Cross pinning and transcondylar lag screw

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.

The cross pin technique may be considered if the fracture configuration allows for inherent stability when reduced.

The addition of crossed pins provides ancillary stabilization to allow healing with early range of motion of the joint. For maximal stability the pins must cross proximal to the fracture.

Proper alignment of the femur must be obtained with special attention to angulation and torsion, particularly in transverse fractures, where rotational malalignment is more likely to occur.

Comparison with the contralateral unaffected bone can be useful.

This procedure is performed with the patient placed in dorsal recumbency.

One of the following approaches is utilized:

• Lateral parapatellar approach
• Medial parapatellar approach
• Bilateral approach
• Percutaneous approach
• Tibial crest/turberosity osteotomy

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.

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.

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

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.

Two Steinmann pins or K-wires (depending on the size of the patient) are driven obliquely across the fracture plane to cross each other proximal to the fracture.

Insertion starts at the proximal aspect of the origin of the long digital extensor tendon, in the extensor fossa of the lateral femoral condyle.

Tip: Slight over reduction of the fracture prior to pin insertion helps ensure anatomic reduction when pins are seated. Otherwise, as the pins are inserted, the distal fragment moves caudal and can be under reduced.

The second pin is inserted at a similar level on the medial femoral condyle.

Tip: Alternately advancing each pin into the metaphysis can aid in maintaining fracture reduction.

Both pins should be 40-45 degrees to the long axis of the femur.

Pins should be advanced until they penetrate the cortex proximally.

Note: Case should be taken not to penetrate the articular surface.

Alternatively, the pins may be inserted using a modified Rush pinning/Dynamic cross pinning technique. In this case, the pin insertion sites are the same, except each pin is angled 20-30 degrees to the long axis of the femur. With the modified Rush/Dynamic cross pinning technique, the pins do not penetrate the cortex of the femoral diaphysis but create friction by bending and creating a “spring like” action against the endosteum.

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.

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.

Tip: Alternately advancing each pin into the metaphysis can aid in maintaining fracture reduction and should be used.

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.

Postoperative radiographs should be taken to assess the repair.

For a case example of this procedure please refer to the matching dog section of the AO Surgery Reference.

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

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.

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.

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.

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.