Charcot neuroarthropathy: An often overlooked complication of diabetes

Cleveland Clinic Journal of Medicine. 2010 September;77(9):593-599 | 10.3949/ccjm.77a.09163

September 1, 2010|Cleveland Clinic Journal of Medicine

Georgeanne Botek, DPM;Martha A. Anderson, DPM;Ryan Taylor, DPM

ABSTRACTIn patients with long-standing, poorly controlled diabetes and peripheral neuropathy, a red, hot, swollen foot without open ulceration should raise the suspicion of Charcot neuroarthropathy, an often-overlooked diabetic foot complication. The authors discuss key diagnostic features and how to differentiate this condition from cellulitis, osteomyelitis, and other conditions. They review key elements of the workup and emphasize the importance of early diagnosis and prompt treatment to preserve a functioning foot.

KEY POINTS

One must pay particular attention to the history in diabetic patients and assess the risk of diabetic foot complications.
Without the presence or history of an open ulceration, infection is rare.
Paramount to the treatment of this condition are the avoidance of weight-bearing and the immediate referral to a foot and ankle specialist. Prevention, suspicion, early diagnosis, and protection of the involved foot preserve the ability to walk and quality of life.

CHARCOT NEUROARTHROPATHY BEGINS WITH PERIPHERAL NEUROPATHY

The pathophysiologic mechanism of Charcot neuroarthropathy is not completely known, but it is thought to begin with peripheral neuropathy. Being insensitive to pain, patients may subject the joints of the foot (most commonly in the midfoot) to stress injuries that lead to the active Charcot process.^10–12 About half of Charcot patients present with pain, as did our patient.

Although our patient remembered no trauma, he was physically active at the time he first noticed the symptoms.

Four stages of Charcot neuroarthropathy are recognized^11–15:

Stage 0 (inflammation), also called Charcot in situ or pre-stage 1, is characterized by erythema, edema, and heat but no structural changes.^11,12,14,15

Figure 2. Stage 0. A plain anteroposterior radiograph taken in the emergency department shows no osseous abnormalities.

A radiograph in our patient (Figure 2) taken during his initial emergency department visit showed no bony abnormalities. However, if instability, weight-bearing, and inflammation persist, stage 0 can progress to the next stage.

Stage 1 (development) is characterized by bone resorption, bone fragmentation, and joint dislocation. The swelling, warmth, and redness persist, but there are also radiographic changes such as evidence of debris formation at the articular margins, osseous fragmentation, and joint disruption.

Stage 2 (coalescence) involves bony consolidation, osteosclerosis, and fusion after bony destruction. Absorption of small bone fragments, fusion of joints, and sclerosis of the bone are noticeable.

Figure 3. In this radiograph taken 3 to 4 months after the initial presentation, Charcot neuroarthropathy has progressed to stage 2 after delayed immobilization.

A radiograph in our patient taken 3 to 4 months after presentation (Figure 3), after treatment had been delayed, showed that his condition had progressed to stage 2.

Stage 3 (reconstruction) is characterized by osteogenesis, decreased osteosclerosis, and progressive fusion.¹³ Healing and new bone formation occur. Decreased sclerosis and bony remodeling signify that the deformity (for example, subluxation, incongruity, and dislocation) is permanent.⁴

MISDIAGNOSIS IS COMMON

Charcot neuroarthropathy is an often overlooked complication in diabetic patients with peripheral neuropathy. A group of experts reported that 25% of patients referred to their facility who had Charcot neuroarthropathy had not received a correct diagnosis at the referring institution.¹⁶ The incorrect diagnoses included infection, gout, arthritis, fracture, venous insufficiency, and tumor.

Figure 4. Some of the key features of Charcot neuroarthropathy, a complication of diabetes mellitus. The presentation and the course are different in each patient.

