2007 Radiology Exam - Musculoskeletal Case 1

Information Provided to Candidate

  • Mix Breed Dog
  • 3 months
  • Female
  • Up to date on vaccination regime
  • Reluctance to walk and intermittently anorexic for 1-2 weeks
  • Stilted gait all four limbs

State the radiographic findings

  • What is your assessment of these findings?
  • Are further imaging studies needed? If so, what are they and why? If no, why not?

See images below. Click to enlarge.

Findings Expected from Candidate
The candidate was presented with original hard copy radiographs. On a ventrodorsal view of the pelvis, the candidate was expected to report the metaphyseal lucencies apparent in the femoral necks, femoral condyles and proximal tibias. Being cognizant of the history, the candidate was expected to ask for radiographs of the forelimbs. The radiographs of the forelimbs showed similar areas of metaphyseal lucency in the proximal and distal radius and distal ulna bilaterally and in the right distal humerus.
The important radiographic finding was cortical bone destruction with an ill-defined transition zone and loss of corticomedullary distinction, primarily in the metaphyseal region of all the long bones imaged in the study.

Conclusion Expected from the Candidate
The candidate was expected to recognize that this was an aggressive process resulting in bone destruction rather than failure of ossification. The differentials for these findings had to include hematogenous osteomyelitis. Another differential to consider in this case is juvenile osseous lymphoma.
The radiographic findings are NOT typical of hypertrophic ostedystrophy (HOD).

Summary of Overall Candidate Performance
Most candidates did extremely poorly on this case. HOD was the most common, and often only differential given. Realizing that this is an aggressive process is pivotal in managing this case. Very few candidates even mentioned sepsis and those that did, often listed it without giving any thought to actually prioritizing it. While one cannot be definitive that this is sepsis based on the radiographs, alerting the clinician that this is not just atypical HOD and stressing that this is an aggressive process is the important point in this case. Managing this case for HOD or ‘some type of metaphyseal dysplasia’ would have resulted in disastrous consequences for this patient.

Followup:
Blood cultures confirmed a bacteremia and the patient was started on antibiotics and made a full recovery. Cause for the bacteremia was never established.