A separation of the pubic symphysis without concomitant fracture constitutes pubic diastasis.
Excessive lateral or anterior movement can be seen secondary to pubic diastasis and this can further lead to pubic symphysis dysfunction.
- patient’s legs will involuntarily move apart
- pregnancy and childbirth
- bladder exstrophy
- prune belly syndrome
- osteogenesis imperfecta
- cleidocranial dysostosis
A width of >10 mm is considered diagnostic. Involvement of the sacroiliac (SI) joints must be assessed.
The normal width differs for different ages and whether measurement is with CT or x-ray. At age 20 the width measures ~6 mm on x-ray and at age 50 is measures ~3 mm. Women tend to have a thicker fibrocartilaginous disk that allows a higher mobility of the pelvic bones and assists in childbirth. During pregnancy, due to the presence of certain hormones like relaxin, the gap in the symphysis pubis can increase by 2-3 mm.
On pelvic radiographs:
- abnormally wide gap between the pubic bones
- instability may be seen on standing / flamingo position
- on standing, vertical displacement of >10 mm indicates instability of pubic symphysis
- >20 mm displacement is most often associated with sacroiliac (SI) joint involvement
Pediatric normal measurement on x-ray
- age 2-5: 6.3 mm
- age 6-11: 5.9 mm
- age 12-15: 5.7 mm
- separation of the symphysis can be very well appreciated
- sacroiliac joints can also be assessed
- other bones can be assessed well in case of trauma
Pediatric normal measurements on CT
- age 2-5: 5.1 mm
- age 6-11: 4.9 mm
- age 12-15: 4.5 mm
- separation of the joint is well appreciated
- soft tissue injury and inflammation of the subchondral region and bone marrow is demonstrated better
Bone scan and ultrasound have been shown to have a role, with the former used for assessing bony inflammation and the latter for assessing the symphyseal widening, especially in cases of pregnancy.
Treatment and prognosis
This condition is most often treated conservatively and stabilization of the pelvis with a pelvic belt or brace may be done, coupled with muscle strengthening. Analgesics and anti-inflammatory medications may be used for symptomatic relief of pain.
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