Bone Mineral Density (BMD) of Ultra-distal Radius: Are we Ignoring Valuable Information?

Background:
BMD measurement of a non-dominant arm is not routinely performed during dual-X-ray-absorptiometry (DXA) test. While 1/3 radius measurement is recommended under certain circumstances, ultra-distal compartment is not used for osteoporosis diagnosis or fracture risk assessment.

Aim:
To evaluate the correlation of ultra-distal radius (UDR) BMD to prevalent fractures, fracture risk predicted by FRAX and diagnosis of osteoporosis by traditional sites.

Methods:
Women who underwent a routine DXA (including non-dominant forearm in all patients) in a tertiary medical center were included in a retrospective cross-sectional study. Risk factors relevant to FRAX calculation were assessed via a self-administered questionnaire.

Spearman correlation of UDR BMD to 10-year risks of major osteoporotic and hip fractures (assessed by FRAX) was explored. The possible added value of UDR BMD in explaining prevalent osteoporotic fractures was assessed using a multivariable regression model incorporating age and traditional osteoporosis diagnosis.

Results:
The study included 1,245 women with a median age of 66 (IQR 59-73), of whom 298 (24%) had UDR T-score ≤ -2.5 and 154 (12%) reported prior fractures. UDR BMD was significantly negatively correlated with FRAX risk score for hip and major osteoporotic fractures (R= -0.5 and R= -0.41 respectively; P<0.001). UDR T-score ≤ -2.5 was associated with higher fracture prevalence (19% vs 10%; P<0.001), and remained significant after adjusting for traditional BMD and age (OR 1.49, 1.01-2.19; P=0.043).

Conclusions:
UDR BMD correlates both with prior fractures and with predicted fracture risks and might pose added value over traditional DXA sites.