Complex Ankle and Hindfoot Arthrodesis Using Circular External Fixation
TAKE-HOME POINTS
- Ankle and hindfoot fusion using circular external fixation is a useful surgical technique in patients with diabetes, Charcot, osteomyelitis, deformity, and/or bone and soft tissue compromise in order to obtain solid bony fusion, stable limb alignment, and eradication of infection in cases of complex pathology.
- Deformity correction with osteotomies and meticulous joint preparation is required in order to obtain broad, cancellous bony surfaces for fusion with neutral alignment. Autograft from the distal fibula and/or medial malleolus can be combined with bone allograft to assist with joint fusion.
- The ankle and hindfoot are provisionally pinned into neutral coronal and sagittal alignment through the plantar surface of the foot using large K-wires prior to placement of the lower leg in the center of a circular 3-ring compression frame. Typically, 2 to 3 points of fixation are used per ring with a combination of half-pins and smooth wires.
- Ring attachments are built up or down to the level of the half-pins and wires in order to prevent pins and wires from bending, breaking, or causing iatrogenic deformity during tensioning. Crossing olive wires are used in the midfoot and calcaneus with dual tensioning devices to ensure an even pull on both sides of the foot.
- Dynamic or static compression struts are used to obtain 8 to 10 mm of compression across the ankle and hindfoot, followed by addition of an anterior foot ring to increase construct rigidity. Daily pin care is started 3 to 4 days after surgery and patients are kept non-weight-bearing for approximately 2 months in the frame with a total frame period of 3 to 8 months depending on bony healing on X-ray.
Patients with complex ankle and hindfoot deformity present a unique challenge to both nonoperative management and surgical reconstruction. Nonoperative management focuses on wound care, bracing, and immobilization using ankle-foot orthoses, total contact casts, and Charcot restraint orthotic walker boots for external stabilization. Fusion using the Ilizarov technique with circular fixation is a salvage limb-preservation procedure that has shown good results in select patient populations.1-5 Indications include post-traumatic, degenerative, and rheumatoid arthritis, osteomyelitis, tumors, neuromuscular conditions, and salvage of failed ankle and hindfoot procedures.6-9 Relative contraindications include wet gangrene, severe limb ischemia, and soft tissue compromise requiring urgent amputation. In addition, circular frames are not recommended in patients who are unable to comply with postoperative restrictions, and pin and wire care for the duration of frame placement because of personal, psychological, or socioeconomic reasons.
The Ilizarov technique of ring fixation provides dynamic, modular, and rigid fixation in multiple planes to control shear, bending, and rotational forces, and allows for early weight-bearing and postoperative adjustments as needed.10,11 Percutaneously placed half-pins and wires allow for solid fixation in the setting of both poor bone and soft tissue quality, and fusion can be achieved in the presence of active infection in a 1-stage procedure. The goal of ankle and hindfoot fusion using the Ilizarov technique is to achieve an infection-free, stable, plantigrade foot with neutral ankle alignment to allow for patient ambulation and return to activities of daily living.
Nonunion rates with circular fixation are reported to be as high as 16% to 54%, due to medical comorbidities, such as smoking, peripheral vascular disease, and Charcot neuroarthropathy.1Charcot, in particular, is a risk factor for nonunion as patients lack protective sensation, and have a higher rate of wound dehiscence, noncompliance with weight-bearing precautions, pin site infections, and frame breakage. In these patients, tibiotalocalcaneal (TTC) arthrodesis is preferred over the isolated ankle, or subtalar fusion to both provide a stable platform for ambulation and reduce the incidence of adjacent joint breakdown. Common complications of the Ilizarov technique include pin site infections, wire breakage, talar necrosis, and tibial stress fractures after frame removal.1,2,6,11-13 Circular frames are typically maintained for 3 to 8 months, until solid fusion is achieved radiographically. Frames are removed in the operating room with the concurrent examination of the fusion sites under anesthesia followed by a period of protected weight-bearing in a cast or tall controlled ankle motion (CAM) boot.
This article reviews several technical details, tips, and tricks that can help improve the intraoperative and postoperative outcomes of combined ankle and hindfoot arthrodesis using the Ilizarov technique with circular external fixation.
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