Bradley M. Lamm and Dror Paley
BACKGROUND
The aftereffects of Charcot joint disease include joint subluxation or dislocation, loss of bone quality, and osseous malalignment (FIG 1).
As a result of the deformed Charcot foot position, aberrant weight-bearing forces and altered muscle–tendon balance increase the risk for ulceration, infection, and amputation.
When treating the Charcot neuropathic foot, the best results are achieved when intervention is initiated as early as possible.
In acute Charcot neuroarthropathy, the goal of treatment is to stabilize the foot. Total contact casting is the traditional treatment.
In this patient population, it is extremely difficult to maintain non–weight-bearing status for multiple reasons, including muscle atrophy, obesity, and diminished proprioception.
Non–weight-bearing immobilization for months produces osteopenia of the involved foot and increased weight-bearing forces on the contralateral limb.
The sequelae can make it difficult for subsequent surgery on the involved foot and can lead to ulceration and Charcot neuroarthropathy in the contralateral foot.
In chronic Charcot neuroarthropathy, the goal of treatment is to realign the soft tissue and osseous structures. In general, surgeries are aimed at realignment, but in these extremely deformed feet, acute realignment is challenging.
Traditionally, acute realignment procedures such as Achilles tendon lengthening, ostectomy, débridement, osteotomy, arthrodesis, and open reduction with internal fixation (plantar plating) have been attempted.4
Acute correction via open reduction with application of static external fixation has also been reported.2
More recently, internal fixation methods have been augmented or replaced by external fixation as a means of static fixation of a Charcot reconstruction.6
Here, we present a new two-stage minimally invasive gradual correction method with the use of external fixation for acute and chronic Charcot reconstruction, which was developed by the senior author (D.P.).3
Gradual deformity correction with external fixation is preferred for large-deformity reductions of the dislocated Charcot joints of the foot. Correction with external fixation allows for gradual, accurate realignment of the dislocated or subluxated Charcot joints.
FIG 1 • Midfoot Charcot neuroarthropathy deformity (Eichenholtz stage II, unstable, with lateral ulceration and previous resection of the fourth and fifth metatarsals). A. AP radiograph shows midfoot adduction deformity. B. Lateral radiograph shows rocker-bottom and equinus deformities. Note the dorsal displacement of the forefoot and the break in Meary's angle. Lateral still images, obtained by using video fluoroscopy, confirm the instability of the midfoot Charcot deformity, demonstrating significant forefoot dorsiflexion (C) and plantarflexion (D). (Copyright 2008, Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore.)
SURGICAL TREATMENT
The goals of surgical intervention for the Charcot foot are to restore anatomic alignment, impart stability, prevent amputation, prevent foot shortening, and allow the patient to be ambulatory.
Historically, open reduction with internal fixation was the mainstay for treatment of Charcot foot deformities.
Large open incisions were made to remove the excess bone, reduce the dislocated bone, and stabilize with internal fixation (screw fixation or plantar plating).
These invasive surgical procedures typically resulted in shortening of the foot or incomplete deformity reduction and occasionally resulted in neurovascular compromise, incision healing problems, infection, and the use of non–weight-bearing casts and boots.
In cases of tarsometatarsal Charcot deformity, open reduction is advantageous.
Typically, Charcot neuroarthropathy of the tarsometatarsal joints is associated with mild to moderate deformities because the tarsometatarsal joints are structurally interlocked.
Acute realignment is achieved by performing a wedge resection or open reduction with fusion and internal fixation to produce a stable foot.
In acute Charcot neuroarthropathy, a static external fixation is placed to stabilize the Charcot process. The smooth wire fixation for the external fixation is applied so as to avoid the “hot,” or Charcot, joint region of the foot.
The static fixator is applied strategically so gradual realignment can begin after the acute phase of Charcot has passed. Thus, the external fixator serves a dual purpose by stabilizing both the acute Charcot joint and the subsequent realignment of the dislocated osseous anatomy.
Once the bony anatomy is realigned, the external fixation is removed and a formal minimally invasive fusion of the Charcot joint is performed. Rigid intramedullary metatarsal screws are used to maintain the fusion.
Chronic stable or coalesced Charcot foot deformities require an osteotomy for correction of the deformity. We prefer a percutaneous Gigli saw osteotomy technique.
Midfoot osteotomies can be performed across three levels (ie, talar neck and calcaneal neck, cubonavicular osseous level, and cuneocuboid osseous level).
Performing Gigli saw osteotomy across multiple metatarsals should be avoided because of the neurovascular injury.3
For an unstable or an incompletely coalesced Charcot foot, correction can be obtained through gradual distraction.
Despite the radiographic appearance of coalescence (superimposition of the dislocated or fragmented pedal bone due to the Charcot process), most Charcot deformities can undergo distraction without osteotomy to realign the pedal anatomy.
An Achilles tendon lengthening is performed and held in a neutral position with the external fixation. This restores the normal calcaneal pitch and hindfoot position.
