Authors of section

Authors

Ernst Raaymakers, Inger Schipper, Rogier Simmermacher, Chris van der Werken

Executive Editors

Joseph Schatzker, Peter Trafton

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MIO - Sliding hip screw

1. Preliminary remarks

Beware! Some of these fractures may be unstable, eg, fractures with a large lesser trochanteric fragment.
The definitive decision for the treatment of this fracture will be made after positioning of the patient and reduction of the fracture. Since emergency department x-rays are often of suboptimal quality, verification of the preoperative diagnosis using image intensification is necessary.

The lesser trochanter is the key in the decision making as to the choice of the appropriate fixation device.

Some surgeons consider this fracture to be a stable trochanteric fracture and feel that it can be treated with closed reduction and an extramedullary sliding screw system for internal fixation. If in doubt about the number of parts and stability, resort to a different fixation (eg, DHS with a trochanteric stabilization plate (TSP), or intramedullary fixation).

Note
There are many different designs of extramedullary sliding devices for the fixation of these fractures available. The general concept of their application is shown on the next pages with the AO dynamic hip screw (DHS) which is currently the gold standard.

mio sliding hip screw

Teaching video

AO teaching video: The sliding hip screw

2. Closed reduction

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. If an unsatisfactory reduction is achieved (eg, large and displaced lesser trochanter) use an intramedullary fixation device.

Reduction will be achieved by first pulling in the length axis of the leg and by internal rotation of the leg.

3. Guide wire insertion

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 (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.

To facilitate the insertion of the guide wire for the screw in the axial view an additional guide wire might be placed by hand.

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.

The aiming device is chosen according to the chosen CCD angle of the implant.

Insertion of 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.

The guide wire is inserted through the aiming device and advanced into the subchondral bone.

4. Screw insertion

Determination of the length of the DHS screw

Determine the length of the DHS screw with help of the measuring device. Select a screw which is 10 mm shorter than the measured length.

Determine the length of the DHS screw with the help of the measuring device.

Drilling

Adjust the cannulated triple reamer to the chosen length of the screw.
Drill a hole for the screw and the plate sleeve.

Adjust the cannulated triple reamer to the chosen length of the screw. Drill the 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.

When the screw has reached its final position, the T-handle has to be in line with the longitudinal axis of the femur.

5. Plate fixation

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 and 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.

Determine the length of the DHS screw with the help of the measuring device.

Fixation of the plate

Fix the plate to the femoral shaft with an appropriate number and size of plate holding cortical screws.

Note
There is no need to use the compression screw. As the patient bears weight, the fracture will impact and compress due to the sliding design of the implant.

Adjust the cannulated triple reamer to the chosen length of the screw.

6. Postoperative treatment

Some simple pertrochanteric fractures with fracture of the lesser trochanter are stable and allow for full weight bearing. It seems, however, advisable to relate the way of weight bearing postoperatively to the displacement of the lesser trochanter. The closer to its anatomical position the more the weight bearing.

Follow-up

The first postoperative visit is at 6 weeks. Check the position of the fracture with appropriate x-rays. See the patient at six-week intervals until union of the fracture and then as desired.

Implant removal

Only if necessary, and not before union of the fracture. Allow usually a minimum of 6 months before removal.

Prognosis of proximal femoral fractures

After surgery the outcomes of greatest concern are
  • mortality
  • loss of independence
  • loss of mobility
  • residual pain.

Mortality
Mortality generally occurs within the first six months after fracture; studies have shown that these rates range from 12-37%.
Predictors of higher mortality rates are patients who are:

  • older
  • male
  • have other comorbid conditions (such as cardiac failure, diabetes, and chronic air flow limitation)
  • have cognitive disorders.

For more information see the additional material on perioperative care in elderly hip fracture patients.