1 Principles 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.
Positioning of the patient
The patient is positioned supine on the fracture table. The ipsilateral arm
is elevated in a sling and the contralateral uninjured leg is placed on a leg
C-arm image intensifier control during surgery is a must.
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 with DHS topenlarge
Technique of insertion
The first step is to position a guide wire on the neck and hammer it into
the head. With the C-arm positioned to show the neck axis, slide the guide wire
along the neck, parallel to its axis, and gently tap it into the head.
With the C-arm in the AP, make sure that the wire subtends the CCD (collum-center-diaphysis) angle of the neck. This will help you with the insertion of the guide wire for the DHS screw.
Insertion of the guide wire
Choose the correct aiming device according to the CCD angle of the neck.
Check its position in the AP view with the image intensifier.
Insert the guide wire through the aiming device and advance it into the subchondral bone of the head, stopping 10 mm short of the joint.
In both the AP and lateral planes, the guide wire should be positioned along the axis of the neck and through the middle of the head, and advanced to within 5 mm of the subchondral bone.
Determination of the length of the DHS screw
Determine the length of the DHS screw with the help of the measuring device. Select a screw which is 10 mm shorter than the measured length.
Adjust the cannulated triple reamer to the chosen length of the screw.
Drill a hole for the screw and the plate sleeve.
The correct screw is mounted on the handle and inserted over the guide wire.
By turning the handle it is advanced into the bone. Do not push forcefully or
you may distract the fracture.
In young patients with hard bone it is best to use the tap to precut the thread for the screw. Otherwise the screw may not advance, and you may actually displace the fracture by twisting the proximal fragment as you attempt to insert the screw.
When the screw has reached its final position (checked with the image intensifier: 10 mm short of the subchondral bone in the AP and lateral), the T-handle of the insertion piece should be parallel to the long axis of the bone to ensure the correct position of the plate.
Fixation of the DHS plate
Generally, a two-hole DHS plate with the preoperatively determined CCD angle
will be chosen.
Take the plate with the correct CCD angle, slide it over the guide wire, and mate it correctly with the screw.
Then push it in over the screw and seat it home with the impactor.
4 Insert an antirotation screw topenlarge
As the plate is mated with the screw and seated with the impactor, some
impaction of the fracture may occur.
Fix the plate to the femur with one or two screws.
If additional rotational stability is required, insert a cannulated screw above the DHS. This screw must be parallel to the DHS in both the AP and lateral planes.