Then, under fluoroscopy, acute forefoot reduction is attempted and, if possible, fixation with intermedullary metatarsal screws is carried out.
Acute reduction of the forefoot is rarely successful, however. If the forefoot cannot be acutely reduced, an external fixator is used to hold the hindfoot position while the forefoot is lengthened and realigned.
Approach
This first stage of the procedure consists of osseous realignment of the forefoot on a fixed hindfoot, which is achieved with an external fixator using distraction.
After realignment, the correction is maintained by minimally invasive arthrodesis of the Charcot joint and is fixed with percutaneous intramedullary metatarsal screws.
TECHNIQUES
STAGE 1
Plate Fixation and Achilles Tendon Lengthening
The first stage consists of osseous realignment achieved by performing an acute Achilles tendon lengthening and gradual soft tissue distraction with the Taylor spatial frame (TSF). Patient adjustments of the TSF (forefoot 6 × 6 butt frame) provide gradual relocation of the forefoot on the fixed hindfoot.
The distal tibia, talus, and calcaneus are fixed with two U-plates joined and mounted orthogonal to the tibia in both the anteroposterior (AP) and lateral planes.
The U-plate is affixed to the tibia with one lateromedial 1.8-mm wire and two or three additional points of fixation (combination of smooth wires or half-pins).
For additional stability, a second distal tibial ring can be added, creating a distal tibial fixation block.
It is essential to fix the hindfoot in a neutral position; an Achilles tendon lengthening typically is required to achieve a neutral hindfoot position. We prefer performing percutaneous Z-lengthening of the Achilles tendon.
With the hindfoot manually held in a neutral position, the U-plate is fixed to the calcaneus with two crossing 1.8-mm wires. A 1.8-mm mediolateral talar neck wire also is inserted and fixed to the U-plate.
External Fixation Setup
Two 1.8-mm stirrup wires are inserted through the osseous segment just proximal and distal to the Charcot joints.
The stirrup wires are bent 90 degrees just outside the skin to extend and attach but are not tensioned to their respective external fixation rings distant from the point of fixation. Stirrup wires capture osseous segments that are far from an external fixation ring, thereby providing accurate and precise Charcot joint distraction.
A full external fixation ring is then mounted to the forefoot by two 1.8-mm crossing metatarsal wires and the aforementioned distal stirrup wire.
Digital pinning often is required whereby the digital wires (1.5 or 1.8 mm) are attached to the forefoot ring.
Finally, the six TSF struts are placed and final radiographs obtained (AP and lateral views of the foot to include the tibia; TECH FIG 1).
Orthogonal AP and lateral view fluoroscopic images are obtained of the reference ring; these images provide the mounting parameters that are needed for the computer planning.
The choice of which ring (distal or proximal) to use as the reference ring is based on the surgeon's preference; typically, a distal reference is chosen for foot deformity correction.
Superimposition of the reference ring on the final films is critical for accurate postoperative computer deformity planning.
Computer planning of the TSF is a critical part of this procedure. The surgeon enters the deformity and mounting parameters into an Internet-based software (www.spatialframe.com) that produces a daily schedule for the patient to perform adjustments on each of the six struts. The rate and duration of the patient's schedule is controlled by the surgeon's data entry.
The patient returns for clinical and radiographic followup in the office weekly or biweekly.
TECH FIG 1 • A. Immediate postoperative AP radiograph shows midfoot adduction (20 degrees) in the patient shown in Figure 1. B. Immediate postoperative lateral radiograph shows plantarflexion of the forefoot (10 degrees). The change in forefoot position as compared with the preoperative radiographs is due to the acute manipulation intraoperatively. The stirrup wires (90-degree bent wires that are not tensioned) are placed adjacent to the region of distraction and realignment (midfoot). These stirrup wires ensure focused distraction. Note the TSF planning lines and reference points. C,D. Clinical photographs show the TSF (forefoot 6 × 6 butt) applied. In C, note the delta configuration of the tibial half-pins and the build-out (two-hole plate) off the distal foot ring to allow for soft tissue clearance. In D, note the stirrup wires adjacent to the distraction region. (Copyright 2008, Rubin Institute for Advanced Orthopedics, Sinai Hospital for Baltimore.)
STAGE 2
Frame Removal and Arthrodesis
Gradual distraction for realignment of the dislocated Charcot joints is obtained in approximately 1 to 2 months. After gradual distraction with the TSF has realigned the anatomy of the foot (TECH FIG 2A), the second stage of the correction is performed.
The external fixator is removed simultaneously with performance of minimally invasive arthrodesis of the affected joints using percutaneous insertion of internal fixation (TECH FIG 2B).
Before frame removal, small transverse incisions (2 to 3 cm in length) are made overlying the appropriate joints to perform cartilage removal and joint preparation for arthrodesis.
