Emerging Concepts In Fixation For Charcot Midfoot Reconstruction

Given the challenges with reconstructive surgery for patients with Charcot neuroarthropathy, this author reviews the different fixation options and offers step-by-step pearls on the use of intramedullary screw fixation.

Charcot neuroarthropathy is a dynamic non-infectious destructive process, which can affect the bones and joints of the foot and the ankle. Diabetes with pronounced neuropathy is the most common etiology of this condition but any neuromuscular disorder that damages the peripheral nerves can result in Charcot foot pathology.

   This includes multiple sclerosis, syringomyelia, cerebral palsy and Charcot-Marie-Tooth disease. Other conditions such as leprosy, syphilis and rheumatoid arthritis can also result in Charcot neuroarthropathy. Trauma to the peripheral nerves and prolonged exposure to toxic substances such as alcohol can also result in Charcot neuroarthropathy.

   The basic goal for surgery of the deformed Charcot foot is to create a stable, braceable, plantigrade foot. One can accomplish this by correcting the foot deformity through wedging osteotomies, removing bony prominences and performing an arthrodesis. Surgery should result in no pressure points on the foot and should prevent amputation.

Key Insights On ‘Superconstructs’

In 2009, Sammarco developed the concept of “superconstructs” to describe the use of surgical techniques when the normal principles of internal fixation are abandoned to reduce the likelihood of failure of the procedure.1

   Superconstructs are defined as follows:

1) fusion that extends beyond the zone of injury to include joints that are not affected to improve fixation;
2) bone resection performed to shorten the extremity to allow for adequate reduction of the deformity without undue tension on the soft tissue envelope;
3) use of the strongest fixation device that can be tolerated by the soft tissue envelope; and
4) application of the fixation devices in a position that maximizes mechanical function.

   Surgeons use superconstructs in situations in which they expect technical problems in achieving a successful outcome and in patients with bone loss, dysvascular bone, severe osteoporosis and major deformity correction. Podiatric surgeons may also use these superconstructs when patients have comorbidities that would adversely affect healing.

Assessing The Pros And Cons Of Plantar Plating And Locking Plates

   Surgical reconstruction with fixation of the neuropathic Charcot foot deformity can be difficult and challenging to the surgeon. In addition to correcting a severe foot deformity, the bone is usually of poor quality and the ability to heal may be impaired.

   The bone may be fragmented and unable to hold a screw. When you combine this with premature ambulation, it can result in a loss of fixation and correction. Even with stable fixation, the incision site may be prone to dehiscense, ulceration, infection and osteomyelitis, which could further weaken the bone.

   Current fixation options for the Charcot foot include plantar plating, locking plates, external fixation and intramedullary screws.

   Various authors have advocated plantar plating to support the medial column in the reconstruction of the Charcot deformity. The plate has the advantage of bridging areas of weakened or grafted bone, and one can anchor this plate into stronger bone distally and proximally. Biomechanically, one can increase the strength of the plate by placing it on the plantar aspect of the foot. In this position the plate is under tension with weightbearing.

   Studies have confirmed the strength of the plantar plate in comparison to crossed screws in stiffness and in load to failure.2 Schon and colleagues have reported success in using the plantar plate to maintain the arthrodesis site in the Charcot deformity.3

   The disadvantage is that the plantar surface of the medial column is very irregular and one must remodel this to fit the shape of the plate. This can involve extensive dissection. Even with the mechanical strength of the plantar plate, premature weightbearing can result in failure of the plate and screws with displacement of the arthrodesis site.

   Locking plates and screws give surgeons the advantage of attaching the screw to the plate rather than the bone. This type of fixation is not as dependent on the quality of the bone as conventional plates and screws, and this makes locking plates and screws very effective in softer osteoporotic bone. Bicortical fixation of this system may further increase screw resistance to pull out. When one applies this fixation dorsally, theoretically, it is as strong as the plantar plate. There is much less dissection involved when one applies the plate dorsally rather than plantarly, and surgeons can easily contour the bone surfaces to accept the plate.4,5

Can External Fixation Be Beneficial For Charcot?

