Info for radiographic positioning

Here are some basic guidelines for radiographs and positioning for the stifle issues we tend to deal with primarily, ACL tears. Our software uses Jpegs so when asked when you share or send them you may need to designate Jpeg vs. dicom

Cranial-caudal: The cranial-caudal view to the right is taken with the patient in dorsal recumbency and the joint in full extension. A close-up is used for illustative purposes. A full cranial-caudal view would include the hock and the hip joint. An un-rotated, straight image is important and may be achieved by slightly internally rotating the limbs. The cranial border of the tibia, also called the tibial crest, should be centered, and the fabellae should sit proximal to the femoral condyles and will usually overlap the distal femur to a variable degree.

One key to getting a good CC is that the medial fabella ( MF) and the lateral fabellae (LF )will overlap the femur about 50%.

Also we prefer to have each stifle on its own radiograph and view, but take at least one full pelvis and stifle cranial-caudal to show the coxofemoral joints and both knees as anatomically extended straight as you can. There are other views we sometimes will need to get measurements of version, anteversion, torsion. One anatomical mark for getting the femur in a good cranial-caudal is to visualize the minor trochanter on the medial proximal femur. If the femur is malpositioned the minor trochanter will not be seen due to the cortex.

With angular limb issues the CC is more difficult to get but stay focused on the fabella on the cranial-caudal view and the conyles on the laterals. It is necessary to see the coxofemoral joint and the tarsus to evaluate anatomical axes so always include them, but call and we can discuss those views if angular issues are suspected.

Lateral stifle radiographic positioning
If you are obtaining radiographs for a leveling osteotomy please make sure it is a lateral stifle with the hock and stifle present, the left and right markers, and some way to calibrate the radiograph. Putting a quarter adjacent to the leg will work in most instances.

In the lateral view, by far the most important aspects in getting good radiographic positioning and therefore measurements, are to have the femoral condyles overlapping as close to possible to looking like a single image and to have the stifle and hock included in the view, and accurately labeled right and left. Calibration is important also for surgical planning , so if not known if your images are calibrated always place an object or radiographic sphere that has a know diameter or length. Often a quarter is placed close to stifle. Take each stifle individually on its own view. The contralateral leg is very helpful and often needed. Below is a close up of an almost perfect lateral where the condyles are imposed over the top of each other. Note the hock is in the radiograph. The stifle and hock are placed at 90 degree angles.

Lateral stifle

Here is a close up of an almost perfect lateral where the condyles are imposed over the top of each other.

We must have the hock and the stifle in the radiograph with calibration to do an accurate surgical plan. The original work on getting accurate TPA measurements were based upon a good lateral position of the stifle with the knee and hock both at 90 degrees. The radiograph above is being used to illustrate good lateral view of joint with condyles overlapping correctly . For surgical planning using the TPA ( tibial plateu angle ) the hock has to be in the view to get measurements. Other views are used as well but this has been the traditional view.

We must have the hock and the stifle in the radiograph preferably at 90 degree angles some type of calibration to do an accurate surgical plan on an anterior cruciate ligament tear ( ACL ).