There are two types of bone fixation

Internal fixation and external fixation

 Internal fixation see here
External fixation

Are those where the mechanical strength of the construct is outside the skin or fixation of fracture outside the skin

Is an alternative way to holding a fracture is to insert pins and wires into the bone on each side of the fracture, and to attach these to an external frame that provides the structural integrity

 Fixators can be as simple as a set of pins incorporated into a plaster through single- and double-bar fixators or as complex as ring fixators holding the bone through tension wires

There is a trade-off between cost, ease of fitting, adjustability rigidity and convenience to the patient

The choice of fixator will depend on what is available and the use to which it is to be put

 The llizarov fixator tensions wires onto an external ring ,wires are easy and safe to introduce, tend not to get infected and are then very strong in tension

Advantages of external fixation

• Minimally invasive

• Can be used when soft tissue cover is compromised

• Allows early mobilisation

• Can be adjusted later

Uses of an external fixator

Emergency use of the external fixator especially in fracture pelvis

Fixators are used for two main reasons in an emergency
Pelvic fractures They can be used to stabilise an unstable pelvic fracture to try to reduce life-threatening haemorrhage from the pelvic veins

 Closing and stabilising an open pelvis fracture may reduce bleed­ing by reducing movement of the pelvic veins this may stabilize clots and reduce haemorrhage

Closing the pelvis may increase the intrapelvic pressure and tamponade the veins to reduce bleed­ing

A bar fixator attached to pins inserted into the pelvic wings will need to be used The bar should be set as low as possible to give enough room over the abdomen should a laparotomy be needed

Neurovascular compromise
If a limb has an unstable fracture and has lost its blood supply the skeleton needs to be stabilised before the vascular repair can be performed one option is to insert a stent and provide a temporary blood supply to the limb while a definitive orthopaedic fixation is performed an alternative is to use an external fixator that can be applied quickly to stabilise the

So that the vascular surgeon can start work with the min­imum of delay

 The disadvantage of this approach is that an exter­nal fixator may not be the optimal way of stabilising that particular fracture, but once it has been applied the risk of infec­tion from the pin tracks makes a conversion to a plate or an intramedullary nail potentially risky.

Non-emergency use of the external fixator

Soft-tissue damage If there is extensive damage to the soft tissues then it may not be possible to achieve good cover of the bone

 If bone is contaminated and/or exposed internal fixation may not be advisable, in these circumstances an external fixator may offer the best option

The position of the pins can be planned with the plas­tic surgeons to enable them to rotate flaps without the fixator or the pins getting in the way

Leg lengthening and correction of deformity
 It is one of the great advances in orthopaedics has been the discovery that bones can be lengthened gradually

Callostasis Segments of bone can be moved across defects and, if the periosteum is left as intact as possible, new bone will be laid down in the defect - bone transport

In order for the pins of the fixator to be able to move through the soft tissues as the bones move they need to be very thin, and it is now routine to use wires which gain their rigidity by being tensioned on a ring by the Ilizarov technique

 The key to the tech­nique is to move the bone so slowly that new bone can be laid down in its track, but not so slowly that the bone unites and prevents any further distraction

 The fixation pins must be positioned to avoid damaging vital structures as they carve through the soft tissues

Care must also be taken to avoid overstretching nerves and vessels, and to avoid contractures caused by liga­ments, tendons and muscles failing to extend in concert with the bone

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