hip presentation

1. Proxima
Francesco Saverio Santori, Nicola Santori
Orthopaedics & Traumatology
Hospital S. Pietro Fatebenefratelli - Rome - Italy

2. WHY CREATE A NEW HIP IMPLANT?
THR survivorship
81% at 25 year follow-up (revision of any
component as endpoint)
Bury D et al JBJS 2002
88% at 30 year follow-up or to the time of death
(original prothesis intact)
Callaghan J et al JBJS 2004

3. WHY CREATE A NEW HIP IMPLANT?
CONVENTIONAL IMPLANTS GIVE VERY GOOD RESULT
AND THEY HAVE WIDE INCIDATIONS HOWEVER THEY
HAVE THE FOLLOWING PROBLEMS:
1. STRESS SHIELDING
2. THIGH PAIN
3. SOFT TISSUE PAIN
4. LOOSENING

4. STRESS SHIELDING
Proximal load transfer is never gauranteed with a
traditional stemmed implant

5. DIAPHESEAL FIXATION
stress shielding !!!!!

6. THIGH PAIN

7. DAMAGE TO TENDON INSERTION POINTS

8. LOOSENING

9. Bone ingrowth occurs only if the implant is very near to bone:
• 1 mm between implant and bone
(2 mm with Ha)
Therefore it's very important to have as much bone contact as
possible, i.e. circumferential contact

10. CONSERVE BONE STOCK
The next
operation!
CONSERVATIVE
PHILOSPHY

11. Conservative implants
CONSERVATION OF THE FEMORAL NECK
?
RESURFACING

12. 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!!

13. Hip resurfacing
• FEMORAL NECK FRACTURES – AN IMPORTANT
COMPLICATION OF SURFACE HIP REPLACEMENT
• 3497 surface replacement hips of the Birmingham
model.
• 50 fractures of the femoral neck
• (1.9%) in female patients
• (1.0%) in male patients
• … surgeon’s experience was thus without influence
A. J. Shimmin and D. Back, BSc : Femoral neck fractures following Birmingham hip
resurfacing. A NATIONAL REVIEW OF 50 CASES.
Journal of Bone and Joint Surgery - British Volume 2005; Vol 87-B: 463-464.

14. Hip resurfacing
Ø 37 femoral surface replacement (FSR)
Ø 24 failures (64.8%)
Failure of femoral surface replacement for femoral head
avascular necrosis.
Squire M, Fehring TK, Odum S, Griffin WL, Bohannon Mason J. - J
Arthroplasty 2005

15. Hip resurfacing
The initial experience of Birmingham
resurfacing replacement in USA :
540 cases
37 complications (7%)
10 early fractures
1 mo Malchau SICOT 2008

16. Hip resurfacing
• Difficult procedure
• Long learning curve
• Insufficient respect of soft tissues
• More bone is removed from the acetabulum in hip
resurfacing than during hybrid total hip arthroplasty,
a difference which is most marked in larger patients.

17. CONSERVATION OF THE NECK
1938

18. NECK SPARING PROSTHESIS
SILENT
ESKA
PROXIMA CFP FRIENDLY S

19. NECK SPARING PROSTHESIS
NANOS TWO STEP
METHA MODULUS MAYO

20. 3 PHILOSPHIES
a Conserve all of the neck
b
Sub Capitale (or
lower) neck cut with
c distal support
Horizontal neck cut
with metafisis 360°
contact.

21. a
Conserve all of the neck

22. a
Conserve all of the neck
SILENT
TWO STEP

23. a Conserve all of the neck
Failed conservative prosthesis can be replaced using a
primary prosthesis

24. b
Sub Capitale (or
lower) neck cut with
distal support

25. CFP
MAYO ESKA
METHA b Sub Capitale (or
lower) neck cut with
distal support
NANOS
MODULUS

26. b
Sub Capitale (or
lower) neck cut with
distal support

27. Observe the difficulty in
removing a stem with distal
fixation.

28. Observe the
difficulty in
removing a
stem with
distal
fixation.

29. TYPE B CONSERVATIVE IMPLANTS
Excellent result but:
• When compared to conventional prosthesis
• Limited indications: ”you must have good
bone quality”
• In some types of prosthesis the level of
complications was embarissing.
• Often they don't have enough clinical history.

30. c
Horizontal neck cut
with metafisis 360°
contact.

31. De Puy PROXIMATM Hip
1991-2006
The story of a conservative implant created as a
result of the most recent biomecchanical
principals.
• PRESERVING BONE STOCK
• AVOID THIGH PAIN AND SOFT TISSUE PAIN
• LOWER THE PERCENTAGE OF
COMPLICATIONS
• HAVE LARGER INDICATIONS

32. THE LATERAL LOAD TRANSFER
DYNAMIC BIOMECHANICS OF FEMORAL
STRESS TRANSFER
• One must consider also the involvment of
muscles. In particolar ileo-tibial band exerts
compression forces on the lateral cortex.
• The classic model of Koch is not adeguate as
it didn't take into account muscle action and
so predicted compression forces only on the
medial femor. ITB
• The ideal prosthesis should transmit forces
laterally.
Fetto, J.F., Bettinger P., Austin K., Re-examination of Hip
Biomechanics During Unilateral Stance.
Am J Orthop., 605-612, August 1995

33. FORCE TRANSFER ON THE LATERAL FLARE
Walker PS et al, Hip International, 1999

34. WHY NO STEM?
• The biomecchanics show that
in a prosthesis with a lateral
flare the forces are only
applied proximally.
• The stem is therefore not
X
Contact Stress
(MPa)
necessary for stability
X
Walker PS et al., Hip International, 1999

