principles of internal fixation
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Transcript of principles of internal fixation
PRINCIPLES OF INTERNAL FIXATION
» DR MANU MATHEW» MODERATOR DR GAURAV SHARMA
• Historical Background• Preoperative Planning• Fracture Reduction• Techniques and Devices for Internal Fixation
Historical Background
• First reports on modern techniquesof internal fixation are only about 100 years old.
• Elie and Albin Lambotte “osteosynthesis” offractures with plates and screws, wire loops and
external fixators
Robert Danis (1880to 1962) introduced the term of “soudure autogéne
Maurice Müller was impressed by DANIS &founded the Arbeitsgemeinschaftfür Osteosynthesefragen (AO)
Gerhard Küntscher(1900 to 1972) in Germany had developed the technique of IMnailing,
• GOAL OF OPERATIVE FRACTURE FIXATION
• full restoration of function
• faster return to his preinjury status• • minimizethe risk and incidence of
complications.
• Predictable alignment of fracture fragments
The purpose of implants
to provide a temporary support
to maintain alignment during the fracture healing
to allow for a functional rehabilitation
Biology and Biomechanics onFracture Healing
fractured bone needs - a certain degree of immobilization -optimally preserved blood supply
-biologic or hormonal stimuli in order to unite.
Soft Tissue Injury and Fracture Healing
“every fracture is a soft tissue injury, where the bone happens to bebroken,”
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
mechanical stability,
Absolute stability
rigid fixation that doesnot allow any micro motion
elastic fixation
provided by internal or external splintingof the bone
High Rate of Healing
Spectrum of Healing
Absolute Stability =10 Bone Healing
Relative Stability =20 Bone Healing
Biology of Bone HealingTHE SIMPLE VERSION...
Fibrous Matrix > Cartilage > Calcified Cartilage > Woven Bone > Lamellar Bone
Haversian Remodeling
Minimal Callus
Callus
Absolute
(Rigid)– eg Lag screw/ plate– Compression plate
Relative– (Flexible) – eg– IM nailing
– - Bridge plating
0
No callus
Fixation Stability
Callus
Reality
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
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
The components of a preoperative plan• Timing of surgery• Surgical approach• Reduction maneuvers• Fixation construct• Intraoperative imaging• Wound closure/coverage• Postoperative care• Rehabilitation
Prophylactic Antibiotics
• In general a second generation cephalosporinwith 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
Fracture Reduction
• The goal of reduction is to restore the anatomical relationship
Direct Reduction
• Direct reduction – fragments are manipulated
directly by the application of different instruments or hands, via open exposure of the fracture
•
joysticks
Collinear reduction clamp
Reduction Forceps provide an excellent purchase onthe fragments without stripping or squeezing the periosteumEG WEBERS FORCEPS
ADVANTAGES
precise restorationof anatomy;
DISADVANTAGES
1 more interference with bone and soft tissue biology.
2 higher risk of infection and
3 possibly a delay in bony union
Open Reduction
• Open reduction implies that the fracture site is exposed, allowing to watch and inspect the adequacy of reduction with our eyes.
Indications for open reduction
1 Displaced articular # with impaction of the joint surface
2 #which require exact axial alignment (e.g., forearm #, simple metaphyseal #)
3 failed closed reduction due to soft tissue interposition
4 Delayed surgery where granulation tissue or early callus has to be removed
5 high risk for neurovascular structures6 no or limited access to perioperative imaging tocheck reduction
Indirect reduction
• Indirect reduction means that the reduction and alignment of the # by applying reduction forces indirectly
• via the soft tissue envelope—to the main fragments by manual Or skeletal traction, a distractor, or some other means.
• classical example of indirect reduction is the “closed” insertion
• of an intramedullary nail on a fracture table
The distractor
Indirect reduction
ADVANTAGES virtually NO exposure of the fracture site ;
LESS damage to the vascularity of the tissue
DISADVANAGES1demandingtechnique and that 2the correct overall alignment of the fracture is more difficult to assess, especially in rotation
Closed Reduction
• Closed reduction relies entirely on indirect fragment alignment by ligamentotaxis or the pull of the soft tissue envelope
• Traction is the most common means to reduce a fracture
– D/A applied across a joint and that there are limited possibilities to move the limb.
