The Salvage of Complex Hindfoot Problems with Use of a Custom Talar Total Ankle Prosthesis
Reference: Ketz J, Myerson M, Sanders R. J Bone Joint Surg Am. 2012; 94-A:13:1194-1200
Scientific Literature Review
Reviewed by: Dresden Beier, DPM
Residency Program: Botsford Hospital
Ankle arthritis is a severe and debilitating deformity that affects many patients. There are treatment modalities for this end-stage disease, one being a total ankle arthroplasty, but surgeons are limited to salvage procedures if arthroplasty has failed. Many mechanical factors can contribute to a failed arthroplasty, but when there is a talar component subsidence, the end result may lead to subtalar joint degeneration and arthritis. Recently, a custom long-stemmed talar component has been described and is placed across the subtalar joint into the calcaneus. This treatment option has provided an alternative to a tibiotalocalcaneal or pantalar arthrodesis. This modality allows motion at the ankle joint with combined arthrodesis of the subtalar joint.
Between November 1, 2004 and February 28, 2006, 33 revisional total ankle arthroplasties were performed using a custom Agility long-stemmed talar prosthesis in 32 patients. The indications for prosthesis included: failure of total ankle arthroplasty secondary to severe talar subsidence with subtalar joint arthritis (13 patients, 39 percent), ankle and hindfoot joint arthritis secondary to primary osteoarthritis or post-traumatic arthritis (14 patients, 42 percent) and stage-IV flatfoot deformity (six patients, 18 percent). Patients were assessed using the following questionnaires: Short-Form-36 (SF-36), Physical Component Summary (PCS) and a Mental Component Summary (MCS), American Orthopaedic Foot & Ankle Score (AOFAS) and the Maryland Foot Scores (MFS). Patients were further evaluated for range of motion and radiographic results.
Patient follow-up averaged at 58.6 months with a minimum of 52 months. There was no clinical or radiographic evidence of delayed or non-union bone healing within the subtalar or triple arthrodesis group. The position and alignment of the foot were evaluated radiographically and 30 of the 31 lower extremities had acceptable outcomes (within 5 degrees of varus and 10 degrees of valgus). There was one unacceptable outcome (>5 degrees of varus), which underwent a calcaneal osteotomy to resolve the deformity. The mean preoperative dorsiflexion was -1.4 degrees ±7 degrees, mean preoperative plantarflexion was 25.5 degrees ±12degrees, and an average arc motion of 21.3 degrees ±14 degrees. The average postoperative dorsiflexion was 6.4 degrees ±6° (p < 0.05), the average postoperative plantarflexion was 25.8° ±10° (p = 0.26), and an average arc motion of 32.2° ±11° (p < 0.05). Three of the thirty-one ankles exhibited talar component subsidence (9.7%). None of the three ankles with talar componen degrees subsidence was greater than three mm. The mean PCS score of the SF-36 was 28.2 ±5.6 preoperatively, which increased to 39.7 ± 6.5 postoperatively (p < 0.05). The mean MCS score of the SF-36 preoperatively was 42.2 ±13.8, which increased to 50.8 ±12.6 postoperatively (p < 0.05). The mean MFS preoperatively was 47 ±13, which increased to 75 ±10 postoperatively (p < 0.05). The average AOFAS preoperatively was 41 ±16, which increased to 68 ±12 postoperatively (p < 0.05). A total of three patients failed the custom long-stemmed talar prosthesis, all greater than 36 months following the implantation.
This study presented a range of pathologies which were indicated for the custom Agility long-stemmed talar prosthesis. The pathologies included: failed total ankle replacement, severe hindfoot arthritis, and stage-IV posterior tibial tendon dysfunction. The authors of this study were able to demonstrate an increase in the total functional outcome scores for each of the pathologies presented. Therefore, the use of the custom Agility long-stemmed talar prosthesis may be a reasonable alternative to salvage arthrodesis in these end-stage diseases or as a revision to failed total ankle arthroplasties.