R3 Design Rationale 00438V1
2015-04-30
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We would like to thank the following surgeons for their participation as part of the R3™ Acetabular System design team: Robert Barrack, MD St. Louis, Missouri Robert Bourne, MD London Health Sciences Center London, Ontario, Canada Jonathan Garino, MD University of Pennsylvania School of Medicine Philadelphia, Pennsylvania Wayne M. Goldstein, MD Clinical Professor of Orthopaedics University of Illinois at Chicago Illinois Bone and Joint Institute Chicago, Illinois Richard Kyle, MD Minneapolis, Minnesota Stephen J. McMahon MB BS, FRACS(Orth), FA(Orth)A Senior Lecturer Monash University Malabar Orthopaedic Clinic Melbourne, Australia John L. Masonis, MD OrthoCarolina Hip & Knee Center Charlotte, North Carolina Henrik Malchau, MD Associate Professor Harvard Medical School Codirector The Harris Orthopaedic Biomechanics and Biomaterials Laboratory Massachusetts General Hospital Boston, Massachusetts Michael Ries, MD University of California San Francisco, California Cecil Rorabeck, MD Professor of Orthopaedic Surgery University of Western Ontario London, Ontario, Canada Van Paul Stamos, MD Illinois Bone and Joint Institute Glenview, Illinois Clinical Instructor of Orthopaedic Surgery Northwestern University Medical School Chicago, Illinois Contents Introduction ..............................................2 Advanced bearing capabilities VERILAST™ Technology Oxidized Zirconium on XLPE .........................................................3 Ceramic-on-ceramic......................................6 Stability Larger head sizes ........................................ 10 Locking mechanism .....................................12 STIKTITE™ Porous Coating ............................ 14 Instrumentation.................................... 16 1 R3volution in motion The R3™ Acetabular System combined with the Smith & Nephew portfolio of hip stems provides an advanced hip replacement system with: • Wide range of advanced bearing options • Excellent primary stability • Flexible instrumentation General features NO HOLE, THREE HOLE, and MULTI HOLE hemispherical shell offering STIKTITE™ Porous Coating for enhanced scratch-fit feel and enhanced initial fixation 2 Polished inner surface to minimize backside wear R3™ Liner options XLPE Offered in 0 and 20 degree, 0 and 20 degree +4mm lateralized, and constrained options Ceramic-on-ceramic offered in BIOLOX® Forte 3 Advanced bearing surfaces: VERILAST™ Technology Oxidized Zirconium with XLPE R3™ system with VERILAST Technology is an advanced bearing option VERILAST™ Technology for hips from Smith & Nephew uses the exclusive bearing combination of proprietary OXINIUM™ and highly cross-linked polyethylene, which provides superior clinical survivorship and biocompatibility without sacrificing versatility or introducing the risk of ceramic-like fracture.1 Most importantly, VERILAST Technology provides low wear, corrosion avoidance and real-life results.OXINIUM material along with 10 Mrad XLPE provides the wear performance of hard bearings along with the intraoperative options of hard-on-soft bearings. Wear performance VERILAST Technology for total hip arthroplasty has been tested and shown to provide superior wear performance compared to CoCr on highly crosslinked polyethelene, for up to 45 million cycles.2 With advanced materials designed to last, VERILAST Technology helps restore patients to their active lifestyles, allowing joint pain to be addressed earlier. Cumulative volumetric wear comparison 2 700 CoCr (32mm) against CPE 600 500 CoCr (36mm) against 10-XLPE 400 80% 300 Real life results Oxidized Zirconium has a clinical history of more than 10 years. Over 190,000 components have been implanted successfully to date. Impressive clinical wear performance of OXINIUM heads has been reported in global registry data. In the 2013 Australian Registry, the ceramicized metal/cross-linked polyethylene category, which includes the exclusive OXINIUM alloy from Smith & Nephew, had the highest survivorship of all bearing categories at five years: 