External skeletal fixation techniques

Shahnawaz ahmad bhat

4857

Definition

A method of fracture treatment ,that involves the percutaneous placement of a series of transcortical pins or wires , which are externally connected to a rigid frame

Indications for use Long bone fractures

Open fractures

Comminuted fractures that cannot be anatomically reconstructed

Osteomyelitis

High-energy fractures with soft- tissue injuries and vascular compromise

Cont’d........

Transarticular ESF in arthrodesis

Temporary splintage during healing of soft tissue or osseous structures

Nonunion / with bone graft

Corrective osteotomy for antebrachial /tibial growth deformities

Limb lengthening procedures

Cont’d……

Conjunction with internal fixation- in humeral, femoral or tibial fractures

Hybrid ESF system- humeral, radial or tibial fractures with very short distal or proximal fragment

Cont’d….. Mandibular or maxillary

fractures- usually with acrylic fixators

Lubosacral fractures & luxations

Avian limb fractures

Fracture repair in small exotic mammals

Advantages of ESF

Minimally invasive method, preserving blood supply & soft tissues

No implants at the fracture site Possible closed application which limits iatrogenic trauma Provides immediate wt. bearing after surgery Maintains normal joint mobility Provides optimum environment for osteosynthesis & wound

healing compatibility with internal fixation devices Technical ease of application and removal wound management in open fractures Reusability of the pin clamps & connecting bars

Disadvantages of

ESF Device must be cleaned and monitored regularly Care to prevent additional damage to

animal/device

Aftercare is more labor intensive

More rigid type II and III frames cannot be used for fractures of femur & humerus

Difficult to apply and more pain in areas of increased muscle mass

Extremely high cost

ESF FRAMES

LINEAR

CIRCULAR

HYBRID

Equipment

ESF

3 BASIC UNITS

FIXATION PINS EXTERNAL CONNECTORS

LINKAGE DEVICES

Inserted into bone To hold major

Fragments Support fractured

Bones

Attach fixation Pins & external

Connectors

FIXATION PINS : classification

on basis of implantation method

HALF PIN penetrate only one skin surface but both bone

cortices

FULL PINPanetrate one skin surface then both cortices ,and then the opposite Skin

Surface

On basis of structural design Smooth pin :

Rely on friction to remain stable in the bone

Threaded pins: Positive profile and negative profile Centrally threaded and end threaded

Positive & negative profile threaded pins

Pins in which core diameter of the threaded section is smaller than the diameter of the smooth section have negative thread profile

If the core diameter is consistent b/w smooth & threaded regions ,thread profile is positive

Positive profile transfixation pins used in ESF

Centrally threaded & End threaded pins

Centrally threaded pins are used as full pins with type ÌÌ or ÌÌÌ external fixator frames

Central threads engage bone & smooth pin ends extend beyond the skin surface

End threaded pins are described a/c to no. of cortices engaged by threads (one cortex & two cortex end threaded pins)

End treaded pin Centrally threaded

pin

External connectors

Made up of stainless steel, titanium alloy , carbon fiber,aluminium or acrylic

External fixator & linkage devices may be fashioned from acrylic for ACRYLIC -PIN EXTERNAL FIXATOR (APEF)

APEF system contains +ve profile threaded fixation pins ,packaged acrylic & sterilized acrylic column molding tubes

SK double clamp

Secur-U clamp

S K single clamp

Kirschner double clamp

Kirschner single clamp

Kirschner type linkage devices for joining fixation Pins to external connecting bars & external connecting

bars to each other.Note the larger holes for the external connecting bars & smaller holes in the bolts for

Fixation pins

Linkage devices

Linear ESF Configurations

Type Ì ,ÌÌ or ÌÌÌ configuration

TYPE Ì Configuration Utilize half pin splintage fixation pins Connecting frame placed on only one side of the

limb Unilateral constructs Classified as *type Іa (unilateral and uniplanar) *type Іb (unilateral and biplanar)

Type Ǐa (unilateral –uniplanar ) fixators

All the fixation pins & connecting frame occupy a single plane (uniplanar)

Usually applied to cranial medial surface of radius/ tibia and lateral surface of femur/ humerus

Fixation pins are half pins

Type Ǐb (unilateral -biplanar ) fixators

Applied most often to radius & tibia

For radius & tibia–one ext. bar is placed on craniomedial surface & 2nd bar on craniolateral surface

Type ǏǏ (bilateral-uniplanar ) fixators

Utilize full pin splintage fixation pins

Cannot be placed on femur/ humerus because of adjacent body wall

Applied only to radius/tibia in mediolateral plane

Maximal type ІІa & minimal type ІІb

Maximal type ІІa

Minimal type ІІb

Type ǏǏǏ(Bilateral-biplanar)fixator

Combination of type І and type ІІ

Type І and type ІІ systems placed approx. 90° to each other

Can’t be applied to femur or humerus

Indicated in very large dogs

TIE-IN CONFIGURATION Combination of ESF (type Іa or Іb) with

intramedullary pin

Increases rigidity of fracture fixation in humerus & femur as type ІІ &Type ІІІ frames cannot be applied

No. of fixation pins is limited to 2 or 3 pins above & below the fracture

Tie –in configuration

Biomechanics Fixator rigidity depends on: Type of configuration- Type ІІІ > type ІІ > type І biplanar type Іb more resistant to

cranial/caudal shear forces compared with type ІІ.

Number of used pins: at least 2 & up to 4 pins/bone segment

Diameter and design of the pins – the diameter ≤ 25 % of the bone’s diameter

The fixator rigidity by widening pin spacing within pin groups & by the distance between pin groups

The most central pin should be 1-2 cm away from the fracture line

Cont’d…..

