Pitfalls and limitations of magnetic resonance imaging in chronic posttraumatic osteomyelitis

The aim of this study was to evaluate pitfalls and technical limitations of MR imaging in diagnosing relapse of chronic posttraumatic osteomyelitis of the lower extremities. Retrospective analysis of MR examinations in 15 pat ients (17 body areas) with suspected relapse of chronic posttraumatic osteo myelitis (at least 1.5 years duration/mean number of surgical procedures pe r patient: 5.8). The MRI findings were compared with postoperative bacterio logy (n = 11) and clinical follow-up (n = 4). Five patients had additional CT examination. Magnetic resonance imaging identified all infected areas co rrectly, but five uninfected regions were diagnosed false positive due to p ostoperative scarring/oedema in bone defects (n = 4) and soft tissue (n = 1 ). Specificity of MRI in diagnosing active bone infection was 63 % and sens itivity 100 %. Additional CT was preoperatively necessary in 5 patients (33 %) to further examine osteomyelitic and reparative bone remodeling. Metal artefacts were present in 11 patients, rendering complete evaluation imposs ible (n = 2) or considerably more difficult (n = 4). Scarring/oedema in pos toperative bone defects occurs up to 13 months postoperatively and represen ts a major pitfall leading to low specificity. Definitive evaluation of sus pected fistula, bony fragments and mineralization by MRI may be limited in this special patient group and requires additional CT in one third of patie nts. Metal artefacts occur in most patients and may impair or even prevent correct film evaluation in 23 and 11%, respectively.