Basic Principles and Techniques of Internal Fixation of Fractures

Dr Terence Tay !

“Common” Definitions of Fracture HealingUnion

▪Bone’s mechanical stability restored to withstand normal loads ▪ Clinically: no pain at fracture site ▪ Radiographically: 3 out of 4 cortices with bridging callus

Delayed Union

▪Fx not consolidated at 3 months, but progressive callus Non Union

▪No improvement clinically or radiographically over 3 consecutive months ▪A fibrocartilaginous interface

From: OTA Resident Course – Russel, T

High Energy vs. Low Energy

“High Energy" ▪Direct axial load or bending force ▪Fall from height/Motor vehicle crash ▪Soft tissue envelope significantly damaged ▪Comminuted fracture patterns ▪Open fractures “Low Energy“ ▪Twisting mechanism or direct load on

weak bone ▪Fall from standing ▪Less soft tissue injury ▪Simple fracture pattern

“High Energy"

“Low Energy"

Fracture Patterns

Fracture patterns occur based on mode, magnitude and rate of force application to bone

▪Bending Load → transverse fx with wedge segment ▪3-point Bend →Wedge fragment ▪4-point Bend → Segmental fragment

▪Torsional Load → oblique or spiral fx ▪Axial Load → Articular impaction (Plateau, Pilon, etc.)

Fracture Patterns

Understanding these patterns and the inherent stability of each type is important in choosing the most appropriate method of fixation and surgical approach

High Rate of Healing

Spectrum of Healing

Absolute Stability =10 Bone Healing

Relative Stability =20 Bone Healing

Biology of Bone Healing

THE SIMPLE VERSION...

Fibrous Matrix > Cartilage > Calcified Cartilage > Woven Bone > Lamellar Bone

Haversian Remodeling

Minimal Callus

Callus

Biology of Bone Healing

Direct/Primary bone healing ▪Requires rigid internal fixation and

intimate cortical contact –absolute stability ▪Minimal callus formation ▪Cannot tolerate fracture gap ▪Interfragmental compression will

minimize fracture motion ▪Relies on Haversian remodeling with

bridging of small gaps by osteocytes (cutting cones)

Figure from: OTA Resident Course - Russel

Biology of Bone Healing

Indirect/Secondary Bone Healing = CALLUS

▪ Divided into stages ▪ Inflammatory Stage ▪ Repair Stage

▪Soft Callus Stage ▪Hard Callus Stage

▪ Remodeling Stage 3-24 mo

▪ Relative stability

Figures from: OTA Resident Course - Russel

Practically speaking...

Primary/Direct Bone Healing

Simple fracture patterns

See the fx during surgery and directly reduce and fix with:

▪Lag screws

▪Plates and screws

Secondary/Indirect Bone Healing

Complex fracture patterns

Don’t directly see the fracture during surgery (use fluoro)

Indirectly reduce the fx and fix with:

▪IM Rods

▪Bridge plate fixation

▪External fixation

▪Cast

Relative Stability !!!!!!!!Absolute Stability

– IM nailing – Ex fix – Bridge plating –Cast

– Lag screw/ plate

– Compression plate

Fixation Stability

Absolute

(Rigid)

Relative

(Flexible)

Spectrum of Stability

Cast

IM Nail

Compression Plating/ Lag screw

Ex Fix

Bridge Plating

Practically speaking….Most fixation probably involves components of both types of healing. Even in

situations of excellent rigid internal fixation one often sees a small degree of callus formation...

Relative (Rigid)Absolute

(Flexible)

No callus

Fixation Stability

Callus

Reality

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

Functions of Fixation

*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

MULTIPLE REASONS EXIST BEYOND THESE...

Benefits of Internal FixationEarlier functional recovery !More predictable fracture alignment !Potentially faster time to healing

Screws• Cortical screws:

–Greater number of threads –Threads spaced closer together (pitch is (smaller pitch) –Outer thread diameter to core diameter ratio is less –Better hold in cortical bone !

• Cancellous screws: – Larger thread to core diameter ratio –Threads are spaced farther apart (pitch is greater) – Lag effect with partially-threaded screws – Theoretically allows better fixation in cancellous bone

Figure from: Rockwood and Green’s, 5th ed.

Lag Screw Fixation

Screw compresses both sides of fx together ▪ Best form of compression ▪ Poor shear, bending, and rotational force resistance

Partially-threaded screw (lag by design) Fully-threaded screw (lag by technique)

1

2

Figure from: Schatzker J, Tile M: The Rationale of Operative Fracture Care. Springer-Verlag, 1987.

Lag Screws• “Lag by technique”

• Using fully-threaded screw

• Step One: Gliding hole = drill outer thread diameter of screw & perpendicular to fx !

• Step Two: Pilot hole= Guide sleeve in gliding hole & drill far cortex = to the core diameter of the screw

Lag ScrewsStep Three: counter sink near cortex so screw head will sit flush

Step Four: screw inserted and glides through the near cortex & engages the far cortex which compresses the fx when the screw head engages the near cortex

Figure from: Schatzker J, Tile M: The Rationale of Operative Fracture Care. Springer-Verlag, 1987.

Functional Lag Screw - note the near cortex has been drilled to the outer diameter = compression

Position Screw - note the near cortex has not been drilled to the outer diameter = lack of compression & fx gap maintained

Lag Screws

Figure from: OTA Resident Course - Olsen

Lag Screws!

• Malposition of screw, or neglecting to countersink can lead to a loss of reduction

• Ideally lag screw should pass perpendicular to fx !

Neutralization Plates

Neutralizes/protects lag screws from shear, bending, and torsional forces across fx

“Protection Plate"

Figure from: Schatzker J, Tile M: The Rationale of Operative Fracture Care. Springer-Verlag, 1987.

