AO principles

1. D E P A R TM E N T O F
O R T H O P A E D IC S
G A N D H I M E D IC A L C O L L E G E ,
B HOPAL
S e m inar O n
PRINC IPL E S A ND TE C HNIQUE S OF A O
Moderator : Presented by :
D r . J . S h u k la D r . S u n il
D r. A.
S in s in w a r

2. HISTORY OF OSTEOSYNTHESIS
• The term osteosynthesis was coined by
Albin Lambotte a Belgian surgeon
regarded universally has the father of the
modern internal and external fixation. He
devised an external fixator and numerous
different plates and screws.
• Robert Danis as surgeon in Brussel
published two books on osteosynthesis in
1932 and 1949.

3. • A young swiss surgeon E. muller read his
second book and he drew around
himself a group of interested swiss
surgeons and in 1958, at an historical
weekend meeting in chur they decided
to form a study group concerning issue
of internal fixation of bone- the
Arbeitgemeinschaft fur Osteosynthe-
sefragen, or AO.

4. Principles of AO :
• 1. Anatomical Reduction.
• 2. Stable internal fixation.
• 3. Preservation of Blood supply
• 4. Early active pain free mobilisation.

5. BIOMECHANICAL ASPECTS OF
THE AO TECHNIQUE
• Neutralization Plate or Protection Plate
• Compression Plating
• Lag screw
• Tension Band Principle
• Intra Medullary Nailing
• External Fixation.

6. 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.

7. Standard Plates
• Narrow DCP-4.5 mm
• Broad DCP – 4.5 mm
• 3.5 mm DCP
• LC-DCP 3.5 & 4.5mm
• Reconstruction plate 3.5 & 4.5mm
• 1/3 tubular plate 2.7, 3.5 & 4.5 mm

8. Special Plates
• T Plates
• T&L Buttress plates
• Lateral Tibial head buttress plates
• Condylar butters plate
• Narrow lenthening plates
• Broad Lengthening plate
• Spoon plate
• Clover leaf plate

9. CLASSIFICATION
• Regardless of their length, thickness,
geometry, configuration or type of holes,
all pates may be classified in four groups
according to their function.
• Neutralization Plates.
• Compression Plates.
• Buttress Plates.

10. Buttress Neutral Load
Position Position Position

11. NEUTRALIZATION PLATE
• A neutralization plate acts as a ""bridge". It
transmits various forces from one end of the bone
to the other, bypassing the area of the fracture.
Its main function is to act as a mechanical link
between the healthy segments of bone above and
below the fracture. Such a plate does not produce
any compression at the fracture site.
• The most common clinical application of the
neutralization plate is to protect the screw fixation
of a short oblique fracture, a butterfly fragment or
a mildly comminuted fracture of a long bone, or
for the fixation of a segmental bone defect in
combination with bone grafting.

12. COMPRESSION PLATE
• A compression plate produces a locking force
across a fracture site to which it is applied.
The effect occurs according to Newton's Third
Law (action and reaction are equal opposite).
The plate is attached to a bone fragment. It is
then pulled across the fracture site by a
device, producing tension in the plate. As a
reaction to this tension, compression is
produced at the fracture site across which the
plate is fixed with the screws. The direction of
the compression force is parallel to the plate.

13. Application of Compression Plate

14. BONE UNDER COMPRESSION
• Superior stability – Utilization of
physiological forces.
• Improved milieu for bone healing.
• Early mobilization.

15. BUTTRESS PLATE
• The mechanical function of this plate, as the
name suggests, is to strengthen (buttress) a
weakened area of cortex. The plate prevents the
bone from collapsing during the healing process.
It is usually designed with a large surface area
to facilitate wider distribution of the load.
• A buttress plate applied a force to the bone
which is perpendicular (normal) to the flat
surface of the plate.

16. • The fixation to the bone should begin in
the middle of the plate, i.e. 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.
• A representative clinical example of a
buttress plate is the T-plate used for the
fixation of fractures of the distal radius
and the tibial plateau.

17. DCP (Dynamic Compression Plate):
Principle :
- Its a self compression plate due to the
special geometry of screw holes which
allow the axial compression.

