Midterm Outcomes Following Conversion of Failed Ankle Arthrodesis to Total Ankle Arthroplasty, Including Patients With a Deficient Fibula

Abstract

Background: Previous studies of conversion of failed ankle arthrodesis to total ankle arthroplasty showed failure in patients with an absent distal fibula, and more recently that has been considered a contraindication. However, these conclusions were based on limited case series with older prosthetic designs, and the potential for successful conversion in this challenging patient population remains unclear. This retrospective study examines the midterm follow-up of 21 patients treated for a conversion of failed ankle arthrodesis by a single surgeon using a standard technique with a single prosthesis, with a focus on the treatment of 5 patients with a deficient distal fibula.

Methods: Between May 2010 and August 2019, 27 patients underwent conversion using a prosthesis with an intramedullary tibial component, 21 of which were available for the study. Six patients had a deficient distal fibula, and 5 were available for follow-up. Our primary outcome measure was having a total ankle arthroplasty in place. Secondary outcomes were evaluated postoperatively with a visual analog scale, the American Orthopaedic Foot & Ankle Society (AOFAS) ankle and hindfoot score, a satisfaction survey, and radiographic assessment of the arthroplasty and any concomitant hindfoot fusions.

Results: Mean follow-up for all patients was 7.6 (2.6-11.8) years, with follow-up of the deficient fibula group of 8.2 (4.9-11.8) years. Complications included malleolar fracture with or without subsequent surgery (n = 5), varus deformity (n = 1), and wound dehiscence or infection (n = 2). At final follow-up, all patients, including the 5 with a deficient distal fibula, had an intact ankle arthroplasty, although 3 with intact fibulas had undergone prosthetic revision. Postoperative dorsiflexion was 4.5 ± 5.1 degrees and plantarflexion 20.9 ± 13.37 degrees. There were no pseudarthroses in the 11 patients with concomitant hindfoot arthrodesis. Mean (±SD) VAS score was 4.4 ± 3.0 and AOFAS score was 71.2 ± 21.7. Sixty-seven percent reported that they were satisfied or very satisfied, with 16% dissatisfied or very dissatisfied. One of the deficient fibula patients was very dissatisfied. Seventy-six percent had no limitations with activities of daily living and two-thirds of those had no limitations at all.

Conclusion: Consistent with previous studies, we find that total ankle arthroplasty can be a satisfactory salvage procedure for patients with a failed ankle arthrodesis. Unlike previous reports, we observed high prosthetic retention in patients with a deficient fibula, although pain relief and range of motion outcomes were mixed, and some patients required revision surgery. These findings should be interpreted in light of the intrinsic limitations of a small sample size, lack of preoperative comparison data, and incomplete follow-up in the deficient fibula group.

Level of evidence: Level IV, clinical research.

Keywords: failed ankle arthrodesis; salvage of failed ankle arthrodesis.

Visual Abstract

This is a visual representation of the abstract.

Figure 1.

Patient 1: (A, B) 50-year-old woman with failed ankle arthrodesis and subtalar arthritis with a varus fracture deformity in the tibia. (C, D) Initial postconversion views of original INBONE prosthesis with tibial stem placed in varus due to constraints of her fracture deformity. A talar body fracture was fixed with screws, and a subtalar fusion with fusion rods. After insertion of the prosthesis, there was demonstrable lateral instability, necessitating transfer of the peroneus brevis tendon into the distal end of the fibula stump at the same setting. Final follow-up 141 months after conversion (E, F) shows tibial-talar malalignment increased by 9.6 degrees. The tibial prosthesis alignment is unchanged. The ankle was stable and the patient declined further ankle surgery.

Figure 2.

Patient 4: (A, B) 68-year-old woman with painful subtalar arthritis after an ankle arthrodesis for failed ankle ORIF. (C, D) Initial postconversion views show ankle prostheses in place. A talar body fracture was fixed with a single screw. A thin medial malleolus was fractured when the ankle was manipulated before the medial bone cut was completed. This was temporarily fixed at the time, and 10 days later definitive fixation was applied with the long plate and screws fixing the medial malleolus. A deltoid reconstruction was also done with an allograft tendon, and the button in proximal tibia adjacent to plate is fixation for that. The subtalar arthrodesis was fixed with a cannulated screw. The symptomatic plate and screws were removed 3 years after conversion. (E, F) At 121 months after conversion, the prosthetic alignment is maintained, and the subtalar fusion and the talus and malleolar fractures have healed with a hypertrophic medial malleolus.

Figure 3.

Patient 5: (A, B) 69-year-old woman who underwent ankle arthrodesis for posttraumatic arthritis had previously also had a triple arthrodesis done. (C, D) She had painful malposition of her pantalar fusion. Initial postconversion views show large components, with fractures of the medial and lateral distal tibia. The lateral fracture was fixed with a single wire, with no fixation medially. (E, F) The final radiographs at 121 months after conversion show the prosthetic alignment has been maintained. The wire fixing the lateral distal tibia fracture was previously removed, and the fractures have healed with exuberant bone formation, leading to ankylosis of the joint. This patient was dissatisfied.

Figure 4.

Patient 15: (A, B) 64-year-old man had previously been treated for osteoarthritis with a tri-component ankle replacement and calcaneal osteotomy. After developing an infection and undergoing prosthetic removal and several debridement procedures, he had arthrodesis attempted, but unfortunately developed a pseudarthrosis. He was advised to have an amputation. (C, D) Initial postconversion views show the ankle prosthesis in place. (E, F) The final radiographs at 49 months after conversion show a tibial-talar malalignment of 97.9 degrees. The tibial stem and talar component position are unchanged.

Figure 5.

Patient 18: (A, B) 40-year-old man had multiple trauma from a fall off a bridge, including ipsilateral hip, femoral shaft, pilon, and calcaneus fractures. He had previously undergone multiple surgical procedures, including ankle and hindfoot arthrodesis that resulted in malposition with pseudarthroses. (C, D) Initial postconversion radiographs show the ankle prosthesis in place. (E, F) The final radiographs at 59 months after conversion demonstrated the prosthetic alignment has been maintained. A subtalar arthrodesis has been performed and has healed.

Figure 6.

Location of bone cuts: (A) AP view of monoblock cutting guide placed with care to ensure the bone cuts will leave adequate malleolar bone to prevent fracture. (B) Lateral view of saw blades placed through the superior and inferior slits in the monoblock cutting guide to locate the site of the cuts. The inferior cut must not enter the subtalar joint posteriorly. (C) AP view after bone cuts have been made and the central bone segment has been removed. It is necessary at this point to complete the cuts between the talus and the malleoli both medial and lateral before any attempt is made to mobilize the ankle. AP, anteroposterior.

Figure 7.

Tibial-talar alignment: This is the angle measured between the longitudinal axis of the tibial prosthesis stem and the undersurface of the talar component on the AP radiograph. The measurement is made of the angle in the superior medial quadrant. An angle of 90 degrees defines perfect alignment. Measurements <90 degrees indicate a varus subluxation of the talus and measurements >90 degrees indicate valgus subluxation. Tibial-talar alignment for patient 1: (A) on the initial radiograph the angle is 92.6 degrees, and (B) on the final radiograph it is 102.2 degrees. Tibial-talar alignment for patient 15: (C) on the initial radiograph the angle is 93.5 degrees, and (D) on the final radiograph, it is 97.9 degrees.

Figure 8.

Longevity of conversion in intact and deficient fibula patients. Three intact fibula patients—3, 12, and 19—underwent prosthetic revision, with the time after conversion noted (X). Other minor procedures were conducted in patients 4, 8, 14, and 18.