Moving the connecting bar closer to the bone makes the pins more resistant to bending

Using a “tie-in” configuration increase significant in bending strength

Fixation pin application Preoperative planning

Patient fracture assessment

Most important principle -asceptic surgery

Injured limb suspended from hook in the ceiling Patient Draping

choose a surgical approach Delimitation of safe corridors for insertion of pins

Cont’d……..

Most proximal and distal pins inserted after a stab skin incision

Predrilling a pilot hole with slightly smaller diameter drill bit

Transfixating pins inserted by using low-speed power drill

Fracture reduced & connecting bar connected to proximal and distal pins by clamps

Clamps placed 1-2 cm away from the skin surface

Central pins are inserted above and below the fracture

Rest of needed pins inserted & bolts tightened

Postoperative management Postoperative analgesia Pin-skin interface cleaned with antiseptic

solution Incision around pins released/extended in

case of skin tension Sterile gauze sponges placed around &

b/w fixation pins Limb wrapped with vetrap (bandage

material ) Activity restricted to least walking &

physical rehabilitation

Circular External Skeletal Fixators(CESF) (Ilizarov technique)

Most recent innovation in ESF technique in dogs and cats & also in large animals.

Developed by the Russian physician Gavriil A. Ilizarov

CESF consist of a series of complete and/or incomplete external rings that are interconnected by a series of threaded rods

Cont’d…..

These are modular systems which can be assembled in numerous configurations to

stabilize fractures and arthrodeses, perform bone lengthening and transport correct angular, translational and rotational

deformities

Each ring is secured in position along the rod by placing a nut on either side of the ring

Cont’d….

Elongation of the frame allows for distraction osteogenesis in which regenerate bone is produced within the gap created when an osteotomy is distracted slowly and sequentially

“Discontinuity of a skeletal segment necessarily triggers the repair process which will continue as long as integrity of both osteogenic tissue & its vascular supply is maintained”

Traditional CFs use small diameter wires, rather than pins, as fixation elements

Standard circular fixator frame for fracture management

Bones can be lengthenedby streching a corticotomy

1mm a day The regenerate is composed of Microcolumns originating from

both bone ends

Radiograph of distraction Callus at 3 wks

Regenerated bone appears in the trailing pathway of a

distracted bone segment in the dog treated with bone resection

& distraction osteogenesis

Equipment

Wires Rings Wire fixation bolts Threaded rods Nuts Wire tensioner &

wrenches

Wires :

1.0,1.2 or1.5mm diameter used in cats/ dogs Olive wires- wires with a bead positioned

midway along the wire Provide interfragmentary compression &

increase stability of frame construct more the no. of fixation wires- more stability

of fixation Wire angles < 45°should be avoided

Olive wires

Rings

Partial ring & full ring Five–eighth/stretch ring are used when rings

would limit joint motion (elbow/stifle) Partial rings -versatile Full rings -more available holes for rods &

wire, not versatile ring diameter , axial stiffness, torsional &

bending stiffness Smallest ring allowing ≥2 cm distance b/w skin

& inner circumference of ring selected

Wire fixation bolts Cannulated wire fixation bolts –allow wire

passage via a concentrically placed hole at base of bolt head

Slotted wire fixation bolts have an eccentric slot located under the bolt head & parallel to its long axis

Wire must be fixed without deformation

Frame construction Threaded rods used to connect rings & form

frame

Telescopic rods- hollow rods used as supports & connecting elements of ring

Frames are constructed so that one ring & its wires are placed at proximal end and another ring & its wires are placed at distal end of long bone

2 additional rings placed so that their wires panetrate proximal & distal bone segments close to the fracture

Wire tensioner

Hybrid External Fixator

Combination of a ring & a linear fixator

Indicated for fractures with juxtaarticular bone segments

May be applied to radius,tibia,femur & humerus

Can also be used to stabilize corrective osteotomies for angular limb deformities

Larger transfixation wires can be combined with the

use of rings & wires in a Hybrid frame

Clinical Applications of ESF

Fracture fixation Radial & tibial

Humeral & femoral Mandibular & maxillary

Stabilization of spinal fractures & luxations Arthrodesis Bone lengthening Bone transport for bone defects Angular limb deformity correction

Fixation of spinal fractures & luxations

Spinal arch external fixator components developed for spinal stabilization

Fluoroscopically guided percutaneous pin placement can be performed when applying external skeletal spinal fixation

Bone transport (limb salvage)

Method by which one or two segments of normal bone adjacent to a defect are slowly transported into the defect while new bone forms in the distraction pathway

Used in dogs with radial/tibial neoplasia or severe osteomyelitis with bone loss

A segment of bone is created with a corticotomy made 2-3 cm from one end of one of the main fragment

Acrylic external fixation

Acrylics are commonly used for the repair of fractures

The acrylic column acts as both the connecting rod and transfixation pin-gripping device Dental acrylic or hoof repair acrylic are suitable It can be moulded over pins after curing to a dough stage Acrylic ESF offers the advantage of reduced cost , improved versatility & simplified application

technique when compared with kirschner ESF

Advantages of acrylic system

Ability to contour the connecting bar to match any fracture configuration

Fixation pins of any diameter may be used

Fixation pins do not have to be in the same longitudinal plane

Light in weight encouraging earlier return to function

cont’d…… Placing the

positive profile threaded pin without the difficulties of passing them through clamps

Inexpensive system

Uses of acrylic fixators

Fixation of mandibular & maxillary fractures

Fixation of long bone fractures

Primary fixation device or intra-oral splint for mandibular & maxillary frcatures

Complications of ESF

Pin tract infection Focal osteomyelitis Ring sequestrum Premature pin loosening Instability at the fracture site Pin breaking Pin tract osteolysis Pressure necrosis of skin Iatrogenic bone fracture soft tissue impalement