Im nail

Im nail

1. Intra- Medullary Nailing Ponnilavan

2. Evolution of intramedullary nailing Effect of reaming on IM nailing Biomechanics of IM nailing

3. Evolution of intramedullary nailing

4. Now in fourth generation of nails, rapid growth and driving force??? Driving forces: Radiographic imaging Biomaterial design Computer assisted manufacturing Realizing the importance of early mobilization of patient

5. IM nailing has evolved over past 75 years Past 33 years IM nailing of femur has become gold standard

6. Evolution of intramedullary nailing 1 st written record from 15 th century from interaction from Spanish and Aztecs Aztecs used wooden sticks for pseudoarthrosis In 1800s Heine used ivory for IM pining 1886 Bircher used same(Ivory) in German Gluck attempted IM osseous implants in late 1800s

7. Lejahrs introduced concept of longer devices for stability Ambotte in Belgium introduced metalic IM pins Hey groves(England) made and surgically implanted solid metal and hollow metal implants These were isolated cases without adoption by medical community

8. Smith-Petersen(1925): Used nail with 3 flanges for hip fractures Open reduction and nailing- widely accepted 1 st concepts of biocompatible material Used intra-op radiographic control Johansen added cannulation for guide wire

9. Smith-Petersen Nail

10. Gerhardt Kuntscher: Father of IM nailing Developed concepts and principles- foundation for 1 st gen nails Explained principles of stable canal filling IM constructs Reported experimental evidence for biological effects of marrow filling Believed optimal fracture healing would happened only with stable nail construct

11. Gerhardt Kuntscher contd …. Described 3 construct options: Pins: controls alignment only Canal filling rod: Controls alignment and translation Nail: Controls alignment, translation, rotation and length

12. Initially used “ V” shaped without reaming Later(1950s) used reaming to use larger nails- increase strength Cloverleaf femoral nails were larger (16-18mm for men & 16mm for women) in 1970s Gerhardt Kuntscher contd ….

13. Kuntscher Cloverleaf Nail

14. Stiff proportional to strength of nail/construct If too stiff, could break bone  unstable construct If too small, flexible unstable  non-union

15. In 1 st multicenter after WWII study Smith stated: Given the proper indications, IM fixation is the most effective form of therapy for many fractures of the shaft of the femur That statement was then modified: This technique, if applied to improperly selected cases, or if ineffectively or unskillfully carried out, offers more possibilities of trouble than any other  so the English, Americans & Australians rejected it

16. 1947 – 1977- left nailing in disregard 3 major obstacles to adoption of nailing in north America: Conflicting bone healing theories Material, manufacturing & surgical technique errors Lack of radiographic image intensifying device and techniques

17. Theories of bone healing Evolved in 1700-1800s Alberct Haller’s believed than bone was deposited in response to injury From vascular regeneration around the injury zone as a deposition of salts Duhamel(France) described importance of periosteal soft tissue & cambium layer John Godsir (England) described the osteoblasts , belived osteoblast as primary origin of repair

18. Current concept/view: Combination of these 2 school of thoughts Callus is complex repair mechanism incorporating: Vascular proliferation Cell differentiation Mechanical factor role Stem cell migration & molecular modulation Theories of bone healing cotd ……

19. United states and England after WWII were behind Germans in material fabrication and radiographic imaging Implant failure cases due to lack of: Uniform manufacturing Medical grade materials Unavailability of fluoroscopic imaging Due to lack of imaging techniques US & UK opted for open nailing

20. US & UK justification for open nailing: Osteoblast as primary organ of repair Avoid complication of fat embolism

21. Next step in 1 st gen nail Kuntscher’s “V” shape was modified to cloverleaf shape He believed - would compress on insertion Later he admitted - incorrect hypothesis In late 1970s and early 1980s accepted Kunscher’s work in US Was pioneered by Harborview group and subsequent article was published by Winquist in 1984 Finally imported Image intensifier

22. Second generation nailing

23. Second generation nailing Use of bicortical screws proximal & distal to fracture Controls length and rotation In 1972 Klemm & Schellam introduced 1 st commercially available interlocking nail Used cloverleaf design with interlocking screws with permission of Kunscher Ended in high rate of implant failure due to rotational instability(due open section design)

24. 1 st commercial interlocking nail

25. Difficulty of placing locking screws focused on design of implants and instruments Kempf et al introduced semi-closed nail with proximal cylinder and distal targeting device for placing locking screws Used both static and dynamic lock based on surgeons preference Second generation nailing Contd…….

