Osteomyelitis is an infection in a bone. Infections can reach a bone by traveling through the bloodstream or spreading from nearby tissue. Infections can also begin in the bone itself if an injury exposes the bone to germs.
In children, osteomyelitis most commonly affects the long bones of the legs and upper arms. Adults are more likely to develop osteomyelitis in the bones that make up the spine (vertebrae). People who have diabetes may develop osteomyelitis in their feet if they have foot ulcers.
Once considered an incurable condition, osteomyelitis can be successfully treated today. Most people require surgery to remove parts of the bone that have died — followed by strong antibiotics, often delivered intravenously, typically for at least four to six weeks.
In most cases, a bacteria called Staphylococcus aureus, a type of staph bacteria, causes osteomyelitis.
Certain chronic conditions like diabetes may increase your risk for osteomyelitis.
Bone is normally resistant to infection. However, when microorganisms are introduced into bone hematogenously from surrounding structures or from direct inoculation related to surgery or trauma, osteomyelitis can occur. Bone infection may result from the treatment of trauma, which allows pathogens to enter bone and proliferate in the traumatized tissue. When bone infection persists for months, the resulting infection is referred to as chronic osteomyelitis and may be polymicrobial. Although all bones are subject to infection, the lower extremity is most commonly involved.
Some important factors in the pathogenesis of osteomyelitis include the virulence of the infecting organism, underlying disease, immune status of the host, and the type, location, and vascularity of the bone. Bacteria may possess various factors that may contribute to the development of osteomyelitis. For example, factors promoted by S aureus may promote bacterial adherence, resistance to host defense mechanism, and proteolytic activity.
In adults, the vertebrae are the most common site of hematogenous osteomyelitis, but infection may also occur in the long bones, pelvis, and clavicle.
Primary hematogenous osteomyelitis is more common in infants and children, usually occurring in the long bone metaphysis. However, it may spread to the medullary canal or into the joint. When infection extends into soft tissue, sinus tracts may eventually form. Secondary hematogenous osteomyelitis is more common and occurs when a childhood infection is reactivated. In adults, the location is also usually metaphyseal.
Saureus is the most common pathogenic organism recovered from bone, followed by Pseudomonas and Enterobacteriaceae. Less common organisms involved include anaerobe gram-negative bacilli. Intravenous drug users may acquire pseudomonal infections. Gastrointestinal or genitourinary infections may lead to osteomyelitis involving gram-negative organisms. Dental extraction has been associated with viridans streptococcal infections. In adults, infections often recur and usually present with minimal constitutional symptoms and pain. Acutely, patients may present with fever, chills, swelling, and erythema over the affected area.
Contiguous-focus and posttraumatic osteomyelitis
The initiating factor in contiguous-focus osteomyelitis often consists of direct inoculation of bacteria via trauma, surgical reduction and internal fixation of fractures, prosthetic devices, spread from soft-tissue infection, spread from adjacent septic arthritis, or nosocomial contamination. Infection usually results approximately one month after inoculation.
Posttraumatic osteomyelitis more commonly affects adults and typically occurs in the tibia. The most commonly isolated organism is S aureus. At the same time, local soft-tissue vascularity may be compromised, leading to interference with healing. Compared with hematogenous infection, posttraumatic infection begins outside the bony cortex and works its way in toward the medullary canal. Low-grade fever, drainage, and pain may be present. Loss of bone stability, necrosis, and soft tissue damage may lead to a greater risk of recurrence.
Septic arthritis may lead to osteomyelitis. Abnormalities at the joint margins or centrally, which may arise from overgrowth and hypertrophy of the synovial pannus and granulation tissue, may eventually extend into the underlying bone, leading to erosions and osteomyelitis. One study demonstrated that septic arthritis in elderly persons most commonly involves the knee and that, despite most of the patients having a history of surgery, 38% developed osteomyelitis. Septic arthritis is more common in neonates than in older children and is often associated with metaphyseal osteomyelitis. Although rare, gonococcal osteomyelitis may arise in a bone adjacent to a chronically infected joint.
Patients with vascular compromise, as in diabetes mellitus, are predisposed to osteomyelitis owing to an inadequate local tissue response.
