Principles of internal fixation

By Dr Praveen Kumar Reddy Gorantla

1. PRINCIPLES OF INTERNAL FIXATION By Dr Praveen

2. Principles (AO) 1 . Anatomical reduction 2 . Stable internal fixation 3 . Preservation of the blood supply 4 . Early active pain-free mobilisatio n

3. Historical Background Preoperative Planning Fracture Reduction Techniques and Devices for Internal Fixation

4. Historical Background First reports on modern techniques of internal fixation are only about 100 years old. Elie and Albin Lambotte “ osteosynthesis ” of fractures with plates and screws, wire loops and external fixators

5. B rothers Elie and Albin Lambotte (1866-1955) Osteosynthesis Anatomical reduction and stable fixation of I/A #

6. Robert Danis ( 1880 to 1962) introduced the term of soudure autogéne

7. Maurice Müller was impressed by DANIS &founded the Arbeitsgemeinschaft für Osteosynthesefragen (AO ) 1958

8. Gerhard Küntscher (1900 to 1972) in Germany had developed the technique of IM nailing

9. GOAL OF OPERATIVE FRACTURE FIXATION Full restoration of function Faster return to his preinjury status Minimize the risk and incidence of complications. Predictable alignment of fracture fragments

10. The purpose of implants to provide a temporary support to maintain alignment during the fracture healing to allow for a functional rehabilitation

11. fractured bone needs - a certain degree of immobilizatio n -optimally preserved blood supply - biologic or hormonal stimuli

12. Soft Tissue Injury and Fracture Healing “ every fracture is a soft tissue injury , where the bone happens to be broken ,” The more extensive the zone of injury and the tissue destruction, the higher is the risk for a delay of the healing process or for other complications

13. High Rate of Healing Spectrum of Healing Absolute Stability = 1 Bone Healing Relative Stability = 2 Bone Healing Biology of Bone Healing THE SIMPLE VERSION... Fibrous Matrix > Cartilage > Calcified Cartilage > Woven Bone > Lamellar Bone Haversian Remodeling Minimal Callus Callus

14. Functions of Fixation Interfragmentary Compression Lag Screw Plate Functions Neutralization Buttress Bridge Tension Band Compression Locking Intramedullary Nails Internal splint Bridge plate fixation Internal splint External fixation External splint Cast External splint *Not internal fixation

15. Indications for Internal Fixation Displaced intra-articular fracture Axial, angular, or rotational instability that cannot be controlled by closed methods Open fracture Polytrauma Associated neurovascular injury

16. The components of a preoperative plan • Timing of surgery • Surgical approach • Reduction maneuvers • Fixation construct • Intraoperative imaging • Wound closure/coverage • Postoperative care • Rehabilitation

17. Prophylactic Antibiotics In general a second generation cephalosporin with a broad spectrum is recommended, applied as single dose 30 minutes before the start of surgery or for a period of a maximum 24 to 48 hours postoperatively

18. Fracture Reduction The goal of reduction is to restore the anatomical relationship Direct reduction Indirect Reduction Closed reduction Open reduction

19. Reduction Forceps

20. joysticks

21. Collinear reduction clamp

22. Open Reduction Open reduction implies that the fracture site is exposed, allowing to watch and inspect the adequacy of reduction with our eyes.

23. The distractor

24. Internal fixation devices stabilize the bone From within the medullary canal ( intramedullary nails ) Fixed to the exterior of the bone ( conventional non locked screws and plates and locked plates as well as tension band wires).

25. Screws A screw is a powerful element that converts rotation into linear motion. They are typically named according to their design, function, or way of application. Design (partially or fully threaded, cannulated , self- tapping,etc .) Dimension of major thread diameter (most common used 1.5, 2, 2.4, 2.7, 3.5, 4.5, 6.5, 7.3 mm, etc.)

26. Area of typical application (cortex, cancellous bone, bicortical,or monocortical) Function (lag screw, locking head screw [LHS], position screw, etc.)

27. The two basic principles of a conventional screw are To compress a fracture plane (lag screw) To fix a plate to the bone (plate screw)

28. Cortical screws: Greater number of threads smaller pitch Outer thread diameter to core diameter ratio is less Better hold in cortical bone Usually fully threaded Size 1-4.5mm diameter Self tapping , cannulated etc Figure from: Rockwood and Green’s, 5 th ed.

29. Each size has a pair of drill bits corresponding to the screws major and minor diameter and a tap. The drill corresponding to the major diameter is used for drilling the gliding hole for a lag screw The drill corresponding to the minor diameter is used for drilling the threaded hole.

