Copy to clipboard 
BomSoo Kim, M.D., Ph.D., knows that vascular necrosis of the talus is one of the most challenging problems in orthopedic foot and ankle surgery.
“The talus is a uniquely complex bone, transmitting nearly the entire body weight from the leg to the foot, while allowing multidirectional motion across the ankle and subtalar joints,” said Dr. Kim, Professor and Chief of the Department of Orthopaedics at Inha University Hospital in Incheon, Korea. “It has no muscular attachments and depends on a very limited vascular supply, which makes biological healing inherently difficult.”
Once circulation to the talus is compromised, necrosis and structural collapse can rapidly develop, leading to progressive arthritis in the ankle and subtalar joints.
“For early-stage disease, multiple drilling procedures or core decompression can promote revascularization, but these treatments are often ineffective and tend to result in disease progression and eventual collapse of the joint,” Dr. Kim said. “In advanced cases with significant talar necrosis or structural loss, surgeons typically resort to ankle or tibiotalocalcaneal fusion, which provide stability and pain relief but sacrifice joint motion.”
Once the talus collapses, fusion often becomes the only viable option, but it comes at the cost of eliminating joint motion. “Even achieving a solid fusion is challenging because of the large bone defect that typically requires substantial bone grafting, compounded by the talus’s poor intrinsic vascularity,” Dr. Kim said.
In recent years, personalized total talar replacement solutions have provided promising alternative treatments when surgeons want to avoid fusing the joint, but Dr. Kim said they often use metallic or ceramic materials to preserve mobility.
“Many were poorly contoured, solid and heavy or brittle, and some carried a risk of allergic reactions or mechanical failure over time,” Dr. Kim said. “These shortcomings highlighted the need for a patient-specific implant that could more accurately restore native anatomy, ensure biocompatibility and maintain natural joint motion.”
Dr. Kim’s team used pure titanium to create a talus replacement implant that offers exceptional biocompatibility and favorable mechanical properties. He said pure titanium enables direct osseointegration when required, is highly corrosion-resistant, non-toxic and demonstrates excellent long-term biological stability.
“The greatest advantages of pure titanium are its exceptional biocompatibility, outstanding corrosion resistance and unique ability to achieve direct osseointegration without additional surface coatings,” Dr. Kim said. “It’s also considerably lighter than cobalt chromium alloys or ceramics, reducing the overall implant weight and enhancing patient comfort.”
Equally important, the surface chemistry of pure titanium promotes stable bone attachment and minimizes the risk of adverse tissue reactions. Unlike some alloys, it does not release metal ions or trigger inflammatory or hypersensitivity responses, which contributes to its excellent long-term tolerance in vivo.
Design Features
The patented 3D printing technology used by Dr. Kim’s team allows them to precisely tailor the microstructure of the pure titanium implant, achieving an optimal balance between mechanical strength and biological performance. “Anatomical fidelity was our priority,” he said. “We used high-resolution CT data from a patient’s healthy contralateral talus to accurately mirror its three-dimensional geometry.”
The articular surfaces were then contoured to ensure congruent articulation with the tibial plafond and calcaneus and navicular bones, allowing for smooth load transmission and near-physiologic motion across the ankle and subtalar joints.
“We also incorporated graded internal cavities within the implant to reduce the overall weight while maintaining the required mechanical strength,” Dr. Kim said. “This internal structure helps replicate the natural biomechanical behavior of the native talus under compressive loading.”
Dr. Kim’s team integrated a porous structure into the implant’s surface layer, which can be selectively printed in areas where bone integration or partial fusion is desired. This feature allows the implant to achieve biological fixation when necessary, enhancing stability and long-term durability.
The external contours of the implant were carefully designed to preserve smooth articulation and even load transfer across the ankle and subtalar joints, closely replicating the natural kinematics of the native talus. That way, Dr. Kim said, movement remains fluid and contact pressures are distributed evenly during weight-bearing.
Internally, the implant incorporates the research team’s patented graded cavity design, consisting of an intricate network of interconnected cells and variable porosity.
“By gradually adjusting the size and density of the internal cavities, the design achieves controlled stress distribution and minimizes the risk of localized overload,” Dr. Kim said. “The cellular framework also provides mechanical damping, absorbing impact forces during gait and enabling the implant to behave more like native bone rather than a rigid prosthesis.”
Next Steps
Dr. Kim and his team are focused on clinical validation and technological refinement of the implant they created. Long-term follow-up studies are underway to assess functional outcomes, implant survival and patient satisfaction.
They’re also optimizing surface properties for enhanced osseointegration and improved wear resistance, and collaborating with materials scientists and regulatory partners to establish standardized manufacturing and validation protocols for 3D-printed patient-specific implants.
“Our ultimate goal is to make this technology more widely accessible and to expand its application to other small and complex joints, where conventional reconstructive options remain limited,” Dr. Kim said.
