Authors of section

Authors

Andrew Howard, Theddy Slongo

Executive Editor

Fergal Monsell

General Editor

Chris Colton

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General K-wire principles

1. Indications

K-wire fixation is indicated for:

  • Fractures in epi-/metaphyseal areas as defined by the AO classification
  • Fractures of small bones (eg, hand and foot)
  • Small bony fragments
  • For fragment reposition in multifragmentary fractures in addition to stable fixation
Note: K-wire fixation is an adaptation and does not, alone, give sufficient stability for early functional rehabilitation.

K-wire fixation alone is not indicated in:

  • Diaphyseal fractures
  • Multifragmentary fractures
Areas of pediatric bones

2. K-wire principles

K-wire size is chosen according to the age of the child and the size of the fragment.

The chosen entry point, together with the correct direction of the K-wire, is the key to optimal fixation.

For most simple fractures, two, occasionally three, K-wires give sufficient stabilization if the K-wires:

  • Are of the correct size (1.6/2.0 mm)
  • Do not cross each other at the fracture level
  • Are intraosseous

K-wire osteosynthesis usually requires additional plaster cast protection.

Additional plaster cast protection

Advantages:

  • Cheap
  • Universally available
  • Can be inserted by hand (with a T-handle), but also by drill provided thermal injury is avoided
  • Easy to remove

Disadvantages

  • Not functionally stable

3. Size of K-wire

The following points influence the size of the K-wire:

  • Patient age/weight
  • Fracture location
  • Fragment size
  • K-wire trajectory

Patient age/weight

In children younger than 5–6 years, 1.6 mm K-wires are used for fractures around the shoulder, elbow, knee and ankle joints.

In children above this age, 2.0 mm K-wires are usually used.

Additionally, it is important to take into account the weight of the patient when choosing the diameter of the K-wire.

K-wire size

Fracture location

Metaphyseal fractures of the long bones require at least 1.6 mm K-wires. If only two wires are used, the surgeon may elect to use larger diameter wires.

Fractures of small bones (hand and foot) require 1.0–1.6 mm K-wires.

Fragment size

The size of the K-wire should be chosen according to the size of the fragment. For example, a fracture of the medial epicondyle of the humerus needs a K-wire of smaller diameter than a fracture of the lateral humeral condyle.

K-wire trajectory

For fractures fixed with two (or three) K-wires from only one side, one size bigger K-wires are used than for bilateral crossed K-wiring.

For example, for bilateral crossed K-wiring of a supracondylar humeral fracture 1.6 mm K-wires can be used, whereas for radial divergent wiring of the same fracture 2.0 mm K-wires are preferable.

4. Planning

K-wire entry point

K-wires are, in most cases, inserted from the free fragment into the main fragment. This allows using the K-wire as a joystick for manipulating the free fragment.

K-wire entry point

Note: For proximal subcapital humeral fractures, the K-wire is inserted from the humeral shaft into the head fragment.
K-wire insertion for proximal subcapital humeral fractures

The entry points of the K-wires should be chosen so that they are as far apart as possible where they cross the fracture line.

K-wires crossing the fracture line

This guarantees maximal rotational stability.

Rotational stability

The choice of the entry point must correlate with the planned direction of the K-wire and the end fixation point in the main fragment.

Ideally, if the anatomical site permits, the K-wires should be introduced as perpendicular as possible to the fracture plane. In certain sites, this is not achievable and mechanical stability should not be compromised by obsessive adherence to the above principle.

K-wire direction and fracture plane

K-wire direction in transverse fractures

The direction of the K-wires should be chosen so that the K-wires are well separated at the fracture level.

To achieve this, the length of the fracture line is divided into four equal parts. Ideally, when using two K-wires, the wires should pass approximately through the green area in the illustration.

K-wire direction in transverse fractures

Monolateral divergent K-wires

For oblique (>30°) metaphyseal fractures crossed K-wire fixation may be very difficult, or impossible, as at least one of the K-wires will run nearly parallel to the fracture line.

Crossed K-wire fixation with nearly parallel K-wire to oblique fracture plane

For oblique fractures, therefore, divergent monolateral K-wire fixation is more suitable. For this technique one size bigger K-wires should be used than for cross K-wiring.

If lateral divergent K-wire fixation is not possible, for example, due to soft tissue condition or a structure at risk, another stabilization technique should be used (eg, external fixator, or plate).

Monolateral divergent K-wires in oblique fractures

5. K-wire insertion

The insertion of K-wires is usually monitored by the use of intermittent image intensification.

Stab incision

A small incision or a direct puncture with the K-wire is made over the planned entry point. An incision is recommended to avoid skin damage, which might cause pin-track infection.

Stab incision

K-wire insertion

In order to avoid thermal injury, especially to the physis, K-wires should be inserted by hand, or using an oscillating drill.

Oscillating drilling

If a standard drill is used, it must be run as slowly as possible to avoid a thermal effect.

Additionally, irrigate the K-wire during drilling with a cooled irrigation fluid.

Standard drilling with cooling

If a drill is used, the K-wire is initially inserted manually through the skin incision, onto the chosen bony entry point. While maintaining the correct position of the tip, the drill is attached to the wire.

To prevent bending of the K-wire, it can be helpful to insert the K-wire using an appropriate drill sleeve – this steadies the wire, protects the soft tissues, and ensures optimal direction.

Use of a drill sleeve

It is helpful to reduce the length of the K-wire protruding from the drill to avoid whipping of the wire and loss of trajectory.

Reduced length of the K-wire protruding from the drill

To avoid skidding, the K-wire tip should initially be held as orthogonal as possible to the bone surface until the tip of the wire has a good purchase.

Orthogonal initial K-wire insertion

Once the tip of the K-wire has obtained a good purchase, the angulation of the K-wire should be corrected according to the planned direction of the K-wire.

Adjusting angulation of K-wire direction

Bony resistance should be felt throughout K-wire insertion. Lack of resistance indicates that the pin is not in the bone. If in doubt, check this in two planes (AP and lateral) using an image intensifier.
Bony resistance throughout K-wire insertion

As soon as increased resistance is felt, check that the tip of the K-wire is engaged in the far cortex of the main fragment.

The tip of the K-wire should penetrate the whole depth of the far cortex, but not protrude more than 2–3 mm. This is to avoid neurovascular damage and soft tissue irritation.

Engaging tip of K-wire in far cortex

The free end of the wire is usually left protruding through the skin and is bent through 180°. A sterile dressing protects the entry wound around the wire.

Protruding free end of K-wire

No more than two attempts should be made to insert any one wire across a physis. Repeated puncture of the physis by multiple attempts to insert the wire can result in subsequent growth disturbance.

Avoiding puncture of physis and growth disturbance

6. K-wire removal

The timing of K-wire removal is a matter for judgment by the treating surgeon, based on the age of the child, the pattern of the injury, as well as additional injuries.

Depending on the age of the child, fracture healing has reached the stage where redisplacement is highly unlikely after 3–4 weeks and the K-wires can be removed.