98.0%.1 4 Reduction in volumetric wear after 7.8 million cycles 67% Reduction in volumetric wear after 45 million cycles 200 100 OxZr (36mm) against 10-XLPE 0 0 10 20 30 40 50 Biocompatibility Protect against taper corrosion There is a growing concern in the orthopaedic community about fretting and corrosion at the head neck taper junction.With its biocompatible properties, due to its use of Oxidized Zirconium, VERILAST Technology has shown to reduce taper corrosion in total hip arthroplasty, minimizing the concern of trunnionosis. A study by Pawar et al. used an acidic fretting test to compare the potential corrosive and fretting responses of OXINIUM™ (OxZr), cobalt chrome (CoCr) and stainless steel (StSt) femoral heads. As the study states, “The OxZr heads coupled with Ti-6Al-4V and SS trunnions showed the least chemical attack on either the head or the trunnion.” 3 Not your average cross-linked poly The Smith & Nephew 10 Mrad, fully annealed XLPE is the only crosslinked polyethylene proven to produce less volume of wear debris particles in all size ranges.4,5 Less wear debris provides a reduced chance for osteolysis. All currently marketed crosslinked poly indicates a significant improvement in the volume of wear debris, which would lead one to assume all crosslinked poly is the same. However, Smith & Nephew investigated more closely and found that not all crosslinked poly minimizes the amount of particles generated. Because the wear particles of crosslinked poly can be smaller in size than with UHMWPE, it is possible to reduce the volume but actually increase the number of particles.4,5 The Smith & Nephew crosslinked polyethylene significantly reduces the number of particles generated. The gravimetric wear rate of R3 XLPE is not measurable in a hip simulator, but the number of particles generated is reduced by 80% compared to traditional CoCr on conventional poly bearing.6 CoCr Ti64 StSt OxZr Ti64 OxZr StSt StSt Image from Pawar et al., ASMI 2004. High magnification images of captured particles Standard unirradiated polyethylene 5 Mrad irradiated crosslinked poly, showing an increase in the number of particles in conjunction with a decrease in average size 10 Mrad irradiated R3™ XLPE showing a reduction in total number of particles 5 Advanced bearing surfaces: ceramic-on-ceramic R3™ ceramic-on-ceramic bearing couple Due to the reduced grain size, ceramic components are harder than before. That has led to wear rates as low as 0.001mm/year.7,8 Ceramic-on-ceramic bearing surfaces have been used worldwide in total hip replacement for more than 30 years. Renewed interest in ceramics as an alternate bearing surface has been driven by the following: • New technology • Improved manufacturing processes and standards • New designs This translates into improvements in the following: • Mechanical and physical properties • Wear characteristics • Optimized biocompatibility • Reliability expected by today’s more active patients Neck impingement In ceramic bearing systems, increases wear and decreases implant longevity.9 The flush-seating liners of the R3 ceramic acetabular system in combination with Smith and Nephew femoral stem neck geometry: • Increases the range of motion and consequently, may reduce the likelihood of impingement.9 • Mitigates the risks of metal transfer and increased friction imposed by designs with a raised rim.10 The R3 system’s ceramic design is an assembled combination of: • A ceramic component made from orthopaedic industry standard material, BIOLOX® Forte • A precision-machined support ring made of a Titanium alloy (Ti-6Al-4V) that is commonly used in orthopaedic implants. Titanium support ring for added strength The unique feature about R3 ceramic liners is that they come with a titanium support ring around the periphery of the liner. The support ring and ceramic liner are precisely assembled utilizing a cold pressing process, which assures that the material properties of the ceramic and titanium are not altered. The support ring offers greater protection against chipped edges. 