Excitement Surrounds the Growth Potential of Ankle Replacement Surgery

Hip and knee replacement? Been there, done that. A certain malaise sets in with repeatable excellent outcomes. Ankle replacement? Now that’s a different story. It’s relatively new. It’s exciting. Advancements in the field will be exponential, not incremental.

“The ankle is unique in that it’s subjected to higher concentrations of force applied to a small area, and the anatomy is extremely complex,” said Shannon Cummings, Vice President of Enovis’ foot and ankle division. “There are a lot of challenges to overcome that the industry continues to work toward solving.”

A wave of groundbreaking innovations is reshaping the landscape with the promise of increased precision, extended implant longevity and improved patient outcomes. From novel implant materials to patient-specific instrumentation and emerging surgical techniques, these developments are poised to enhance patient outcomes and redefine the field.

The challenges associated with ankle replacement surgery include the joint’s complex structure, the necessity of long-term implant durability and the wide range of varying patient anatomy. Plus, as a relatively new procedure, clinical studies are still determining which technologies and processes work best for individual patients. Remarkably, only 16 orthopedic companies have a total ankle implant on the market compared to more than a hundred companies that market hip and knee implants.

“Total ankles have not been around as long as total hips and knees,” said Devan Carter, Director of Marketing for foot and ankle at Exactech. “Experts in the segment are seeking more information to achieve optimal outcomes. Why do implants fail? How do they fail? How can new designs and materials ensure they last 20-plus years like they do in knees and hips? These are the questions that need answering.”

Materials and Implants

One of the top developments in ankle replacement surgery involves advancements in material composition that aim to boost implant longevity. Technologies like 3D-printed surfaces and vitamin E-based polyethylene show promise in making implants last longer, Carter said.

Exactech’s Activit-E polyethylene, which is used in the company’s Vantage Total Ankle System, is a next-generation, highly crosslinked material that provides strength, flexibility, toughness and oxidative stability.

“It’s a total game-changer,” Carter said. “Ankle implants are approaching 12- to 15-year survivorship. We’re seeing that this poly can boost the longevity of implants even further to match the performance of knee and hip implants.”

The success of Enovis’ Scandinavian Total Ankle Replacement (STAR) system is rooted in its mobile bearing platform, which reduces stress at the bone/implant interface. This results in lower micromotion and has been shown in peer-reviewed journals to extend long-term metal component survivorship.

Cummings said Enovis is committed to improving STAR, particularly in the areas of oxidative resistance and the integration of vitamin E polys. STAR is poised to enter the market with vitamin E poly, promising extended longevity and enhanced wear resistance.

“Our strategic focus on investing in a polyethylene bearing surface has already paid dividends on implant longevity,” Cummings said. “These advancements give replaced ankles a longer and more active life.”

Companies in the ankle replacement space are using 3D printing to better integrate bone into implants, Cummings noted. He’s seen an uptick in the transition from traditional plasma-coated implants to devices that utilize 3D-printed titanium surfaces that encourage bone ingrowth.

“Historically, most implants were plasma coated and featured roughened surfaces for bone to attach to,” he said. “Now, 3D-printed materials are used to produce implants. Performance data is lacking because the devices are somewhat new to the market, but as we look to the next generation of total ankles, bone will grow into implants instead of only on top because of the 3D-printed material.”

Last October, Exactech earned FDA 510(k) clearance for its 3D-printed tibial implants: the Vantage Ankle 3D and 3D+. The implants are designed with a porous surface to aid with biological fixation. They also feature spiked pegs and a center bone cage of various lengths to promote improved initial fixation.

The Vantage Ankle 3D+ is a stemmed implant that comes in several tibial height options. Carter said the additional stem height offerings provide more stability in patients with anatomical deformities, comorbidities and poor bone quality.

“One of the most important aspects of total ankle surgery is having a wide range of implant sizes available for a variety of patients,” Carter said. “The tibial height options of the Vantage Ankle 3D+ give surgeons the freedom to decide what’s needed to optimize implant longevity in individual patients.

“Overall knee and hip replacement outcomes are similar, but total ankle outcomes are all over the board,” she added. “Determining what implant is right for each patient and their needs is helping to create an algorithm for longer survivorship.”

The STAR PSI system from Enovis provides a personalized preoperative plan for individual patients.

Patient-Specific Options

To that end, R&D efforts in ankle replacement are focused on producing ways to precisely match implants and instrumentation to individual patients. Tailored surgical plans and personalized cutting guides that are based on the preoperative scans of specific patient anatomy contribute to enhanced surgical accuracy and reduced operating room time. They also provide surgeons with a detailed roadmap to follow while operating.

