1 Preliminary remarks topenlarge
Children's hip fractures have historically had a bad prognosis. Accurate stable fixation has been one of the factors identified to improve the outcome.
Stable fractures have a better prognosis than displaced fractures.
The main problems have been avascular necrosis (AVN) due to disruption of the blood supply, nonunion and malunion due to unstable fixation.
The objective is timely fixation without disruption of the blood supply.
2.0, 2.5, or 3.0 mm K-wires can be selected depending upon the size of the child.
Larger K-wire sizes are preferred for stability.
Threaded K-wires also increase stability.
Typically, two K-wires separated vertically are inserted. This configuration may be more suitable in smaller bones.
An alternative is three K-wires used in an apex-distal, triangular configuration, with the lower central K-wire abutting the calcar.
Inserting a single central K-wire does not provide rotational stability.
K-wires alone may not provide adequate stability for a vertically-oriented fracture line. A pediatric hip locking plate is a better construct if the fracture line is more vertical.
If the child is too small for a plate, the K-wires must be protected with a hip spica cast.
2 Reduction topenlarge
A K-wire is inserted through the lateral cortex of the femur just above the level of the lesser trochanter and advanced to the fracture line.
If necessary, manipulation of the femoral head is achieved using a small K-wire, inserted into the proximal fragment, as a joystick.
Pitfall: Secondary subtrochanteric fractures may occur if K-wires are inserted below the level of the lesser trochanter.
The femoral neck is manipulated gently into position, usually by lifting with a bone hook and manipulating the K-wires.
Gentle reduction maneuvers are essential in order to prevent secondary damage to the femoral head blood supply.
3 Fixation topenlarge
When acceptable reduction has been obtained, the first K-wire is advanced across the fracture and into the femoral head. Overpenetration into the hip joint must be avoided.
Additional wires are inserted under x-ray control, using image intensification.
The K-wire positions are confirmed on AP and lateral x-ray images, using image intensification.
If using a standard radiolucent table, the K-wire fixation is generally stable enough to allow "frog" lateral view.
The K-wires are repositioned if necessary.
Images at multiple angles are used to confirm that the K-wires do not penetrate into the hip joint.
Pitfall: Wire penetration can occur, especially with eccentrically placed wires, even if not apparent on standard AP or lateral x-rays.
Typically, 5 mm of epiphyseal bone/cartilage should remain between the wire tip and joint surface.
Dynamic, real-time image intensification, with a full range of internal and external rotation at different degrees of flexion, is useful to see how close the K-wire-tip is to the joint surface of the head.
Observing an approach/withdrawal of the K-wire tip helps in judging its position. Some surgeons supplement this examination with 3-D image intensification for confirmation.
Arthrography is useful to confirm correct wire placement in the younger patient.
Cutting the K-wires
The K-wires can be bent and cut short and left beneath the fascia lata.
The K-wires are usually removed with a short secondary procedure once the fracture is healed.