Evaluation of acute charcot foot using SPECT/CT imaging

A. Bilal, K. Boddu, S. Hussain, N. Mulholland, G. Vivian, M. Edmonds, V. Kavarthapu

Introduction: Charcot arthropathy is a complex condition affecting diabetic patients with neuropathy. Diagnosis of acute Charcot arthropathy particularly in absence of any perceptible trauma is very challenging as clinically it can mimic osteomyelitis and cellulitis. Delay in recognition of Charcot arthropathy can result in gross instability of foot and ankle. Early diagnosis can provide an opportunity to halt the progression of disease. We report the role of SPECT /CT in the early diagnosis and elucidation of the natural progression of the disease.

Methods: Our multidisciplinary team analysed the scans of neuropathic patients presented with acute red, hot, swollen foot with normal radiological findings (Eichenholtz stage 0), attending the diabetic foot clinic from 2009-2013.The patients were selected from our database, clinic and nuclear medicine records. Initial workup included the assessment of peripheral neuropathy, temperature difference, between the feet, serum inflammatory markers and weight bearing dorsoplantar, lateral and oblique x-rays. All patients had three dimensional triple Phase Bone Scan using 800Mbq ^99mTc HDP followed by CT scan. Those patients with obvious radiological findings and signs of infection were excluded.

Results: We evaluated 193 scans in 189 patients. One hundred and forty nine patients showed increase in focal radionuclide uptake at ligament insertion or subchondral bone with a positive predictive value of 77 percent. Forty four out of 193 were negative for Charcot changes and they were not treated as Charcot. These patients did not develop any Charcot changes in the mean follow up of 8 months, indicating a clinically false positive rate of 23%.

Conclusion: SPECT/CT scan is a highly sensitive and specific tool for early diagnosis and accurate localisation of Charcot neuroarthropathy as clinical examination results in high false positive rate. SPECT/CT also helps to understand the natural progression of this disease.