Development of Novel Orthopaedic Materials

Abstract

New materials have played a critical role in Orthopaedic for many decades. Early total joints and trauma devices were made from stainless steel then titanium and cobalt-chrome replaced stainless steel in most modern implants. In addition to high-strength structural metals, polymers such as polyethylene were used for many decades in total joints followed by polyether-ether-ketone (PEEK) in spine fusion and then in sports medicine anchors. Biodegradable polymers have also made a strong impact with their beginnings in degradable sutures and current widespread use as an anchoring material in sports medicine reconstructions. This issue covers recent material developments in multiple areas of Orthopaedic surgery, such as soft-tissue fixation, hip arthroplasty, spine fusion, and wound healing. As the title suggests, orthopaedic materials may come from two avenues, emerging into the field or evolving within the field of orthopaedic surgery. Emerging materials may have a long history in other fields of medicine, but are experiencing a transition into orthopaedic use. In contrast, evolving materials have an established history in the field of orthopaedic materials, but they are being processed in new ways to gain additional functionalities. This issue will explore both of these approaches and discuss how financial and regulatory burdens affect material technology development. A recent special issue has focused on the 3-dimensional printing of materials for orthopaedics so we will not discuss that innovation here. Dr Elsner and Dr McKeon have provided a thorough review on the use of polycarbonate urethanes, a material emerging from the cardiovascular field due to its enhanced oxidative stability compared with prior polyurethanes. Regarding orthopedic use, polycarbonate urethanes show a much softer response and less wear compared with ultra-high molecular weight polyethylene, thus this material is potentially replacing bearing surfaces in hip arthroplasty and being trialed as a meniscus replacement. This review covers the full spectrum of material development from in vitro biomechanics to animal testing to clinical outcomes. Dr Smith and colleagues describe the use of shape-memory polymers for soft-tissue fixation. The concept and use of shape-memory polymers has seen a long history since the 1960s as heat-shrink tubing, but only recently have they emerged into the Orthopaedic field due to advances in activation mechanisms. The principles of both shape-memory polymers and soft-tissue fixation mechanics are discussed as well as the advantages of these expandable devices. In addition, Dr Higgs gives an in-depth explanation of how to use shape-memory polymer devices for posterior lateral corner reconstruction, which greatly simplifies the procedure. Dr Lei and colleagues have written a comprehensive review on the use of dehydrated human amnion/chorion membranes allograft for healing Orthopaedic soft-tissues. Although amniotic membranes have been used for wound healing and skin grafting since the early 20th century, it is the refinement of processing methods and continued expansion into more Orthopaedic applications that drives the use of this regenerative technology. This review covers the relevant biological markers and components of these allografts along with a myriad of clinical uses, including rotator cuff repair, anterior cruciate ligament reconstruction, Achilles tendinopathy, plantar fasciitis, and even transforaminal lumbar interbody fusion. Torstrick and colleagues discuss the development of a porous PEEK interbody fusion device. PEEK interbody fusion devices have a history of producing a fibrous tissue response due to their smooth surface, but porous PEEK challenges this paradigm with its 3-dimensional topography that allows for osseointegration. Although the effect of chemical structure and topography on osseointegration is a current debate, this porous PEEK serves as an example of how altering topography can change the biological response to a well-known material. Dr Burkus and Dr Chappuis present clinical examples of their experience where the porous PEEK interbody fusion device was used for anterior cervical discectomy and fusion. Dr Bariteau and colleagues give a detailed review of the ethical, financial, and regulatory issues to be considered when developing a new orthopedic technology. The need for new technology is illustrated by the development of total hip arthroplasty devices throughout the 20th century. Innovation is necessary for improving patient care, and it must be done in the face of steep research and development costs and significant regulatory requirements. In addition, total ankle replacements are given as an example of recent technology development in the foot and ankle market. Finally, we would like to thank all of the authors for their time and contributions to this symposium.