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Corato

  1. 1. Proxima Francesco Saverio Santori, Nicola Santori Orthopaedics & Traumatology Hospital S. Pietro Fatebenefratelli - Rome - Italy
  2. 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. 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. 4. STRESS SHIELDING Proximal load transfer is never gauranteed with a traditional stemmed implant
  5. 5. DIAPHESEAL FIXATION stress shielding !!!!!
  6. 6. THIGH PAIN
  7. 7. DAMAGE TO TENDON INSERTION POINTS
  8. 8. LOOSENING
  9. 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. 10. CONSERVE BONE STOCK The next operation! CONSERVATIVE PHILOSPHY
  11. 11. Conservative implants CONSERVATION OF THE FEMORAL NECK ? RESURFACING
  12. 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. 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. 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. 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. 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. 17. CONSERVATION OF THE NECK 1938
  18. 18. NECK SPARING PROSTHESIS SILENT ESKA PROXIMA CFP FRIENDLY S
  19. 19. NECK SPARING PROSTHESIS NANOS TWO STEP METHA MODULUS MAYO
  20. 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. 21. a Conserve all of the neck
  22. 22. a Conserve all of the neck SILENT TWO STEP
  23. 23. a Conserve all of the neck Failed conservative prosthesis can be replaced using a primary prosthesis
  24. 24. b Sub Capitale (or lower) neck cut with distal support
  25. 25. CFP MAYO ESKA METHA b Sub Capitale (or lower) neck cut with distal support NANOS MODULUS
  26. 26. b Sub Capitale (or lower) neck cut with distal support
  27. 27. Observe the difficulty in removing a stem with distal fixation.
  28. 28. Observe the difficulty in removing a stem with distal fixation.
  29. 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. 30. c Horizontal neck cut with metafisis 360° contact.
  31. 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. 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. 33. FORCE TRANSFER ON THE LATERAL FLARE Walker PS et al, Hip International, 1999
  34. 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. 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. 36. CONSERVATION OF THE FEMORAL NECK
  37. 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. 38. PROXIMA DOESN'T DAMAGE TENDON INSERTION POINTS
  39. 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. 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. 41. PROXIMA CUSTOM-MADE TYPE 1 7Y 8Y
  42. 42. STRESS SHIELDING ESKA CFP MAYO
  43. 43. PROXIMA CUSTOM-MADE TYPE 2 - 1999 12 y 7y type1 type2
  44. 44. TYPICAL CASES
  45. 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. 46. After 2,5y After 6,5y
  47. 47. INDICATIONS ARTHRITIS
  48. 48. INDICATIONS AVN
  49. 49. INDICATIONS OSTEOPOROUS
  50. 50. OSTEOPOROUS Reumatoid arthritis 61y
  51. 51. BONE CHANGES IN OSTEOPOROSIS Bone remodeling modifies bone structure
  52. 52. 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
  53. 53. OSTEOPOROUS 84 y
  54. 54. 81 y
  55. 55. 91y After 18 m
  56. 56. PROXIMATM Hip HOW HAVE MY INDICATIONS CHANGED CEMENTED NON-CEMENTED PROSTHESIS PROSTHESIS 2004 45,4% 54,6% 2007 9,4 % 90,6%
  57. 57. 84 y
  58. 58. SERIOUS OSTEOPOROSUS • CEMENTED PROSTHESIS
  59. 59. UNUSUAL INDICATIONS
  60. 60. UNUSUAL INDICATIONS
  61. 61. UNUSUAL INDICATIONS
  62. 62. UNUSUAL INDICATIONS
  63. 63. UNUSUAL INDICATIONS
  64. 64. UNUSUAL INDICATIONS 75 y Furlong 9 y TKR same side CVD
  65. 65. CONTRO-INDICATIONS • Excessive antiversion o valgus femoral neck • Serious Osteoporosus • Metafisis Osteosclerosus
  66. 66. 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
  67. 67. Complications with traditional prosthesis
  68. 68. INTRAOPERATORY FRACTURES EARLY LOOSENING After 2 m
  69. 69. Complications with Proxima 1mo 2y
  70. 70. MIGRATION After 7y
  71. 71. SUBSIDENCE INTO VARUS
  72. 72. SUBSIDENCE INTO VARUS
  73. 73. SUBSIDENCE INTO VARUS -THIGH PAIN
  74. 74. SUBSIDENCE INTO VARUS + HIGH OFF-SET + LONG HEAD OFFSET LOOSENING
  75. 75. IS PROXIMA INVASIVE? 74 y TIGH PAIN -STRESS SHIELDING
  76. 76. IS PROXIMA INVASIVE? TIGH PAIN STRESS SHIELDING
  77. 77. After 2,5y After 6,5y
  78. 78. De Puy PROXIMATM Hip CONCLUSIONS WHAT IS THE DIFFERENCE
  79. 79. De Puy PROXIMATM Hip CONCLUSIONS ANATOMICA CIRCUMFERENZIAL DISTRIBUTION OF IMPLANT STRESSES
  80. 80. 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
  81. 81. 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
  82. 82. De Puy PROXIMATM Hip CONCLUSIONS THE SURGICAL TECHNIQUE IS NOT DIFFICULT...IT'S JUST DIFFERENT Can be used with any type of surgical access
  83. 83. De Puy PROXIMATM Hip CONCLUSIONS 13 YEARS OF CLINICAL EXPERIENCE
  84. 84. GRAZIE

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