30. Cancellous screws : Larger thread to core diameter ratio pitch is greater Lag effect with partially- threaded screws Theoretically allows better fixation in cancellous bone indicated for meta-epiphyseal , cancellous bone Tapping is recommend to open the cortex and in dense bone of the young adult.

31. LHS The LHS have a head with a thread that engages with the reciprocal thread of the plate hole. a screw-plate device with angular stability variable angular stability , which allows angulating locking screws within the plate hole to address specific fracture configurations

32. Name Mechanism Example Nonlocked Plate screw Preload and friction is applied to create force between the plate and the bone Forearm plating Lag screw The glide hole allows compression between bone fragments Fixation of a butterfly or wedge fragment or medial malleolus fracture Position screw Holds anatomical parts in correct relation to each other without compression (i.e., thread hole only, no glide hole) Syndesmotic screw

33. Locking head screw threads in the screw head allow mechanical coupling to a reciprocal thread in the plate and provide angular stability Complex metaphyseal # Osteoporotic Variable locking screw Used exclusively with special locked plates; same mechanical angular stability as locking head screw, but allows some variability in screw angulation within the plate hole Complex comminuted metaphyseal fractures and periprosthetic fractures Interlocking screw Couples an intramedullary nail to the bone to maintain length, alignment, and rotation Interlocked femoral or tibial intramedullary nail

34. Anchor screw A point of fixation used to anchor a wire loop or strong suture Tension band anchor in a proximal humerus fracture Push–pull screw A temporary point of fixation used to reduce a fracture by distraction and/or compression Use of an articulated compression device Reduction screw Conventional screw used through a plate to pull fracture fragments toward the plate; the screw may be removed or exchanged once alignment is obtained MIPO technique to reduce multifragmentary fracture onto the plate Poller screw Screw used as a fulcrum to redirect an intramedullary nail Proximal tibial fracture during IM nailing

35. Lag screw Can be applied independently or through a plate hole. Interfragmentary compression is the basic element responsible for absolute stability of fracture fixation.

36. The ideal direction of a lag screw , for generation of compressive force, is perpendicular to the fracture plane. As this is often not practical , an inclination halfway between the perpendiculars to the fracture and to the long axis of the bone is typically chosen

37. Positioning Screw *A fully threaded screw that joins two anatomical parts at a defined distance without compression . *The thread is therefore tapped in both cortices. *Example- Syndesmotic screw

38. Compression Plates Plate is pressed against the bone which produces preload and friction between the two surfaces. USES # forearm bones , simple metaphyseal # of long bones, malunion and nonunions ,

39. Early modern plates In 1967 the DCP designed by Perren Angle blade plates for the proximal and distal femur Tubular plates Reconstruction plates The sliding hip screw Dynamic condylarscrews LC-DCP LCP

40. THE FIVE FUNCTIONS OF PLATING • Neutralization or protection • Compression • Buttressing • Tension band function • Bridging

41. Neutralization Plates Neutralizes/protects lag screws from shear, bending, and torsional forces across fx “Protection Plate"

42. Compression plate Produces locking forces across a # site. Role of compression Compaction of # to force together interdigitating spicules space b/n bone fragments fracture stability Generate friction Absolute stability

43. Methods of achieving compression Self compressing plate(coverts torque to longitudinal force) Tensioning device Eccentric screw placement Lag screw

44. Dynamic compression principle

45. Axial compression with a plate can be obtained with the removable, articulated tension device

46. Verbrugg forceps used for tensioning

47. Lag screw placement through the plate Compression + rigidity obtained a with one construct Compression plate first Then lag screw placed through plate

48. In oblique fractures the plate must be fixed first to the fragment with an obtuse angle , so that when compression is added on the opposite side of the fracture the fragment locks in the axilla between the plate and the bone

49. The structure of a limited-contact dynamic compression plate. LC-DCP

50. In the dynamic compression plate (A), the area at the plate holes is less stiff than the area between them. During bending, the plate tends to bend only in the areas of the hole. The limited-contact dynamic compression plate (B) has an even stiffness without the risk of buckling at the screw holes.

51. Undercuts plate holes; undercut at each end of the plate hole allows 40 tilting of screws both ways along the long axis of the plate and 7 degrees tilting in transverse plane

52. Tension Band Plates Plate counteracts natural bending moment seen wih physiologic loading of bone Applied to tension side to prevent “gapping” Plate converts bending force to compression Examples: Proximal Femur & Olecranon

53. Buttress plate Strengthen a weakened cortex . Prevents bone from collapsing during healing . Usually with large surface area to facilitate wider distribution of the load. Plate must match contour of bone to truly provide buttress effect

54. To maintain bone length or support depressed fracture fragments. Commmonly used in fixing epiphyseal and metaphyseal fractures.

