Osteomyelitis is an inflammation of the bone. Usually, bacteria are the etiologic agents, but fungal infections can also occur. Osteomyelitis in children is primarily caused by hematogenous origins. In these cases, osteomyelitis occurs less commonly as a result of direct injury or trauma. In this population, osteomyelitis due to vascular insufficiency is not common.
Acute hematogenous osteomyelitis (AHO) is a disease that primarily affects children. This is due to the rich vascular supply of their rapidly growing bones. Infectious organisms usually enter the bone through the nutrient artery. They then travel to the metaphyseal capillary loops, where they are deposited. They replicate and initiative an inflammatory response.
Osteomyelitis is a disease that has been known since antiquity. It is accompanied by bone destruction and caused by a microorganism. The infection can be limited to a single portion of the bone or to several regions, such as the surrounding soft tissue, marrow, and cortex.
AHO evolves over a number of days or weeks. This is opposed to chronic osteomyelitis, which is a long-standing infection that evolves over months of years. Chronic osteomyelitis is a low-grade inflammation and is characterized by the presence of sequestrum (dead bone) and fistulous tracts.
AHO results from the bacterial seeding of bone. More than one-half of all cases of AHO are found in children, due to the rich vascular supply in their bones. Typically, symptoms occur within two weeks after the onset of the disease. These symptoms include irritability, fever, local erythema, and swelling. Tenderness over the involved bone can be observed. Chronic osteomyelitis is uncommon in children.
Chronic osteomyelitis occurs secondary to bacteremia, open fractures, or soft tissue infections. The incidence of significant infection is as high as 27% within three months after an open fracture. The incidence appears to be independent of the time between diagnosis and surgery or injury.
Individuals with AHO may be reluctant to use an extremity. They may also complain of fever and pain at the site of infection. Rarely, they may also have anorexia, vomiting, and malaise. Physical findings include focal swelling, warmth, tenderness, and erythema (usually over the long bone’s metaphysics). Aside from this, a draining fistulous tract may develop over the affected bone. The tenderness that is not promotional to soft tissue findings also suggests osteomyelitis. Exaggerated immobility of the joint, as well as lack of tenderness over the metaphysis, suggests pyogenic arthritis.
Osteomyelitis frequently occurs in the long bones. However, in some studies, 10-25% of cases involve short, non-tubular bones. These include the clavicle, calcaneus, scapula, ribs, and skull.
AHO refers to infections of the bone resulting from bacteria that is circulating in the bloodstream. This is most often seen in children, with initial infection thought to occur in the regions of the bone that are richly vascularized. Children are also seen to experience common episodes of bacteremia, and this often occurs with no symptoms, leading to the development of osteomyelitis. The pathogenesis of osteomyelitis has been described. The metaphyseal vessels become inoculated with bacteria at the transition point from the arteriolar vessels to the venous sinusoids. This slows the blood flow and increases vascular turbulence. These points of turbulence are predisposed to bacterial infection which provides an opportunity for local invasion.
If left untreated, hematogenous osteomyelitis may take on a chronic course. This is rare in developed countries. The events that follow this devastating condition may include chronic sinuses with the bone exposed, as well as the loss of structural integrity and growth disturbances.
Local trauma to the bone within the context of bacteremia may also be a precipitating factor. Animal studies have shown that there is a significantly increased rate of hematogenous osteomyelitis when the direct bone injury was combined with seeding of bacteria.
Risk factors for osteomyelitis are varied. One of the primary risk factors for osteomyelitis is decreased peripheral circulation, which may predispose the person to bacterial infection. Open wounds are another risk factor. This is the entry site of bacteria that may colonize the bone.
A prior history of osteomyelitis is another risk factor. People who have had osteomyelitis are at risk for having it again, although the mechanisms are not clear.
Poor glycemic control is another risk factor. Diabetes in patients is common. Those with osteomyelitis often have poor blood sugar control.
Malnutrition is another risk factor. Without adequate nutrition, individuals have weakened immune systems, which predisposes them to osteomyelitis and other infections. Furthermore, malnutrition depletes the body’s stores of calcium and vitamin D, which decreases the integrity of the bones.
