Sacral Insufficiency Fracture
Epidemiology
This condition classical affects osteoporotic elderly women. The mean age is 70-75, with almost all patients older than 55.[1]
Other risk factors include prior pelvic radiation (prevalence 21-89%), prolonged glucocorticoid use, rheumatoid arthritis, multiple myeloma, Paget disease, renal osteodystrophy, and hyperparathyroidism. [1]
Anatomy
- Main article: Sacrum
The sacrum has three zones
Pathology
Insufficiency fractures are a subtype of stress fracture where normal stress is applied to bone with reduced elastic resistance. This is usually due to osteoporosis. Other causes of insufficiency fractures are metastatic disease and bone marrow infiltration processes.
They most commonly affect the sacral ala, in a sagittal line lateral to the sacral foraminae and medial to the sacral iliac joints, called zone 1. There is an equal prevalence of unilateral versus bilateral fractures. In some cases there is a fracture line component in the axial plane.
The reason that the sacral ala are affected is because in osteoporosis there isn't uniform bone loss. There is relatively increased loss of bony trabeculae in the sacral alae compared to the vertebra bodies.
There is a high prevalence of concomitant fractures of the pubic rami and parasymphyseal region. There can also be additional fractures in the superior acetabulum and iliac wing. It is thought that the sacral ala fractures happen first which then results in a cascade of abnormal biomechanics resulting in fractures elsewhere.
Clinical Features
History
In two thirds of patients there is no trauma, and when there is trauma it is usually minor. Patients will commonly have diffuse low back pain with radiation to the buttock, hip, or groin. 45% of patients have a history of malignancy.[1]
Examination
There may be lumbosacral spine tenderness. There is usually no neurological deficit, however rarely patients can manifest with a sacral radiculopathy or even cauda equina syndrome.
Investigations
Almost all patients will have severe osteopenia on DEXA imaging.
- ↑ 1.0 1.1 1.2 Lyders, E. M.; Whitlow, C. T.; Baker, M. D.; Morris, P. P. (2010-02). "Imaging and treatment of sacral insufficiency fractures". AJNR. American journal of neuroradiology. 31 (2): 201–210. doi:10.3174/ajnr.A1666. ISSN 1936-959X. PMC 7964142. PMID 19762463. Check date values in:
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