The diagnosis is usually made radiographically or by clinical signs such as erythema, warmth, or change in foot shape in a neuropathic foot in the absence of a skin wound. However, even if there is no radiographic evidence of overt osseous dislocation or fracture fragmentation, the condition should still be suspected so that treatment, if indicated, can be started promptly. A careful medical history is most helpful in arriving at the diagnosis. Keep in mind that a patient with neuropathy may be unaware of injury to the foot. Also keep in mind that although certain changes are characteristic of Charcot neuroarthropathy, the condition may be different in every patient. Figure 4 illustrates some of the typical changes that can occur at various stages of Charcot neuroarthropathy.

Laboratory tests can narrow the differential diagnosis

There are no laboratory criteria for the diagnosis of Charcot neuroarthropathy and no hematologic markers, but laboratory testing can help narrow the differential diagnosis. Leukocytosis, an elevated C-reactive protein and erythrocyte sedimentation rate, and recent unexplained hyperglycemia suggest infection.¹⁷ However, unremarkable results on clinical tests in this population may not comprehensively exclude infection.

Our patient’s elevated white blood cell count confused the diagnosis. Further, when he was treated with antibiotics, he reported having less pain, although the edema and erythema continued.

Imaging studies

Although advanced imaging may help confirm the diagnosis of Charcot neuropathy in some patients, it is not always necessary.

Radiography. Radiographic findings are important in diagnosing Charcot neuroarthropathy, although they are less helpful in patients with stage 0 disease, such as our patient, in whom the condition has not yet progressed to fracture or dislocation. All foot and ankle radiographs should be taken in the weight-bearing position. Subtle changes may be missed if non-weight-bearing images are taken.

Magnetic resonance imaging (MRI) can show changes in stage 0, thus enabling treatment to be started sooner,¹⁸ and it is increasingly being recommended for diagnosing Charcot neuroarthropathy, especially in the early stages.³ Although bone scintigraphy and white blood cell scans have been traditionally advocated, MRI offers the highest diagnostic accuracy.¹⁹ Signs on MRI consistent with Charcot neuroarthropathy include ligamentous disruption, concomitant joint deformity, and the center of signal enhancement within joints and subchondral bone.²⁰

MRI can also differentiate Charcot neuroarthropathy from transient regional osteoporosis. The latter has a different anatomic location and does not cause fractures and dislocations, and patients do not have a clinical history of pain.

Another condition MRI can identify is complex regional pain syndrome. In this condition, patients have no radiographic abnormalities except for periarticular osteopenia, but they may have severe pain out of proportion with the clinical appearance, and they may develop soft-tissue deformity in the late stages, which is not seen in Charcot neuroarthropathy.

Figure 5. Magnetic resonance imaging 4 to 6 weeks after presentation shows areas of significant bone marrow edema of the navicular, medial, middle, and lateral cuneiform bones, and at the bases of several metatarsal bones.

MRI findings in our patient 4 to 6 weeks after the initial presentation were characteristic of Charcot neuroarthropathy (Figure 5).

Positron emission tomography (PET) with fluorine-18 fluorodeoxyglucose is also gaining support,²¹ especially when combined with computed tomography (CT). This PET-CT hybrid has better anatomic localization than PET alone.

PET-CT is very reliable for differentiating Charcot neuroarthropathy from osteomyelitis, a distinction that can be difficult to make when Charcot neuroarthropathy is complicated by adjacent loss of skin integrity. The sensitivity of PET-CT in this situation has been reported as 100%, and its sensitivity 93.8%.²²

Patients with Charcot neuroarthropathy demonstrate a low-intensity diffuse uptake that is easily distinguishable from normal joints on visual examination of the images. In addition, the maximum standardized uptake value, a quantitative measurement, is low to intermediate in Charcot neuroarthropathy but significantly higher in osteomyelitis. In one study,²² the mean standardized uptake values were 0.42 in normal feet, 1.3 in Charcot neuroarthropathy, and 4.38 in osteomyelitis.

References

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