18. Dynamic compression principle: The holes of the plate are
shaped like an inclined and transverse cylinder. Like a ball, the
screw head slides down the inclined cylinder. Because the screw
head is fixed to the bone via the shaft, it can only move vertically
relative to the bone. The horizontal movement of the head, as it
impacts the angled side of the hole, results in movement of the
bone fragment relative to the plate and leads to compression of
the fracture.

19. • Screw hole and the spherical gliding
principle.
• Axial compression result from the an interplay
between screw hole geometry and eccentric
placement of the screw in the screw hole. The
screw hole is a combination of incline and
horizontal cylinder which permits the downward
and the horizontal movement of a sphere the
screw hand. Sideway movement of screw head
is impossible. The aim is to position the screw
head at the intersection of inclined and the
horizontal cylinder. At this point screw head has
a spherical contact in the screw hole which
result in the maximum stability without
completely blocking the horizontal movement of
the screw.

20. General principles of internal fixation.

21. The shape of the holes of the dynamic compression
plate allows inclination of the screws in a transverse
direction of +7° and in a longitudinal direction of
25°.

22. 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 load screw for the compression.
4. Usage of two load 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.

23. Short Coming of DCP :
1. Flat under surface.
2. Inclination upto 25°
3. Plate hole distribution (extended middle
segment)

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

25. 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.

26. • The LC-DCP (limited contact DCP) is a further
development of the DCP is used for the same
indications as the DCP, but the improved design
offers additional advantage.
• The evenly distributed undercuts reduces the
contact area between bone and plate to a
minimum. This significantly reduces impairment
of the blood supply of the underlying cortical
bone undercuts also allow for the formation of a
small callusbridge.
• The enlarged cross section at the plate holes and
the reduced cross section between holes offer a
constant degree of stiffness along the long axis
of the plate.

27. • The trapezoid cross section of the plate
results in a smaller contact area between
plate and bone.
• The plate holes are uniformaly spaced,
which permits easy positioning of the
plate.
• 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. Lag screw fixation of short
oblique fractures is thereby possible.

28. Bridge Plating :
Bridge Plating for
comminuted fracture

29. Wave Plating :
Wave Plating for
non union.

30. ADDITIONAL PRINCIPLES OF
PLATE FIXATION
• The engineering principle of the tension
band is widely used in fracture fixation. It
applies to the conversion of tensile forces
to compression forces on the convex side
of an eccentrically loaded bone.

31. PREBENDING PLATES
• Contour to fit the bone surface snugly.
• Make a sharp bend opposite the fracture
site; midsection is elevated.
• Fix to the bone, starting on either side of
the fracture and then moving outwards.
• Plate then compresses the far cortex also.
• Apply only to two fragment fractures.

32. 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

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

34. 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.

35. 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.

36. 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.

37. 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.

38. LOCKING COMPRESSION PLATE (LCP)
Principle :
• The basic principle of LCP is its angular stability
whereas stability of conventional plate
osteosynthesis relies on the friction between
the plate and bone.
• The principle of fixation of LCP is screw locking.
• The functional LCP screw is like that of external
fixator pins, that is why they are called as
internal fixator.
• LCP provides the relative stability.
• # heals by the callus formation (Secondary
Healing).

39. The mechanical principle of a locked screw plate. (A) The
plate sits slightly of the bone. (B) Tightening of the screw
locks the screw head within the plate. The plate is not
drawn toward the bone and there is no compression b/w
the bone and the plate. The flux is bone/ screw/ plate/
screw/ bone.

40. Bridge/Locked Plating Using
Locking Screws
• Screws lock to the plate, forming a
fixed-angle construct.
• Bone healing is achieved indirectly
by callus formation when using
locking screws exclusively.
Maintenance of primary reduction
Once the locking screws engage the plate, no further
tightening is possible. Therefore, the implant locks the bone
segments in their relative positions regardless of degree of
reduction. Precontouring the plate minimizes the gap
between the plate and the bone, but an exact fit is not
necessary for implant stability. This feature is especially
advantageous in minimally or less invasive plating
techniques because these techniques do not allow exact
contouring of the plate to the bone surface.