External fixators have proven to be very versatile by being able to provide distraction, compression and stability. Podiatric surgeons can also use external fixation in osteoporotic bone as it provides excellent strength. In some cases, physicians can allow early weightbearing with the fixator. It is possible to use this type of fixation in the presence of a localized infection by positioning the wires away from the infected area.6

   However, the use of an external fixator can result in many complications. The most common is pin tract infection. Cellulitis, osteomyelitis, loosening of the half pins or breaking of the wires can also occur. These complications may require repositioning of the pins and wires, or early removal of the frame. When it comes to this type of fixation, one must be careful about proper patient selection as there are many people who physically and mentally cannot tolerate an external fixator.7

What About Intramedullary Screws?

Intramedullary screw fixation is not a new concept. In 1991, Sammarco presented a case in which he used an intramedullary screw for a midfoot reconstruction. He inserted the screw from the posterior aspect of the calcaneus into the medullary canal of the fourth metatarsal.8 Researchers have demonstrated that intramedullary screw fixation provides better stability than oblique screw fixation for arthrodesis of the calcaneocuboid joint.9

   Another advantage is that intramedullary screws are able to resist axial loading caused by weightbearing. This type of fixation gives surgeons the advantage of being able to achieve correct alignment prior to inserting the screw. With the guide pin in the bone, one can perform final reduction and advance the pin across the arthrodesis site, providing temporary stabilization until the surgeon inserts the screw.

   Another advantage is that surgeons often can insert the screws through a small percutaneous incision, thus avoiding a more extensive dissection. Since the surgeon is not drilling the holes directly through the cortical bone, he or she can avoid stress risers that could result in fracture.

   Very few studies have reported the outcomes of intramedullary screws for the reconstruction of the Charcot foot deformity. Sammarco and colleagues reported on 22 patients who had midfoot arthrodesis procedures fixated with this technique. There were no amputations and all patients were considered to have successful limb salvage.10

A Step-By-Step Guide To Charcot Midfoot Reconstruction

When it comes to Charcot midfoot reconstruction, one should first ensure the patient is in the supine position. This permits easy access to the medial and lateral aspects of the foot. Flex the knee and internally rotate the leg to provide exposure to the posterior aspect of the leg, which is necessary for the Achilles procedure.

   The first step in the reconstruction is releasing the contracted Achilles tendon. Instead of the normal calcaneal inclination angle of approximately 20 degrees, Achilles contracture can result in a neutral or even a negative angle. Lengthening of just the gastrocnemius tendon is usually not sufficient to correct a negative calcaneal angle and lengthening of the Achilles tendon complex is usually necessary. The goals of the procedure are dorsiflexion of the foot to at least a 90 degree angle to the leg and reducing a negative calcaneal angle.

   Occasionally, it is necessary to insert a large Steinman rod into the posterior aspect of the heel. The surgeon can then use this as a joystick to dorsiflex the calcaneus and talus, and correct the negative calcaneal inclination angle. The specific lengthening procedure is up to the surgeon’s preference. One can perform the procedure with an open or percutaneous approach. After the surgeon has performed the lengthening, if the negative calcaneal inclination angle is still present, it may be necessary to release the posterior capsule of the ankle joint.

   Appropriate planning is necessary to determine incision placement. When there is a rocker bottom deformity, there is a collapse of the medial column with fracture or dislocation occurring at some level of the midfoot, either the talonavicular joint, navicular cuneiform joint or first metatarsal cuneiform base. Any or all three of these joints can be involved.

   A medial incision provides excellent exposure to all of the involved medial joints. One must take care to identify and retract both the tibialis anterior and tibialis posterior tendons. If the lesser metatarsals are displaced laterally, make an incision between the second and third and between the fourth and fifth metatarsals at their bases to ensure adequate exposure of the joints.

   If the foot has a rocker bottom deformity with abduction of the forefoot, one must take a wedge of bone from the midfoot at the apex of the deformity. Make the osteotomy from medial to lateral, usually at the level where the greatest amount of pathology exists.

   Remove an appropriate wedge of bone with the base facing medially. Extend the osteotomy as far laterally as needed to correct the deformity. Once you have removed the wedge and closed the arthrodesis site, abduction will be corrected. The forefoot should be plantarflexed with correction of elevatus.

