Diagnostic accuracy of ultrasonography for occult femoral neck fracture

BackgroundA delay in the diagnosis and treatment of an occult femoral neck fracture (OFNF) can negatively affect the subsequent quality of life. We investigated the diagnostic accuracy of ultrasonography for OFNF in patients confirmed with this condition by magnetic resonance imaging (MRI), and compared these results with other clinical findings.MethodsNinety-four outpatients aged above 70 years with acute hip pain but without radiographic abnormal findings who were suspected of having an occult femoral neck fracture (11 men and 83 women with a mean age of 81.8 ± 6.0 years) were enrolled. Both ultrasonography and MRI were performed in all cases within 24 h. The ultrasonographic distance between the anterior aspect of the femoral neck and the anterior joint capsule (ultrasound joint swelling) was measured.ResultsBy MRI findings, 27 patients were assigned to an occult femoral neck fracture (OFNF) group (1 man, 26 women) and 67 patients to a non-OFNF group (10 men, 57 women). The mean ultrasound joint swelling in both groups was 7.53 ± 1.52 mm and 3.45 ± 0.89 mm, respectively (p = 0.006, 95% CI, 3.58–4.59). A cut-off value of 5.3 mm showed a sensitivity of 0.96 (0.89–0.96) and a specificity of 0.98 (0.92–1.00).ConclusionsUltrasonography shows very high diagnostic accuracy for occult femoral neck fracture. This modality can thus contribute to initial bed-side examinations for this condition in patients over 70 years with acute hip pain.