Infection is most often caused by minor trauma to the feet with multiple organisms isolated from bone, including Streptococcus species, Enterococcus species, coagulase-positive and -negative staphylococci, gram-negative bacilli, and anaerobic organisms. Foot ulcers allow bacteria to reach the bone. Patients may not experience any resulting pain, because of peripheral neuropathy, and may present with a perforating foot ulcer, cellulitis, or an ingrown toenail.
Physical examination may reveal decreased sensation, poor capillary refill, and decreased dorsalispedis and posterior tibial pulses. Treatment is aimed at suppressing infection and improving vascularity. However, most patients develop recurrent or new bone infections. Resection or amputation of the affected tissue is sometimes necessary. Debridement, incision and drainage, and tendon lengthening are attempted first.
The incidence of vertebral osteomyelitis generally increases progressively with age, with most affected patients being older than 50 years. Although devastating complications may result from a delay in diagnosis, vertebral osteomyelitis is rarely fatal since the development of antibiotics. The infection usually originates hematogenously and involves two adjacent vertebrae with the corresponding intervertebral disk. The lumbar spine is most commonly affected, followed by the thoracic and cervical regions.
Potential sources of infection include skin, soft tissue, respiratory tract, genitourinary tract, infected intravenous sites, and dental infections. S aureus is the most common isolated organism. However, Pseudomonas aeruginosa is more common in intravenous drug users.
Most patients with vertebral osteomyelitis present with localized pain and tenderness of the involved vertebrae with a slow progression over 3 weeks to 3 months. Fever may be present in approximately 50% of patients. Fifteen percent of patients may have motor and sensory deficits. Laboratory studies may reveal peripheral leukocytosis and an elevated erythrocyte sedimentation rate. Extension of the infection may lead to abscess formation.
Osteomyelitis in children
Acute hematogenous osteomyelitis usually occurs after an episode of bacteremia in which the organisms inoculate the bone. The most common organisms isolated in these cases include S aureus, Streptococcus pneumoniae, and Haemophilus influenza type b (less common since the use of vaccine for H influenza type b).
Acute hematogenous S aureus osteomyelitis in children can lead to pathologic fractures. This can occur in about 5% of cases with a 72-day mean time from disease onset to fracture.
Signs and symptoms of osteomyelitis include:
- Fever or chills
- Irritability or lethargy in young children
- Pain in the area of the infection
- Swelling, warmth and redness over the area of the infection
Sometimes osteomyelitis causes no signs and symptoms or has signs and symptoms that are difficult to distinguish from other problems.
To get to the root of pain, doctors can use several tests. This article provides an overview. Click here.
Quality-of-Life Scale for Pain
Quality of life scale is one tool that can help your doctor assess your pain. This same scale can help you and your doctor monitor improvement, deterioration, or treatment-related complications.
The most common treatments for osteomyelitis are surgery to remove portions of bone that are infected or dead, followed by antibiotics. Hospitalization is usually necessary.
Depending on the severity of the infection, osteomyelitis surgery may include one or more of the following procedures:
- Drain the infected area. Opening up the area around your infected bone allows your surgeon to drain any pus or fluid that has accumulated in response to the infection.
- Remove diseased bone and tissue. In a procedure called debridement, the surgeon removes as much of the diseased bone as possible, and takes a small margin of healthy bone to ensure that all the infected areas have been removed. Surrounding tissue that shows signs of infection also may be removed.
- Restore blood flow to the bone. Your surgeon may fill any empty space left by the debridement procedure with a piece of bone or other tissue, such as skin or muscle, from another part of your body.
Sometimes temporary fillers are placed in the pocket until you’re healthy enough to undergo a bone graft or tissue graft. The graft helps your body repair damaged blood vessels and form new bone.
- Remove any foreign objects. In some cases, foreign objects, such as surgical plates or screws placed during a previous surgery, may have to be removed.
- Amputate the limb. As a last resort, surgeons may amputate the affected limb to stop the infection from spreading further.
A bone biopsy will reveal what type of germ is causing your infection, so your doctor can choose an antibiotic that works particularly well for that type of infection. The antibiotics are usually administered through a vein in your arm for at least four to six weeks.
An additional course of oral antibiotics may be needed for more-serious infections.