MSCT Week 3: Osteomyelitis Flashcards
Osteomyelitis description
Inflammation of bone that is almost always due to an infection, typically bacterial (pyogenic osteomyelitis) and may be acute or chronic
Pyogenic Osteomyelitis AKA
Bacterial osteomyelitis
Signs and symptoms of osteomyelitis
- Fever
- pain in the area of infection
- warmth and redness over the area of infection
Osteomyelitis risk factors
- Any age
- 2-12 is most common
- more common in males
Pathogenesis of Osteomyelitis
usually results from haematogenous spread in which bloodborne organisms, usually bacteria, are deposited in the medullary cavity and form a nidus infection
Osteomyelitis: Region in long bones most predisposed to infection
metaphysis because it has a large supply of slow-flowing blood which is an ideal environment for bacteria to accumulate and proliferate
Osteomyelitis from contiguous spread
infections originating from soft tissues and joints can spread to bone which often occurs in the context of vascular insufficiency such as patients with diabetes mellitus or peripheral vascular disease
A contiguous spread of osteomyelitis is from?
Soft Tissues to bone usually in vascularly impaired patients DM, Vasculitis
Haematogenous spread is from
Blood to bone
The contiguous spread is most common in people with
3 listed
- vascular deficiencies such as DM or peripheral vascular disease
- there is a diminished immune response secondary to poor perfusion of the infected region
- in these patients, the lower extremities are most commonly affected as there is associated peripheral neuropathy which predisposes to repeated microtrauma.
Osteomyelitis: Direct Inoculation
Direct seeding of bacteria into bone can occur as a result of open fractures, insertion of metallic implants or joint prostheses, human or animal bites and puncture wounds
Osteomyelitis most common infectious agent
Staphylococcus aureus
Staphylococcus aureus accounts for how much of Osteomyelitis?
80-90% of infections
Pathogen common in IVDU and Genitourinary tract infections
Escherichia Coli or Pseudomonas spp.
Osteomyelitis: Infectious agents common in Sickle Cell Disease
Salmonella
Osteomyelitis: Infectious agents common in Neonates
- Haemophilus influenzae
- Group B streptococci
Mycobacterial Osteomyelitis
typically affects 1-3% of individuals with pulmonary or extrapulmonary tuberculosis
COMMON SITE OF INFECTION IS SPINE 40% OF ALL CASES
Osteomyelitis: Acuity
Osteomyelitis may be acute or chronic
Acute Osteomyelitis: hematogenous spread or direct inoculation
- bacterial proliferation within the bone induces an acute suppurative response
- there is an accumulation of pus within the medullary cavity leading to raised intramedullary pressure and vascular congestion which can disrupt intraosseous blood supply
- the rise in intramedullary pressure can lead to rupture of the bony cortex, producing a cortical defect known as a cloaca
- Intramedullary pus can spread outward through the cloaca and form a subperiosteal abscess
- This causes elevation of the periosteum and disrupts the periosteal blood supply to the bone
- Continual accumulation of pus in the subperiosteal space leads to rupture of the periosteum and spread of infection to soft tissues through a channel between the bone and skin surface known as a sinus tract
Chronic Osteomyelitis
- If Acute Osteomyelitis is inadequately treated, there will be a progression of the disease to chronic osteomyelitis
- The pathological features of chronic osteomyelitis are a result of osteonecrosis caused by a disruption of the intraosseous and periosteal blood supply during the acute stage of disease
- a fragment of dead infected bone becomes separated from the viable bone and is known as a sequestrum
- The bacteria within the revascularized sequestrum are protected from antibiotics and the endogenous immune response thus forming a nidus for chronic infection which may persist for many years
- in an attempt to wall of the sequestrum, an inflammatory reaction characterized by osteoclastic resorption and periosteal new bone formation occurs
- The sequestrum becomes surrounded by pus, granulation tissue and a reactive shell of new bone known as involucrum
- The involucrum may have cloaca through which the pus can be discharged
Identify
Identify
Osteomyelitis Diagnosis
7 Listed
- Radiographic evaluation
- Blood Tests
- WBCs are usually normal even in acute osteomyelitis
- ESR and CRP are often elevated (but lack specificity without radiographs and microbiological data)
- CRP may be more reliable than ESR for assessing response to treatment in children
- Blood cultures should always be obtained when osteomyelitis is suspected though they are often negative except in cases of hematogenous osteomyelitis
- GOLD STANDARD FOR DIAGNOSIS OF OSTEOMYELITIS IS NEEDLE BONE BIOPSY WITH HISTOPATHOLOGIC EXAMINATION AND MICROBIAL CULTURES
Treatment of Osteomyelitis
3 listed
- Typically intravenous antibiotics, usually for extended periods
- if a sequestrum and involucrum is present then drainage and / or surgical debridement is often necessary
- Although uncommon with use of antibiotic regimens, amputation may be necessary with failure of medical therapy or when the infection becomes life threatening
