OXINIUM™ Oxidized Zirconiumand counterface review™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
Outline• Bearings choices for hard on soft articulation• OXINIUM™ Oxidized Zirconium• OXINIUM knee – laboratory studies• OXINIUM knee – clinical studies• OXINIUM hip – laboratory studies• OXINIUM hip – clinical studies™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
Desired attributes of hard bearingsin hard on soft articulationBulk material attributes Bearing surface attributes• Biocompatible to reduce PE wear• Corrosion resistant • Low friction and wettable• Suitability for metal sensitive patients • Scratch or abrasion resistant to third body debris such as bone cement• Chemically and mechanically stable over extended period of time • Macro-damage resistance (instrument damage, chipping, taper damage-compatibility, fracture risk, etc)
Choices of hard bearing materials• CoCr alloy (as-cast, forged or wrought)• Surface hardened CoCr• Surface hardened Ti6Al4V alloy (wrought or forged)• Ceramic coatings• Monolithic ceramic such as yttria stabilized zirconia, alumina (Forte), zirconia toughened alumina (Delta)• OXINIUM™ Oxidized Zirconium™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
CoCr Alloy• Long clinical history• Does contain Nickel which is known to cause allergic Allergic response Ni content for Ti and CoCr to a CoCr knee femoral response in some patients (Nasser et al., AAOS 2007) is permissible content per ASTM, actual content• Less scratch resistant to bone may be less, Internal cement debris compared to some Specification of Ni for Zr2.5Nb <0.0035% of the advanced bearing materials Scratches on retrieved CoCr due to bone cement debris
Ion treated CoCr• Increase surface hardness of CoCr to improve wettability and abrasion resistance• Sold by Stryker under trade name “LFIT” (Low Friction Ion Treated)• Small depth of hardening (~0.2 micron)• Retrieval analysis has shown that ion treated layer can disappear over time**McGrory et.al., AAOS 2005
Ti6Al4V alloy• Not a favored material for bearing application• Promoted as an alternate to CoCr for metal sensitive patients by some companies• Nitrogen diffusion hardened Ti6Al4V sold by Zimmer• Depth of hardening is small and hardened layer will eventually wear Scratching of nitrogen ion implanted through and scratch the femoral Ti6Al4V during knee simulator test (Shetty et.al., ASTM- STP, 1272,1996) leading to increased wear of polyethylene
Ceramic coatings• Ceramic coating to improve hardness and abrasion resistance• Coating adhesion critical to the performance, third body debris can Endotec TiN Aesculap ZrN wear the coating, coating debris can coating on Ti6Al4V coated CoCr scratch CoCr and will increase wear of polyethylene Coating delamination TiNbN ZrNWear through of the coating during bone cement abrasion test TiNbN coating* – Vanguard-Biomet(Hunter et al., MPMD, 2004) *Haider et. Al. Trans. 54th ORS, poster 2007, 2008
Monolithic ceramics• Yttria stabilized zirconia, Alumina and zirconia toughened alumina (ZTA or Delta) are preferred materials of choice Yttira stabilized Biolox Delta-CeramTec AG zirconia ceramic• Difficult to put porous structure for JMM, Japan non-cemented use in knee femoral !"90 ß=#=90 a!c• Ceramic knees not cleared in US #• Finite fracture risk 5% Volume increase c• Phase transformation leading to roughening or fracture pose long ß term concern on stability a ! Tetragonal Monoclinic Metastable phase of zirconium Stable phase of zirconium dioxide in ytrria stabilized oxide in the oxide of zirconia and Delta OXINIUM™ Oxidized Zirconium™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
OXINIUM™ Oxidized Zirconium• Base alloy of the OXINIUM material is zirconium-2.5 wt% niobium (Zr-2.5Nb)• Oxidized to form a hard ceramic surface• Zirconium is one of the five most biocompatible elements (titanium, zirconium, niobium, tantalum and platinum)• Ni content of Zr2.5Nb alloys is extremely low making it suitable for metal sensitive patients• Other uses of Zirconium alloys – Chemical industries (valves and seals) – Nuclear fuel rods™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
OXINIUM™ Oxidized Zirconium• Wrought zirconium-2.5 niobium device is heated in air• Surface transforms to stable ceramic (~5 !m), not a coating• The OXINIUM alloy is durable with toughness of metal and high strength Air Oxygen 500oC Diffusion Original Surface Oxygen Enriched Metal Ceramic Oxide Oxygen Enriched Metal Metal Substrate *Hunter et al., J ASTM Intl 2005™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
HardnessHardness of Oxide of OXINIUM™ devices is twice that of CoCr*Long et al., SFB 1998™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
