Seminar on Basic principles relating to Bone Plates. Required for every Orthopedic PG resident.

1. BONE PLATES
PRESENTER- DR. SYED MOHAMMED ADNAN
MODERATORS :
SR - DR. KULDEEP RATHOR
CONSULTANT - DR. SANDEEP KUMAR YADAV
AIIMS JODHPUR

2. Absolute stability
• "Surfaces of the fracture do not displace under functional load"
• Can only be achieved by interfragmentary compression
• 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]

3. 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.

4. BONE PLATES INTRODUCTION
• In 1958, the AO formulated four basic principles which have
become guideline for internal fixation
1. -ANATOMICAL REDUCTION
2. -STABLE FIXATION
3. -PRESERVATION OF BLOOD SUPPLY
4. -EARLY ACTIVE MOBILIZATION

5. 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 (DCP) was developed.
• In 1994 LC DCP was created.
• In 2011 LCP with combination holes
(Combi-hole) has come into use.

6. INTRODUCTION
Like an internal splints holding together the fractured end of a bone
・ General principle - anatomical reduction and stable internal
fixation.
• Two mechanical functions-:
-Transmits force from one end to another bypassing fracture area
-Holds the fracture ends while maintaining alignment of the fragments

7. CLASSIFICATION
• Shape of the plate (semitubular, 1/3rd tubular 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 – Regional Plates -
(Clavicle,acetabular,olecranon, DER)

8. ACCORDING TO FUNCTION
1. Neutralization plate
2. Buttress plate
3. Bridging plate
4. Condylar plate
5. Tension plate
6. Compression plate

9. 1. NEUTRALIZATION PLATE
Transmits force from one end to another bypassing the fracture site
• Function - mechanical link between healthy segment of bone above
and below fracture
• Does not produce compression
• Used In combination with lag screw.

10. Clinical application
-To protect the screw fixation of a short oblique fracture
-Butterfly fragment fractures
-Mildly comminuted fracture of long bone
-Fixation of segmental bone defect in combination with bone graft.
Both DCP and LCP can be used to achieve this mode

11. The Neutralization Plate
It is crucial to use a plate that
is long enough so that at least
three bicortical screw can
be inserted into each main
fragment.

13. 2. BUTTRESS PLATE
• Means to strengthen (buttress) a weakened area of cortex The plate
prevents the bone from collapsing during the healing process.
Applies a force to the bone which is perpendicular to the flat surface of the
plate
• Main function:
1. -Buttress weakened area of cortex
2. -Protects from collapsing during healing process
3. -Designed with large surface area to facilitate wider distribution of load
4. -Used to maintain bone length or support the depressed fracture
fragment
• Commonly used in fixing epiphyseal and metaphyseal Fracture

14. • -T,L or hockey shaped plates are used
• -Plate force is perpendicular to the offset
of bone
• -The first screw lies closest to the fracture
site on shaft hence it will firmly anchors
the main Fragment of plate to the bone

15. 3. 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 severely comminuted and segmental fracture
• Limits devitalization of fragments and thereby allows for a better healing environment
(minimal disruption to blood supply )
-DCP and LCP are used .
- Plate length should be at-least 3 times the length of the fracture (PSW/PSR – 3:1)
- It provides relative stability, and Indirect(secondary) bone healing occurs with callus
formation

17. CONDYLAR PLATE
• Has distinct mechanical function
-Maintains the reduction of main intra-articular fragments – restores
anatomy of joint surface
-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 (Since the plate can be attached to a tensioning
device and has specially designed screw holes).
• Fixed angle of the plate overcomes the coronal plane instability and
prevents consequent collapse.

19. TENSION BAND PLATING
Based on Frederic Pauwels observation that a curved,
tubular structure under axial load always has a
compression side as well as a tension side.
-Under vertical pressure the curved femur creates a
tension force laterally and a compression force
medially.
-A plate positioned on the side of tensile forces
neutralizes them at the fracture site provided there
is cortical contact opposite to this plate.
In this case of a cortical defect, the plate will undergo
bending stresses and eventually fail due to fatigue.

