Osseointegration of Orthopaedic Implants

Amirhossein Goharian

• Editorial: Academic Press
• Año: 2019
• ISBN:
  9780128133958
• Categoría: Tecnología e ingeniería
• Categoría: Ciencias biomédicas

Osseointegration of Orthopaedic Implants helps product developers at orthopedic implant manufacturers enhance the effectiveness of orthopedic implants and reduce complications, particularly in patients with osteoporotic bones. The book's expert contributors provide cutting-edge information on the latest technologies and advances available. Biomaterial researchers can use the book for basic data in the further development of orthopedic implant materials with better osseointegration. Biomechanical researchers can review related challenges and concepts of osseointegration for use in the development of implants. The book is suitable for readers from academia and industry, bridging the knowledge gap between academic based researchers, industrial based engineers, and clinical based surgeons.

• Reviews and discusses all aspects of orthopedic implant osseointegration
• Provides conceptual implants for bone fracture fixation and joint replacement
• Offers novel ideas for the development of orthopedic implants with superior osseointegration

Chapter 1

Fundamentals in Loosening and Osseointegration of Orthopedic Implants

Abstract

Various concepts and parameters have been addressed in the literature for the evaluation and assessment of integration between the bone and the implant for implantation of orthopedic implants to the bone tissue. In order to treat the severe bone injuries, losses, fractures, and even deformities, it would be inevitable to use internal implantation of orthopedic implants. Therefore the integration of bone tissue to/through the implant surface is the main concern that is currently being investigated by the researchers and product developers in the development of new generation of orthopedic implants. In this chapter, history of osseointegration concept was first reviewed, and then the effective parameters on integration of bone to the implant were discussed in view of biological and mechanobiological aspects. Poor osseointegration of orthopedic implant is associated with loosening of the implant after implantation to the bone. There would be some factors which originate from the implant that would have significant effect on osseointegration such as contact wear particles, bone loss during implantation, implant design, implant surface roughness, early mechanical integration to the cortical and trabecular bones, etc. It was observed that contact wear particles would induce expression of macrophages to phagocytosis the contact wear particles or any released particles from the implant, from which bone remodeling process is affected. Likewise, damage to the bone tissue during bone drilling and insertion of implant to the bone has been found to be effective parameter in early osseointegration. Furthermore, design feature for early mechanical integration to the bone was reported to influence the early biological integration of bone to the implant. In this chapter, the fundamentals of osseointegration in orthopedic implants and loosening of the implant are deeply reviewed. Reading of this chapter is recommended for effective pursuing of the reviewed contents in the following chapters.

Keywords

Osseointegration; Bone-implant integration; Bone-implant interface; Gene expression; Osteoblastic genes; Endosseous concept; Implant loosening

1.1 Introduction

The concept of osseointegration was first developed for dental implants to address the in-growth and on-growth of bone tissue to the surface of titanium dental implants. Gradually, this biological advantage was addressed for the development of orthopedic implants and for the evaluation of implant bioactivity aspects. In majority of implantation cases, osseointegration of implant is greatly beneficial; however, there would be some cases at which poor osseointegration is desired. Generally, better osseointegration of implant could enhance implantation of the implant to the bone, which results in better treatment of bone injuries. It has been clinically reported that poor integration of bone and implant would cause loosening of implant or even suppression of the bone to the implant.

Osseointegration is a scientific term that is going to be of a practical-scientific development concept [1–9]. The understanding of interaction between the bone and the implant has opened various fields of researches and investigations. Undesired biological response of human body after the implantation of implant was the initial side effect of internal treatment utilizing various types of materials in fabrication of implants. Therefore, the standard “ISO 10993” was developed to determine the essential biological requirements for the biological evaluation of materials aimed to be used in fabrication of implants. It would be very crucial to assure no biological effects (e.g., toxicity, cytotoxicity, sensitization, and genotoxicity) of implant materials in human body fluid and in contact with bone tissue for the development of orthopedic implants. In fact, implant must be without chemical reaction in ionized body fluid or blood if undesired release of implant materials causes biological signs or symptoms. Other factors such as low bacterial adhesion have also been highlighted to enhance biological safety or biocompatibility of the implant.