55. Order of fixation: Articular surface compressed with bone forceps and provisionally fixed with k-wires Bottom 3 cortical screws placed Provide buttress effect Top 2 partially-threaded cancellous screws placed Lag articular surface together Third screw placed either in lag or normal fashion since articular surface already compressed Buttress Concepts Figure from: Schatzker J, Tile M: The Rationale of Operative Fracture Care. Springer-Verlag, 1987.

56. Antiglide plate

57. Bridge Plates “Bridge”/bypass comminution Do not produce any compression Proximal & distal fixation Goal: Maintain length, rotation, & axial alignment Avoids soft tissue disruption at # = maintain # blood supply

58. Condylar plate Mainly used in Rx of I/A distal femoral fractures. Two mechanical functions Maintains reduction of manjor intra-articular fragments Rigidly fixes metaphyseal componets to diaphyseal shaft,permitting early movements of extremity. Functions both as neutralizatio and buttresssing plate It can also function as compression plate

59. Plate Pre-Bending Compression Forces opposite cortex into compression

60. Application of straight plate to curved bone

61. Effect of forces

62. Torsional stability

63. Counting number of engaged cortices

64. Longer plates reduce stress in the plate as well as to th screws

65. HOW MANY SCREWS ? Hands-on experience suggests that, in the humerus, screws grip seven cortices on each side of the fracture ; in the radius and the ulna, five; in the tibia, six, and in the femur, seven. Bones No. of Cortices No. of Holes Type of Plate Forearm 5 to 6 Cortex 6 holes Small 3.5 Humerus 7 to 8 Cortex 8 holes Narrow 4.5 Tibia 7 to 8 Cortex 7 holes Narrow 4.5 Femur 7 to 8 Cortex 8 holes Narrow 4.5 Clavicle 5 to 6 Cortex 6 holes` Small 3.5

66. HOW CLOSE TO THE FRACTURE SITE? A screw, as a result, should not be placed closer than one centimeter from the fracture line.

67. Classic example of inadequate fixation & stability Narrow, weak plate that is too short Insufficient cortices engaged with screws through plate Gaps left at the fx site Unavoidable result = Nonunion Failure to Apply Concepts

68. Reconstruction Plates Can be bent and twisted in two dimensions. Decrease stiffness than DCP. Should not be bent more than 15°. Used were the exact and complex contouring is required. eg . Pelvis, Distal Humerus , Clavicle.

69. Reconstruction plates are thicker than one third tubular plates but not quite as thick as dynamic compression plates . As with tubular plates, they have oval screw holes , allowing potential for limited compression .

70. One Third Tubular Plates Plates have the form of one third of the circumference of a cylinder. Low rigidity (1mm thick). Oval holes – Axial compression can be achieved. Uses – Lateral malleolus, distal ulna, metatarsals.

71. limited stability . The thin design allows for easy shaping and is primarily used on the lateral malleolus and distal ulna. The oval holes allow for limited fracture compression with eccentric screw placement.

72. LOCKING PLATES The force transfer in the internal fixator principle occurs primarily through the locking head screws (LHS) across the plate and fracture

73. Angular stability of the construct Improved construct stability in osteopenic bone Resistance to secondary collapse or screw displacement

74. Screw head has threads that lock into threaded hole in the plate Creates a “ fixed angle ” at each hole Theoretically eliminates individual screw failure Plate-bone contact not critical Courtesy AO Archives

75. Increased axial stability It is much less likely that an individual screw will fail But, plates can still break Indications: Osteopenic bone Metaphyseal fractures with short articular block Bridge plating

76. Screw : Conical screw head Large core diameter. Self tapping. Star drive recess.

77. 1 st reduced the # as anatomical as possible Cortical screw should be used 1 st in a fracture fragment. If locking screw is used first avoid spinning of plates. Unicortical screws causes no loss of stability

78. Osteoporotic bones bicortical screws should be used. In the comminuted # screw holes close to the fracture should be used to reduce stain. In the fracture with small or no gap the immediate screw holes should be left unfilled to reduced the strain

79. Indications : 1. Osteoporotic # 2. Periprosthetic # 3. Multifragmentry # Delayed change from external fixation to internal fixation. Advantages : 1. Angular stability 2. Axial stability 3. Plate contouring not required 4. Less damage to the blood supply of bone. 5. Decrease infection because of submuscular technique 6. Less soft tissue damage.

80. Plate screw density and fracture plate quotient

81. Plate length and No. of Screws Plate span ratio Plate length # length Comminuted # - 2-3 Simple # - 8-10 Plate Screw density No. of Screws No. of Plate holes Simple #-0.3-0.4 Comminuted # 0.4-0.5 - At least 4 cortices per main fragment for comminuted fracture - At least 3 cortices per main fragment for simple fracture.

