Bone Density Report Is Normal but Fracture Suggests Otherwise

July 8, 2020

Patients with suspected osteoporotic fractures and normal DXA rarely have normal bone, shows a new study.

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Patients experiencing fractures at the hip and spine considered likely to be osteoporosis rarely have normal bone, even when dual-energy X-ray absorptiometry (DXA) measurements suggest that they do, a study published in the Archives of Osteoporosis shows.

The researchers looked at other clinical data available in the patients records, including femoral trochanter and radius 0.3/ultradistal DXA T-scores, lumbar spine trabecular bone score (TBS), lumbar vertebral opportunistic CT, and femoral cortical index, and found that this additional information could give a more complete picture and inform clinical decisions regarding osteoporosis therapy.

“Patients with normal spine and hip BMD who sustain fracture rarely have normal bone when all available data are considered,” says author Dr. Sindhura Bandaru, of the University of Wisconsin School of Medicine and Public Health in Madison. “These data indirectly support recommendations that postmenopausal women and men age 50 and older with a hip or vertebral fracture should receive osteoporosis medication as their bone is rarely normal.”

The researchers accessed the medical records of 387 patients who sustained hip or spine fractures, were evaluated by a fracture liaison service and received spine and hip DXA. From this group they identified 32 (8.3%) in whom the spine and/or hip BMD reported had been normal.

Other clinical bone data were available in the medical records of 30 out of the 32 patients. These clinical bone data included 0.3 and ultradistal radius T-scores, trochanteric T-scores, lumbar spine trabecular bone score (TBS), L1 opportunistic CT Hounsfield units (HU), and femoral cortical index (FCI).

When all the additional data available for skeletal assessment were considered, only 5/387 (1.3%) were considered to have normal bone. And, Dr. Bandarua emphasised: “It is plausible that even some of these few might have had abnormal bone if additional imaging studies were available.”

The remaining 27 patients with normal DXA results, had atleast one value in their record which suggested abnormal bone. Ultradistal and 0.3 radius results were available in 21 patients, and 18 of these (85.7%) had T-scores < − 1.0. Trochanteric T scores were available for 16 patients and these T-scores were < − 1.0 in 18.8% of patients. Lumbar spine trabecular bone score data were available for 24 patients, and the scores showed that 41.7% had vertebrae with partially degraded or degraded values. Lumbar opportunistic CT was available for 25 patients, and 80% were below normal and < 150 HU. Finally, the femoral cortical index was measurable in 9 subjects, of which 66.7% were below < 0.4.

Not all patients returned abnormal results for all tests, Dr. Bandarua pointed out. “We believe this is to be expected, given that these methods assess skeletal sites with differing proportions of cortical and trabecular bone and that trabecular bone is lost more rapidly after menopause is widely recognized resulting in diagnostic discordance when multiple skeletal sites are measured.”

It was also likely that some tests had differential sensitivity and precision which impacted on reproducibility, she added. “As such, we believe it appropriate that clinicians characterize their fracture patients’ bones as abnormal if any of these tests are low.”

Clinicians who are reluctant to utilize osteoporosis medications in fracture patients with normal spine and hip DXA are advised to seek additional data or testing evaluating bone status in such individuals, Dr. Bandaru said. “Such data is often readily available in the Emergency Room with no additional cost or radiation exposure.”

She added: “In patients who sustain fracture with a fall and are reported to have normal BMD based on standard hips/spine DXA, it is important to first assess for DXA errors and subsequently further evaluate to see if the bone is truly normal as such knowledge may be important in treatment decisions, especially whether to utilize pharmacotherapy to decrease the subsequent fracture risk.”

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REFERENCE

Bandaru, S., Hare, K., Krueger, D. et al. "Do patients that fracture with normal DXA-measured BMD have normal bone?" Arch Osteoporos15, 70 (2020). https://doi.org/10.1007/s11657-020-00745-0