Osteomyelitis can be broken down. Osteo- refers to bones, –myel stands for myelo and relates to the bone marrow, and lastly, –itis refers to inflammation.
So, osteomyelitis is an inflammation of the bone or bone marrow, and it typically results from an infection.
Normally, if we look at a cross-section of a bone, we can see that it has a hard-external layer known as the cortical bone and a softer internal layer of spongy bone that looks like honeycombs.
There’s also another layer called the periosteum that covers the cortical bone - like the lamination of a basketball card - and it's where the muscles, tendons, and ligaments are attached.
If we zoom into a cross-section of cortical bone, we can see that it has many pipe-like structures called osteons running through the length of the bone.
Each pipe has an empty center called a Haversian canal which contains the nerves and blood vessels that supply the osteon.
At the outer-border of the osteon is a ring of cells called osteoblasts which synthesize bone.
Along with these cells are osteoclasts that break down bone.
In bones, like the long femur bones, the tips of the bone are called the epiphysis, while the shaft is called the diaphysis of the bone.
Between the epiphysis and diaphysis, we have the metaphysis. It contains the growth plate, the part of the bone that grows during childhood.
In osteomyelitis, microorganisms, such as bacteria, reach the bone to cause an infection in a few different ways.
Bacteria particularly affect certain high-risk individuals like those with a weak immune system, and those with poor blood circulation due to uncontrolled diabetes.
In fact, a major way that bacteria reach the bone is through the bloodstream, and it's called hematogenous spread. For example, this might happen in a person who uses contaminated needles to inject drugs or in individuals undergoing hemodialysis that may be contaminated by a bacteria or even through the dental extraction of an infected tooth.
