external fixation ali sarhan

By : ali sarhan

External fixation is a surgical treatment used to stabilize bone and soft tissues at a distance from the operative or injury focus. 

external fixator includes : 1. Schanz pin 2. Connecting rods 3. Clamps.

Schanz pins

Connecting rods

Indications severe open fractures

Infected fractures

Correction of extremity malalignments and length discrepancies

Initial stabilization in poly trauma patients

Closed fracture with associated severe soft tissue injuries

Severely comminuted diaphyseal and periarticular lesions

Temporary transarticular stabilization of severe soft tissue and ligamentous injuries

Pelvic ring disruptions

Certain pediatric fractures

Arthrodesis

Osteotomies

Malunion/nonunion

Advantages1. Minimally invasive

2. Flexibility (build to fit)

3. Quick application(emergency)

4. Useful both as a temporizing or definitive stabilization device

Disadvantages

Mechanical

1. Distraction of fracture site2. Inadequate immobilization3. Pin-bone interface failure4. Weight/bulk5. Refracture (pediatric femur)

Biologic

1. Infection (pin track)2. Neurovascular injury3. Tethering of muscle4. Soft tissue contracture

May result in malunion/nonunion,

loss of function

Pins Principle: The pin is to link between the

bone and the frame

Pin stiffness is determined by its diameter.Pin insertion technique respecting bone and

soft tissue

Various diameters(Commonly from 3 to 5 mm.), lengths, and designs

MaterialsStainless steelTitanium (More biocompatible , Less stiff ) .

‘Blunt’ pins- Straight

- Conical

Self Drilling

Pin coatings

Recent development of various coatings (Chlorohexidine, Silver, Hydroxyapatite)

1. Improve fixation to bone2. Decrease infection

Pin Insertion Technique1.Incise skin2.Spread soft tissues to bone3.Use sharp drill with sleeve4.Irrigate while drilling5.Place appropriate pin using sleeve

Avoid soft tissue damage , and bone thermal necrosis that created by the drilling

Pin Length

Half Pinssingle point of entryEngage two cortices

Transfixation PinsBilateral, uniplanar fixationMore stable Limited anatomic sites ( injury )

Pin Diameter GuidelinesFemur – 5 or 6 mmTibia – 5 or 6 mmHumerus – 5 mm Forearm – 4 mmHand, Foot – 3 mm

< 1/3 dia

Clamps Two general varieties:

Single pin to bar clampsMultiple pin to bar clamps

Connecting Rodsmaterials:

○ titanium○ Steel○ Aluminum○ Carbon fiber

Design○ Simple rod○ Articulated○ Telescoping

Ring Fixators

Useful for correction of: (Reconstruction)LengthAngulationrotation

MRI Compatibility Stainless steel most at risk for attraction and

heating

Titanium ,aluminum and carbon fiber demonstrate minimal heating and attraction

Almost all are safe if the components are not directly within the scanner.

Biology

Current External fixation systems have been designed to allow micromotion at the fracture site to promote callus formation

Stable yet less rigid systems of external fixation maintain alignment and length while allowing and actually encouraging beneficial micromotion

Micromotion = rigid stability

Anatomic Considerations Avoidance of major nerves,vessels and organs

(pelvis) is mandatory

Avoid joints and joint capsules Proximal tibial pins should be placed 14 mm distal to articular surface to

avoid capsular reflection

Minimize muscle/tendon impalement

Lower Extremity “safe” sites

14 mm

Upper Extremity “Safe” Sites

Humerus Proximal: axillary n Mid: radial nerve Distal: radial, median and ulnar n

Ulna: safe subcutaneous border, avoid overpenetration

Radius Proximal: avoid because radial n Mid and distal : sup. radial n.

In the upper extremity dissection is In the upper extremity dissection is recommended to avoid neurovascular injury.recommended to avoid neurovascular injury.

Conversion to Internal Fixation

Generally safe within 2-3 wks

Plates are good choice

Use with caution with signs of pin irritation (Consider staged procedure )

Extreme caution with established pin track infection

Pin-track Infection Prevention

Pins placed in subcutaneous bone borders

Pins placed away from zone of injury

Use of adequate skin incision

Use of sharp drill bits to prevent thermal necrosis

Postoperative care:

Clean implant/skin interfaceSalinegauze around pins to hold skin down to

prevent excessive motion at pin/skin interface Shower (only after wounds are healed)

Stage I: Seropurulent Drainage

Stage II: Superficial Cellulitis

Stage III: Deep Infection

Stage IV: Osteomyelitis

Pin-track Infection Treatment of Pin-track infection should consist of:

Stage I: aggressive pin-site care and oral cephalosporinStage II: +/- Parenteral AbxStage III: Parenteral Abx plus removal of pin

Stage IV: same as Stage III , culture pin site for offending organism, specific IV Abx for 10 to 14 days, surgical debridement of pin site