Goh J C, Low S L, Bose K
Department of Orthopaedic Surgery, National University of Singapore, National University Hospital.
Calcif Tissue Int. 1995 Nov;57(5):340-3. doi: 10.1007/BF00302069.
Precision in femoral neck scans with dual energy X-ray absorptiometry (DXA) is affected by variability in positioning and subsequent repositioning of the femur for repeated scans. To study the in vitro effect of femoral rotation on the bone mineral density (BMD), four fresh-frozen cadaveric femurs were fixed in a specially designed jig which allows for rotation of the femurs. BMD measurements of the femurs were done in neutral position (0 degrees) i.e., with the femoral neck axis parallel to the surface of the couch and at 15 degrees, 30 degrees, and 45 degrees of internal and external rotation. In vivo precision of the femoral neck scan was determined in five normal male subjects. The scans were first done with the legs positioned using the manufacturer's foot block. Five scans were performed, with repositioning, on the left hip of each subject. The procedure was then repeated with the legs positioned using a custom-designed positioning jig to minimize the rotation of the hips during a scan. In the in vitro study, the femoral neck BMD value was minimum at neutral position (0 degrees) and increased when the femur was rotated internally or externally. In vivo precision error of the femoral neck scan was reduced by almost 50% with the use of the positioning jig when compared with the manufacturer's foot block. Femoral rotation was shown to have a significant effect on BMD measurements, and proper positioning of the femur during a scan can improve precision significantly.
双能X线吸收法（DXA）进行股骨颈扫描时的精度会受到股骨定位及后续重复扫描时重新定位的变异性影响。为研究股骨旋转对骨矿物质密度（BMD）的体外影响，将四根新鲜冷冻的尸体股骨固定在一个专门设计的夹具中，该夹具可使股骨旋转。在中立位（0度），即股骨颈轴线与检查床表面平行时，以及在15度、30度和45度的内旋和外旋角度下对股骨进行BMD测量。在五名正常男性受试者中测定了股骨颈扫描的体内精度。首先使用制造商提供的足部垫块对腿部进行定位后进行扫描。对每个受试者的左髋部进行了五次扫描，并重新定位。然后使用定制设计的定位夹具对腿部进行定位，重复该过程，以尽量减少扫描过程中髋部的旋转。在体外研究中，股骨颈BMD值在中立位（0度）时最低，当股骨进行内旋或外旋时会升高。与使用制造商的足部垫块相比，使用定位夹具时股骨颈扫描的体内精度误差降低了近50%。研究表明，股骨旋转对BMD测量有显著影响，扫描过程中股骨的正确定位可显著提高精度。
