Intramedullary pin

Intramedullary (IM) pin fixation is an option for A1 fractures in small to mid-sized breed dogs and cats.

The pin is introduced antegrade in a closed fashion.

For this procedure, the patient is placed in lateral recumbency.

For antegrade placement of the IM pin, the approach is made over the greater tubercle.

The length of the pin can be determined using fluoroscopy or measured on preoperative radiographs.

Note: The pin should not enter the supratrochlear foramen.

The IM pin diameter should be 70-80 % of the isthmus of the medullary canal. Alternatively, if a smaller pin diameter is used, more than one pin can be inserted.

Pitfall: If the pin is too small, it will not have adequate strength or bending stiffness to maintain stability.

A 1 cm stab incision is made directly over the craniolateral point of the greater tubercle.

Note: Care should be taken not to incise the omobrachial vein.

The IM pin enters the bone on the lateral slope of the ridge of the greater tubercle near its base.

Pearl: Cutting the sharp end of the pin reduces the risk of penetrating the supratrochlear foramen, especially in the soft bone of young animals. After having drilled the entrance hole, the pin can be retracted, the sharp end cut, and the pin reintroduced into the bone.

The pin is advanced until just proximal to the supratrochlear foramen.

The protruding IM pin is cut close to the greater tubercle.

The pin can also be bent, cut close, and positioned close to the greater tubercle.

Final construct.

The aim is to reduce edema, inflammation, and pain.
Integrative medical therapies, anti-inflammatory medication, and analgesics are recommended.

Note: Animals carry 2/3 of their weight on the front limb. Therefore, strict leash confinement or cage rest and no jumping are recommended until radiographs show signs of bone healing. Since fixation with IM pin is less rigid and stable than plate fixation, strict leash confinement is essential for this treatment method.

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

A careful evaluation is recommended if the dog does not start to use the limb within a few days after surgery.

Early ambulation is aimed for.

Radial nerve neurapraxia may occur in some cases. This neurapraxia resolves in most cases within a few days.

10-14 days after surgery, the sutures are removed.

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

Note: It can be challenging to assess bone union on radiographs when bone healing occurs without callus formation.