Osteoporosis - Spinal Imaging and Image Analysis - page 68

bisphosphonates and anti-receptor activator of NF- κ B ligand (RANKL) have

demonstrated to ef ciently reduce the incidence of osteoporotic fractures [ 13 , 14 ].

Therefore, the Fracture Risk Assessment Tool (FRAX) has been introduced which
uses easily obtainable clinical risk factors to estimate a 10-year fracture probability
in order to provide a better clinical guidance for treatment decisions [ 15 , 16 ]. Age,
sex, weight, height, personal history of fracture, parental history of hip fracture,
smoking status, glucocorticoid intake, rheumatoid arthritis, secondary osteoporosis,
alcohol use, and femoral BMD value are inquired for this purpose. Bone turnover
markers may be useful for monitoring osteoporosis treatment, e.g. annual infusion
of zoledronic acid reduced bone turnover markers and explained much of the
observed fracture risk reduction [ 17 ]. However, measurements of bone turnover
markers are not included in algorithms for fracture risk prediction at the moment
due to the lack of data [ 18 ].
The most important role of osteoporosis imaging at the spine is the correct
assessment of vertebral fracture status and BMD measurements, which are outlined
in the following two sections. FRAX does not directly assess bone strength and
quality, parameters in particular important for monitoring drug effects. Therefore,
imaging techniques measuring bone microstructure and bone marrow fat content,
which have been already used or have been emerging to predict bone strength and
assess bone quality, are presented in the last sections of this chapter.

3 Diagnosis of Osteoporotic Vertebral Fractures

A prevalent osteoporotic fracture increases the risk of a subsequent fracture,
independent on BMD [ 19 22 ]. Therefore, the correct diagnosis and reporting of

prevalent osteoporotic vertebral fractures by radiologists is highly important to
initiate appropriate therapy. Osteoporotic vertebral fractures most commonly occur
between thoracic vertebra 5 (T5) and lumbar vertebra 5 (L5).
Several scoring methods for osteoporotic vertebral fractures have been intro-
duced [ 23 ]. Quantitative morphometry (QM) obtains ratios from direct vertebral
body height measurements to de

-

ne osteoporotic vertebral fractures. Semiquanti-
tative (SQ) methods are based on the visual grading of fractures by using speci c

height and area reduction criteria. The algorithm-based qualitative (ABQ) method
outlines a scheme to systematically rule out non-fracture deformities and diagnoses
osteoporotic vertebral fractures based on endplate depression.
QM measures anterior, middle, and posterior vertebral body heights and cal-
culates ratios between these heights [ 24 , 25 ]. Vertebral fractures are de ned by

thresholds, e.g. three standard deviations difference in height ratios from normal
population means or generally 15 % reduction in height ratios [ 26 ]. The advantages
of the QM scoring systems are the better reproducibility and objectivity compared
to the SQ and ABQ methods. The drawback of QM is the relatively high expen-
diture of time which is critical in clinical routine.