Taking Great Stifle X-rays!
The stifle is the joint most frequently noted to have acquired injury. Part of the work up typically includes well positioned radiographs. In the development of the tibial plateau leveling osteotomy (TPLO), Dr. Barclay Slocum devised a technique of positioning that produced consistent lateral and posterior/anterior radiographs. Even though this positioning method is necessary for the preoperative measurements needed for the TPLO, it has become the standard for all stifle radiographs in our hospitals.
Here is how to do it:
Patient cooperation is essential! After a thorough physical evaluation and the patient is found to be in good cardiovascular health, the majority of our radiographs are done under sedation using dexdomitor (1/2 the label dose) and torbugesic (0.1mg/kg) given IV. This is welltolerated in healthy dogs and is then reversible, allowing the client to take their dog home within 30-45 minutes of administration. Your staff will also appreciate not having to hold wiggly dogs under an x-ray beam and will have reduced exposure as they can leave the room to take the radiograph with these techniques.
Lateral – the patient is placed in lateral recumbency on the x-ray table.
- The stifle to be radiographs needs to be the down limb.
- The stifle and hock are placed at ninety degrees.
- Center the X-Ray beam on the proximal, medial tibial – just distal to the stifle joint.
- Collimate to include the tibiotarsal joint (this will mean that ~ 40 % of the exposed area will proximal to the stifle).
- Bring the upper limb forward and hold with a sand bag. Moving the upper limb too far forward will tend to turn the lower stifle out of position.
Posterior/Anterior – The patient is placed in sternal recumbency.
- Extend the limb to be radiographed caudally with the hip and stifle in extension. A sand bag type weight on the pelvis may help hold the hip in extension.
- Place a rolled towel or foam under the inguinal area on the contralateral side that is to be radiographed.
- Place the patella so that it is centered under the stifle. This is the tricky part and is judged on the radiograph by noting if the patella is centered in the distal femur and both fabellae are bisected by the medial and lateral edges of the femur. In a straight limbed dog the medial border of the calcaneus will bisect the distal point of the center of the tibio-tarsal joint. Pulling on the paw to steer the patella tends to torque the hock and give an artificially mal-aligned appearing radiograph.