MSK Infections

Question 1

Which groups of patients are most prone to getting osteomyelitis?

Answer 1

Immunocompromised
Chronic disease
DM
Elderly
Young children

Question 2

What is the pathophysiology of osteomyelitis?

Answer 2

Bacteria may infect directly due to trauma or surgery, or may spread haematological from another site
As bacteria multiply, local osteolysis occurs and pus develops –> impairs blood flow making it very difficult to treat
Dead fragment of bone can form (sequestrum) –> antibiotics alone will not cure infection at this stage

Question 3

What is a Brodie’s abscess?

Answer 3

An abscess with a thin rim of sclerotic bone, can occur i children with subacute osteomyelitis

Question 4

What is Pott’s disease?

Answer 4

Chronic osteomyelitis in the spine caused by TB –> spread from lungs

Question 5

How is Pott’s disease diagnosed?

Answer 5

MRI spine

Question 6

Which organisms may cause osteomyelitis?

Answer 6

Staph aureus
Group A strep
Group B strep (neonates)
Enterobacter
H. influenza in children
P. aeruginosa (IVDU)
Salmonella

Question 7

Which group of patients get Salmonella osteomyelitis?

Answer 7

Sickle cell disease

Question 8

What are the clinical features of acute osteomyelitis?

Answer 8

Severe pain (may be absent in diabetic foot)
- constant and worse at night
Low grade pyrexia
Tender, swelling, erythema

Question 9

Which bloods should be done in acute osteomyelitis?

Answer 9

Routine + cultures

Question 10

Which mode of imaging is definitive for osteomyelitis?

Answer 10

MRI

Question 11

What is the role of xray in osteomyelitis?

Answer 11

Often done but has poor accuracy –> often appears normal until about 7-10 days

Question 12

What is the gold standard investigation for osteomyelitis?

Answer 12

Culture from bone biopsy at debridement

Question 13

What is the management for acute osteomyelitis?

Answer 13

Long term (>4 weeks) IV antibiotics
If abscess --> drain
If patient deteriorates or signs of progressive bone destruction --> debridement

Question 14

What are the complications of acute osteomyelitis?

Answer 14

Overwhelming sepsis
Children may develop growth disturbance due to premature physeal closure
Recurrence of infection
May develop chronic osteomyelitis

Question 15

What are the features of chronic osteomyelitis?

Answer 15

Localised ongoing bone pain + malaise/lethargy

May be a draining sinus tract

Question 16

How may investigation findings differ in chronic osteomyelitis?

Answer 16

Blood tests may be normal
Culture may be negative
(cultures from sinus tract often contaminants)

Question 17

What is the management for chronic osteomyelitis?

Answer 17

(antibiotics alone will not work)
–> surgical debridement + long term IV antibiotics
- complex staged reconstruction with internal/external fixation
- prolonged rehab
Amputation possible if patient not suitable for long rehab

Question 18

How might a surgical implant/prosthesis become infected?

Answer 18

From patient or theatre staff’s skin (during surgery)
Post-op before wound healed
Late via the blood

Question 19

What are the clinical features of an infected prosthesis?

Answer 19

Chronic infection
Pain
Poor function
Recurrent sepsis
Sinus formation
Implant loosening

Question 20

What are the consequences of infection of fracture stabilising materials?

Answer 20

Osteomyelitis

Non-union of fracture

Question 21

Which organisms are most likely to cause an early prosthesis infection?

Answer 21

Staph aureus

Gram -ve bacilli e.g. coliforms

Question 22

Which organisms are most likely to cause a late prosthesis infection (low grade, may take up to a year to be diagnosed)?

Answer 22

Staph epidermidis

Enterococcus

Question 23

How is an infected surgical prosthesis managed?

Answer 23

Washout + revision surgery usually required
- may need to be left without a joint while antibiotics treat the infection
Then new prosthesis

Question 24

What are the main causative organisms for septic arthritis?

Answer 24

Staph aureus (most common)
Streptococci
Gonorrhoea (sexually active)
Salmonella (sickle cell disease)

Question 25

How might the joint be affected long term following septic arthritis?

Answer 25

Irreversible damage to cartilage

Severe, early OA

Question 26

What are some risk factors for septic arthritis?

Answer 26

Age > 80
Pre-existing joint disease
DM
Immunosuppression
CKD
Joint prosthesis
IVDU

Question 27

What are the clinical features of septic arthritis?

Answer 27

Single, red, swollen, warm joint
Severely painful on active + passive movement
Pyrexia in 60%
Unable to weight bare
Symptoms often more subtle in a prosthetic joint

Question 28

How should a suspected septic arthritis be investigated?

Answer 28

Bloods including FBC, CRP, ESR, urate + blood cultures

JOINT ASPIRATION is essential, ideally before antibiotics

Question 29

Which tests need to be done on the joint aspirate which suspicious of septic arthritis?

Answer 29

gram stain, leukocyte count, polarising microscopy + culture

Question 30

How is septic arthritis managed?

Answer 30

Manage sepsis
Antibiotics for at least 4-6 weeks (IV for 2)
Surgical irrigation + debridement (washout)
- can be done open or arthroscopic
- may need to be done several times
If prosthetic joint –> washout + revision surgery