Plates and screws 11

easy for orthopedic resident to understand

1. Plates and Screws Supervised by Dr. Marwan Abuhashem By Dr. Ismael Al- jabiri Al- Bashir Orthopedic Department Ministry Of Health Jordan

2. 1 . Anatomical Reduction. 2. Stable internal fixation. 3. Preservation of Blood supply 4. Early mobilization. Principles of Fixation :

3. 3 “ Surfaces of the fracture do not displace under functional load” Can only be achieved by interfragmentary compression Absolute stability A plate by itself rarely provides absolute stability The key tool of absolute stability is the lag screw Compression must sufficiently neutralize all forces[bending, tension, shear and rotation]

4. Relative Stability:  A fixation device that allows small amounts of motion in proportion to the load applied. The deformation or displacement is inversely proportional to the stiffness of the implant. Examples: Intramedullary rod, bridge plating, external fixation.

5. PLATES Introduction : Bone plates are like internal splints holding together the fractured ends of a bone. A bone plate has two mechanical functions . It transmits forces from one end of a bone to the other, bypassing and thus protecting the area of fractures. It also holds the fracture ends together while maintaining the proper alignment of the fragments throughout the healing process.

6. History Hansman’s Bone Plate (1886) Hansmann’s plates were: Bent at the end to protude through the skin Attched to bone by screw with long shanks that projected outside the soft tissues.

7. Bone Suture Stabilization Inserts (Koenig, 1905)

8. History Since 1958, AO has devised a family of plates for long bone fractures, starting with a round holed plate. In 1969 the Dynamic Compression Plate was developed. In 1994 LC DCP was created. In 2011 LCP with combination holes has come into use.

9. Names of plates. Shape (Semitubular, 1/3 rd tubular) Width of plate (Small, Narrow, Broad) Shape of screw holes. (Round, Oval) Surface contact characteristics. (LC, PC) Intended site of application (Condylar Plate) According to the function

10. Standard Plates Narrow DCP-4.5 mm Broad DCP – 4.5 mm 3.5 mm DCP

11. LC-DCP 3.5 & 4.5mm Reconstruction plate 3.5 & 4.5mm

12. 1/3 tubular plate 2.7, 3.5 & 4.5 mm

13. Special Plates T Plates T&L Buttress plates

14. Lateral proximal Tibial buttress plates Condylar buttress plate Narrow lengthening plates

15. Broad Lengthening plate Spoon plate Clover leaf plate

16. DCP - 3.5 and 4.5 First introduced in 1969 by Danis Revolutionary concept of compression plating Featured a new hole designed for axial compression Broad 4.5 for Femur & Narrow 4.5 for Humerus & Tibia DCP 3.5 for Forearm, Fibula, Pelvis & Clavicle

17. Advantage of DCP : 1. Inclined insertion 25°longitudinal and 7° sideways 2. Placement of a screw in neutral position without the danger of distraction of fragments 3. Insertion of a lag screw for the compression 4. Usage of two lag screws in the main fragments for axial compression 5. Compression of several fragments individually in comminuted fractures 6. Application as a buttress plate in articular area

18. Problems with DCP Unstable fixation leads to fatigue & failure Strict adherence to principles of compression Compromised blood supply due to intimate contact with underlying cortex “Refractures” after plate removal

19. LC-DCP Represents a design change Overcome problems with DCP Plate footprint reduced Minimized kinking at screw holes, more countourable , reduced plate fatigue at hole Allows more inclination of screw in longitudinal plane and transverse plane.

20. In the DCP (A), the area at the plate holes is less stiff than the area between them so while bending, the plate tends to bend only in the areas of the hole. The LC-DCP(B) has an even stiffness without the risk of buckling at the screw holes.

21. The LC-DCP offers additional advantage Improve blood circulation by minimizing plate-bone contact More evenly distribution of stiffness through the plate Allows small bone bridge beneath the plate

22. Tubular plates 3.5 system - 1/3 rd Tubular 4.5 system - Semitubular Limited stability -Oval holes – Axial compression can be achieved. -Low rigidity (1mm thick). Lateral malleolus Distal ulna / Olecranon Distal humerus

23. 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 .

