Double PCL sign - appears on sagittal MRI images of the knee when a bucket-handle tear of a meniscus (most commonly the medial meniscus) flips medially and comes to lie anteroinferior to the posterior cruciate ligament (PCL), mimicking a second smaller PCL.
Spinnaker sign - a neonatal chest radiograph sign of pneumomediastinum. It refers to the thymus being outlined by air with each lobe displaced laterally like spinnaker sails. This appearance may also be termed the thymic wing sign. Bonus radiology signs also demonstrated in this case include left-sided deep sulcus sign of pneumothorax and continuous diaphragm sign of pneumomediastinum.
- Lamellated, layered or onion skin
- Codman triangle
- Spiculated, sunburst or hair on end
Although periosteal reactions may be seen in young and adult populations, the relatively loose attachment and active physiology of the periosteum in children leads to an earlier and more robust reaction to underlying pathology, and is a more sensitive indicator of disease. Lack of a periosteal reaction in adults, who have a tightly adhered and relatively inactive periosteum, is not unusual, even with highly aggressive underlying pathologies. (see the example of adult primary osteosarcoma at the bottom of this post)
Primary osteosarcoma in an adult male. Note the absence of a periosteal reaction.
The term licked candy stick appearance refers to tapering of the tips of the metacarpal / tarsal bones, phalanges or clavicles. This finding can be seen in advanced cases of:
Psoriatic arthritis: enthesitis and marginal erosions destroy the peripery of the bone, leaving a thinned central region. This also leads to the "pencil in cup deformity".
Rheumatoid arthritis: marginal erosions and destruction of the joint, due to destructive pannus, also may leave a tapered portion of bone.
Leprosy: atrophy and resorption of bone due to deinvervation, begins distally in the colder regions of the body and progresses proximally.