Joints are Jumping

Micropart makers get a lift from thriving small-implant market

Though dwarfed by the more established hip-and-knee market, the orthopedic niche known as small bone and joint (SBJ) is growing much faster, providing new opportunities for large and small medical device firms as well as their suppliers.

The SBJ market includes replacement and fixation devices for the shoulder, elbow, hand, wrist, foot and ankle.

The STAR total ankle replacement system. Image courtesy Small Bone Innovations.

“In the beginning, this market wasn’t well defined in terms of its products,” said Alan Taylor, president of Solana Surgical LLC, Memphis, Tenn., which makes foot implants. Doctors were surgically implanting devices originally intended for the maxillofacial (jaw) area of the face, “because they were small and would go well in the foot, ankle or hand,” he said. “But as time went on, the industry began developing specific products for specific problems in the extremities. Now the market is growing based on people seeing a need and then customizing products to fill that need.”

Double-digit growth

By 2017, the U.S. SBJ market is expected to reach $2.4 billion, roughly double its current size, according to a report published by iData Research Inc., a market research firm based in Vancouver, British Columbia. “For at least the next 5 years, we’re seeing 10-plus percent growth for this market,” noted Andrew Park, senior business development executive at iData.

Such growth is the envy of manufacturers in more-established markets, such as large joint reconstruction. In the U.S., the growth trajectories for some of the major hip and knee procedures “have flattened out in the last 2 years, and that’s projected to continue for the next 5 years,” said Park. “The same thing can be said for traditional trauma fixation. If you’re looking at major long-bone and hip fractures, the innovation just isn’t there because the procedure volumes have pretty much stagnated, and the plates and screws used in those procedures are being commoditized.”

iData predicts especially rapid growth for the foot-and-ankle segment of the SBJ market, which is expected to more than double in size over the next 5 years. In this segment, double-digit annual growth is expected in both replacement and fixation, according to Park.

Leading the way in revenue growth will be total ankle replacement, driven by the high selling prices of new ankle replacement devices and more cases of diabetes, which can cause ankle deterioration. Despite the difficulties involved in getting FDA approvals, the total ankle replacement market is now the fastest growing SBJ segment, expanding at about a 20 percent annual rate, Park reported.

By 2017, iData expects the size of the U.S. market for all ankle devices to more than triple from its current size. Growth will be driven by the increasing popularity of three-piece mobile ankle devices, such as the STAR total ankle replacement system from Small Bone Innovations Inc., Morrisville, Pa. (See sidebar on page 38.)

At the same time, external ankle fixation will also become more widespread, iData predicts. External fixation procedures involve attaching rigid frames to the outside of the body to heal fractures. Compared to internal fixation, external fixation offers a number of advantages, including less-invasive procedures, less blood loss and shorter operating times, according to iData.

iData sees steady growth ahead for the U.S. external fixation market, as a whole, through 2017, when it’s expected to reach almost $350 million. Growth drivers for this market, cited by iData, include an aging population, the minimally invasive nature of the procedures and improvements in infection-prevention techniques.

The hot SBJ market has attracted the notice of major players such as Zimmer, Wright Medical, Stryker, Biomet, Synthes and DePuy. Still, Park said, there are opportunities for smaller companies looking to break into the orthopedic industry—if they use the right approach.

“The last thing you want to do right now is produce another trauma fixation plate with screws,” he said. “If you do, you’ll have to deal with market incumbents that have billions of dollars in cash.” A better approach for a smaller company is to “pick a growing market that hasn’t been saturated yet, such as wrist replacement or fixation, and try to gain some first-mover advantage by developing new products for that market,” said Park.

According to Park, the hand-and-wrist sector isn’t as well established as the foot-and-ankle segment, but it’s now getting plenty of attention from large and small orthopedic companies. In the area of wrist fixation, Park singled out the distal-radius (forearm) market as “probably the fastest-growing plate-and-screw market.” Product innovation is needed because of the complex structures of the wrist and forearm, “so a lot of companies are jumping in,” he said.

Product characteristics

Looking at the design of SBJ devices, one trend cited by Aarti Shetty, senior medical device industry analyst at market research firm Frost & Sullivan, is a move toward modular joint-replacement products. Consisting of multiple small parts instead of one large part, these products allow surgeons to replace part of an implant rather than the whole thing. In addition, Shetty sees more miniature components being developed for minimally invasive surgical procedures.

The SBJ market contains many small components, including implants, staples, screws and tissue anchors with single-digit-millimeter dimensions. “There’s a lot of ‘micro’ in what we do,” Solana’s Taylor noted.

That’s clearly the case at Small Bone Innovations, which offers a number of other SBJ products besides its well-known ankle system. These include a circular fixation system for diseased or deformed lower limbs, thumb and finger implants, a total wrist replacement system and an elbow management system. Tiny components and features of these products include bone screws and spray coatings 0.5mm thick. “Microscale parts and features are key to our products’ success,” said Stephen Gilbert, SBi’s director of product development.