In majority of the implantations, the bonding of the implant to the bone is strongly beneficial. Indeed, good biocompatible implant without enhanced clinical benefits would not be a superior solution for the treatment of bone injuries. It has been observed that without effective bonding or integration of orthopedic implants to the bone tissue, various types of clinical complications arise postoperatively. Thus, bone-implant integration with high level of shear strength under dynamic loading conditions (which is transferred to the bone-implant interfaces) is the key factor of implant stability inside the bone and ultimately enhances clinical outcomes. Ineffective osseointegration of implant and bone may result in loosening or dislocation of the implant from the original implanted location [10–20]. Poor integration of bone and implant may occur because of various reasons. In fact, whatever would affect the bone resorption and deposition process at the bone-implant interface could cause loosening of integrity between the bone and the implant.

In this chapter, first the history of osseointegration concept is reviewed to clarify how this biological interaction could enhance the clinical results. Then various parameters that could influence the better integration of bone-implant are elaborated. Following that, the differentiation and formation of bone tissue at the bone-implant interface is discussed, then the effective expression of osteoblastic genes in promoting osseointegration is expressed. In second part of this chapter, the loosening of the implant is reviewed from various aspects. The effects of contact wear, the level of mechanical stimulation, and implant-related factors on implant loosening are discussed. Due to high risk of implant loosening in total joint replacements (TJRs), the interaction between the bone cement and the bone is deeply expressed and development concepts that could reduce the risk of implant loosening are highlighted in general.

1.2 History of Osseointegration

Osseointegration was first introduced by Professor Per-Ingvar Branemark in the 1950s as the attachment of human bone cells to the surface of metallic implants. Initially, reaction of the bone to the titanium alloy was seen in investigations carried out by Beaton and Davenport in 1940 and Gottlieb Leventhal in 1951. Through their research, potential use of titanium in orthopedic and dental implants has been addressed due to good strength, no body reaction, and growth of bone tissue on the surface of the titanium. In 1952, Per-Ingvar Branemark implanted a titanium chamber to the rabbit bone to investigate the effect of blood flow on progression of bone formation on the surface of the titanium chamber. After completion of the test, when he wanted to remove the chamber, he recognized that the chamber had integrated with bone and could not be removed easily. At that point, he discovered bone growth into the titanium chamber and good integration of bone and titanium implant. After that, he called this phenomenon "osseointegration" to be used as a material characteristic to be used in the development of implants for the better treatment of bone injuries. Later on in 1965, Branemark developed dental implant using the osseointegration ability of the titanium. Based on the description of Nishimura [5] from Branemark's definition, osseointegration is stable connecting of the bone and implant without sign of infection, inflammation, and clinical undesirable issues. Today, the concept of osseointegration is used extensively in the development of orthopedic, spine, and dental implants to promote bone in-growth and on-growth through the implant. Osseointegration may start with bone resorption at the interface of bone-implant, then formation of bone tissue on the implant surface or through in the implant body, and ultimately integration of the bone and implant at the contact surfaces.

1.3 Effective Parameters on Implant Osseointegration

Integration of orthopedic implants and bone tissue is a very complex phenomenon. Bone tissue is inherently a smart bioactive structure at which alteration of its architecture, density, size, and composition are permanently changing based on the mechanical, chemical, physical, hormonal, and stimulation signals for proliferation and differentiation. On the other hand, orthopedic implants are normally made of bioinert materials with no bioactivity characteristics. Implantation of implants with bioinert material to the bone would cause alteration of bone remodeling process at the bone-implant interface and if this abnormal bioactivity of bone tissue is continued, more depth of bone tissue at the bone-implant contact area is affected. In fact, this abnormality may increase resorption of bone tissue by osteoclast, which results in weak or no integration of bone through the implant surface. Ineffective integration of implant to the bone would affect clinical outcomes significantly. Therefore currently the topic of osseointegration is the main development concept to enhance the effectiveness of the orthopedic implants. This topic has been addressed as crucial concern to reduce the clinical complications, however, implant with high osseointegration characteristics (osseointegrant) for internal impl...