Infection of Locomotor Tissues

Question 1

What is septic arthritis?

Answer 1

Surgical emergency where there is infection of a joint + bacteraemia
-mortality 10%

Question 2

What is the typical form of spread in septic arthritis?

Answer 2

Haematogenous

-typically from skin/resp tract

Question 3

What are the risk factors for septic arthritis?

Answer 3

Extremes of age
Pre-existing joint disease (RA)
IVDU
DM/immunosuppression
Recent op/injective procedure

Question 4

What are the most likely causative organisms of septic arthritis?

Answer 4

Staph. aureus (most common)
Disseminated gonococcal (young adults)
Strep pneumonia/haem influenzae (children)

Question 5

What is Osteomyelitis?

Answer 5

Infection of bone

-carries same risk factors/organisms as SA

Question 6

What are the common sites for acute Osteomyelitis?

Answer 6

Metaphyseal plates of long bones (in children)

Spine (in immunosupressed adults)

Question 7

What are the risk factors for chronic Osteomyelitis?

Answer 7

Open fractures

Operative procedures

Question 8

How do SA/Osteomyelitis present?

Answer 8

Acute/subacute monoarthritis
-hot/swollen/erythematous joint
Joint held in ‘loose pack’ position

Question 9

What are the signs on examination of SA/Osteomyelitis?

Answer 9

Fever & systemic sx
Demonstrable effusion
Loss of movement of the joint
Extreme pain w/ even passive movement

Question 10

Which joints are most commonly affected in SA/Osteomyelitis?

Answer 10

Knee

Hip

Question 11

What is the differential diagnosis for SA/Osteomyelitis?

Answer 11

Crystal arthritis
Reactive arthritis
Overlying cellulitis
Monoarticular presentation of RA/CTD/seroneg arthritis

Question 12

How does acute Osteomyelitis present?

Answer 12

In a child w/
   -continuous pain
   -throbbing
   -worse at night
Fever
Malaise
Local swelling
Erythema
Warmth/oedema

Question 13

What investigations may be appropriate in suspected SA/Osteomyelitis?

Answer 13

Joint aspiration (gram stain, synovial fluid culture)
-aspirate in theatre if prosthetic/not readily accessible
Blood cultures
FBC, ESR, CRP, uric acid, clotting

Question 14

What is the management of SA/Osteomyelitis?

Answer 14

A-E resus
Admission under orthopaedics
IV a/b, after joint aspiration (2g Fluclox 6hrly)
   -continue for 2wks
   -6wks of oral treatment
Analgesia
Early source control (in theatre washout)
Early active rehabilitation

Question 15

What is the underlying pathophysiology of locomotor sepsis?

Answer 15

Joint invaded
-haematological spread OR
-eruption of bone abscess
-directly through penetrating wound
Infection spreads through joint, destroys cartilage
Pus forms abscesses & sinuses
Raw articular surfaces adhere –> ankylosis

Question 16

What are the X-ray changes in Septic Arthritis?

Answer 16

Soft tissue swelling in first 2wks
   -widening of joint space due to effusion
Cartilage later destroyed
   -narrowed joint space
   -bone destruction & ankylosis

Question 17

What is the underlying pathophysiology of Osteomyelitis?

Answer 17

Inflammation
-acute inflam response, inc intraosseous pressure, intense pain
Supparation
-pus appears in medulla (2/7), forms subperiosteal abscess
Necrosis
-compromised blood supply, necrosis by (7/7)
New bone formation
Resolution

Question 18

What are the imaging abnormalities of Osteomyelitis?

Answer 18

No abnormality on XR for 10/7
Inc bone activity on radioisotope scans
Reduced bone density & new bone formation by 2wks
Sclerosis/thickening of cortex

Question 19

What causes viral arthralgia?

Answer 19

Any viral infection

-occurs during prodromal phase, along w/ viral rash

Question 20

How does viral arthralgia present?

Answer 20

Symmetrical, non-destructive

Occurs along w/ viral rash

Question 21

What investigations may be appropriate in suspected viral arthralgia?

Answer 21

Viral titres/antigens

RF