Lateral spine densitometry in obese women

Area of Science:

• Endocrinology
• Radiology
• Gerontology

Background:

• Lateral (LAT) spine scans are proposed as more sensitive than posterior-anterior (PA) scans for detecting age-related bone loss in normal-weight postmenopausal women.
• Dual energy X-ray absorptiometry (DXA) measurement error for both PA and LAT bone mineral density (BMD) increases with higher body fat percentage and thickness variations.

Purpose of the Study:

• To investigate the influence of obesity on the correlation between paired PA and LAT lumbar (L2-L4) BMD and Z-scores in obese postmenopausal women.
• To determine how adjustments for various obesity metrics affect these correlations.

Main Methods:

• A cross-sectional study involving 30 obese postmenopausal women (mean BMI 33.3 +/- 4.06).
• Paired PA and LAT lumbar BMD and Z-scores were measured using DXA.
• Adjustments were made for body mass index (BMI), percent body fat, fat mass, truncal fat (DXA), waist:hip ratio (WHR), and abdominal fat (CT).

Main Results:

• The correlation between PA and LAT BMD (r = 0.55) and Z-scores (r = 0.57) was lower than previously reported in normal-weight populations.
• After adjusting for obesity indicators, the PA and LAT Z-score correlation improved to r = 0.62.
• The mean LAT Z-score was significantly higher (4.6 times) than the mean PA Z-score in this obese cohort.

Conclusions:

• Obesity significantly affects the correlation between PA and LAT lumbar BMD measurements in postmenopausal women.
• Increased soft tissue and fat inhomogeneity in obese individuals may lead to increased X-ray attenuation, potentially causing LAT scans to overestimate bone loss compared to PA scans.
• These findings suggest that standard interpretation of LAT scans may not be directly applicable to obese postmenopausal women without considering body composition.