Paris 2003 Wear of UHMWPE cup and component loosening in total hip arthroplasty Professor B.M. Wroblewski P.D. Siney P.A. Fleming The John Charnley Research Institute Wrightington Hospital, U.K. Mechanical v Biological A scientific controversy ?

Paris 2003 “The late failure if it does eventually supervene, is to be expected from one, or both, of two possible causes – 1. Tissue reaction to particles abraded from the bearing surfaces 2. Mechanical loosening of the cement bond in the bone.” Sir John Charnley 1967

Paris 2003 Cup Wear & Migration

Paris 2003 “… socket wear... and the resultant cup loosening … appears to be the one factor limiting the life of the arthroplasty.” BM Wroblewski 1985

Paris 2003 Removal or transfer of material from articulating surfaces due to their relative movement under load. British Standards Institution 1979 Wear :

Paris 2003 Wear measurement : - Change of mass - Volume measurement - Depth of wear tracks (penetration : depth and rate) British Standards Institution 1979

Paris 2003 Continuous deformation of a material when subjected to stress over an extended period. Change of dimensions without loss of material Creep :

Paris 2003

“… granulomatous tissue may act on the neighbouring bone … which is removed by extensive resorption leading to loosening of the prosthesis.” Willert & Semlitsch Biocompatibility of Implant Material 1976

Paris 2003 “… the chief clinical question is that of biological effects of the debris and not the mechanical problems due to dimensional changes.” RM Rose et al JBJS 1980

Paris 2003 “… only 10% of volumetric changes are caused by wear, whereas creep is responsible for the other 90%” RM Rose et al JBJS 1980

Paris 2003 “ Cement disease” “ Cementless disease” “Particle disease” “Access disease” – “Effective joint space”

Paris 2003 Wear Volume – ‘Cylindrical’ Volume   r 2 x d

Paris 2003 Mechanical v Biological causes of component loosening in total hip arthroplasty. A scientific controversy ?

Paris 2003 The study of those judgements concerning which universal agreement can be achieved Science Campbell 1921

Paris 2003 A publicly and persistently maintained dispute Controversy Campbell 1921

Paris 2003 Scientific controversy does not concern the facts : - component loosening - It concerns explanation of the facts : - the cause of component loosening -

Paris 2003 Scientific controversy rests on the assessment of the reason for action

Paris 2003 NOT : is there tissue reaction to wear particles BUT : is tissue reaction to wear particles responsible for component loosening ?

Paris Loss of interest - Force - Consensus : does not resolve the basic issue - Negotiation : common in politics - Sound argument closure Resolution of Controversy

Paris correct position is reached - in the context of the controversy - making the opposing view unjustified Sound argument closure

Paris 2003 Essential to promote progress Controversy

Paris 2003 Three aspects - The facts - The explanation of the facts - Proposed solutions Controversy

Paris 2003 Component loosening : not disputed but - Incidence Interpretation of radiographic appearances Clinical presentation Indications, timing and method of revision may be open to debate and dispute Controversy : The Facts

Paris 2003 Mechanical or Biological ? The main aspect of the controversy as it dictates the line of action Controversy : The explanation of the facts

Paris Tissue reaction to wear particles - Bone resorption - Component loosening Solution - Modify tissue reaction - Change the materials Biological

Paris Outer cup wear : B.M. Wroblewski JBJS Head damage : increased frictional resistance R.M. Hall et al B.J. Rh Thinning of plastic cup shell : fatigue type process R.M. Hall et al Ibid - Increased frictional torque : Cup size 30 < 40 < 43 - Impingement B.M. Wroblewski JBJS 1985 Mechanical :

Paris Theoretical consideration B.M. Wroblewski Practical results (1982 : 10mm diameter neck) mm : impingement at 0 wear 10.0 mm : at 2 mm wear Mechanical : reduced diameter neck (12.5mm 10mm) } 50% probability R.M. Hall et al J. Orth. Sc. 1998

Paris 2003 Acetabular Pressurizer and revision for aseptic cup loosening Survivorship Analysis

Paris 2003 Distal closure of the medullary canal with cancellous bone block and revision for aseptic stem loosening Survivorship Analysis

Paris year results : 0.2 – 0.41 mm total penetration Mechanical : Alumina Ceramic / XLPE

Paris cases : 80.4% no measurable wear Mechanical : Zirconia Ceramic / UHMWPE Rate of penetration (mm/yr)

Paris Tuberculosis - OA cysts - Wear without cavitation - Healing of Teflon granuloma Clinical observations

Paris 2003 Intrapelvic teflon granuloma Orthopaedics International, 1995

Paris Low Wear = penetration  0.02 mm/year - High Wear = penetration  0.2 mm/year Low Wear v High Wear

Paris 2003 Low Wear v High Wear Low WearHigh Wear Number of cases Average age41 years40 years Average follow-up15.6 years13.1 years Cup revision 5.3%40.0% Stem revision 5.3%7.4%

Paris 2003 Low Wear v High Wear and revision for aseptic CUP loosening Survivorship Analysis

Paris 2003 Low Wear v High Wear and revision for aseptic STEM loosening Survivorship Analysis

Paris Fix components well - Reduce wear (Ceramic v UHMWPE) - Avoid strain shielding Conclusions

Paris 2003

What is revealed is interesting What is concealed is vital When it comes to WEAR

Paris 2003 “To know is science. To believe one knows is ignorance” Hippocrates 460 – 400 BC