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Performing a DXA PA Lumbar Spine, Proximal Femur, or Forearm DXA Study

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Bone Densitometry for Technologists

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Abstract

The most commonly studied regions of the skeleton remain to be the PA lumbar spine, proximal femur, and forearm in spite of the development of software applications that allow measurement of virtually any skeletal region. The manufacturers of DXA devices provide instructions for patient positioning for the different types of DXA studies that can be performed utilizing their device and software applications. While the manufacturer’s recommendations for positioning should always be given priority, an understanding of why certain aspects of positioning are recommended is useful. In particular, the technologist who understands the goals of positioning is better able to modify certain aspects of positioning when the patient’s anatomy demands it, without undermining the validity of the study. In reviewing the basic procedures and nuances of positioning for the three major scan types, the following discussion provides both the basic “how to” as well as the more detailed “why.”

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Notes

  1. 1.

     See Chap. 3, Vertebral Anatomy.

  2. 2.

     See Chap. 3, Proximal Femur Anatomy.

  3. 3.

     See Chap. 7, Precision in Bone Densitometry.

  4. 4.

     It is necessary to correct the anteversion in order to bring the femoral neck parallel to scan table. Thus, one might reasonably conclude that the average magnitude of internal rotation necessary to do so would be approximately 20°.

  5. 5.

     The Cobb angle was named after orthopedic surgeon John Robert Cobb, MD (1903–1967). It was originally used to measure the sideways curve of the thoracic or lumbar spine that is called scoliosis, although it is also now used to assess the degree of kyphosis, in which the normal curve of the thoracic spine is accentuated. A Cobb angle of 10° or greater is generally taken as diagnostic of scoliosis, although curves of 25° or less may not require extensive intervention. Curves of 40° or more often require surgical correction.

  6. 6.

     See Chap. 9 for a discussion of the WHO criteria. They are also found in Appendix B.

  7. 7.

     This clearly does not apply to DXA devices which are dedicated forearm devices.

  8. 8.

     A Colles’ fracture is a fracture of the distal radius, named after Abraham Colles (1773–1843), an Irish surgeon, who first described this type of fracture in 1814. The fracture typically occurs when an individual falls on an outstretched arm. The classic Colles’ fracture is described as a transverse fracture of the radius which occurs approximately 1 inch proximal to the radiocarpal joint and results in dorsal displacement and angulation of the radius.

  9. 9.

     The Tromsø Study is a population-based study, conducted in Tromsø, Norway, that focuses on lifestyle-related diseases such as osteoporosis.

  10. 10.

     See Chap. 11, Precision in Bone Densitometry.

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  1. Clinical Research Center of North Texas, Denton, TX, USA

    Sydney Lou Bonnick md, facp, ccd & Lori Ann Lewis mrt, cdt

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  1. Sydney Lou Bonnick md, facp, ccd
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  2. Lori Ann Lewis mrt, cdt
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Bonnick, S.L., Lewis, L.A. (2013). Performing a DXA PA Lumbar Spine, Proximal Femur, or Forearm DXA Study. In: Bone Densitometry for Technologists. Springer, New York, NY. https://doi.org/10.1007/978-1-4614-3625-6_4

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  • DOI: https://doi.org/10.1007/978-1-4614-3625-6_4

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