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  3. Diagnosis
  4. Indications
  5. Treatment

Authors of section


Paulo Barbosa, Felix Bonnaire, Kodi Kojima

Executive Editors

Steve Krikler, Chris Colton

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Lag screw through buttress plate

1. Principles

As the thread advances within the main body of the tibia, the head pushes the medial fragment towards the tibia.

The smooth shaft of the screw prevents any significant hold between itself and the surrounding bone.

The length of the screw shaft must be chosen so that the threaded part of the screw lies fully beyond the fracture line.

The function of a buttress plate is to neutralize any vertical shearing force.

infrasyndesmotic medial fracture with lcl rupture

2. Patient preparation and approach

The patient may be placed in the following positions:

For this procedure a medial approach is normally used.

lag screws oblique or vertical fractures

3. Reduction

Cleaning the fracture site

It is important to visualize and inspect the joint, searching for bone and cartilage fragments detached from the medial malleolus or from the talus, and any impaction of the articular surface at the margin of the fracture. If the articular surface has been impacted, this must carefully disimpacted before the medial fragment is reduced.

Anatomical reduction

Reduce the fracture anatomically with the use of small pointed reduction forceps taking care with the soft tissues.

Depending on fracture configuration and size of the fragment, the use of large pointed reduction forceps through a lateral stab incision may be necessary.

Do not strip the periosteum more than necessary.

lag screw through buttress plate

In the presence of an impacted medial corner fragment, gently open the main vertical fracture plane by retraction of the medial malleolus medially (opening the book). The impacted “corner” fragment, usually identifiable by its articular cartilage, after irrigation if necessary, can then be seen.

Disimpact and carefully tease back the fragment into its anatomical position.

Then close the book by careful reduction of the medial malleolus.

lag screw through buttress plate

Preliminary fixation

Insert two 1.6 mm K-wires as perpendicularly as possible to the fracture plane, about 1 cm proximal to the level of the horizontal tibiotalar joint line.

As decided in preoperative planning, these K-wires should be inserted anterior and posterior in order not to interfere with the planned position of the plate.

Check the reduction under image intensification.

lag screw through buttress plate

4. Fixation

Plate position

Position a four-hole, one-third tubular plate firmly by hand so that two holes lie superior and two holes lie inferior to the fracture line. Plan to position the first proximal screw near the fracture.

This screw must be located in the tibia, 3 mm proximal to the apex of the fracture.

lag screw through buttress plate

Insertion of the proximal screws

Use the 2.5 mm drill bit and protection sleeve. Drill both cortices, but exercise great care not to overpenetrate laterally.

Measure the depth and tap both cortices with the 3.5 mm tap, using the protection sleeve.

Carefully apply the uncontoured plate and insert the first cortex screw. By tightening the screw, the plate will act as a buttress on the distal fragment.

Insert the second proximal 3.5 mm cortex screw as described above.

lag screw through buttress plate

Insertion of the distal lag screws

With the protection of the drill sleeve, drill a 2.5 mm hole as perpendicularly as possible to the fracture plane. Do not drill the far cortex.

Care must be taken to avoid penetration of the ankle joint.

Measure the drill depth and then tap the medial cortex only with the 4.0 mm cancellous bone tap using the protection sleeve.

The 4.0 mm cancellous bone screw to be inserted should come to rest with its threads completely beyond the fracture line.

Insert the second lag screw in the same manner as described above.

infrasyndesmotic medial fracture with lcl rupture

5. Postoperative treatment of infra- and trans-syndesmotic malleolar fractures

A bulky compression dressing and a lower leg backslab, or a splint, are applied, and the limb is kept elevated for the first 24 hours or so, in order to avoid swelling and to decrease pain.

In anatomically reconstructed, stable malleolar fractures, early active exercises and light partial weight bearing are encouraged after day one. In osteoporotic bone, weight bearing should be postponed.

X-ray evaluation is made after 1 week and then monthly until full healing has occurred. Progressive weight bearing is recommended as tolerated.