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A Closer Look At A Total Talar Replacement And Ankle Arthroplasty

Discussing a case of recalcitrant pain for a patient three years after an open left talar neck fracture dislocation and failed surgeries, this author shares insights and pearls on performing a total talar replacement and ankle arthroplasty. 

Foot and ankle avascular necrosis (AVN) is uncommon with about 15,000 cases per year in the United States.1 Avascular necrosis occurs when the blood supply is lost or severely diminished to the diaphyseal or epiphyseal portion of the bone, and the underlying cancellous bone weakens and collapses. Also referred to as osteonecrosis, avascular necrosis can either be traumatic or atraumatic in nature due to long-term steroid use, alcoholism, chemotherapy or sickle cell anemia. Avascular necrosis most commonly affects the hip and femur, but it may also occur in the humerus, knee and ankle.1  

Talar avascular necrosis can be significantly disabling and pose a major problem for the average foot and ankle surgeon. Diagnosis is difficult and treatment is even more challenging. The most common etiology of talar avascular necrosis is a talar body or neck fracture. The combination of a precarious blood supply with a complex fracture creates a serious problem.

When A 49-Year-Old Patient Has Continued Pain After Multiple Surgeries For A Talar Neck Fracture

A 49-year-old healthy male sustained an open left talar neck fracture dislocation while rock climbing approximately three years prior to presenting to our office in Phoenix, Arizona. 

Initial immediate treatment of the injury involved a spanning external fixator and closed reduction at an outside facility. Subsequent surgeries included a free tissue transfer to the medial ankle, multiple incision and drainage procedures, and core decompression of the talar body. 

The patient is a non-smoker and takes no medications. He presented to our office with ongoing pain, restricted ankle range of motion, a healed skin graft over the medial malleolus and a significantly antalgic gait. Repeat weightbearing radiographs and magnetic resonance images showed continued talar body collapse. 

We discussed his options including tibiotalar or tibiotalocalcaneal joint fusion, in an effort to create a solid fusion mass and maintenance of limb length, or amputation, which he adamantly declined. A hindfoot or ankle fusion has long been the “gold standard” for end-stage talar avascular necrosis. We also discussed a custom talar prosthesis made of cobalt chromium as a newer, more advanced option. This would allow for maintenance of ankle range of motion while sparing the peritalar joints, maintaining limb length and ultimately a more normal gait cycle. (See first two images above.)

Understanding The History And Fabrication Of The Talar Body Prosthesis

First reported in 1997 by Harnroongroj and Vanadurongwan, use of the talar body prosthesis is controversial.2 Several adaptations have led surgeons to manage end-stage avascular necrosis with a recreation of the talar head, neck and body via third-generation total talus replacements that incorporate 3D printing technologies.3

The aforementioned patient and former rock climber consented to a total talar replacement and ankle arthroplasty. This would involve replacing the distal plafond with the tibial component of a total ankle arthroplasty and utilizing a custom total talus replacement as well. Employing computed tomography (CT), we scanned the contralateral limb for congruency and sent the scan to the manufacturer for design and production. 

The design of the implant takes approximately two to four weeks. The implant is an example of a patient-centric custom device, which is manufactured based on the order of a physician. The process begins with receiving the patient's CT scan (in this case the contralateral scan), which the manufacturer loads into software that allows for generation of a 3-D rendering of the patient's anatomy. 

The surgeon and design team discuss all design specifications and factors over an Internet web portal that acts as a virtual surgery of sorts. Restor3d® designs the device offline and generates a design proposal with all implant details before sending it to the surgeon for his or her approval. Once the surgeon approves the design, Restor3d prints the implant at its facility. The implant is subsequently sterilized at the hospital prior to implantation. The final implant comes with a nominal (or normal) size as well as smaller and larger sizes for trials.

The gold standard for load-bearing articulating surfaces, cobalt chrome is common in total hip and knee arthroplasty components due to the low coefficient of friction and reduced wear. In the case of a total talus replacement, cobalt chrome is advantageous as it reduces wear with the adjacent bones of the foot that we want to keep intact to preserve motion in the joint (i.e. subtalar and talonavicular joints). In this case, the patient had distal tibial plafond degeneration which necessitated the arthroplasty.

Reviewing The Surgical Technique And Postoperative Protocol 

The technique is relatively straightforward if one is familiar with ankle arthroplasty. The surgeon makes an anterior ankle incision between the tibialis anterior and extensor hallucis longus tendons.  One then deepens the incision to the ankle capsule and reflects the capsule. The extensor hallucis longus protects the neurovascular structures. If the patient requires an ankle arthroplasty, the surgeon performs the procedure at this time as per the technique guide for the specific implant. 

The surgeon proceeds to carefully dissect the talar body circumferentially with a meniscotome. This technique allows placement of a threaded Steinmann pin or Schanz pin in the talar body to facilitate complete removal. One subsequently removes the talar neck from the talonavicular joint. This technique allows the medial and lateral capsule to maintain integrity, and avoids any inadvertent neurovascular damage. After trialing the appropriate size, the surgeon inserts the total talus replacement and proceeds to insert the tibial portion of the arthroplasty system. He or she then closes the capsule and skin in layers. 

At two weeks postoperatively, the patient began weightbearing in a CAM boot. Physical therapy began at four weeks post-op with transition to a supportive shoe with a lace-up ankle brace at six to eight weeks. The patient, now three months post-op, reports little to no pain in his ankle joint, and is very pleased with the results (see postoperative radiographs in the bottom two images above). As one can see in the case of this patient, total talus replacement and 3-D printing are allowing surgeons to think outside the box, and treat difficult to treat pathologies like never before.  

Dr. McAlister is board-certified by the American Board of Foot and Ankle Surgery, and is in private practice in Phoenix, Ariz. He completed an advanced foot and ankle surgical fellowship at the Orthopedic Foot and Ankle Center in Columbus, OH. 

Online Exclusives
Jeffrey McAlister, DPM, FACFAS
References
  1. Jones LC, Mont MA. Osteonecrosis of bone. UpToDate. Available at: http://www.uptodate.com/contents/osteonecrosis-avascular-necrosis-of-bone . Published September 22, 2014. Accessed February 12, 2020.
  2. Harnroongroj T, Vanadurongwan V. The talar body prosthesis. J Bone Joint Surg Am. 1997;79(7):1313-1322. 
  3. Tracey J, Arora D, Gross CE, Parekh SG. Custom 3D-printed total talar prostheses restore normal joint anatomy throughout the hindfoot. Foot Ankle Spec. 2019;12(1):39-48.
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