Musculoskeletal ImagingInsufficiency fracture
a
fracture related to application of a normal force to abnormal bone. Insufficiency fractures are one of the two main types of
stress fracture and occur when a normal stress is placed on a bone with deficient elasticity. Insufficiency fractures can occur at almost any skeletal site and are associated with diverse conditions, including
rheumatoid arthritis,
osteoporosis,
Pagets disease,
osteomalacia or
rickets,
renal osteodystrophy and irradiation. Routine radiography is essential in the diagnosis of stress fractures, but bone scintigraphy has greater diagnostic
sensitivity. On bone scans, such fractures show fusiform, sharply marginated areas of increased
radionuclide activity. In addition, MR imaging is as sensitive as scintigraphy but has superior
specificity in the assessment of stress (insufficiency) fractures. On MR images stress fractures commonly appear as a linear zone of low signal intensity surrounded by a broader, poorly defined area of slightly higher (although still low) signal intensity on T1-weighted spin-echo images and as a linear area of low signal intensity surrounded by a broader region of high signal intensity on T2-weighted spin-echo images. (See
acetabulum (III:1), Fig. 1,
anticonvulsant drugs (III:1), Fig. 1).
DR