Kwon, Young-MinMellon, S. J.Monk, P.Murray, D. W.Gill, H. S.2013-10-182012Kwon, Y-M., S. J. Mellon, P. Monk, D. W. Murray, and H. S. Gill. 2012. In vivo evaluation of edge-loading in metal-on-metal hip resurfacing patients with pseudotumours. Bone & Joint Research 1(4): 42-49.2046-3758http://nrs.harvard.edu/urn-3:HUL.InstRepos:11181170Objectives: Pseudotumours (abnormal peri-prosthetic soft-tissue reactions) following metal-on-metal hip resurfacing arthroplasty (MoMHRA) have been associated with elevated metal ion levels, suggesting that excessive wear may occur due to edge-loading of these MoM implants. This study aimed to quantify in vivo edge-loading in MoMHRA patients with and without pseudotumours during functional activities. Methods: The duration and magnitude of edge-loading in vivo was quantified during functional activities by combining the dynamic hip joint segment contact force calculated from the three-dimensional (3D) motion analysis system with the 3D reconstruction of orientation of the acetabular component and each patient’s specific hip joint centre, based on CT scans. Results: Edge-loading in the hips with pseudotumours occurred with a four-fold increase in duration and magnitude of force compared with the hips without pseudotumours (p = 0.02). Conclusions: The study provides the first in vivo evidence to support that edge-loading is an important mechanism that leads to localised excessive wear (edge-wear), with subsequent elevation of metal ion levels in MoMHRA patients with pseudotumours.en-USPseudotumoursEdge-LoadingIn Vivo EvaluationMetal-on-MetalHip ResurfacingMetal IonsEdge-loadingIn vivo evaluationMetal-on-metalHip resurfacingMetal ionsJournal Article2013-10-1810.1302/2046-3758.14.2000019