ISCHIAL STRESS FRACTURE
IntroductionStress fractures are common overuse injuries. It is a continuum of bone injury from radiologically occult, yet microscopic, trabecular injury to frank fracture. These fractures are frequently seen in athletes and military recruits. 2 types of stress fractures are seen: A fracture within normal mineralised bone is termed fatigue fracture (usually as a result of abnormal load or stress; whereas a fracture within abnormal bone is termed insufficiency fractures (may oocur with an underlying condition such as osteoporosis, radiotherapy, corticosteroid therapy or rheumatoid arthritis). Pain is the presenting symptom.
Case ReportA professional soccer player presented with low-grade right sided buttock pain worsening over 4 months. There was tenderness with palpation of hamstring insertion. So that, his clinician wanted MRI examination to rule out hamstirng pathology.
MRI revealed a lineer hypointense signal in cranial part of the ischial bone in both T1 and T2-weighted images (Figure 1-2). There is also large surrounding T2-hyperintense signal, consistent with perilesional bone marrow edema (Figure-1). These findings suggested a probability of stress fracture. Further examination with multislice CT, clearly delineated stress fracture and surrounding sclerosis (Figure-3).
Long-lasting pain in pelvic region should be evaluated with MRI. Radiologist should be aware of any bone marrow edema of pelvic bones in athletes, as if it may be a sign of stress fracture.
References1) Raija Korpelainen, et. al. Risk Factors for Recurrent Stress Fractures in Athletes. Am J Sports Med (2001), Vol. 29, No. 3: 304-310.
2) Barry P. Boden, et. al. Low-Risk Stress Fractures. Am J Sports Med (2001), Vol. 29, No. 1: 100-111.
3) A. W. Clarke, et. al. Case report: bilateral ischial stress fractures in an elite tennis player. Skeletal Radiol (2009), 38:711–714.
Figure-1: Lineer hypointensity and surrounding hyperintense edema is seen on T2-weighted image(arrows)
Figure-3: Stress fracture (short arrow) and surrounding sclerosis is seen on sagittal MPR image of multislice CT
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