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Orchid Blog

Orthopedic Implant Coatings: Current State and a Look into the Future

Posted: Monday, March 04, 2019

Coatings applied onto surfaces of implants have been a mainstay of the medical device industry for a few decades. Coatings serve a number of functions, ranging from enhanced tissue integration with the host, to improved bearing wear performance, and local delivery of therapeutic agents. Orchid remains at the forefront of delivering clinically proven implant coatings to our OEM customers, who are striving to innovate newer technologies for the unmet and anticipated future needs.

CLINICALLY PROVEN ORTHOPEDIC IMPLANT COATINGS

Porous Coating of bone contacting surfaces of orthopedic implants is the gold-standard for implant fixation, with long clinical history of effectiveness and safety. The concept is simple; a coating of porous material is applied onto the specified tissue contacting surfaces. Upon implantation bone tissue grows onto and infiltrates the voids of the porous structure, thereby achieving long-term mechanical stability.

Porous coatings of various types have been in clinical use for titanium and CoCr orthopedics implants since the 1970s. The technology has evolved to a mature state over the last ten years. Maturity of this coating technology notwithstanding, the challenges to bring innovative implant designs and systems to the market remain; namely the regulatory requirements to demonstrate that the coating meets very tightly prescribed technical specifications; (i) manufactured from nominally biocompatible materials, (ii) robust attachment to the implant substrate in order to survive the forces applied during surgical implantation, and (iii) pore characteristics amenable for the biological processes that ultimately lead to bony attachment.

Bone Conductive Coatings, such as hydroxyl apatite (HA), as a stand-alone coating or an adjunct to metallic porous coating remain an attractive technical solution to further enhance tissue integration of long-term stability.

Orchid has state-of-the-art facilities that provide metallic porous coatings (both sintered and plasma sprayed) and plasma sprayed HA coatings to customers world-wide. Our highly qualified engineering, innovation, production, and quality teams work hand-in-hand with established and new customers to facilitate regulatory clearance, including work to generate engineering studies, create technical dossiers, process validations, and in rare instances they interact with the FDA to address questions.

The medical device industry is undergoing rapid changes; including integration of 3D layer-by-layer manufacturing technologies, such as electron beam melting and selective laser sintering. The value propositions of these new technologies to deliver the same results as cost-effectively as mature technologies remains a challenge. However, the technologies are driving rapidly to satisfy needs currently unmet by traditional technologies.

THE FUTURE OF ORTHOPEDIC IMPLANT COATINGS

Bearing surface ceramic coatings have the potential to further improve the longevity of articulating implant systems such as hip, knee, and shoulder replacements. Innovation in this area is driven by the need for ultra-high hardness counter-bearing surfaces which articulate against itself or against soft ultrahigh molecular weight polyethylene.

The current standard-of-care counter-bearing material, CoCr alloy, has been utilized for more than 40 years. More recently, as implants are lasting longer in patients, clinicians and researchers are observing that CoCr may not be the most ideal candidate for some patients. The alloy components in CoCr, including cobalt, chromium, molybdenum, and potentially nickel, are not the most bio-compatible and some patients are sensitive to these elements.

Alternative solutions remain relatively elusive because the elements that are considered the most biocompatible (and inert in the body) are also too soft for counter-bearing application. On the other hand, ultra-hard and inert ceramic materials such as alumina and stabilized zirconia are prone to fracture due to the inherent low fracture toughness of ceramics. Orchid is actively developing technologies to address these concerns.

Implant infection (whether acquired through systemic bacteria or nosocomial at the time of surgery) remains a vexing unsolved problem in implantology. Antimicrobial coatings, to help with reduction in early post-op infections, are promising avenues for innovation; notwithstanding the technical and clinical challenges to demonstrate safety and effectiveness. However, the regulatory barriers for antimicrobial coatings are daunting.

The orthopedic coating market is primed for growth. Orchid has the expertise in facilitating and helping to meet the challenge of implant fixation and is actively developing technologies for the anticipated future needs of the market.


By Shilesh Jani, Engineering Manager