The Tribology of Explanted Hip Resurfacings Following Early Fracture of the Femur.
A recognized issue related to metal-on-metal hip resurfacings is early fracture of the femur. Most theories regarding the cause of fracture relate to clinical factors but an engineering analysis of failed hip resurfacings has not previously been reported. The objective of this work was to determine the wear volumes and surface roughness values of a cohort of retrieved hip resurfacings which were removed due to early femoral fracture, infection and avascular necrosis (AVN). Nine resurfacing femoral heads were obtained following early fracture of the femur, a further five were retrieved due to infection and AVN. All fourteen were measured for volumetric wear using a co-ordinate measuring machine. Wear rates were then calculated and regions of the articulating surface were divided into "worn" and "unworn". Roughness values in these regions were measured using a non-contacting profilometer. The mean time to fracture was 3.7 months compared with 44.4 months for retrieval due to infection and AVN. Average wear rates in the early fracture heads were 64 times greater than those in the infection and AVN retrievals. Given the high wear rates of the early fracture components, such wear may be linked to an increased risk of femoral neck fracture.
Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA 24061, USA. jklord@vt.edu.
James K
JK
Lord
North Tees Explant Centre (NTEC), Farndale House, University Hospital of North Tees, England TS19 8PE, UK. djlangton22@doctors.org.uk.
David J
DJ
Langton
Joint Replacement Unit, University Hospital of North Tees, England TS19 8PE, UK. Antoni.Nargol@nth.nhs.uk.
Antoni V F
AV
Nargol
Department of Orthopaedics & Trauma, Queen Elizabeth University Hospital, Glasgow G51 4TF, UK. rmdmeek@doctors.org.uk.
R M Dominic
RM
Meek
School of Mechanical and Systems Engineering, Newcastle University, England NE1 7RU, UK. Thomas.joyce@ncl.ac.uk.
Thomas J
TJ
Joyce
cobalt chromium; hip prosthesis; hip resurfacing; metal-on-metal; roughness; wear