42-A1 are incomplete fractures of the tibial/fibula diaphysis. The tibia and fibula are paired bones. If one of them is fractured and the other one is intact, they are also classified as “incomplete”.
Incomplete fractures are very rare and typically occur in young animals affected by metabolic pathologies, such as nutritional secondary hyperparathyroidism. Fractures of only one of the two bones are occasionally encountered from minor trauma. They are generally simple minimally displaced fractures.
Radiographs of a 5-month-old Feline Domestic short hair who sustained a 42-A1 fracture of the distal diaphysis after falling down the stairs.
The tibia has an S-shape in the frontal plane. In the sagittal plane, cat tibias are straighter than in dogs. Even though this will not influence the fracture fixation method, it is important to bear it in mind when reconstructing the fracture and restoring the normal anatomy.
The fibula at the level of the tibia midshaft is very thin. For this reason, fractures of the fibula are generally not addressed.
42-A type fractures generally result from low energy trauma.
Clinical signs observed in 42-A fractures are:
Swelling of the region
Abnormal movement in the tibia shaft
Cats with A1 type fractures may present with mild to severe non-weight bearing lameness. Cats with incomplete fractures may still be able to use the limb.
Craniocaudal and lateral radiographic views are needed.