66 Stability: head/shell ratios Optimized head/shell ratios Use of larger diameter femoral heads has been clinically reported to decrease the probability of dislocation in patients.11-14 • Large heads increase the ROM of the joint11-13 • Large heads reduce the incidence of neck impingement with soft tissue or the edge of the shell14 7 Stability: head/shell ratios continued With the R3™ Acetabular System, surgeons have the option of using larger head sizes in smaller acetabular shells: R3 OXINIUM™ alloy on XLPE acetabular system: 36mm head in a 52mm cup size XLPE Cups 22 28 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 8 32 36 40 44 Ceramic 28 32 36 Stability: locking mechanism R3™ locking mechanism for secure liner stability R3 locking mechanism design features: • Locking taper that supports ceramic liners • Double-channel lock design that provides axial stability for poly liners • 12 large anti-rotational tabs on the poly liner that provide rotational stability Anti-rotation tabs Constrained liner locking mechanism Hard-bearing taper locking mechanism XLPE locking mechanism Intraoperative adjustments to the liner position may be performed with true confidence. Independent researchers confirm that in some competitive locking designs, the liner can be significantly damaged by extraction, which prohibits liner repositioning.15 Laboratory tests of the R3 locking mechanism have shown it withstands consecutive insertions of the same liner without damaging its locking integrity.16 9 Stability: locking mechanism continued Push-out and torque-to-failure tests of the R3™ locking mechanism demonstrate that it offers the benefit of a secure and stable liner. The R3 lock can withstand over 1112N of push-out force in any of its liner options and over 40 N-m of torque. 1400 REFLECTION™ R3 1200 Push-out Load (N) 17 1000 800 600 400 200 0 45 REFLECTION R3 40 Torque-to-failure (N-m) 35 30 25 20 15 10 5 0 10 Maximum predicted in-vivo torque = 2.4 N-m 18 Stability: STIKTITE™ Porous Coating Enhanced stability and fixation with STIKTITE Porous Coating Utilizing STIKTITE coating on the R3™ Acetabular Shells allows for a true scratch-fit feel during the shell seating and a clinically proven in-growth surface for long-term implant success.19 11 Stability: STIKTITE™ Porous Coating continued STIKTITE Porous Coating demonstrated a higher coefficient of friction compared to porous tantalum when tested by the same method.20 The mean coefficient of friction for STIKTITE coating was higher than that of porous tantalum against both cancellous and cortical bone. These results indicate that STIKTITE coating should have superior friction, scratch-fit feel and initial fixation stability as compared to porous tantalum. Frictional coefficients of bone ingrowth structures against cancellous and cortical bone (n=96 to 100)20 1.5 Cancellous bone Cortical bone Frictional coefficient 1.2 0.9 0.6 0.3 0.0 STIKTITE coating Porous tantalum, net-shaped Porous tantalum, EDM-shaped STIKTITE coating is a sintered three-dimensional asymmetric titanium powder that has a porosity of about 60%. Increased porosity allows for potentially greater bone ingrowth, which can enhance long-term fixation and implant stability. STIKTITE coating provides enhanced initial mechanical stability, which is particularly important in damaged or less biologically active bone. The average pore size of STIKTITE coating (200 µm) is within the 100– to 500–µm range for optimal bone ingrowth. 12 Instrumentation Streamlined instrumentation improves surgical efficiency This seemingly simple technique is a very effective way of precisely placing the hard bearing liners inside the shell without the issue of improper seating due to misalignment as seen in other competitive systems.21-22 Cocking of a ceramic liner, in particular, during impaction can lead to a fracture of the liner. Preassembled alignment ring on all hard bearing liners. Alignment ring allows for easy placement of the hard bearing liner in the shell. The liner impactor can then be inserted through an opening in the alignment ring and the liner can be seated with an impaction force. Upon impaction the ring will disengage and remain on the liner impactor for later disposal. The hard bearing liner is now perfectly seated in the shell. 