The Effect of Acetabular Component Geometry on Revision for Instability or Loosening: A study of 427,385 Primary Hip Replacements from the National Joint Registry for England, Wales, Northern Ireland, the Isle of Man and the States of Guernsey

Abstract

Instability is a potential complication after total hip arthroplasty (THA), and alternative acetabular component designs feature an elevated rim to improve THA stability. It has been reported, however, that these elevated rim designs can increase the risk of prosthetic impingement that can conversely increase the risk of THA instability and may contribute to PE wear and loosening. The published literature remains unclear regarding the influence of acetabular component bearing surface geometry, and in particular the influence of uncemented lip size, on the risk or revision THA surgery for instability or for loosening. The aim of this study is to examine the influence of acetabular component geometry on the risk of revision THA for instability or for loosening, and how surgical approach and time from surgery can influence revision risk. An observational cohort analysis of 224,874 cemented and 202,511 uncemented acetabular components from the National Joint Registry for England, Wales, Northern Ireland, the Isle of Man and the States of Guernsey (NJR) dataset was performed, utilising covariate adjusted competing risks survival analyses. This Registry based study confirms a significantly higher risk of revision THA for instability and for loosening when a cemented hooded or offset reorientating acetabular component is used, compared to an LPW component, regardless of surgical approach. In uncemented acetabular components, a lower risk of revision for instability in posterior approach THAs with 10- or 15-degree lipped liners compared to neutral liners was found, but no significant difference between these lip sizes. A higher revision risk is seen with offset reorientating liners. The benefit of lipped geometries against revision for instability was not seen in lateral approach THAs. Uncemented liner geometry does not seem to influence the risk of revision for loosening. Further research is required to clarify the role of offset reorientating cups/ liners and whether certain situations benefit from their use; and if the observed influences of acetabular bearing surface geometry on revision for instability or for loosening persist into the long-term.

Date of Award	31 Dec 2021
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Terence O'Neill (Supervisor)