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.