   The surgeon must follow the basic principles in performing an arthrodesis. One must remove all cartilage to good bleeding, subchondral bone and the surgeon must fashion the osteotomy site to ensure good alignment and uniform fit of the bone surfaces with no strain on the soft tissue envelope. Once this is complete, it should take minimal force to reduce the arthrodesis site.

   One can usually correct mild lateral displacement with the medial wedge resection. However, if the lesser metatarsals are severely dislocated, it may be necessary to perform osteotomies through each metatarsal cuneiform base and cuboid joint to enable reduction.

   Once you have aligned the osteotomy sites and corrected the deformity, you may employ 0.62 Kirshner wires to provide temporary stability and maintain the alignment.

Pertinent Pearls On Employing Intramedullary Screw Fixation

Intramedullary screw fixation can be very difficult and one should not attempt to use this fixation without the aid of fluoroscopy. The surgeon can insert the intramedullary screw from a distal approach through the first metatarsal head or posteriorly through the talus. If you insert the screw from the metatarsal head, you may use an open or percutaneous procedure.

   The surgeon can employ either a dorsal or plantar approach depending on the amount of motion at the first metatarsophalangeal joint. If dorsiflexion of the hallux is greater than plantarflexion, I will dorsiflex the toe and enter percutaneously from the plantar distal surface. Otherwise, I will plantarflex the great toe, make a 2 to 3 cm incision dorsally and expose the articular surface of the metatarsal head.

   Originally, when using a 6.5 mm screw, I would drill through the cartilage of the first metatarsal head with the 4.5 mm drill bit but this technique eradicates almost all of the articular cartilage. Currently, I will use an appropriately sized trephine to remove a plug of cartilage and bone to a depth of about 2 cm. Once you have inserted the bone screw, you can reinsert the osteochondral plug to minimize damage to the joint.

   After removing the trephine plug, insert the guidewire from the cannulated screw set and drive it into the intramedullary space of the first metatarsal. Before advancing the guide wire into the midfoot, reduce the arthrodesis site. Advance the guide wire across what is left of the cuneiform and navicular, across the arthrodesis site and anchor it into the dense cancellous bone of the body of the talus. With the guide pin in place and the medial column aligned, overdrill the bone and insert the screw. Generally, one would position the head of the screw at the junction of the metaphysis and diaphysis of the first metatarsal.

   If you are employing a posterior approach, insert the guide pin from the posterior aspect of the talus. Make the percutaneous incision adjacent to the Achilles tendon and carry it through the capsule. Fluoroscopy guidance is necessary for this technique. Insert the guide pin from the posterior aspect of the body of the talus, through the talus neck and head, and through the medial column of the foot. With the foot in good alignment and the guide pin in place, overdrill the bone and insert the bone screw. I prefer a headless screw for this approach because the head of a traditional screw may impinge the posterior lip of the tibia.

How To Address Fixation For Lesser Metatarsals And The Lateral Column

Intramedullary fixation of the lesser metatarsals can be very difficult because of the smaller diameter of the metatarsals. Most of the time, one cannot use a 6.5 mm screw because it could lead to fracture of the metatarsal. A more feasible option is to use smaller diameter screws like a 4.5 mm or 5 mm screw.

   With appropriate exposure of the metatarsal bases, use a clamp to elevate the metatarsal base so you can see the medullary canal. Insert a guide pin through the canal and exit through the metatarsal head plantar to the toe. After advancing the guide pin distally to the metatarsal base, reduce the metatarsal and retrograde the pin into the midfoot and rearfoot. Overdrill the bone and insert the screw from distal to proximal. I usually employ a headless screw for the lesser metatarsals.

   If the Charcot neuroarthropathy has resulted in fracture dislocation at the Lisfranc joint, which has coalesced and resulted in fusion at the metatarsal bases, the surgeon may employ an alternative technique. In this case, it is possible to insert the screws from an area between the metatarsal bases through the midfoot and into the rearfoot. Make the incision between the toes at the intermetatarsal space and insert a guide pin by hand until you encounter the metatarsal bases. At that point, use power to advance the pin guide through the metatarsal bases and into the cuneiforms. This technique is effective for stabilizing the central rays.

