Effect of increased axial rotation angle on bone mineral density measurements of the lumbar spine.
BACKGROUND
Osteoporosis frequently occurs in elderly people and is commonly associated with neuromuscular diseases or severe cerebral palsy. Osteoporosis can cause pain via compression fractures or secondary neurologic deficits; thus, accurate evaluation of bone mineral density (BMD) is essential for the prevention and treatment of osteoporosis. However, spinal axial rotation caused by scoliosis may affect the outcome of BMD tests, such that BMD measurements may be significantly greater than actual BMD in patients with severe scoliosis of the spine.


OBJECTIVE
We investigated the effect of axial rotation angle on BMD measurements of the phantom spine.


METHODS
Investigation for the effect of axial rotation with aluminum phantom spine.


METHODS
A GE-Lunar Aluminum Spine Phantom was used to assess BMD. Bone mineral content (BMC), BMD, and cross-sectional area were measured 100 times at L1-L4 using a GE Lunar Prodigy Vision system. Dual-energy X-ray absorptiometry was performed at axial rotation angles of 0° to 25° (5° intervals).


RESULTS
Cross-sectional area decreased and BMD values increased as the axial rotation angle increased, whereas BMC did not change significantly. A fitting function was obtained to evaluate the relationships among axial rotation angle, cross-sectional area, and BMD. We obtained an equation to estimate BMD at L1-L4: 1.000-0.001674x+0.0001043x(2)-0.000005333x(3), where x denotes the axial rotation angle. We found that the observed BMD needed adjustment when the angle was more than 5°.


CONCLUSIONS
Bone mineral density values may be overestimated in patients with even slight (>5°) axial rotation. When osteoporosis is suspected in a clinical setting, the degree of axial rotation should be measured on a lumbar spine X-ray.
Department of Internal Medicine, Pusan National University School of Medicine, Gudeok-ro 179, Seo-gu, Busan 602-739, Korea; Medical Research Institute, Pusan National University, Gudeok-ro 179, Seo-gu, Busan 602-739, Korea.
Yun Kyung
YK
Jeon
Medical Research Institute, Pusan National University, Gudeok-ro 179, Seo-gu, Busan 602-739, Korea; Department of Rehabilitation Medicine, Pusan National University Hospital, Pusan National University School of Medicine, Gudeok-ro 179, Seo-gu, Busan 602-739, Korea.
Myung Jun
MJ
Shin
Medical Research Institute, Pusan National University, Gudeok-ro 179, Seo-gu, Busan 602-739, Korea; Department of Rehabilitation Medicine, Pusan National University Hospital, Pusan National University School of Medicine, Gudeok-ro 179, Seo-gu, Busan 602-739, Korea. Electronic address: yi0314@gmail.com.
Yong Beom
YB
Shin
Department of Statistics, Pusan National University, Busandaehak-ro, 63beon-gil, Geumjeong-gu, Busan 609-735, Korea.
Choong Rak
CR
Kim
Medical Research Institute, Pusan National University, Gudeok-ro 179, Seo-gu, Busan 602-739, Korea; Department of Nuclear Medicine, Pusan National University School of Medicine, Gudeok-ro 179, Seo-gu, Busan 602-739, Korea.
Seong-Jang
SJ
Kim
Department of Rehabilitation Medicine, Pusan National University School of Medicine and Pusan National University Yangsan Hospital, Beomeo, Mulgeum, Yangsan, Gyeongnam, Korea; Research Institute for Convergence of Biomedical Science and Technology, Pusan National University Yangsan Hospital, Beomeo, Mulgeum, Yangsan, Gyeongnam, Korea.
Hyun Yoon
HY
Ko
Department of Internal Medicine, Pusan National University School of Medicine, Gudeok-ro 179, Seo-gu, Busan 602-739, Korea; Medical Research Institute, Pusan National University, Gudeok-ro 179, Seo-gu, Busan 602-739, Korea.
In Joo
IJ
Kim
D015502:Absorptiometry, Photon; D015519:Bone Density; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging*; D010024:Osteoporosis / Q000150:complications / Q000175:diagnosis / Q000000981:diagnostic imaging*; D019047:Phantoms, Imaging; D012600:Scoliosis / Q000150:complications / Q000000981:diagnostic imaging*; D013131:Spine / Q000000981:diagnostic imaging*
Axial rotation; Bone mineral density; DXA Scan; Lumbar spine; Phantom; Scoliosis