Just Scratching the Surface

Growth in orthopedics leads to new opportunities and challenges for coating and finishing providers

Ed Kensik

It’s not exactly news that implants have become a mainstay in orthopedics over the years. The demographics of the recipients have been shifting, however, sparking a different set of needs for a newer subset of patients. It’s clear that orthopedic OEMs are looking beyond the traditional elderly candidate as a recipient for their next-generation implants. This fall, Biomet launched an educational campaign featuring former Olympic gymnast Mary Lou Retton, who had a hip replacement
in June 2005. Using celebrities to promote a cause is nothing new in orthopedics—actress Angela Lansbury, now 81 years of age, acted as a spokesperson for DePuy Orthopaedics earlier this year, discussing her knee replacement. The difference with Retton is that she’s only 38.

The photograph shows a porous section of a femoral stem coated with Spire’s IonTite hydroxyapatite material for enhanced bone ingrowth. Photo courtesy of Spire Biomedical.

While many advances in the implant category have made more patients willing to undergo the surgery in an attempt to get back to a more active life, the unfortunate reality is that younger generations receiving these joint replacements often have been faced with the knowledge that their implant most likely would not outlive them and would need to be replaced. In fact, the average lifespan of a reconstructive joint implant is 10 to 20 years, after which a revision procedure usually must be performed. However, strides are being made to counter this need.

Coatings and finishes play a key role in increasing component durability and reducing the need for repeat surgeries. For orthopedic implants, coatings provide a wear-resistant surface in conjunction with other substrate materials. In addition, coatings can improve the performance of a product by lowering frictional forces between the tissue and device or enhancing the ability to withstand mechanical failure of a device surface. Finishes can help extend the life of the implant by protecting against abrasion and corrosion.

According to a 2005 Frost & Sullivan report, titled Advances in Coatings Technology for Medical Devices and Drug Delivery (Technical Insights), “surface modification has barely penetrated this major market. Improved surfaces would ensure orthopedic implants become more wear resistant, and promote new tissue growth or cellular adhesion, for better healing.”    

As younger generations replace their stressed joints, they want to know they won’t have to revisit the operating room time and again for a revision. “If I am getting a knee implant, I would want it to last my whole lifetime,” said Ray Harris, sales manager of Electrolizing Corporation of OHIO, a coatings and finishing provider based in Cleveland. “One [of the goals] is to get the coating and finishing to extend the life of the implant as long as possible.”    

To meet the demands of a growing market, contract service providers are working overtime to discover and evaluate new coatings and finishes, along with processes for incorporating them into orthopedic products. “Our R&D department is constantly looking for new technologies,” Harris added.    

Providers such as Electrolizing Corp. are attempting to meet the growing demands of their OEM
customers, who are looking to their coating and finishing providers for durability, safety and biocompatibility. After all, as the Frost & Sullivan report indicates, greater biocompatibility offered by a coating means fewer infections and systemic reactions, which often can necessitate costly treatment and extended hospital stays.     
    

A Look at Finishing Processes

According to Jean-Paul Burtin, vice president of marketing and sales of Wilmington, MA-based Tecomet, part of the safety equation involves the need for an orthopedic implant to have a quality surface finish.

“High quality polishing is very important for articulating surfaces like a knee femoral component,” he said. “It is also required for certain cemented hip stems.”    

Harris agrees with Burtin about the articulating surfaces. “Something like that would have to be ultra smooth…it would have to be highly polished,” said Harris. “If there’s any surface roughness, it would not attach properly.”

In orthopedics, certain finishing processes tend to be used more often than not across the implant spectrum.

For example, laser marking is used to etch serial or tray numbers and even graphics on the implant. These markings are permanent and non-toxic, as well as non-intrusive and free from corrosion mechanisms, according to Electrox, a laser marking service provider based in Letchworth, United Kingdom.

Passivation, on the other hand, is much more than an aesthetic process. This finishing process uses nitric acid to remove surface contamination, which removes the “free iron” left on the surface of stainless steel after a part has gone through machining and fabrication. Passivation adds a protective film, providing optimum corrosion resistance, according to Robert Mills, director of sales and marketing for Natick, MA-based Duralectra, a finishing provider.

Samples of Tecotex computer-generated, photo-etched, 3D surface textures from Tecomet are shown. Photo courtesy of Tecomet.