Decreased sensation, due to neuropathy, can be a risk factor for osteomyelitis. Decreased sensation in the limbs affected by the infection will predispose the patient to invasive infections that are often difficult to detect. In addition, pain may not be felt because of desensitization.
Structural deformities in the bones are also factors that may predispose a person to osteomyelitis. These deformities may make it more difficult to diagnose the disease and may aid in disease progression.
Gait abnormalities are another risk factor. People with abnormal gaits are at an increased risk for inflammation.
Lastly, male gender is a risk factor. Osteomyelitis is more common in males compared to females, although the reason behind this is not clear. Males may have different physiological responses to diseases compared to women.
Complications may arise from having untreated osteomyelitis. Sepsis is a potentially deadly complication of osteomyelitis. Sepsis is a widespread, systemic infection that may occur after osteomyelitis. Sepsis starts with fever, chills, and irregular heartbeat. Septic emboli are another complication. If a person, for instance, has osteomyelitis on the femur, septic emboli can occur. These emboli can travel to other parts of the body, which can cause blockages in other parts of the body.
Amputations may also occur, particularly if the disease has advanced and the bone and leg or extremity can no longer be saved. These amputations are often of the lower leg, where infections are more common.
The diagnosis of osteomyelitis is based primarily on clinical findings. The patient’s initial history, physical findings, and laboratory results serve as benchmarks for improvement. Leukocytosis and increased erythrocyte sedimentation rate, as well as increases in C-reactive protein, may be noted. In up to one-half of children with osteomyelitis, blood cultures are positive.
The bones should also be palpated at the pedal ulcers that are infected. In patients with diabetes, this is strongly correlated with the presence of osteomyelitis. If bone is palpated, the physician may proceed directly to histologic and microbiologic confirmation. Treatment will come after.
In osteomyelitis of the extremities, x-rays may be taken and bone scintigraphy may also be done. These are the primary investigative tools. Radiographic evidence of osteomyelitis may not be evident for up to two weeks after the onset of infection. The radiographs may show that the patient has osteolysis, sequestra, and periosteal reactions. A bone abscess found during the chronic or sub-acute stage of osteomyelitis is termed as Brodie’s abscess.
Techetium Tc-99m methylene diphosphonate is used for nuclear imaging. It is the radiographic drug of choice. The specificity of bone scintigraphy will not be enough to support a diagnosis of osteomyelitis in many practical clinical scenarios.
After initial evaluation, establishment of microbial etiology, and staging, treatment includes antibiotic therapy, debridement, and stabilization of the bone if necessary. In most patients with osteomyelitis, the use of early antibiotic therapy produces the most optimal results. Antibiotics must be given for a minimum of four weeks to achieve an acceptable response. To reduce costs, parenteral antibiotics can be administered on an outpatient basis. Alternatively, the use of oral antibiotics can be considered.
Surgical debridement is not necessary if the diagnosis of osteomyelitis is made early on. Current treatment recommendations do not always require surgical debridement. However, this is an option if antibiotic therapy fails. Then, another course of 4-6 weeks of parental antibiotic therapy is essential. Empiric antibiotic therapy is generally not recommended for chronic osteomyelitis. Depending on the type of chronic osteomyelitis, patients may have to receive a course of antibiotics for 2-6 weeks.
The prevention of osteomyelitis begins with avoiding infections. Thus, wounds that are open and fresh should be cleaned thoroughly. Running them under tap water for a few minutes should help in avoiding infections. Afterwards, the wound should be covered with a clean cloth or sterile gauze. Checking wounds for any signs of infection may help the diagnostic process if osteomyelitis develops.
Improving one’s health is another way to prevent osteomyelitis. People who have a weakened immune system or poor circulation are at an increased risk for osteomyelitis. Taking steps to improve general health will greatly reduce the chances of osteomyelitis.
Cigarette smoking is a risk factor for osteomyelitis. Stopping smoking is one way to prevent osteomyelitis from occurring. If the patient has diabetes, adequate glycemic control is another way to prevent osteomyelitis. Preventing osteomyelitis is not easy, however, it can be done if the patient is well-informed.