Patients with Charcot neuroarthropathy often present with manifestations in the vascular, neurologic, musculoskeletal, and dermatologic systems. In the acute phase, look for a severe inflammatory reaction with edema and erythema. In addition, there is an increase in local skin temperature of several degrees compared with the contralateral limb.4 Frequently, there is mild to moderate pain that may be disproportionate to expectations because the foot is insensate.4,5
Many patients with Charcot neuroarthropathy have normal or even rebounding pedal pulses. The presence of an ulcer might further misguide the clinician toward a diagnosis of an acute infectious process, such as cellulitis or acute osteomyelitis.
As the acute process ends, the foot may continue to have residual edema or erythema or both. However, the chronic Charcot foot frequently has a noteworthy appearance, known as a “rocker bottom foot.” This deformity arises after the acute degenerative phase, as small fractures coalesce along with fusion of the osseous debris. The consolidated bone appears as a plantar convexity that causes increased plantar pressures, which may lead to neuropathic ulcerations.
A typical rocker bottom foot is shown in Figure 1. A noninfected neuropathic ulcer on the bottom of the midfoot resulted from increased pressure from ambulation. Increased hyperkeratotic skin around the ulcer was caused by walking.
Acute exacerbations may continue to occur. They often are misdiagnosed as chronic osteomyelitis because of their appearance (fibrotic and frequently widened soft tissue envelope, with an ulcer at the site of a gross osseous deformity) and the fact that among patients who have DM, infection is more common than Charcot neuroarthropathy.
Diagnosis of Charcot Foot
Early diagnosis of Charcot foot and proper treatment are critical to preventing long-term consequences. Charcot neuroarthropathy should be considered in all patients with DM who have peripheral neuroarthropathy and present with leg or foot edema, erythema, and increased skin temperature, with or without foot ulceration.
If the diagnosis is not made immediately when the patient reports symptoms, a vicious cycle ensues, because weight bearing further stresses the injured Charcot joint. This leads to increased fragmentation, instability, joint degeneration, and bony deformities. Further ulceration may lead to concomitant infections and, eventually, amputation. Of course, the concomitant process of Charcot foot and an infection can certainly further challenge the diagnostic process.
Also seen in Figure 1 are a normal-appearing radiograph of a patient’s left foot and, for comparison, a radiograph of the patient’s right foot showing consolidation of the osseous fragments creating the chronic joint subluxation and bony prominence on the bottom of the midfoot.
Misdiagnosis also may lead to unnecessary incision and drainage or to inappropriate treatment with antimicrobial therapy. Maintaining a high index of suspicion for Charcot neuroarthropathy is important to prevent a potentially devastating outcome.
The standard tests for definitive diagnosis of Charcot and osteomyelitis are synovial tissue biopsy and bone biopsy. A finding of multiple shards of bone and soft tissue embedded in the synovium is pathognomonic for Charcot. However, these tests are invasive and involve considerable risk to the patient. Diagnosis by imaging is far preferable.