Infective arthritis Flashcards

Question

Which organisms cause OM

Answer 1

Staphylococcus aureus, coagulase-negative staphylococci, aerobic gram-negative bacilli (30%) M. tuberculosis Neisseria gonorrhoeae Streptococci (skin, oral) Enterococci (bladder, bowel) Anaerobes (bowel) Salmonella in sickle cell anaemia patients

Answer 2

1.inflammatory exudate in the marrow 2. increased intramedullary pressure 3.extension of exudate into the bone cortex 4.rupture through the periosteum 5.Interruption of periosteal blood supply causing necrosis 6. Leaves pieces of separated dead bone 7. New bone forms here

Answer 3

Inflammatory cells Oedema Vascular congestion Small vessel thrombosis

Answer 4

neutrophil exudates lymphocytes & histiocytes Necrotic bone ‘sequestra’ new bone formation ‘involucrum’

Answer 5

History Examination CRP - raised inflammatory marker FBC- WCC - high in acute, normal in chronic U and E LFTs HbA1C MRI - Gold standard CR Plain Xray Nuclear bone scan

Answer 6

Onset - several days. dull pain at site of OM may be aggravated by movement. - **Fever** - **Pain** - **Overlying redness** - **Swelling** - **Malaise**

Answer 7

Systemic: Fever, rigors, sweats, malaise Local: Acute OM tenderness, warmth, erythema, and swelling Chronic OM tenderness, warmth, erythema, and swelling PLUS any of draining sinus tract deep / large ulcers that fail to heal despite several weeks treatment* non-healing fractures

Answer 8

pain but few other signs or symptoms.

Answer 9

Posterior extension - epidural and subdural abscesses or even meningitis. Extension anteriorly or laterally can lead to paravertebral, retropharyngeal, mediastinal, subphrenic, retroperitoneal, or psoas abscesses.

Answer 10

when infection breaks through cortex resulting in discharge of pus into the joint (knee, hip, and shoulder). More common in infants due to patent transphyseal blood vessels and immature growth plate

Answer 11

cortical erosion, periosteal reaction, mixed lucency, Sclerosis sequestra soft tissue swelling

Answer 12

Poor sensitivity and specificity,

Answer 13

marrow oedema from 3-5 days Delineates cortical, bone marrow and soft tissue inflammation

Answer 14

Microbiology and histology: Bone biopsy Positive Blood cultures

Answer 15

obtained via sterile technique, Open bx >>> needle bx 2 specimens Culture 16sRNA PCR may be necessary Histology showing inflammation and osteonecrosis

Answer 16

may obviate the need for invasive diagnostic testing if the organism isolated from blood is a pathogen likely to cause osteomyelitis. +ve in 50% of Acute OM most useful if hematogenous OM

Answer 17

Soft tissue infection (Cellulitis and erysipelas) Charcot joint Avascular necrosis of bone Causes: steroid, radiation, or bisphosphonate use. Gout uric acid crystals in joint fluid / more acute presentation Fracture Bursitis Malignancy

Answer 18

Debridement (remember Bromfield “we cannot be too early in letting it out”) Hardware placement or removal

Answer 19

Initial broad spectrum empirical therapy “start SMART” S. aureus or MRSA? gram-negative organisms? Special population: IVDU/HbSS? Tailored to culture and sensitivity findings “then FOCUS”. Bone penetration of drug Prolonged duration

Answer 20

Levofloxacin Ciprofloxacin Moxifloxacin Vancomyocin

Answer 21

Knowing when to stop treatment is very difficult 6 weeks of IV considered minimum switch to oral alternatives may work in some situations Stopping treatment guided by CRP response failure to respond requires re-imaging

Answer 22

May be slower onset Systemic symptoms Epidemiology is different from pyogenic OM Blood Culture less useful Biopsy essential Longer treatment 6 months Caseating Granolumata on histology

