(CS-125) Bone Pathology in Osteomyelitis after Trans metatarsal Amputation

Qi Chu, DPM – Resident, Podiatry/Surgery, BMC/BOSTON UNIVERSITY SCHOOL OF MEDICINE; Elizabeth Sanders, DPM – Attending Physician, Podiatry/Surgery, BMC/BOSTON UNIVERSITY SCHOOL OF MEDICINE; Maral Jonloo, DPM – Resident, Podiatry/Surgery, BMC/BOSTON UNIVERSITY SCHOOL OF MEDICINE

Introduction:

Each year, about 1.6 million of the 38.4 million Americans with diabetes experience a diabetic foot ulcer. Approximately 50% of ulcers become infected; between 15% and 20% of moderate-to-severe infections eventually lead to a lower-extremity amputation (1). Peripheral artery disease (PAD) and osteomyelitis (OM) are the predominant causes of non-healing ulcers (2). Diagnostic measures for OM include Magnetic Resonance Imaging (MRI), a probe-to-bone test, a bone biopsy, and pathology from resected bones (3).  This study evaluates the pathology of resected bones from patients who underwent trans metatarsal amputation (TMA).

Methods:

We reviewed the records of 276 patients with TMA from 2014 to 2023. All patients had diabetes, foot ulcers, and PAD.   We excluded patients who did not have diabetes and those who had TMA because of trauma or cancer. All specimens from the TMA procedure were sent to pathology for analysis.

Results:

142 out of 276 patients had pathologic OM at the time of TMA. 181 patients returned to the operating room, and 23 specimens were positive for OM in patients who had previously been negative. Procedures for the return trips to the operating room included wound closure, debridement, midfoot amputation, and major amputation. Overall, 179 had successful TMA, 15 had successful midfoot amputation, and 82 required major amputation.

Discussion:

Although MRI is regarded as the most reliable technique for diagnosing OM, with a sensitivity of 90% and specificity of 80% (4), it was not initially used to diagnose OM in our patient group.  Twenty-three specimens were positive at the second surgery. The surgery became necessary when the wounds showed slow progress. Of the 23 patients with delayed OM diagnoses, 7 needed major amputation, and all also had PAD. An early MRI test might improve the overall results. Like MRI, surgical pathology examines all parts of the infected foot, and both can have late manifestations. We can get MRI results in 1 day, while pathology results may take up to one week. Pathologic examinations can provide a more definitive diagnosis. We need to have a prospective study to compare the efficacy of MRI and pathologic examination.