1 Preliminary remarks topenlarge
Beware! A2 fractures are multifragmentary and are unstable.
In A2.2 and A2.3 fractures, the number of intermediate fragments is larger. In A2.2 fractures, the greater trochanteric mass is involved in the (four-part) fracture, and in A2.3, the fracture line extends well (>1 cm) below the lesser trochanter.
Because these fractures are considered unstable (loss of the lesser trochanter which is important for weight transfer, and loss of greater trochanter which allows collapse of the fracture and foreshortening of the neck), extramedullary devices are considered as a second choice for fixation. They lack the necessary stability to ensure union in a satisfactory position of all the fragments.
The extramedullary devices are unsuitable for the fixation of these fractures because they allow axial collapse under repeated loading. The next pages will show the use of an extramedullary device (DHS) coupled with the trochanter stabilization plate (TSP) which adds to the stability of the fixation and prevents axial collapse.
2 Closed reduction topenlarge
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 holder.
Reduction is usually achieved by first pulling in the direction of the long axis of the leg in order to distract the fragments and regain length.
Next comes internal rotation.
The reduction must be checked in both the AP and lateral with an image intensifier.
In case the closed reduction should fail, open reduction will be necessary.
3 Insertion of the guide wire topenlarge
Technique of insertion
The approach is between the vastus lateralis and the septum. 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 it subtends the CCD angle of the neck (collum-center-diaphysis angle, ie, angle subtended between the femoral neck and shaft axes). This will help you with the insertion of the guide wire for the DHS screw.
Application of the aiming device
Choose the correct aiming device according to the CCD angle of the neck. Check its position in the AP with the image intensifier.
Insertion of the guide wire for the screw
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.
Position it so that in the AP it is in the caudal half of the neck, and in the axial view in the center of the neck.
4 Screw insertion topenlarge
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 four-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.
The plate is fixed with one cortical screw to the femur shaft.
5 Internal fixation topenlarge
Preparation of the Trochanter Stabilizing Plate (TSP)
If necessary, contour the spoon-shaped end of the Trochanter Stabilizing Plate to fit the mass of the greater trochanter. Position the TSP over the DHS plate in such a way that it is securely seated and that the screw holes line up.
Application of the TSP
Now the TSP is mounted over the DHS plate and is fixed using the holding
cortical screws which connect the plate to the shaft.
Depending on the fracture pattern, if the greater trochanter is not captured by the TSP, a tension band wiring may be added to hold the abductor muscle insertion reduced and securely fixed. A screw may also be added through the plate into the neck to prevent rotation of the head and neck fragment.
The compression screw for the DHS should not be used.