Review Question - QID 5636

The next best step would be an MRI hip and pelvis to investigate for an occult fracture of the left hip.

Moderate evidence supports MRI as the advanced imaging of choice for diagnosis of presumed hip fracture not apparent on initial radiographs. MRI has been shown to be able to detect occult fractures earlier than bone scan, with better spatial resolution. Usually the MRI should be obtained in less than 24 hours from the time of injury. For situations in which MRI is not immediately available, bone scan can be considered after 72 hours form the time of injury. However, this may compromise patient care and put the patient at risk of fracture displacement.

Cannon et al. reviewed the imaging of choice in occult hip fracture. They showed that physical examination yields a poor sensitivity identifying occult hip fractures, with log-rolling and straight-leg raise as 50% and 70%, respectively. The most sensitive modality for occult fracture identification was MRI.

Iwata et al. retrospectively reviewed a cohort of 35 patients with clinically suspected fractures of the hip that underwent MRI. All radiographs were negative. In 26 of these patients, a T1-weighted coronal MRI showed a hip fracture with 100% sensitivity.

Roberts et al. reviewed the 2015 AAOS Clinical Practice Guideline: Management of Hip Fractures in the Elderly. They report moderate evidence that supports MRI as the advanced imaging of choice for diagnosis of presumed hip fractures not apparent on initial radiographs.

Figure A is a AP radiograph of the left hip and pelvis. Apart from a healed fracture of the ischiopubic rami and generalized osteopenia, there is no obvious hip fracture. Figure B is a coronal CT image that does not demonstrate evidence of an acute hip fracture. Illustration A is a T1 weighted MR image that shows a non displaced fracture (white arrow) through the intertrochanteric region of the left proximal femur.

Incorrect Answers:
Answer 1: Stress view radiographs would not be recommended.
Answer 2: If MRI is contraindicated, for example if a pacemaker is present, then a bone scan at 72 hours is the next test of choice. Waiting 7 days would not be appropriate for this patient.
Answer 3: Repeating the CT scan will not help to identify fracture, unless the fracture becomes displaced. A delay in identifying a fracture pattern by 48 hours, while the patient is non-mobile, significantly increases their risk of complications.
Answer 5: Weight bearing activity as tolerated with close follow-up may be suggested if the patient is clinically able to walk and advanced imaging is negative for fracture. The best modality to rule-out occult fracture is MRI.