Highly cross-linked polyethylene (XLPE) has been shown to reduce wear rates compared to conventional polyethylene in hip replacements. This reduced wear is associated with lower rates of osteolysis. XLPE appears compatible with large diameter heads, though thin liners may be at increased risk of early failure. Fatigue properties of XLPE are favorable though long-term data is still needed. Ceramic-on-ceramic bearings have the lowest wear rates of any bearing surface but can fracture, though modern designs have low fracture risks. Ceramic generates fewer inflammatory particles than other bearings and may have the best long-term durability without osteolysis. Metal-on-metal bearings are no longer recommended due to high revision rates

1. Alternative Bearing Surfaces-
Evidence So Far.
Dr Rajesh PDr Rajesh P
Government Medical College,Government Medical College,
KozhikodeKozhikode

2. Tribology
• Science of interactive surfaces
in relative motion
• Incorporates the concepts of
wear, friction, and lubrication

3. Bearing Surface
Bearing surface is
the area of contact
between two
objects
– Primary bearing
surface
– Secondary
bearing
surfaces

4. Hip arthritis is a problem of the bearing
surface

5. Bearing surfaces
• Perpendicular to the force transmitted
• Subject to relative motion
• Relative motion of two surfaces in
contact is resisted by the force called
friction
• This leads to wear

6. Wear
• Is the removal of material from
opposing and moving surfaces under
an applied load
• The primary mechanisms of wear are
– Abrasion
– Adhesion
– Fatigue
– Third-body wear

7. Cause of Wear
• Wear occurs mainly due to motion
between articulating surfaces
• It may also occur due to
unintended impingement or motion
• Wear leads to formation of wear
particles

8. Effect of Wear Particles
• Mechanical
• Biological
– Direct cytotoxicity
– Immunological response
– Carcinogenicity
– Systemic toxicity

9. Low Friction Arthroplasty- Charnley
• Stainless steel head on UHMWPE
cup articulation
• Bone cement for fixation
• Small head to reduce wear

10. Polyethylene
• Discovered in 1935
• Viscoelastic and thermoplastic polymer
• Long chains of the monomer ethylene
(C2H4)n
• All carbon-carbon and carbon-hydrogen
bonds are single

11. Types of Polyethylene
• Low-density polyethylene - Density of
0.910 to 0.940 g/cm3
• High-density polyethylene - Density
greater than 0.941 g/cm
• UHMWPE - Average molecular
weight of greater than 3 million
g/mol

12. UHMWPE
• Extremely long chains of ethylene
• Crystalline domains embedded within an
amorphous matrix
• Mainstay of joint replacement over last 40
years

13. Results in Elderly
• Very good long term results
• Remains the gold standard in elderly
• Geriatric patients with low activity
demands

14. Operation of the 20th
century
Learmonth I. The operation of the century:
total hip
replacement. Lancet 2007;370:1508-19

15. Extended Indications for THR
• Its success expanded its use in
more active patients younger than
65 years
• 270,000 THRs in USA per year
and 70,000 in UK per year
• 12% in those less than 55 years

16. Results in the Young
Longevity & High demands
• 15 year survival rate is less than 60% in
those less than 55 years.
• Osteolysis seen in 60% of young active
patients with UHMWPE at 5 years.
Schmalzried et al The mechanism of loosening of cemented acetabular
components in total hip arthroplasty: analysis of specimens retrieved at autopsy.
Clin Orthop 1992;274:60-78

17. THRs in patients under 30 years
– 49 hips in 44 patients
– HA coated stem and cup
No stem revisions at 10-16 years
24 out of 49 cups revised due to
loosening
H. Wangen . Hip arthroplasty in patients younger than 30 years: excellent
ten to 16-year follow-up results with a HA-coated stem . International
Orthopaedics (SICOT) (2008) 32:203–208

18. Prosthetic Failure
• Aseptic loosening and osteolysis
secondary to wear are the
primary cause of failure
• Second major cause is dislocation
seen in about 4% mostly in the
first 6 months

19. Cause of Osteolysis
• Cement was thought to be the
cause ‘Cement disease’
• Polyethylene wear particles
are the cause for osteolysis

20. Reduction of wear strategies
• Improved designs to lower contact
stresses and sliding distances between
moving parts.
• Altering the structure of polyethylene-
Process of cross-linking.
• Avoid the use of polyethylene

21. Cross-linked Polyethylene

22. Cross-linked Polyethylene (XLPE)
• Is it more resistant to wear?
• Has it reduced osteolysis?
• Is it compatible with large diameter heads?
• Is there any increase in fatigue related
failures?
• Is the longevity better?

