Pelvic Positioning and Acetabular Orientation in Total Hip Replacement

  • Megan Rutherford

Student thesis: Doctoral ThesisDoctor of Philosophy


Mal-orientation of the acetabular component can induce negative outcomes such as dislocation and subsequently a loss of patient satisfaction. Currently, a wide range of acetabular component orientations are observed on post-operative radiographs, despite the use of fixed intra-operative target angles. This work sought to answer the question of how pelvic orientation affects acetabular cup orientation in current practice and whether it can be accounted for without the use of expensive tools or additional radiation exposure.

To assess the influence of post-operative pelvic positioning relative to the radiographic film, a new computational tool was developed that allowed three-dimensional reconstruction of the pelvis and acetabular component from a single two-dimensional radiograph. Use of this tool enabled true measures of acetabular orientation to be determined (relative to the pelvis as compared to the radiographic reference frame which is subject to magnification errors). True measures of acetabular orientation exhibited reduced variability when compared to conventional 2D measures of radiographic acetabular orientation; inclination variability was reduced by 22% when applied to a clinical cohort.

Pelvic external / internal rotation (about the longitudinal axis) was found to be the primary mode of intra-operative pelvic mal-rotation that contributed to differences between operative and true post-opertative measures of acetabular orientation. In practice this may be reduced by using a new coronal alignment guide developed as part of this research (mean error, 0.60° ± 0.68°). To account for intra-operative pelvic mal-rotation, when using the TAL approach, in the absence of any other intervention, orthopaedic surgeons should aim for an operative inclination that is 9° less than their true post-operative target.

The tools developed within this research have the potential to be adapted into surgical practice for total hip replacement. If implemented, they could help reduce inclination variability, increase survivorship, and improve patient satisfaction.
Date of Award2019
Original languageEnglish
Awarding Institution
  • Queen's University Belfast
SupervisorAlex Lennon (Supervisor), Nicholas Dunne (Supervisor), David Beverland (Supervisor) & Janet Hill (Supervisor)

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