39 year old, 260 lb. park ranger. TKA in situ: 4 Years. First reported Metal-backed, non-modular PCA knee. 16% incidence. Modular metalbacked

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1 Designer (Royalty income) - DePuy A Johnson & Johnson Company Consultant on Knee Products for Smith & Nephew Orthopaedics General Research Funding Inova Health System and the U.S. Army Medical Research & Materiel Command and the Telemedicine & Advanced Technology Research Center. Investor - Alexandria Research Technology First reported-19 Metal-backed, non-modular PCA knee Engh, JBJS August 19 1% incidence Modular metalbacked tibial component Peters, JBJS 7A, year old, 0 lb. park ranger TKA in situ: 1

2 9 year old nun TKA in situ 3.5 years Osteolysis can occur even when there is minimal visible wear on the articular side of the polyethylene Backside wear does occur and may contribute to the debris that causes osteolysis the Articular surface or the Modular surface

3 Do modular interfaces move? What is the magnitude of motion? Do any locking mechanisms eliminate interface motion? Nine different implant designs Mechanical testing-instron Do locking mechanisms deteriorate with time in vivo? 3

4 Mount tray in acrylic Precondition: 37 water bath for weeks Clamp components in individual frames Measure motion before resistance is encountered All implants out of the box had a mean 90 microns of motion Wide variation within any implant type Wide range of motion for all implants Do locking mechanisms become looser in vivo? Do both snap-fit and tongue-ingroove become looser?

5 Motion Index(microns) Control P.M. REV Parks et al, CORR, 199 ISO recommended surface finish for articulating medical devices: 0.1µ Tibial trays are over 30 times rougher than acceptable standards!! 55 retrieved inserts- designs Removal of stamped markings and poly protrusions correlated with time in vivo to X wear rates in total hips Poly protrusions Removal of Stamped Markings none <.5mm >.5mm (Months) None Partial Complete protrusion Stamped markings Loss of backside markings Li et al, CORR, 00 5

6 1 retrievals (1 different designs) In situ: 51 months Moderate / severe: Pitting-55% Burnishing-% Protrusions-% Conditt et al, JBJS AMK implants In situ: 3-1 months (mean-91 months) Backside volumetric wear: 13 ± 95mm 3 / Yr. Conditt et al, JBJS MG post-mortem retrievals Wear Mean: months in vivo Concave deformation: 9% Screw hole impression: 100% Wear Laser profilometry-computer reconstructions Burnishing, pitting, & protrusions Conditt et al, JBJS 005 Surace et al, CORR 00 Fixed 9 Sigma PFC inserts Gamma in Barrier In situ: 3 months Mobile 3 LCS RP inserts Gas Plasma In situ: 9 months

7 AORI retrievals Fixed 9 Sigma PFC inserts Gamma in Barrier In situ: 3 months Mobile 3 LCS RP inserts Gas Plasma In situ: 9 months Wear Score 1 10 p=.01* p=.135 p=1.000 Mobile Fixed Pitting early for mobile bearing Similar pitting at > years 0 <1 Year >1- Time In Situ > Wear Score p=.000* p=.000* p=.000* <1 Year >1- > Time In Situ Mobile Topside Mobile Fixed Scratching not seen on fixed bearing inserts Wear Score p=.00* p=.010* <1 Year >1- > Time In Situ p=.79 Mobile Fixed Burnishing early for mobile bearing Similar burnishing at > years Backside Wear LCS Rotating Platform Tibial Tray Scratches go beyond the expected rotation of the knee suggesting 3 rd body debris wear Scratching on metal tray closely mimics scratching on inserts 7

8 Titanium 0 CoCr Polished Total Wear Score- Poly Insert Titanium Cobalt Chrome p=.00* (13) p=.115 (11) 31 Posterior Stabilized γ in Barrier PFC Inserts > years: 100% had deformation & burnishing Post contact may accelerate backside wear 0 (7) () (0) (7) <1 Year >1- > Time In Situ 1) Himont Compression molded less sensitive to oxidation ) Non-modular interface eliminates backside wear Backside wear is a significant source of wear debris with both mobile and fixed bearing modular implants Industry standards are needed to minimize tibial component micromotion This research was supported by funding received from the U.S. Army Medical Research & Materiel Command and the Telemedicine & Advanced Technology Research Center.