Can the total ankle replacement (TAR) provide a viable alternative to ankle arthrodesis? In addition to reviewing the FDA approved TARs in the United States, advances in device design and the current literature, these authors emphasize proper patient selection, sound pre-op planning and other insights from their experience in performing total ankle arthroplasty procedures.
End-stage osteoarthritis (OA) of the ankle is a major cause of pain and disability. The most common cause of ankle degeneration is previous trauma with ankle fracture-dislocations being common.1,2 The treatment for disabling ankle arthritis remains a controversial topic. Until recently, the “gold standard” treatment for painful arthritis has been an ankle arthrodesis.3-5 With unique designs, comprehensive patient follow-up and improved instrumentation, total ankle replacements (TARs) have become increasingly popular. These features now make the option of an ankle replacement more attractive.6
Accordingly, let us take a closer look at the emergence of TAR, current literature and the evolution of TAR surgery at our institution.
Lord and Marotte performed the first ankle prosthesis procedure in 1970.7 When only seven of 25 implants proved successful, they abandoned the procedure. Many design changes have occurred since the introduction of TAR in the early 1970s. Initially, the ankle prosthesis was highly constrained and consisted of a complete polyethylene tibial component, which required large bony resection and cement for implant fixation.8 Low patient satisfaction and a high complication rate — including loosening, subsidence and osteolysis — slowed the use and popularity of the prosthesis.9
Newer implant designs, referred to as second- and third-generation implants, developed in the 1980s. They consisted of three pieces: tibial and talar metallic components, and a bearing surface made of high-molecular weight polyethylene interposed between the metallic components.8,10 These new generation implants are also classified as two- or three-component designs. The two-component implant, also referred to as a fixed-bearing device, locks the polyethylene piece within the tibial component. The three-component implant, referred to as a mobile-bearing device, provides two distinct and independent articulation interfaces for the polyethylene component, allowing translation, rotation and flexion.8
The new implant designs were meant to function with less constraint, require less bone resection and utilize stems or pegs for fixation instead of cement.10 Many of the second-generation implants, though, had increased polyethylene wear and failure, leading to instability and even reported dislocation of the components.10 With the advent of the newest third-generation implants, manufacturers have placed more emphasis on improved instrumentation, soft tissue balance, a plantigrade foot and patient selection and education.11 These elements have led to greater long-term results.12,13
A Pertinent Review Of Approved Total Ankle Replacements
There are currently five total ankle replacement systems approved for use in the United States by the Food and Drug Administration (FDA). These devices include: the Agility LP Total Ankle System (DePuy); the INBONE total ankle (Wright Medical); the Salto Talaris anatomic ankle (Tornier); the Eclipse Total Ankle (Integra LifeSciences); and, most recently, the Scandinavian Total Ankle Replacement (STAR) (SBI). All the approved devices, except the STAR, are fixed-bearing, two-component systems. The STAR ankle is the only approved three-component, mobile-bearing system available for use in the U.S.