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 mobilisation

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. • Brothers 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 immobilization
-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 =
10 Bone Healing
Relative Stability =
20 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.

24. The distractor

25. • 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).

26. 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.)

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

28. • 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)

29. • 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, 5th ed.

30. • 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.

31. 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.

32. 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

33. 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

34. 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

35. 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

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

37. • 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

40. 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

41. 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,

42. 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

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

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

45. 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

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

47. Dynamic compression principle
•

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

49. Verbrugg forceps used for tensioning

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

53. • 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

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

56. 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.

57. • 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

58. 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

60. 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

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

62. • Order of fixation:
• Articular surface compressed with
bone forceps and provisionally fixed
with k-wires
1. Bottom 3 cortical screws placed
• Provide buttress effect
2. Top 2 partially-threaded cancellous
screws placed
• Lag articular surface together
3. 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.

63. Antiglide plate

64. 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

66. 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

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

71. Application of straight plate to curved bone

72. Effect of forces

76. Torsional stability

77. Counting number of engaged cortices

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

79. 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

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

81. • 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

82. 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.

83. 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.

84. 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.

85. 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.

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

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

88. • 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

89. • 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

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

92. • 1st reduced the # as anatomical as possible
• Cortical screw should be used 1st in a fracture
fragment.
• If locking screw is used first avoid spinning of
plates.
• Unicortical screws causes no loss of stability

93. • 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

94. Indications :
1. Osteoporotic #
2. Periprosthetic #
3. Multifragmentry #
4. 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.

95. Plate screw density and fracture plate quotient

96. 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.

97. 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

98. • 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

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

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

101. 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.

102. 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.

103. TYPES OF INTRAMEDULLARY NAILS :
• Centromedullary nails
• Condylocephalic nails
• Cephalomedullary nails

104. Blk screws.
Working Length

105. 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

106. 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

107. • 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.

108. • 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...

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

110. 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.

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

112. Should be less than 28mm

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

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

115. • 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

116. Biomechanics – Pauwels 1935

117. Biomechanics

118. Biomechanics

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

120. 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.

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

123. Bilateral cable ension band operation

124. Treatment options for comminuted
patella fractures

125. Comminuted fracture –circlage wire
and K wire fixation

126. 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.

127. 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)

128. Thankyou