Among the smallest SBJ components cited by iData’s Park are screws with diameters less than 3.5mm for hybrid “mini fragment” plates used for foot fixations, currently a high-growth item in the SBJ space. Park is also bullish on the prospects for what he describes as “absolutely tiny” nickel-titanium shape-memory-alloy staples used for internal fixation in SBJ applications. The market for these staples “is small right now, but we think it’s going to grow,” he said.

SBJ material options

Besides titanium, materials found in the SBJ space include cobalt-chromium. It is used for a variety of joint replacement implants and for trauma fixation products, such as plates and screws, according to Shetty. This hard, biocompatible material is less expensive than titanium, but is said to offer similar strength and better corrosion resistance, she added.

Other material options for SBJ products include ceramics and plastics, which can be less expensive than metals in some applications, Shetty said. In addition, she reported that manufacturers are trying to develop advanced versions that provide better wear resistance than metals, which could reduce the need for follow-up surgeries.

Plastics used to make SBJ products include PEEK-based biocompatible polymers like those available from Invibio Ltd. The company, which is headquartered in Lancashire, U.K., and has U.S. offices in West Conshohocken, Pa., reports that in orthopedic applications, the materials offer the following benefits:

Wear resistance for articulating devices. The wear characteristics of PEEK-based biocompatible polymers can be “extremely good,” according to Adam Briscoe, the company’s product development project manager for joint arthroplasty. In addition, he noted, they can often be as good as the wear characteristics of metals and ceramics.

The STAR Total Ankle replacement system includes three main components. The tibial plate (right) is made from cobalt-chromium molybdenum. This wedge is shaped to conform to the existing ankle anatomy. The polyethylene mobile bearing (center) is made from ultrahigh-molecular-weight polyethylene. The talar component (left) is designed as an anatomical prosthesis to cover the talar dome, anterior, posterior, and medial and lateral facets. Like the tibial plate, it is made from CoCrMo. Image courtesy Small Bone Innovations.

This photo shows the assembled device. Image courtesy Small Bone Innovations.

Strength. Invibio’s ENDOLIGN composite, for example, offers metal-like strength for trauma applications, high compressive strength to handle load requirements and enough fatigue strength to allow many motion cycles without failure, according to the company. Briscoe also points to the polymer’s high strength-to-weight ratio, which lets manufacturers use lighter components.

Low creep improves implant stability.

Cost savings. Briscoe says there can be a cost advantage in using PEEK-based biocompatible polymers in place of other material options. The actual amount depends on factors such as the component design and the amount of waste caused by processing.

Changeable imaging characteristics. Different applications call for different imaging characteristics, Briscoe noted. Sometimes it’s better for a device to be invisible to X-raying—so bone can been seen growing around an implant. Other applications require an implant to be seen in the image so doctors can spot any shift in its position. With the company’s radiolucent PEEK-OPTIMA, imaging characteristics can be tailored to the application by adding different quantities of barium filler (more filler produces greater X-ray contrast).

As for specific applications in the SBJ market, Briscoe reports that a couple of small finger joints are made of PEEK-OPTIMA supplemented with different fillers—carbon-fiber reinforcement in one case and barium in the other (to make the joint visible on radiographs).

In addition, Invibio noted that a European manufacturer of finger-joint prostheses switched from polyoxymethylene copolymer (POM C) to PEEK-OPTIMA. When tested against POM C, PEEK-OPTIMA exhibited up to 40 percent higher tensile strength and elastic modulus, as well as better wear behavior during articulation with human cartilage, according to the company.

Looking ahead, Invibio is considering different options to improve PEEK-OPTIMA’s interaction with biological tissue for fixation applications, according to Briscoe. One way would be to add a bioactive ingredient to the polymer. Another would be to develop a means of treating the surfaces of components made of the material to encourage bone growth into and onto them.

Opportunities for manufacturers

Material makers like Invibio aren’t the only suppliers profiting from contracts with companies in the SBJ market. Contract manufacturers are scoring deals with these firms as well. As the SBJ market grows, the need for manufacturing services will grow too.

Probably more than 75 percent of the companies in the SBJ market use contract manufacturers, according to Taylor, who spent almost 20 years at Wright Medical and founded two other companies that make SBJ products before joining Solana.

“Most of the smaller companies have no plans to develop their own manufacturing,” he said. “When you’re building a market like Solana is, the volumes are small in the beginning. So you have to find suppliers that are willing to do small lots at first and bet on what you can do later on.” At one of the companies he founded, for example, “we started off real small with a fusion implant and ended up selling thousands of them.”

What about big companies? “They want efficiencies of scale in their plants, so they tend to farm out the lower-volume stuff,” he explained. “When I was at Wright, we had a policy of farming out manufacturing at the beginning and waiting to see if volume went up. In the case of several products, volume got high enough that we brought the manufacturing inside. Generally, though, the outside vendors do a better job of holding costs down. They don’t have the overhead that an orthopedics company might have.”

