G10 internal fix principles

Basic Principles and Techniques of Internal Fixation

of Fractures

Dan Horwitz, MD

Biology of Bone Healing

• Rigid Fixation - bone heals directly to bone

• Nonrigid fixation or immobilization - the body forms a fibrous matrix which transitions to cartilage, calcified cartilage, disorganized woven bone, and finally organized lamellar bone.

THE SIMPLE VERSION...


• Primary bone healing– Requires rigid internal fixation and intimate

cortical contact – Cannot tolerate soft tissue interposition– Relies on Haversian remodeling with bridging

of small gaps by osteocytes


• Secondary Bone Healing = CALLUS– Divided into stages

• Inflammatory Stage 5-14 days• Repair Stage

– Soft Callus Stage– Hard Callus Stage

• Remodeling Stage 3-24 mo

Practically speaking...

• Plates and screws = primary bone healing• Cast = callus formation• IM Rods = primarily secondary bone

healing/callus - depends on location of fracture, size of nail, quality of bone…

• Small wire/tension band = usually callus formation unless bone quality is excellent in which case rigidity may be achieved.

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...

Fracture Patterns• Lateral bending produces a transverse fracture pattern

while torsional or twisting forces produce oblique or spiral fracture patterns.

• Understanding these patterns and the inherent stability or instability of each type is important in choosing the most appropriate method of fixation

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

Clinical Examples

• Callus formation and consolidation in a distalthird tibia fracture treated in a cast.

• The central defectis asymptomatic and produces no long term problems.

Casting


Rigid Internal Fixation:Proximal Humerus

• Fixation is achieved by lagging the head to a laterally stabilized plate.

• The plate is necessary because the lateral cortex of the proximal humerus is unlikely to be adequate to support the lag screws alone.

• Extensive soft tissue dissection is required for this construct.


•The humerus represents rigidinternal fixation with a broad4.5 DC plate.

•The ulna has 2 lag screws combined with a classic tension band on the olecranon.

•The tension band represents stable but not rigid fixation

Combined Fixation Techniques


Combined techniques for rigid fixation of a distal humerus fracture

• The dual plates provide stability in two planes at the metaphyseal diaphyseal junction

• The lag screw provides reduction and stability at the articular surface.


Semi -Rigid Fixation:Proximal Humerus Fracture

• This technique utilizes small K wire fixation after impaction ofthe shaft into the head and is supplemented by a modified tension band laterally.

• Healing in this situation is achieved by both primary bone healing as well as callus formation.


Indications and Benefits of Internal Fixation

• Displaced intraarticular fracture• Axial or angulatory instability which cannot

be controlled by closed methods• Open fracture• Malreduction/interposed soft tissue• Multiple trauma• Early functional recovery

MULTIPLE REASONS EXIST BEYOND THESE...

Methods of Internal Fixation• Screws - Design• Plates - Design• Lag screw/Interfragmentary screws - COMPRESSION • Dynamic compression plating - COMPRESSION

• Neutralization plate• Buttress plate• Reduction techniques• IM Nailing

Screws• Cortical screws:

– greater surface area of exposed thread for any given length

– better hold in cortical bone

• Cancellous screws:– core diameter is less– the threads are spaced farther apart– lag effect option with partially threaded screws – theoretically allows better

fixation in soft cancellous bone.

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

Examples- 3.5 mm Plates

• LC-Dynamic Compression Plate:– stronger – 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



Examples- 3.5 mm Plates

• The plates on the right are thin, pliable and often used in the distal radius.

• Those on the are left also fairly thin and are designed for subcutaneous application in sites such as the distal, medial tibia.


Example: A Reconstruction Plate

• Both small frag (3.5mm) and large frag (4.5mm) sizes

• fairly good strength• multiplanar

contourability• often used in

acetabular fractures and about the elbow


Compression

• Fundamental concept critical for primary bone healing

• Compressing bone fragments decreases the gap the bone must bridge creating stability by preventing fracture components from moving in relation to each other.

• Achieved through lag screw or plating techniques.

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.


