Planning Correction of the Varus Ankle Deformity with Ankle Replacement

The technology and techniques of total ankle replacement have improved significantly over the last few decades. With these advances, the indications for ankle replacement have similarly expanded. Previously, ankle replacement was primarily indicated for patients with minimal coronal plane deformity. This excluded many patients from ankle replacement, because the most common pathology leading to ankle replacement is posttraumatic arthritis and this is frequently associated with a varus deformity. Increasingly, indications are beginning to include patients with coronal plane deformity. Previous recommendations have been to limit ankle replacement to a coronal deformity of less than 10°. Some reports have documented a higher failure rate in larger deformities. Coetzee reported a 50% failure rate with conversion to an nkle arthrodesis in 3 years for the group of patients with preoperative varus of 20° or ore. He recommended primary arthrodesis in this patient group. The latter report, owever, detailed the results of treatment of the Agility prosthesis, which in our pinion is unsuitable for accurate correction of a varus deformity. With the latter rosthesis, there are only 2 sizes of the polyethylene, which is inadequate, and as we ill see, is integral to the correct decision making and balancing of the ankle joint. Wood and colleagues found a higher incidence of edge loading of the polyethylene in patients with a preoperative deformity of 15° or more. They recommended that a coronal deformity of 15° or more be considered a relative contraindication to ankle replacement. The increased failure rates in these studies may be due to an inadequate correction of alignment and ligamentous balance intraoperatively, leading to edge loading of the polyethylene and premature implant failure.