82. Timing of Plate Removal, Recommendations for removal of plates in the lower limb : Malleolar fractures-8-12 The tibial pilon - 12-18 The tibial shaft-12-18 The proximal tibia -12-18 Shaft of radius / ulna-24-28 Distal radius 8-12 Metacarpals 4-6

83. The femoral condyles-12-24 The femoral shaft: Single plate, Double Plate-24-36 From month 18, in 2 steps ( Interval 06 months) Pertrochanteric and femoral neck fractures Upper extremity-12-18

84. Combi plates Hybrid plating with a combination of conventional nonlocked screws and locked screws lag first, lock second

85. INTRAMEDULLARY NAILING Load sharing device Axial and rotational stability Maintains the length Biological fixation Minimal soft tissue exposure Early weight bearing

86. Intramedullary Nailing : The principle of fixation is based on the compression between the bone and the nail. Interlocking Intramedullary Nail : Nail have the proximal and distal screw holes. Nail is locked by the interlocking screws. The resistance to the torsial and axial force depend on the screw bone interface. Working Length : Distance between the proximal and distal interlocking screws.

87. Dyanamization : Interlocking Nails can be locked in dynamic or static mode. Dyanamization means placing the screw at only one end of the bone. Static Locking means placing the screw at the both ends of the bone. Dynamization can be done at the 8-12 weeks for delayed union. Screw is removed from the longer fragment.

88. TYPES OF INTRAMEDULLARY NAILS : Centromedullary nails Condylocephalic nails Cephalomedullary nails

89. Blk screws. Working Length

90. Intramedullary Fixation Generally utilizes closed/indirect or minimally open reduction techniques Greater preservation of soft tissues as compared to ORIF IM reaming has been shown to stimulate fracture healing Expanded indications i.e. Reamed IM nail is acceptable in many open fractures

91. Intramedullary Fixation Rotational and axial stability provided by interlocking bolts Reduction can be technically difficult in segmental and comminuted fractures Difficult to Maintain reduction of fractures in close proximity to metaphyseal flare

92. Open segmental tibia fracture treated with a reamed, locked IM Nail. Note the use of multiple proximal interlocks where angular control is more difficult to maintain due to the metaphyseal flare.

93. Intertrochanteric/ Subtrochanteric fracture treated with closed IM Nail The goal: Restore length, alignment, and rotation NOT anatomic reduction Without extensive exposure this fracture formed abundant callus by 6 weeks Valgus is restored...

94. Percutaneous Plating Plating through modified incisions Indirect reduction techniques Limited incision for: Passing and positioning the plate Individual screw placement Soft tissue “friendly”

95. DYNAMIC HIP SCREW & DYNAMIC CONDYLAR SCREW The dynamic hip screw (DHS) implant system has been designed primarily for the fixation of trochanteric fractures . It may also be used for certain subtrochanteric fractures as well as for selected basi -cervical femoral fractures. The implant is based on the sliding nail principle which allows impaction of the fracture. This is made possible by the insertion of a wide diameter screw into the femoral head . A side plate, which has barrel at a fixed angle is slid over the screw and fixed to the femoral shaft.

96. DHS : Length of measurements : Length measured 105 mm Reamer setting 95 mm Tapping depth 95 mm DHS/DCS Screw length 95 mm

97. Should be less than 28mm

98. CCS Fixation in Fracture Neck Femur : - Parallel 6.5mm CCS are used in triangular or inverted triangular configuration .

99. Tension Band Wiring wire absorbs tensile forces, the bone withstands the compressive forces

100. Wire must be applied on tension surface of bone. Wire must be prestressed (tightened) Wire must be strong enough to withstand tension load. Strong opposite bone cortex must be present. Joint movement must be encouraged to improve congruity and compression

101. Biomechanics – Pauwels 1935

102. Biomechanics

103. Biomechanics

104. Biomechanics The cortex from the TBW must be strong enough to bear the applied compressive loads

105. Biomechanics The implant alone does not provide stability. In combination with antagonistic deforming muscles, it can help produce uniform compression at the fracture site. It guides the compression force .

106. Biomechanics Tension Band Wiring is a device, which convert distraction forces of extensors acting on the fracture line into compressive forces

107. Bilateral cable ension band operation

108. Treatment options for comminuted patella fractures

109. Comminuted fracture –circlage wire and K wire fixation

110. Cerclage wiring Long spiral or oblique #. Obtain reduction. Place wires perpendicular to long axis of bone. Adequately spaced multiple wire loops. Contour wires around bone. Tension and tighten.

111. Always Use strong wire Use two or more wires Use wire tightener –twister Apply equal tension on all wires Twist in same direction Support # with addition means(never sole means of # stabilization)

112. Thankyou