Krismer M, Bauer R, Tschupik J, Mayrhofer P
Department of Orthopaedics, Medical School, University of Innsbruck, Austria.
J Biomech. 1995 Oct;28(10):1225-36. doi: 10.1016/0021-9290(94)00177-6.
In orthopedics there is a demand for determining migration of hip sockets by evaluation of standard radiographs. In this case problems are caused mainly by changing pelvis positions on the X-ray table at successive exposures. A method (EBRA) is described that evaluates standard AP radiographs without requiring additional means at exposure (e.g. ball markers). Simulating the spatial situation it computes parameters of longitudinal and transverse migration of prosthetic cup and femoral head. A comparability algorithm using a grid of transverse and longitudinal tangents of the pelvis contour divides serial radiographs into sets of comparable ones. Comparability of serial radiographs takes place if the distances of corresponding grid lines do not transcend a given limit L. Migration is measured only between comparable radiographs. Different studies are described concerning the interdependence of pelvis rotations and changes of the grid lines, the degree of pelvis rotations appearing in practice, the choice of the limit L, the properties of the comparability algorithm and the accuracy of EBRA. The 95% confidence limits for EBRA results are 1.0 mm for longitudinal and 0.8 mm for transverse migration.
在骨科领域，需要通过评估标准X线片来确定髋关节臼的移位情况。在这种情况下，主要问题是在连续曝光时患者在X线检查台上骨盆位置发生变化。本文描述了一种方法（EBRA），该方法无需在曝光时使用额外手段（如球形标记物）即可评估标准前后位X线片。通过模拟空间情况，它可以计算假体髋臼杯和股骨头的纵向和横向移位参数。一种使用骨盆轮廓的横向和纵向切线网格的可比性算法将系列X线片分为可比的几组。如果相应网格线的距离不超过给定极限L，则系列X线片具有可比性。仅在可比的X线片之间测量移位。文中描述了关于骨盆旋转与网格线变化的相互依存关系、实际出现的骨盆旋转程度、极限L的选择、可比性算法的特性以及EBRA的准确性的不同研究。EBRA结果的95%置信限为纵向移位1.0毫米，横向移位0.8毫米。