Oxide integrityAdhesion and cohesion of the oxide excellent• “Brick-like” structure perpendicular to surface• No pores or segregation internally or at interface TEM Image* Rectangular Ceramic Monoclinic Oxide Crystals of Zirconia Zr2.5Nb *Hobbs et al., J Appl Ceram Tech 2005
Strength• Supports 4.4 kN (~1000 lbf) for 10 million cycles – equivalent to CoCr• Bends with 19.8 kN (~4500 lbf) – does not break or delaminate Tsai et al., SFB 2001
Abrasion resistance4,900 times less volumetric wear in bone cement abrasion testcompared to CoCr, Ceramic coated disks show wear through OXINIUM CoCr TiNbN ZrNWear through of the coating during bone cement abrasion test(Hunter et al., MPMD, 2004) Hunter and Long, WBC 2000™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
Damage toleranceResists oxide removal even if damaged• 10 Mcycle bone cement abrasion test across a groove milled through the oxide* Milled Pin Motion Groove Oxide Surface Metal Substrate *Hunter, SFB 2001*Hunter, SFB 2001
Coefficient of friction• Lower coefficient of friction against polyethylene and against cartilage ™• Lower coefficient of friction means less adhesive wear of polyethylene Poggie et al., ASTM STP 1145™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
Interfacial friction and heat generation*• Lower friction leads to lower interfacial temperature• Thermal conductivity (heat dissipation also critical)• OXINIUM™-ceramic surface provides lower friction and bulk metal 45 provides higher thermal conductivity 40 HEAD LINER Alumina Temperature Difference (degC) OxZr• Alumina and OXINIUM heads 35 CoCr 30 generated less heat compared to 25 Zirconia yttria stabilized zirconia. 20 15 10 5 0 1.0Hz 0.5 Hz 1.0Hz 0.5 Hz*Tsai et al., Key Eng. Matls. 2006 Test Frequency Test Frequency™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
Wettability• A drop of fluid beads up more on a CoCr surface• A drop of fluid lies down more on a ceramic surface Drop of fluid on a CoCr surface• The ceramic surface of Oxidized Zirconium slides better than Cobalt Chrome because it lubricates better Drop of fluid on a ceramic surface
Chemical and mechanical stability• Chemically stable after 20 hrs of steam autoclave (~simulated ageing of >80 years in-vivo)*• Does not shatter in crush test with 89 kN (20,000 lbf) load – Flattens slightly with 89 kN side load without stem – Oxide maintains integrity on slightly flattened head Zirconia OXINIUM™ head*Sprague et al., ISTATop load 2003 Side load*Sprague et al., ISTA 2003™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
OXINIUM™ Oxidized Zirconium – key messages• Ceramic bearing surface without a risk of fracture• Surface transformation, not a coating• Suitable for metal sensitive patients• Highly wettable, abrasion resistant and low friction ceramic surface• Long term mechanical and chemical stability• Like other surfaces can get damaged intraoperatively, care needs to be exercised with all the bearing surfaces™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
OXINIUM™ knee – laboratory studies™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
Knee simulator test (benign)OXINIUM™ femorals reduced conventional PE wear rate by 85%Spector et al., JBJS, 2001™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
Independent Wear Study: Scripps Institute• Testing done at Independent Lab (Scripps Institute in San Diego)• 42% wear reduction – benign conditions*• 40–60% wear reduction – high rotation & high varus** 40 CoCr Wear Rate (mm3 / Mcycle) 35 OxZirc 30 25 20 15 10 5 0 Benign HiRot HiVarus*Ezzet et.al., CORR 2004, ** Ezzet et.al., Trans. ORS, 2005
VERILAST™ Technology:OXINIUM™ Knee Femoral and 7.5 XLPE*VERILAST Technology provides the lowest wear™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
OXINIUM™ knee – clinical studies™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
OXINIUM™ knee and hip implantationsAs of 2009, over 200,000 knee femoralsand 100,000 femoral heads implanted• First total knee in December 1997• First total hip in October 2002™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
Clinical study knees – 5 year clinical results• First Study 72 Patients with OXINIUM™ knees OXINIUM CoCrMo mean follow-up 5.6 years, safety study• Second study (randomized) Mean flex 119º 116º compare CoCr and OXINIUM knees Knee (38 patients) 91 92 score• No specific complications Function associated with OXINIUM knees 76 72 score Laskin, Tech. Knee Surgery 6(4), 220-226,2007™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