26. Semi-closed nail with proximal cylinder and distal targeting device for placing locking screws Used in US with excellent results in 1980s surpassed closed reduction 10% malunion rate These patients were treated with non-weight bearing

27. Closed section nail Different approach evolved in Memphis with goal of immediate weight bearing Static construct to avoid mal-union To enhance stability(rotational) & increase fatigue life Resulted in fragmentation of bone from hoop stress during insertion Rheinlander believed closed section nail is not in favor as it caused more damage to endosteal vascularity Second generation nailing Contd…….

28. Russel and Taylor contribution Conceptualized closed section nail by designing bending stiffness less than intact femur with 50% rotational stability to maximized fatigue failure introduced 1 st closed section IL nails, reported clinical results in 1986 Brumback in 1988 reported 99% union rate with no malunion with static lock, 1% implant failure Second generation nailing Contd…….

29. Between 1980 & 1985 closed reduction and traction for femur fracture was replaced by Interlocking nails: With early mobilization Less hospital stay Russel -Taylor designed smaller stronger nails to allow less reaming for bone conservation Standard sized(for femur) became 10-12mm Second generation nailing Contd…….

30. Cephalomedullary nail developed by Kuntscher for proximal femur fractures Replaced plating for subtrochanteric fractures Retrograde nailing: Introduced by Seligson , Green & Henry for supracondylar fractures Now extended use for shaft of femur Second generation nailing Contd…….

31. In 1990s issues of endosteal vascularity disturbance reconsidered advantages of reaming But unreamed nailing did not attain adequate stability with lower union rates Then issue of pulmonary complications of reaming lead to reevaluation of reamer head design Second generation nailing Contd…….

32. Third generation nailing

33. Third generation nailing From 1998 to 2008 resulted from analysis of failures of 2 nd gen nails Involved material and structural change Surgeons also expanded indication for metaphyseal fractures: Inadequate stabilization High screw breakage rates with 2 nd gen

34. Titanium alloys screws used- more fatigue resistant IL screws fail by axial loading Can be reduced by multiaxial screw placement- more stable Krettek et al. improved nail stability by introducing pollar screws, initially for tibia This additional blocking screws ensured translational and angular stability Third generation nailing Contd……

35. In 1990s entry portal errors and malalignment were problems Russell et al documented decreased rate of malunion of proximal femur with minimally invasive technique for entry portal Piriformis or trochanteric entry was dependent on nail design Reduction of fractures evolved through flexible wires and extensive imaging Third generation nailing Contd……

36. Fracture table or with minimal manipulation is institution dependent- both are equally effective Manual traction: Reduced operating time But required more skilled assistants Traction table: Widespread used In retrograde nailing cannot be used Third generation nailing Contd……

37. Supine nailing or lateral position: Supine is commonly performed Lateral has advantages for performing intramedullary osteotomies Third generation nailing Contd……

38. Fourth generation nailing Combination of all 3 generations With options to address infections, telemetry to ascertain status of bone regeneration and mechanical reconstitution Newer techniques: Surface engineering with active or passive coupling of antibiotics Non-iodizing sensor technology for screw placement Sensors to change in pH around nail Load stress telemetry to asses stiffness progression at fracture site

39. Recent advancement Motorized Intramedullary nail for management of limb length discrepancy Uses reliable-remote controlled mechanisms for distraction osteogenesis Provide reliable fragment stabilization

40. Motorized Intramedullary nail Contd… Accurate control of rate and rhythm of distraction Used magnetic and electrical remote control to distract Outcomes are promising Patient selection is crucial

41. Schneider nail Hansen-Street nail

42. Sampson fluted nail Kuntschner nail

43. Rush nail Ender nail

44. Modny nail Halloran nail

45. Huckstep nail AO universal nail

46. Grosse & Kempf nail Russel -Taylor nail

47. Principle Extends from one end to other through medullary canal acting as splint Allows axial forces to be transmitted to opposing ends of fragments and prevents angulation , translation and to some extent rotatory movements Contact between nail and bone exits between entry point, marrow and at the cancellous epiphysis region of opposite side

