Authors of section

Executive editor

Michael Baumgaertner

Authors

Michael Huo, Michael Leslie, Iain McFadyen

Open all credits

Lag screw with or without neutralization plate

1. Introduction

The stabilization of periprosthetic fractures that disrupt the extensor mechanism at the tibial tubercle is critically important to knee function.

Fixation is challenged by the size of the fracture fragment, and the need for expeditious mobilization of the knee.

Stabilization of periprosthetic fractures that disrupt the extensor mechanism at the tibial tubercle

Neutralization for large fragments

If fracture fragment size allows for neutralization, a small fragment plate is typically utilized. This may be inclusive of locking fixation if desired.

A hook plate is helpful with a smaller non-comminuted fragment. An interfragmentary compression screw is inserted through the plate.

Neutralization for large fragments

2. Patient preparation and approach

In most cases, the midline approach to the knee that was used for the knee arthroplasty will be extended in order to adequately expose the fracture.

The obliquity of the fracture will dictate a medial, anterolateral (open or minimally invasive approach), or posteromedial extension to the prior incision.

Small incisions may be made over the distal aspect of the plate utilizing fluoroscopy as a guide, in order to minimize larger surgical approaches.

With rare exceptions, supine positioning with a bump under the ipsilateral greater trochanter will achieve neutral rotation of the limb.

Positioning the limb in full extension will facilitate the reduction of the tibial tubercle and decrease deforming forces across the fixation construct.

Supine positioning

3. Reduction

The fracture site should be exposed, cleared of hematoma and debris, and reduced utilizing direct reduction methods.

Reduction

Large non-absorbable sutures can be inserted in the patellar tendon to aid in reduction.

Large non-absorbable sutures can be inserted in the patellar tendon to aid in reduction

Provisional fixation is attained with K-wires.

Provisional fixation is attained with K-wires

4. Fixation

Lag screw fixation

Bicortical lag screws are inserted according to the standard technique. If the fracture fragment will allow for multiple lag screws, they should be inserted in a divergent pattern.

The screws can be countersunk to avoid soft tissue prominence. Washers can be utilized to disperse forces more evenly in the near cortex.

Lag screws should not be inserted through the cement mantle as reliable compression cannot be achieved.

Lag screw fixation

Plate contouring

In order to achieve earlier mobilization, the addition of a neutralization plate may reinforce the construct. The surgeon should ensure that the plate selected is perfectly contoured to the bone as not to disrupt the compression that is achieved by the lag screw. The plate should be positioned to avoid plate prominence.

Plate contouring

Plate fixation

The plate is fixed to the bone using a mixture of cortical, locking, and non-locking screw fixation.

Plate fixation

Options for additional stability

Additional stabilization can be achieved with locking and nonlocking screw fixation above and below the fracture site.

If there is no room for bicortical screw fixation, different options may be used around the component stem to secure the plate:

  1. Unicortical locking screw fixation
  2. Cerclage cables integrated into the plate
  3. Locking attachment plate

For additional details on these implants please refer to adjunct plate options.

Alternative fixation technique

In the setting of a very small or comminuted fragment a tension band construct or suture anchors can be utilized to reinforce a lag screw or to achieve primary stability. A detailed description of these techniques can be found in the trauma section.

Additional stability

Tubercle fracture repair augmentation

To protect this tubercle fracture repair during the healing process, a protective cerclage wire or suture can be passed around the upper pole of the patella and through a transverse drill hole distal to the tibial tubercle.

This wire frequently breaks later, and it is best to remove it once healing is assured at 3-4 months.

Tubercle fracture repair augmentation

5. Radiographic verification

Anteroposterior, mediolateral, and oblique radiographs of both the fracture site and the arthroplasty are obtained at the end of the procedure, to ensure that:

  • There is no displacement
  • The joint articulation is preserved

6. Aftercare

The knee is braced in full extension during ambulation for 6 weeks.

Supervised gentle knee flexion can start after wound healing. Resisted knee extension should be limited until 10 weeks or fracture consolidation is visible.