Bone fractures

• imagine someone is involved in a MVA or some other trauma and has a fracture. what happens?

• depending on severity and type of fracture, there is usually some bleeding

• associated with that bleeding is local death of the bone at the site of the fracture. there is hemorrhage and necrosis. this does not only involve the bone; it may also involve the marrow in the area of the bone

• the fibrous tissue as a result of healing is bony sclerosis, and this is how fractures heal

• some blood vessels may grow into this, and in the soft tissue surrounding the bone, there are always some cells that are potentially multipotent

• these cells can turn into stromal cells, etc, and accompany the blood vessels to grow into the site of fracture

• so, you have variable amounts of cartilage forming in this area of fracture

• this cartilage, depending on extent of fracture, might be totally replaced by new bone or may partially remain

• this type of cartilage is analogous to granulation tissue and subsequent scarring in soft tissue, except in bone the scarring is called a callus

Necrotic bone at the site of a fracture

• we can tell that the bone is necrotic because the osteocytes are absent

• necrotic fat cells manifest as large vacuoles, and these are associated with multinucleate giant cells

• so in the bone there is both bony as well as fat necrosis in the initial phases of fracture

Subperiosteal bone formation

• this is happening both just below the periosteum as well as within the bone. this is the callus forming

• higher power view reveals highly cellular cartilage, and this is a cartilaginous callus

• callus can be misdiagnosed as a cancer if it is overly cellular

• pseudoarthrosis: bent healed bone almost looks like a joint

SEM of bone from the vertebral column

• microfractures occur on a daily basis

• microcalluses are visualized here; these occur every day

Rib fracture with callus formation

• looks a whole lot like a neoplasm

• fracture (as in joggers, dancers) leads to callus formation that most people would call a tumor

Category: Pathology Notes