Plates and screws 11

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

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

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]

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.

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.

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.

Bone Suture Stabilization
Inserts (Koenig, 1905)

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.

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

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

Special Plates
 T Plates
 T&L Buttress plates

 Lateral proximalTibial
buttress plates
 Condylar buttress plate
 Narrow lengthening
plates

 Broad Lengthening
plate
 Spoon plate
 Clover leaf plate

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

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

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

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.

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.

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

Tubular plates
 3.5 system - 1/3rd 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

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.

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

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.

LCP – Locking Compression Plate

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

LCP: internal external fixator

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

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

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)

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

 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

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 plate
5. Unicortical screws causes no loss of stability

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 :

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

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
Screw 2.7 , 3.5 and 4 mm
cancellous screw
4.5 mm & 6.5mm
canellous screw
4.5 mm & 6.5mm
canellous screw
Screw 4 mm locking screw 5 mm locking screw 5 mm locking screw
Sizes of LCP

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 .

LISS-Less Invasive Stabilization
System

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.
1. Neutralization plate.
2. Compression plates.
3. Buttress plate.
4. Tension band plates.

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.

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

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

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

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.

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

52
External compression device

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

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.

• 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

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

TENSION BAND PRINCIPLE
Tension-band principle.

 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

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

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

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

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)

SCREWS
 4 functional parts
 Head
 Shaft Shank Core
 Thread
 Tip

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

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

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

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

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.

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

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

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

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

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

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

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

Locking Screws vs Cortical
Screws
Creates FixedAngle Generates
Friction/Compression
4.4mmCore Dia. 3.5mm Core Dia.
5.0 mm Locking Screw 4.5 mm Cortical Screw

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

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

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

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.

 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

 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

 Cannulated screws
 3.0
 4.0
 4.5
 6.5
 7.0
 7.3

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

 Pedicle screw
 Suture anchor

Headless Screws
Herbert screw bridging
a scaphoid fracture
Acutrak screw

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

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

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.

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.

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

 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

 LAG SCREWTECHNIQUE :
- 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

 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

Plates and screws 11

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