Kyphosis most often caused by disk degeneration, not osteoporotic vertebral fractures

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Apr 12, 2004

Kyphosis most often caused by disk degeneration, not osteoporotic vertebral

fractures

La Jolla, CA - Images of exaggerated forward curvature of the spine known as

kyphosis or " dowager's hump " have been widely used in sales pitches for

osteoporosis drugs, but new data from the Rancho Bernardo Study show that

kyphosis is more often due to intervertebral disk degeneration than to

vertebral fractures or osteoporosis, Dr Diane L Schneider and colleagues

report in the April 2004 Journal of Rheumatology[1].

" We expected to find degenerative disk disease, but we didn't expect it to

be more of a marker of kyphosis than osteoporotic fracture. "

" We were [surprised by the findings] because we expected kyphosis to be a

really good marker for fracture. Since this is an older population, we

expected to find degenerative disk disease, but we didn't expect it to be

more of a marker of kyphosis than osteoporotic fracture, " co-author Dr

G von Mühlen (University of California, San Diego) tells rheumawire.

Researchers surprised by findings

The study cohort comprised 553 men and 854 women aged 50 to 96 years from

Rancho Bernardo, California, and represented 80% of community-dwelling

residents. Participants attended a 1992 through 1996 research clinic visit

where bone mineral density (BMD) of the hip and spine was measured and

lateral thoracolumbar spine radiographs were obtained. Researchers measured

the degree of kyphosis with the modified Cobb method. Degenerative disk

disease without thoracic vertebral fracture was observed in 56.7% of women

and 45.4% of men. Thoracic vertebral fracture with or without degenerative

disk disease was seen in 22% of women and 20.6% of men. The mean

age-adjusted Cobb angle was significantly higher in men and women with

vertebral fractures, compared with those without vertebral fractures.

The prevalence of vertebral fracture increased with higher Cobb angles and

the proportion of women with osteoporosis increased with the increase of

Cobb angle, the study showed. The prevalence of thoracic vertebral fractures

evaluated by quartile of Cobb angle increased with higher Cobb angles, but

even in the upper quartile of the Cobb angle distribution (greater than or

equal to 55.5 degrees), only 36.2% of men and 36.9% of women had prevalent

thoracic vertebral fractures. Moreover, only 9.7% of men and 32.7% of women

in that quartile had osteoporosis at the hip using the World Health

Organization's BMD criteria.

" Nearly two-thirds of the women and men in the fourth quartile of Cobb angle

had no evidence of thoracic vertebral fractures. The absent sex difference

in the percentage with degenerative disk disease or vertebral fractures was

an unexpected observation, " the researchers write.

The relation between disk deterioration and kyphosis was examined previously

by Goh et al, who found that 86% of the variability in overall Cobb angle in

93 spines was due to unfractured " wedging " of the vertebrae and degeneration

of the anterior fibers of the annulus fibrosus[2].

" We would like rheumatologists to still think about osteoporosis and

vertebral fracture, but also consider that other conditions can be

responsible for kyphosis, " von Muhlen says. " They should consider

osteoporosis an osteoporotic fracture, but should also consider other

diseases like degenerative disk disease. "

Rheumatologists shouldn't jump to conclusions

" Kyphosis per se should not be considered diagnostic of osteoporosis.

Nevertheless, patients with exaggerated kyphosis should be evaluated for

underlying osteoporotic fracture, " the researchers conclude.

In the future, the Rancho Bernardo study group plans to investigate the

genetics of osteoporosis. " We are focusing a lot on the genetics and the

newest medications on the market and what happens to the very old people, "

von Mühlen says.

Dr Ricciardi (Long Island College Hospital/Continuum Health Partners

Brooklyn, NY), who reviewed the study for rheumawire, says, " The most

important thing [in this study] is that kyphosis is not synonymous with

osteoporosis. " He would like to see a similar study conducted on older

postmenopausal women with kyphosis.

Ricciardi adds, " I do think general practitioners think kyphosis equals

osteoporosis and as soon as they see it, they think patients are at high

risk for osteoporotic fracture. "

Mann

Sources

1. Schneider DL, von Muhlen DG, Barrett-Connor E, Sartoris DJ. Kyphosis does

not equal vertebral fractures: the Rancho Bernardo Study. J Rheumatol 2004;

31:747-752.

2. Goh S, Price RI, Leedman PJ, Singer KP. The relative influence of

vertebral body and intervertebral disc shape on thoracic kyphosis. Clin

Biomech (Bristol, Avon) 1999 Aug; 14(7):439-48.