MRI of radiographically occult ischial apophyseal avulsions

Background Acute avulsions of unossified ischial apophyses in children may go undetected on radiography. Therapy includes rest and rehabilitation; however, substantial displacement may require surgery. Objective Our purpose is to illustrate the utility of MRI in the detection of these radiographically occult injuries in skeletally immature children. Materials and methods This retrospective study of more than 5 years included children with ischial avulsions who were evaluated with both radiography and MRI within 3 weeks of acute injury. Initially, radiographs were reviewed to identify those children with unossified ischial apophyses. Subsequently, their MRI examinations were assessed for physeal disruption, bone/soft tissue edema, periosteal/perichondrial elevation and disruption. Initial and follow-up radiographs (if available) were reviewed. Patient age, symptoms and offending activity were determined from clinical records. Results Five children met inclusion criteria. All initial radiographs were normal. MRI showed: edema ( n = 5), periosteal elevation ( n = 4), periosteal/perichondrial disruption ( n = 4), >5.5 mm displacement ( n = 0). Follow-up radiographs in two children (2 and 2.5 months from MRI) showed osseous ischial irregularity. The apophyses remained unossified. Conclusions Acute unossified ischial apophyseal avulsions in children may be radiographically undetected. In the setting of correlative clinical symptoms, MRI can be used to identify these injuries and to help direct appropriate therapy.