   One can also stabilize the lateral column in this manner. The surgeon can insert the screw distally from the third or fourth intermetatarsal space — whichever is better aligned with the rearfoot — and advance it through the cuboid and into the calcaneus. One can accomplish this procedure from the posterior lateral approach. The screw should pass through the calcaneus, across the calcaneocuboid joint, through the cuboid and into the metatarsal bases.

Tips On Bone Screw Selection For The Medial Column

Use the largest diameter screw possible for the medial column. This can range from 6.5 to 8 mm diameter. A fully threaded screw is less likely to displace postoperatively than a partially threaded screw. A cannulated system is much easier to work with but, if possible, a solid screw is preferred over a hollow screw because of its greater strength.

Salient Insights On Post-Op Management

Although one may apply a splint to the extremity, I prefer the strength of a fiberglass below-the-knee cast. If there is concern about significant postoperative swelling, one can bivalve the cast in the recovery room.

   Most patients with diabetes cannot remain non-weightbearing even with preoperative strengthening with physical therapy. They do not have the upper body strength or the balance to effectively use crutches. When patients have increased BMI and neuropathy, full weightbearing could result in displacement of the osteotomy/arthrodesis sites.

   One may allow partial weightbearing with a walker as well as a wheelchair and scooters. When osseous consolidation has occurred, we usually fit patients with a Charcot restraint orthotic walker (CROW).

Case Study: When A Patient Presents With A Painful, Deformed Foot And A History Of Frequent Infections

A 66-year-old male was referred to the office for evaluation and treatment of a painful, deformed left foot. Pain was graded in the range of 2 to 5 on a scale of 0 to 10. He had a history of frequent infections and an ulcer on the plantar aspect of his foot occurring periodically over the last 18 months. He had failed orthotics, bracing and diabetic shoes. The patient reported that his foot structure started changing about two years ago.

   His medical history was positive for type II diabetes, arthritis, coronary artery disease, hypertension and hyperlipidemia. The patient’s medications included humulin 70/30, olmesartan (Benicar, Daiichi Sankyo), clopidogrel bisulfate (Plavix, Sanofi Aventis/Bristol-Myers Squibb), metoprolol succinate 50 mg (Toprol, AstraZeneca), lovastatin 40 mg, ranitidine 150 mg, hydrochlorothiazide 12.5 mg and aspirin 81 mg.

   His surgical history included a right hip implant and open reduction with internal fixation of a Lisfranc fracture dislocation of his left foot in 2003. The patient also had an angioplasty with insertion of a stent in 2008.

   In regard to the physical examination, his left foot pulses were palpable and the capillary refill time at the toes was 3 to 4 seconds. He had pronounced neuropathy to the level of the ankle joint. There was a stasis dermatitis on his lower leg and foot secondary to venous insufficiency.

   Very mild edema was present in his foot and he had diffuse hyperkeratosis on the plantar aspect of his foot at the apex of his deformity. There was no evidence of an ulcer. Musculoskeletal examination revealed an equinus. With his knee extended and with maximum dorsiflexion, his foot was plantarflexed 15 degrees. With knee flexion, his foot could be dorsiflexed to a neutral position. Subtalar joint motion had 10 degrees of inversion and 5 degrees of eversion. In stance, he had a lowered medial arch, a prominent rocker bottom deformity and abduction of the forefoot.

   Radiographic examination revealed comminution, fragmentation and collapse of his midfoot specifically involving the cuneiforms and navicular. Five bone screws remained from his previous surgery. The lateral view revealed a negative calcaneal inclination angle, corresponding plantarflexion of the talus and dorsiflexion of his forefoot creating a rocker bottom deformity.

   The patient was cleared for elective foot surgery by his primary care physician and his cardiologist. Plavix was discontinued seven days prior to surgery.
The surgical procedure consisted of performing a gastrocnemius tendon lengthening through a small 3 cm incision on the posterior aspect of the lower leg. Through a linear incision on the medial aspect of the foot, the talonavicular, naviculocuneiform and metatarsal base cuneiform joints were exposed.

   I removed four of the screws that interfered with the procedure. I removed a wedge of bone from the medial aspect of the foot, which encompassed the majority of the cuneiform and navicular bones, and extended laterally to the level of the lateral column. I adducted and plantarflexed the forefoot, and remodeled the osteotomy sites to ensure good bone alignment.