41. Stability under load
By locking the screws to the
plate, the axial force is
transmitted over the length of the
plate. The risk of a secondary
loss of the intraoperative
reduction is reduced.
Blood supply to the bone
Locking the screw into the plate
does not generate additional
compression. Therefore, the
periosteum will be protected and
the blood supply to the bone
preserved.

42. Plate Design :
• LC DCP features :
• Tapered end for
sub
muscular insertion.
• Locking holes

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

44. Principle of internal fixation
using LCP :
1. 1st reduced the # as anatomical as possible.
2. Cortical screw should be used 1st 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
plates.
5. Unicortical screws causes no loss of stability.

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

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

48. Plate screw density and fracture plate quotient

49. 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.

50. Timing of Plate Removal,
Recommendations for removal of
plates in the lower limb :
• Bone / Fracture
• Time after implantation in months
• Malleolar fractures
• 8-12
• The tibial pilon
• 12-18
• The tibial shaft
• 12-18
• The tibial head
• 12-18

51. • 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
• Optional
• Shaft of radius / ulna
• 24-28
• Distal radius
• 8-12
• Metacarpals
• 4-6

52. Cortical Screw :
- Use in the hard cortical bone mainly in the
diaphysis of the long bones.
- Large core diameter
- Non self cutting
- Tapping is required.
Cancellous Screw :
- Large thread depth
- Large pitch.
- Non self tapping.
- Tapping only near cortex.

53. The screw thread is defined by its major or outside
and minor or root diameters, pitch, lead, and number
of threads. Bottom: Screw head drive types.

54. Common screw.

55. Indication :
- Metaphyseal and epiphyseal areas
- Partially Threaded (for lag screw)
- Fully threaded (for plates)
- Cannulated or Non cannulated

56. Drill Bit :
Used for drilling the hole in the bone.
- Sizes 2.5 mm, 3.2 mm, 2 mm, 4.5 mm.
- Always use the drill bit with the sleeve.
- Standard drill bits – 2 flutes – air drill.
- Three flutes drill bits – Better for drilling at
oblique angles.
- During the drilling normal saline should be
used.
- Canulated drill bit used for drilling over guide
wires.

57. Cutting lip
Cutting Edge
Flute
Margin
Axis of drill
Drill Bit

58. Taps :
Used for cutting the thread in the bone.
Cortical Tap :
- Used to cut threads in the bone of same size as
the screw.
- Have 3 flutes.
- Entire far cortex must be taped.
- Taping should be done manually.
- Two turn forward and half turn in the reverse
direction.
Cancellous Tap :
- Short and wide threads slightly smaller than
the screw.
- One near cortex tapping is required.

59. DIFFERENT AO SCREWS
LARGE STANDARD SCREWS. 4.5 mm Cortex Screw
6.5 mm Cancellous Screw
Malleolar Screw 4.5
CANNULATED SCREW SYSTEM 6.5 Cannulated Screw
4.0 mm Cannulated Screw
3.5 Cannulated Screw
SMALL FRAGMENT SCREW 3.5 mm Cortical Screw
4.0 Canceleous Screw
-Partially Threaded.
-Fully Threaded
MINI SCREW 2.7 mm Cortex Screw
2.0 mm Cortex Screw
1.5 mm Cortex Screw

60. THE LAG SCREW
A lag screw is the most effective way to
achieve compression between two bone
fragments; it pulls the fragments together
producing pressure across the fracture line. It
achieves this by providing purchase on the
distal fragment while being able to turn freely
in the proximal. If the screw threads engage
both cortices, the fragments remain apart like
two nuts on the same bolt.

61. Top: Biomechanics of cannulated and noncannulated
screws. Bottom: Ideally, lag screw fixation produces
maximum interfragmentary compression when the
screw is placed perpendicular to the fracture line.

