A Novel Method to Calculate Functional Pelvic Tilt Using a Standing Anteroposterior Pelvis Radiograph

Jeffrey J Frandsen; Joshua P Rainey; Timothy L Kahn; Brenna E Blackburn; Christopher E Pelt; Lucas A Anderson; Jeremy M Gililland

doi:10.1016/j.artd.2023.101145

A Novel Method to Calculate Functional Pelvic Tilt Using a Standing Anteroposterior Pelvis Radiograph

Arthroplast Today. 2023 May 22:21:101145. doi: 10.1016/j.artd.2023.101145. eCollection 2023 Jun.

Authors

Jeffrey J Frandsen¹, Joshua P Rainey¹, Timothy L Kahn², Brenna E Blackburn¹, Christopher E Pelt¹, Lucas A Anderson¹, Jeremy M Gililland¹

Affiliations

¹ Department of Orthopaedics, University of Utah, Salt Lake City, UT, USA.
² St. Mark's Hospital, Salt Lake City, UT, USA.

Abstract

Background: Functional patient-specific acetabular component positioning is important in total hip arthroplasty. We preoperatively evaluate the pelvic tilt (PT) on standing anteroposterior (AP) pelvis radiographs using a novel measurement and then recreate this intraoperatively using imaging. The purpose of this study was to determine if there is a linear correlation between this novel measurement and the actual PT.

Methods: A retrospective study of 200 patients was performed, measuring PT on standing lateral radiographs as the angle between the anterior superior iliac spines and the pubic symphysis. On the AP pelvis radiographs, the trans-teardrop (TT) line was drawn between the teardrops. The vertical distance between the TT line and the top of the pubic symphysis (TTPS) was then measured. A ratio was made between the lengths of both lines to account for the overall size of the pelvis (TTPS/TT). Linear regression analysis was then performed between PT and TTPS/TT.

Results: There was a strong linear correlation between the TTPS/TT ratio on AP pelvis radiographs and PT on lateral radiographs (r = 0.785, r² = 0.616, P < .001). On subanalysis of the female cohort, the correlation became even stronger (r = 0.864, r² = 0.747, P < .001). Using regression analysis, a linear equation was created (PT = 97.32 [TTPS/TT] - 5.51), to calculate the PT using the TTPS/TT ratio.

Conclusions: There is a strong linear correlation between the TTPS/TT ratio and PT. Using this information, a surgeon can reliably use the distance between the TT line and the superior pubic symphysis on an AP radiograph to recreate the patient's functional PT intraoperatively, allowing for a more accurate patient-specific placement of the acetabular component.

Keywords: Anteroposterior pelvic radiograph; Functional pelvic tilt; Pelvic tilt; Spinopelvic disease; Trans-teardrop line; Trans-teardrop to pubic symphysis distance.