Surface modifications and coatings enhance the functionality and longevity of orthopedic implants and other medical devices. A growing focus in orthopedics is creating implants that offer better properties for greater functionality and improved osseointegration. “The aim is to improve healing and accelerate recovery for patients,” said Ulf Brogren, chief commercial officer for Promimic, a provider of nanoengineered bioactive coatings for implants with headquarters in Gothenburg, Sweden, and a manufacturing operation in Austin, Texas. “With demographic shifts and an aging population, this has become increasingly important to ensure successful clinical outcomes for this segment of the market.”

A major goal for implant manufacturers is improving osseointegration—the connection between bone and implant—”by utilizing bioactive materials such as hydroxyapatite coatings and biocompatible metals, including titanium,” said Francesco Bucciotti, head of global business and business development for Lincotek Medical, a global solution provider for medical device manufacturers.

Advanced depositional methods such as plasma spraying, physical vapor deposition, and chemical vapor deposition are popular methods for integrating surface materials into the implant. Recent developments in surface technology target multifunctional coatings that address multiple performance aspects simultaneously. These include improved wear resistance, antibacterial properties, and the controlled release of bioactive factors that aid in faster recovery and reduced infection risks. “The exploration of such technologies reflects the strong, ongoing demand for innovative surface treatments that can offer increasing performance and product differentiation in an increasingly consolidated and competitive market,” said Bucciotti.

These and other methods such as atmospheric plasma spraying, vacuum plasma spraying, and controlled atmosphere plasma spraying that work so well on machined components and implants are more problematic for those made with additive manufacturing (AM) because the coating material can be too thick and occlude the porosity built into the part. Therefore, considerable R&D is being spent to improve chemistry and application methods for AM parts that will not clog the porosity that is so vital for osseointegration. 

Recent Trends

One of the most popular surface treatments is electropolishing—a critical finishing process for the orthopedic industry that improves surface finish and overall product performance. Electropolishing boosts manufacturing efficiency, enhances product durability, makes parts easier to clean and sterilize, and increases corrosion resistance. Tiny (±0.0002 inches) surface defects and contaminants left behind by the machining process can be easily eliminated with microscopic precision, leaving critical metal parts free of microburrs, microcracks, and other defects, while enhancing durability and corrosion resistance.

“Most ortho companies think only stainless steel can be electropolished and are surprised to discover that nearly any metal alloy, with the exception of precious metals, can be electropolished,” said Scott Potter, vice president of sales for Able Electropolishing Company, a Chicago, Ill.-based provider of electropolishing, nitric and citric passivation, vacuum vapor degreasing, passivation verification testing, and surface analysis services for medical device manufacturers. “Right now, the hottest items for electropolishing are titanium and nitinol implants, bone screws and plates, and staples. After COVID, the resurgence in voluntary surgeries, fueled by the aging population, has resulted in a steady amount of work in the orthopedic space.” 

Overall, the electropolishing market is projected to experience an annual growth rate of 7.1% from 2024 to 2031.¹ Advancements driving this trend include improved aesthetics, minimized risk of contamination, decreased friction, and increased durability. These properties make electropolishing an important finishing technology in the medical, automotive, aerospace, and electronics industries.

New or improved bioreactive coatings that enhance osseointegration are always in high demand, especially for spinal implants. Promimic, for example, has developed a state-of-the-art nanotechnology that mimics nature, making it possible to create a bioactive surface for any implant. Its HA^nano Surface coating is a 20-nanometer-thin implant surface composed of crystalline hydroxyapatite (HA) particles. These particles have the same shape, composition, and structure as HA found in human bone. HA^nano Surface is 1,000 times thinner than traditional HA coatings and can be applied to nearly all implantable materials, creating a super hydrophilic surface that improves osseointegration of the implant.

Implants are dipped in the HA^nano Surface solution and, after spinning and heat treatment, all materials are removed except for the HA crystals. “This approach can be combined with other techniques such as anodization, acid etching, laser treatment, and 3D-printed surfaces, without clogging the porous structure,” said Brogren. “We also see an increased demand for biomimicking coating of softer polymers used in sports medicine.” 

