Cerclage wiring is the use of an encircling wire loop or ring to bring fracture ends together and provide some compression, particularly when used with K wiring. In this Section we will consider a number of techniques in which cerclage wiring is used such as 90/90 wiring, the Lister Loop and Tension Band Wiring.
Principle
90/90 Wiring: Loops of wire which are placed at 90 degrees to each other to provide a stable fixation which resists distraction and torsion. This is able to be applied rapidly and works well when there is good bone exposure, for example in the case of re-plantation or even arthrodesis.
Lister Loop: A loop of wire provides compression while a K wire provides longitudinal alignment. This is the classic small joint arthrodesis technique.
Tension Band Wire: This involves the principle of fixation along the extensile surface of a curved bone. When a curved bone is axially loaded, one side of the bone will take a compression force and the other side will be distracted. This can be seen if a transverse fracture is placed along a curved bone and an axial load is applied, the bone will fold over towards the inside of the curve. If a plate or a loop of wire is placed along the outside of the curve, then this resists the distraction forces and prevents the bone from buckling over, thus providing stability to the fracture. Clearly, a loop of wire cannot take a compressive load, but it resists distraction very well and this is the principle of a tension band wire.
Technique
90/90 Wiring
Step 1 – Place 2 transverse drill holes on each side of the fracture and pass a loop of wire through them giving consideration to where the twist is going to be.
Tip: Place the wires strategically as the twist of wire may be palpable beneath the skin or may interfere with overlying gliding structures such as flexor and extensor tendons.
Step 2 – Once the loop has been placed do not twist tightly at this stage, but make 2 further drill holes each side of the fracture at 90 degrees to the wire.
Tip: Consider whether you can come inside or outside the loop of wire, as you do not want to break the wire by drilling through it!
Again, consider where the twist is going to be placed. Once the two loops have been placed, then slowly tighten up the wire – ensure 5 or 6 tight twists – and cut the excess wire beyond these. The wire twists can then be folded down flat or twisted inwards to bury into the bone if possible.
Tip: When tightening the wires maintain a traction on the wire perpendicular to the loop and twist slowly at the same time. If this is not done the loop will not be tight and the fracture will lose the compression as soon as the wire is released.
Lister Loop
Described in the context of arthrodesis. Once the joint surfaces have been cut to the appropriate angles, oppose ends snugly and then perform the fixation:
Step 1 – Use a double-ended K wire of appropriate diameter – usually 1.1mm – and starting at the centre of one of the arthrodesis surfaces, drill obliquely through the bone and (in a patient) out through the skin. Re-position the drill onto this external K wire end and withdraw the K wire so that the tip of the other end is just under the arthrodesis surface. This sets the K wire ready to pass retrograde back across the arthrodesis site.
Step 2 – Drill 2 transverse drill holes through the bone, being careful to avoid the K wire. Pass a cerclage wire through these two holes, again considering where the twist is going to be left. Start to gently tighten the twist until the bone edges are comfortably adjacent to each other. STOP at this point and advance the K wire across the joint and out through the other cortex. Once this is through, the cerclage wire can be fully tightened and trimmed, as described before. The wire can be cut flush to the bone or left through the skin.
Tension Band Wiring
The configuration here is that two longitudinally placed K wires are used to provide axial stability and the wire figure of eight provides compression, and resistance to flexion forces.
Step 1 – Reduce the fracture and cross the joint with 2 longitudinally aligned K wires (either directly/ ante grade or in a retrograde technique as described before). Place a transverse drill hole in the distal fragment and pass a cerclage wire through this.
Step 2 – Bend the 2 K wires AWAY from the bone and cut about 5mm beyond the bend.
Step 3 – Arrange the cerclage wire in a figure of 8 orientation and hook this underneath the protruding ends of the K wires and gently tighten.
Step 4 – Twist the K wires so that the ends are now pointing down into the bone trapping the tension band wire beneath and the wire ends are flush with the bone.
