It can be sub-classified based on the:
- organism that caused the infection
- the route of the infection
- duration
- anatomic location of the infection
In rare circumstances bone and joint infections can even be fatal, but luckily, an early diagnosis and proper treatment can help control or eliminate the infection.
Incidence
The incidence of osteomyelitis is 2 in 10,000 people. Neonatal prevalence is approximately 1 per 1,000. The annual incidence in sickle cell patients is approximately 0.36%. The prevalence of osteomyelitis after foot puncture may be as high as 16%. 30-40% of all patients are diabetics. Male-to-female ratio is approximately 2:1.
The route of infection
Several researches done in the past have proven that bacteria can infect the bones in a number of ways. The most common bacterium that causes osteomyelitis is Staphylococcus aureus.
- It can travel into the bone through the bloodstream from other infected areas in the body. This is called Hematogenous osteomyelitis. Studies are indicating that this the most common way people get bone infections.
- Direct infection is also common. It happens when bacteria enter the body's tissues through a wound and travel to the bone. This mostly happens following an injury or trauma. Open fractures are the injuries that most often cause osteomyelitis.
- When the blood supply to that area of the bone is disrupted, it can also result in bone infection. This can happen in older people with atherosclerosis and sometimes it is also associated with diabetes. Most infections of this kind occur in toes or feet.
Possible causes of osteomyelitis
Beside the Staphylococcus aureus, Escherichia coli and streptococci are other common pathogens. In some subpopulations, including intravenous drug users, Gram negative bacteria, including enteric bacilli, are also a significant pathogen. In osteomyelitis involving the vertebral bodies, 50 percent of the cases are due to Staphylococcus aureus, and the other 50 percent due to tuberculosis.
Tubercular osteomyelitis of the spine was very common before the initiation of effective anti-tubercular therapy.
The infection that causes osteomyelitis often has a root in another part of the body and spreads to the bone via blood. Affected bone may have been predisposed to infection because of some recent trauma.
When we talk about children’s osteomyelitis, usually the long bones are affected, while, in adults, it is the vertebrae and the pelvis. When the bone is infected, pus is produced within the bone, which may result in an abscess. The abscess then deprives the bone of its blood supply causing bone tissue to die and leading to chronic osteomyelitis which can persist intermittently for years.
Signs and symptoms of osteomyelitis
The signs and symptoms of osteomyelitis and septic arthritis vary depending on the location of the infection, the stage to which it has developed and the cause of the infection.
Hematogenous long-bone osteomyelitis
- Abrupt onset of high fever (fever is present in only 50% of neonates with osteomyelitis)
- Fatigue
- Irritability
- Malaise
- Restriction of movement
- Local edema, erythema and tenderness
Hematogenous vertebral osteomyelitis
- Insidious onset
- History of an acute bacterial episode
- May be associated with contiguous vascular insufficiency
- Local edema, erythema and tenderness
Chronic osteomyelitis
- Non-healing ulcer
- Sinus tract drainage
- Chronic fatigue
- Malaise
All this is usually accompanied with fever, edema, warmth, fluctuance, tenderness to palpation, reduction in the use of the extremity and sinus tract drainage. As for the histological changes, the basic processis the bone necrosis. The areas of necrotic bone are the basis for distinguishing between the acute osteomyelitis and chronic osteomyelitis. Osteomyelitis is an infective process which encompasses all of the bone components, including the bone marrow. When it is chronic it can lead to bone sclerosis and deformity.
Risk factors
Risk factors are:
- recent trauma
- diabetes
- hemodialysis
- intravenous drug abuse
- removed spleen
Diagnosis of osteomyelitis
Blood tests
An increased number of white blood cells in your blood may indicate an infection. Your doctor may also be able to identify the infecting microorganism in cultures of your blood.
X-ray
Bone scans and X-ray exams are the key to diagnosing osteomyelitis and may help the doctor identify the infected areas. For example, they may help detect fluid collections around a joint and abnormal bone surfaces. This method can be particularly useful in diagnosing septic arthritis, since they can better define soft tissue swelling and identify excess fluid in an infected joint.