A significant trend in orthopedics is the focus on infection management in joint prosthetics, which is a critical need due to persistent infection rates, particularly prosthetic joint infections (PJIs). Although PJIs affect only 1-2% of hip and knee replacements (higher rates in revision, trauma, and tumor cases), they still impose notable financial strains on both patients and healthcare systems. “The need for infection management is driving advancements in both preventative and therapeutic solutions, including biofilm-resistant materials, advanced antibiotic coatings, and protocols such as debridement, antibiotics, and implant retention, which aid in reducing recovery times and improving patient outcomes,” said Bucciotti. “The rise of antibiotic-resistant strains, such as Staphylococcus aureus, also intensifies this need, driving interest in glycopeptide antibiotics and biofilm-targeted treatments.”

While HA coatings are still very popular, a slight decline in their usage is expected as the market shifts toward alternative bioactive coatings. For example, Lincotek Medical offers nano calcium phosphate coatings that also prevent clogging of porous structures and accelerate osseointegration, ensuring superior performance, especially during the early stages after surgery. The company also provides nano calcium phosphate coatings specifically designed for application on polyetheretherketone (PEEK), a material increasingly valued in spinal applications for its radiolucency and compatibility with bone tissue.

Also, because of health issues related to the shedding of ions from cobalt-chromium (Co-Cr) alloys commonly used in knee implants, the coatings industry is exploring advanced coatings as alternative solutions—for example, multilayer materials that improve wear resistance and significantly reduce ion release, thus enhancing implant biocompatibility. “These advanced coatings also incorporate elements that support bone integration and minimize allergic responses through encapsulation techniques that isolate Co-Cr surfaces when necessary,” said Bucciotti. 

What OEMs Want

OEMs seek surface treatments that are qualified, validated, and compliant with regulatory standards. In addition, they want these coatings to streamline market approvals across multiple regions. “Companies want to work with vendors that can provide electropolishing and passivation and are ISO 13485 certified,” said Potter.

Ortho companies are intently focused on achieving specific properties that enhance both the functional performance and aesthetic appeal of implants. “Popular requests right now are mirror-like finishes with lower micro finishes,” said Potter. They also count on their surface-treatment partners to provide expert advice on how to achieve multiple critical characteristics such as: 

• Porosity—Porous coatings are “highly valued for their ability to promote bone ingrowth and ensure stable mechanical fixation,” said Bucciotti. “The porosity of the coating supports osseointegration, providing a foundation for long-term implant stability and durability.”
• Adhesion—Strong adhesion between the coating and the implant surface is crucial for longevity and effectiveness. Medical device companies (MDMs) prioritize coatings that maintain robust adhesion, even under mechanical stress.
• Roughness—Surface roughness can be customized to optimize the biological response as a controlled roughness level aids in the attachment of bone cells and enhances overall osseointegration. This property is finely balanced to promote cellular attachment without compromising the implant’s structural integrity or
  mechanical function.
• Wear resistance—Wear-resistant coatings contribute to the implant’s longevity by minimizing surface degradation due to mechanical friction. Enhanced wear resistance is especially critical for load-bearing implants, where coatings designed to reduce wear can significantly extend the device’s lifespan and decrease revision rates.
• Bacteriostatic properties—Coatings with bacteriostatic properties help inhibit bacterial colonization, which reduces the risk of post-operative infections. “By integrating bacteriostatic agents or materials that create a less-favorable environment for bacterial growth, these coatings help improve patient outcomes by lowering infection risks,” said Bucciotti.
• Appearance and color—The appearance and color of coatings can aid in implant identification and enhance aesthetic appeal. Consistent coloration and finish provide visual cues that simplify handling and placement during surgery, improving operational efficiency.

Combined, these properties allow MDMs to deliver implants that are not only biocompatible and structurally sound but also optimized for wear resistance and infection control. By meeting both the functional and practical standards of modern orthopedic applications, these highly engineered coatings play an essential role in advancing implant performance and patient outcomes.

It is more challenging, however, to create these properties in complex, AM-made products. In many cases, traditional plasma-sprayed coatings do not work because they block the porosity of the implant material. Therefore, orthopedic manufacturers are keenly interested in integrating 3D-printed porous structures with advanced surface treatments that do maintain porosity, such as Promimic’s HA^nano Surface and Lincotek Medical’s nano calcium phosphate coatings. The porosity supports bone ingrowth and mechanical stability, while the coatings accelerate the biological bonding process—together, these two capabilities meet the growing demand for implants that promote faster recovery, better stability, and long-term durability.

