Vertebral fractures: how large is the silent epidemic?

How large is the silent epidemic?

The ascendancy of osteoporosis to its present status as a leading health problem has led, finally, to the critical study of vertebral fractures. Although these have long been attributed to osteoporosis, only recently have epidemiological data confirmed that low bone mineral density is their most important determinant. [1,2] Large prospective studies have suggested that the risk of sustaining a new vertebral fracture more than doubles with each decrease of one standard deviation in bone mineral density of the lumbar spine. [3,4]

Falls, so prominent in the pathogenesis of fractures of the hip and distal forearm, do not play such a large part in causing vertebral fractures because the spine is subjected to substantial loads during daily activities such as bending forward, lifting objects, and climbing stairs; vertebral fractures result uniquely from such loading.[5,6] Despite the strength of the association between bone mineral density and vertebral fracture the overlap between bone density in patients with vertebral fractures and that in control subjects without fractures is sufficiently large for vertebral fracture to be diagnosed reliably only from radiographs. Densitometry is more appropriately used to assess the future risk of fracture.[7]

Assessment of the impact of vertebral fractures has been hampered by the absence of formal criteria for identifying fractures in radiographs of the thoracolumbar spine. Even in early case series three patterns were recognised: wedge, crush, and end plate (biconcave) fractures. Since then the means of defining vertebral fractures have evolved through several stages. Initial methods, relying on subjective radiological assessment, [8] gave way to morphometric measurement cut off values.[9] As each vertebral body in the spinal column has unique dimensions [1,10] recent analyses have focused on deriving the distribution of vertebral dimensions at each spinal level and calculating cut off values from these.[11,12]

The most widely adopted thresholds for defining and grading fractures denote moderate (or grade 1) fractures as deformities that fall between three and four standard deviations from the mean values specific to each vertebra, and severe (or grade 2) fractures as those that fall four standard deviations or more from this mean." When morphometric studies are done without reference to clinical presentation the abnormalities found are usually referred to as deformities rather than fractures.

The application of recently developed morphometric techniques to various population samples in the United States has permitted estimation of the incidence of new vertebral fractures in the general population. One recent estimate of the age adjusted incidence among white American women aged 50 and...