What’s more, manufacturing suppliers can, and do, provide input that ends up improving the product. “They’ll ask questions, and we’ll say, ‘Why didn’t we think of that?’ ” Taylor said. µ

For more information on the SBJ market

Some of the information in this article comes from “U.S. Market for Small Bone & Joint Orthopaedic Devices 2011,” a report published by iData Research. To order this report, visit the iData Web site: www.idataresearch.net.

Three-component ankle offers greater mobility

A joint implant from Solana Surgical. Image courtesy Solana Surgical.

Today, there are a number of options for treating painful, arthritic ankles. One is to fuse or join the ankle bones together. Once an ankle is successfully fused, however, the patient loses mobility in the joint.

Another alternative is to replace the ankle joint with a prosthetic device that attempts to mimic real ankle movement. One such device is Small Bone Innovations’ STAR ankle system. Approved by the FDA in 2009, the STAR ankle has been implanted in more than 15,000 patients worldwide, according to iData Research, which follows the orthopedic ankle market.

X-ray shows a Solana implant in a patient’s foot. Image courtesy Solana Surgical.

In all total-ankle procedures, metal components replace the ankle’s bone surfaces. The STAR ankle includes two cobalt-chromium parts, one that covers the lower bone of the ankle joint and another that covers the bottom of the shin bone.

While other ankle implants require cement to attach the implant parts to the bone, the STAR ankle attaches directly to the bone without cement, relying instead on the growth of bone that adheres to the implant. Why? “The body doesn’t adhere to cement because it views cement as a foreign object,” explained Stephen Gilbert, SBi’s director of product development. “So for better fixation, what you’d like is for the bone to grow onto the implant without cement.” To promote this growth, the STAR’s metal components are coated with a titanium-plasma spray. “Bone likes the spray, so it actually grows onto and into the surface of our implant,” Gilbert said.

In addition to the two metal parts, the STAR ankle includes a plastic mobile bearing. This component, made of ultrahigh-molecular-weight polyethylene, moves between the metal parts as the ankle is moved. In other U.S. ankle implants, the plastic piece is attached to one of the metal parts. Compared to these two-component ankles, designs with mobile bearings pose more technical challenges but are better at replicating natural ankle motion, according to iData.

One of the challenges for ankle implants is to minimize wear when the metal articulates with the plastic component. This wear produces debris that degrades nearby bone. SBi lessens the wear by polishing the surfaces of the ankle’s raw metal component castings to produce a mirror finish, Gilbert reported.

Though some surgeons still aren’t sold on the three-piece ankle concept, iData believes the ankle replacement market is going to be driven by the development of new three-component implants, said Andrew Park, senior business development executive at the firm. “We know that Wright Medical, Tornier and DePuy are all interested in developing their own three-piece devices because they’ve seen how much attention SBi has been getting.”

—W. Leventon

Artificial finger allows real movement

The X-Finger is an artificial finger assembly designed specifically for partial-finger amputees. Developed by Didrick Medical Inc., Naples, Fla., the device provides users complete control of the flexion and extension movements of an artificial finger in a self-contained unit.

The X-Finger incorporates a metal framework with joints similar to actual fingers. Image courtesy Didrick Medical.

The X-Finger replaces the distal and middle phalanges of one or more fingers. A residual finger can articulate the replaced phalanges of the same finger, as well as the phalanges of an opposing finger. The replaced phalanges follow the natural bending motion of a finger.

The X-Finger does not require batteries or motors. Finger movements are guided by the same cognitive process previously used to flex and extend the natural finger, so users can operate the X-Finger without any training.

The design of the X-Finger includes a metal framework with joints similar to an actual finger, covered by a skin-colored sheath. “We use surgical stainless steel for all of the parts that are weight bearing,” said CEO Dan Didrick. “There are two plastic parts that help to hold the shape of the finger. Then, the device is inserted into a cosmetic glove fabricated from thermoplastic. The material matches the softness of human skin and is very tear resistant.”

Each unit is custom-assembled to match the patient’s finger size. “Several of the components are manufactured longer than they will ultimately end up being,” said the owner. “When measuring for a patient, several of the parts are cut short, polished and assembled. Therefore, the devices are not customized for each patient, but rather custom-assembled. In all, we have developed an erector set of parts, so to speak, that can be assembled into more than 500 configurations in approximately 16 different lengths.”

The X-Finger is registered with the FDA and CE-marked under the Medical Device Directive of Europe, which means it can be sold throughout the European Union. (To view a video of the X-Finger in use, click here.)

—Susan Woods

Contributors

Didrick Medical Inc.
(877) DIDRICK
www.didrickmedical.com

Frost & Sullivan
(877) 463-7678
www.frost.com

iData Research Inc.
(604) 266-6933
www.idataresearch.net

Invibio Ltd.
(866) 468-4246
www.invibio.com

Small Bone Innovations Inc.
(215) 428-1791
www.totalsmallbone.com

Solana Surgical LLC
(855) 214-1860
www.solanasurgical.com