Ellipse method for measuring Liaw’s anteversion of the acetabular component after total hip arthroplasty

Abstract

Background Several cup anteversion measurements for post-operative total hip arthroplasty (THA) surgery have been described. We developed the standardized Liaw’s trigonometric method to eliminate the influence of patient position, which is the most accurate method for cup anteversion measurement. We then developed an ellipse method using the Elliversion software and reported an interobserver error reduction in 2013. In this study, we attempted to apply this ellipse method in the clinic and compared its accuracy with the standard trigonometric version. Methods In the present study, we attempted to incorporate the ellipse method with Liaw’s standardized anteversion in the simulated cup position. We measured standardized Liaw’s anteversion for 434 radiographs in the clinic using the ellipse method. Repeated standard deviation (RSD) was calculated for accuracy evaluation. Furthermore, paired t-test was used for comparison with the interobserver and intraobserver errors. Results We found that the standardized Liaw’s anteversion measured using the ellipse method showed lower RSD than the radiographic version. RSD was 0.795 in the standardized Liaw’s anteversion with ellipse method group. The p-values of the paired t-test were all higher than 0.05 when measuring the interobserver and intraobserver errors. It indicated that the ellipse method was a precise and simple tool for cup anteversion measurement. Conclusion We believe that this ellipse measurement can assist surgeons while placing the acetabulum cup into the precise position and enable early diagnosis of acetabulum loosening.

Degree of Pelvic Rotation in the Coronal Plane on Postoperative Radiographs Obtained after Total Hip Arthroplasty

“…When doctors detect a small but significant cup movement they can possibly minimize the incidence of cup loosening and prosthetic hip dislocation. When early cup loosening is detected, we can warn the patient against an excessive range of motion, or take it as a signal for the need of a cup revision [ 4 ]. We would not revise a cup with an anteversion of only 2.5°, but we would pay more attention and advise the patient not to do any extreme internal rotation of hip to prevent dislocation or impingement.…”

“…However, there was one exception. The standardized Liaw’s anteversion measurement is the only measurement that corrects patient positioning during film acquisition [ 4 , 7 ]. To our knowledge, the standardized Liaw’s measurement is the most accurate method to date [ 4 , 5 , 16 , 17 ].…”

“…In 2019, we invented software to measure the cup anteversion using Elliversion software (Microsoft platform, Windows 11) by drawing the trans-teardrop line (TTDL), the vector from the center of the sacrococcygeal junction to the upper pole of the symphysis pubis in the midline (SCSP), and the edge of the cup [ 4 ]. In this study, we used the same software to measure pelvic rotation.…”

“…THA can relieve pain, restore function, and improve the quality of life in patients with hip pain due to various conditions [ 2 , 3 ]. In addition, the number of primary and revision THA surgeries is expected to increase over the next 20 years due to the aging of the population [ 4 , 5 ].…”

“…The importance of cup anteversion measurement after THA has been well described, including assessing the range of motion, stability, and function [ 7 ]. Furthermore, several methods for measuring cup anteversion have been described, such as Fabeck’s, Lewinnek’s, and Murray’s methods [ 4 , 8 , 9 , 10 ]. Because pelvic radiographs are taken by different technicians at different time points, the patient’s position could not be the same every time.…”