Other Surface Technologies

The main types of surface modifications in orthopedics address key performance aspects of implants, particularly osseointegration, wear resistance, and antibacterial properties. For example, anodization enhances not only the strength and corrosion resistance of an implant but also provides aesthetic benefits that improve the efficiency of surgical procedures. Lincotek has developed specialized anodization treatments for 3D-printed titanium porous structures. These treatments provide all the typical anodization properties while leaving no residues, thus preserving the integrity of interconnected porous structures in 3D-printed implants.

Another important coating for wear resistance is diamond-like carbon (DLC), “an innovative multi-purpose coating that utilizes two key chemical properties of carbon—the typical hardness of diamond and the ease of sliding of graphite,” said Gianmarco Lualdi, head of sales for HPF Group, a Udine, Italy-based provider of titanium applications, including hot forging and heat treatments. “Thanks to this combination of outstanding properties, DLC is the high-tech carbon-based coating with the widest spectrum of use.”

There is a growing number of multifunctional coatings and surface treatments that contribute to improved patient outcomes by reducing post-surgery infections. Lincotek Medical’s Osprolife is a resorbable form of calcium phosphate made from brushite that is applied as a 20-micron-thick coating and dissolves within a few weeks of implantation. “Brushite chemistry can be doped with antibacterial agents,” said Bucciotti. “This approach avoids many of the concerns, such as toxicity and development of resistant bacteria associated with long-term exposure to antibacterial doping agents. Also, both the external and internal surfaces of AM structures can be coated with brushite without filling the pores, providing a bioactive layer that enhances product performance.” 

NanoLaze was developed by Precision Coating, a New England- and Costa Rica-based provider of high-tolerance coating and surface modification technologies to the medical device industry. The technology uses high-frequency, low-temperature pulse lasers to create custom textures that improve the osseointegration and antimicrobial properties of an implant. The five-axis interchangeable laser configuration enables texturing on contoured surfaces and complex geometries with a single setup. “We collaborate with our customers to create custom textures to help achieve the desired results,” said Mike Gianfrancesco, vice president of engineering and technology for Precision Coating.

Peak Coating utilizes silver nanoparticles in its Ag360 coating to create antimicrobial properties. This material can be applied to a variety of substrates, including polyethylene terephthalate (PET), silicone, PEEK, stainless steel, cobalt-chromium, and titanium, providing a broad spectrum of antibacterial protection with low elution profiles. Common applications are orthopedic implants, fixation devices, and vascular grafts. 

TiShield is a Lincotek Medical antibacterial coating that also uses nanosilver particles. Unlike traditional silver coatings that rely primarily on ion release for antimicrobial effects, TiShield utilizes the nanoparticle itself to prevent bacterial adhesion. Nanometric silver particles are deposited within the AM lattice network, leveraging their antimicrobial properties without altering the structure’s integrity. Due to their nanoscale size and shape, these particles penetrate bacterial membranes directly, effectively killing a wide range of pathogens and minimizing the risk of implant-associated infections. This targeted mechanism of action not only enhances antibacterial efficacy but also supports the longevity of the implant surface by reducing bacterial colonization. 

Orthobond Corporation, based in Monmouth Junction, N.J., has developed a way to covalently bond its antibacterial molecule to implant surfaces. Using advanced covalent linker technology, the Ostaguard treatment delivers effective antimicrobial protection directly on the device’s surface, including those used in joint reconstruction, neuromodulation, oncology, sports medicine, plastic surgery, and cardiovascular procedures. The technology is integrated during the manufacturing phase and not applied as a secondary operation. The FDA has approved the De Novo marketing request for Ostaguard for use on permanent medical devices, making it the first FDA-approved non-eluting coating that actively kills bacteria on a medical device surface. 

Regulatory Considerations

The FDA recently issued a draft guidance document titled, “Characterization of Metallic Coatings and/or Calcium Phosphate Coatings on Orthopedic Devices,” which updates earlier guidelines from 1995 and 2000 on HA coatings and plasma-sprayed metallic coatings. Once finalized, the document will provide recommendations for orthopedic device manufacturers that submit devices with metallic, calcium phosphate, or dual coatings to the FDA for premarket review. 

