2010 Radiology Exam - Musculoskeletal Case 1

SIGNALMENT: 8mo MC canine Labrador Retriever

HISTORY: Hindlimb lameness

IMAGES AVAILABLE: Right Stifle – lateromedial and caudocranial.

See images below. Click to enlarge.

EXPECTED DESCRIPTIONS TO INCLUDE:

Findings

• Irregular articular margin on medial femoral condyle with adjacent sclerosis.
• Increased soft tissue opacity in stifle joint space – various ways to describe this.
• Increased medullary opacity in femoral diaphysis.

Synthesis

• Medial femoral condyle osteochondrosis with joint effusion and/or synovial thickening.
• Panosteitis

Management

• Radiographs of the contralateral stifle – as the osteochondrosis can be a bilateral condition.
• Radiographs of the femur – if not sure about the increased medullary opacity. The lateral femur radiograph was available and had more extensive patchy increased medullary opacity consistent with panosteitis.

SUMMARY OF OVERALL CANDIDATE PERFORMANCE:

• It was expected that candidates would know that multiple lesions are possible in this age canine where panosteitis, developmental, congenital and traumatic lesions are not uncommonly concurrent. This case was a good example of “satisfaction of search”, meaning an incomplete evaluation of the study by stopping after finding a lesion. Most candidates diagnosed only a single lesion, with the majority identifying only the medial femoral condyle lesion and two diagnosing only the panosteitis. Only a few candidates successfully diagnosed both lesions. Two of the candidates described the increased medullary opacity but dismissed it as artifact, image mottle or summation of overlying soft tissues without trying to rule out other possibilities.
• Many candidates over-interpreted degenerative changes to the stifle, but were not penalized as mild changes could be equivocal.
• Several candidates described the medial femoral condyle irregularity on the caudocranial view but stated they could not see it on the lateral view and often pointed to the incorrect area, typically too caudal on the articular surface. They did not demonstrate understanding of the principle of how the x-ray beam is tangential to the surfaces and how that affects the image projected, which in this case would be affected by the fact that a caudocranial view is made with the limb more extended than the lateral image.