Eg The fracture table
The distractor
offers many possibilities and more freedom of movement•D/Aquite demanding to manipulate and requires considerable practice
advantages of closed reduction
• minimal damage to soft tissues• safer• more rapid fracture repair • lesser infection.
Indications for closed reduction
• Most diaphyseal fractures • • Minimally displaced articular fractures.• Geriatric femoral neck fractures,
trochanteric fractures, subcapital humerus fractures, and certain distal radius fractures
Techniques and Instruments for Fracture Reduction
Screws
• The two basic principles of a conventional screw are
• to compress a fracture plane (lag screw) and
• to fix a plate to the bone (plate screw)
• 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
–Size1-4.5mm diameter
–Self tapping ,cannulated etcFigure from: Rockwood and Green’s, 5th ed.
•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
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 lockingscrews within the plate hole to address specific fractureconfigurations
LAG SCREW
Positioning Screw a fully threaded screw that joins two anatomical parts at a defined distancewithout compression. The thread is therefore tappedin both cortices.example is a screw placed between fibulaand tibia in a malleolar fracture
Plates• Conventional non locked screws used to fix a plate to the
bone plate is pressed against the bone
which produces preload and friction between the two surfaces.
• #forearm bones ,• simple metaphyseal fractures of long bones, malunion and nonunions,
D/A local cortical necrosis
HISTORY OF PLATES
• Early modern plates - round holes the conical--firm fit
the dynamic compression• plate (DCP) by Perren
. spherical screw head and an inclined oval screw hole
•Angle blade plates tubular plates,•reconstruction plates, the sliding hip screw and dynamic condylar
•LC-DCP (limited contact-•DCP)
THE FIVE FUNCTIONS OF PLATING
• Neutralization or protection• Compression• Buttressing• Tension band function• Bridging
Neutralization Plates
• Neutralizes/protects lag screws from shear, bending, and torsional forces across fx
• “Protection Plate"
Buttress / Antiglide Plates• “Hold” the bone up• Resist shear forces during axial loading – Used in metaphyseal areas to
support intra-articular fragments• Plate must match contour of bone to
truly provide buttress effect• Buttress Plate– When applied to an intra-articular
fractures • Antiglide Plate– When applied to diaphyseal
fractures
• 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.
Bridge Plates
• “Bridge”/bypass comminution
• Proximal & distal fixation• Goal:– Maintain length, rotation, &
axial alignment
• Avoids soft tissue disruption at # = maintain # blood supply
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
Plate Pre-Bending Compression• Prebent plate– A small angle is bent into the
plate centered at the #– The plate is applied– As the prebent plate compresses
to the bone, the plate wants to straighten and forces opposite cortex into compression
– Near cortex is compressed via standard methods• External devices as shown• Plate hole design
Screw Driven Compression Device
• Requires a separate drill/screw hole beyond the plate
• Currently, more commonly used with indirect fracture reduction techniques
Dynamic Compression Plates
•
Dynamic Compression Plating
• Compression applied via oval holes and eccentric drilling– Plate forces bone to
move as screw tightened = compression
Lag screw placement through the plate
• Compression + rigidity obtained a with one construct
• Compression plate first
• Then lag screw placed through plate
Figure from: Rockwood and Green’s, 5th ed.
Locking Plates• 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
Locking Plates• Increased axial stability• It is much less likely
that an individual screw will fail
• But, plates can still breakIndications:– Osteopenic bone– Metaphyseal fractures
with short articular block
– Bridge plating
Intramedullary Nails• Relative stability• Intramedullary splint• Less likely to break with
repetitive loading than plate
• More likely to be load sharing .
• Secondary bone healing• Diaphyseal and some
metaphyseal fractures
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
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
• 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.
• 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...
Percutaneous Plating
• Plating through modified incisions– Indirect reduction
techniques– Limited incision for:
• Passing and positioning the plate
• Individual screw placement
– Soft tissue “friendly”
•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
Summary
• Respect soft tissues• Choose appropriate fixation method• Achieve length, alignment, and rotational
control to permit motion as soon as possible• Understand the requirements and
limitations of each method of internal fixation
Thankyou