35. PRESERVATION OF THE NECK
The preservation of the femoral neck increases the resistence of
the implant to rotational forces - because the neck becomes
more rectangular shaped proximally
Torsional load (Nm)
60
50
40
30
`
20
10 Proxima
0
0% 15% 50% 100%
Neck preservation
Pipino 1983 ,Freeman 1986
Whiteside et al, Am J Orthop, 1995

36. CONSERVATION OF THE FEMORAL NECK

37. PROXIMAL CONTACT AREA
44 cm²
DePuy Proxima size 3
39cm² 18cm² 39 cm²
Stryker Accolade TMZF,
S&N: Synergy Stem Stryker Osteonics Omnifit, size 4
size 14(roughtest area) size 4

38. PROXIMA DOESN'T DAMAGE TENDON INSERTION POINTS

39. CLINICAL EXPERIENCE
1995-2004
140 PROXIMA custom-made
type1
• Conservative neck recsection
• Forces distributed to the
lateral cortex type 2
(circumferential loading)
• Stem-less
2005-2008
260 PROXIMA std.

40. PROXIMA CUSTOM-MADE PROSTHESIS
(1995)
System Design – Implant Features
• Titanium (Ti-6Al-4V)
• Short stem
(metaphyseal loading)
• Ha coating
• Lateral flare
• Conservative neck
resection
• Contact with load
bearing cancellous bone
(M, L, A, P)

41. PROXIMA CUSTOM-MADE TYPE 1
7Y 8Y

42. STRESS SHIELDING
ESKA
CFP
MAYO

43. PROXIMA CUSTOM-MADE TYPE 2 - 1999
12 y 7y
type1 type2

44. TYPICAL CASES

45. FINITE ELEMENT ANALYSIS
OBJECTIVE
Examine the effects of a lateral flare on the
stability of a short stem with metafisis loading
CONCLUSIONS
• In a prosthesis with a lateral flare a distal
stem does not improve primary stability
• No difference in stability between a large and
small lateral flare
• A High Friction porous coating auments the
prothesis' stability.
Dep Bioeng University Southampton G.B.

46. After 2,5y After 6,5y

49. INDICATIONS
ARTHRITIS

50. INDICATIONS
AVN

51. INDICATIONS
OSTEOPOROUS

52. OSTEOPOROUS
Reumatoid arthritis
61y

53. BONE CHANGES IN OSTEOPOROSIS
Bone remodeling modifies bone structure

54. Age-related changes in bone geometry make a
correct fit and fill more difficult
Seeman. Lancet 2002; 359: 1841-50
Seeman. N Engl J Med. 2003; 349:320-3

55. OSTEOPOROUS
84 y

56. 81 y

57. 91y
After 18 m

58. PROXIMATM Hip
HOW HAVE MY INDICATIONS CHANGED
CEMENTED NON-CEMENTED
PROSTHESIS PROSTHESIS
2004 45,4% 54,6%
2007 9,4 % 90,6%

59. 84 y

60. SERIOUS OSTEOPOROSUS
• CEMENTED PROSTHESIS

61. UNUSUAL INDICATIONS

62. UNUSUAL INDICATIONS

63. UNUSUAL INDICATIONS

64. UNUSUAL INDICATIONS

65. UNUSUAL INDICATIONS

66. UNUSUAL INDICATIONS
75 y
Furlong 9 y
TKR same side
CVD

67. CONTRO-INDICATIONS
• Excessive antiversion o valgus
femoral neck
• Serious Osteoporosus
• Metafisis Osteosclerosus

68. RESULTS
International Experience
4748 implantations (up to June 08)
27 revisions (8 – trial, 19 – markets)
0.59% revision rate
In all cases, revisins were performed with primary or
conservative prosthesis
personal update
402 implantations (1995-2008)
0 revisions

69. Complications with traditional prosthesis

70. INTRAOPERATORY FRACTURES EARLY LOOSENING
After 2 m

71. Complications with Proxima
1mo
2y

72. MIGRATION
After 7y

73. SUBSIDENCE INTO VARUS

74. SUBSIDENCE INTO VARUS

75. SUBSIDENCE INTO VARUS
-THIGH PAIN

76. SUBSIDENCE INTO VARUS
+ HIGH OFF-SET + LONG HEAD OFFSET
LOOSENING

77. IS PROXIMA INVASIVE?
74 y
TIGH PAIN
-STRESS SHIELDING

78. IS PROXIMA INVASIVE?
TIGH PAIN
STRESS SHIELDING

79. After 2,5y After 6,5y

80. De Puy PROXIMATM Hip
CONCLUSIONS
WHAT IS THE DIFFERENCE

81. De Puy PROXIMATM Hip
CONCLUSIONS
ANATOMICA CIRCUMFERENZIAL DISTRIBUTION OF
IMPLANT STRESSES

82. CONSERVATIVE PROSTHESIS
CONCLUSIONS
The other conservative solutions (resurfacing or
normal neck preserving prosthesis) have
normally restricted indications, both because
they are not appropriate for a non-normal
femoral morphology and because they have a
need of good bone quality.
• For some of these implants the number of
complications is very high
• Often times they don't have a long follow-up

83. De Puy PROXIMATM Hip
CONCLUSIONS
PROXIMA, after a short learning curve may be used with the
same indications as a normal non-cemented prosthesis.
• Wide indications
• Improvement of the Peri-Prosthetic
bone quality
• Low percentage of complications

84. De Puy PROXIMATM Hip
CONCLUSIONS
THE SURGICAL TECHNIQUE IS NOT
DIFFICULT...IT'S JUST DIFFERENT
Can be used with any type of surgical access

85. De Puy PROXIMATM Hip
CONCLUSIONS
13 YEARS OF CLINICAL EXPERIENCE

86. GRAZIE