Emerging Concepts In Fixation For Charcot Midfoot Reconstruction

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What You Should Know About Charcot Classification Systems

One of the most widely accepted classifications of Charcot deformity was developed by Eichenholtz.11 This system is based on the characteristic progression of the Charcot deformity. Stage I (development-fragmentation) represents the initial phase of the deformity. Clinically, the foot is red, hot and swollen with an obvious injury to the bone and joints. Stage II (coalescence) is characterized by both injury and healing. Eventually, the deformity stabilizes and the clinical signs of Stage I subside. The hallmark­ of Stage III (reconstruction-consolidation) is the maturation of the bone and soft tissue healing, and the foot becomes stable with a fixed deformity.

Brodsky developed an anatomical classification based on the four areas of the foot typically involved with the deformity.12 Type 1 involves all or portions of the tarsometatarsal joints. This is the most common area of the Charcot deformity. A type 2 injury involves the transverse tarsal joint, subtalar joint or all three joints of the hindfoot. A type 3 injury affects the ankle joint and a type 3B injury affects the calcaneal tuberosity. When the tuberosity is involved, it is usually an avulsion fracture of the posterior superior aspect of the calcaneus and the type 3B injury is the least common Charcot injury.

Schon and colleagues had proposed a classification system for the midfoot based on the area of involvement.13 Type I is a tarsometatarsal (Lisfranc) fracture dislocation. Type II affects the naviculocuneiform area. Type III is perinavicular and Type IV is a transverse tarsal pattern of injury. The authors had also developed a clinical classification of the amount of Charcot deformity based on the physical examination. Stage A exists when the midtarsus is above the metatarsal calcaneal plane. Essentially, the patient maintains an arch. Stage B is when the midtarsus is coplanar with this plane and the arch touches the ground. Stage C is when the midtarsus is below this plane.

Sammarco and Conti proposed another system that recognizes midfoot pathology.14 In this system, Pattern 1 represents diastasis that occurs between the first and second metatarsals with fragmentation and collapse extending across the tarsometatarsal joints. Pattern 2 is medial metatarsal-cuneiform destruction without diastasis of the first and second metatarsals. Pattern 3 is arthropathy (injury) at the navicular-medial cuneiform joint with fragmentation of the middle cuneiform and destruction occurring across the lateral transmetatarsal joints. Pattern 4 is injury occurring at the first metatarsal-medial cuneiform with diastasis between the first and second metatarsals, and proximal and lateral extension into the intercuneiform joint ending at the calcaneal cuboid joint. Pattern 5 is perinavicular arthropathy with distal intertarsal extension.

Lawrence M. Fallat, DPM, FACFAS

   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.

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