Dual-energy X-ray absorptiometry overestimates bone mineral density of the lumbar spine in persons with spinal cord injury

• Published in: Spinal cord 2009-08, Vol.47 (8), p.628-633
• Main Authors: Bauman, W A, Schwartz, E, Song, I S Y, Kirshblum, S, Cirnigliaro, C, Morrison, N, Spungen, A M
• Format: Article
• Language: English
• Subjects: Absorptiometry, Photon; Adult; Anatomy; Biological and medical sciences; Biomedical and Life Sciences; Biomedicine; Bone Density - physiology; Cerebrospinal fluid. Meninges. Spinal cord; Cross-Sectional Studies; Human Physiology; Humans; Injuries of the nervous system and the skull. Diseases due to physical agents; Lumbar Vertebrae - diagnostic imaging; Male; Medical sciences; Middle Aged; Nervous system (semeiology, syndromes); Neurochemistry; Neurology; Neuropsychology; Neurosciences; original-article; Osteoarthritis - complications; Osteoporosis - diagnostic imaging; Osteoporosis - etiology; Spinal Cord Injuries - complications; Spinal Cord Injuries - diagnostic imaging; Tomography, X-Ray Computed; Traumas. Diseases due to physical agents
• ISSN: 1362-4393; 1476-5624
• DOI: 10.1038/sc.2008.169

Background: Bone mineral density (BMD) of the lumbar spine (L-spine) has been reported to be normal or increased in persons with chronic spinal cord injury (SCI). Objective: To determine BMD of the L-spine by dual-energy X-ray absorptiometry (DXA) and quantitative computerized tomography (qCT) in men with chronic SCI compared with able-bodied controls. Design: Cross-sectional, comparative study. Setting: Clinical research unit, Veterans Affairs Medical Center, Bronx, NY, USA and Kessler Institute of Rehabilitation, West Orange, NJ, USA. Methods: Measurements of the L-spine were made in 20 men with SCI and compared with 15 able-bodied controls. The DXA images were acquired on a GE Lunar DPX-IQ. The qCT images of the L-spine were acquired on a Picker Q series computerized tomographic scanner. Results: The mean ages for the SCI and control groups were 44±13 vs 42±9 years, and the duration of injury of the group with SCI was 14±11 years. There were no significant differences between the SCI and control groups for L-spine DXA BMD (1.391±0.210 vs 1.315±0.178 g/m 2 ) or for L-spine DXA T-score (1.471±1.794 vs 0.782±1.481). L-spine qCT BMD was significantly lower in the SCI compared with the control group (1.296±0.416 vs 1.572±0.382 g/m 2 , P =0.05); the T-score approached significance (−1.838±1.366 vs −0.963±1.227, P =0.059). Subjects with moderate degenerative joint disease (DJD) had significantly higher T-scores by DXA than those without or with mild DJD. Conclusion: Individuals with SCI who have moderate to severe DJD may have bone loss of the L-spine that may be underestimated by DXA, reducing awareness of the risk of fracture.