Sacral Fatigue Fracture in a Military Recruit.

A 19-year-old male military recruit presented with 3 weeks of persistent left hip and groin pain after abnormally twisting his hip during a hike. Initial radiographs were interpreted as negative. He subsequently underwent a bone scan which revealed linear left sacral uptake along or paralleling the sacroiliac joint. Differential diagnostic considerations included unilateral sacroiliitis and sacral fracture. SPECT/CT was performed which confirmed left sacral fatigue stress fracture. Transitional lumbosacral anatomy was evident on radiographs with pseudoarticulation of the transitional left S1 transverse process with the sacrum. We postulate this predisposed the recruit to sacral fracture.