Sex difference in the validity of vertebral deformities as an index of prevalent vertebral osteoporotic fractures: A population survey of older men and women

Morphometric methods have been developed for standardized assessment of ver tebral deformities in clinical and epidemiologic studies of spinal osteopor osis. However, vertebral deformity may be caused by a variety of other cond itions. To examine the validity of morphometrically assessed vertebral defo rmities as an index of osteoporotic vertebral fractures, we developed an al gorithm for radiological differential classification (RDC) based on a combi nation of quantitative and qualitative assessment of lateral spinal radiogr aphs. Radiographs were obtained in a population of 50- to 80-year-old Germa n women (n = 283) and men (n=297) surveyed in the context of the European V ertebral Osteoporosis Study (EVOS). Morphometric methods (Eastell 3 SD and 4 SD criteria, McCloskey) were validated against RDC and against bone miner al density (BMD) at the femur and the lumbar spine. According to RDC 36 per sons (6.2%) had at least one osteoporotic vertebral fractures among 516 (88 .9%) nonosteoporotics 154 had severe spondylosis, 132 had other spinal dise ase and 219 had normal findings; 14 persons (2.4%) could not be unequivocal ly classified, The prevalence of morphometrically assessed vertebral deform ities ranged from 7.3% to 19.2% in women and from 3.5% to 16.6% in men, dep ending on the stringency of the morphometric criteria. The agree ment betwe en RDC and morphometric methods was poor. In men, 62-86% of cases with vert ebral deformities were classified as nonosteoporotic (severe spondylosis or other spinal disease) by RDC, compared with 31-68% in women. Among these, most had wedge deformities of the thoracic spine. On the other hand, up to 80% of osteoporotic vertebral fractures in men and up to 48% in women were missed by morphometry, in particular endplate fractures at the lumbar spine . In the group with osteoporotic vertebral fractures by RDC the proportion of persons with osteoporosis according to the WHO criteria (T-score <-2.5 S D) was 90.0% in women and 86.6% in men, compared with 67.9-85.0% in women a nd 20.8-50.0% in men with vertebral deformities by various methods. Althoug h vertebral deformities by most definitions were significantly and inversel y related to BMD as a continuous variable in both sexes [OR; 95% CI ranged between (1.70; 1.07-2.70) and (3.69: 1.33-10.25)], a much stronger associat ion existed between BMD and osteoporotic fractures defined by RDC [OR; 95% CI between (4.85; 2.30-10.24) and (15.40; 4.65-51.02)]. In the nonosteoporo tic group individuals with severe spondylosis had significantly higher BMD Values at the femoral neck (p<0.01) and lumbar spine (p<0.0004) compared wi th the normal group. On the basis of internal (RDC) and external (BMD) vali dation, we conclude that assessment of vertebral osteoporotic fracture by q uantitative methods alone will result in considerable misclassification, es pecially in men. Criteria for di differential diagnosis as used within RDC can be helpful for a standardized subclassification of vertebral deformitie s in studies of spinal osteoporosis.