24. Reconstruction plates Deep notches between holes Accurate contouring in any plane Pelvis Acetabulum Distal humerus Clavicle Olecranon

25. Reconstruction plates are thicker than third tubular plates but not quite as thick as dynamic compression plates. Designed with deep notches between the holes, they can be contoured in 3 planes to fit complex surfaces, as around the pelvis and acetabulum . Reconstruction plates are provided in straight and slightly thicker and stiffer precurved lengths. As with tubular plates, they have oval screw holes, allowing potential for limited compression.

26. LCP – Locking Compression Plate

27. LCP Latest in the evolution “ Internal fixator ” Combination of locking screw with conventional screw Extraperiosteal location of plate

28. LCP: internal external fixator

29. LCP Combines advantages of DCP principle and locking head principle. Flexibility of choice within a single implant. Screw hole have been specially designed to accept either: cortical screw and locking screw

30. The locking screws, by achieving angular stability within the plate holes are able to produce a similar hoop with just two unicortical screws. LCP

31. LOCKING COMPRESSION PLATE ( LCP) Principle : Angular-stability whereas stability of conventional plates is friction between the plate and bone Screw locking principle Provides the relative stability  Healing by callus formation (Secondary Healing)

32. Stability under load By locking the screws to the plate, the axial force is transmitted over the length of the plate secondary loss of the intraoperative reduction is reduced Blood supply to the bone No additional compression after locking Periosteal blood supply will be preserved

33. LCP used as internal fixator to bridge multifragmentary diaphyseal fracture zone. Locking compression plate is used. Standard cortical and cancellous screws are used as a traditional plate. LCP

34. Principle of internal fixation using LCP : 1. 1 st reduced the # as anatomical as possible 2. Cortical screw should be used 1 st in a fracture fragment 3. If the locking screw have been put, use of the cortical screw in the same fragment without loosening and retightening of the locking screw is not recommended 4. If locking screw is used first avoid spinning of plate 5. Unicortical screws causes no loss of stability

35. 6. In Osteoporotic bone bicortical screws should be used. 7. In comminuted # screw holes close to the fracture should be used to reduce strain. 8. In the fracture with small or no gap the immediate screw holes should be left unfilled to reduced the strain. Principle of internal fixation using LCP :

36. Indications : Osteoporotic # Periprosthetic # Multifragmentry # Delayed change from external fixation to internal fixation.

37. 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

38. Sizes of DCP Name of plate Small Narrow Broad Width 11 mm 13.5 mm 17.5mm Profile 4 mm 5.4 mm 5.4 mm Screw 2.7 , 3.5 cortex screw and 4 mm cancellous screw 4.5 mm cortex screw & 6.5mm canellous screw 4.5 mm cortex screw & 6.5mm canellous screw Sizes of LCDCP Name of plate Small Narrow Broad Width 11 mm 13.5 mm 17.5mm Profile 4 mm 5.4 mm 5.4 mm Screw 2.7 , 3.5 and 4 mm cancellous screw 4.5 mm & 6.5mm canellous screw 4.5 mm & 6.5mm canellous screw Name of plate Small Narrow Broad Width 11 mm 13.5 mm 17.5mm Profile 4 mm 5.0 mm 5.0 mm Screw 4 mm locking screw 5 mm locking screw 5 mm locking screw Sizes of LCP

39. LISS System Preshaped plates with self drilling self tapping screws with threaded heads. Through a small incision (using this jig ) plate is slid along the bone surface. position of plate and wire are checked radiologically before insertion of metaphyseal screw .

40. LISS-Less Invasive Stabilization System

41. LISS

42. Type of plate – Functional Regardless of their length, thickness, geometry, configuration and types of hole, all plates may be classified in to 4 groups according to their function. Neutralization plate. Compression plates. Buttress plate. Tension band plates.

43. NEUTRALIZATION PLATE Acts as a ""bridge”” protection No compression at the fracture site neutralization plate is to protect the screw fixation of a short oblique fracture a butterfly fragment a mildly comminuted fracture of a long bone fixation of a segmental bone defect in combination with bone grafting.

44. The Neutralization Plate Lag screws: compression and initial stability Plate: protects the screws from bending and torsional loads

45. NEUTRALIZATION PLATE

46. COMPRESSION PLATE produces a locking force across a fracture site plate is attached to a bone fragment then pulled across the fracture site , producing tension in the plate Direction of the compression force is parallel to the plate

47. Compression Plate Principle : - a self compression plate due to the special geometry of screw holes which allow the axial compression.

