Collapse of the talar body is a serious complication of total ankle arthroplasty. As the degree of osteoporosis increases, collapse is more likely, especially in patients with rheumatoid arthritis1. A paucity of revision implants, poor soft-tissue coverage and vascularity, and decreased bone stock make revision of a failed total ankle arthroplasty more challenging than revision of a failed hip or knee arthroplasty2. Kotnis et al.2 reported that revision is inadvisable in the presence of large osseous defects because they increase the chances of malalignment and instability, with resultant early failure. Johl et al.3 recommended a tibiotalocalcaneal arthrodesis with a short retrograde femoral nail as the treatment for aseptic loosening after a total ankle replacement with extensive bone loss because of the stability that is created and the low risk of pseudarthrosis. However, the major disadvantages of a tibiotalocalcaneal arthrodesis are a certain degree of shortening and a stiff foot4. In the case reported here, to restore the range of motion and to prevent degenerative changes in the distal joints such as the tarsometatarsal and metatarsophalangeal joints, we replaced a collapsed talar body and previous implants with a total talar prosthesis.
The patient was informed that data concerning the case would be submitted for publication, and she consented.
A fifty-six-year-old woman who had been managed for rheumatoid arthritis for twenty years presented to our institution because she had had increasing pain and loss of function in the left ankle for the previous year. Extensive changes in the ankle and subtalar joints that were typical of rheumatoid arthritis were verified with radiography, and a total ankle arthroplasty with cement (TNK Ankle; Japan Medical Materials, Osaka, Japan) and an arthrodesis of the subtalar joint with screw fixation were performed.
After the operation, the patient was managed with nonbiologic disease-modifying antirheumatic drugs by her family physician and had no subjective complaints of pain or instability. However, four years after the operation, she complained of slight pain and swelling in the left ankle and was referred to our hospital for further treatment. A lateral radiograph of the ankle joint revealed that collapse of the talar body had occurred, the arthrodesis of the subtalar joint had failed, and the fixation screw across the subtalar joint had been sheared by the talar component and had broken (Fig. 1). A total talar replacement was planned, but the implant insertion was considered to be difficult because of the shortening of the collapsed ankle joint and the poor skin quality that is known to be present in patients with rheumatoid arthritis. Therefore, the ankle was distracted with use of a Taylor Spatial Frame (Smith & Nephew, Memphis, Tennessee). At the same time, a total talar prosthesis was custom designed with use of the contralateral, normal talus as a reference on the basis of three-dimensional computed tomography images. The prosthesis was created with use of alumina ceramic, and a fixation peg was added to its calcaneal side (Figs. 2-A and 2-B). Gradual distraction was started at five days after application of the two-ring system of the external fixator at a rate of 0.8 to 1.0 mm/day. Twenty-two days were required to distract the ankle joint 18 mm (Fig. 3). The external fixator was retained until the tension in the distracted skin had been reduced. As a result, it was retained for an additional twenty-nine days. The total external fixation period was fifty-six days, and toe-touch weight-bearing gait was permitted during this period with use of the foot ring. The patient was managed in the hospital during this waiting period to avoid pin-site infections.
After removal of the external fixator, the ankle joint was exposed through the previous anterior incision. After removal of the implants and the collapsed talar body, fibrous tissue and necrotic material in the joint were excised. The tibial component was secured with use of bone cement. The subtalar joint was debrided, a peg hole was made on the posterior talar facet of the calcaneus, and the fixation peg of the talar body was inserted into the peg hole. The total talar prosthesis was inserted easily and was fixed to the calcaneus with use of bone cement. Postoperatively, the patient was managed with a below-the-knee cast for five weeks. She was prevented from bearing weight for one week and then gradually was allowed to progress from partial to full weight-bearing over the following week. After removal of the cast, range-of-motion exercises were initiated. At the two-year postoperative follow-up, the patient had no pain during normal activities and was able to walk without aids. Plain radiographs showed good alignment of both the tibial and talar prosthetic components, with no evidence of loosening (Figs. 4-A, 4-B, and 4-C). The range of ankle motion was from 15° of dorsiflexion to 10° of plantar flexion. The Japanese Society for Surgery of the Foot rheumatoid arthritis foot and ankle scale score5 was 65 of 100 points (Table I).
We introduce the total talar prosthesis as a new option for salvage of a failed total ankle arthroplasty. A total talar prosthesis can restore the range of motion in the ankle joint, prevent degenerative changes of the adjacent joint, and maintain leg length. In addition, we believe that preoperative use of an external fixator contributed to the good outcome in our patient by distracting the shortened tibiotalocalcaneal area and reducing skin tension.
Several reports on talar prostheses have been published in the past thirteen years. Magnan et al.6 reported on a forty-five-year-old man who underwent total ankle arthroplasty and insertion of a talar body prosthesis because of traumatic loss of the talus. Harnroongroj and Vanadurongwan7 reported a satisfactory result following talar body replacement with use of a metal prosthesis. Stevens et al.8 reported on a fourteen-year-old girl who underwent total talar replacement after an open talar dislocation. We previously reported a satisfactory result following talar body replacement with use of an alumina ceramic prosthesis for the treatment of idiopathic osteonecrosis of the talus9. However, we are not aware of any previous reports on the use of a total talar prosthesis for the salvage of a failed total ankle arthroplasty.
Some authors have recommended tibiotalocalcaneal arthrodesis with use of a retrograde nail for the treatment of a failed total ankle replacement associated with talar subsidence and extensive bone loss1,3,4. Although hindfoot stability and high rates of fusion have been reported in association with retrograde nail fixation3, a tibiotalocalcaneal arthrodesis following a failed total ankle arthroplasty causes loss of leg length, and the patient becomes unable to adapt to uneven ground, loses shock absorption, and has reduced propulsion4.
Remarkable pain relief and improvement in walking ability were obtained in our patient. We believe that this new method is feasible for restoring the function of the ankle joint in patients with a failed total ankle arthroplasty. Although our patient had an excellent result at the time of short-term follow-up, it is necessary to verify the long-term durability of the total talar prosthesis.