23. Is XLPE more resistant to wear?
74% reduction in total penetration of
highly cross-linked polyethylene when
compared with
conventional polyethylene at an
average of 9 years
Wear analysis of first-generation highly cross-
linked polyethylene in primary total hip arthroplasty: an average
9-year follow-up. Reynolds SE et al. J Arthroplasty. 2012
Jun;27(6):1064-8

24. Evidence for reduced wear
• Rajadhyaksha . Five year comparative study of highly crosslinked (Crossfire) and traditional
polyethylene. J. Arthroplasty. 2009;24:161-167.
• D’Antonio. Five year experience with Crossfire highly crosslinked polyethylene Clin Orthop
2005;441:143-150
• Engh. A randomized prospective evaluation of outcomes after THA using cross-linked
marathon and non-crosslinked Enduron polyethylene liners. J. Arthroplasty. 2006;21(Suppl)
17-25
• Mutimer.Highly cross-linkedpolyethylene reduces wear in THA at 5 years CORR
2010;468:3228-3233.
• MacCalden. Wear rate of highly crosslinked polyethylene in THA.A RCT. JBJS A 2009 91A
773-782.
• Geerdink. Cross-linked compared to historical polyethylene in THA: An 8 year clinical study.
CORR 2009;467:979-984.

25. Does reduced XLPE wear lower
osteolysis?
• Incidence of osteolysis was 22% vs 0% for
cross-linked
• Survivorship at 10-years was 94.7 ± 4.6%
vs 100% for cross-linked
• Mean linear wear rate - 0.22 mm/yr vs
0.04 mm/yr for cross-linked
A prospective, randomized study of cross-linked and non-cross-
linked polyethylenefor total hip arthroplasty at 10-year follow-up.
Engh CA Jr et al. J Arthroplasty. 2012 Sep;27(8 Suppl):2-7.e1.

26. Does reduced XLPE wear lower
osteolysis?
• XLPE cups had a lower wear rate between 2 and
10 years compared to conventional PE hips:
0.005 mm/year versus 0.056
mm/year
• No differences in cup migration, bone mineral
density, radiolucencies, functional scores, and
revision rate.
Highly crosslinked polyethylene does not reduce aseptic loosening
in cemented THA 10-year findings of a randomized study. Johansen
PE et al. Clin Orthop Relat Res. 2012 Nov;470(11):3083-93

27. Other evidence for reduced osteolysis
• Engh CA, Jr, Stepniewski AS, Ginn SD, Beykirch SE,
Sychterz-Terefenko CJ, Hopper RH, Jr, et al. A
randomized prospective evaluation of outcomes after
total hip arthroplasty using cross-linked marathon and
non-cross-linked Enduron polyethylene liners.
J.Arthroplasty 2006;21(6 Suppl 2):17–25.
• Illgen RL,2nd, Forsythe TM, Pike JW, Laurent MP,
Blanchard CR. Highly crosslinked vs. conventional
polyethylene particles—an in vitro comparison of biologic
activities. J Arthroplasty 2008;23(5):721–31.
• Illgen RL, 2nd, Bauer LM, Hotujec BT, Kolpin SE,
Bakhtiar A, Forsythe TM. Highly crosslinked vs.
conventional polyethylene particles: relative in vivo
inflammatory response. J Arthroplasty 2009;24(1):117–24

28. Is it compatible with large diameter
heads?
• Two important issues have been
dislocation and wear
• Larger heads reduce dislocation and
increase range of movement but increase
poly wear
• Rim cracking and catastrophic liner failure
with conventional polyethylene if thickness
is less than 5mm

29. Is it compatible with large diameter
heads?
• XLPE cups of 3.8mm Vs 5.8mm
• No difference between the groups
• However most investigators
advise against the use of thin
shells
Early Outcomes of Sequentially Cross-Linked Thin Polyethylene
Liners with Large Diameter Femoral Heads in Total Hip
Arthroplasty. Siraj Sayeed et al. Bulletin of theNYU Hospital for Joint
Diseases 2011;69(Suppl 1):S90-4

30. Thin shells may lead to early failure
•4 cases of early failure within one year
reported
Tower SS, Currier JH, Currier BH, et al. Rim
cracking of the cross-linked longevity
polyethylene acetabular liner after total hip
arthroplasty. J Bone Joint Surg Am.
2007;89(10):2212-7.

