Magnetic Resonance Imaging of Pressure Sores in Spinal Cord Injured Patients: Accuracy in Predicting Osteomyelitis

Objective: Identify key magnetic resonance imaging (MRI) features that have a significant correlation with osteomyelitis of pressure ulcers in spinal injury patients. Design: Retrospective review study. Participants: Adult patients admitted to the National Spinal Injuries Centre with spinal cord injury (SCI) and signs of pressure ulceration investigated with MRI. Methods: Analysis of MRI examinations and clinical records collected over a 4-year period. Images were independently assessed by 2 experienced radiologists for osteomyelitis based on assigned predictive indicators including cortical bone erosion, soft tissue edema, deep collections, heterotopic new bone, hip effusion, and abnormal signal change of the marrow. Results: Thirty-seven patients underwent 41 MRI scans. The prevalence of osteomyelitis was highly correlated with cortical bone erosion (r = 0.84) and abnormal bone marrow changes on T1-weighted images (r = 0.82). Key words: osteomyelitis, pressure ulcers, spinal cord injury P atients with spinal cord injuries (SCI) are at a high risk of developing pressure sores due to decreased mobility and lack of sensation, with a reported prevalence between 23% and 33%, 1,2 the lifetime risk estimated between 25% and 85%, 3 and an associated mortality of 7% to 8%. 4-6 Complex pressure sores are associated with adjacent complications including low grade soft-tissue infection, fistula or abscess formation, sinuses, septic arthritis, heterotopic ossification, and osteomyelitis. These complications, especially osteomyelitis, can be difficult to assess by physical examination alone; this results in delayed diagnosis and onset of treatment that leads to prolonged hospitalization and in complicated cases requires surgical intervention and deforming bone debridement. The gold standard for the definite diagnosis of osteomyelitis is histology of bone biopsy and the identification of the causative microorganism by tissue culture. Histological examination requires invasive sampling, and microbiological tissue culture can sometimes become cross-contaminated with pathogens present in the skin and soft tissue of pressure ulcers and draining wounds. 7 Current imaging modalities employed in identifying the presence of osteomyelitis in pressure ulcers includes bone scans, ultrasound, plain films, computed tomography (CT), bone biopsy, and MRI. Bone scan reliably excludes bony infection, 8-13 but it is not specific for the diagnosis of osteomyelitis that is affected by adjacent soft-tissue infection, the presence of orthopaedic devices, trauma, healing fractures, arthritis, surgery, or diabetes. 12,14-16 Ultrasound is not helpful for visualizing bone changes associated with osteomyelitis, nor can it detect associated surrounding soft-tissue infection, 17 but it can be useful in the detection of