48. Good cortical contact Bone shares load Stable

49. Bend/break No Cortical Contact Stress on Interlocking(IL) screws Four point stress on screws Nail transmits load

50. Four point stress on IL screws

51. Effect of nailing on vascularity & bone Vascular supply of bone: Inner 2/3 rd - endosteal supply Outer 1/3 rd - periosteal supply Fracture Necrosis of 50-70% of cortex near # Nailing Further affected

52. Reaming Endosteal supply regenerates around nail (proportional to space around nail) Periosteal supply traverses into endosteum Marrow infiltration into marrow supply Damage to endosteal supply Attempt to increase endosteal vascularity Necrosis Fat embolism

53. Unreamed R eamed

54. Reaming and vascularity Revascularization starts from periosteal side Delayed by close/tight fitting nail Takes 12 weeks for regeneration Sometimes regeneration of nutrient artery may not occur for 6 months

55. Reaming on shape of medullary canal Hourglass shape Reaming Perfect cylinder Nail close/snugly fits

56. Reaming and pressure in medullar canal Heat and pressure are by–products of reaming Hydraulic builds up after reaming and far exceeds BP Increased by: Material in cavity like blood, clots, fat & bone pieces Low clearance head Reduced by: Removing material periodically Using hollow reamer Narrow shaft reamer

57. Reaming: Increases systemic inflammatory response(2 nd hit response) Should be gentle and slow

58. Thermal effect of reaming Heat- by-product Rise of temperature of 44.6 C had negative effect of healing on cell enzymes Threshold for Osteonecrosis is 47 C for 1 minute Increased by: Blunt reamer High speed High thrust

59. New reamer design

60. Reamer-Irrigator-Aspirator(RIA) Developed to: Reduce fat embolism Thermal necrosis RIA System: Shaft with continuous irrigation and aspiration system with closed suction bag Reaming material collected is an ideal autograft

61. Reamer-Irrigator-Aspirator(RIA)

62. Bone healing after nailing Snug/tight fitting nail Affects endosteal revascularization Delayed healing Thin/loose fitting nail Unstable construct Delayed/ Non-union Vs

63. Strength of fixation: Shape Diameter Area of nail in contact with bone Material Working length Fracture reduction

64. Shape: Nail with sharp corners/fluted edges resists torsional forces Slot does not reduce bending stiffness/but reduces torsional stiffness

65. Nail diameter More important factor in determining nail strength Nail with diameter of 12 mm and thickness of 2mm has bending stiffness equal to intact femur 16mm nail is: 1.5 times stiff as 14mm nail 2.5 times stiff as 12mm nail

66. Curves Straight, curved or helical Long bone has curved medullary canal Nails- accommodate curvatures Straight nail insertion- stress and may rupture bone

67. Curves Cotd …. Maximum axial force at 3/4 th of insertion Axial insertion produces hoop stress May split cortex Over reaming by 0.5-1mm makes insertion easier and reduces hoop stress

68. Nail length and working length Total nail length Length of nail-bone contact Working length

69. Nail length Larger contact area- higher resistant to motion Longer nail Protrude into joint Limit ROM Shorter nail Inadequate fixation

70. Working length Length of nail spanning the fracture from its distal point of fixation in proximal fragment to proximal point of fixation in distal fragment Distance between two points on either side of fracture where the bone firmly grips nail Thus it is the unsuported portion of nail on either side of fracture

71. Working length and fixation Bending stiffness of nail is inversely proportional to square of its working length Torsional stiffness is inversely proportional to its working length Shorter working length means stronger fixation

72. Factors influencing working length Reaming Reduces working length Adds rotational/torsional stability Interlocking nailing Modify working length Gives greater torsional stability Increases stability

73. Ends of nail Slot for attachment of extraction hook Tapered for insertion Internally threaded core Holes for interlocking screws  mediolateral , anteroposterior and oblique holes

