How deep acetabular cup can be positioned from transverse acetabular ligament to have an ideal inclination?

Abstract

Introduction: Acetabular component positing is the major deterministic step that defines the outcome following total hip replacement. Although various methods exist to measure and maintain cup inclination, intraoperative landmarks always guide to get the individual native inclination. This study aims to estimate the safe cup depth from the transverse acetabular ligament to get an ideal cup inclination.Methodology: This is a prospective study conducted between 2017-2019. Patients who underwent uncemented total hip replacement for reasons other than hip dysplasia were included in the study. Modified Hardinge approach was used in all the cases. Archbold grading of TAL was done intra-operatively. The distance of the inferior rim of the cup to the TAL is measured and cup inclination is measured in post-operative radiograph with reference to the inter-teardrop line in anteroposterior radiograph of the hip. Correlation between cup depth and inclination is calculated by Spearman’s correlation and regression curve analysis was used to analyze the results. Results: We included 35 patients in our study and TAL was identified in all the cases and the mean radiological inclination achieved was 41.4o (SD=7.15) and the mean distance from TAL noted was 4.2 mm (SD=2.73). 85.7% of the cups were within the safe zone target of 300 to 500. There was a significant positive correlation between the cup depth and inclination angle (r=0.93, p