Current Insights On Classifying Charcot Arthropathy
How Schon Classifies Midfoot Deformities
Schon, et al., developed a classification system, which further categorized midfoot deformities. They concluded that midfoot deformities can be classified as one of four types based on the anatomic location with the most significant involvement.20 The patterns include: Lisfranc, naviculocuneiform, perinavicular and transverse tarsal patterns of deformity.
The Lisfranc pattern will have significant involvement at the metatarsocuneiform joints. One may see the naviculocuneiform pattern when the deformity occurs more proximally at the naviculocuneiform joint. The perinavicular pattern includes the navicular and its adjacent bones, and the transverse tarsal pattern involves significant deformity at the talonavicular joint.
Schon also included three stages of severity (A-C) based on the degree of collapse in the sagittal plane as shown on lateral weightbearing radiographs.
Stage A is the least severe as the deformity does not collapse to the level of the plantar surface of the foot. Stage B deformities collapse to the level of the plantar surface of the foot.
Stage C represents the most severe deformity in which the midfoot is collapsed beneath the level of the plantar foot. This deformity represents a rocker bottom foot and is often associated with plantar ulcerations.
A Closer Look At A Five-Stage Classification
Sella and Barrette developed a five-stage classification scheme for medial column neuropathic joint disease based on radiographs, clinical findings and bone scans.16 This system divides the medial column of the Charcot foot into five clinical stages.
This system includes an early phase, Stage 0, which consists of localized heat and swelling of the medial column. Radiographs are normal. Stage 1 follows and early bone involvement is visible on radiographs. Radiographic findings include localized osteopenia, subchondral cysts, erosions and possibly diastasis. Stage 2 consists of joint subluxation and once dislocations and joint collapse occur, the patient reaches Stage 3. Stage 4 represents healing and radiographic findings include sclerosis and fusion of affected bone and joints.
The anatomic-based classification systems provide insight into the frequency and patterns of bone and joint involvement, but none of these classification schemes is able to predict outcomes. Patient outcomes depend not only on the anatomic site of involvement but also the presence of an ulceration and osteomyelitis.
Could A New Charcot Classification Help Predict Amputation Risk?
Recently, Rogers and Bevilacqua proposed a new classification scheme, which accounts for the degree of complications in the Charcot joint (see “A Guide To A New Charcot Classification System” on page 24).22 This new system considers deformity, ulceration and osteomyelitis, and may be helpful in predicting amputation.
This is a two-axis system (XY) and combines the features of the clinical exam, radiography and anatomy. The X-axis marks the anatomic location of involvement and the foot and ankle are divided into three regions: forefoot, midfoot and rearfoot/ankle. The Y-axis describes the degree of complication in the Charcot joint. A is acute Charcot with no deformity, B is Charcot foot with deformity, C is Charcot foot with deformity and ulceration, and D includes osteomyelitis. Therefore, one moves across the X-axis (anatomic involvement) and/or down the Y-axis (complicating factors) as the Charcot foot becomes “more complicated” and is accordingly at greater risk for amputation.
We postulate that a 1A Charcot foot (acute Charcot arthropathy localized to the forefoot) is relatively simple and at lower risk for amputation in comparison to a 3D Charcot foot (rearfoot and/or ankle involvement with underlying osteomyelitis). The proposed classification system has not been correlated with patient data. However, studies are currently underway to evaluate the effectiveness of this classification scheme in predicting amputation.