Ceramics in Orthopaedic and Neurosurgery. B. Sonny Bal, MD MBA JD PhD University of Missouri-Columbia Amedica Corporation

Transcription

1 Ceramics in Orthopaedic and Neurosurgery B. Sonny Bal, MD MBA JD PhD University of Missouri-Columbia Amedica Corporation

2 Historic Concern: Wear

3 Bearing Failures of the Past

4 The Rationale for Alternatives Metal-PE mm/year Ceramic-PE 0.1mm/year Ceramic-Ceramic 0.001/year 4000x reduction (in vitro, Clarke) 0.025mm/year (in vivo, Sedel)

5 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

6 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 = Ceramic-on-crosslinked polyethylene = 0.01 Metal-on-metal = 0.02 Ceramic-on-ceramic = Wang A et al, Role of ceramic components in the era of crosslinked polyethylene for THR in Zippel & Dietrich, Steinkopff, 2003

7 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.

8 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

9 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.

10 Modern Implants & Ceramics ~1990 s

11 U.S. TRIALS: more than 5,000 patients 1996 Osteonics, Wright , Encore Smith & Nephew Implex Biomet : Murphy et al AAOS 2005: D Antonio et al 2007: Seminars Arthroplasty Sedel et al: 30-year success alumina-alumina

12 Concerns: Fracture Risk? ~1/25,000 Reason? U.S. IDE Technical Deviation Murphy et al 2006

13 Fracture origin? Taper Bore- Metal Junction Multiple Dislocation? Metal Discoloration

14 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

15 Metal Staining of Alumina?

16 Recurrent Dislocations with Alumina Obvious implant/liner damage Metal debris and ceramic debris Femoral heads intact Heavy staining (Aldo Toni AAOS 2006)

17 Surface changes on SEM Interposed metal particles? Metal + Scratches? 5 m cycles in vitro (Bal, Li 2006)

18 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

19 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.

20 Ceramic Countersurface in TKA Breakage? Oonishi, Akagi Alignment, Wear

21 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

22 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

23 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

24 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):

25 Fracture Toughness Mechanisms Si 3 N 4 s improved toughness is solely mechanically activated. 25

26 Fracture Toughness Mechanisms ZTA s toughness is chemically-mechanically activated. 26

27 Silicon Nitride in the Spine 30,000 implants; 8 years 27

28 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

29 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

30 Silicon nitride is Osteoconductive Only Porous Structural Ceramic Micro-CT ovine femur Ingrowth at 4 weeks 30

31 As-fired silicon nitride is nano-textured, plus favorable ph, hydrophilic, and ionic surface properties N 2 - Anneal 9 2 R a = 336 nm R a = 296 nm 31

32 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

33 Supported by 40+ papers 33

34 Thank you for your attention