20. Prerequisites of tension band fixation
● Bone which is able to withstand compression
● An intact buttress of the opposite cortex
● A strong plate to withstand the tensile forces
● Plate placement on the tension side of the bone
‘A bone plate will act as a tension band only if it is
applied to the tension side of a bone’

22. COMPRESSION PLATE
Produce locking force across 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 produced, as a reaction to this tension,
compression is produced at the fracture site.
-It produces compression across fracture site. If the fracture is reduced
anatomically; plate partially shares the load until fracture heals finally fracture
united
-DCP and LCDCP are used for this mode

23. COMPRESSION
• 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.

24. METHODS OF ACHIEVING COMPRESSION
• With tension devise
• By overbanding
• With dynamic compression principle (DCP/LC-DCP)
• By contouring plate
• Additional lag screw through plate

25. Application of the articulated tension
device
• In oblique fractures the tension
device must be applied in such a
way that the loose fragment locks
in the axilla if compression is
produced, demonstrates the
tension device applied in the
wrong position

26. COMPRESSION WITH OVERBANDING
□ If a straight plate is tensioned on a straight bone,
a transverse fracture gap will open up due to the
eccentric forces acting on the opposite side.

27. DYNAMIC COMPRESSION 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

28. DYNAMIC COMPRESSION PLATE
• Two basic advantages :
-independent axial compression
-the ability to place screws at different angles of inclination.

29. Plate application :
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.

30. After insertion of one compressing screw, it is only possible to
insert one further screw with compressing function in the same
fragment.
Movement of the plate pushes the first compression screw
against the side of the screw hole and prevents further
movement.
When the second screw is tightened, the first has to be
loosened to allow the plate to slide on the bone, after which it is
retightened.

31. • Screw holes allow 1mm
compression
• Additional compression with 1
more eccentric screw before
locking first screw

32. • The oval shape of the
holes allows 25°
inclination of the screws
in the longitudinal plane,
and up to 7° inclination in
the transversal plane

33. ・ The plate can act any of the following 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

34. DCP DISADVANTAGES
・ 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

35. LIMITED CONTACT DYNAMIC COMPRESSION (LC DCP)
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.
1 -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,
2 -the screw hole is made up of two inclined and one horizontal cylinder
• they meet at the same angle, permitting compression in both directions
3 -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.

36. SEMI-TUBULAR, ONE-THIRD TUBULAR.
AND QUARTERTUBULAR 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).

38. 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

40. ANGLED PLATES
・ Developed in the 1950s for the fixation of proximal and distal femur fractures.
• They are a one-piece design with a U-shape 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 Ib/in. with the medial cortex
exposed to compression combined with greater stress and the lateral cortex
exposed to tension.

41. 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.

42. 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 sub-trochanteric 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.

43. REGIONAL
PLATES

44. PLATE BIOMECHANICS

45. STRESS AND STRAIN IN RELATION TO BONE AND IMPLANT
STRESS RISER
-Stress is an internal force which resist deformation
-At a point where this stress is reasonably higher those points are called Stress Risers
-Ex- angulation of bone , holes in plates , grooves, bone screw interface, end of plates
-These stresses weakens the bone part and may lead to fracture e.g. fracture near callus,
fracture at the end of plates etc.

46. STRESS SHIELDING
-When a implant is loaded specially with wt bearing implant, it
produces osteopenia of bone just beneath the implant.
-This effect is called stress shielding
-This occurs because-
when static forces at bone implant interface is lesser than
loading forces , it leads to micro motion at bone implant interface
and finally osteopenia of underlying bone

47. PERREN STRAIN THEORY
When the fractured bone is immobilized, the relative movement of two fragments depends
upon
-Stiffness of implant
-Magnitude of external loading
-Stiffness of bridging calluses
Capacity to tolerate the deformation of calluses at fracture site varies acco to nature of
healing at fracture site, this deformation or strain is expressed in percentage
-strain - 2% ; healing by primary intention
-strain 2-10%; healing by secondary intention -Strain 10-30% ; threshold level for healing

48. PLATE CORTICES
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

49. PLATE SPAN RATIO AND PLATE SCREW DENSITY

51. STRESS AND PULL OUT FORCE

52. TO SUMMARISE

53. References
• AJ Thakur Principles of Fixation
• Campbell Operative Orthopaedics
• AO Principles of Fracture Fixation

54. THANK YOU