   I inserted a 6.5 mm cannulated bone screw through the first metatarsal head, across the arthrodesis site and into the body of the talus. I inserted a second screw through the second intermetatarsal space, through the hard bone of the second and third metatarsal bases across the fusion site, and into the calcaneus. I inserted a third screw from the posterior aspect of the calcaneus through the midfoot in order to provide a very strong construct. Plantarflexion of the forefoot reduced the rocker bottom deformity and an exostectomy was not necessary.

   The patient’s postoperative course was unremarkable and he has returned to wearing a diabetic shoe with plastazote inserts.

In Conclusion

Reconstruction of the Charcot foot deformity is a high-risk procedure that is prone to many complications including wound dehiscense, infection, osteomyelitis and amputation. A common surgical complication is failure of bone screws and plates with a loss of correction.
Intramedullary fixation is a concept that takes advantage of the strength of the cortical shell of the metatarsals and the dense hard cancellous bone of the talus to stabilize the medial column. This type of fixation appears to provide more strength and provide better outcomes than other types of fixation.

   Dr. Fallat is a Diplomate of the American Board of Podiatric Surgery and is a Fellow of the American College of Foot and Ankle Surgeons. He is the Director of Podiatric Surgical Residency at the Oakwood Annapolis Hospital in Wayne, Mich.

References

1. Sammarco VJ. Superconstructs in the treatment of Charcot foot deformity: plantar plating, locked plating and axial screw fixation. Foot Ankle Clin N Am. 2009;14(3):393-407.
2. Marks RM, Parks BG, Schon LC. Midfoot fusion technique for neuropathic feet: biomechanical analysis and rationale. Foot Ankle Int. 1998; 19(8):501-10.
3. Schon LC, Easley ME, Seinfield SB. Charcot neuroarthropathy of the foot and ankle. Clin Orthop Relat Res. 1998;349(4):116-31.
4. Hardukewych GJ, Ricci W. Locked plating in orthopaedic trauma: a clinical update. J Am Acad Orthop Surg 2008;16(6):347-55.
5. Tejwani NC, Wolinsky P. The changing face of orthopaedic trauma: locked plating and minimally invasion techniques. Instr Course Lect. 2008; 57:3-9.
6. Grant PW, Rubin LG, Pupp GR, et al. Mechanical testing of seven fixation methods for generation of compression across a midtarsal osteotomy: a comparison of internal and external fixation devices. J Foot Ankle Surg. 2007;46(5): 325-335.
7. Giurini J. A closer look at fixation options for the Charcot foot. Pod Today. 2005;18(11):16-21.
8. Sammarco GJ. Diabetic arthropathy. In: Sammarco GJ (ed): The Foot in Diabetes, Ch. 11, Lea and Febiger, Philadelphia, 1991, pp. 153-72.
9. Kann JN, Parks BG, Schon LC. Biomechanical evatuation of two different screw positions for fusion of the calcaneocubiod joint. Foot Ankle Int. 1999; 20(1):33-6.
10. Sammarco VJ, Sammarco GJ, Walker EW, et al. Midtarsal arthrodesis in the treatment of Charcot midfoot arthropathy. J Bone Joint Surg Am. 2009; 91(1):80-91.
11. Eichenholtz SN. Charcot Joints. Charles C. Thomas, Springfield, IL. 1966.
12. Brodshy JW: The diabetic foot. In: Coughlin MJ, Mann RA (eds): Surgery of the Foot and Ankle, Mosby, Inc., St. Louis, 1999, pp 895-969.
13. Schon LC, Weinfield SB, Horton GA, et al. Radiographic and clinical classification of acquired midtarsus deformities. Foot Ankle Int. 1998; 19(6):394-404.
14. Sammarco GJ, Conti SF. Surgical treatment of neuroarthropathy foot deformity. Foot Ankle Int. 1998; 19(2):102-9.

   For further reading, see “How To Manage The Charcot Midfoot Deformity” in the July 2010 issue of Podiatry Today or “Current Insights On Classifying Charcot Arthropathy” in the April 2009 issue.