48. Dynamic compression principle: a The holes of the plate are shaped like an inclined and transverse cylinder. b–c Like a ball, the screw head slides down the inclined cylinder. d–e Due to the shape of the plate hole, the plate is being moved horizontally when the screw is driven home. f The horizontal movement of the head, as it impacts against the angled side of the hole, results in movement of the plate and the fracture fragment already attached to the plate by the first screw (1). This leads to compression of the fracture .

49. 51 Compression plate: eccentric DC (dynamic compression) hole Removable device: compression device Interfragmentary compression by plate

50. 52 External compression device

51. METHODS OF ACHIEVING COMPRESSION With tension devise By overbending With dynamic compression principle (DCP/LC-DCP) By contouring plate Additional lag screw thro plate

52. BUTTRESS PLATE is to strengthen (buttress) a weakened area of cortex The plate prevents the bone from collapsing during the healing process. A buttress plate applied a force to the bone which is perpendicular (normal) to the flat surface of the plate.

53. The fixation to the bone should begin in the middle of the plate, closest to the fracture site on the shaft. The screws should then be applied in an orderly fashion, one after the other, towards both ends of the plate . example : the T-plate used for the fixation of fractures of the distal radius and the tibial plateau. BUTTRESS PLATE

54. Bridge Plating Bridge Plating for comminuted fracture instead of individually fixing each fragment minimal disruption to blood supply reduction is performed indirectly - compression is only sometimes possible

55. TENSION BAND PRINCIPLE Tension-band principle.

56. Tension Band Principle :- Its describes how the tensile forces are converted into compressive forces by applying a devise eccentrically or to the convex side of a curved tube or bone. Indications :- Fracture Patella, olecranon , medial malleolus , greater trochanter of the femur. Static Dynamic

57. Dynamic and static tension band In dynamic tension band the tensile forces are converted to compression on the convex side of an eccentrically loaded bone Examples : Patella Olecranon Greater tuberosity Tension band principle to the medial malleolus example of static tension band

58. HOW MANY SCREWS ? 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

59. Timing of Plate Removal Malleolar fractures. 8-12mo The tibial pilon. 12-18mo The tibial shaft. 12-18mo The tibial plateau. 12-18mo The femoral condyles. 12-24mo The femoral shaft. 24-36mo Upper extremity. 12-18mo Shaft of radius / ulna. 24-28mo Distal radius. 8-12mo Metacarpals. 4-6mo

60. SCREW: INTRODUCTION An elementary machine to change the small applied rotational force into a large compression force Function Holds the plate or other prosthesis to the bone Fixes the # fragments ( Position screw) Achieves compression between the # fragments (Lag screw)

61. SCREWS 4 functional parts Head Shaft\ Shank \Core Thread Tip

62. Head: Recess Types 1. Slotted 2. Cruciate 3. Philips 4. Hex/ Allen 5. Torx ( eg Stardrive of Synthes )

63. Screw: Shaft/ Shank/ Core Smooth link Almost not present in standard cortex screw Present in cortical SHAFT SCREW or cancellous screw

64. Screw: Run out Transition between shaft and thread Site of most stress riser Screw break Incorrectly centered hole Hole not perpendicular to the plate

65. Screw: Thread Inclined plane encircling the root Single thread May have two or more sets of threads V-thread profile: more stress at sharp corner Buttress thread profile: less stress at the rounded corner

66. Core Solid section from which the threads project out wards. The size of core determines the strength of screw and its fatigue resistance. The size of drill bit used is equal to the core diameter.

67. Screw: Core Diameter Narrowest diameter across the base of threads Also the weakest part Smaller root  shear off Torsional strength varies with the cube of its root diameter

68. Screw: Thread Diameter Diameter across the maximum thread width Affects the pull out strength Cancellous have larger thread diameter

69. Screw: Tip Designs 1. Self-tapping tip: Flute Cuts threads in the bone over which screw advances Cutting flutes chisel into the bone and direct the cut chips away from the root

70. Screw: 2.Non self tapping Lacks flutes Rounded tip Must be pre-cut in the pilot hole by tap Pre-tapped threads help to achieve greater effective torque and thus higher inter-fragmental compression Better purchase

71. Screw: 3.Corkscrew tip Thread forming tips In Cancellous screws which form own threads by compressing the thin walled trabecular bone Inadequate for cortical bone

72. Screw: 4.Trochar Tip Like self tapping Displaces the bone as it advances Malleolar screw Schanz screws Locking bolts for IMIL