For implants, the finishing process also includes a cleaning stage, which usually involves sterilization. However, when you hear someone refer to the “cleaning” process in terms of finish, it also can pertain to other functions, depending on at what step the implant is in the manufacturing process.    

One other commonly used process is anodization. This process entails coating a metallic surface electrolytically with a protective or decorative oxide. For example, coating aluminum by anodic treatment can result in a thin film of aluminum oxide of extreme hardness with the possibility of a wide variety of dye-colored coatings.

Mills said that consistency of the anodizing is most critical from both functional and cosmetic perspectives. “A consistent thickness is critical to the performance of the part,” said Mills. “Thickness must be uniform on each individual part as well as every part in the lot. Thickness impacts abrasion and corrosion resistance. It also impacts the fit of the part when it is a component of an assembly. Cosmetic requirements demand that the anodized finish has consistent and uniform color and graphics. Since most of the parts are assembled with other colored parts, the shading must be the same.”    

It should be noted, though, that the benefits of anodizing often overshadow the challenges the process can pose. The finish it provides often is inexpensive to obtain, and it’s durable and versatile. Anodizing also can reinforce aluminum parts by offering abrasion resistance and corrosion protection.

Coating Materials

When it comes to coatings, much of the quality-and-efficacy solution depends on material selection. According to Eric Tobin, chief operating officer of Bedford, MA-based Spire Biomedical, his company often receives requests for coatings that enhance fixation. He pointed to hydroxyapatite (a complex calcium phosphate) or tricalcium phosphate as the more commonly used materials for promoting bone fixation. “(These) coatings are of interest because they can speed device integration and mitigate device loosening problems.”
 
Hard coatings, such as titanium nitride and chromium nitride, also have fostered some interest, Tobin added, because they can enhance wear resistance. However, use remains limited in orthopedic applications because these materials raise concerns of delamination which is when the coating separates from the substrate surface. Still, he noted, “[These] coatings are of interest because they enhance important performance characteristics such as bone fixation [thereby reducing recovery times and mitigating device loosening problems] or wear resistance, which can lead to premature device failures.”    

Many coatings providers also pointed to a newer trend in orthopedic coatings: the surging demand for nanophase materials with the enhancement of nanostructured materials. Gene Elwood, senior medical accounts manager North America for Ionbond, a Madison Heights, MI-based coatings provider, noted that the demand for ‘engineered’ coatings is increasing, i.e, Ionbond’s nanotextured titanium coating, which was developed to enhance cell attachment.  

The Importance of Testing

With safety on every OEM’s mind, coatings providers have found that one of the top criteria their customers use to evaluate a potential outsourcing partner in this field is the vendor’s testing procedures for both the coating/finishing and the device itself. After all, every component of anything that goes into a patient’s body must be proven safe and effective.

Before a coating can be applied to any part of a device, the coating must be fully tested and proven safe—usually this proof and documentation must be validated both in-house and by an independent laboratory. Of course, once a coating passes the test, the provider also must use various additional testing processes to ensure that the coating will be appropriate for use with any given implant or device with which an OEM presents.

“If you have not done [proper testing], an OEM probably won’t even talk to you,” said Dennis Fulford, sales manager of Fort Wayne, IN-based Fort Wayne Anodizing.     

In terms of evaluating a finish on a product, corrosion resistance and wear are two key evaluations, Fulford said. For coatings, biocompatibility and wear-resistance testing take precedence.

Tobin additionally noted that coating delamination—which is when the coating separates from the substrate surface—is a top concern. Therefore, the potential for this problem occurring must be evaluated and addressed, if necessary.    

“Coating delamination is always a concern, particularly with hard coatings, since delaminated coatings or coating particles can lead to 3-body wear,” Tobin explained. “Therefore, it is imperative to use a coating process that provides good adhesion and to prepare substrate materials properly to optimize adhesion of the coating.”

Challenges Abound   

While tackling all the issues that present themselves during coating and finishing selections, it’s a given that challenges are bound to ensue. When anyone speaks of challenges in the orthopedic industry, it’s usually not a surprise to hear the words “time” and “money” as the top factors.

Timelines are particularly critical for finishing providers, given that they often are handed a part so close to the end of the manufacturing cycle.

