Imaging of occult hip fractures: CT or MRI?

OBJECTIVES: Patients presenting with hip pain but normal plain radiographs may ultimately be shown on further investigation to have suffered an occult hip fracture (OHF). This diagnosis can be made with CT or MRI. Traditionally MRI has been considered a superior modality. We performed a retrospective review of all patients presenting to our service with a suspected OHF over a four-year period, investigated with either CT or MRI.

DESIGN: Retrospective review.

SETTING: Urban trauma centre.

PATIENTS: Patients with suspected hip fractures and negative radiographs.

INTERVENTION: CT or MRI.

MAIN OUTCOME MEASURES: Detection rate; delay in request for further imaging; delay to theatre; re-presentations with missed fractures.

RESULTS: A total of 179 patients were investigated, with a mean age of 82±13 years. The ultimate diagnosis was of an OHF in 71 cases and pelvic or acetabular fracture in 34. The average time from presentation plain radiograph to further imaging was 2.0±2.7 days, but was significantly shorter for CT. No patient re-presented with unidentified fractures or other localised hip pathology within a 12-month period.

CONCLUSIONS: Modern imaging technology does not appear to miss clinically significant fractures. As CT is usually more accessible than MRI, the results of our study should encourage surgeons to consider CT as a first line investigation for occult hip fractures. We advocate a high index of suspicion and early imaging referral for elderly patients presenting with non-specific hip pain following a fall. Level 3 Evidence.