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.
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 a “frog” lateral view.
The 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.
5. Hip spica
Because K-wire fixation is less stable, and only indicated for younger children, a hip spica cast is generally used to supplement the fixation.