74. Inter-locking screws Weakest portion- shaft thread junction Partially threaded  purchase on one cortex backs out easily screw failure Fully threaded & threads at either ends has better hold on both the cortex Core diameter- determines strength Titanium screws improves strength

75. Inter-locking screws Thread at one end Fully threaded Thread at Both end Weakest portion

76. Multiple nails Several smaller diameter nails inserted Stability- 3 or 4 point fixation Gives more bending stiffness than torsional stiffness Surgical exposure is minimal

77. Vs Reamed nailing Improved nail bone contact Improved stability Increases use of larger nail Reduced chance of bone splinting Non-reamed nailing Preferable in Compound fractures Suitable for tibia, humerus and forearm

78. Safe Practices in reaming Don’t use torniquet Use ball-tipped guide wire Attention to sound and speed of reamer- if slowing and catching harbinger of jamming On jamming, withdraw with full power and re-advance Flexible reamer should be used only in forward direction Guide wire should be stabilized while reaming Follow 1 st pass of guide wire under C-Arm Ream with increments of 0.5mm Overream with 2mm Remove reamer and clean bone debris frequently Use high-torque, low-rpm power source

79. More flexible(torsion > bending) Can tolerate variable insertion points May have difficult in placing IL screws Less flexible (bending > rotation) Need precise insertion point Risk of bone splinting Rigidity of Thicker walled slotted nail = Rigidity of thinner walled non-slotted nail Vs Slotted Nail Non-Slotted Nail

80. Slotted Nail Non-Slotted Nail

81. Used in simple/Stable/minimally /comminuted #s Does not offer torsional stability Can be used only in selected cases Needs approximation of cortex In highly comminuted /Segmenta l /Spiral/ unstable #s Offers torsional stability Popular implant in diaphyseal #s, mainly lower limb #s Full opposition is not necessary Vs Standard Non-Locking Nail Interlocking Nail

82. IL screws at either end of nail Offer better torsional stability Length is maintained by IL Screws In highly comminuted /Segmental /Spiral/ unstable #s Full opposition is not necessary IL Screw only at one end  placed in oval hole  Permits telescopic movements Torsional stability depends mainly on nail-bone interface Length is maintained by nail-bone contact Used in simple/Stable/minimally /comminuted #s Needs atleas 50% of cortical contact Vs Static Locking Dynamic locking

83. Static Locking Dynamic locking

84. Polar Screw and biomechanics Pollar (German) or Bollard(English) is strong post made of strong metal/ conrete /wood to prevent cars entering part of road for parking Blocking(pollar/Bollard Srews ) were introduced to route an unreamed nail into distal or proximal fragments But now used to centre a guide wire/reamer/Nail by narrowing medullary canal

85. Intra-Op Post-Op

86. Placing a polar screw Drill bit, screws, locking bolt can be used While placing it should leave adequate space for medullary devices Chance of reamer jamming against pollar screws  better to ream under C-Arm guidance Increased primary stability of metaphyseal #s Effective in preventing malalignment and stability

87. Distal Locking Screws Resists axial and torsional loading Stress on screws is very high in unreamed cases Two distal screws should be used if distal fragment is less than 60% of distance between mid-shaft and knee joint line Prevents toggling

88. Amount of toggling proportional to: Length of distal fragment Number of distal screws Postion of screws Distal Locking Screws Contd…..

89. Four point stress of distal locking screws

90. Stress on distal femoral locking screw Closer the fracture to screw L ess cortical contact of nail Increased stress

91. Stress on distal femoral locking screw Increased four point stress Increased width of femoral condyles Increased unsupported portion of screw

92. Antibiotic impregnated IM Nail(AIIN) PMMA(Bone Cement) elute antibiotics coated nail Its heat stable, good elution property and few harmful effects on bone healing Ideal AIIN: Heat stable Inert Smooth surfaced

93. Dynamization Indicated- risk of non-union Removing static screw from long segment, maintaining adequate control over short segment Removing from short segment/premature removing: Shortening Instability Non-union

94. Open Nailing Fracture site opened Fracture biological environment disturbed Hematoma removed/disturbed Soft tissue damage-periosteal vascularity disturbed Chance of infection- 6 times Vs Closed nailing Chance of Non-Union- 10 times Vs Closed nailing

95. Thank You