Answer 23

- Once the bacteria reach the bone they start to proliferate. This alerts nearby immune cells - specifically dendritic cells and macrophages - that try to fight off the infection. This represents the **acute phase** of the disease and occurs over a course of weeks. The immune cells release chemicals and enzymes that break down bone and cause local destruction. Usually acute osteomyelitis comes to a resolution - the immune system destroys all of the invading bacteria. - If the lesion is not that extensive, and there’s viable bone the osteoblasts and the osteoclasts begin to repair the damage over a period of weeks

Answer 24

- affected bone sometimes becomes necrotic and separates from the healthy part of the bone - and that’s called a **sequestrum.** At the same time, the osteoblasts that originate from the periosteum may form new bone that wraps the sequestrum in place, this is called an **involucrum.** - **Cloaca** may also form

Answer 25

defined as the infection of 1 or more joints caused by pathogenic inoculation of microbes. It occurs either by direct inoculation or via haematogenous spread. It is a medical emergency!

Answer 26

- Septic arthritis is a rare but potentially devastating condition, affecting 5 per 100,000 people each year in the developed world - Increases with age - 45% over 65 yrs

Answer 27

- **Staphylococcus aureus** - the most common cause in all age groups - **Staphylococcus epidermidis** - prosthetic joints - **Streptococcus pyogenes** - children under 5 years old - **Neisseria gonorrhoeae** - young, sexually-active adults - **Pseudomonas aeruginosa** - immunosuppressed, eldery and IV drug abuse - **Escherichia coli** - immunosuppressed, eldery and IV drug abuse

Answer 28

- **Underlying joint disease:** 10-fold increased risk; conditions such as rheumatoid arthritis, osteoarthritis and gout - **Intravenous drug use:** transfer of pathogenic organisms into the bloodstream - **Immunocompromised:** elderly, diabetes, HIV - **Prosthetic joint** - **Recent joint surgery**

Answer 29

due to the risk of permanent joint destruction, osteomyelitis and sepsis. It is most commonly caused by a bacterial infection, with the microbes either invading the joint directly or via the bloodstream from other sites of infection.

Answer 30

90% of cases are caused by staphylococci or streptococci, often as a complication of other pathologies such as cellulitis, chronic osteomyelitis, or drug abuse. Fungal and viral causes are rare.

Answer 31

Septic arthitis mainly affects one joint and so should be suspected in all monoarthritic cases. The knee is most commonly affected, but hip, shoulder, wrist and elbow joints are also affected.

Answer 32

- Hot, tender, erythematous, swollen joint - In the elderly and immunosuppressed and in RA the articular signs may be muted - Very limited range of movement

Answer 33

- Difficulty weight bearing - Fever

Answer 34

- **FBC**: leukocytosis - **CRP and ESR**: elevated due to inflammation and used for monitoring response to treatment - **Blood cultures**: should be performed on **all** patients before commencing antibiotics - **Joint aspiration (arthrocentesis):** definitive investigation Plain Xray US or MRI

Answer 35

Joint aspiration - MSC

Answer 36

Kocher criteria has been used in the diagnosis of septic arthritis. A score of 2 suggests a 40% probability and a score of 3 suggests a 93% probability. Non weight bearing 1 Temp > 38.5 1 ESR > 40mm/hr 1 WCC >12x10(9)/L 1

Answer 37

Crystal arthropathies - gout and pseudogout

Answer 38

IV antibiotics for 2 weeks followed by oral antibiotics for 4 weeks. Broad spectrum antibiotics should be given urgently and then tailored once the causative agent has been identified. - **Empirical therapy**: flucloxacillin is first-line - **Penicillin allergy**: clindamycin - **Suspected or confirmed MRSA**: vancomycin - **Gonococcal arthritis or gram-negative infection**: cefotaxime or ceftriaxone - **Joint drainage** - Aspiration - Arthroscopic drainage - Open drainage

Answer 39

After resolution of the acute illness, the patient should be followed up on at least one occasion to confirm complete recovery and to check for the presence of joint damage.

Answer 40

- **Osteomyelitis**: the spread of infection from the joint to the surrounding bone - **Permanent joint destruction** - **Sepsis**

Infective arthritis Flashcards

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