Polyethylene Damage Mechanisms in Total Hip & Total knee Surgeries ,DR.SANDEEP AGRAWAL Agrasen Fracture Hospital Gondia Maharashtra Cause for Failure or Revision for Joint Replacement surgeries THR , TKR Hip Knee Pain Instability

1. Polyethylene Damage Mechanisms
in Total Hip & Total knee Surgeries
Dr.Sandeep Agrawal,
Bone Joint Surgeon,
Agrasen Hospital,
Gondia
Maharashtra
India
drsandeep123@gmail.com
09960122234

2. Polyethylene Damage Mechanisms
 Delamination
 Adhesive/Abrasive
2
Wear
 Pitting
 Creep
 Cold Flow

3. Delamination

4. Delamination
 Delamination occurs due to initiation
and propagation of subsurface cracks
and can result in the removal of large
(>0.5-mm) flakes of polyethylene
wear debris.
 Crack initiation and propagation occur
when materials fatigue following
repetitive stresses.

5. Crack
 Tibial insert subjected to compressive stresses immediately
under the contact area, with a peak stress at a depth of 1 to
2 mm below the surface
 Stresses outside the contact area are reversed and are tensile
in nature.
 As a result, during the rolling-sliding motion of the femoral
component, subsurface region of polyethylene is subjected to
completely reversing cycles of stress, i.e., compression and
tension.
 This fluctuating stress environment is precursor to fatigue,
leading to the initiation and propagation of cracks in the
material.

6. Delamination
 Primary cause of most polyethylene-related
total knee failures
 result in loss of geometric conformity
 alter pattern of load distribution
 eventually result in accelerated implant
failure by disengagement or fracture of tibial
insert or wear-through .

7. WEAR :
motion between surfaces  loss of
material from the surfaces of the prosthesis
plastic deformation
CREEP  implant shape change, not
causing loss of material or producing
particulate debris
7

8. Wear
8
Adhesive wear
Abrasive wear
Transfer wear
Fatigue wear
Third body wear

9. Adhesive/Abrasive Wear
contributes to implant failure mainly by
generating particulate debris that
results in periprosthetic osteolysis

10. Abrasive wear
Generation of wear debris from the
cutting and removal of the soft
polyethylene articular surface by hard
asperities on the femoral component
By hard third-body particles, such as
bone chips or bone-cement particles

11. Adhesive Wear
 Adhesive wear causes removal of
small particles of wear debris, usually
a few micrometers or smaller in size
 It is initiated by orientation and strain
hardening of the implant surface

12. Adhesive Wear
 M-G I PE s/p 10y/o
 Lace or ripple ,are
the likely
precursors to
adhesive/abrasive
wear
lace ripple

13. Adhesive Wear
 Occurs at primary articulations, i.e.,
the tibiofemoral and patellofemoral
articulations, and at backside,and
tibial post-cam articulation of posterior
stabilized total knee designs

14. Pitting
 Pitting is another fatigue-related
phenomenon
 results from the coalescence
of shallow subsurface cracks
or cracks initiated on the
surface
 occurs mostly on the articular
surfaces, does not result in a
substantial loss of material.

15. Creep
 Permanent deformation resulting from
prolonged application of a stress
below the elastic limit

16. Creep
 Deformation that occurs over period of time
when a material is subjected to constant
stress at constant temperature
 In metals, creep usually occurs only at
elevated temperatures.
 Creep at room temperature is more common
in plastic materials and is called cold flow or
deformation under load.

17. Cold flow
 Permanent deformation of plastics
remaining after load applied at
temperature below distortion
temperature is removed.
 It is an alternate term for creep in
plastics (ASTM D-674) and rubber
(ASTM D-530).

18. Cold flow
 The distortion, deformation, or
dimensional change which takes
place in materials under continuous
load at temperatures within the
working range (cold flow is not due to
heat softening).

19. Polyethylene Damage Mechanisms
 extent of oxidative embrittlement of the
polyethylene resulting from gamma
sterilization in air
 stress state of the components
implant design
PS designs generally have more conforming
articulating surfaces than CR type, lower stress levels
polyethylene thickness
thicker inserts provide more cushioning and
lower stresses in the polyethylene than do thinner ones
soft-tissue stability
component alignment

20. method of sterilization of
polyethylene components
 gamma irradiation in air 55% Delamination
reaction of oxygen with the residual free radicals that are
generated by gamma irradiation, leads to the degradation of the
mechanical properties of polyethylene.
embrittlement
 ethylene oxide gas 0% Delamination

21. resin type and the consolidation
method affect the delamination
resistance
 Himont 1900 polyethylene resin in
combination with direct compression-molding
has been shown to have
superior resistance to delamination
 ram-extruded GUR 4150 resin

22. Application of crosslinking technology
in total knee replacement
 high-dose radiation used to achieve a
high crosslink density
 followed by melting to eliminate the
residual free radicals
 substantially increases the
delamination resistance of
polyethylene after accelerated aging

23. Application of crosslinking technology
in total knee replacement
 The preliminary in vitro knee simulator
testing of highly crosslinked polyethylenes
suggests that these polyethylenes reduce
adhesive/abrasive wear and eliminate
delamination
 Two types of highly crosslinked polyethylene
tibial inserts have been in clinical use for
more than one year, and there have been no
reports of early in vivo complications.