Here is the answer to our latest imaging case. The horse has fractured a piece of bone (red arrow on image 1) off the back of its radial carpal bone, one of the bones in the top row of bones in the carpus. In this case, it is relatively easy to see the main fracture but in some cases it can be very difficult to interpret radiographs of the carpus as there are many bones that are ‘superimposed’ on top of each other. For this reason we always take multiple x-rays at different angles. However, it can still be easy to underestimate the complexity of a fracture. A CT scan can be extremely useful in these cases, as it allows a detailed cross-sectional view of the structures with high spacial resolution. This eliminates problems with conventional, two-dimensional imaging, such as superimposition. It also affords the surgeon excellent surgical planning, as each individual fragment can be localised prior to surgery. The horse is anaesthetised as normal for the surgery but prior to going into theatre, the CT scan is performed. This only adds about 15 minutes onto the length of the anaesthetic and is extremely valuable in cases such as this. Image 2 is a single “slice” taken from the CT scan, showing a greater complexity of the fracture than can be ascertained from the radiograph. The red arrow labelled A is pointing to the main fragment of bone we could see on the radiograph. The red arrow labelled B is pointing to a separate fragment off the bottom of the same bone that is difficult to see on the radiograph. The green arrow is pointing to a normal gap between two bones. The CT scan can be reconstructed in any plane (image 3), allowing us to look at the structures in any orientation. This is a CT slice orientated in a transverse plane showing the complexity of the fracture. Image 4 is a computerised 3D reconstruction of the CT scan showing the fragments.
Posted on: Sun, 04 May 2014 23:52:32 +0000