Osteomyelitis (Bone Infection): Symptoms, Causes, and Treatment

Osteomyelitis (bone infection) is an acute or chronic inflammatory process involving the bone and its structures secondary to infection (with pyogenic organisms including bacteria(mostly Staphyloccocus), fungi, and mycobacteria).

Acute osteomyelitis is the clinical term for a new infection in bone that can develop into a chronic reaction when intervention is delayed or inadequate.

Before the introduction of penicillin in the 1940s, management of osteomyelitis was mainly surgically (eg extensive debridement, saucerization, wound packing).

Since the availability of antibiotics, mortality rates from osteomyelitis, including staphylococcal osteomyelitis, has improved significantly. Despite the advances in current health care, osteomyelitis is now a major clinical challenge, with recurrent and persistent infections occurring in approximately 40% of patients.

The pathophysiology of osteomyelitis is complex and poorly understood. There are several key factors contributing to the infection including: the virulence of the infectious organism, the individual’s immune status, any underlying disease, and the type, location, and vascularity of the involved bone.

Osteomyelitis (Bone Infection)

Characteristics/Clinical Presentation

Individuals presenting with osteomyelitis may have the following symptoms:

• Pain and/or tenderness in the infected area
• Inflammation, redness, and warmth in the infected area
• Fever, chills, and excessive sweating
• Nausea and generalized feeling of being ill
• Lower back pain
• Swelling of the legs, ankles, and feet
• Joint pain
• Antalgic gait
• “Sausage toes

The primary manifestations of osteomyelitis may vary between adults and children.

In children, osteomyelitis tends to be acute, and it usually appears within 2 weeks of a pre-existing blood infection. This is known as hematogenous osteomyelitis, and it is normally due to methicillin-resistant Staphylococcus aureus (S. aureus) (MRSA).

They have severe complaints, such as high fever and intense pain, but in some cases the predominating symptoms are edema, erythema, and tenderness in the infected area.

In adults, sub-acute or chronic osteomyelitis are more common, especially after an injury or trauma, such as a fractured bone. This is known as contiguous osteomyelitis. It usually affects adults over the age of 50 years

Etiology/Causes

The most common causative species are the usually commensal staphylococci, with Staphylococcus aureus and Staphylococcus epidermidis responsible for the majority of cases.

Staphylococcal infections are becoming an increasing global concern, partially due to the resistance mechanisms developed by staphylococci to evade the host immune system and antibiotic treatment. Other organisms that cause are Escherichia coli, Pseudomonas, Klebsiella, Salmonella.

Osteomyelitis can occur in a variety of bones in different areas of the body. The area affected often depends on the causative agent, the individuals’ age, and previous medical history as certain types of osteomyelitis can affect different populations.

The bones commonly involved in children are long bones (adjacent to growth plates) such as the femur, tibia, humerus, and radius due to the amount of bone marrow present in long bones. Osteomyelitis in adults usually affects the vertebral column, in particular the lumbar spine, the sacrum, and the pelvis.

Staphylococcus aureus is the usual causative agent of acute osteomyelitis. Once bound to cartilage, the organism produces a protective glycocalyx and stimulates the release of endotoxins.

Other organisms such as group B streptococcus, pneumococcus, Pseudomonas aeruginosa, Haemophilus influenza, and Escherichia coli are also capable of producing bone infection. In individuals diagnosed with sickle cell anemia, Salmonella infection can be associated with osteomyelitis.

Surgical procedures, open fractures, and implanted orthotic devices are also causative agents of acute osteomyelitis.

A form of osteomyelitis, exogenous osteomyelitis, occurs when bone extends out from the skin allowing a potentially infectious organism to enter from an abscess or burn, a puncture wound, or other trauma such as an open fracture.

These examples of osteomyelitis secondary to infection are common in immunocompromised individuals and in those diagnosed with diabetes mellitus or severe vascular insufficiency.

Hematogenous osteomyelitis is acquired from the spread of organisms from preexisting infections such that occurs in impetigo; furunculosis (persistent boils); infected lesions of varicella (chickenpox); and sinus, ear, dental, soft tissue, respiratory, and genitourinary infections. Genitourinary infections can lead to osteomyelitis of the sacrum or iliac.

Diagnostic Tests/Lab Tests/Lab Values

Medical diagnosis is often difficult because of the lack of specific signs and symptoms, especially in chronic osteomyelitis.

Signs and symptoms that are usually associated with infection may be mistaken for normal postoperative changes.

Radiographs

May not detect bony abnormality in infections less than 10 days in duration[3].

Lytic lesions may be demonstrable on radiographs within 2 weeks of onset of the infection.

Magnetic resonance imaging (MRI) and isotope bone scans are the procedures of choice to delineate the diseases anatomic extent.

Flourine-18-flourodeoxyglucose positron emission tomography (FDG-PET) scans provide accurate localization of infection and/or source of fever of undetermined origin, thereby guiding further testing.

Medical Management

Immediate treatment is indicated for osteomyelitis, especially in the acute phase. Treatment is usually initiated with an antibiotic, determined by the results of the bone biopsy or cultures taken, given intravenously at a high dose.

Factors such as the patients age, health status, location of infection, and prior antimicrobial therapy are taken into consideration when determining the antibiotic used for treatment[3]. The antibiotics are usually prescribed for 4-6 weeks followed by >8 weeks of oral therapy.

Osteomyelitis may also need to be treated surgically. Options include:

• Draining the infected area
• Removal of necrotic bone and soft tissue
• Restoring normal blood flow to the bone
• Removing any foreign objects
• Amputation of the infected limb

Physical Therapy Management

Physical therapists can play a vital role in the screening process for osteomyelitis. Individuals who present with signs and symptoms of infection, possibly causing osteomyelitis, should be referred to a physician for further diagnostic testing. These signs and symptoms are included in the above section.

Prevention is another area in cases of osteomyelitis where physical therapists can play an important role. Chronic osteomyelitis is often a result of complication of treatment with open fractures, therefore, prevention of infection is highly important.

Since the role of nutrition is vital in cases of infection, patient need to be properly educated on proper nutrition in early post-surgical intervention due to the fact that most infections occur in the immediate post-operative period.

Individuals who are at risk for developing osteomyelitis should also be taught proper preventative measures and be aware of early warning signs that infection may be present such as, excessive pus present coming from incision line, redness, extreme tenderness, increased skin temperature near area of injury or surgical procedure, and symptoms of nausea or vomiting.

If treated surgically for osteomyelitis, physical therapy may be indicated post-operatively to address any impairments in strength, ROM, proprioception, etc. as well as treatment for any functional limitations or disabilities secondary to the infection.

Differential Diagnosis

• Ewing Sarcoma
• Osteosarcoma
• Reactive bone marrow edema
• Traumatic or stress fractures
• Inflammatory arthritis
• Gout