Pelvic MRI in spinal cord injury patients: incidence of muscle signal change and early heterotopic ossification

Study design Prospective observational study. Objective To evaluate pelvic MRI muscle signal changes and their association with early heterotopic ossification (HO) in patients with spinal cord injuries. Setting National Spinal Injuries Unit, Stoke Mandeville, UK. Methods Forty patients were imaged with at least two interval magnetic resonance (MR) studies of the pelvis in the first 6 months following a spinal cord injury. Scans were reviewed and scored for heterotopic ossification, muscle signal change and extent of muscle involvement. Results Muscle signal change was present in 28 (70%) on the initial MRI and 31 (77%) by the second study. Six patients developed MR changes of prodromal or immature heterotopic ossification (15%). No restricted diffusion was demonstrated and no patient developed mature HO. Patients developing MR changes of early HO were more likely to have grade 3 muscle changes. Conclusion Increased T2 muscle signal is common following cord injury, is frequently progressive in the subacute period and is associated with complete injury and early MR signs of heterotopic ossification.