Orthopaedic Quiz 2
62 year old male attends your clinic with the following knee x-ray:
View 1
View 2
View 3
Case Source
Question 1
Name the above 3 views.
Hover over the icon for the answer:
View 1: Frontal, View 2: Lateral, View 3: Skyline
Question 2
What diagnosis is this x-ray suggestive of?
Answer:
Bilateral osteoarthritis (OA) of the knee
Question 3
What features of the above x-ray are suggestive of this diagnosis?
Answer:
Varus deformity of the knee, narrowing of joint space in the medial tibiofemoral and lateral patellofemoral compartments, small osteophytes at lateral margins, subchondral sclerosis, moderate joint effusion
The patient underwent a bilateral total knee replacement. Two years later he represents with left knee pain but normal WBC count and mildly raised inflammatory markers. There is clinical suspicion for prosthetic infection, so In-111 WBC (left) and Tc99-Sulfur Colloid (right) scans are performed together for evaluation.
Question 4
Is there an infection of the left knee replacement?
Answer:
No
Question 5
Justify your above answer.
Answer:
The In-111 WBC scan is sensitive for inflammation, however false positives can occur in the setting of aseptic loosening. In order to improve specificity when concerned for osteomyelitis, a Tc99-Sulfur Colloid scan be performed simultaneously. On the Sulfur Colloid scan, areas of increased uptake on the WBC scan that represent infection should show decreased uptake. Increased uptake on both studies is therefore suggestive against infection.