Sacral insufficiency fractures are stress fractures, which are the result of normal stresses on abnormal bone, most frequently seen in the setting of osteoporosis. They fall under the broader group of pelvic insufficiency fractures.
They are usually seen in elderly females who present with low back pain without any history of significant trauma.
They are most frequently seen in the setting of osteoporosis, although any process which weakens bone is a risk factor. Long-term bisphosphonate use has been associated with insufficiency fractures.
Risk factors are those of osteoporosis as well as other abnormal bone conditions, including:
- osteoporosis: most common
- rheumatoid arthritis
- Paget disease
- osteomalacia: milkman syndrome
They may be normal or a sclerotic line may be noted in involved region.
May show a fracture line along with sclerosis that is parallel to the sacroiliac joint, although even CT imaging is less sensitive as compared to MRI and nuclear imaging.
Can depict bone marrow oedema as early as 18 days after the development of symptoms.
Uptake of Tc-99m MDP is also sensitive but not specific. A typical H-sign or Honda sign (uptake in H pattern) may be noted in 20-40% of cases and is considered diagnostic.
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