1. Total hip arthroplasty has evolved significantly since its origins in the late 1800s through improvements in materials, designs, fixation methods, and surgical techniques. 2. Cementless fixation and improved bearing surfaces have led to improved implant survivorship and reduced osteolysis. 3. Current areas of focus include minimizing wear through novel bearing surfaces and coatings, inhibiting the cellular response to wear debris, and improving surgical techniques through minimal access approaches and computer navigation.

1. TOTAL HIP ARTHROPLASTY
Many mountains climbed
- many yet to conquer

2. HISTORICAL REVIEW
The present, like a note of music,
is nothing but as it appertains to
what is past and what is to come
Walter Landau

3. Hip arthroplasty
 interpositional
 excision
 replacement

4. Interpositional arthroplasty

6. Excision arthroplasty

7. Hemiarthroplasty

8. Judet

9. Austin Moore Thompson

10. TOTAL HIP REPLACEMENT

11. 1891

12. 1938

15. The cart has been
put before the horse:
the artificial joint has
been made and used,
and now we are trying
to find out how and
why it fails
Charnley 1956

16. Charnley’s 3 major contributions
 low friction torque arthroplasty
 introduction of high density
polyethylene
 use of acrylic bone cement to
secure implant fixation to bone

18. Survivorship
 81% at 25 year follow-up
(revision of any component as
end point)
Berry et al 2002
 77% at 25 year follow-up
(revision of any component as
end point)
Callaghan et al 2000
(also Kavanagh, Wroblewski, Older, etc)

19. Why change component design?
Are we addressing a non-problem?

20. Two basic design concepts
 composite beam
 taper slip

21. Composite beam
“Shape closed” design
Roughened surfaces
and precoating
contribute to perfect
bond between stem
and cement

22. Taper slip
Highly polished double
tapered stem
Designed to settle in
the cement mantle thus
re-engaging the taper
and becoming
progressively more stable

23. Debonding at the cement-metal
interface represents the initiation
of loosening of cemented femoral
components
Harris 1992
Slip between metal and cement is
essential to protect the cement-
bone interface
Fowler et al 1988

24. Triple tapered stem
? improves loading
of the calcar and
preservation of the
bone in the long term

25. “I think my major
contribution was
the concept of
achieving fixation
entirely by means
of cement”
Charnley 1970

26. Cement is a grout not a glue
 the surface area of the truncated cone of
cement presents a much larger surface
area than the stem
 when loaded, a cemented prosthesis
transfers the load to the endosteal
surface through hundreds of trabeculae

27. Cementing techniques

28. Can we improve the mechanical
properties of cement?
Norwegian Hip Study
1987-99
→ probably not

29. There is no such thing
as a small change

30. Exeter
- surface finish
 matte 10% revised at 10 years
 polished 2.5% revised at 10 years

32. 3M Capital stem
 6 year survival of modular
flanged stem: 84%
 ? rounded medial and lateral
surfaces below the shoulder
reduced torsional stability
? Material (titanium)

33. CEMENT DISEASE
Jones & Hungerford 1987
→ cementless fixation

34. CEMENT DISEASE
Particle disease
Particle access
disease

35. CEMENTLESS FIXATION
Objectives
Primary
 immediate press-fit stability
 durable biological fixation
Secondary
 biomechanical compatibility
Avoid
thigh pain
stress protection osteopenia

36. Distal fixation may predispose to
 thigh pain
 proximal stress
protection
osteopenia

37. Reducing the stiffness of the stem
can reduce thigh pain and reduce
proximal stress protection osteopenia

38. Bioactive coatings
 tricalcium phosphate
 hydroxyapatite

39. Makes the osteocyte more athletic
Can bridge gaps up to 2mm

40. Mid-term results with the
cementless hip replacement
 100% survival of the femoral
component at 10 years
Archibeck et al 2001
 99% survival of an HA coated
femoral stem at 9-12 years
McNally et al 2000

41. CEMENTED FIXATION
Mechanical interlock: static: quality
of bone, cement and consequently
fixation degrade with time
CEMENTLESS FIXATION
Biological osseo-integration:
dynamic: bone replaced and quality
of fixation maintained

42. “Periprosthetic osteolysis
is the leading problem in
contemporary THR”
Harris 1995