62. Optimal inclination of the screw in relation to a simple
fracture plane.

63. T-lag screw.

64. PRINCIPLE
• The screw must glide freely through the
near fragment and engage only the far
fragment.
• Wherever a screw crosses a fracture line it
should be inserted as lag screw.
• Two small screws produce a more stable
fixation than one large screw.

65. Screw Core Thread Pitch Drill bit Drill bit Tap
diamet diamet for for diamet
er er gliding thread er
hole hole
Large 7mm 4.5mm 7mm 2.75mm 4.5mm 7mm
Standard Cancellou
Screws s Screw
6.5mm 3.5mm 6.5mm 2.7mm 3.2mm 4.5mm 6.5mm
cancellous
screw
4.5mm 4.5mm 3.1mm 1.75mm 3.2mm 4.5mm
cancellous
screw
4.5mm 3mm 4.5 mm 1.75mm 4.5mm 3.2mm 4.5mm
cortical

66. Small 3.5mm 2.5mm 3.5mm 1.25mm 2.7mm 3.5mm
Fragment cancellous
Screws screw
4mm 1.9mm 4mm 1.75mm 2.5mm 4mm
Cancellous
screw
3.5mm 2.4mm 3.5mm 1.25mm 3.5mm 2.5mm 3.5mm
Cortex
Screw
Mini 2.7mm 1.9mm 2.7mm 1mm 2.7mm 2mm 2.7mm
Fragment Cortex
Screws Screw
2mm 1.3mm 2mm 0.6mm 2mm 1.5mm 2mm
Cortex
Screw
1.5mm 1mm 1.5mm 0.5mm 1.5mm 1.1mm 1.5mm
Cortex
Screw

67. 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.

68. DYNAMIC CONDYLAR SCREW
• The dynamic condylar screw (DCS) is similar
to the DHS in its design and concept. The
fixed angle between plate and barrel is 95 and
the plate is contoured to fit the lateral surface
of the distal end of the femur.
• The main indications are fractures of the distal
femur and inter-condylar fractures. It may also
be used for certain intertrochanteric fractures
and very proximal subtrochanteric fractures.
Impaction of compression of the fracture is
achieved by using the compression screw.

69. DHS :
• Example of measurements :
• Length of measurements :
• Length measured 105 mm
• Reamer setting 95 mm
• Tapping depth 95 mm
• DHS/DCS Screw length 95 mm
DCS
• Length measured 85 mm
• Reamer setting 75 mm
• Tapping depth 75 mm
• DCS Screw 70 mm

70. Canulated Cancellous Screw Fixation in
Fracture Neck Femur :
- Parallel 6.5mm CCS are used in triangular or inverted
triangular configuration.
- After fracture reduction antiversion is determined.
- 2mm threaded guide wire is inserted in the centre of
the neck in both AP and lateral view.
- Parallel wire guide is replaced over the central guide
wire.
- 2mm guide wire are inserted into the subchondral bone
of the femoral head starting with the most superior.
- Parallel wire guide is removed and length is
determined.
- Canulated drill bit is used.
- Tapping is done with 6.5mm tap.
- Appropriate screws are inserted.

71. TENSION BAND PRINCIPLE
Tension-band principle.

72. Tension-band principle at the femur.

73. • 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

74. Pitfalls and Complications:
• The most complication is failure of the
implant. A wire put under pure tension is
very strong. However, if bending forces
are added, it will break by fatigue quite
rapidly. As this also holds true for plates, it
appears essential that in the diaphysis, the
tension side of the bone is known and the
opposite cortex is able to withstand the
compression forces.

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

76. 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.

77. 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.

