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

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.
In simple pertrochanteric fractures, the lesser trochanter remains attached to one of the two fragments. In case it is not, we are dealing with another fracture type, and another treatment modality might be a better choice.
Fractures where the lesser trochanter is still attached to the femoral shaft are generally called stable trochanteric fractures, because after anatomic reduction and internal fixation there is little tendency to loss of reduction under physiological loading.
If the lesser trochanter is attached to the proximal fragment, closed reduction might be impossible because the pull of the psoas muscle will flex and externally rotate the proximal fragment, and traction will not correct this displacement. In these cases, open reduction is often necessary.

Note
Because of the intrinsic stability of fractures with lesser trochanter attached to the distal fragment after reduction, most implants will be adequate to maintain reduction and result in uneventful healing. Simple extramedullary sliding devices like the DHS are the cheapest and most logical choices for fixation. The general concept of the application of these devices is shown on the next pages with the AO dynamic hip screw (DHS) used as an example.

The lesser trochanter must be attached to one of the two fragments.

Teaching video

AO teaching video: The sliding hip screw

2. Reduction

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 view with an image intensifier.

Reduction will be achieved by first pulling in the length axis of the leg in order to distract the fragments and regain length.

Open reduction

If closed reduction fails, carry out a limited open reduction. The lateral incision is enlarged as necessary by increasing its length and retracting the vastus lateralis anteriorly and medially. Direct visualization of the fracture site is usually unnecessary. Clear the fracture site of interposed soft tissue as needed. Then restore length and correct rotation. Fracture table adjustments are usually required.

Align the corresponding fracture surfaces so they are opposite one another. Then place a pointed reduction clamp so that one point catches the proximal fragment above the lesser trochanter. Reduction is achieved by closing the clamp.

Confirm the reduction with the image intensifier.

mio sliding hip screw

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 center-collum diaphysis (CCD) angle of the neck. This clarifies the anteversion of the femoral neck, which may be affected by internal rotation of the limb for reduction of the fracture.

In order to facilitate the insertion of the guide wire for the screw 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 a 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 the 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 measuring device and select a screw which is 10 mm shorter.

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 a hole for the screw and the plate sleeve.

Insertion of the femoral neck screw

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. Fixation of the DHS plate

Application of the DHS plate

Generally, for pertrochanteric fractures with lesser trochanter attached to the distal fragment, a two-hole DHS plate is enough. 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.

Generally, a two-hole DHS plate with the preoperatively determined CCD angle will be chosen.

Plate fixation

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.

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

6. Case

Preoperative AP image of the pelvis showing right intertrochanteric fracture.

Preoperative AP image of the pelvis showing right intertrochanteric fracture.

Initial images in the operating room with the patient in traction, showing the fracture reduced.

Initial images in the operating room with the patient in traction, showing the fracture reduced.
Initial images in the operating room with the patient in traction, showing the fracture reduced.

Lateral image showing centrally positioned guide wire for DHS.

Lateral image showing centrally positioned guide wire for DHS.

This image demonstrates insertion of the triple reamer.

This image demonstrates insertion of the triple reamer.

The hip screw is inserted under X-ray control.

The hip screw is inserted under X-ray control.

Post-operative image showing hip screw placed on both views with good tip apex position. (Tip apex distance in this instance is about 10 mm).

Post-operative image showing hip screw placed on both views with good tip apex position. (Tip apex distance in this instance is about 10 mm).

2 years postoperative image showing complete healing. It is recommended that two bicortical screws are placed in the DHS side plate.

2 years postoperative image showing complete healing. It is recommended that two bicortical screws are placed in the DHS side plate

7. Postoperative treatment

Simple pertrochanteric fractures are stable after internal fixation and full weight bearing is allowed.

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.