Analysis of initial injury radiographs of occult femoral neck fractures in elderly patients: a pilot study.

Diagnosis of occult hip fractures by initial radiographs remains challenging in the emergency department. Previously, the gold standard for accurate diagnosis of occult hip fractures was magnetic resonance imaging. This study used initial radiographs obtained in the emergency department to evaluate specific signs and measurements as diagnostic references for occult femoral neck fractures in elderly patients.Initial negative radiographs were reviewed for 2 groups of patients: a group with occult femoral neck fractures (n=16) and a group without fractures (n=32). Reviews of initial radiographs and all imaging studies were performed by a senior orthopedist (C-C.C.) and a radiologist (H-T.W.). Diagnostic signs included lateral, medial, anterior, and posterior signs; measurements included elevation of the fat pad and external rotation of the femur. The prevalence of occult femoral neck fracture was 3.3%. Initial radiographs of occult femoral neck fractures were not routinely negative; 14 (87.5%) of 16 patients with fractures had at least 1 radiographic sign. Using the positive lateral or posterior sign as the diagnostic reference, the sensitivity was 0.875 and the specificity was 0.906. When elevation of the fat pad was ⩾1.5 mm, the sensitivity was 0.867 and the specificity was 0.857 for the diagnosis of occult femoral neck fracture.The lateral and posterior signs and elevation of the fat pad ⩾1.5 mm on initial radiographs are recommended as diagnostic references for occult femoral neck fracture. These references are clearly defined and may offer important information for all clinicians and radiologists in the emergency department.