13 References 1 Australian Orthopaedic Association National Joint Replacement Registry Annual report. Adelaide: AOA; 2013. 2 Parikh, P. Hill, V. Pawar and J. Sprague, “Long-term simulator wear performance of an advanced bearing technology for THA,” Orthop Res Soc, San Antonio, TX, Jan 26-29, 2013, 1028. 3 Pawar V, Jones B, Sprague J, Salehi A, Hunter G. Acidic Fretting Tests of Oxidized Zr-2.5Nb, CoCr, and SS Femoral Heads, ASMI, 2004. 4 Scott M, Morrison, Mishra SR, Jani S. A method to quantify wear particle volume using atomic force microscopy. ORS Transaction. 2002:27:132. 5 Ries MD, Scott ML. Relationship between gravimetric wear and particle generation in hip simulators: conventional versus crosslinked polyethylene. Scientific exhibit at American Academy of Orthopaedic Surgeons; Feb 27-March4, 2001; San Francisco, CA. 6 Good V, Widding K, Heuer D, Hunter G. Reduced wear using the ceramic surface on oxidized zirconium heads. InL Lazennec JY, Dietrich M, eds. Bioceramics in Joint Arthroplasty. Darmstadt, Germany; Steinkopff; 2004:93-98. 7 Biolox-ceramics for hip arthroplasty. CeramTec AG, MT 060003: GB.5.000-0612. Germany. 8 CeramTec Technical Monograph. Current perspective on the use of ceramics in total hip arthroplasty. CeramTec AG, 060003: GB.5.000-0612, 2007. 9 Elkins JM, O’Brien MK, Stroud NJ, Pedersen DR, Callaghan JJ, Brown TD. Hard-on-Hard Total Hip Impingement Causes Extreme Contact Stress Concentrations. Clin Orthop Relat Res (2011) 469:454–463; 16 October 2010. 10 Knahr K. Total Hip Arthroplasty, Tribological Considerations and Clinical Consequences. Orthopaedic Hospital Vienna-Speising, Vienna, Austria, 2013. 11 Berry DJ, von Knoch M, Schleck CD, Harmesen WS. Effect of femoral head diameter and operative approach on risk of dislocation after primary total hip arthroplasty. J Bone Joint Surg AM. 2005 Nov;87(11):2456-2463. 12 Barrack RL, Butler RA, Laster DR, Andrews P. Stem design and dislocation after revision total hip arthroplasty: clinical results and computer modeling. J Arthroplasty. 2001 Dec;16(8 Suppl 1):8–12. 13 Barrack RL. Dislocation after total hip arthroplasty: implant design and orientation. J Am Acad Orthop Surg. 2003 Mar-Apr;11(2):89–99. 14 Barrack RL, Lavernia C, Ries M, Thornberry R, Tozakoglou E. Virtual reality computer animation of the effect of component position and design on stability after total hip arthroplasty. Orthop Clin North Am. 2001 Oct;32(4):569–577, vii. 15 Tradonsky S, Postak P, Frimson A, Greenwald A. Performance characteristics of two piece acetabular cups. Cleveland, OH: The Orthopaedic Research Laboratory, Mt. Sinai Medical Center. 1992. 16 Data on file. 17 Data on file. 18 FDA guidance document for testing acetabular cup prosthesis. US Food and Drug Administration. May 1995. 19 Bourne R. Randomized controlled trial to compare acetabular component fixation of two porous ingrowth surfaces using RSA analysis. London, Ontario, Canada: London Health Science Center. 2007. Internal report on file at Smith & Nephew, Memphis, TN. 20 Heiner AD, Brown TD. Frictional coefficients of a new bon ingrowth structure. Poster no. 1623 presented at: Orthopaedic Research Society Annual Meeting; Feb 11-14, 2007; San Diego, CA. 21 Padgett DE, Miller AN, Du EP, Bostrom MPG, Nestor BJ. Ceramic liner malseating in total hip arthroplasty. Poster P097 at American Academy of Orthopaedic Surgeons; Feb 14-18, 2007; San Diego, CA. 22 Langdon AJ, Pickard RJ, Hobbs CM, Clarke HJ, Dalton DJ, Grover ML. Incomplete seating of the liner with the Trident acetabular system: a cause for concern? J Bone Joint Surg Br. 2007 Mar;89(3):291-295. Smith & Nephew, Inc. 7135 Goodlett Farms Parkway Cordova, TN 38016 USA www.smith-nephew.com Telephone: 1-901-396-2121 Information: 1-800-821-5700 Orders and Inquiries: 1-800-238-7538 ™ Trademark of Smith & Nephew. Certain marks Reg. US Pat. & TM Off. All Trademarks acknowledged. ©2014 Smith & Nephew, Inc. All rights reserved. 00438 V1 04/14
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