Exactech’s patient-specific approach is exemplified through its Vantage Ankle PSI technology, which features 3D-printed instruments that are used in conjunction with tibial and talar cutting guides. These cutting guides are designed to circumvent osteophytes or the affected joint — in other words, match the patient’s anatomy — to strategically minimize variability induced by disease progression.

Enovis’ STAR Ankle PSI, released in early 2023, provides surgeons with a preoperative plan for patients and creates a 3D model of a patient’s ankle joint that shows the location of existing implants or bone defects. This not only offers surgeons increased accuracy but can also reduce up to 30 steps of a procedure, reducing overall surgical time and contributing to better patient outcomes.

“We can make specific instrumentation that conforms to the patient’s anatomy and allows surgeons to make a more precise cut,” Cummings said. “That’s great for surgeons because they’re able to be more accurate and operate more efficiently. It’s also great for patients because the longer they’re in the O.R., the more risk is involved. The more we can speed up these procedures, the better.”

Patient-specific solutions also reduce incision sizes and minimize soft tissue disruption. While minimally invasive surgical techniques have gained traction in recent years in other applications, applying them to total ankle replacement remains challenging due to the use of larger bone cuts and implants. However, Cummings noted that STAR Ankle PSI helps to reduce incision sizes and leverages other technologies for a less invasive approach.

Navigation Enters the Equation

Exactech wants to take personalized ankle replacement surgery to the next level with its new navigation system. ExactechGPS Ankle, which received FDA 510(k) clearance last December, is a first-of-its-kind technology that connects preoperative plans with real-time intraoperative instrument guidance. The technology, which allows for intraoperative navigation with sensors placed on the ankle and instruments, has already been applied successfully in shoulder and large joint replacement surgery.

GPS Ankle uses proprietary active tracker technology and a touchscreen tablet to provide surgeons with intraoperative feedback throughout surgery. It also enhances the accuracy of surgery by confirming that resections match the preoperative surgical plan. Surgeons can ensure precise execution of the plan and make necessary adjustments during surgery.

The system is compatible with Exactech’s Vantage Total Ankle and will be available to users without additional capital cost. Pre-clinical studies involving bench testing reported that the technology produced cuts within 2mm and two degrees of CT-based surgical plans. These findings were confirmed by two studies performed on sawbones.

Not only can the system help surgeons perform better surgery, but, according to Carter, the clinical data it collects will provide a much-needed deep dive into total ankle outcomes that Exactech can use to improve its enabling technologies even further.

“I’m excited about GPS Ankle’s potential,” she said. “It’s going to allow us to conduct research on ankle replacement surgery. The platform can take pre-op and post-op scans of a patient’s range of motion in the joint and capture the data. We’re hoping to use this information to better understand what makes a total ankle procedure successful and ultimately provide recommendations to help the surgery go more smoothly.”

Exactech’s Vantage Ankle 3D and 3D+ implants provide surgeons with additional tibial height options for total ankle replacement patients.

Looking to the Future

The ankle replacement field is continually advancing, with companies exploring the potential of using enabling technology to elevate surgeon training and surgical precision. Despite the inherent challenges posed by total ankle procedures, Cummings anticipates transformative developments in robotics, navigation and augmented reality.

“The investment to get these advanced technologies off the ground in this space is difficult to justify when case volumes are comparably lower than knee and hip replacements,” he said. “Efforts to make enabling technology more affordable and accessible will especially benefit the total ankle segment.”

Carter envisions a future in which ankle replacement surgery achieves the same level of success that shoulder replacement has realized. She anticipates ongoing evolution in the ankle replacement field and stresses the significance of data-driven decision-making, along with algorithmic approaches for implant selection and survivorship analysis.

“Exactech’s Predict+ software system allows surgeons to input a shoulder replacement patient’s specific information. It then recommends which implant to use and generates a graph of survivorship rates for that implant,” Carter said. “Surgeons feel confident about that implant’s expected longevity and are given the information they need to set realistic outcomes expectations with their patients. I’m hoping we will get there with total ankles.”

Experts in the field believe ankle replacement surgery will continue to advance along the pathway of innovation that’s been blazed by hips, knees and shoulders.

“We’re going to see more advancement in this space over the next decade,” Cummings said. “It’s been interesting to watch the evolution because although surgical volume within ankle replacement surgery is low, the amount of attention that it has received has been amazing.

“You’re going to see the market evolve in ways that are similar to what’s occurred in other large joint spaces,” he added. “But it’ll happen a lot faster, and you’ll see the impact in greater terms simply because we’re not looking to run faster. We’re looking to go from walking to running.”