Exostosis-not always easy to identify!

Young Skeleton with pain after fall  shows exophytic opacity outwards from the metaphyseal location of humerus with undisplaced fractures in the vicinity  with almost 2 Humeral heads appearance   suggesting exostosis with suspicion for   secondary chondrosarcoma  of cartilage cap. MRI is needed for further evaluation.

Teaching points by Dr MGK Murthy, Dr Sumer Sethi.

·         Defined as developmental dysplasia of peripheral growth plate which forms cartilage cap  projection of bone near metaphysis of long bones. Peripheral chondroblast grows  outwards acting as ectopic growth  plate , stopping at maturity

·         Most common benign bone tumor. Any bone forming in cartilage can get involved

·         X ray hallmark is blending of tumor in to  the underlying metaphysis  along with calcification of cap elements 

·         Only 1% solitary  ones can turn secondary chondrosarcoma  at the cap , with  10%  in multiple variety

·         Cartilage cap measuring >1cm in adults and 2-3 cms in children on MRI along with  sudden increase in bone scan uptake in adults  is of concern

·         Other complications include bursal formation