Hi, this is Sagar Wagle, one of the musculoskeletal radiology fellows at Stanford University. We have a case of a 14 year old male with one week of lateral knee pain. The differential is broad. These are the images from the patient. Let's talk about osteochondromas. Osteochondromas are benign bone tumor and one of the main characters of osteochondroma is that the cortex and the medullary cavity of the underlying bone is continuous with the osteochondroma. They also have a cartilage cap that we do not see on radiographs, but can be seen on MRI. This image is of a 23 year old girl and she was having pain from this osteochondroma during physical activities such as running and bicycling and she underwent surgical resection of the osteochondroma. Here we have a case of hereditary multiple exostosis where patient has multiple osteochondromas, for example in the distal femur, fibular head, posterior tibia, anterior tibia, and here we're seeing the same osteochondromas and again, we can see that the cortex and medullary cavity of the underlying bone is continuous with the osteochondroma. A diagnosis of an osteochondroma does not need MRI, but if there is concern about cartilage cap or malignant transformation or pain in area related to adventitial bursal formation, then an MRI could be obtained. Here we can see on the MR osteochondroma on the fibular head, posterior femur, posterior tibia, and anterior tibia, and we're going to look at them one more time. Here osteochondroma on the fibular head, posterior femur, posterior tibia, anterior tibia, and here we can see that this osteochondroma has a cartilage cap and the cortex and the medullary cavity of the underlying bone is continuous. Some aggressive lesions could be mistaken for osteochondroma, but it is important to remember that osteochondroma has medullary and cortical continuity. Here on the left, we have a case of a sarcoma. This is case of a parosteal osteosarcoma, and we can see that the cortex and the medullary cavity is not continuous as compared to the osteochondroma on the right. This is the same sarcoma on MRI. We can see a big mass that extends into the bone and outside the bone, and the patient was treated with surgical resection of distal femur and placement of a prosthesis. And here again, we can look at the sarcoma and compare this to our osteochondroma. So in our case, the patient has osteochondroma, and we can see that the cortex and medullary cavity is continuous. The deformity that we see on the distal thigh is due to underlying osteochondroma. On this surgical image, we can see the cartilage cap and the osteochondroma was surgically resected. Thank you for watching the video.

3rd Edition, CASE 41

3rd Edition

Oncology

osteochondromas

musculoskeletal radiology

knee pain

hereditary multiple exostosis

malignant transformation