2011 Radiology Exam - CT/MRI Case 2

History
• 12 year old, female polo pony
• Left thoracic lameness of recent onset
• Lameness exacerbated by foot flexion
• Digital pulses of the left fore foot were increased
• No signs of right thoracic lameness

Images
• MR images of the left foot
• Sagittal and transverse T1-weighted images only

See images below. Click to enlarge.

Signs
• Linear hyperintensity affecting deep digital flexor tendon in sagittal images from the level of the navicular bone to the proximal interphalangeal joint
• Hyperintensity affects lateral lobe of the deep digital flexor tendon in transverse images; defect in tendon is largest on its dorsal aspect, with focal disruption of the dorsal border

Interpretation
• Partial thickness tear of the deep digital flexor tendon

Comments: A limited number of images were presented in order to avoid overloading candidates. 24% candidates did not gain a passing score for this case. The most common deficiencies in reports were inaccurate anatomic terminology (e.g. confusing flexor tendon for navicular bone or bursa), failure to include tear in the differential diagnosis, and invention of other lesions (e.g. swelling of coronary band).