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

• 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.

Antiglide/Buttress Concepts

Plate is secured by three black screws distal to the red fracture line

Axial loading causes proximal fragment to move distal and to the left along fracture line

Plate buttresses the proximal fragment • Prevents it from “sliding”

Buttress Plate ▪ When applied to an intra-articular fractures

Antiglide Plate ▪ When applied to diaphyseal fractures

Bridge Plates

“Bridge”/bypass comminution

Proximal & distal fixation Goal: ▪Maintain length, rotation, & axial

alignment Avoids soft tissue disruption

at fx = maintain fx blood supply

Tension Band Plates

Plate counteracts natural bending moment seen w/ physiologic loading of bone

▪Applied to tension side to prevent “gapping” ▪Plate converts bending force to compression ▪Examples: Proximal Femur &

Olecranon

JOINT SURFACE

Tension band

Tension Band Theory • The fixation on the opposite side from the articular surface provides reduction and

compressive forces at the joint by converting bending forces into compression • The fracture has tension forces applied by the muscles or load bearing

Load applied to bone

The tension band prevents distraction and the force is converted to compression at the joint

The tension band functions like a door hinge, converting displacing forces into beneficial compressive forces at the joint

JOINT SURFACE

Tension band

Load applied to bone

• Wires can be used for tension band as well • Ex: Olecranon and patella

• 2 K-wires from tip of olecranon across fx site into anterior cortex to maintain initial reduction and anchor for the tension wire !

• Tension wire brought through a drill hole in the ulna !

• Both sides of the tension wire tightened to ensure even compression !

• Bend down and impact wires

Classic Tension Band of the Olecranon

Figure from: Rockwood and Green’s, 4th ed.

Compression Plating

Reduce & Compress transverse or oblique fx’s

▪Unable to use lag screw ▪Exert compression across

fracture ▪Pre-bending plate ▪External compression devices

(tensioner) ▪Dynamic compression w/ oval

holes & eccentric screw placement in plate

Examples- 3.5 mm Plates

LC-Dynamic Compression Plate:

▪ stronger and stiffer ▪more difficult to contour. ▪ usually used in the treatment

radius and ulna fractures

Semitubular plates: ▪ very pliable ▪ limited strength ▪most often used in the treatment of

fibula fractures

Figure from: Rockwood and Green’s, 5th ed.

Figure from: Rockwood and Green’s, 5th ed.

Compression

Fundamental concept critical for primary bone healing Compressing bone fragments decreases the gap and maintains the bone position even when

physiologic loads are applied to the bone. Thus, the narrow gap and the stability assist in bone healing.

Achieved through lag screw or plating techniques.

Plate Pre-Bending Compression

Prebent plate ▪A small angle is bent into the plate centered at the fracture ▪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

Plate Pre-Bending Compression

Screw Driven Compression Device

Requires a separate drill/screw hole beyond the plate

Concept of anatomic reduction with added stability by compression to promote primary bone healing has not changed

Currently, more commonly used with indirect fracture reduction techniques

Figure from: Schatzker J, Tile M: The Rationale of Operative Fracture Care. Springer-Verlag, 1987.

Dynamic Compression Plates

• Note the screw holes in the plate have a slope built into one side. !• The drill hole can be purposely

placed eccentrically so that when the head of the screw engages the plate, the screw and the bone beneath are driven or compressed towards the fracture site one millimeter.

!

This maneuver can be performed twice before compression is maximized.

Figure from: Schatzker J, Tile M: The Rationale of Operative Fracture Care. Springer-Verlag, 1987.

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 can be achieved and rigidity obtained all with one construct

Compression plate first

Then lag screw placed through plate if fx allows

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 PlatesMust have reduction and compression done prior to using locking screws ▪ CANNOT PUT CORTICAL SCREW OR LAG SCREW AFTER LOCKING

SCREW

Increased axial stability

It is much less likely that an individual screw will fail

▪But, plates can still break

Locking Plates

Locking Plates

Indications: ▪ 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 (i.e. allow axial loading of fracture with weight bearing).

Secondary bone healing Diaphyseal and some

metaphyseal fractures

Intramedullary FixationGenerally 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

Rotational and axial stability provided by interlocking bolts

Reduction can be technically difficult in segmental and comminuted fractures

Maintaining reduction of fractures in close proximity to metaphyseal flare may be difficult

Intramedullary Fixation

• 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...

Reduction Techniques…some of the options

Indirect Methods

Traction-assistant, fx table, intraop skeletal traction

Direct external force i.e. push on it

Percutaneous clamps Percutaneous K wires/

Schantz pins—”Joysticks”

External fixator or distractor

Direct Methods

Incision with direct fracture exposure and reduction with reduction forceps

Reduction TechniquesOver the last 25 years the biggest change regarding ORIF of fractures has probably

been the increased respect for soft tissues. Whatever reduction or fixation technique is chosen, the surgeon must minimize

periosteal stripping and soft tissue damage. ▪ EXAMPLE: supraperiosteal plating techniques

• Pointed reduction clamps used to reduce a complex distal femur fracture • Open surgical approach • Excellent access to the fracture to place lag screws with the clamp in place • Remember, displaced articular fractures require direct exposure and reduction

because anatomic reduction is essential

Direct Reduction Technique

• Place clamp over bone and the plate • Maintain fracture reduction • Ensure appropriate plate position proximally and distally with respect to the bone, adjacent joints, and neurovascular structures • Ensure that the clamp does not scratch the plate, otherwise the created stress riser will weaken the plate

Reduction Technique - Clamp and Plate

Figure from: Rockwood and Green’s, 5th ed.

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

Figure from: Schatzker J, Tile M: The Rationale of Operative Fracture Care. Springer-Verlag, 1987.

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