MIO - Sliding hip screw

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.

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.
C-arm image intensifier control during surgery is a must.

AO teaching video: The sliding hip screw

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.

For this procedure a lateral approach for closed reduction and fixation is used.

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.

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.

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.

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.

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.

X-ray of minimally displaced fracture of the left femoral neck.

CT of minimally-displaced fracture but notice comminution.

Closed reduction with the foot internally rotated in boot traction.

AP image with the foot 30° internally rotated.

Lateral intraoperative image of reduced femoral neck.

A guide wire is introduced under X-ray control to determine the proximal end of the incision.

Small incision starting from the guide wire and extending distally.

Insertion of preliminary guide wire to help with targeting for the DHS centrally placed screw and the superior cannulated 7.3 screw.

With the inferior preliminary guide wire in place, the more eccentrically placed superior wire is inserted. The 7.3 mm cannulated screw can then be positioned superior to the final centrally placed dynamic hip screw.

The eccentric 7.3 cannulated screw is now in position with room inferiorly for the dynamic hip screw.

The length of the DHS is measured from the inferior guide wire and the triple reamer set accordingly.

DHS triple reamer inserted for centrally placed dynamic hip screw.

The triple reamer is introduced under X-ray control. If the guide wire jams in the cannulated drill, it may be driven into the joint or even into the pelvis. This should be monitored under X-ray control. This image shows slight penetration of the guide wire into the joint.

AP image showing both screws in position.

Lateral image showing both screws.

The DHS plate is inserted over the hip screw assembly.

Once the plate has been seated, cortical screws are inserted.

Final AP image

Final lateral image

Vastus lateralis falling back down over DHS side plate

Lateral tensor fascia closure.

Final closure

3 weeks postoperative X-rays showing satisfactory position with no sign of displacement.

At 9 weeks there is excellent progression on the AP X-rays ....

… and on the lateral view.

Elderly patients tend not to do well if kept immobilized, so early mobilization should be encouraged. Depending on the fracture configuration, strength of the bone and security of fixation, the surgeon may prefer partial or full weight bearing.

In reality, many elderly patients may not be able to comply with instructions for partial weight bearing.

In practice, it is often best overall to allow weight bearing as tolerated.

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.

Ability to return home
Besides mortality, the ability to return home is also an important outcome for patients with hip fractures. Studies have shown that as few as 50% of patients were able to return home, and that mortality rates are lower in those that do return home compared with rates in those that are transferred to nursing homes or rehabilitation centers.

Predictors of returning home include:

• a younger age (less than 85 years)
• ability to walk independently preoperatively
• ability to perform activities of daily living preoperatively
• living with another person
• ability to walk independently at the time of discharge from the hospital.

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