[Comparison of differences between hip and lumbar bone mineral density in dual energy X-ray absorptiometric data]

To explore the changes and regulations in T-scores of hip and lumbar vertebrae in different aged people through retrospective data analyses of dual energy X-ray absorptiometry (DXA) and improve their reference values.

With the aid of DXA, the bone densities of hip (femoral neck) and lumbar (L1-L4) bones were measured in 3662 males and females over 45 years old. There were 9 female and 9 males groups based upon the stratifications of gender and 5-year age intervals (> 85-year-olds combined as one group). After ruling out the "single-part test" data, the T-score averages were calculated and their differences analyzed by t-test.

In females, T-scores of hip and lumbar bone mineral density were basically the same before 50 years old. Significant differences existed between 51 and 75 years old females. The lumbar T-scores were lower than their hip counterparts. In some age groups, T-scores of lumbar vertebrae showed decreased bone mass while those of hip remained normal. However, T-scores of lumbar vertebrae might be diagnosed by osteoporosis but decreased bone mass of hip was absent in the other age groups. After 75 years, no obvious differences existed between hip and lumbar bone T-scores; in all male groups, hip T-scores were lower than lumbar counterparts. There were small changes in T-scores of lumbar vertebrae with aging while the hip ones decreased gradually; each group had a single measurement rate of skeletal site. In females, the minimal and maximal values of single site measurement rate were 12.50% and 63.98% versus 16.68% and 44.50% in males.

Differences of lumbar and hip T-scores exist in some age groups. Thus some normal T-scores of one skeletal site may be abnormal at another site. While evaluating one particular site, one should consider these differences to avoid an incorrect diagnosis.