43. STRATEGIES FOR THE
PREVENTION OF OSTEOLYSIS

44.  prevent particle access
 ↓ number of particles
 inhibit cellular response
(“pharmacological”)

45. PREVENT PARTICLE ACCESS
Cementless implantation
 enhanced
circumferential
osseo-integration
(? bioactive coating)

46. Cemented implantation
 effective cementation to
avoid early bone cement
interface lucencies

47. Ritter et al (1999) demonstrated
38-fold increase of cup loosening
associated with wear if early post-
operative x-ray demonstrated
bone cement lucency in zone 1

48. Interface can be sealed to exclude
wear debris with PTFE GORE-TEX
membrane + butyl cyanoacrylate
glue
Bhumbra et al 1999

49.  physical seal
- membrane excludes fibrous
ingrowth and enhances
osteogenesis
↓
 secondary biological seal

53. Reduce number
of particles

54. The great tragedy of science -
the slaying of a beautiful hypothesis
by an ugly fact
Thomas Huxley

55. Highly cross-linked polyethylene
 ↓ wear
 ↓ # toughness
 more vulnerable to
abrasive environment

56. In an abrasive environment
↓ fracture toughness associated with
an increased number of particles
and
an increased number in the
biologically active range
“Watch this space”

57. Hard-on-hard bearings
Ceramic
 ↓ surface roughness (Ra 0.02)
 wettability
↓ coefficient of friction
 hard - not scratch sensitive

58. Ceramic-ceramic
 alumina must be of high quality
(roughness/sphericity)
 tight tolerances must be
maintained in the manufacture of
the bearing surfaces
 clearance must be <10 µ m

59. 
acetab
ular
implan
t
should
not be
implan
ted too

60. Advantages
 low coefficient of friction
 does not degrade with time
 minimal wear
 0.25 microns per year
 4000 x less than M/P coupling
Dorlot 1992
 alumina is an inert material and
the wear particles excite a limited
inflammatory response
Lerouge et al 1992

61. Disadvantages
 brittle
 do not mix and match femoral heads
and morse tapers
 avoid scratching the morse taper and
clean thoroughly before applying the
head
 avoid heavy hammering

62. 1978 - 2000
 > 3000 Al/Al couples
 1 # head
 1 # socket
Witvoet 1999
 1763 femoral heads
 1 # (0.06%)
Fritz and Gleitz 1996

64. Metal-metal couple
1938

65. Look for new ideas in old
books, because old ideas
are found in new books

66. Early metal-on-metal
articulations had a high rate
of early loosening and failure
 stainless steel
 small clearance
↓
 equatorial bearing with
↑ frictional torque

67. Clearance
 optimised clearance ↑ contact area
but avoids equatorial bearing
(minimum 30 - 50 µ m)
 ↓ angle of convergence ↑ thickness
of fluid film
→ ? fluid film lubrication

69. Metal-metal couple
 wear 80 times less than metal on
polyethylene
Metasul
 25 µ m during first million cycles
then 4 - 10 µ m per million cycles
Nelson and Dyson

70. Polyethylene Metal-Metal Ceramic-Ceramic
Wear volume mm3/year 30 1.6 1
Particle size (mode) nm 300 30 30 and 500
Number of particles 500 50 000 1 000 to 10 000
billion/year

71. Small particles do not excite an
inflammatory response but are
biologically active

73. Inhibition of cellular response
 bisphosphonates directly inhibit
osteoclastic activity
 reduce mechanically related
loosening of hip prostheses

74.  established ovine model of hemi-
arthroplasty where significant
stress-shielding of the calcar and
medial cortex results in significant
bone resorption at 6 - 12 months

78. Hip resurfacing
Smith Petersen
developed a CoCr
resurfacing head in the
1930s
Charnley used a
resurfacing design in the
1960s
 teflon-on-teflon
bearing
 very low friction
 very high wear!!

