Osteomyelitis: Causes, Diagnosis and Treatment

Normally, when bones are intact and healthy, they have the ability to resist infection. However, when bacteria enter through trauma, local blood supply deficiency, or wounds that allow bacterial contact with bone, it can cause osteomyelitis.

What is Osteomyelitis?

Osteomyelitis, also known as bone infection, is an acute or chronic inflammatory process related to the bone, usually secondary to infection by bacteria, fungi, and mycobacteria.

Osteomyelitis occurs more frequently in children than in adults and usually affects long bones. In adults, osteomyelitis affecting the vertebral bodies is the most common. Osteomyelitis involving the adjacent joints in young people usually occurs with trauma and related surgeries. In contrast, in older adults, infections are often associated with pressure sores and infected joints. Osteomyelitis associated with vascular insufficiency occurs frequently in patients with underlying diabetes.

Common causes of osteomyelitis

Normally, healthy and intact bones have the ability to resist infection. However, when bacteria penetrate through injury, local ischemia, or damaged tissue that allows bacteria to come into contact with the bone, osteomyelitis can occur.

Some bacteria such as Staphylococcus aureus attach to bone via receptors called adhesins. They bind to components of the bone structure including laminin, collagen, fibronectin, and bone sialoglycoprotein. S. aureus is able to bind to collagen, allowing it to attach to bone cartilage. It can also survive intracellularly after being phagocytosed by bone cells.

Some bacteria produce a protective biofilm around themselves and underlying surfaces. This characteristic is found in some bacteria that attach to bones and implants. Subsequently, they become antibiotic resistant and survive intracellularly causing bone infection and failure of short-term antibiotic treatment.

Individuals at higher risk for osteomyelitis include those with prolonged skin infections, immune suppression, poor blood circulation, prosthetic joints, intravenous drug use, and diabetes.

The progression of osteomyelitis

The process of bone inflammation in the body always involves two simultaneous processes: destruction and regeneration.

The process of bacterial bone destruction

First, bacteria arrive at the bone and destroy it, leading to the formation of pus which then spreads around. The spread can be:

• Into the bloodstream: causing sepsis.
• Into the joint: usually at the upper end of the thigh bone into the hip joint.
• Into the bone, causing inflammation and blocking the blood vessels that nourish the bone, forming pockets of inflammation that surround the bone, and the bone in that area will die due to lack of nourishment.
• Outside the soft tissue, causing infection and abscesses, which may rupture spontaneously or need to be incised, leaving a persistent, long-lasting hole.
• If the inflammation process is strong, which means the destruction caused by bacteria is massive, it can make the entire bone section inflamed and sometimes broken.

The process of bone regeneration after infection

The process of bone regeneration after infection, also known as the body’s defense mechanism, involves two simultaneous phenomena in the presence of bacteria in the bone.

Firstly, there is an increase in the formation of new blood vessels in the inflamed area to enhance the delivery of white blood cells, macrophages, antibiotics, etc. to eradicate the bacteria. The body establishes a barrier against inflammation.

Secondly, there is an increase in the development of a thick bone membrane in the inflamed area, known as the “bone membrane reaction,” which also aims to provide support. This thick bone membrane promotes the formation of new blood vessels and develops into new bone tissue, thereby resisting the destructive effects of bacteria.

The relationship between the processes of bone destruction and regeneration in osteomyelitis is as follows

If bone destruction is more severe than bone regeneration, it usually leads to acute osteomyelitis, where bone inflammation occurs quickly.

If bone destruction is weaker than bone regeneration, and appropriate treatment is given to enhance the body’s defense mechanism, it can eliminate all bacteria and cure the disease.

If the two processes are balanced, chronic osteomyelitis usually occurs, with intermittent acute exacerbations that require complex treatment.

Symptoms and diagnosis of osteomyelitis

To diagnose osteomyelitis, clinical symptoms and blood tests, X-rays, bone scans, CT scans, MRI, and bone biopsy are needed.

Hematogenous osteomyelitis

Patients with hematogenous osteomyelitis may have the following symptoms:

• High fever, chills, rapid pulse, and continuous high temperature. If bacteria enter the bloodstream, the body shows signs of sepsis.
• Pain: Often unclear pain, pain at the site, sometimes pain around the inflamed bone area, also known as the characteristic pain circle of osteomyelitis. Sometimes, osteomyelitis creates an abscess that spreads outside the surrounding soft tissue. The larger the abscess, the more the patient experiences pain.
• Reduced mobility: Due to pain or sometimes loss of mobility due to natural bone fractures, joints become inflamed.
• Usually only a slight swelling is seen at the painful area. Later, there may be a swollen, hot, red, and painful lump, similar to a muscle inflammation. The surrounding joint area may also become swollen and tender.
• Puncture: There may be pus, and culturing the bacteria shows that most of them are staphylococcus aureus.
• Blood tests: The neutrophil count, sedimentation rate, and CRP of patients with hematogenous osteomyelitis are all increased. If the procalcitonin is also elevated, it usually indicates sepsis and the cultured blood can identify the bacteria causing the disease.
• X-rays of hematogenous osteomyelitis have three stages: In the early stage, the bone appears to be sparse, and the bone membrane thickens. In the later stage, the bone membrane thickens noticeably, and there is an image of compression under the bone membrane. In the final stage, abscesses, dead bone fragments, or even dead bone fractures can be seen.

