Issue 15   -   March 2015

Animg header
New to Animal Imaging!
3 Tesla MR imaging of the equine stifle

Pathology of the equine stifle can be challenging to definitively and accurately diagnose. We are excited to discuss a few imaging options available at Animal Imaging. After the referring veterinarian performs a lameness exam, including localization of the lameness to the stifle with regional anesthesia, radiology is often the first procedure performed. Our equine board certified radiologists, Dr. Neelis and Dr. Biscoe are available to consult with the referring veterinarian on radiographs obtained. The next step is often ultrasound of the joint. Both Dr. Neelis and Dr. Biscoe have trained extensively in equine ultrasound prior to and during their  radiology residencies. If any uncertainties regarding the pathology remain present, select cases can be imaged with our 3 Tesla MRI. The 70cm bore is large enough to accommodate most horses of average frame. Treatment protocols will be managed by the referring veterinarian. If you would like to discuss if your patient is a good candidate for imaging of the stifle in the MRI, please do not hesitate to give our doctors a call.  

3T MRI Imaging of the Equine Hock - Bone Edema
Patient History

A 5 year old Quarter Horse Gelding presented to Animal Imaging for an MRI of the left hock in early October 2014. An acute grade 4/5 left hind lameness was noted after a work, a week prior to our diagnostic studies. The lameness was localized to the hock by the referring DVM with intra-articular anesthesia of the tarsal-metatarsal joint and distal intertarsal joint. Lower limb blocks were unsuccessful in alleviating the lameness. No palpable swelling or pain was noted upon evaluation of the left hind limb. A region of interest scintigraphic exam was performed to rule out any stress fracture.  
Intense Uptake Tarsus
Scintigraphic/Radiographic Findings:

An intense focal area of uptake was noted in the proximal lateral aspect of the MT3. Radiographs of the hock and proximal aspect of the MT3 were within normal limits. The patient was scheduled to compete in an important upcoming event, therefore an MRI was requested to better understand the extent of the pathology in the left hind limb.
MRI Findings:

A focal region (1.4cm x 2cm) of increased fluid signal was identified within the mid to dorsal lateral aspect of the third metatarsal bone. A small focal bone/wedge-shaped hyperintense STIR defect was noted in the dorsal lateral aspect of the third metatarsal bone. On the T1 images, a focal hypointensity extended distally from the tarsal-metatarsal joint which indicated a small non-displaced fragment. The patient was rested, treated, and improved clinically by seven weeks post accident, therefore a follow-up MRI was requested. The MRI at six weeks revealed resolution of the bone edema-like changes of the third tarsal bone and proximal third metatarsal bone. The small linear hyperintensity which extended distally from the tarsal-metatarsal joint was not as apparent on the recheck study, likely associated with healing.

Impressions and Recommendations: 
This case illustrates the pain that is often caused by an acute accumulation of fluid, or bone edema, within any given area of damaged bone. Near complete resolution of the bone edema was evident at seven weeks post injury. Clinically, the patient was sound. The separate but related lateral proximal MT3 subchondral defect and non-displaced fragment also improved. A residual cyst-like lesion remained in the lateral aspect of the tarsal-metatarsal joint, which hopefully is manageable. An MRI evaluation was beneficial in this case:  to arrive at initial diagnosis, formulate a treatment plan, and evaluate the response to therapy. The patient competed successfully in a later event.
 Copyright 2012. Animal Imaging.