Bone plate for fixation of fracture

1. BONE PLATES
Presented By:
Dr Dipendra Maharjan
1st yr Resident,
Orthopaedics

2. AO PRINCIPLES
• In 1958, the AO formulated four basic
principles which have become guideline for
internal fixation
– Anatomical reduction
– Stable fixation
– Preservation of blood supply
– Early active mobilization

3. BONE PLATE
• Like an internal splints holding together the
fractured end of a bone
• A load sharing device
• General principle – anatomical reduction and
stable internal fixation
• Two mechanical function
– Transmits force from one end to another bypassing
fracture area
– Holds the fracture ends while maintaining alignment
of the fragments

4. CLASSIFICATION
• Shape of the plate (semitubular plate)
• Width of the plate (broad/Narrow)
• Shape of the screw hole (Round hole plate)
• Surface contact characteristics of the plate
(low contact)
• Intended site of application (Condylar)

5. Contd…
• Classified into a group, according to their
function
– Neutralization plate
– Compression plate
– Buttress plate
– Condylar plate

6. NEUTRALIZATION PLATE
• Transmits force from one end to
another bypassing the fracture site
• Acts as a bridge
• Function – mechanical link
between healthy segment of bone
above and below fracture
• Does not produce compression
• In combination with lag screw is
also neutralization plate

7. • If geometry permits, produce compression at
fracture site
• Clinical application
– To protect the screw fixation of a short oblique
fracture
– Butter fragment
– Mildly comminuted fracture of long bone
– Fixation of segmental bone defect in combination
with bone graft

8. COMPRESSION PLATE
• Produce locking force across a
fracture site
• Works as per Newton’s third
law
• Direction of compression is
parallel to plate
• General principle
– A plate is attached to a bone
fragment, pulled across the
fracture site and tension is
produces. As a reaction to this
tension, compression is produced
at the fracture site.

9. • ROLE OF COMPRESSION
– Compaction of fracture to force together
• Increase stability of the construct
– Reduction of the space between bone fragments
– Protection of blood supply
– Friction
• Resists the tendency of fragment to slide under torsion
or shear force
– Generates axial inter-fragmental compression
• Fracture immobilization to that of neutralization plate

10. • Compression may be static or dynamic
compression
– Dynamic
• A phenomenon by which a plate can transfer or modify
functional physiological force into compression force at
fracture site
– Static
• A plate applied under tension produces static
compression site, this compression exist constantly even
when limb is at rest or functioning

11. DYNAMIC COMPRESSION PLATE
• Two basic functions:
– independent axial compression
– the ability to place screws at different angles of
inclination.
• There are three areas in which to place a
screw:
– one at each end (eccentrically)
– one in the middle (concentrically).
• The act of compression is accomplished
through the merging of two eccentric circles
to become concentric.

12. • A screw placed at the inclined plane moves
the plate horizontally in relation to the bone
until the screw head reaches the intersection
of the two circles.
• At this point, the screw has optimal contact
with the hole, ensuring maximal stability and
producing axial compression of the bone and
tension on the plate.

13. • The plate can be placed for depending on the insertion
of the screw
– neutralization
– compression
– buttressing,
• The DC plate can be modified for use and its use is
based on fracture pattern and location
• Certain shortcomings of the DC plate have been
discovered through the years.
– interference with the periosteal blood supply
• plate-induced osteoporosis
• sequestrum could form underneath the plate.
– a soft spot in fracture healing can occur
• possibility of refracture

14. LIMITED CONTACT DYNAMIC COMPRESSION
• Modification that attempts to correct some of the design
shortcomings of the DC plate.
• Based on work by Klaue and Perren, there are three main
differences in design.
– sides of the plate are inclined to form a trapezoidal cross section
interrupted by undercuts that form.
• reduces the area of contact between the plate and the periosteal
surface of the bone,
– the screw hole is made up of two inclined and one horizontal
cylinder
• they meet at the same angle, permitting compression in both
directions
– stress is more equally distributed
• less deformation occurs at the screw holes when contouring
• The biomechanical uses and applications of the LCDC plate
are the same as those for the DC plate.

15. Methods of achieving compression
• Self compressing plate
– Converts torque applied to the screw head to a
longitudinal force which compresses the fractured
bone ends
– Screws and plates are designed to facilitate this
conversion
• Tensioning device
– Special tensioning device can be attached the bone
plate and adjacent bone cortex
– Produce tension in the plate and compression force
across the fracture

16. • Eccentric screw placement
– Eccentric means cirlce with different centre
– Eccentric screw placement in a plate hole creates
considerable shear stress in the screw which is
transmitted to the plate and can occasionally be
used to produce interfragmental compression
– Inefficient technique, screw head may break

17. TENSION BAND
• When fuctional activity begins, physiological
force which are normally destabilizing for a
fracture, are converted to a stabilizing and
active force by the same plate, which acts as a
tension band.
• This band is used to create a small amount of
compression, which results in partial closure of
the discontinuity and compression of the
spring on the same side as the band.

