Bone Infection (Osteomyelitis) Basics

 

So you’ve been told you have osteomyelitis, or you might have osteomyelitis.  That’s a five dollar word for bone infection.  Read on to get a few facts about this condition, and where it may lead you in the short term.

Staph Aureus is the most common causative organism

Bone infection means that a bacteria has gotten through the skin and soft tissues (tendons, ligaments, fat) and has penetrated the bone.  It’s important to note that this rarely happens in healthy individuals unless some trauma has penetrated all the way to bone, or has exposed bone.  In those with diabetes, peripheral vascular disease, and other conditions resulting in a weaker immune system infections will persist and can spread further than would be possible in the presence of a healthy immune system.

There are many different types of bacteria, many may cause osteomyelitis, but the most common causative organism is staph aureus.  One type of staph aureus that is more pathogenic is MRSA (methicillin resistant staph aureus), which has become more common in hospitals and in the community.

Most common type of osteomyelitis in adults is direct spread

There are several different types of osteomyelitis.  The more common type in adults is called direct spread (contiguous).  This means that the bacteria started in the skin and then proceeded through soft tissues until it hit bone.  There has to be a break in the skin for this to occur, and may be due to trauma such as a cut or scrape that becomes infected.  In those with neuropathy there is often a callus which formed, and then and ulcer beneath which became infected.  This is why for diabetic, prediabetic or high risk individuals it is so important to do a daily foot exam.

Osteomyelitis doesn’t happen overnight

It takes time for the bacteria to move from the skin to the bone, even if the skin is directly overlying the bone.  The good news is that this is quite a long distance for the bacteria to travel, the bad news is that we are one of the favorite food groups for bacteria.  The bacteria will multiply rapidly while eating it’s way to our bones.

Again, as noted above, if you are doing a daily foot exam you should notice changes such as redness, swelling, maybe pain (but not if you have neuropathy), and possibly drainage from the wound. Neuropathy is different in each individual, in denser (more complete) peripheral neuropathy no surface pain will be felt.  However, once infection is in the bone a deep ache or actual pain may be felt.

Why is osteomyelitis so difficult to treat?  

Imagine a child is hiding from you in your house.  They have decided that they don’t want to be found or bothered, so instead of simply hiding behind a chair or a curtain, they create a brick wall to completely hide themselves.  Sounds drastic? Unrealistic?  Or does this sound like your kids?  

As the bacteria breaks through the outer layer of bone, it is often under siege by the body’s immune system.  The resulting chaos results in pus formation and bone destruction.  The dead bone is called sequestra.  The body will begin forming new bone which is called involucrum, often with the bacteria within.  The bacteria also form biofilms which are protective layers very difficult for antibiotics to penetrate. When the involucrum becomes large enough it is visible on xrays.  

Treatment with antibiotics or surgical debridement

Treatment options largely falls into two main camps.  One is some duration of antibiotics (antibacterial medication), and the other treatment is surgical debridement (removal) of the bone.  Antibiotics may be via mouth (oral or PO) or intra-venous (IV).  Many factors go into which route is appropriate, and the duration.  For treatment of osteomyelitis treatment often lasts four to six weeks, and may last months.  Surgical treatment consists of removing part or all of the infected bone.  An MRI will often be ordered in advance for surgical planning, the MRI gives more information about the extent of the infection and which bones may need to be removed.  

So there you have five basic things about osteomyelitis.  Stay tuned for a more in depth article where we will talk about diagnosis, and further about treatment options and post-operative care.  Remember that many of these infections might have been avoided if the patient had been doing daily foot inspections and had sought care earlier in the course of the infection.

 

For more information on the diabetes team look here.

 

For more information on the role of a surgically trained podiatrist look here.