The guidance now regulates dual-layer coatings more explicitly, addressing areas that may have previously been ambiguous. The draft indicates that testing evidence will be required for both single-layer and dual-layer coatings, which could increase the overall testing burden. Notably, the solubility requirement for HA coatings has been removed, simplifying that aspect of the testing process.

Other types of coatings, such as calcium-based coatings, are not covered in the document. The draft does include advice regarding sterility, coating descriptions, sterilization, biocompatibility testing, and shelf life and packaging. It also offers recommendations for non-clinical bench testing for device coating, such as coating chemical analysis. 

“We reviewed the draft and did not identify any ASTM or ISO testing requirements that are unfamiliar or beyond our current internal and/or external testing capabilities,” said Bucciotti. “However, one aspect that requires further clarification is the testing of titanium coating aging. While aging tests have long been a requirement for HA coatings, the draft suggests that similar evidence may now be required for titanium coatings, despite the well-established durability of metallic elements like titanium.”

The final release date for the official document has not yet been announced.

Moving Forward

New methods and materials continue to enter the market, with a strong focus on multifunctional coatings for implants. R&D is being invested in developing customized coatings based on individual patient profiles. AM is being advanced to create intricate coatings that perfectly fit an implant’s surface, improving functionality and longevity. MDMs also want smart coatings that can monitor an implant’s condition and relay that data in real-time to detect potential issues, before they become more serious problems.

For example, researchers at the University of Illinois Urbana-Champaign have developed smart coatings for orthopedic implants that have bacteria-killing nanopillars on one side and flexible electronics on the other side that monitor strain—providing an “early warning” system that can identify preliminary signs of failure while preventing infection. Inspired by insect wings, the pillars puncture the cell walls of bacteria trying to attach to the implant. The arrays of highly sensitive, flexible electronic sensors can help doctors track healing progress in patients and repair or replace devices before they fail.²

Advancements in coatings are not just about new chemistries—it is also about coming up with better ways to administer coatings. Leaders in this field such as Lincotek are at the forefront of plasma spray research and have developed new solutions and proprietary equipment tailored for optimized coating applications. These engineers are devoted to the design and development of specialized systems that integrate the latest technological advancements across all coating processes. R&D teams prioritize innovation with a clear focus on reducing infection risks and improving the patient experience. For example, Lincotek Medical’s TiGrowth—a unique titanium foam that can be sprayed onto a variety of medical devices, such as femoral stems and acetabular cups—could not have been developed without Lincotek Medical’s proprietary technologies for plasma spray processes.

“Our product development teams are constantly advancing the technology behind the HA^nano Surface,” added Brogren. “Over the past year, we have developed new techniques to deposit HA crystals at lower temperatures, opening new opportunities for heat-sensitive substrates like polymers.”

In addition, Lincotek has become the first company to submit an FDA Master File for titanium plasma spray coatings on PEEK. PEEK is increasingly preferred in spinal applications due to its radiolucency and biocompatibility with bone tissue and coatings. These new coatings are specifically optimized for this material. The combination of titanium plasma spray and nano calcium phosphate coating on PEEK enhances mechanical stability and osseointegration and broadens the scope of customized solutions available for complex orthopedic applications. 

Ultimately, the balance between clinical efficiency and cost effectiveness plays perhaps the largest role in the adoption of cutting-edge surface modifications and coatings. Therefore, the challenge lies in driving innovations that meet clinical demands, such as reducing infection risks or enhancing osseointegration, while remaining accessible within existing healthcare frameworks. 

“This dual focus requires collaboration among OEMs, healthcare providers, and regulatory bodies to ensure that impactful coating and surface modification technologies reach the patients who can benefit most, without introducing unsustainable costs,” said Bucciotti.

References

¹ tinyurl.com/odt241131

² tinyurl.com/odt241132

Mark Crawford is a full-time freelance business and marketing/communications writer based in Corrales, N.M. His clients range from startups to global manufacturing leaders. He has written for MPO and ODT magazines for more than 15 years and is the author of five books.