Dr. Michael Gentile, DPM, fellow of the American College of Foot and Ankle Surgeons, lends his perspective on future coating technologies and ways to engage coating’s important role in a device. Special focus is given to titanium-integrated PEEK surfaces.
5. The Grand Conundrum
Goals of the Surgeon/Patient vs. Reality.
Correction of deformity and retention of results.
Implant compatibility and respect for anatomy.
Boney healing and return to function.
EFFICIENT HEALING
6. The Status Quo:
A Block of Bone
Autograft
Retains bioactivity.
Moot points:
Disease transmission
and immune response.
Donor site morbidity.
Allograft
Essentially dead bone.
Disease transmission and
immune response are real
concerns.
Donor won’t miss it.
7. Challenging the Paradigm
Block of Bone:
Requires osseo-
integration by creeping
substitution.
Requires fixation to
avoid loss of correction.
Allograft requires
augmentation.
PRP
BMAC
8. Other Than Bone?
Titanium
Should retain correction.
Allows osseointegration.
BUT….
Different elastic modulus
Stress shielding.
Possible subsidence.
Chemically active
0
20
40
60
80
100
120
Ti-Alloy Cortical
Bone
PEEK /
TiPEEK
Cancellous
Bone
ElasticModulus(GPa)
17 4 2.3
110
9. The Elastic Modulus
Elastic modulus and stress shielding are
~ directly proportional.
Elastic modulus > Bone MAY RESULT in aseptic
loosening of implant overtime.
Possibly despite efforts to make a more porous titanium.
1. Engh CA et al: JBJS Br 1987: 69(1),45-55.
2. Bobyn et al: Clin Orthop Rel Res 1992: 274, 79-96.
3. Nagels J et al: J Shoulder Elb. Surg. 2003: 12(1), 35-39
10. The Ideal Alternative
Provides predictable and
efficient healing.
Material is inert and
similar to bone.
May not require
supplemental fixation.
Deformity correction
is maintained.
Potentially quicker
return to function.
Cost effective.
11. Why PEEK?
Mechanical
EPEEK similar to native bone
Allows strain transfer to adjacent bone=bone remodeling
Visual
Radiolucent (PEEK) vs. Radiopaque (Ti)
Chemical
Bioactive (Ti) vs. Bioinert (PEEK)
Topographical
Surface features direct cell-substrate interactions
Macro, micro, and nano
1. Davies, J. E. Biomaterials 28, 5058–5067 (2007).
2. Kurtz, S. M. & Devine, J. N. Biomaterials 28, 4845–69 (2007).
3. Rho, J. Y., Ashman, R. B. & Turner, C. H. J. Biomech. 26, 111–119 (1993).
12. Osseointegration: It’s all about the osteoblasts.
Adhesion to the implant surface
Osteoblast proliferation
Bioactivity of the osteoblasts
13. PEEK Ti-6Al-4V Ti-PEEK
Samples characterized for:
• Surface topography
• Osteoblast response
• Adhesion
• Proliferation
• Calcium deposition
This in vitro study examined the response of human osteoblasts
to PEEK, titanium, and Ti-PEEK surfaces
Cross-sectional SEM of
the Ti-PEEK interface
14. Increased Surface Roughness
PEEK Ti
Ti-PEEK
From atomic force microscopy analysis,
the Ti-PEEK surface provides ~30%
more surface area per sq. micron
of projected area
The Ti-PEEK surface
exhibits roughness at the
macro, micro, and nano levels.
Macro: friction fit Micro: cell growth surface area Nano: cell-substrate interactions
15. Osteoblast Adhesion and Proliferation
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
4 hrs 4 days 7 days 14 days 21 days
OsteoblastViability(OD490)
PEEK
Ti
Ti-PEEK
*
**
*
**
*
**
*
*
PEEK
Ti
Ti-PEEK
Osteoblast viability measured via an MTS cell viability assay
Data is avg. +/- stdev., N = 3, *p<0.001 compared to PEEK,
**p<0.001 compared to Ti
• Ti promotes clear improvement compared to PEEK.
• Rough Ti-PEEK surface provides more area for proliferation.
• Ti-PEEK micro- and nano-features enhance
osteoblast differentiation.
16. Enhanced Osseointegration
Surface calcification: TiPeek is superior
Up to 305% compared to Titanium
Up to 470% compared to PEEK
Does this equal less chance of aseptic loosening?
Load sharing
May be as high 38% irrespective of PEEK
porosity or bone ingrowth.
Can this allow earlier WB and less aseptic loosening?
Economy of time:
This can happen as early as 4 weeks.
17. The Great Race
Adequate
osseointegration
Early mobilization
and WB
-Less dysfunction
-Less aseptic loosening
-More predictable results
Titanium never catches
up to PEEK in terms of
load sharing.
Titanium has <50% bone
ingrowth in short term
analysis.1
In fact, bone resorption
may actually occur over
time.2-5
1. Jensen, W.K., et al.: 2005Spine 30 (22), 2497–2502.
2. Sumner et al: 1995 J Arthroplasy 10(2), 67-67
3. Hanzlik J 2016 Ortop. Proc 98-B (Supp 2).
4. Hanzlik J 2013 J Arthroplasty 28(60, 922-927
5. Hanzlik J 2015 J. Arthroplasty 30(6), 1073-1078
27. Bringing It Home
Current clinical practice is to utilize blocks of bone.
Thought Leaders:
Titanium or Titanium coated PEEK (Ti-PEEK).
Ti-PEEK makes the most sense:
Elastic modulus similar to bone.
Titanium coating with unique surface properties:
Increase co-efficient of friction.
Enhanced osteoblast adhesion and bioactivity.
Increased calcium deposition…Osteointegration.
