Patient information
These pages reflect general information on external fixators. They are not
designed to replace a patient physician consultation.
Fine wire external fixatours
Fine wire external fixatours are used for:
- Fractures (brakes) of long bones (vast
majority) mainly with compromised soft tissues (skin, muscles,…)
- Infections of bone where fragments are healed
(infected acute fracture – vast majority of cases are open fractures
with severe contamination of wound and bone fragments, infected
non-unions)
- Extremity deformity correction mainly where
deformity is not mendable in one attempt during surgical
intervention but has to be done during prolonged period of time
- Limb lengthening (or rarely limb shortening)
what can be a result of either trauma to the extremity with not
properly mended bones or can be congenital (present from birth).
Principles of application of fine wire
External Fixatours
Fine wires are used to attached rings (half, 2/3 or
full circumference) to affected extremity. Usually we use 1.8mm
stainless steel wires with or without olive (olive is used to either
prevent bone fragment to move or to pull a bony fragment) on one side of
the wire.
Wires are than attached to the rings with different
types of bolts (usually slotted ones).
When wire is attached on one side of the ring,
tension is applied on wire with special device where tension can be
delivered in controlled way (exact Nm per wire).Usually we go for 1000Nm
in range 900Nm to 1100 Nm. Less than 900 Nm doesn’t stabilise the wire
enough, when above 1100Nm can not be retained due to friction force
limitation which can be applied between wire and frame with slotted
bolts.
When wires don’t fit directly to the rings before
tensioning, different augments or extensions can be used.
Sometimes wires can be augmented with half pins,
which are mainly used in diaphyseal part of bone. They can be
hydroxyapatit coated to improve longetability of stability of half pin
in the bone and prevent loosening of pin comparing to non-coated ones.
Half pins are attached to the rings with specially designed bolts and
screws, but are not tensioned.
Rings belonging to the same bone fragment are
connected together either by threaded rods or rancho cubs when rings
belonging to different fragments of bone are joined together by threaded
rods (in Ilizarov type external fixatour with or without hinges) or
struts (TSF external fixatour).
Applicational rationals
In ideal construct we would like to have:
Rule of twos:
2cm between skin and frame
2 rings/bone segment
2 points fixation/ring
Fixation both (2) ends of the bone
segment (near-near and far-far)
Pin and wire fixation in two planes
Other
1.8 mm smooth or olive wires (adult)
6.0 mm tapered hydroxyapatite coated half
pins (adult)
Wires in methaphysis
Pins in diaphysis
Type of fracture or deformity can prevent surgeon
to achieve ideal construct. In that case very likely additional wires or
half pines will be added to the construct.
There are some anatomical restrictions surgeon has
to respect when applying the frame. Mainly nerves and vessels corridors.
It is advisable not to enter them. If one of the major vessels is
entered by wire, wire has to be removed, entry side compressed for 10
min or until bleeding stops and then repositioned wire inside safe
corridors. If major damage of nerve or vessel is suspected, surgical
exploration and repair is necessary.
More of history and basic principles is available
using this link (Wikipedia).