78. INDICATINOS FOR UNIVERSAL
NAILING OF FEMUR AND TIBIA
WITH AND WITHOUT LOCKING
• Conventional nailing without locking for stable
fractures with bony support in the middle third
of the bone, such as:
• Transverse fractures.
• Short oblique fractures
• Delayed union or nonunion
• Locked medullary nailing for unstable fractures
without bony support in approximately the
middle 60% of the bone, where axial and
rotational stability has to be achieved, such as

79.  Fractures near the metaphysic
 Long torsional fractures
 Segmental fractures
 Multifragmentary fractures
 Fractures with bone defects.
TYPES OF INTRAMEDULLARY NAILS :
• Centromedullary nails
• Condylocephalic nails
• Cephalomedullary nails

80. Working Length
Blk screws.

81. K wire :
Used for the temporary and permanent
fixation
- Trocar Tip : 0.6 mm, 0.8 mm, 1 mm,
1.25 mm, 1.6 mm, 2mm, 2.5 mm, 3 mm.
- Threaded Tip : 1.6 mm, 2 mm, 2.5 mm
- Double Trocar Tip : 0.6 mm, 0.8 mm,
1.25 mm, 1.6 mm, 2 mm.

82. EXTERNAL FIXATION
Introduction :
• An external fixator is a device placed outside the skin
which stabilizes the bone fragments through wires or
pins connected to one or more longitudinal bars/
tubes.
Biomechanical Aspects :
• Components of standard external fixators
• Pins (Schanz screws/Steinmann pins)
• Stainless steel tubes or carbon fibre rods
• A variety of clamps to fasten pins/wires to
tubes/rods
• A variety of clamps to fasten pins/wires to
tubes/rods.
• Clamps to connect tubes/rods to tubes/rods

83. There are a variety of pins and wires
available:
• Steinmann pins for bilateral frames
• Schanz screws, either self drilling or requiring pre
drilling
• Schanz screws with small diameter tips for use in
small bones.
• 2.0 and 1.8 mm K-wires (#olives) for ring fixator.
• Threaded K-wires for small external fixators.
• The standard tubular system is employed for
treatment of fractures in large bones, for
arthrodesis, and for bone lengtheneing and
transport systems. The small external fixator is
used mainly for fractures or distal radius and
forearm as well as for fractures in children and
adolescents.

84. Types of external fixators:
• Pin fixators:
• Unilateral
• V-shaped,
• Bilateral frame,
• Triangular,
• Ring (wire fixators)
• Hybrdfixators (wire pin)
• Pinless external fixator.
• Mefisto (Monolateral External fixator System in
traumatology and orthopedics).
• Considerations when applying the external fixator

85. • Frame Stiffness and Fracture stabilization of
long bones.
• Placing the main frame. in the sagital plane
• Increasing the main frame in the sagital plane.
• Preloading the Schanz screws by pre-drilling 4.5
mm and using the 5.0 mm
• Schanz screws with 4.6 mm core size (radial pre
load).
• Increasing the no. of Schanz screws in each
main fragment.
• Reducing the distance between the bone and
the tube.
• Using double tube frame.

86. • Increasing the distance between the tubes.
• Applying a two plane unilateral frame.
• Insufficiently stable external fixation may
delay fracture healing and lead to pin
loosening. However, too much stiffness or
rigidity of the external fixator construct may
also delay fracture healing, expecially in open
fractures. In the managmenet of such
fractures it may be necessary to "dynamise"
an initially quiet stable configuration or add
stability in case of pin loosening.

87. Indications of External Fixator :
• Stabilization and correction of extremity mal
alignment and length discrepanicies in severe
open fractures and infected non unions.
• Initial stabilization of bony disruption and soft
tissue injuries in poly traumatized patients.
• Closed fractures associated with severe soft
tissue damange.
• Multifragmentary disaphyseal and periarticular
lesions
• Certain pelvic ring disruptions
• Arthrodesis
• Compression fixation in osteotomies.

88. Frame Construction :
• Good pin insertion practice
• Make a liberal skin incision; spread deeper
soft tissues with haemostar.
• Lift periosteum with small elevator to prevent
damage by drill bit.
• Use trocar to mark pin insertion point.
• Employ sleeve to drill a pilot hole and to insert
a pin.
• Use a power drill.

89. • Sharp drill bit with simultaneous saline
irrigation prevents thermal damage.
• Clean drill bit flutes often
• Use depth guage for accurate pin length.
• Insert pin with hand instrument.

90. Bibliography
- AO/ASIF Instruments and Implants
- Manual of Internal Fixation
- The Elements of Fracture Fixation
- Rockwood and Green
- Campbel Operative Orthopaedics