DXA（dual–energy X–ray absorptiometry）を用いた人体質量分布計測に基づく脊椎負荷評価法の開発

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Many patients have neck and back pain, and their standing posture (spinal alignment) is sometimes considered to be one of the factors that contributes to such pain. Thus, it would be useful to evaluate spinal loads in that posture. A method to evaluate individual spinal loads using link segment models made from body mass distributions using DXA (dual–energy X–ray absorptiometry) was developed. An element was defined as 1.30 × 1.22 cm, and a detailed body mass distribution consisting of 7473 elements was constructed using DXA equipment (QDR4500). The subjects bodies were divided into cervicofacial (vertex–C7 ⁄ T1), thoracic (C7 ⁄ T1 – T12 ⁄ L1), and lumbar (T12 ⁄ L1 – L4 ⁄ 5) segments. Each mass, M1, M2, and M3, and the center of the masses were calculated. With these parameters and DXA images, each torque, TC7/T1, TT12/L1, and TL4/5, was calculated from the following formulas: TC7/T1 = M1gr1cosθ1, TT12/L1 = M1g (l2cosθ2 + r1cosθ1) + M2gr2cosθ2, and TL4/5 = M1g (l3cosθ3 + l2cosθ2 + r1cosθ1) + M2g (l3cosθ3 + r2cosθ2) + M3gr3cosθ3 (r1, r2, and r3: lengths from the rotation center to each center of mass; l2 and l3: lengths of C7 ⁄ T1 – T12 ⁄ L1 and T12 ⁄ L1 – L4 ⁄ 5; θ1, θ2, and θ3: angles formed between a horizontal line and r1, r2, and r3). In order to reproduce the standing posture on DXA, the standing side was formed by a vacuum cushion for operative position in advance. The parameters from DXA in the lateral view were as follows. In case 1 (38–year–old man, healthy, 164.0 cm and 55.5 kg), they were M1 = 4.50, M2 = 13.24, M3 = 6.92 kg, TC7/T1 = –0.28, TT12/L1 = –3.80, and TL4/5 = –6.42 Nm (facing right, clockwise: positive). In case 2 (76–year–old man, lumbar spondylosis, 156.9 cm and 59.6 kg), they were M1 = 4.83, M2 = 14.27, M3 = 10.34 kg, TC7/T1 = –1.69, TT12/L1 = –16.1, and TL4/5 = –44.3 Nm. In case 3 (71–year–old woman, lumbar spondylosis, scoliosis, 147.2 cm and 49.0 kg), they were M1 = 4.63, M2 = 11.42, M3 = 5.36 kg, TC7/T1 = –2.53, TT12/L1 = –16.0, and TL4/5 = –27.0 Nm. Torques at L4/5 were 6.9 and 4.2 times greater in cases 2 and 3 than in case 1. Total masses calculated from DXA were 54.5, 59.0, and 47.6 kg, and errors between these and actual weights were –1.8, –1.0, and –2.9％, respectively. A method for evaluating spinal loads as torques was developed using DXA. In the future, it will be possible to use this method to evaluate factors such as pain and the effect of rehabilitation. The relationships between torques and various scales (such as pain, depression, ADL, and QOL) need to be examined, taking into account age, sex, muscular strength, etc.

DXA（dual–energy X–ray absorptiometry）を用いた人体質量分布計測に基づく脊椎負荷評価法の開発

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