Osteomyelitis

Osteomyelitis
Classification and external resources
Osteomyelitis of the tibia of a young child. Numerous abscesses in the bone show as radiolucency.
ICD-10	M86
ICD-9	730
DiseasesDB	9367
MedlinePlus	000437
eMedicine	ped/1677
MeSH	D010019

Osteomyelitis (sometimes abbreviated to OM, and derived from Greek words osteon, meaning bone, myelo- meaning marrow, and -itis meaning inflammation) is infection and inflammation of the bone or bone marrow.^[1] It can be usefully subclassified on the basis of the causative organism (pyogenic bacteria or mycobacteria), the route, duration and anatomic location of the infection.

Classification

The definition of OM is broad, and encompasses a wide variety of conditions. Traditionally, the length of time the infection has been present and whether there is suppuration (pus formation) or sclerosis (increased density of bone) is used to arbitrarily classify OM. Chronic OM is often defined as OM that has been present for more than one month. In reality, there are no distinct subtypes, instead there is a spectrum of pathologic features that reflect balance between the type and severity of the cause of the inflammation, the immune system and local and systemic predisposing factors.

• Suppurative osteomyelitis
  • Acute suppurative osteomyelitis
  • Chronic suppurative osteomyelitis
    • Primary (no preceding phase)
    • Secondary (follows an acute phase)
• Non-suppurative osteomyelitis
  • Diffuse sclerosing
  • Focal sclerosing (condensing osteitis)
  • Proliferative periostitis (periostitis ossificans, Garré's sclerosing osteomyelitis)
  • Osteoradionecrosis

OM can also be typed according to the area of the skeleton in which it is present. For example, osteomyelitis of the jaws is different in several respects from osteomyelitis present in a long bone. Vertebral osteomyelitis is another possible presentation.

Pathogenesis

In general, microorganisms may infect bone through one or more of three basic methods: via the bloodstream, contiguously from local areas of infection (as in cellulitis), or penetrating trauma, including iatrogenic causes such as joint replacements or internal fixation of fractures or root-filled teeth.^[1] Once the bone is infected, leukocytes enter the infected area, and, in their attempt to engulf the infectious organisms, release enzymes that lyse the bone. Pus spreads into the bone's blood vessels, impairing their flow, and areas of devitalized infected bone, known as sequestra, form the basis of a chronic infection.^[1] Often, the body will try to create new bone around the area of necrosis. The resulting new bone is often called an involucrum.^[1] On histologic examination, these areas of necrotic bone are the basis for distinguishing between acute osteomyelitis and chronic osteomyelitis. Osteomyelitis is an infective process that encompasses all of the bone (osseous) components, including the bone marrow. When it is chronic, it can lead to bone sclerosis and deformity.

Chronic osteomyelitis may be due to the presence of intracellular bacteria (inside bone cells).^[2] Also, once intracellular, the bacteria are able to escape and invade other bone cells.^[3] At this point, the bacteria may be resistant to some antibiotics.^[4] These combined facts may explain the chronicity and difficult eradication of this disease, resulting in significant costs and disability, potentially leading to amputation. Intracellular existence of bacteria in osteomyelitis is likely an unrecognized contributing factor to its chronic form.

In infants, the infection can spread to a joint and cause arthritis. In children, large subperiosteal abscesses can form because the periosteum is loosely attached to the surface of the bone.^[1]

Because of the particulars of their blood supply, the tibia, femur, humerus, vertebra, the maxilla, and the mandibular bodies are especially susceptible to osteomyelitis.^[5] Abscesses of any bone, however, may be precipitated by trauma to the affected area. Many infections are caused by Staphylococcus aureus, a member of the normal flora found on the skin and mucous membranes. In patients with sickle cell disease, the most common causative agent is Salmonella, with a relative incidence more than twice that of S. Aureus.^[6]

Cause

In children, the long bones are usually affected. In adults, the vertebrae and the pelvis are most commonly affected.

Acute osteomyelitis almost invariably occurs in children. When adults are affected, it may be because of compromised host resistance due to debilitation, intravenous drug abuse, infectious root-canaled teeth, or other disease or drugs (e.g., immunosuppressive therapy).

