Background: It is standard practice for total hip arthroplasty (THA) patients to have post-operative imaging, and one of the reasons is to assess the adequacy of acetabular component position. Correct positioning of the acetabular component is important for successful outcome in THA. Acetabular component position can be measured from either computed tomography (CT) or plain radiographs. While CT is the gold standard for accurately measuring acetabular component position, radiographs are routinely used for post-operative evaluation. However, measurement of acetabular component position from plain radiographs is not straightforward and numerous methods have been proposed. As most imaging is now digital, the aim of this study was to investigate the reliability of one method to measure acetabular component position using a basic diagnostic imaging software program that is readily available to orthopaedic surgeons.
Methods: We investigated the reliability Lewinnek's method using a basic Picture Archiving and Communication System program, InteleViewer ™ . We measured 69 post-operative anteroposterior (AP) radiographs of patients who underwent primary THA. Intra-observer and inter-observer reliability for Lewinnek's method was calculated using the intraclass correlation coefficient.
Results: Our results showed excellent intra- and inter-observer reliability for both inclination (0.99, 95% confidence interval (CI): 0.99-1.0; and 0.97, 95% CI: 0.95-0.99) and anteversion (0.99, 95% CI: 0.98-0.99; and 0.93, 95% CI: 0.89-0.96) measurements.
Conclusion: This study has shown that using Lewinnek's method, acetabular component position can be reliably measured on post-operative AP digital radiographs using readily available software tools.
Keywords: X-ray computed; acetabulum; arthroplasty; hip; replacement; reproducibility of results; software; tomography.