Screw Driven Compression Device• Requires a separate drill/screw

hole beyond the plate • Replaced by the use of DCP

plates.• Concept of anatomic reduction

with added to stability by compression to promote primary bone healing has not changed

• Currently used with indirect fracture reduction techniques


1

2


•Compression Lag Screws

• Provide stability through compression between bony fragments

• Step One: drill a pilot hole equal in size to the outer diameter of the screw selected generally perpendicular to the fracture

• Step Two: Place of a guide sleeve into the pilot hole and drilling of the far cortex with a drill equal to the core diameter of the screw

COMPRESSION - LAG SCREWS

• The screw glides through the near cortex and only engages the far side.

• When the screw engages the far cortex it compresses it against the near cortex.

• This technique must usually be supplemented by additional internal or external fixation.


Compression - Lag Screws• A functional lag screw between fragments on the left - note the

near cortex has been drilled to the outer diameter of the screw and permits compression

• The screw on the right has not been drilled to the outer diameter on the near cortex and the result is lack of compression and gap at the fracture.


Combined Plating and Lag Screw

• Compression can be achieved and rigidity obtained all with one construct.


•A classic example of inadequate fixation and stability.

•This fracture was fixed with a narrow, weak plate, insufficient cortices were engaged,and gaps were left at the fracture site.

•The unavoidable result isa nonunion.


Buttress and Antiglide Concepts

• In this model the white plate is secured by three black screws distal to the red fracture line.

• The fracture is oriented such that displacement from axial loading requires the proximal portion to move to the left.

• The plate acts as a buttress against theproximal portion, prevents it from “sliding”and in effect prevents displacement froman axial load.

• If this concept is applied to an intraarticular fracture component it is usually referred to as abuttress plate, and when applied to a diaphyseal fracture it is usually referred to as an antiglideplate.

• The bottom 3 cortical screws provide the basis for the buttresseffect.

• The top 3 screws are in effectinterfragmentary screws and the 2top screws are lag screws becausethey are only partially threaded.• Underbending the plate can be advantageous in that it can increase the force with which the plate pushes against the proximal

fragment. • NOTE: screws are placed from

distal to proximal maximizing the buttress action and aiding in reduction.

Buttress Plate


The Neutralization Plate

• The two lag screws provide compression and initial stability.

• The plate bridges the fracture and protects the screws from bending and torsional loads.


Reduction Techniques…some of the options

• Traction• Direct external force i.e. push on it• Percutaneous clamps - INDIRECT METHOD• Percutaneous K wires - INDIRECT METHOD• Minimal incision, debridement of hematoma • Incision and direct fracture exposure and

reduction- DIRECT METHOD

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 should attempt to minimize periosteal stripping and soft tissue damage.– EXAMPLE: supraperiosteal plating techniques

• The use of a pointed reduction clamps to reduce a complex distal femur fracture pattern.

• Excellent access to the fracture to place lag screws with the clamp in place

• Can be done open or percutaneously, as long as the neurovascular structures are respected.

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


JOINT SURFACE

Tension band

Tension Band Theory • The concept here is that a “band” of fixation at a distance from the articular surface can provide reduction and compressive forces at the joint. • The fracture has bending forces applied by the musculature and these forces have a component which is perpendicular to the joint/cortical surface.

• Since the tension band prevents distraction at the

cortex the force is converted to compression at the joint.

• The tension band itself essentially functions like a door hinge, converting displacing forces into

beneficial compressive forces at the joint.

JOINT SURFACE

Tension band

• 2 K-wires up the ulnar shaft 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


Intramedullary Fixation

• Generally utilizes closed 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 screws

• Reduction can be technically difficult in segmental, comminuted fractures

• Fractures in close proximity to metaphyseal flare may be difficult to control

• Open segmental tibia fracture treated with a reamed, locked IM Nail.

• Note the use of

multiple proximal interlocks where angulatory control is more difficult to maintain due to the metaphyseal

flare.

• Subtroch fracture treated with closed IM Nail.

• The goal here is to restore alignment and rotation, not to achieve anatomic reduction.

• Without extensive

exposure this fracture formed abundant callous by 6 weeks. Valgus is restored...

Summary

• Respect soft tissues• Choose appropriate fixation method• Achieve stability, length, and rotational

control to permit motion as soon as possible• Understand the limitations and requirements

of methods of internal fixation

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G10 internal fix principles