Fig. 1 A CT scan of an ankle showing talar collapse due to osteonecrosis. The distal tibial and subtalar articulations remain intact.
Courtesy of mark S. Myerson, MD

AAOS Now

Published 8/1/2016
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Mark S. Myerson, MD

Total Talus Replacement Shows Promising Results in Treating Talar Osteonecrosis

The management of osteonecrosis of the talus depends on the stage and severity of the disease process. For early osteonecrosis without collapse, core decompression or vascularized bone grafts have been used to halt progression and alleviate symptoms.

Most treatments for managing more severe talar osteonecrosis—in which collapse has occurred—have included arthrodesis of one type or another, depending on the severity of the necrosis (Fig. 1). These options include primary tibiotalocalcaneal (TTC) fusion or tibiocalcaneal fusion with excision of the talar body. TTC fusion with resection of the body of the talus and intercalary structural autograft or allograft has also been reported but with dismal fusion rates (ranging from 50 percent to 58 percent).

An alternative technique for managing severe osteonecrosis of the talus is replacing the talar body with a prosthesis, leaving behind the neck of the talus. This technique was first reported by Thos Harnroongroj, MD, and Thossart Harnroongroj, MD, with good long-term results. A similar approach with resection of the body of the talus only was reported by Akira Taniguchi, MD, and colleagues, but this approach has been replaced with removal of the entire talus and replacement of a ceramic talar prosthesis.

Recently, this implant became available in the United States, after 4Web Medical (Frisco, Texas) developed a technique for designing a patient-matched, custom talar prosthesis. The process uses computed tomography (CT) scans to create three-dimensional (3D) computer bone models of both the diseased and the unaffected ankle joints. The normal talus shape is mirrored to shape the talar replacement (Fig. 2). The implant is created from medical-grade metallic alloy, using 3D printing technology (Fig. 3, 4). Under U.S. Food and Drug Administration guidelines, the implant is considered a custom device.

The results of talar body replacement and complete talus replacement have been reported in two series. According to the first report, 33 talar body prostheses were implanted with the use of a transmalleolar surgical approach from 1974 to 2011. Follow-up ranged from 10 to 36 years. At the time of final follow-up, 28 of the 33 prostheses were still in place; the remaining five had failed within 5 years of surgery. The researchers concluded that, although early prosthesis failure may occur, survival of the talar body prosthesis can provide satisfactory ankle and foot function.

The second report examined 55 prostheses inserted in 51 patients between 2005 and 2012; patients were followed for an average of 52.8 months. Pain scores improved significantly and no patients required revision.

I recently had the opportunity to talk with lead author Dr. Taniguchi of the department of orthopaedic surgery at Nara Medical University, Nara, Japan, about the procedure. Following is a summary of our conversation.

What you should know
Dr. Myerson:
Your team has been performing the talar body prosthesis surgery since 1999. What are your current indications for this procedure?

Dr. Taniguchi: Any patient with severe osteonecrosis of the talus may be a candidate.

Dr. Myerson: Do you obtain a CT scan or an MRI preoperatively to plan the surgery?

Fig. 1 A CT scan of an ankle showing talar collapse due to osteonecrosis. The distal tibial and subtalar articulations remain intact.
Courtesy of mark S. Myerson, MD
Fig. 2 A CT scan of the normal ankle is used to create a mirrored model of the diseased talus.
Courtesy of Mark S. Myerson, MD
Fig. 3 A custom-sized matched talus is implanted.
Courtesy of Mark S. Myerson, MD
Fig. 4 A lateral radiograph of the talar replacement.
Courtesy of Mark S. Myerson, MD

Dr. Taniguchi: Yes, we obtain both modalities. The CT scan is necessary for designing the custom-made implant and the MRI is necessary for diagnosing the talar necrosis.

Dr. Myerson: Do the articular surfaces of the tibia and the calcaneus need to be healthy for a good outcome?

Dr. Taniguchi: Yes, I think so. But if the patient has degenerative changes in the articular surface of the distal tibia, we replace it with tibial component of the TNK (Takakura Nara Kyocera) ankle (KYOCERA Medical Corporation, Osaka, Japan). If the patient has degenerative changes in the posterior articular facet of the calcaneus, we design the implant with a peg for cement fixation to the calcaneus.

Dr. Myerson: Your team originally performed the procedure by removing the body of the talus only, leaving the neck intact. Why have you since changed your approach to remove the entire talus?

Dr. Taniguchi: We had some cases with loosening at the fixation site (neck of the talus) after replacement with the talar body prosthesis. So we began using the total talar prosthesis, and this is all we use now.

Dr. Myerson: Do you initiate weight bearing and rehabilitation immediately following surgery?

Dr. Taniguchi: Partial weight bearing is allowed after surgery, and is gradually increased to full weight bearing by 3 weeks after surgery. A short leg cast is fitted and worn for the first 3 weeks postoperative, followed by continuous use of a soft, multistrap, ankle orthosis for more than a month thereafter.

Dr. Myerson: The range of motion (ROM) of the ankle and subtalar joint is not always recovered following this procedure. What surgical and rehabilitation treatment tips can you give us to maximize motion?

Dr. Taniguchi: We do not have much trouble with restriction of the ankle and subtalar joints. Passive ROM exercise is started just after removal of the cast (3 weeks after surgery).

Mark S. Myerson, MD, is medical director of the Institute for Foot and Ankle Reconstruction at Mercy Medical Center in Baltimore.

References:

  1. Jeng CL, Campbell JT, Tang EY, Cerrato RA, Myerson MS: Tibiotalocalcaneal arthrodesis with bulk femoral head allograft for salvage of large defects in the ankle. Foot Ankle Int 2013;34(9):1256–1266.
  2. Berkowitz MJ, Clare MP, Walling AK, Sanders R: Salvage of failed total ankle arthroplasty with fusion using structural allograft and internal fixation. Foot Ankle Int 2011;32(5):S493–502.
  3. Harnroongroj T, Harnroongroj T: The talar body prosthesis: Results at ten to thirty-six years of follow up. J Bone Joint Surg Am 2014;96(14):1211–1218.
  4. Taniguchi A, Takakura Y, Tanaka Y, et al: An alumina ceramic total talar prosthesis for osteonecrosis of the talus. J Bone Joint Surg Am 2015;97(16):1348–1353.