Definition
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The utilization of 3D printing technology for combined total talus and navicular replacement with incorporation of subtalar joint fusion and total ankle replacement.
Indications
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Talar avascular necrosis
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Aseptic talar body collapse
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Failure of total ankle arthroplasty with talar subsidence/collapse
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Nonunion of talar fracture following open reduction and internal fixation (ORIF)
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Failed nonoperative management
Patient history and physical exam
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Detailed patient history must include history of trauma, arthritis, prior surgeries, and postoperative course.
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Duration, degree of dysfunction, and intensity of pain should be documented.
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Pain is predominately isolated to the ankle and hindfoot.
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Range of motion (ROM) should be assessed. Typically, the patient’s ankle and subtalar joint ROM is severely limited due to pain and crepitus ( Fig. 9.1 ).
• Fig. 9.1
On physical exam, the left ankle presented with pain throughout the range of motion. There was moderate global swelling around the ankle joint. The patient had pain to palpation to the medial and lateral gutters of the ankle as well as over the sinus tarsi and dorsal navicular regions. Her heel alignment was neutral with a plantigrade foot. She was neurovascularly intact. Her skin was warm, dry, and well perfused with well-healed incisions.
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Clinical alignment is determined with the patient weight bearing. The surgeon should note any deformities including equinus and varus/valgus malpositioning.
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The soft tissue envelope is examined for prior incisions, preulcerative lesions, global swelling, and signs of infection.
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Examine the neurovascular status for signs of neuropathy or vascular impairment.
Imaging and other testing
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Standard plain film weight-bearing radiographs should be obtained of the foot and ankle including anteroposterior (AP), mortise ankle views, as well as AP, oblique, and lateral ankle/foot views ( Fig. 9.2 ).
• Fig. 9.2
Bilateral weight-bearing radiographs were obtained preoperatively of a 74-year-old female who presented to the clinic with worsening left ankle pain. She had initially undergone bilateral total ankle arthroplasty with a mobile bearing implant. The left ankle implant failed and the patient underwent a revision total ankle arthroplasty with a fixed bearing implant utilizing a stemmed tibial component. One year later, the patient was referred to our office after postoperative radiographs revealed talar body aseptic collapse. Radiographs demonstrated severe loss of height of the left ankle. The talar component had completely subsided, resting on the superior aspect of the calcaneus. There was also fragmentation of the navicular bone and lateral gutter impingement.
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Advanced imaging is required for preoperative planning as well as engineering of the proposed custom implant. Bilateral CT scans should be obtained of both ankles. The custom implant is constructed based on the patient’s contralateral nonpathologic talus ( Fig. 9.3 ).
• Fig. 9.3
Preoperative ankle CT scan demonstrated complete talar subsidence with severe collapse of the talar component, severe subchondral cystic changes, as well as degeneration and fragmentation of the navicular bone. The tibial stemmed component was stable without signs of periprosthetic lucency.
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Infection must be ruled out and may be done so with laboratory studies, advanced imaging such as CT or MRI, joint aspiration, and bone biopsy.
Nonoperative management
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Bracing
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Nonsteroidal antiinflammatory medications
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Shockwave therapy
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Intra-articular injections
Traditional surgical management
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Bone-block pantalar arthrodesis
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Total talus replacement (TTR)
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Below-knee amputation
3D-printed implant design specifications and considerations
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Titanium alloy implant was designed and manufactured utilizing 3D printing technology incorporating a total talus and navicular bone into one combined custom implant. The size and dimensions of the implant were based on the contralateral, unaffected ankle, and hindfoot.
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Modifications were made in order to accommodate fixation through the custom implant with screws and staples.
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The fixation was designed to accept 5.5- to 6.5-mm headed screws and high-strength nitinol compression staples.
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The inferior aspect of the talar component and the distal aspect of the navicular component was engineered with plasma-coated lattice surfaces to aid in bony ingrowth at the proposed arthrodesis sites.
Surgical management with 3D-printed technology
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Proper stable positioning is vital during this procedure. The authors recommend a flat radiolucent operating table. A towel or bean bag hip bump is placed under the ipsilateral hip, maneuvering the operative lower extremity from an externally rotated position into a neutral position.
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A stack of blankets is placed under the operative lower limb prior to prepping and draping, elevating it above the contralateral leg, thus decreasing superimposition with the contralateral limb during lateral intraoperative fluoroscopic imaging.
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A standard large C-arm is recommended along with a thigh pneumatic tourniquet while the leg is prepped and sterilely draped above the level of the tibial tuberosity.
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Proper positioning allows for consistent intraoperative fluoroscopic images—AP ankle, mortise ankle, AP foot, Saltzman, and lateral foot/ankle views.
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Approach:
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A standard anterior ankle incision approach utilizing a 16-cm linear incision lateral to the tibialis anterior tendon.
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A superficial peroneal nerve is identified and retracted throughout the procedure.
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An interval is established between the extensor hallucis longus and the tibialis anterior tendon. It is important to preserve the tibialis anterior tendon sheath ( Fig. 9.4 ).
Related posts:
Historical perspectives on 3D printing
Material science for 3D printing in medicine
Distraction subtalar joint fusion using a custom 3D-printed implant
3D-printed solutions for avascular necrosis of the talonavicular joint
3D-printed total cuboid replacement for lateral column pathology
3D-printed custom hemi-talus replacement
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