By Nabil A. Ebraheim MD & Dalton Blood MD
The presence of a white vertebral body on lumbar spine x-ray
requires differentiation between Paget’s, Rugger-Jersey spine, and metastatic
prostate carcinoma.
Paget’s disease involves abnormal bone remodeling
characterized by excessive osteoclast bone resorption followed by increased
osteoblast bone formation which is disordered and structurally weaker than
normal, healthy bone. The increased bone turnover causes these patients have an
increased serum alkaline phosphatase and urinary hydroxyproline and urinary N-telopeptide.
Due to rapid, disorganized bone formation, bone samples under the microscope
demonstrate a mosaic pattern and cement lines. The increased osteoblast
activity can also result in cortical thickening. This cortical thickening
increases opacity of the cortex on all sides of the vertebral body combined
with vertebral body expansion and coarsened trabeculae makes the vertebra look
like a picture frame (“Picture frame vertebra body”). In Paget’s disease the
cortex is thickened on all sides of the vertebral body. In contrast, the
Rugger-Jersey spine sclerosis only occurs at the superior/inferior vertebral
endplates.
Rugger-Jersey spine describes the prominent sub-endplate
density at multiple continuous vertebra levels. The alternating sclerotic,
lucent appearance on x-ray looks like the horizontal stripes of a rugby
jersey. These pathogenic changes occur
due to hyperparathyroidism which leads to increased bone resorption with
subsequent loss of bone mass resulting in the lucent areas seen. The dense or
sclerotic areas at the superior and inferior vertebral body endplate result
from excess osteoid accumulation.
While Paget’s disease lesions can appear osteoblastic,
metastatic prostate and breast tumors can also appear as osteoblastic lesions
on x-ray. The diffuse and homogeneous increase in opacity of a vertebral body
that otherwise maintains its size and contours with no change in the adjacent
intervertebral discs is called the “ivory vertebra sign”. This sign often indicates
metastatic prostate cancer in adult males or metastatic breast cancer in
females. An elevated Prostate-Specific Antigen (PSA) and biopsy can confirm the
diagnosis of prostate cancer. The lesion biopsy histology demonstrates
adenocarcinoma with gland formation. The key differences between Paget’s
disease, Rugger-Jersey spine, and metastatic prostate cancer allow for
effective differentiation between these disease processes when presented with a
white vertebra x-ray.
