Plain radiographs can be useful in estimating lumbar bone density.

On standard lateral roentgenograms of the lumbar spine, a decrease in bone density is said to be detectable only after a bone loss of about 40%. To evaluate this view, we compared findings on plain films with bone mineral content of L1 determined by quantitative computed tomography in 80 healthy subjects with a mean age of 60 years. The highest correlations with bone mineral content were found for the criteria "vertebral density versus soft tissue" (r = 0.5, p less than 0.0001), the "amount of trabeculations" (r = 0.49, p less than 0.0001), and for the "overall" estimate of osteopenia in the vertebra (r = 0.55, p less than 0.0001). Surprisingly, these three radiographic criteria proved to be most helpful in subjects with bone mineral content above 110 mg/cm3 (nonosteoporotic range). We conclude that lateral radiographs of the lumbar spine can provide a rough estimate of bone density in nonosteoporotic subjects which may be helpful in determining when further analysis with more precise methods is appropriate.