Original Research

Prevalence of Low Bone Mineral Density in Younger Versus Older Women With Distal Radius Fractures

Am J Orthop. 2015 December;44(12):E493-E496

References

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To further analyze BMD of specific age groups, we divided patients by decade: 35-39, 40-49, 50-59, 60-69, 70-79, 80-89 years. Among all 6 decades, there were no statistically significant differences between hip z scores (P = .83) (Figure 1). Spearman rank-order correlation test showed a moderate inverse correlation between age and femoral neck BMD (R = –0.42) and t score (R = –0.43). There was a weak correlation between increasing age and decreasing spine BMD, t score, and z score (Rs = –0.27, –0.31, 0.03). There was no correlation between age and femoral neck z score (R = –0.04).

According to the WHO classification system, 11 (23%) of the 47 women in the younger group were osteopenic, and 8 (17%) were osteoporotic, based on spine BMD. Hip BMD values indicated that 20 patients (43%) were osteopenic, and 3 (6%) were osteoporotic. One patient in the younger group had a hip z score of less than –2, and 14 patients (39%) had a hip z score between –2 and –1. Six patients (18%) had a spine z score of less than –2, and 6 patients (18%) had a spine z score between –2 and –1. Of the 81 older patients, 22 (27%) were osteopenic, and 21 (26%) were osteoporotic, according to spine measurements. The femoral neck data indicated that 39 (48%) of the older patients were osteopenic, and 22 (27%) were osteoporotic.

In both groups, mechanisms of injury were identified. Of the 47 younger patients, 26 fell from standing, 7 fell from a height of more than 6 feet, and 14 were injured in motor vehicle collisions (MVCs). Of the 81 older patients, 2 sustained a direct blow, 64 fell from standing, 4 fell from a height of more than 6 feet, and 11 were injured in MVCs. The differences in z scores based on mechanism of injury were not statistically significant (P = .22) (Figure 2).

Discussion

Several studies have shown that older women with DRFs have low BMD in the spine and femoral neck.^8,9 These studies focused on older women who sustained low-energy fractures caused by a fall from a standing height. Studies of younger women with DRFs focused on BMD of the contralateral distal radius, not the spine or femoral neck.^10,11 Those study groups also had low BMD. Findings from a multitude of studies have established that patients who are older than 50 years when they sustain distal radius fragility fractures should be referred for bone densitometry studies, and there is increasing evidence that younger patients with fragility fractures should undergo this evaluation as well.

The present study was designed to expand the range of patients and mechanisms of injury. Women in this study were 35 years or older. In addition to collecting data from patients injured in a fall from standing, we examined the medical records of women injured in MVCs, in falls from heights of more than 6 feet, and from direct trauma to the wrist. We measured the BMD of the spine and femoral neck and of the contralateral distal radius.

For this discussion, several key points should be made about BMD evaluation in younger versus older women. Most organizations caution against using spine BMD in older women. The ISCD, however, recommended measuring both hip and spine BMD; whereas BMD can be falsely elevated by spine osteoarthritis in older patients, spine BMD measurements are accurate in younger patients not affected by osteoarthritis. The ISCD also stipulated that z scores should be used in examining BMD in younger patients. The z score is a value of how many standard deviations BMD differs from a matched population of the same age, sex, ethnicity, and weight. The t score, which is useful in evaluating older patients, compares a patient’s BMD with that of an average 30-year-old.¹²

According to the WHO classification system (intended for older women), osteopenia is indicated by a t score between –1.0 and –2.5, and osteoporosis is indicated by a t score of less than –2.5. In the present study, about 43% of the younger patients (age, 35-50 years) with DRFs were osteopenic, and 6% of these patients were osteoporotic. In concert with previous studies,⁹ 48% of our older women (age, >50 years) with DRFs were osteopenic, and 27% were osteoporotic. The difference in mean spinal z scores between the younger and older groups was not statistically significant (P = .81).

As mentioned, when examining BMD of younger patients, it is imperative to use spine z scores. About 18% of our younger patients had a z score of less than –2, and 18% had a z score between –2 and –1. In our comparison of patients from 5 different age decades (range, 35-79 years), there was no statistically significant difference in z scores (P = .83). In addition, there was no correlation between increasing age and decreasing z score (R = –0.04).