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Total Ankle Arthroplasty Design
Although total joint arthroplasty has become a well-established treatment option in patients with painful osteoarthritis (OA) of the hip and the knee, the indications for total ankle arthroplasty (TAA) in patients with endstage ankle OA remain controversial. Most first-generation TAA prostheses introduced in the 1970s were two component, highly constrained or totally unconstrained prostheses requiring cement fixation. The first-generation ankle prostheses resulted in unacceptably high failure rates and necessitated a complete reconsideration of prosthetic design and surgical technique. The four main second-generation TAA designs—Agility (currently available as Agility LP; DePuy), Buechel-Pappas (formerly manufactured by Endotec), STAR (Scandinavian Total Ankle Replacement; Stryker), and TNK (Kyocera)—addressed critical shortcomings of the first-generation TAA prostheses, resulting in substantial improvement in midterm and long-term functional and clinical results. Further analysis of second-generation prosthetic failures and intensive biomechanical research led to the development of third-generation TAA designs.
Currently, two main types of TAA prostheses exist: mobile bearing and fixed bearing. Although biomechanical studies have shown that three three component designs may better mimic the complex biomechanics of the tibiotalar joint and the hindfoot complex, clinical observational studies do not reveal substantial differences in clinical outcomes between these types of prostheses.