Radiographic measures as a predictor of ulcer formation in diabetic Charcot midfoot

Background: Plantar midfoot ulceration in diabetic patients with midfoot Charcot neuroarthropathy is a risk factor for infection that can require amputation. The aim of this study was to determine a simple radiographic predictor of the individual risk of subsequent ulcer formation in this group of patients. Materials and Methods: A retrospective review of all patients seen at our institution between January 1998 and July 2004 with diabetic Charcot neuroarthropathy was performed. Exclusion criteria were previous reconstructive foot surgery, absence of weightbearing foot radiographs and absent pedal pulses. Patient charts were reviewed for demographics, diabetic co-morbidities, and presence of midfoot skin pathology (plantar callus and/or ulceration). Weightbearing anteroposterior and lateral radiographs were assessed using standard measurements. Results: Nineteen patients with radiographs of 24 feet were included. Fifty-eight percent were female, and the mean age was 54 (SD +/- 13) years. Ninety-five percent had type II diabetes mellitus, and the median duration of illness was 20 (range, 14 to 25) years. Midfoot ulceration and callus formation were seen in 6 (25%) and 2 feet, respectively. When radiographic measures of feet with and without midfoot skin pathology were compared, the lateral talar-first metatarsal angle was significantly associated with skin pathology (p < 0.001). Conclusion: The lateral talar-first metatarsal angle measured on weightbearing radiographs is a simple means of monitoring patients' risk of development of midfoot ulceration. Only patients with a lateral talar-first metatarsal angle of greater than -27 degrees had an ulcer. This may be a clinically useful threshold for increase risk of the development of ulceration in midfoot diabetic neuroarthropathy.