The Evaluation of SPECT-CT in the Early Management of Acute Charcot Osteoarthropathy (CN)

Abstract

Category: Diabetes Introduction/Purpose: Charcot osteooarthropathy (CN) is a debilitating condition afflicting the bone, soft tissue and joints of foot and ankle and is related to pain insensitivity. Its pathogenesis and natural progression is poorly understood. In patients with high clinical suspicion, treatment with immediate off-loading and immobilisation may halt and (help to) reverse or prevent deformity. We aim to establish the role of SPECT CT in the diagnosis of acute charcot osteoarthropathy of the red swollen foot prior to radiographic changes and assess its reliability in diagnostic accuracy and guiding treatment. Methods: A prospective, observational review of all patients presenting to the multidisciplinary diabetic foot clinic from 1st Jan 2009 to 1st Jan 2013 with clinically suspected acute active charcot arthropathy was performed. All patients with a high clinical suspicion of acute CN and normal radiographs, underwent SPECT-CT within 10 days of the assessment after emergency off-loading in a TCC. A positive SPECT CT scan for new onset acute CN was diagnosed if radioisotope uptake was seen in all 3 phases of scanning. Further CT fusion images provided localization of ongoing activity. All patients were followed up for 1-year or until treatment ceased and treated in concordance with clinical symptoms and SPECT CT imaging. Results: In total 137 patients were referred or self referred with a high suspicion of new onset acute CN. The majority being diabetic (98%), including 116 unilaterally symptomatic feet with normal radiographs; 86 were consequently positively confirmed on SPECT-CT CN; 15 new ‘diabetic’ fractures were diagnosed on the CT component. At 1 year – only 5 patients went on to develop radiological changes consistent with charcot arthropathy even with accepted off loading in TCC. Thirty negative scans were recorded where no triple phase trace response & localisation was uni-focal or not associated with skeletal structures. Differential diagnosis included cellulitis, degenerative changes, old fractures, and planter fasciitis were made. At 1-year none of the patients were found to have developed CN in neither in the form of foot deformity nor radiological evidence of fragmentation or loss of normal bone anatomy. Conclusion: A combination of symptoms including swelling, pain and/or heat, positive three phase tracer uptake and localisation on SPECT CT can identify and aid the management of acute active CN in radiographically normal feet. Positive scans seem to identify an intermediate grade of charcot arthropathy where cortical fractures have occurred with significant subchondral bone turnover. A negative scan excludes high-risk feet for CN confidently and thus can direct treatment. We find SPECT CT a valuable addition to the armamentarium of the treating physician in instituting off loading to prevent the possible progression and onset of deformity and avoiding unnecessary treatment.