Hello and welcome to HCM,
The CT report of the lower limb suggests a lesion called non-ossifying fibroma
Before explaining you the meaning of this term, I would like to give you brief over view.
The ends of long bones (tibia
in your case- tibia is one of the long bones of leg) has two parts- epiphysis
In health, the ends of the bones are cartilaginous. As the child grows the cartilage
is replaced by bone.
This process is called ossification.
In some conditions, the ossification does not occur.
Instead the cartilage is replaced by fibrous tissue only without any evidence of ossification.
In the absence of ossification, the bone is soft, appears translucent on X-ray, is not strong enough and breaks easily.
This is exactly what is happening in your son's bone of the leg (tibia).
As the bone is weak it has undergone a pathological fracture
(i.e. fracture due to disease of the bone and no due to any kind of trauma).
You need to consult an orthopedician for further management.
Thanks and take care.
Dr Shailja P Wahal