Pearls On Using External Fixation For Charcot Hindfoot And Ankle Deformity

Mindful of the debilitating effects of Charcot foot in patients with diabetes, these authors discuss the use of external fixation for a tibio-calcaneal fusion in a neuropathic patient with a Charcot ankle valgus deformity.

Diabetic Charcot foot deformity is a progressive, disfiguring and debilitating condition characterized by joint subluxation and dislocation, fracture, and extensive osseous destruction. The goal of surgical intervention is to achieve a stable, plantigrade foot that will allow the use of proper footwear, reducing the risk of re-ulceration.

Surgeons have used intramedullary fixation/arthrodesis in the treatment of rearfoot/ankle deformity of the neuropathic Charcot patient. One of the major complications with intramedullary fixation is nonunion of the arthrodesis site(s), which researchers have attributed to the bone quality and difficulty obtaining compression and stability across the arthrodesis site.^1,2 Multiple authors have reported complication rates (as high as 69 percent) with the use of internal fixation.^1,3,5,6 Common complications are infection, hardware failure requiring removal, recurrent ulceration, fracture, subsequent surgical procedures and recurrence of the deformity.^2-6 In addition, postoperative amputation rates reportedly range from 0 to 15 percent within this patient population due to an unstable hindfoot/ankle leading to limb loss.^1,3,4

External fixation is gaining popularity as an alternative method of successful treatment for the correction of the hindfoot and ankle in a patient with Charcot neuropathy. We present a case study demonstrating the use of external fixation for a tibiocalcaneal fusion to address a Charcot ankle valgus deformity with associated dislocation in a neuropathic patient.    

A Closer Look At The Surgical Technique For Tibiocalcaneal And Tibio-Talocalcaneal Arthrodesis With Ex-Fix

Make a transverse lateral incision between the anterior and posterior borders of the tibia in anticipation of limb shortening. Expose the fibula with the use of atraumatic dissection techniques. If there is no concern for osteomyelitis, use a small acetabular reamer to ream the fibula, the lateral wall of the talus and the lateral cortex of the tibia. Save the reamed bone fragments and use them later for bone graft. Our technique of fibular reaming serves a duel role of providing autograft bone while obtaining access to the necessary joints for arthrodesis. When there is any question of osteomyelitis in the fibula, resect the fibula, culture it and send it to pathology.

Then identify the ankle joint and subtalar joint articulations, and prepare them for arthrodesis with the use of curettes and a patella saw blade. Also prepare to resect the subchondral bone plate to expose bleeding, healthy, cancellous bone. When resecting and preparing these joints, ensure minimal bone resection to avoid a further loss in limb length.

While examining the limb with the use of fluoroscopy, the surgeon realigns the foot at the tibia. One can achieve this by compressing the cut surfaces of the calcaneus, talus and tibia, externally rotating the foot to the limb, obtaining a neutral to valgus heel position, and maintaining a plantigrade foot position. The surgeon should also translate the foot posteriorly or anteriorly, and medially or laterally as needed to achieve proper alignment.

Then insert a 1.8 mm K-wire from the plantar aspect of the foot, beginning at the calcaneus and extending through the talus and into the tibia. Check the foot to tibia alignment on the axial, lateral and anteroposterior fluoroscopy views. The foot should be plantigrade, beneath the tibia and externally rotated 10-15 degrees with the heel in neutral. Place local fibular, tibial and talar bone autograft along the anterior and lateral aspect of the arthrodesis sites, bridging the tibia, talus and calcaneus.

Apply a two-ring fixation block (orthogonal to the tibial axis) to the tibia by using 1.8 mm wire(s) and/or 6 mm half-pin(s). One should apply the tibial external fixation construct an ample distance proximal to the ankle joint to ensure ease of access to the ankle joint. The greater you angle the half-pins and wires to each other, the greater the strength of fixation. In addition, the greater distance the fixation spans a bone segment, the stronger the fixation will be.

Mount a closed U foot ring parallel to the sole of the foot by using two crossed calcaneal wires: one perpendicular wire below the ring, medial to lateral, and one obliquely placed wire above the ring, medial to lateral. Insert one midfoot wire across the cuneiform cuboid level, apply tension and fix the wire. Proceed to insert two talar 1.8 mm wires, one medial to lateral through the talar neck and the other from anteromedial in the neck of the talus to posterolateral to the Achilles tendon. Attach three threaded rods from the tibial ring to the foot ring and use these for compression of the ankle and/or subtalar joint to achieve fusion. All of the smooth wires are 1.8 mm in diameter and should have tension to 110 kg. Maintain the external fixator for approximately three months. After fixator removal, one can allow partial weightbearing in a cast for an additional month.

In Conclusion

The use of external fixation in the treatment of the complex neuropathic patient provides a source of rigid fixation and stabilization in a patient population with poor bone quality and delayed healing potential.

Advantages include:

• single-stage treatment in the presence of osteomyelitis or ulceration;

• the allowance of immediate weightbearing with an assisted device in a poorly adherent population; and

• the allowance of subsequent dynamic compression and adequate surface area of bone to bone contact while avoiding retained hardware.^1,3,5

In addition, the versatility of external fixation is advantageous in the setting of the abnormal anatomy in Charcot patients in comparison to intramedullary nailing devices that have a set screw placement and alignment.

Therefore, one can treat Charcot neuropathy of the hindfoot and ankle successfully with the use of external fixation, yielding a high rate of limb salvage.

Dr. Knight is a Clinical Fellow with the Foot and Ankle Deformity Correction Fellowship at the International Center for Limb Lengthening at the Rubin Institute for Advanced Orthopedics within the Sinai Hospital of Baltimore.

Dr. Pugh is a Clinical Fellow with the Foot and Ankle Deformity Correction Fellowship at the International Center for Limb Lengthening at the Rubin Institute for Advanced Orthopedics within the Sinai Hospital of Baltimore.

Dr. Lamm is the Head of Foot and Ankle Surgery and the Director of the Foot and Ankle Deformity Correction Fellowship at Sinai Hospital of Baltimore. He is also the Chief of the Limb Preservation Program and the Co-Director of the Veterans Affairs/Sinai Podiatric Surgical Program at the International Center for Limb Lengthening at the Rubin Institute for Advanced Orthopedics within the Sinai Hospital of Baltimore.

References

1. Zgonis T, Roukis TS, Lamm BM. Charcot foot and ankle reconstruction: current thinking and surgical approaches. Clin Podiatr Med Surg. 2007; 24(3):505-517.
2. Paley D, Herzenberg JE. Principles of Deformity Correction. Springer-Verlag, Berlin, 2002.
3. Lamm BM, Paley D. Deformity correction planning for hindfoot, ankle, and lower limb. Clin Podiatr Med Surg. 2004; 21(3):305-326.
4. Caravaggi C, Cimmino M, Caruso S, Dall Noce S. Intramedullary compressive nail fixation for the treatment of severe Charcot deformity of the ankle and rearfoot. J Foot Ankle Surg. 2006; 45(1):20-24.
5. Lamm BM, Gottlieb HD, Paley D. A two-stage percutaneous approach to Charcot diabetic foot reconstruction. J Foot Ankle Surg. 2010; 49(6):517-522.
6. Mendicino RW, Lamm BM, Catanzariti, AR, Statler TK, Paley D. Realignment arthrodesis of the rearfoot and ankle: a comprehensive evaluation. J Am Podiatr Med Assoc. 2005; 95(1):60-71.