Extract
Osteoid osteomas are rare, benign tumors. They are differentiated
from osteoblastomas by their size. McLeod et al. defined lesions with a
diameter of =1.5 cm as osteoid osteomas and those with a diameter of
>1.5 cm as
osteoblastomas1.
Approximately 20% of osteoid osteomas occur in the spine, and most involve the
posterior
elements2,3.
Ten percent of those in the spine occur in the vertebral
body4. The lumbar
spine is the most commonly involved
segment3,4.
The rate of associated compensatory scoliosis has been reported to be as high
as 74%; Heiman et al. reported that seventeen (74%) of twenty-three patients
with osteoid osteomas or osteoblastomas had a spinal
deformity4. The
tumor typically is located at or near the concave apex of the
curve5,6.
If the fourth or fifth lumbar vertebra is involved, the apex is typically
cephalad to the lesion and pelvic obliquity is
present5. Asymmetric
pain-provoked muscle spasm on the side of the lesion is thought to be the
cause of the
scoliosis6. Ransford
et al. postulated that the concave-side muscle spasms, if present for long
enough, eventually will cause asymmetric growth inhibition of the vertebral
epiphysis, leading to a rotational deformity and making the curve more
structural7.