and insure earlier implant stabilization and fixation by bony ingrowth. Titanium-alloy cylinders with a porous-titanium-alloy plasma spray coating were implanted into the medial femoral condyles in six mature dogs. In another group of six dogs, matched in age, weight, and gender, hydroxyapatite (HA) coated implants were used. All implants were surrounded by a 1-mm gap. Unilateral osteopenia of the knee, with a 20% reduction of bone density as judged by computed tomography scanning, was induced by 12 weekly intraarticular injections of carrageenin into the right knee before surgery. Four weeks after implantation, the HA-coated implants were compared to the parent porous-titanium implants by mechanical testing and histomorphometry. A marked positive influence of HA coating on bone mineralization and the strength of the interfacial bone between the bone and implant was found. The increment in interface shear strength and shear stiffness was three- to fivefold in osteopenic bone and two-fold in control bone. Coating of an unloaded porous-titanium-coated implant with HA accelerates the rate of bone ingrowth and thereby provides relatively high, early interfacial shear strengths in the presence of an initial gap between bone and implant even in the presence of osteopenic host bone.

Gap healing enhanced by hydroxyapatite coating in dogs.

Three-plane kinesiology of hindfoot instability was studied after lesions to the ligamentous structures in the sinus and canalis tarsi in 20 amputation specimens. Neither a lesion of the cervical ligament nor of the interosseous talocalcaneal ligament resulted in an increase in the total range of movements above 2.6 degrees in any of the three planes. However, the percentage increase in the total range of movements after cutting of the ligaments was generally largest in the talocalcaneal joint compared to the increase in the total hindfoot joint complex. The largest percentage increase (43%) in the talocalcaneal joint occurred at dorsiflexion after cutting the interosseous talocalcaneal ligament. The demonstrated minor instability after experimental lesions of the ligamentous structures in the sinus and canalis tarsi may have a clinical identity in the sinus tarsi syndrome. Patients with that syndrome rarely present an objective hindfoot instability, although a major complaint is a feeling of hindfoot instability.

Kjeld Søballe

Papers

Transforming growth factor-β enhances fracture healing in rabbit tibiae

In vivo study of the effect of RGD treatment on bone ongrowth on press-fit titanium alloy implants

Accelerated perioperative care and rehabilitation intervention for hip and knee replacement is effective: A randomized clinical trial involving 87 patients with 3 months of follow-up

Gap healing enhanced by hydroxyapatite coating in dogs.

The stabilizing effect of the ligamentous structures in the sinus and canalis tarsi on movements in the hindfoot An experimental study