18. Buttress plate
• Applies a force to the bone which
is perpendicular to the flat surface
of the plate
• Main function:
– Buttress weakened are of cortex
– Protects from collapsing during
healing process
– Designed with large surface area to
facilitate wider distribution of load
– Used to maintain bone length or
support the depressed fracture
fragment
• Commonly used in fixing
epiphyseal and metaphyseal
fracture

19. Bridging Plate
• Called bridge because its fixation is out of the
main zone of injury at the end of the plate to
avoid additional injury in comminuted zone
• Intended to maintain length and alignment of
severly comminuted and segmental fracture
• Limits devitalization of fragments and thereby
allows for a better healing enviroment

20. Condylar plate
• Has distinct mechanical function
– Maintains the reduction of main intra-articular
fragments
– Rigidly fixes the metaphyseal components to
diaphyseal shaft, permitting early movement of the
extremity
• Functions as neutralization plate as well as
buttress plate. it does act as compression plate as
well.
• Fixed angle of the plate overcomes the coronal
plane instability and prevents consequent
collapse.

21. SEMI-TUBULAR, ONE-THIRD TUBULAR, AND QUARTER-
TUBULAR PLATES
• the first AO self-compression plate designed in the shape of a half-
tube.
• It provides compression through eccentrically placed oval plate
holes.
• Semi tubular plate:
– maintains its rotational stability with edges that dig into the side of the
periosteum under tension.
– Its main indication is for tension resistance
• The one-third tubular plate
– commonly used as a neutralization plate in the treatment of lateral
malleolar fractures.
• The quarter-tubular plates
– have been used in small bone fixation (e.g., in hand surgery).

22. RECONSTRUCTION PLATE
• designed with notches in its
side so that it can be contoured
in any plane
• mainly used in fractures of the
pelvis, where precise
contouring is important
• also be used for fixation of
distal humerus and calcaneal
fractures.
• relatively low strength, further
diminished with contouring.
• offers some compression
because of its oval screw holes.

23. ANGLED PLATES
• developed in the 1950s for the
fixation of proximal and distal femur
fractures.
• They are a one-piece design with a U-
shaped profile for the blade portion
and a 95° or 130° fixed angle between
the blade and the plate.
• The shaft is thicker than the blade and
can withstand higher stress.
• The forces applied in this area exceed
1200 lb/in. with the medial cortex
exposed to compression combined
with greater stress and the lateral
cortex exposed to tension.

24. • The 130° Blade Plate
– originally designed for fixation of proximal femur
fractures
– has different lengths to accommodate different
fracture patterns.
– The 4- and 6-hole plates are used for fixation of
intertrochanteric fractures, while the 9- to 12-hole
plates are used for treatment of subtrochanteric
fractures.
– It has been replaced for the most part by the
dynamic hip screw, which allows for compression
of the fragments.

25. • The 95° Condylar Blade Plate
– designed for use with supracondylar and
bicondylar distal femur fractures
– the length employed is also fracture specific
– It can be used for subtrochanteric fractures where
more purchase on the fracture fragment can be
gained with a sharper angled plate.
– the device is strong and provides stable fixation
– The need for precise alignment in all three planes
demands careful preoperative planning and
intraoperative radiographic control.

26. LOCKING COMPRESSIVE PLATE
• General principle:
– Represents novel, bio-friendly approach to internal
fixation
– it combines the principles of conventional plate
osteosynthesis for direct anatomical reduction with
those of bridging plate osteosynthesis.
– The importance of the reduction technique and
minimally invasive plate insertion and fixation relates
to ensuring that bone viability is undisturbed.

27. • Is a symbiosis of various locking techniques of plate
osteosynthesis
• Offers a versatile, easy to use and purposeful design to
improve the surgical approach to fracture treatment
• Is a construct where screw with threaded head locked in a
threaded hole in a bone plate
• The force are transferred from the bone to the fixator across
the threaded-screw fixator connection

28. BIOMECHANICS
• Might be considered as ultimate external fixator, with
minimal soft tissue dissection, wide screw spacing, locked
screw and the plate functioning as the connecting bare,
placed extremely close to the mechanical axis of the bone.
• Locked plate controls the axial orientation of the screw to
the plate, enhancing the screw-plate-bone construct
stability by creating a single beam construct
• Single beam construct is four times stronger than load
sharing beam construct.
• Relative stability and secondary bone healing are the goals
of LCP

29. ADVANTAGES
• Preserve biological intergrity
• Resistance to infection
• Locking the screw in the fixator abolishes
– load transmission by friction,
– minimizes bone contact,
– increase stability,
– eliminates the risk of loss of reduction
• Achieving fixation in osteopenic or pathologic
bone

30. DISADVANTAGES
• Has no tactile feedback as to the quality of screw
purchase into the bone
• Can maintain fracture reduction but not to obtain it
• Locked screw will not pull the plate down on its own
• Higher rate of fracture malalignment
• Rigidity of locked screw plate construct
• Inability to alter the angle of the screw within the hole
and still achieve a locked screw
• Hardware removal is more difficult

31. SUMMARY
• The basic biomechanical functions of plates in fracture
fixation have been discussed, as well as some of the
major plate designs and examples of plates modified
for use in specific anatomic areas.
• It is important to realize that specific design features of
plates can be used to fulfill biomechanical needs based
on the particularities of the fracture.
• Research in this area continues to improve fracture
fixation techniques and instrumentation.

32. THANK YOU

33. REFERENCES
• The element of fracture fixation, 2nd Edition
• Skeletal Trauma, 4th Edition