31. Is there any increase in fatigue related
failures?
• Crosslinking leads to unfavourable changes
in the ultimate tensile strength, ductility,
modulus, toughness, and crack propagation
• But long term effects is not available
• So far clinical outcomes are favourableSo far clinical outcomes are favourable
• Pruitt LA. Deformation, yielding, fracture and fatigue behavior of
conventional and highly cross-linked ultra high molecular weight
polyethylene. Biomaterials 2005;26(8):905–15.
• Bradford L, Baker D, Ries MD, Pruitt LA. Fatigue crack propaga-tion
resistance of highly crosslinked polyethylene. Clin Orthop Relat Res 2004;
429:68–72.

32. Metal-on-Metal Articulations

33. MoM
• In clinical use longer than any
bearing surface
• Most commonly used option until
the 1970s
• The most apparent advantage is
its greater resistance to wear

34. MoM
• Has an initial run-in phase of increased
wear followed by steady state wear phase
• Yearly run-in wear rate is 25 µm
• Steady-state wear of 3 to 7 µm
• Equal to only 2% of the wear rate of
UHMWPE
• Theoretically should last a life time even in
the young

35. Particle number
• MOM articulations produce
approximately 6.7 X 1012 to 2.5 X
1014 particles each year
• 13500 times the number of
polyethylene particles produced
by MoP articulations

36. MoM Bearings
• 5-10 times increase in the serum
metal ion levels
• Hence not advisable in women of
child bearing age
• Long term effects is a concern

37. Effect of increased metal ions
• Carcinogenesis, metal sensitivity and
organ toxicity
• Locally unusual lymphocytic
aggregates called acute lymphocytic
vasculitis associated lesions (ALVAL)
or pseudotumour are seen

38. ALVAL
Images from Internet, found on google image search

39. Australian Orthopaedic Association
National Joint Replacement Registry
• First reported increased revision rates in
2008
• Larger MoM femoral heads were
associated with more than two times the
rate of revision as that associated with
smaller MoM femoral heads. (9.4%: 4.5%)

40. Seventh Annual Report (2010) of the NJR
for England and Wales Registry
• At five years, the rate of revision of large
femoral head MoM prostheses was at least
twice that of all other cemented, hybrid,
and conventional total hip replacements.

41. A Multinational Assessment of Metal-on-
Metal Bearings in Hip Replacement
Data from the Australian, England and
Wales, and New Zealand registries
Increased rate of revision for large
femoral head MoM prostheses when
compared to other bearing surfaces
Stephen E. Graves et al. A Multinational Assessment of Metal-on-Metal
Bearings in Hip Replacement. J Bone Joint Surg Am.2011;93 Suppl 3(E):43-7

42. Risk of revision
Product 5 Year
revision rates
ASR 7.8%
BHR 4.9%
Cormet 7.1%
Metasul 4.6%

43. Metal-on-Metal Bearings
• National Joint Registry of England and
Wales for primary hip replacements (2003-
2011)
• 402,051 THRs
• 31,171 were stemmed metal-on-metal

44. Risk of revision
From Lancet

45. Rate of MoM THRs
From Lancet

46. “Metal-on-metal stemmed articulations give
poor implant survival compared with other
options and should not be implanted.
All patients with these bearings should be
carefully monitored, particularly young
women implanted with large diameter
heads.”

47. Metal-on-Metal Bearings
“The lack of a clinical advantage with metal
bearings and the significant downsides to t
he use of metal on metal mean that, in the‐ ‐
author’s opinion this bearing option
should be used with
great caution, if at all.”
The Journal of Arthroplasty Vol. 25 No. 1 2
010
Editorial

48. Ceramic-on-Ceramic Bearings

49. Ceramic on Ceramic (COC) Bearings
• Ist
Generation- 1974-88 – Low density, high
porosity and large grain size, Either
cemented or press-fitted.
• IInd
Generation -1988-94- Increased purity
and smaller grain size. Titanium shell with
alumina liner

50. Ceramic on Ceramic (COC) Bearings
• IIIrd
Generation- 1994 onwards- Better
manufacturing and quality control- hot
isostatic pressing, laser etching and proof
testing
• IVth
Generation- Alumina – Zirconia-
Strontium oxide matrix composite-2000
onwards

51. Improvement over generations
Property I & II
generation
III
Generation
IV
Generation
Bending
strength
400 580 1150
Fracture
toughness
4 4.3 8.5
Vickers
hardness
20 20 19
Grain
size
7.2 1.8 0.6
Young’s
modulus
380 380 350
Hot
isostatic pressing
No Yes Yes

52. Tribology of CoC
• Smaller grains
– Low surface roughness
• Reduced friction
• High hardness
– Low wear rate
• High wettability
– Fluid film lubrication

53. Evidence on Ceramic-on-Ceramic
• Is it more resistant to wear?
• Has it reduced osteolysis?
• Any unique complications?
• Is the longevity better?

