Ceramics in Orthopaedic and Neurosurgery B. Sonny Bal, MD MBA JD PhD University of Missouri-Columbia Amedica Corporation
Historic Concern: Wear
Bearing Failures of the Past
The Rationale for Alternatives Metal-PE 0.2-0.5 mm/year Ceramic-PE 0.1mm/year Ceramic-Ceramic 0.001/year 4000x reduction (in vitro, Clarke) 0.025mm/year (in vivo, Sedel)
BIOLOX forte Alumina-Alumina Simulator Wear Compared to the typical wear rates for 28mm UHMWPE cups these ceramic wear rates conservatively represented a reduction in wear debris of some 750 fold. Clarke IC et al, Hip simulator validation of alumina THR wear rates for run-in and steady-stae wear phases in Garino and Willmann, Thieme, 2002
Comparative Wear Rates Simulator tests: Less wear and less likelihood of third body wear for ceramic-on-ceramic than for any other wear combination Wear rates in mm/year: Metal-on-polyethylene = 0.2-0.5 Ceramic-on-crosslinked polyethylene = 0.01 Metal-on-metal = 0.02 Ceramic-on-ceramic = 0.005 Wang A et al, Role of ceramic components in the era of crosslinked polyethylene for THR in Zippel & Dietrich, Steinkopff, 2003
Alumina Ceramic THA in U.S. 1981: Mittelmeier hip approved for sale. 1989: Ceramic-on-polyethylene cleared for sale. 1990: Ceramic-on-ceramic classified as class III. 1996: Ceramic-on-ceramic IDE studies initiated. 2003: Ceramic-on-ceramic approved for sale by FDA in February.
Evolution of Design & Material 1970 s Poor implant technology Inferior grade ceramics 1980 s Catastrophic Failure Design flaws 1990 s Mature implant technology Improved ceramics
Past Experiences THE MITTELMEIER STORY 1973 Wear couple performed quite well if components were stable and with proper range of motion. Design of femoral and acetabular components did not encourage proper fixation.
Modern Implants & Ceramics ~1990 s
U.S. TRIALS: more than 5,000 patients 1996 Osteonics, Wright + 2000, 1250 1997 Encore + 800 1998 Smith & Nephew + 300 1999 Implex + 300 2000 Biomet + 200 2006: Murphy et al AAOS 2005: D Antonio et al 2007: Seminars Arthroplasty Sedel et al: 30-year success alumina-alumina
Concerns: Fracture Risk? ~1/25,000 Reason? U.S. IDE Technical Deviation Murphy et al 2006
Fracture origin? Taper Bore- Metal Junction Multiple Dislocation? Metal Discoloration
Oxinium? Wrought zirconium alloy component is heated in air Metal surface transforms to ceramic; not a coating Ceramic oxide is uniformly about 5 mm thick Oxygen Diffusion Air 500 o C Original Surface Ceramic Oxide Oxygen Enriched Metal Metal Substrate
Metal Staining of Alumina?
Recurrent Dislocations with Alumina Obvious implant/liner damage Metal debris and ceramic debris Femoral heads intact Heavy staining (Aldo Toni AAOS 2006)
Surface changes on SEM Interposed metal particles? Metal + Scratches? 5 m cycles in vitro (Bal, Li 2006)
Stripe Wear and Squeaking 47 yo female Dysplasia Revision at 43 months for psoas tendonitis Walter, Toni 28mm heads, Mechanism? Wear colored with a pencil
Evolution Continues ZTA Ceramics: Controlled phase Low fracture rate Clinical data New applications for ceramic materials will bring more substitution of ceramic for metal components.
Ceramic Countersurface in TKA Breakage? Oonishi, Akagi Alignment, Wear
2017 Concerns? Wear? ZTA- or CoCr on x-linked PE Hard-Hard bearings? Squeak Metal-Metal bearings? Recalled Implant breakage? Low risk Material Stability? Unknown Metal taper corrosion? Big concern Not solved by ZTA femoral heads
Bull et al (J Bio Tribo Corros 2017) Corrosion: Galvanic, Electrochemical, Mechanical ZTA is not impervious to damage Corrosion and the electrochemical effects of the surrounding environment and related damage have been observed within the taper of a ceramic head on a titanium alloy stem The oxidized titanium showed significantly higher hardness values therefore damaging the chemo-mechanically softened alumina material
Silicon Nitride for Biomedical Applications A Bioactive Non-Oxide Ceramic Strength, toughness, and reliability Wear and scratch resistant Phase stability Hydrophilicity Favorable imaging characteristics Bacteriostatic Osteoconductive Clinical Studies 23
Fracture Toughness of Medical Ceramics B. J. McEntire, et al. "Surface toughness of silicon nitride bioceramics: II, Comparison with commercial oxide materials." Journal of the Mechanical Behavior of Biomedical Materials, 54, (2016): 346-359. 24
Fracture Toughness Mechanisms Si 3 N 4 s improved toughness is solely mechanically activated. 25
Fracture Toughness Mechanisms ZTA s toughness is chemically-mechanically activated. 26
Silicon Nitride in the Spine 30,000 implants; 8 years 27
Requirements of Ideal Spine Fusion Device Biocompatible, Stable, Non-toxic Images well on CT, MRI, x-ray Osteoconductive: Porous Osteoinductive: Stem Cells Living Bone Resist Bacteria Eliminate need for bone grafts Custom implants 3D manufacture No increase in costs 28
Silicon nitride shows up easily on x-ray, MRI, and CT Properties of silicon nitride enable radiolucent imaging X-rays, MRI, and CT Able to see peri-implant tissues 29
Silicon nitride is Osteoconductive Only Porous Structural Ceramic Micro-CT ovine femur Ingrowth at 4 weeks 30
As-fired silicon nitride is nano-textured, plus favorable ph, hydrophilic, and ionic surface properties 66 12 N 2 - Anneal 9 2 R a = 336 nm R a = 296 nm 31
If the Goal is Bioactive Spine Interbody Device That changes the basic biology of bone healing Through favorable nanostructure, ph, wet, ions And resists bacterial adhesion inherently With no risk of subsidence (Suh et al 2017) With faster fusion up to 36 months (Ball 2017) All without added bone grafts (Arts et al 2017) And is 3-D printable (Rahaman 2016) And is cost-competitive with PEEK SILICON NITRIDE is the only answer 32
Supported by 40+ papers 33
Thank you for your attention. 34 34