Petersen T D, Rohr W
Clin Orthop Relat Res. 1987 Jun(219):112-9.
Accurate assessment of total hip and knee alignment requires a single-exposure weight-bearing roentgenogram of the involved limb. The problem with single-exposure technique is that a good exposure of the hip overexposes the lower leg. This problem is solved by using leaded acrylic wedges, which, when placed in front of the X-ray tube (collimator), block excessive radiation to the lower limb and create an evenly exposed film of the entire lower extremity. The development of these collimator wedge filters and the advent of newer fast-speed film and screens have reduced the amount of radiation absorbed by the patient by eight times or more. Guided by a chart to interchange and choose between film/screen combinations, the method and technique provides the surgeon with an exact alignment of the limb and joints for all kinds of operations.
准确评估全髋关节和膝关节的对线情况需要对受累肢体进行单次曝光负重X线片检查。单次曝光技术的问题在于，髋关节的良好曝光会使小腿过度曝光。使用铅制丙烯酸楔形板可解决此问题，将其放置在X射线管（准直器）前方时，可阻挡对下肢的过多辐射，并使整个下肢得到均匀曝光的胶片。这些准直器楔形滤光片的开发以及新型高速胶片和增感屏的出现，已使患者吸收的辐射量减少了八倍或更多。该方法和技术在胶片/增感屏组合的互换和选择图表的指导下，为外科医生提供了用于各种手术的肢体和关节的精确对线情况。
