Athirty-one-year-old woman sought medical advice because of three
weeks of pain in the left buttock. The pain started five days after her first
vaginal delivery. The pain was relieved with a self-prescribed treatment of
ibuprofen and remitted soon without medication. She had a history of two
episodes of low-back pain two years previously. Imaging studies did not show
any underlying lesion. During the pregnancy, she gained 15 kg (1.6 kg in the
last week), without complications except for one lower urinary tract infection
that resolved with antibiotic treatment. The patient did not experience pelvic
or spinal pain during the pregnancy, and there was no history of trauma or
endocrine or metabolic diseases. No smoking or use of heparin was reported. At
the end of the fortieth week of the pregnancy, she was admitted after
spontaneous rupture of the membranes. She was in active labor for 9.5 hours.
Epidural analgesia was used. No instruments or unusual maneuvers were used to
deliver a healthy 3125-g baby girl.
On physical examination of the woman at three weeks post partum, the left
sacroiliac joint was painful with the slightest movement with no other
relevant findings. Plain radiographs of the pelvis showed bone density
asymmetry with increased intensity in the left sacral wing. A pelvic magnetic
resonance imaging scan revealed a linear fracture of the left sacral wing
(Fig. 1), as well as an
associated left superior pubic ramus fracture adjacent to the symphysis pubis
(Fig. 2). The results of blood
tests were normal for cell counts, inflammatory markers, calcium, and
phosphorus levels. The results of renal function tests were also normal. The
patient was treated with rest and analgesics. One month later, the pain had
resolved and the clinical outcome was favorable
(Fig. 3).
The cases of only six patients who had a sacral fracture during
pregnancy or the postpartum period have been reported, as far as we
know2-7.
The risk factors for sacral stress fracture during pregnancy and the
postpartum period may include vaginal delivery of a high-birth-weight newborn,
increased lumbar lordosis, excessive weight gain, a rapid vaginal delivery,
selected obstetric maneuvers and forceps
instrumentation2,
and sports activities such as
jogging3. The cases
of only four pregnant women with non-osteoporosis-related sacral fractures
have been
reported4-7.
All of those patients complained of low-back pain during the last trimester or
after delivery, but no risk factors for osteoporosis were identified. A weight
gain of 20 and 22 kg was documented during the pregnancy in two
patients4,6,
and a normal bone density was demonstrated by densitometry in two
patients4,5.
Insufficiency fractures (including vertebral, femoral neck, pelvic, rib,
and wrist fractures) can be the initial manifestation of osteoporosis during
pregnancy or the postpartum
period4,8,9.
Many of these reported cases have occurred in primigravidas who had
osteoporosis develop during the last trimester of pregnancy or shortly after
delivery. However, few patients with a sacral fracture associated with
pregnancyrelated osteoporosis have been
reported10.
Vitamin-D deficiency (osteomalacia) is another cause of nontrauma-related
fracture during pregnancy and the postpartum
period11. However,
in the patient in the present report, the magnetic resonance imaging findings
revealed normal bone-marrow signal intensity
(Fig. 1) and the initial serum
levels of calcium, phosphorus, and alkaline phosphatase were normal (the
absence of renal failure), making the diagnosis of osteoporosis or
osteomalacia extremely unlikely. The absence of relevant risk factors for an
insufficiency or stress fracture makes the diagnosis unclear in this case. We
believe that the work of labor was the only important event, and a
delivery-related stress fracture is the most probable diagnosis in this
patient.
In all of the patients described above, computed tomographic and/or
magnetic resonance imaging scans confirmed the diagnosis. Computed tomography
is both sensitive and specific and seems to be the imaging modality of choice
for evaluating bone structure; however, it is not recommended during
pregnancy. Magnetic resonance imaging studies have similar sensitivity and can
be performed throughout
pregnancy12. In
addition, magnetic resonance imaging can provide an evaluation of the soft
tissues13. On
T1-weighted images, the fracture was seen as a low-intensity line surrounded
by a hypodense region of surrounding osseous edema. On T2-weighted sequences,
the fracture line was seen as a moderate low-intensity signal or isosignal
within the high-intensity-signal area produced by the edema. These fractures
have a low risk of complications; thus, conservative treatment is recommended.
Analgesics and rest until resolution of the pain (usually within three to
eight weeks) should be
recommended3.
In conclusion, delivery-related sacral fracture is an uncommon complication
that should be considered in the differential diagnosis of low-back pain
during the postpartum period. Magnetic resonance imaging is a useful technique
for diagnosis. The prevalence of this complication could be underestimated
since the prevalence of lumbosacral pain following delivery is high and it
usually resolves during the postpartum period. Thus, imaging studies are
rarely performed to investigate these symptoms. ?