There are several different ways to develop the bone infection of osteomyelitis. The first is for bacteria to travel through the bloodstream (bacteremia) and spread to the bone, causing an infection. This most often occurs when the patient has an infection elsewhere in the body, such as pneumonia, an abscessed tooth, or a urinary tract infection that spreads through the blood to the bone. An open wound over a bone can lead to osteomyelitis. This happens most commonly with underlying peripheral vascular disease, peripheral neuropathy, or diabetes. With an open fracture (compound fracture), the bone that punctures through the skin is exposed to bacteria. This increases the risk of osteomyelitis. A recent surgery or injection around a bone can also expose the bone to bacteria and lead to osteomyelitis. Patients with conditions or taking medications that weaken their immune system are at a higher risk of developing osteomyelitis. Risk factors include cancer, chronic steroid use, sickle cell disease, human immunodeficiency virus (HIV), diabetes, hemodialysis, intravenous drug users, infants, and the elderly.