Epidemiology
In developed countries, the reported incidence of peripheral bone infection is about 2% per year.[1] Surgical care of open or closed fractures may increase this incidence.[1]
A study in the US showed that the overall age- and sex-adjusted annual incidence of osteomyelitis was 21.8 cases per 100,000 person-years between 1969 and 2009. The annual incidence was higher for men than for women and increased with age.[6] During the study period, incidence rates remained stable among children and younger adults (<50 years) but almost tripled among older adults, mostly driven by an increase in diabetes-related cases. The incidence of diabetes-related osteomyelitis quadrupled over the three decades of investigations.[6]
Risk factors
Patients may present with an acute exacerbation of a chronic osteomyelitis. Relapse of infection may occur in the same site (bone) weeks to years after apparently successful treatment of the initial infection, particularly in older patients.[4]
Bacteria can enter through an open fracture site or a wound that penetrates down to bone (e.g., stab wound).[23] The risk depends on the the severity of injury (higher risk of surgical infections with open proximal femoral and tibial fractures and proximal humeral fractures), the degree of bacterial contamination, the timing and adequacy of surgical debridement, and the timing and administration of antibiotics.[24] Soft-tissue stripping may leave devitalised bone and soft tissues that may become infected. Fracture fixation can also become infected.[25] Delays to initial debridement (or inadequate debridement), not being given appropriate antibiotic prophylaxis, or delays in definitive soft-tissue cover are risk factors for subsequent infection.[25] In patients with open extremity fractures, a delay to debridement increases the rate of deep infection in patients with higher-grade injuries.[26][27]
Because of the high likelihood of bacteraemia during non-sterile self-injection techniques, bone infections can occur in intravenous drug misusers. The commonest pathogen is Staphylococcus aureus but pathogens such as Pseudomonas aeruginosa are also implicated (classically in the spine and sacroiliac joints).[8] Injecting drug users are susceptible to skeletal infections in uncommon places such as the sternoclavicular and sacroiliac joints or the pubic symphysis.[28][29] Infections of the sternoclavicular and sacroiliac joints may result, in part, from injecting in high-risk areas such as the jugular vein (termed a ‘pocket shot’) and femoral vein (known as a ‘groin hit’).[28] Such musculoskeletal infections are also more likely to be polymicrobial or anaerobic, especially if the injecting drug user contaminates the injection site, equipment, or drugs with saliva.[28]
Foot infections occur frequently in patients with diabetes. Acute infections usually follow minor trauma and dramatically increase the risk of amputation. Chronic infection may be associated with ulceration as a result of changes in foot biomechanics and peripheral neuropathy.[30] See Diabetes-related foot disease.
With a weakening immune system, the risk of osteomyelitis increases.[1]
Surgical site infections are common following surgery for injuries such as open fractures, bullet wounds, knife wounds, and lacerations.[31]
Contamination of local bones in the operative field during surgery can lead to osteomyelitis, or prosthetic implant infections (which can be non orthopaedic).
For example, sternal osteomyelitis is a complication of acute mediastinitis associated with coronary artery bypass surgery and harvesting of the internal mammary artery, which can lead to sternal ischaemia.[32]
Haematogenous osteomyelitis is seen in patients with distant foci of infection, such as those with infected urinary catheters.
Periodontal abscess can result in osteomyelitis of the mandible, which is more susceptible to osteomyelitis than the maxilla because the cortical plates of the mandible are thin and its medullary tissues have relatively poor vascular supply.[33]
Bone and joint infections are common complications of sickle cell disease, occurring in more than 10% of patients.[34][35][36] Long bones are the most common sites of infection, predominantly in paediatric patients and young adults.[37] Sickle cell anaemia is often associated with adult haematogenous osteomyelitis. Osteomyelitis may mimic a sickle cell crisis in these patients; therefore, culture results are important to establish the diagnosis and to determine the pathogen (which is often atypical).[37] The most commonly isolated pathogens are Salmonella and Staphylococcus aureus.[34]
As an autoimmune disease, rheumatoid arthritis increases the risk of osteomyelitis.[1]
As a chronic condition, chronic kidney disease increases the risk of osteomyelitis.
Risk of osteomyelitis increases in patients who are immunocompromised due to HIV or autoimmune diseases, chemotherapy, or immunosuppressive treatment, and in those who misuse drugs or alcohol.[1]
May predispose to Kingella kingae infection.[9]
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