79. Resurfacing arthroplasty (RA)
1970s/1980s
 Wagner
Wagner
 ICLH
 Tharies etc
Freeman ICLH

80. Large heads
 “high wear” bearings
Thin polyethylene
 → catastrophic failure of the cup

81. Tharies - clinical results
Failed Wagner device

82. Large bore metal-on-metal
articulations
 McKee Farrar
 Ring
 Muller

83. Poor early results
 poor materials
 poor tolerances
 equatorial bearing

84.  later implants have better
tolerances and polar bearing
 good long-term results with
excellent wear characteristics

86.  the 20 year survivorship for
metal-on-metal was better
than for metal-UHMWPE
Jacobsson, Djerf & Wahlstrim 1996

88.  RA is not new
 neither is a metal-on-metal
couple
Improved technology has produced a
reconciliation and a happy
marriage
RA
MoM

89. FUTURE TRENDS -
A CLINICAL PERSPECTIVE

90. Coatings have failed due to harsh
environment which has often led
to separation of the coating
However, if successful they could:
 improve wear
 reduce friction
 improve biocompatibility

92. Surgical technique
 instrumentation to provide
reproducibility
(in everyone’s hands!)

93. Implant
 proximal loading
 conservative
 no thigh pain
 reduced proximal stress protection

95. PROXIMA
 conservative
metaphyseal
loading implant
 lends itself to MIS

97. Conservative implants
Neck Fixation Short Stem Resurfacing
Sulzer: TTP Waldemar-Link: CFP Midland Medical: BHR
Eska: Cut2000 Zimmer: Mayo Wright Medical: Conserve
Eska: Cigar Sulzer: Stellcor
Corin: Cormet 2000
SHO: Biodinamica

98. Surgical technique
 image guided systems
 minimal access surgery

99. Minimal access surgery
 instruments
Position and cut head
Enlarge hole splitting
Drill head head into four sections
Enlarged view of oscillating saw

100. Expandable reamer
Retractor

102. Conservative philosophy
If your preferred hip will
outlast the patient
→ use it
Otherwise...

103. Preserve bone stock
Think about the next operation

104. Biological solutions
 bone has the intrinsic capacity
to regenerate structurally and
functionally

105.  articular cartilage, menisci,
tendons and ligaments have
little or no ability to regenerate
a replica of normal tissue

106. Tissue engineering
 creates biological tissues using
cells + matrix + bioactive factors
for the replacement of the
diseased tissues or organs

107. BMP mitogenic
synthetic matrices
chemotactic adhesion
stem cell
progenitor cell
induction
biological polymers
cohesion
TGF conduction

108. Autologous chondrocyte
implantation
(Carticel - Genzyme Tissue Repair)

109. Key concepts
Chondrocyte implantation: 6 months
 evidence of hyaline cartilage formation
 chondrocytes are in lacunae
 columnar organisation
 integrated into subchondral bone

110. Articular cartilage has a highly
sophisticated ultrastructure

113. Gene therapy
Gene therapy can be effected by
 ex vivo modification with the
gene re-introduced into the
body after modification or
 in vivo modification which is
done in situ

114. Can these strategies exert
structure modifying effects to
counteract the disease process?

115. The delivery of genes that
encode the anti-arthritic proteins
may present a biological drug
delivery system
Hendon et al 1999
but...
Safety is an overriding concern

116. Gene delivery vector delivers a
stable gene which permits
stable and regulated production
of therapeutic proteins

117.  suppression of the activities of
lymphocyte co-stimulatory
molecules
 against anti-lymphocyte antigens
(CDH)
 suppression of IL-1 and TNFα
etc

118. Strategies for gene therapy
in arthritis
 gene replacement
- substitution of a non-active or
defective gene, e.g. type II
collagen mutation in familial OA

119.  gene addition
e.g. IL-1 receptor antagonist
and
 gene control, where the
expression of a gene is controlled
e.g. for a specific cytokine

120.  onset of OA may be prevented
or delayed by transfection of
articular cartilage chondrocytes
with HPV proto-oncogens which
will slow the progression of
chondrocyte senescence or
replace senescent cells

121. 2000
Biological solutions will supersede
biomechanical solutions
Prevention will reduce the
need for surgery
but…

122. 2010
25% of the population will be
≥ 60 years
40% of these will have arthritis

123. THR is still in the ascendency
for the foreseeable future

124. A surgeon should be as
knowledgeable of the biological
consequences of implanting the
material and prostheses he uses
as the physician is about the side
effects of any drugs he prescribes

126. Many mountains climbed...
...many yet to conquer