73. Screw: 5.Self drilling self tapping Like a drill bit In locked internal fixator plate hole Pre-drilling not required Flute Good purchase in osteoporotic and metaphyseal area

74. Locking Screws vs Cortical Screws Creates Fixed Angle Generates Friction/Compression 4.4mm Core Dia. 3.5mm Core Dia. 5.0 mm Locking Screw 4.5 mm Cortical Screw

75. Bending stiffness proportional to the core diameter Pull out strength is proportional to the size of the thread Cannulated screws have less bending stiffness

76. Biomechanics Locking Screw Design: Shaft Why smaller threads? Not used to generate compression between plate and bone Why larger core diameter? Decreased thread diameter allows increased core diameter Greater bending and shear strength Dissipates load over larger area in bone Cortex Screw Locking Screw

77. AO/ASIF Screws: Types Cortical Fully threaded Shaft screw 1.5:phalanx *drill bit 1.1 mm 2.7: mc and phalanx *bit:2.0 3.5: Radius/ Ulna/ Fibula/ Clavicle*bit:2.5 4.5: Humerus/ Tibia/ femur *bit:3.2

78. AO/ASIF Screws Cortical screws: a machine type Smaller threads Lower pitch Large core diameter Smaller pitch higher holding power greater surface area of exposed thread for any given length better hold in cortical bone

79. AO/ASIF Screws Cancellous screws: a wood type core diameter is less the large threads Higher pitch Greater surface are for purchase Untaped pilot hole Pilot hole equals the core diameter lag effect option with partially threaded screws theoretically allows better fixation in soft cancellous bone.

80. Cancellous Fully threaded Cannulated or Non- cannulated Partially threaded 16mm or 32 mm Cannulated or Non- cannulated 4.0,  drill bit 2.5mm humeral condyle 6.5  drill bit 3.2mm tibial and femoral condyle

81. MALLEOLAR SCREW: - smooth shaft - partially threaded - trephine tip : no tapping needed - was designed as lag screw for malleoli fixation NOW small cancellous screws preffered - distal humerus and lesser trochanter - size : 25mm – 75 mm

82. Cannulated screws 3.0 4.0 4.5 6.5 7.0 7.3

83. Special Screws Locking bolt Herbert Screw Dynamic Hip Screw Malleolar Screw Interference screw Acutrak screw

84. Pedicle screw Suture anchor

85. Headless Screws Herbert screw bridging a scaphoid fracture Acutrak screw

86. Bioabsorbable Screws The most common materials used are polylactic acid (PLA), poly-L-lactic acid (PLLA), and polyglycolic acid.

87. Advantages of bioabsorbable screws • Does not interfere with MRI. • Does not interfere with future revision surgery if needed. • Decreased incidence of graft laceration. • Does not need implant removal

88. Disadvantages of bioabsorbable screws • Major disadvantage is screw failure during insertion. Special screw drivers that span the entire length of screw reduce incidence of screw breakage. • Foreign body reaction may be seen in some.

89. Function or mechanism. Neutralization screws – neutralizes forces on the plate in plate fixation. Lag screws – For inter-fragmentary compression . Reduction screw – To reduce displaced fracture by pushing or pulling . Position screw – Holds two fragments in position without compression. Eq. Syndesmotic screw Anchor screw – Acts as an anchor for wire or suture. In tension band wiring Locking head screw – In locking plates Locking screw – In interlocking nails Poller screw – To guide the nail path in interlocking nailing of fractures close to the bone ends.

90. TAP To cut threads in bone of same size as the screw to facilitate insertion Flutes : to clear the bone debris Two turns forward and half turn backward recommended to clear debris Used with sleeve Done manually Power tapping NOT recommended For cancellous bone : short and wide thread , slightly smaller dia than screw

91. For cortical screws : - as fixation screw : both cortices - as lag screw : only far cortex For cancellous screw: - only near cortex - sometimes in young patients tapping entire screw length needed

92. LAG SCREW TECHNIQUE : - to achieve interfragmentary compression - this technique is used if a screw is to be inserted across a # , even through a plate. - screw has no purchase in near fragment, thread grips the far fragment only -achieved either with screw with shaft or fully threaded screw

93. Positioning of screws: -max. interfragmentary compression : placed in middle of fragment, right angle to fracture plane - max. axial stability: right angle to long axis of bone

94. Thank You