Clinical study knees >5 year clinical results• 98 Patients, minimum follow-up 5 years, Implanted between April 2001 to December 2003• 98.7% survival rate at 7 years (95% CI , 90.3%–99.8%)• Worst case scenario of patients losing follow-up, gives 94.5% survivorship at 7 years **Innocenti et al.,CORR, DOI 10.1007/s11999-009-1109-y, 2009
In-vivo temperature measurements*Increase in temperature in the joint space for healthy knee,arthritic knee, different designs and OXINIUM™ kneefemoral components was measured OXINIUM knee*Pritchett, CORR, 442,2006,195-198™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
Metal sensitivity case study*• 56 year old homemaker, cannot wear jewelry• Left Knee: 3 years post TKA (CoCr) – Pain & stiffness – Persistent rash• Revised to Alumina – Rash went away• Right knee primary with OXINIUM™ material: Rash did not appear*Nasser et al., AAOS 2007™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
Retrieval analysis* 90 80• Matched pair analysis of OXINIUM™ 70 Tibial Insert Wear Score 60 Oxidized Zirconium and CoCr knee 50 femorals and tibial inserts 40 30• In-vivo time similar 20 10• Wear score of inserts and of femoral 0 Inserts/CoCr Inserts/OXINIUM components graded 12• Lower wear score of OXINIUM femorals and corresponding inserts Femoral Damage Wear Score 10 8 6 4 2 0 CoCr OXINIUM*Heyse et al., ESSKA, 2010, Oslo, Norway™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
Retrieval analysis• 9 OXINIUM™ and 9 CoCr knee femoral components*• In-vivo time – OXINIUM (1.2 to 5.6 yrs) – CoCr (0.7 to 4.6 yrs)• Articulating surface roughness measurements• CoCr components rougher than OXINIUM knee femorals*Sebastian et al., Trans. 54th ORS, 2008™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
OXINIUM™ hip – laboratory studies™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
Hip simulator wear test with abraded heads 20• CoCr and OXINIUM™ heads Wear Rate (mm3/Mcycle) Against OXINIUM heads roughened to simulate presence Against CoCr heads of third body debris in the joint 10• Tumbled OXINIUM head has same wear rate as new CoCr head 0 Smooth RoughGood et al., JBJS 2003™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
Hip simulator wear test (jogging protocol) 30 HL001123 Verse CoCr Head 25 Against CoCr heads HL001125 Verse CoCr Head HL001127 Verse CoCr Head HL001122 Verse Oxinium Head HL001124 Verse Oxinium Head heads Against OXINIUM 20 HL001126 Verse Oxinium Head Cumulative Wear (mm3) 15 10 5 0 0 1 2 3 4 5 6 7 8 -5 Cycles (millions) -10Parikh et al., Trans. 55th ORS, 2340, 2009™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
CoCr/CPE, OXINIUM™/XLPE and Delta/XLPE under jogging protocol 60 50Wear Rate mm3/Mcycle 40 30 ~95% 20 10 0 32mm CoCr/CPE 36mm Delta/XLPE 36mm Ox/XLPE 32 mm CoCr/CPE: Parikh et al., ORS 2009, 36 mm Delta/XLPE and Ox/XLPE –Data on file ™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
Large heads against XLPE• Large heads offer more joint 4.5 stability and range of motion 4• Wear of 44mm OXINIUM™/XLPE 3.5 Cumulative Wear (mm 3) is less than 36mm CoCr/XLPE 3 (p<0.05)* 2.5 2 1.5 1 0.5 0 Against 36mm CoCr heads Against 44mm OXINIUM headsParikh et al., ISTA 2010™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
OXINIUM™ hips – clinical studies™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
Linear wear• RSA study in Australia: – 30 patients with 32mm OXINIUM™/XLPE (10Mrad) – 28mm CoCr/XLPE (5 and 10 Mrad) – 28mm CoCr/ETO sterilized UHMWPE• OXINIUM/XLPE-10 shows promising results Li et al., Trans. 52nd ORS, 0643,2006™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
Linear wear• 2 year follow-up, – CoCr/XLPE – OXINIUM™/CPE – OXINIUM/XLPE• 270 patients prospectively randomized consecutive, all heads 32 mm• Reviewers blinded CoCr/XLPE Ox/CPE Ox/XLPE• OXINIUM/XLPE shows lowest wearHaddad et.al., Proc. AAOS, P067, 2010™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
Clinical Outcome*• Randomized study – 50 patients received OXINIUM™ femoral heads – 50 patients received CoCr femoral heads• Minimum follow-up 2 years• Authors conclude use of OXINIUM heads is safe and effective*Lewis et.al., ISTA 2009™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.
Retrieval analysis: phase stability Raman spectra**• Comparison of OXINIUM™, yttria stabilized zirconia (YTZ) and Delta (contains yttria stabilized zirconia~17 volume %)*,**• Monoclinic content and surface roughness measured• Both YTZ and Delta showed phase transformation,• OXINIUM is stable monoclinic Tetragonal peak absent for OXINIUM so no phase transformation observed *Medel et al., Trans. 55th ORS,2300, 2009 **Sakona et al., Trans. 56th ORS, 2358A, 2010™Trademark of Smith & Nephew. Reg. US Pat. & TM Off.