Osteomyelitis is a secondary complication in 1–3% of patients with pulmonary tuberculosis.^[1] In this case, the bacteria, in general, spread to the bone through the circulatory system, first infecting the synovium (due to its higher oxygen concentration) before spreading to the adjacent bone.^[1] In tubercular osteomyelitis, the long bones and vertebrae are the ones that tend to be affected.^[1]

Staphylococcus aureus is the organism most commonly isolated from all forms of osteomyelitis.^[1]

Bloodstream-sourced osteomyelitis is seen most frequently in children, and nearly 90% of cases are caused by Staphylococcus aureus. In infants, S. aureus, Group B streptococci (most common^[7]) and Escherichia coli are commonly isolated; in children from one to 16 years of age, S. aureus, Streptococcus pyogenes, and Haemophilus influenzae are common. In some subpopulations, including intravenous drug users and splenectomized patients, Gram-negative bacteria, including enteric bacteria, are significant pathogens.^[8]

The most common form of the disease in adults is caused by injury exposing the bone to local infection. Staphylococcus aureus is the most common organism seen in osteomyelitis, seeded from areas of contiguous infection. But anaerobes and Gram-negative organisms, including Pseudomonas aeruginosa, E. coli, and Serratia marcescens, are also common. Mixed infections are the rule rather than the exception.^[8]

Systemic mycotic (fungal) infections may also cause osteomyelitis. The two most common are Blastomyces dermatitidis and Coccidioides immitis.

In osteomyelitis involving the vertebral bodies, about half the cases are due to S. aureus, and the other half are due to tuberculosis (spread hematogenously from the lungs). Tubercular osteomyelitis of the spine was so common before the initiation of effective antitubercular therapy, it acquired a special name, Pott's disease.

The Burkholderia cepacia complex has been implicated in vertebral osteomyelitis in intravenous drug users.^[9]

Diagnosis

Mycobacterium doricum osteomyelitis and soft tissue infection. Computed tomography scan of the right lower extremity of a 21-year-old patient, showing abscess formation adjacent to nonunion of a right femur fracture.

Diagnosis of osteomyelitis is often based on radiologic results showing a lytic center with a ring of sclerosis.^[1] Culture of material taken from a bone biopsy is needed to identify the specific pathogen; alternative sampling methods such as needle puncture or surface swabs are easier to perform, but do not produce reliable results.^[10]

Factors that may commonly complicate osteomyelitis are fractures of the bone, amyloidosis, endocarditis, or sepsis.^[1]

Treatment

Osteomyelitis often requires prolonged antibiotic therapy, with a course lasting a matter of weeks or months. A PICC line or central venous catheter is often placed for this purpose. Osteomyelitis also may require surgical debridement. Severe cases may lead to the loss of a limb. Initial first-line antibiotic choice is determined by the patient's history and regional differences in common infective organisms. A treatment lasting 42 days is practiced in a number of facilities.^[11] Local and sustained availability of drugs have proven to be more effective in achieving prophylactic and therapeutic outcomes.^[12]

In 1875, American artist Thomas Eakins depicted a surgical procedure for osteomyelitis at Jefferson Medical College, in a famous oil painting titled The Gross Clinic.

Prior to the widespread availability and use of antibiotics, blow fly larvae were sometimes deliberately introduced to the wounds to feed on the infected material, effectively scouring them clean.^[13][14]

Hyperbaric oxygen therapy has been shown to be a useful adjunct to the treatment of refractory osteomyelitis.^[15][16]

Open surgery is needed for chronic osteomyelitis, whereby the involucrum is opened and the sequestrum is removed or sometimes saucerization^[17] can be done

Fossil record

Evidence for osteomyelitis found in the fossil record is studied by paleopathologists, specialists in ancient disease and injury. It has been reported in fossils of the large carnivorous dinosaur Allosaurus fragilis.^[18]

See also

Media related to Osteomyelitis at Wikimedia Commons

• Brodie abscess
• Chronic recurrent multifocal osteomyelitis
• SAPHO syndrome
• Garre's sclerosing osteomyelitis
• Mickey Mantle, who contracted osteomyelitis in his youth from a football injury and whose condition shortened his baseball career

References

Further reading

• Mechanisms of Staphylococcus aureus invasion of cultured osteoblasts. Ellington JK, Reilly SS, Ramp WK, Smeltzer MS, Kellam JF, Hudson MC. Microb Pathog. 1999 Jun;26(6):317–23.
• Intracellular Staphylococcus aureus. A mechanism for the indolence of osteomyelitis. Ellington JK, Harris M, Webb L, Smith B, Smith T, Tan K, Hudson M. J Bone Joint Surg Br. 2003 Aug;85(6):918–21.
• Intracellular Staphylococcus aureus and antibiotic resistance: implications for treatment of staphylococcal osteomyelitis. Ellington JK, Harris M, Hudson MC, Vishin S, Webb LX, Sherertz R. J Orthop Res. 2006 Jan;24(1):87–93.

External links

• 00298 at CHORUS
• Acosta, Chin; et al. (2004). "Diagnosis and management of adult pyogenic osteomyelitis of the cervical spine" (PDF). Neurosurg Focus 17 (6): E2. doi:10.3171/foc.2004.17.6.2. PMID 15636572.  Cite uses deprecated parameters (help)