Advanced Imaging
Moderate evidence supports MRI as the advanced imaging of choice for diagnosis of presumed hip fracture not apparent on initial radiographs.

Five low strength studies evaluated the use of MRI to assess for hip fractures in patients with a clinical history consistent with fracture but negative plain films. The included studies demonstrated the ability of MRI to identify fractures, especially in older patients (Chana et al 1). The studies also noted that MRI was able to demonstrate causes of hip pain other than fracture (Harrmati et al2, Kirby et al3, Lim et al 4, and Pandey et al 5).  Only one low strength study (Lee et al 6) was available that evaluated the sensitivity of bone scan in detecting occult hip fractures. Rizzo et al. 7 noted equivalent accuracy when comparing MRI to bone scan in this setting; however, MRI was found to provide a diagnosis earlier (Rizzo et al. 7) than bone scan, with better spatial resolution.  In this study, MRI was obtained within 24 hours of admission and bone scan within 72 hours.  For situations in which MRI is not immediately available, bone scan can be considered (Rizzo et al). 7  In addressing issues of cost and patient discomfort,, three studies showed that a “limited” MRI of the hip could identify occult hip fractures (Lim et al 4, Iwata et al 8, Quinn et al 9); these limited scans were obtained with lower cost and shorter duration that standard MRIs. 

Limited, small studies have examined the use of CT scan in the diagnosis of occult hip fractures.  Due to the quality of existing literature, as well as potential harm with radiation exposure related to use of CT in this setting, this modality was not recommended for evaluation of occult hip fracture.

Risks and Harms of Implementing this Recommendation
There are no specific harms associated with this recommendation.
Future Research
Additional research is needed to clarify the role, if any, as well as accuracy and timing, of bone scan in identifying occult hip fractures. Studies are also needed to clarify the role, if any, of CT in this situation, and the relative accuracy and safety of bone scan vs CT vs MRI for the diagnosis of occult hip fractures.  There needs to be further clarification of the technique and relative accuracy of “limited” MRIs in the diagnosis of occult hip fractures.