54. Is it more resistant to wear?
Mean total wear at five years
• 0.869mm for the conventional polyethylene
• 0.329mm for the HXLPE
• 0.035mm for the CoC group0.035mm for the CoC group
A prospective randomised controlled trial comparing three alternative bearing
surfaces in primary total hip replacement. V. S. Nikalaou et al. J Bone Joint
Surg Br 2012; 94-B:459-65

55. Has it reduced osteolysis?
• Reaction to alumina wear debris is
fibrocytic with very few macrophages
and no giant cells
• Lower concentration of wear particles
in the periprosthetic tissue

56. Has it reduced osteolysis?
CoC is the only bearing that has
long term survival without adverse
reaction to wear debris

57. Any unique complications?
Liner Fracture
• Ceramic is a brittle material with no
ductility and limited bending strength
• Old generation CoC had fracture rate as
high as 20%
• Risk of fracture with newer CoC is
approximately 0.02% to 0.1%
Hamilton WG, McAuley JP, Dennis DA, Murphy JA, Blumenfeld TJ, Politi J. THA
with Delta ceramic on ceramic: results of a multi-center investigational device
exemption trial. Clin Orthop Relat Res 2010;468(2):358-66.

58. Any unique complications?
Squeaking
• Incidence varies from less than 1% to 20%
• May be due to
– Localized “striped” wear
– Changes of fluid film lubrication conditions
– Femoral head micro-separation
• Clinically often minor and revision
indicated only occasionally.

59. Any unique complications?
Less chance to customize
• CoC systems have only one head size per
cup diameter
• No lateralized liners, elevated rims etc
• Equalizing leg lengths and maximizing
stability is more challenging
• Loss of all of these options may
currently be the most substantial
disadvantage of CC THA

60. Any unique complications?
Liner chipping on insertion
• Titanium shell is thinner than ceramic and
has only 30% stiffness of ceramic
• On impaction of liner, the shell expands
• Failure to seat the liner increases chance
of chipping
• Design related

61. Any unique complications?
Difficulties during revision
• Total synoviectomy needed
• Liner exchange may not be
sufficient as the removal may
damage the shell or taper

62. Is the longevity better?
• High survivor-ship especially in young and
active patients, with survival rates free of
revision from 90.8% to 97.4% at ten years
• Comparable but not better than the best
outcomes for both MoM, MoP and CoP
articulations
Bizot P, Larrouy M, Witvoet J, Sedel L, Nizard R (2000) Press-fit metal-
backed alumina sockets: a minimum 5-year followup study. Clin Orthop Relat
Res 134–142
Garcia-Rey E, Cruz-Pardos A, Garcia-Cimbrelo E (2009) Alumina-on-alumina
total hip arthroplasty in young patients: diagnosis is more important than age.
Clin Orthop Relat Res 467:2281–2289

63. Ceramic on XLPE Vs CPE
• Both creep and wear rates of XLPE were
significantly lower than those of CPE
• Varying femoral head material, size, implantation
period, and patient demographics had no adverse
effect on XLPE but on CPE
Wear resistant performance of highly cross-linked and annealed ultra-high
molecular weight polyethylene against ceramic heads in total hip arthroplasty
Taishi Sato et al.
J Orthop Res 30:2031–2037, 2012
Journal of Orthopaedic Research
Volume 30, Issue 12, pages 2031–2037, December 2012

64. CROSS-LINKED POLYETHYLENE WEAR IN TOTAL HIP JOINT REPLACEMENTS WITH 36MM
CERAMIC HEADS
E. Selvarajah, G. Hooper, G. Inglis, T. Woodfield and P. Devane
J Bone Joint Surg Br 2010 vol. 92-B no. SUPP I 225
J Bone Joint Surg Br 2010 vol. 92-B no. SUPP I 225
J Bone Joint Surg Br 2010 vol. 92-B no. SUPP I 225
• Assessed the rate of polyethylene wear of a
36mm ceramic femoral head and a highly
cross-linked polyethylene (X3 Stryker) liner
• Demonstrated much higher early linear wear
rates compared to other studies using 28
and 32 mms heads.
• This higher rate may be associated with the
creep phenomenon and early bedding-in.
Ceramic on XLPE - Effect of large head size

66. Conclusions
• XLPE so far shows promising results
• But long term results are yet to come
• The biological response to metal debris
limit use of MoM
• Ceramic shows promise, but have its own
unique problems