1 Principles topenlarge
Please note that impacted subcapital femoral neck fracture are relatively stable. However, undisplaced fractures are potentially unstable.
These fractures are best fixed with screws rather than the bulky sliding hip screw (DHS), which is an alternative.
No reduction is necessary.
Cancellous screw fixation
Use two or three 7.0 mm or 7.3 mm cancellous screws. Make sure they are parallel and that the thread is in the head fragment and does not cross the fracture line.
The inferior screw should rest on the calcar. A washer may be used to stop the screw head from penetrating the bone of the greater trochanter.
These screws can be inserted open or percutaneously through stab incisions.
AO teaching video: The 7.3mm Cannulated Screw: Femoral Neck Fracture
2 Positioning topenlarge
The patient is positioned supine on a conventional operating table, or on a
fracture table. C-arm image intensifier control during surgery is a must.
Be gentle in transferring the patient and do not apply traction in order not to disimpact and displace the fragments.
3 Fixation top
The screws must be parallel. The guide wires may be inserted freehand under x-ray control to ensure they are parallel, or an aiming device may be used if available.
If using an aiming device, expose the greater trochanter through an incision just large enough for the device.
If using an aiming device with a central hole, it may be best to start by placing a wire in the center of the neck and head. The three wires for screws may then be placed through the aiming device in a triangle around the central wire, with one wire below and two above the central wire.
Alternatively, the first wire may be placed along the inferior border of the neck, with the two superior wires then being placed parallel to the first wire.
Determine screw length
Determine the length of the screws with the aid of the measuring device.
Choose the length of the drill and screws 5 mm shorter than the length of the guide wires.
Insertion of the cannulated screws
Drill over the wires with a 3.6 mm cannulated drill bit. Then insert three 7.0 mm or 7.3 mm cannulated cancellous screws over the wires.
In younger patients with dense cancellous bone, the cannulated tap may be necessary to precut the thread.
A washer may be used to avoid penetration of the screw head through the thin cortex.