Authors of section

Author

Mary Sarah Bergh

Executive Editor

Amy Kapatkin

General Editor

Noel Moens

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Dynamic cross pinning and transcondylar lag screw

1. Principles

Anatomic reconstruction of the joint surface is essential, and it should be performed prior to fixation of the condyles to metaphysis.

Interfragmentary compression is achieved with a lag screw for anatomical reduction of the articular fracture.

Note: This technique does not provide rigid stability. Ideally, it should be used in patients that will heal quickly, or when other techniques are not possible.

Cross pinning and transcondylar lag screw fixation in a type C1 fracture in a distal femur of a dog

2. Positioning and approach

This procedure is performed with the patient placed in dorsal recumbency

One of the following approaches is utilized:

transcondylar lag screw and neutralization plate

3. Surgical technique

Reduction and stabilization of the femoral condyles

The articular fracture of the condyles is reduced with pointed reduction forceps. Anatomic reduction is essential in all cases.

Note: Bone in juvenile patients is very soft. Care must be taken not to damage it during reduction.

The articular fracture of the condyles is reduced with pointed reduction forceps

Screw insertion

Stabilization is achieved with inserting a screw in lag fashion across the condyles perpendicular to the fracture plane. Frequently the screw is placed in lateral to medial direction, starting at the level of the epicondyle.

Note: Care should be taken not to penetrate the condylar fossa to avoid damage to the cruciate ligaments with the screw.

A detailed description of "Lag screw fixation" can be found here.

Stabilization is achieved with inserting a screw in lag fashion across the condyles perpendicular to the fracture plane

Definitive stabilization of the smaller fragments of the condyles may be performed using lag screws or K-wires.

Note: If the screw head or K-wire is positioned in the articular surface they must be countersunk to avoid interference with intraarticular structures.

If the lag screw is not placed perpendicular to the fracture plane, this will result in loss of anatomic reduction of the articular surface

Reduction and stabilization of the condyles to the metaphysis

The reconstructed femoral condyles are carefully reduced to the metaphysis with pointed reduction forceps. Anatomic reduction is desired in all cases. Under-reduction of the fracture should be avoided as it is less stable, and the cranial aspect of the metaphysis may interfere with the gliding of the patella in the trochlear groove.

Note: Bone in juvenile patients is very soft. Care must be taken not to damage it during reduction.

The reconstructed femoral condyles are carefully reduced to the metaphysis with pointed reduction forceps

Rush pinning/Dynamic cross pinning

The pins may be inserted using a modified Rush/dynamic cross pinning technique. In this case, the pin insertion sites start at the proximal aspect of the origin of the long digital extensor tendon, in the extensor fossa of the lateral femoral condyle.

Each pin is angled 20-30 degrees to the long axis of the femur.

Due to the anatomical differences between the canine and feline femur, this technique is easier to perform in the cat, as there is less caudal curvature in the distal femur.

Distal femoral fracture in a dog repaired with Rush pinning technique and lag screw

As the pins are advanced they bounce off the endosteal cortex and slide up the medullary canal. Advancement of the pins stop when they reach the proximal metaphysis.

Pearl: The depth of penetration of the pin is measured using a pin of same size as a reference, by holding it outside the bone.

Pin insertion with Rush pinning technique

Cutting the pins

The pins can be cut flat with the bone surface, countersunk with a pin punch or bent over and then cut short.

Note: Care should be taken if the bone is very soft, as bending the pin may cause damage to the bone.

The pins can be cut flat with the bone surface or bent over and then cut short

Validation of fixation

Postoperative radiographs should be taken to assess the repair.

cross pinning and transcondylar lag screw

4. Aftercare

Activity restriction and controlled walking is indicated until evidence of bone healing is detected by radiographic examinations.

cross pinning

Phase 1: 1-3 day after surgery

The aim is to reduce the edema, inflammation and pain using anti-inflammatory and analgesic medications.

Passive range of motion of the hip and stifle joint can be initiated to promote mobility and joint health.

cross pinning

Phase 2: 4-10 days after surgery

The aim is to resolve the hematoma, edema and control pain, and prevent muscle contracture.

Anti-inflammatory and analgesic medications are still 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, as they are at risk for developing quadriceps contracture. Early controlled activity and passive range of motion is strongly recommended to help prevent this complication.

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

cross pinning

Phase 3: 10 days-8 weeks after surgery

Rehabilitation therapy is continued.

10-14 days after surgery the sutures are removed.

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

cross pinning

Implant removal

Implants may be removed if there is irritation or infection present, however if they are not causing problems for the patient, there is no need for implant removal.