“Certainly, turnaround time is always an issue. Because we are, to a large degree, the last stop for parts prior to final assembly, the pressure mounts the farther down the chain you are,” said Matt Thompson, sales manager of Richter Precision of East Petersburg, PA.    

Cost becomes an issue as well, Tobin said, when you consider that most devices don’t have budgets that tolerate significantly higher production costs stemming from a coating or finishing process. Since skimping on the coating or finishing materials is not an option, the service providers said they must constantly work to improve the efficiencies in their system and processes.

Some providers have found that one way to improve on the finishing system is investing in new machinery.

Dick Hewitt, product manager of Kalamazoo, MI-based Hammond Roto-Finish, provides capital equipment for various industries, including the once-lucrative automotive field. One trend he’s noticed is that orders for finishing machines to be used in manufacturing orthopedic products have grown as business in the automotive sector fades.

Kyle Elmblad, technical manager at Hammond Roto-Finish, added that mass-finishing equipment continues to be popular, and robotic machinery increasingly is gaining ground in orthopedics as well. The benefit of mass finishing, he said, is that it requires no programming (compared to robotic machinery).

“You just throw a part in the machine with specific meeting compounds and you finish it,” Elmblad said about the mass-finishing capital equipment.

Despite the growing demand for both robotic and mass-finishing machines, Hewitt noted that hand-finishing machinery is still desired by many orthopedic companies because of the unique designs and features of their products.

One tricky situation that finishing and coating providers alike often must deal with is the shape of an implant, because certain angles can make both processes difficult to perform. As with many medical devices these days, demands for tighter tolerances add to these challenges.

“The geometry of the implant is always a challenge,” said Harris. “The more complex the geometry, the more complex it is to coat, and that goes the same with metal finishing as well.”    
 

Communication and Education

Clearly, dealing with challenges is a major part of any coating and finishing vendor’s daily routine. As with other processes for producing a successful medical device—and coatings and finishes are no exception—communication among all the different parties involved is paramount. Educating customers is a large part of the communication process, coatings and finishing providers said.

One tactic being used to convey complex information is educational seminars. For example, Thompson said OEMs sometimes ask for certain requirements to be upheld for a coating that simply is not possible to achieve. In such cases, a seminar can help Richter Precision clearly delineate to the customer what exactly is and is not feasible—and why.
 
“There are certain limitations with the process,” said Thompson. “We do seminars for the OEM, and some of the larger subcontractors as well, to let them know [about these limitations] and keep them informed. It’s not just the medical industry—it’s any industry where they think the process is basically sending in the parts and dipping it in the bucket. The process is much more complicated than that.”    

Fulford said each party in the relationship has a duty. It’s important for the OEM customer to communicate its needs. However, when a service provider finds that the needs aren’t necessarily realistic, the vendor must be able to clearly explain the reasons in a manner that the OEM can understand.

For example, it’s non uncommon for a specialist in this field to have to convey that finishing techniques should not (and cannot) be used to try to hide imperfections in the parts. “We often are expected to work miracles with parts that are less than perfect,” Fulford explained. Once the limitations of finishing processes are fully disclosed to clients, these customers usually respond by adjusting the specs of the part or the implant, noted Duralectra’s Mills.            

“They’ll either find some other method of coating or plating, or they will adjust dimensions in their process to allow us to do what we need to do,” he explained.

A High-Gloss  Future

Industry professionals expect a bright future for the coating and finishing markets, given the growth prospects for the orthopedic sector. Looking a little more closely into what the future might hold, one area to which Elwood believes companies will pay more attention is alloy sensitivity, which is considered a high priority by surgeons in Europe (though, not yet in the United States, he said).

Elwood expects that more U.S. physicians will begin to examine this factor more closely in the future. This, in turn, should impact the market as their demands grow more vocal.

Dr. William Burghoff, orthopedic surgeon at the Orthopaedic Hospital at Parkview North in Fort Wayne, IN, reinforced the validity of this speculation as he said during a recent industry event that there have been “growing concerns” from patients and doctors with regard to certain metal allergies and sensitivities. New coating and finishing applications could respond to that need.

The next generation of implants surely will benefit from all the advances in this marketplace in terms of longevity and efficacy. As older implants are replaced, they will give way to permanent implants. Indeed, much more will be possible with the products coming down the line, all thanks to new coating and finishing developments.