The treatment of ankle osteoarthritis with total ankle arthroplasty has experienced a resurgence over the past three decades. The introduction of the Agility total ankle implant in the early 1980s was the genesis of the contemporary efforts at ankle arthroplasty1. The early success of that fixed-bearing implant, as well as the less-favorable longer-term outcomes, spurred the development and introduction of a number of newer fixed and mobile-bearing designs, including the two implants highlighted in this study, the two-component Salto-Talaris and INBONE total ankle prostheses.
Recent reports have demonstrated that the results of total ankle arthroplasty are on par with, and possibly superior to, those of arthrodesis with respect to pain and function2,3. In addition, the survivorship of total ankle implants, while not yet demonstrated to be equivalent to that of total hips and knee implants, has been shown to be quite favorable at intermediate-term follow-up. Mann et al. demonstrated 90% survival at ten years and Nunley et. al. showed 88.5% survival at 8.9 years with the STAR (Scandinavian total ankle replacement) mobile-bearing implant4,5. This solid clinical performance has further bolstered a trend in favor of total ankle replacement. Earlier this year, the authors of the current study reported the early clinical results for their patients who underwent total ankle replacement with the Salto-Talaris implant, which showed 96% implant survivorship at 2.8 years. While these results are encouraging, they should be considered preliminary, like all of those related to the newest generation of fixed-bearing implants6.
Unlike those of hip and knee arthroplasty, the art and science of total ankle replacement are still in a period of self-exploration. While most surgeons likely remember from residency training the well-established approach to knee ligament balancing, a unified approach to achieving a well-balanced ankle replacement is still a work in progress. Coronal plane balancing often involves both extra-articular and intra-articular techniques, including hindfoot osteotomies and ligament reconstruction, either at the time of total ankle replacement or as part of a staged procedure. For most patients in the current study, the authors employed one or more adjunctive procedures at the time of total ankle implantation to achieve normal ankle coronal plane alignment, the most common being a medial or deltoid release (twenty-seven patients), subtalar arthrodesis (eleven), calcaneal osteotomy (seven), and lateral ligament reconstruction (seven). These are typical balancing procedures for anterior-approach total ankle replacements and are commonly used by most experienced foot and ankle surgeons.
Preoperative coronal plane deformity, especially beyond 20°, continues to be a particular concern for surgeons. Previously, Reddy et al. reported universal failure in patients with >25° of preoperative deformity but also showed that alignment was maintained, at an average of average of 3.4 years of follow-up, in 93% of patients with <25° of deformity7. Similarly, the authors of the current study followed 103 patients for two years and were able to demonstrate that 95% of patients had maintenance of neutral alignment, defined as <5° of varus or valgus, at the time of the two-year follow-up. The authors defined their “excessive deformity” group as the seventeen patients with >15° of varus or valgus, with an average of just 21.3°. While the number of patients with >25° of varus or valgus was not reported, and likely was quite small, the fact that no recurrences were reported in this series is encouraging. Most importantly, the authors reported excellent clinical and functional measures for the series as a whole and could not demonstrate any impact on outcome on the basis of preoperative deformity.
In conclusion, the authors have demonstrated that the correction of coronal plane deformities of 20° at the time of implantation of a modern fixed-bearing total ankle implant is durable at two years of follow-up without diminution of clinical or functional outcomes measures.