Evolution of Signal Abnormality in Femoral Neck Stress Injuries

The image sequence above shows 3 sets of MRI examinations for a 75-year-old woman who began experiencing left hip pain after favoring that side due to contralateral knee pain. Initial MR examination at t=0 shows signal abnormality in the left femoral neck. Approximately 2 months later (t=51 days) patchy small areas of abnormal signal remain, but there has been significant improvement. 5 months after the initial scan (t=145 days), we see resolution of signal abnormality in the femoral neck.

Knowing the expected evolution of post-traumatic bone marrow signal abnormalities can be helpful in the setting of persistent pain or concern for neoplasm. In a patient presenting with persistent pain after the initial MRI, new signal abnormalities could represent reinjury or progressing injury. Persistent signal changes in the absence of new trauma may indicate a neoplasm.

In a study of 10 patients with (9 men, 1 woma, between the ages of 19 to 49), Slocum et al found that STIR signal abnormalities in nondisplaced, compressive-side femoral neck stress fractures resolved 6 months after the first imaging study in 90% of their patients.

Interestingly, they also found that most patients continued to be symptomatic even after resolution of the edema.

References

Slocum KA, Gorman JD, Puckett ML, Jones SB. Resolution of abnormal MR signal intensity in patients with stress fractures of the femoral neck. AJR Am J Roentgenol. 1997 May;168(5):1295-9.