33-A1 Simple extraarticular fracture

Type A1 fractures are simple extra-articular fractures of the supracondylar region.

Shown are mediolateral and craniocaudal radiographs of a skeletally mature mis-breed dog with a 33-A1 fracture of the distal femur. Note the simple fracture configuration.

Distal femoral fractures account for 20-25% of all fractures of the femur. Early identification and surgical management are essential to optimize outcomes, especially in articular and physeal fractures.

High-velocity injuries of the distal femur often present as comminuted fractures. Low-velocity injuries dissipate less energy and normally result in two-piece fractures such as physeal fractures, or transverse fractures of the distal femur.

The small bone stock available for fixation in the distal fragment makes treatment of these types of fractures challenging.

Type A fractures account for approximately 85-90% of distal femoral fractures.

33-A1 and A2 type fractures generally result from low energy trauma, whereas A3 fractures are caused by high energy trauma.

33-A1 and A2 type fractures are the most commonly seen fractures of this region. In the juvenile animal, they may occur through the physis and are classified as Salter-Harris type I and II fractures, respectively.

Among the skeletally mature animals, chondrodystrophic dogs are predisposed to type 33-A fractures due to anatomic variances in the shape of the distal femur. Such breeds typically have an increased caudal angulation to the distal femur and a prominent concavity along the popliteal surface of the bone.

Clinical signs observed in 33-A fractures are:

• Pain
• Swelling around the distal femur
• Lameness of the affected limb
• Wounds: open fractures are possible

Good quality mediolateral and craniocaudal radiographs are essential for fracture evaluation. The entire femur should be included in each radiograph.

If more information is needed, computed tomography should be considered.