Biopsy
The gold standard for diagnosing a bone or joint infection is biopsy. The doctor will usually administer a local anesthetic and remove tissue from a bone lesion or use a needle to withdraw fluids from an infected joint. Tests, including cultures performed on the samples, can confirm an infection and identify its cause.
MRI
The MRI is effective in the early detection and surgical localization of osteomyelitis. Studies have shown its superiority compared to plain radiography, CT, and radionuclide scanning in selected anatomic locations. Its sensitivity ranges from 90-100%.
CT scanning
CT scans can depict abnormal calcification, ossification, and intracortical abnormalities. It is probably most useful in the evaluation of spinal vertebral lesions. It may also be superior in areas with complex anatomy: pelvis, sternum, and calcaneus.
Ultrasonography
This simple and inexpensive technique has shown promise, particularly in children with acute osteomyelitis. Ultrasonography may demonstrate changes as early as 1-2 days after the onset of symptoms.
Abnormalities include:
- soft tissue abscess
- fluid collection
- periosteal elevation
Ultrasonography allows for ultrasound-guided aspiration. It does not allow for evaluation of bone cortex.
In order to set the accurate diagnosis 2 of the 4 following criteria are required:
- Purulent material on aspiration of affected bone
- Positive findings of bone tissue or blood culture
- Localized classic physical findings of bony tenderness, with overlying soft-tissue erythema or edema
- Positive radiological imaging study
Possible complications
Several problems could occur if osteomyelitis is left untreated. In most cases, it becomes a chronic infection or spreads to other areas of your body, eventually causing bone death. This process is called osteonecrosis. Reduced limb or joint function may follow, and in extreme cases an amputation may be required. It can even damage the spinal nerves and prove fatal. The most common complication of septic arthritis is osteoarthritis –an inflammation of bone and joint. Some patients may have a poor long-term response to joint infection treatment so it can sometimes lead to permanent movement limitation, difficulty walking or shortening of the afflicted limb.
Other possible complications include:
- Bone abscess
- Bacteremia
- Fracture
- Loosening of the prosthetic implant
- Overlying soft-tissue cellulitis
- Draining soft-tissue sinus tracts
Treatment of osteomyelitis
There are several treatment options for treating osteomyelitis and septic arthritis and the primary goal should be eliminating the infection and preventing it from developing into a chronic condition.
Antibiotics
If the infection is caused by the bacteria, it's often treated with antibiotics.
Patient can receive the drugs intravenously and the treatment could last from two to six weeks. In some cases, especially with children, oral antibiotics following an initial intravenous dose may be effective. The treatment you receive depends on the: type of bacteria, the location of the infection, the type of surgery that might be done, and other health conditions or issues you might have.
The most commonly used antibiotics are:
- Nafcillin (Nafcil, Unipen)
- Cefazolin (Ancef)
- Ciprofloxacin (Cipro)
- Ceftazidime (Fortaz, Ceptaz)
- Clindamycin (Cleocin)
- Vancomycin (Vancocin)
- Drainage
The doctor may drain soft tissue abscesses or pockets of fluid surrounding the infected bones or joints, if needed. In cases of septic arthritis, ther doctor may use a needle to drain the pus from the joint on a daily basis. He may also use an instrument called arthroscope to clean the joint. If the infection is serious and couldn’t be resolved by drainage, he may need to open the joint surgically to remove damaged tissue and infection.
Surgery
Surgery is usually necessary, especially if the infection is chronic or if a patient has some hardware implanted such as metal plates or artificial joints.
Prevention
The easiest way to prevent osteomyelitis is to practice good hygiene. This means that, if you get a cut or a wound, you make sure you clean it thoroughly. Wash it with simple toilet soap and water, holding it under running water for at least 5 minutes to flush it out.
To keep the wound clean afterward, you should cover it with sterile gauze or a clean cloth. You can apply an over-the-counter antibiotic cream, too, but the most important thing is to keep the injury clean.