1 Preliminary remarks top
Choice of fixation method
Displaced transcervical and subcapital fractures are unstable. Their prognosis is by and large the same and they will be discussed as one group for the purpose of manner of reduction and choice of fixation, should internal fixation be chosen as the method of treatment.
They can be stabilized with either cannulated screws or DHS. At this point we do not have sufficient evidence based information to point to one or the other method as superior. If the surgeon feels that optimal stability is required, he should choose a sliding hip screw (DHS) type of implant for fixation.
If added rotational stability is desired in addition to the DHS, a cannulated screw is inserted above and parallel in both planes to the DHS. It must be parallel in order not to block the sliding property of the DHS implant.
Principles of reconstruction
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 Flynn reduction maneuver topenlarge
The most logical and anatomically based, atraumatic reduction maneuvre for displaced intracapsular fractures of the femoral neck, was published by Flynn (1974). This is not appropriate for the totally displaced intracapsular fractures.
It is based on the fact that in the anatomical position, the major capsular fibres of the hip joint are in a spiral configuration.
This arrangement pulls the femoral head tightly into the acetabulum: Flynn described this as the “tight-packed” status of the hip.
If the hip is flexed and slightly abducted, the spiral of the capsular fibres is unwound...
... producing the “loose-packed” condition of the hip joint.
In the “loose-packed” state, manual traction along line of the femoral neck disimpacts the fracture fragments.
The traction produces an hour-glass shape to the capsule, which realigns the disimpacted fracture fragments.
The most comfortable set-up is for the assistant to support the heel of the injured leg, whilst the surgeon’s ipsilateral hand pulls along the line of the femoral neck, the other hand controlling the knee.
Whilst manual traction is maintained along line of the femoral neck, the leg is first internally rotated, to correct any retroversion, and is then brought down to the extended position.
This produces a “tight-packed” hip and impacts the realigned fracture fragments.
The injured leg is then placed on moderate traction in the position of reduction, on a fracture table.
The uninjured leg and ipsilateral arm are raised and supported...
...to allow unimpeded positioning of the image intensifier.
The reduction must be checked in both the AP and lateral views with an image intensifier. If closed reduction fails, carry out a limited open reduction.
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.