Interlocking nail

Fracture types:

A) Comminuted, unreduced fracture
B) Comminuted fracture aligned biologically
C) Fracture aligned and biologically stabilized

Diameter, length and depth of ILN insertion are determined by preoperative planning using the radiograph of the opposite intact tibia if available.

The nail’s largest diameter should be approximately 75% of the medullary cavity at the tibial isthmus. The longest possible nail should be selected to optimize construct stability. ( Dejardin et al. Interlocking nail and minimally invasive osteosynthesis. Vet Clin Small Anim. 2012; 42:935–962)

It is usually advantageous to have the patient in dorsal recumbency and the stifle flexed at a right angle.

In the tibia the only acceptable nail insertion technique is normograde. After the approach for normograde nail insertion is made, the medullary cavity is opened using an intramedullary pin or a dedicated awl.

The pin is started close to the medial border of the tibia plateau and angled slightly medially and caudally. After entering the marrow cavity, decreased resistance will be felt.

Entering the pin too far caudally in the stifle joint will not allow full extension of the stifle joint when the nail is placed because of interference of the nail with the femoral condyle.

Depending on the type of nail used, further reaming of the medullary canal in the distal fragment may be required. This is done to allow nail placement into the distal segment.

The nail is coupled to an insertion handle via a nail extension. It is introduced along the anatomical axis of the tibia and inserted into the medullary canal of the proximal segment by hand or gentle hammering. The fracture is aligned while the nail is inserted further into the distal segment.

The nail is directed into the distal segment using fluoroscopic guidance, closed palpation, or visualization through an open-but-do-not-touch approach to the fracture site. A mallet is used to fully impact the nail into the intramedullary canal, until deeply seated in the distal metaphysis or epiphysis.

Once the bone length has been restored, it is necessary to check for correct alignment and rotation.

Rotational alignment can be judged by palpation or by direct visualization of the relation between the tarsus and the stifle.

Flexing and extending the tarsus and stifle will help to check the alignment of the repair.

Note: Position of the cat in dorsal recumbency permits a better three-dimensional view of the tibia, thus it helps in the verification of alignment.

Once adequate reduction, alignment and proper nail insertion are confirmed, placement of the bolts or locking bolts is achieved through the use of an alignment guide coupled to the nail.

The alignment guide and nail extension are removed at the end of the procedure.

The aim is to reduce the edema, inflammation and pain and to protect the surgical wound. A compressive bandage or modified Robert Jones bandage can be used. Integrative medical therapies, anti-inflammatory medications (note in the cat that many are toxic; only use drugs labeled for cats) and analgesics are recommended. In most cases, 10-20 minutes of ice therapy is recommended every 8 hours, but maybe challenging in cats.

The aim is to resolve the hematoma, edema and control pain, and prevent muscle contracture. Analgesic medications may still be needed. Anti-inflammatory medications used in the cat are not labeled for continued use after a few days and should be avoided. Rehabilitation and integrative medical therapies can be used.

If the cat is not starting to use the limb within a 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.

More information about implant removal can be found here.