Adjacent osteomyelitis symptoms

• Adjacent osteomyelitis usually occurs after surgery, open fractures, etc.
• From the 4th or 5th day after surgery, the patient continues to have high fever and chills.
• Pain at the fracture site or wound gradually increases.
• Swelling, redness, and tenderness spread around the wound or surgical site.
• Purulent discharge flows through the wound or surgical site and continues.

X-rays show that the bone is sparse and slow to heal. The patient needs to distinguish between bone membrane reactions in inflammation and nonunion phenomena of the bone.

Symptoms of chronic osteomyelitis

Chronic osteomyelitis often occurs after acute osteomyelitis is not adequately treated.

The disease recurs in episodes characterized by the formation of abscesses and dead bone. Abscesses usually occur in low areas, one or two abscesses, with a small size of about 0.5 cm.

Treatment is difficult, complex, and prone to recurrence. Antibiotics are not effective.

Patients are anemic and weak. They may experience fever during acute exacerbations.

Motor function is usually minimally affected. There may be pain during acute episodes or limited movement of the affected joint.

The affected limb is swollen, larger, with inflamed gray skin, and feels firm to the touch.

The discharge from acute abscesses is thick and foul-smelling, while chronic discharge is thin, yellow, and very odorous.

Old abscesses may appear closed on the bone.

The bacteria that cause chronic osteomyelitis are often Staphylococcus aureus.

X-rays typically show the characteristic features of pus formation, dead bone, and periosteal reaction, or only pus formation without dead bone.

Complications of osteomyelitis

The most common complication in children with osteomyelitis is recurrent bone infection. Some complications may arise from untreated or inadequately treated osteomyelitis, such as:

Infected joint inflammation, bone deformities, compression, pathological fractures. Squamous cell carcinoma, systemic infections, contiguous soft tissue infections. Rare amyloidosis.

How to treat osteomyelitis?

The principle of treating osteomyelitis is early diagnosis, intravenous antibiotic therapy, drainage of pus, and debridement of necrotic tissue.

The treatment for osteomyelitis depends on the severity of the condition, with surgery being indicated if the patient does not respond to specific antibiotic therapy, or in cases of prolonged soft tissue compression or collection under the hard membrane, or if there is a suspicion of concomitant joint infection.

Internal treatment for osteomyelitis

Conservative internal treatment is required for all cases of acute hematogenous osteomyelitis. For chronic relapsing osteomyelitis, internal treatment is only used to support and combine with postoperative care.

Antibiotics should be used in the early stages of osteomyelitis according to the following principles:

• First, the patient should be blood cultured, joint fluid cultured, and the joint fluid or pus sample should be rapidly tested and gram-stained to identify the bacteria.
• Based on the results of the gram-stain and other risk factors, appropriate antibiotics should be administered immediately.
• Antibiotics used for osteomyelitis in this stage should be high-dose, intravenous, and administered continuously for 3 to 4 weeks.
• At this point, the patient with osteomyelitis is treated with combination antibiotics, typically using the anti-staphylococcal group (Oxacillin, Vancomycin). If there is a suspicion of Gram-negative bacterial infection, Cephalosporin III generation should be used in combination with either a Fluoroquinolone or Aminoglycoside group.
• In the later stage of osteomyelitis, treatment should be tailored according to the clinical response and results of antibiotic therapy.

Additionally, painkillers, anti-swelling, and fever-reducing medications may be necessary in the treatment of osteomyelitis, along with addressing any underlying lifestyle changes.

To prevent pathological fractures and improve body support, patients should be immobilized. Plaster casts are widely recommended for all cases of acute hematogenous osteomyelitis. The cast can be closed or open, depending on the case. If there is a pathological fracture, the cast should be applied for the same duration as that of the fracture treatment.

Another important aspect is ensuring adequate nutritional intake and vitamin supplements. Blood transfusions or protein-rich fluids may also be necessary.

Surgical treatment of osteomyelitis

Acute hematogenous osteomyelitis requires surgical treatment when the inflammation is tense and may lead to bone fracture.

Wide incision and drainage of pus, removal of necrotic tissue. Local antibiotic irrigation. Establishment of a daily irrigation system with antibiotic solution.

The treatment for chronic osteomyelitis adjacent to bone fusion is as follows:

• Maintaining bone continuity is a priority according to anatomy. After the bone is fused, surgical removal of the inflammation is performed.
• For osteomyelitis of the pseudo-articulation or bone loss, after removal of the inflammation, bone grafting is performed.
• If the exposed bone is long, the surrounding skin and muscle flap must be cut to cover the fracture site.

Surgical treatment for chronic osteomyelitis:

• All cases of chronic osteomyelitis with pus discharge and dead bone require surgical treatment.
• Clean the surgical area by continuous irrigation with antibiotic solution or hydrogen peroxide.
• Excise the necrotic tissue, remove the pus and clean the pus discharge opening.
• Proceed to drill the bone until reaching the healthy bone (where the bone is bleeding). Clean the pus discharge area thoroughly by continuous irrigation and remove all dead bone, without leaving any behind. Unblock the medullary canal.
• Filling the bone defect is necessary and mandatory in the surgical treatment of osteomyelitis.

Hopefully, this article has helped answer the question of how to treat osteomyelitis. Is osteomyelitis dangerous?