Bone and Joint Infection

Question 1

Define osteomytelitis

Answer 1

Infection of the bone

Question 2

Define septic arthritis

Answer 2

Infection of a joint

Question 3

Name microbes that can be responsible for osteomytelitis and/or septic arthritis

Answer 3

Staphylococcus Aureus (incl MRSA)
Streptococci
Enteric bacteria (e.g. salmonella, E.Coli)

Question 4

What microbe can cause infection on prosthetic joints?

Answer 4

Coagulase negative staphylococci

Question 5

What are the risk factors for osteomyelitis or septic arthritis?

Answer 5

Direct inoculation (trauma, medical procedures, skin ulcers)
Contiguous spread (nearby skin/soft tissue infections)
Haematogenous dissemination (IV devices, IV drug use)
Immunosuppression (drugs, conditions- mainly diabetes mellitus, renal failure, sickle cell disease)

Question 6

What factors must microbes have to enable infection of bone/joints?

Answer 6

Access
Adherence
Invasion
Multiplication
Evasion
Resistance
Damage
Transmission

Question 7

Describe the pathological process of osteomyelitis

Answer 7

Initial infection localised to cortical region as a small abscess
Infection progresses into subperiosteal space with lifting of the periosteum
Diffuse infection with sequestrium and sinus tract

Question 8

Define sequestrium

Answer 8

Avascular, necrotic region of infected tissue

Question 9

Define sinus tract

Answer 9

Route for pus to escape from an infection in bone

Question 10

Define involucrum

Answer 10

New bone formation outside the sequestrium

Question 11

Define cloacae

Answer 11

Pus from sequestrum escapes through holes in the involucrum

Question 12

What may a patient with osteomytelitis present with?

Answer 12

Pain, swelling, erythema, warmth, loss of function, fever, pathological fractures, discharging sinuses

Question 13

What may a patient with septic arthritis present with?

Answer 13

Pain, swelling, erythema, fever, loss of function, damage to articular surfaces

Question 14

How may imaging be used to investigate septic arthritis or osteomyelitis?

Answer 14

X-ray: useful in later stages but do not show early signs well.
CT: shows bone changes well, not so useful for soft tissue changes.
MRI: shows soft tissue changes well, not so useful for bone changes

Question 15

What may synovial fluid aspirated from a joint capsule look like if it is infected?

Answer 15

Thinner than usual, cloudy or contain pus if severe infection.
Blood indicates trauma, not infection

Question 16

What bloods should be taken for suspected osteomyelitis or septic arthritis? Any other investigations?

Answer 16

FBC, CRP, blood cultures
Skin/wound swabs (inc MRSA)
Imaging
Joint aspiration/ bone biopsy

Question 17

How should septic arthritis or ostemyelitis be managed?

Answer 17

Management of sepsis (sepsis 6)
Samples/cultures
Empirical Abx if necessary (2-6 weeks IV then 4-6 weeks PO)
Targeted Abx dependent on culture and sensitivities (2-6 weeks IV then 4-6 weeks PO)
Septic arthritis requires surgical washout
Osteomyelitis only requires surgery if chronic changes have occurred.
Prosthetic joint infection requires joint removal, treatment with antibiotics then joint replacement.