Authors of section

Author

Bruno Peirone

Executive Editor

Amy Kapatkin

General Editor

Noel Moens

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Lag screw and neutralization plate

1. Indications

The preferred treatment for 32-A2 fractures is internal fixation with lag screws and/or cerclage wires across the fracture line, combined with a neutralization plate. The screws/wires applied across the fracture generate friction between the fragments and counteract shearing forces, while the plate protects the fixation from collapsing.

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2. Principles

Anatomical reconstruction

Anatomical reconstruction of the fragments is mandatory for the correct placement of lag screws and/or cerclage wires.

Note: If anatomical reconstruction cannot be accomplished, then a bridging technique should be used.

lag screw and neutralization plate

Lag screws vs. cerclage wires

In order to achieve compression and counteract the shearing forces, either lag screws, cerclage wires or a combination of both can be used depending on fracture configuration.

Lag screws are the preferred technique because they provide greater interfragmentary compression than cerclage wires.

Cerclage wires should only be used if the fracture configuration allows for placement of at least two wires and should not be used on short oblique fractures.

A singular lag screw can be used on short oblique fractures as long as it is directed at a right angle to the fracture plane.

Read more about cerclage wire technique and lag screw fixation.

lag screw and neutralization plate

3. Patient positioning and approach

This procedure is performed with the patient in lateral recumbency, and through the open approach to the shaft.

lag screw and neutralization plate

4. Surgical technique

Reduction

Bone holding forceps are applied to the proximal and distal fragment for distraction. This is necessary to counteract the strong muscles surrounding the bone, particularly in large breed dogs.

lag screw and neutralization plate

Once distraction is achieved, the bone fragments are pulled, toggled or levered along the fracture line into perfect anatomical reduction with the help of one or two pointed reduction forceps placed across the fracture line.

intramedullary pin fixation with cerclage wires

Preliminary fixation

The fracture is preliminary fixed with one or two pointed reduction forceps while the lag screw(s) or cerclage wires are applied.

Note: take care to avoid placing the forceps at the planned lag screw or cerclage wire sites.

Anatomical reduction and the stability of preliminary fixation are carefully checked before applying the implants.

lag screw and neutralization plate

Lag screw fixation

The screws are inserted in lag fashion. To achieve maximal interfragmentary compression, the screws must be directed perpendicular to the fracture plane.

Read more about lag screw fixation.

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Depending on the fracture configuration, 1-2 additional screws are inserted in the same fashion.

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Note: The screws should be evenly spaced and care should be taken to avoid placing them too close to each other. Safe distance is at least 1 screw diameter away from any fracture line and 2 screws should be separated by 2 x their diameter.

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Cerclage wires application

Indications for the use of cerclage wires are long oblique fractures, in which at least two wires can be applied.

Read more about cerclage wire technique.

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Pitfall: Placing cerclage wires on a short oblique fracture will generate larger shear forces and will cause the fracture to shear and collapse.

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Plate selection

The length of the plate should allow the placement of at least 3-4 screws in each major fragment.

Note: a traditional non-locking or locking plate (DCP, LCDCP or the LCP) can be used. If using a LCP, the dynamic compression unit (DCU) part of the combi hole can be used with locking screws.

lag screw and neutralization plate

Plate application

The contoured plate is applied to the lateral surface (tension surface) of the bone and secured with at least three bicortical screws in each of the major fragments. Avoid screw insertion close or at the level of the fracture line. All screws are placed in a neutral mode.

Read more about plate preparation.

32 A2

Pitfall: in spiral fractures it may be difficult to determine the exact location of the fracture line once the bone is reduced. Careful examination of the fracture configuration and pre-planning is necessary to avoid placing a screw too close to or at the level of a fracture line.

lag screw and neutralization plate

5. Alternative surgical technique

Lag screws through the plate

In cases, where independent lag screws would interfere with the placement of the plate, the lag screws can be placed through the plate holes to achieve compression.

lag screw and neutralization plate

6. Aftercare

Phase 1: 1-3 day after surgery

Aim is to reduce the edema, inflammation and pain.
Integrative medical therapies, anti-inflammatory and analgesics.

Phase 2: 4-10 days after surgery

Aim is to resolve the hematoma, edema and control pain, and prevent muscle contracture.
Anti-inflammatory and analgesic medications may still be needed. Rehabilitation and integrative medical therapies can be used.

Special attention should be given to patients less than 1 year of age with a femoral fracture. Rehabilitation is strongly recommended to help prevent quadriceps muscle contracture.

If the dog is not starting to use the limb within few days after surgery, a careful evaluation is recommended.

10-14 days after surgery the sutures are removed.

Radiographic assessment is performed every 4-8 weeks until bone healing is confirmed.

~3-4 months after follow up radiographs surgery check bone healing.