Abstract

1. Abstract [Background] Although a number of methods are used to estimate acetabulum anteversion from radiographs of total hip replacements, there is no consensus regarding the accuracy of these methods. This study aims to compare the accuracy of several such measurement methods with simulated radiographs of total hip replacements.   [Methods] With simulator program, we simulate 45 total hip replacement radiographs with 15 different anteversions and randomized inclinations and wear. The anteversions are measured with the Lewinnek method, the Liaw method, the modified Widmer method, and the Fabeck method by one of the authors.   [Results] With simulated radiographs, median errors are 1° with the Liaw and Widmer and Fabeck methods, and 1.23° with the Lewinnek method. Maximum errors are between 2.61° (Lewinnek) and 3° (Liaw, Widmer, and Fabeck). Mean errors are 1.20° with the Lewinnek method, 0.96° with the Liaw method, 1.16° with the modified Widmer method, and 0.89° with the Fabeck method.  [Conclusions] With simulated radiographs, the accuracy of the four methods are comparable. The errors are less than 3°, which are acceptable for clinical evaluations. The Liaw and modified Widmer methods are easier because neither drawing nor caculator is needed. Introduction Lewinnek method measure long axis: l measure short axis: s anteversion= arc sin(s/l) SIC03-P026 Accuracy of Measurement of Acetabulum Anteversion with Radiographs of Total Hip ReplacementsChen-Kun Liaw1,3 Rong-Sen Yang2 Sheng-Mou Hou2 Chiou-Shann Fuh3 Tai-Yin Wu4En Chu Kong Hospital, Taipei Hsian, Taiwan1National Taiwan University Hospital, Taipei, Taiwan2 National Taiwan University, Computer Science and Information Engineering3Taipei City Hospital4 Liaw method Methods • 45 simulated total hip replacement radiographs • 15 different anteversions and randomized inclinations and wear • Measured with the Lewinnek method, the Liaw method, the modified Widmer method, and the Fabeck method • Blind method • Pair t test, p<0.05 as significant. Results With simulated radiographs, median errors are 1° with the Liaw and Widmer and Fabeck methods, and 1.23° with the Lewinnek method. Maximum errors are between 2.61° (Lewinnek) and 3° (Liaw, Widmer, and Fabeck). Mean errors are 1.20° with the Lewinnek method, 0.96° with the Liaw method, 1.16° with the modified Widmer method, and 0.89° with the Fabeck method. There are no stastical difference between these methods. Widmer method Conclusions Fabeck method • All four methods have acceptable results on measuring anteversion. • Liaw and modified Widmer methods are easier because the examiner do not have to draw line on radiographs.