Predictors of Successful Antibiotic Treatment of Osteomyelitis in Diabetic Forefoot Infection.

Background: Osteomyelitis (OM) associated with diabetic foot ulceration (DFU) is a growing public health challenge worldwide. Since 2012 the number of patients presenting with DFU per year to our centre has doubled.

Objective: This study aims to evaluate outcomes from outpatient antibiotic therapy (OPAT) in the management of OM in DFU patients.

Methods: A retrospective analysis was performed of medical notes, radiology, and vascular laboratory reports for all DFU patients with OM treated from April 2016 to April 2020. Variables analyzed included age, gender, site of OM, WIfI Score (Wound Ischaemia and foot Infection Score), probe-to-bone test (PTB), imaging (X-ray/magnetic resonance imaging (MRI), co-morbidities (peripheral arterial disease (PAD), chronic kidney disease (CKD), hypertension (HTN), smoking, ischemic heart disease (IHD), and dyslipidaemia. Outcomes evaluated were healing, recurrent DFU, and freedom from amputation at 12 months.

Results: 185 patients were admitted with 264 infected digits (Male 223; Female 41). The mean age was 66 years. Only 168 (63.6%) were fully healed at 12 months. Of the 96 patients who failed to heal, 43 underwent a repeat course of prolonged antibiotics without improvement. Factors associated with treatment failure were PAD, poorly controlled HbA1c and Deep or Extensive Ulcer or Gangrene.

Conclusion: Extended outpatient antibiotic therapy (with an inpatient multidisciplinary approach) is an effective treatment for digital OM in DFU with a success rate of 63%. In recurrence, repeating prolonged antibiotics is unlikely to achieve healing. PAD, poorly controlled HbA1c and Deep or Extensive Ulcer or Gangrene are predictors of treatment failure.