TECH FIG 2 • A. Lateral view radiograph after 1 month of gradual TSF correction shows a normal (or zero) Meary's angle and distraction of the midfoot in the same patient. The dorsal foot ulcer has healed and the foot is correctly positioned. B. Immediately after removal of the external fixator, a minimally invasive fusion of the midtarsal joint was performed to prevent future Charcot foot collapse. A weight-bearing AP radiograph shows two percutaneous intramedullary metatarsal screws and a lateral column screw that were inserted for stabilization of the fusion of the midtarsal joint. Note the accurate anatomic reduction. (Copyright 2008, Rubin Institute for Advanced Orthopedics, Sinai Hospital for Baltimore.)
Minimally invasive arthrodesis is easily performed because the Charcot joints are already distracted.
Under fluoroscopic guidance, the guidewires for the large-diameter cannulated screws are inserted percutaneously through the plantar skin incision into the metatarsal head by dorsiflexing the metatarsophalangeal joint.
After the lateral and medial column guidewires (fourth, first, and second metatarsals) are inserted to maintain the corrected foot position, the frame is removed and the foot is reprepped. partially threaded screws for compression of the arthrodesis site and one central (second metatarsal) fully threaded screw for additional stabilization.
These screws span the entire length of the metatarsals to the calcaneus and talus, provide compression across the minimally invasive arthrodesis site, and stabilize adjacent joints. The intramedullary metatarsal screws cross an unaffected joint, the Lisfranc joint, thereby protecting the Lisfranc joint from experiencing a future Charcot event.
The minimally invasive incisions are then closed, and a well-padded L and U splint is applied.
At the time of hospital discharge, the patient is placed in a non–weight-bearing short leg cast for 2 to 3 months, and then gradual progression to weight bearing is achieved. Thus, the entire treatment is completed in 4 to 5 months (TECH FIG 3).
Intramedullary Screw Fixation and Closure
Typically, three large-diameter cannulated intramedullary metatarsal screws are inserted: medial and lateral column
TECH FIG 3 • A postoperative lateral view radiograph from the same patient shows a healed plantigrade foot with intact intramedullary metatarsal screws. Note the accurate anatomic reduction, fusion of the involved Charcot joint (midtarsal joint), protection of the adjacent Lisfranc joints (stability via screw fixation), ridged internal stability, restoration of foot length, healed ulceration, and preservation of the subtalar and ankle joints. (Copyright 2008, Rubin Institute for Advanced Orthopedics, Sinai Hospital for Baltimore.)
PEARLS AND PITFALLS
External fixation construction is challenging because of the small size of the foot. When applying the forefoot 6 × 6 butt frame, it is important to mount the U-plate on the hindfoot as posterior as possible and the forefoot ring as anterior as possible. The greater the distance between the forefoot and hindfoot ring, the more space for the TSF struts.
Bone segment fixation is important; otherwise, failure of osteotomy separation or incomplete anatomic reduction occurs. Small wire fixation is preferred in the foot because of the size and consistency of the bones.
When treating a patient with neuropathy, construction of extremely stable constructs is of great importance. External fixation for Charcot deformity correction should include a full distal tibial ring with a closed foot ring.
OUTCOMES
We have performed this gradual distraction technique for the past 5 years and have achieved good to excellent success in more than a dozen feet.
Feet were operated on at various stages of Charcot deformity (Eichenholtz stages I, II, and III).
When comparing the average change in preoperative and postoperative radiographic angles, the transverse plane talar–first metatarsal angle, sagittal plane talar–first metatarsal angle, and calcaneal pitch angle were all found to be significantly altered.
Most notably, no deep infection, no screw failure, and no recurrent ulcerations occurred and no amputations were necessary during the past 5 years.
Gradual Charcot foot correction with the TSF plus minimally invasive arthrodesis has constituted a safe and effective treatment.
Our results are promising. The advantages of our method when compared with the resection and plating method reported by Schon4 or the resection and external fixation method reported by Cooper1 are preservation of foot length (no bone resection), accurate anatomic realignment of soft tissues and bone, and a stable foot. Furthermore, our method is much less invasive and allows for partial weight bearing.
ACKNOWLEDGMENT
We thank Amanda Chase, MA, for her editing assistance, and Alvien Lee for his photographic expertise.
REFERENCES
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· Jolly GP, Zgonis T, Polyzois V. External fixation in the management of Charcot neuroarthropathy. Clin Podiatr Med Surg 2003; 20:741–756.
· Paley D. Principles of Deformity Correction. Rev ed. Berlin: SpringerVerlag, 2005.
· Schon LC, Easley ME, Weinfeld SB. Charcot neuroarthropathy of the foot and ankle. Clin Orthop Relat Res 1998;349:116–131.
· 5. Trepman E, Nihal A, Pinzur MS:. Current topics review: Charcot neuroarthropathy of the foot and ankle. Foot Ankle Int 2003;6:46–63.
· Wang JC, Le AW, Tsukuda RK. A new technique for Charcot's foot reconstruction. J Am Podiatr Med Assoc 2002;92:429–436.