basic principles and techniques of internal fixation of fractures

Basic Principles and Techniques of Internal Fixation of Fractures

Brett D. Crist, MD

Original Author: Dan Horwitz, MD; March 2004Revision Author: Michael Archdeacon, MD, MSE; January 2006

New Author: Brett D. Crist, MD; October 2009

“Common” Definitions of Fracture Healing

• Union– 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 HealingHigh 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

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 stabilityFigures 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

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

MULTIPLE REASONS EXIST BEYOND THESE...

Benefits of Internal Fixation

• Earlier 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 Screws

• Step 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.

Lag Screws

• 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

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 together3. 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 theplate have a slope built intoone 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 Plates

• Must have reduction and compression done prior to using locking screws– CANNOT PUT CORTICAL SCREW OR LAG

SCREW AFTER LOCKING SCREW

Locking Plates

• Increased axial stability

• It is much less likely that an individual screw will fail– But, plates can still

break

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 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

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

• 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 Techniques

• Over 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

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