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 - Cancellous screws

1. Preliminary remarks

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.

Principles of reconstruction

Use two or three 7.0 mm or 7.3 mm cancellous screws. Make sure they are parallel and that the thread is in the head fragment and does not cross the fracture line.
The inferior screw should rest on the calcar. A washer may be used to stop the screw head from penetrating the bone of the greater trochanter.
These screws can be inserted open or percutaneously through stab incisions.

femoral neck fracture subcapital displaced

Teaching video



AO teaching video: The 7.3mm Cannulated Screw: Femoral Neck Fracture

2. Reduction

Reduction of varus and retroversion

Always start with an attempt at closed reduction. If a satisfactory reduction is achieved, proceed with fixation as described below.
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.
If closed reduction fails, carry out a limited open reduction.

mio cancellous screws

3. Lateral approach for closed reduction and fixation

4. Fixation

Guide-wire insertion

The screws must be parallel. The guide wires may be inserted freehand under x-ray control to ensure they are parallel, or an aiming device may be used if available.

If using an aiming device, expose the greater trochanter through an incision just large enough for the device.

If using an aiming device with a central hole, it may be best to start by placing a wire in the center of the neck and head. The three wires for screws may then be placed through the aiming device in a triangle around the central wire, with one wire below and two above the central wire.

mio cancellous screws

Alternatively, the first wire may be placed along the inferior border of the neck, with the two superior wires then being placed parallel to the first wire.

mio cancellous screws

Determine screw length

Determine the length of the screws with the aid of the measuring device.
Choose the length of the drill and screws 5 mm shorter than the length of the guide wires.

mio cancellous screws

Insertion of the cannulated screws

Drill over the wires with a 3.6 mm cannulated drill bit. Then insert three 7.0 mm or 7.3 mm cannulated cancellous screws over the wires.
In younger patients with dense cancellous bone, the cannulated tap may be necessary to precut the thread.
A washer may be used to avoid penetration of the screw head through the thin cortex.

mio cancellous screws

5. Postoperative treatment

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.

Prognosis of proximal femur 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.

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.

6. Case

Preoperative image of a displaced right femoral neck fracture in a middle-aged man

Preoperative image of a displaced right femoral neck fracture in a middle-aged man

AP and lateral preoperative images showing significant displacement.

AP and lateral preoperative images showing significant displacement.

Patient in supine position with a C-arm placed to obtain AP and lateral images. The unaffected leg is in a well-padded, supported "up and away" position.

The maneuvers to obtain AP and lateral views should be rehearsed before sterile drapes are applied.

Patient in supine position with a C-arm placed to obtain AP and lateral images

AP image showing the fracture is reduced with traction and internal rotation.

AP image showing the fracture is reduced with traction and internal rotation

Lateral image with internal rotation showing slight distraction.

Lateral image with internal rotation showing slight distraction

Targeting for percutaneous incision.

Targeting for percutaneous incision

Lateral skin incision.

Lateral skin incision

The tensor fascia is incised and the vastus lateralis is lifted anteriorly and held with a Hohmann retractor.

The tensor fascia is incised and the vastus lateralis is lifted anteriorly and held with a Hohmann retractor

First guide wire inserted in anterosuperior position.

First guide wire inserted in anterosuperior position.

The second guide wire is inserted inferiorly, immediately along the calcar.

The second guide wire is inserted inferiorly, immediately along the calcar

The third guide wire is inserted in a posterosuperior position.

The third guide wire is inserted in a posterosuperior position

The screw lengths are measured from the guide wires.

The screw lengths are measured from the guide wires

The cannulated lag screws are inserted. In this case titanium screws were used. This patient is at risk of osteonecrosis, the use of titanium screws allows future MRI imaging to assess the state of the femoral head.

The cannulated lag screws are inserted

Final images showing eccentrically placed cannulated screws. Ideally, the insertion points should all be above the level of the lesser trochanter to reduce the risk of subsequent subtrochanteric fracture.

Final images showing eccentrically placed cannulated screws

9 weeks postoperative images demonstrating fracture healing and slight compression of the fracture site. The heads of the screws have backed out a few mm.

9 weeks postoperative images demonstrating fracture healing and slight compression of the fracture site

22 weeks postoperatively shows final healing.

22 weeks postoperatively shows final healing