Bone and Joint Infections

Question 1

What is the source of most organisms getting into bone/joints ?

Answer 1

Definitely from outside, mainly from the skin

Question 2

How do bones become infected (osteomyelitis)/what are possible access routes to the bone ?

Answer 2

• Haematogenous spread (in most cases)
• Local spread (e.g. from septic arthritis)
• Compound fracture
• Foreign body (mainly as a result of surgery)

Question 3

Where, within the bone, does osteomyelitis tend to arise ? Why ?

Answer 3

In the epiphyseal plate/metaphysis, because that is an area of high vascularization so pathogens in the circulation often end of there.

Question 4

What are some predisposing factors to osteomyelitis ?

Answer 4

• Younger people much more prone than older people
• Sickle cell disease (due to Salmonella)
• Travel/foreign born (due to Brucella)
• Prosthesis (due to Staphylococcus epidermis)
• Children under 5 (due to H.influenzae, so rare in countries with Hib vaccination programme)
• UTI (especially in older people, due to E.coli and others)

Question 5

What are the organisms responsible for osteomyelitis ?

Answer 5

• S. aureus (>80%)
• S. pyogenes (~5%)
• M. tuberculosis
(Percentage applies to Scotland)

Question 6

Which bones of the body are particularly prone to osteomyelitis ?

Answer 6

Bones with growing epiphyses.

• Femur
• Tibia
• Calcaneum
• Humerus
• Fibula

Question 7

Define ostemyelitis.

Answer 7

Infection of the bone

Question 8

Describe Haematogenous spread of infection to bones in osteomyelitis.

Answer 8

• Usually asymptomatic, but skin sepsis may be present (but is usually absent)

Question 9

What are the main sources of foreign body infections in osteomyelitis.

Answer 9

• Orthopaedic implant (Knail) (most common)
• Trauma
• Shrapnel/Gun shot wound

Question 10

Identify the main signs and symptoms of osteomyelitis.

Answer 10

• Painful swollen site
• Fever
• Reduced movement (may be the only sign in very young)
• Paraplegia

Question 11

Identify the preliminary investigations for osteomyelitis.

Answer 11

• Fever
• WBC
• ESR (Erythrocyte Sedimentation Rate)
• CRP

Question 12

Identify Investigation which should be undertaken for osteomyelitis diagnosis.

Answer 12

• Blood culture (Take 3 cultures. May be negative early on in the course of infection, but that does not rule out osteomyelitis because it may take weeks to show abnormalities)
• X-ray
• MRI/CT/Bonescan
• Pus (to help identify organism, from operative sample)

Question 13

What would an X-ray of osteomyelitis show ?

Answer 13

• Reduced/absent space between vertebrae (vertebrae collapse)
• Demineralization of bones

Question 14

What may a bone scan with osteomyelitis show ? Would this be a definite proof of osteomyelitis ?

Answer 14

• Areas with infection (osteomyelitis) hotter than rest of the body (noticeably darker on scan)
• Not definitive proof of osteomyelitis because anything that causes inflammation results in such ‘hotter’ areas

Question 15

Describe the therapy required for osteomyelitis.

Answer 15

1) Standard Empirical Treatment
- Flucloxacillin/Fucidin (Flucloxacillin especially effective against staphylococcus aureus)

2) Alternative Empirical Treatment
- Fucidin/erythromycin or rifampicin (for ß- lactam allergy)
- Ciprofloxacin (for Salmonella infection)
- Isoniazid, Rifampicin, Pyrazinamide, Ethambutol
(tuberculosis)

3) Drainage/Removal of involucrum

Question 16

Define empirical therapy.

Answer 16

Therapy begun on the basis of a clinical educated guess in the absence of complete or perfect information, do not know causal organism

Question 17

Identify the sites of Septic Arthritis.

Answer 17

• Knee
• Hip
• Lumbosacral spine

Question 18

What are predisposing factors of Septic Arthritis ?

Answer 18

• Rheumatoid arthritis
• Injection of joint
• Prosthetic joint

Question 19

Identify causative Organisms for Septic Arthritis.

Answer 19

• S. aureus
• S.pyogenes
• S. epidermis
• M. tuberculosis
• Salmonella
• Brucella

Question 20

Identify investigation which should be undertaken for septic arthritis diagnosis.

Answer 20

• Blood culture
• Joint aspirate (Easier to get material out of septic arthritis than in OM)
• Joint X-ray

Question 21

Describe the therapy required for septic arthritis.

Answer 21

Same organisms as OM so same approach

1) Standard empirical
- Flucloxacillin/Fucidin

2) Alternatives empirical
- Fucidin/erthromycin or rifampicin (for ß- lactam allergy)
- Ciprofloxacin (for Salmonella infection)
- Isoniazid, Rifampicin, Pyrazinamide, Ethambutol
(tuberculosis)

Question 22

Define reactive arthritis and identify the organisms involved. Also identify the main symptoms.

Answer 22

-=post infectious arthritide. Painful form of inflammatory arthritis, in reaction to an infection by certain bacteria.
-Most often, these bacteria are in the genitals (Chlamydia) or the bowel (Rubella, meningococcus, Yersinia, Salmonella, Shigella, Campylobacter, Mumps)
Used to be called Reiter’s Syndrome
• Synovitis
• Conjunctivitis
• Sacroiliitis
• Aortitis
• Circinatebalinitis
• Keratodermablennorrhagica
• Presence of HLA B27 antigen (associated with ankylosing spondylitis)

Question 23

Identify the main risk factors for prosthetic joint infection, both in primary arthroplasty and revision (done for infection) arthroplasty.

Answer 23

PRIMARY: 
Rheumatoid Arthritis
Diabetes Mellitus
Poor Nutritional Status
Obesity
Concurrent UTI
Steroid Therapy
Malignancy
Postoperative surgical site infection

REVISION
Prior joint surgery
Prolonged operating room time
Preoperative infection (of teeth, skin, UTI)

Question 24

Identify the main organisms responsible for prosthetic joint infections.

Answer 24

Staph. Aureus
Coagulase negative staphylococci
Streptococci

Question 25

Describe the symptoms of Reitter’s Syndrome

Answer 25

• Synovitis
• Conjunctivitis
• Sacroiliitis
• Aortitis
• Circinatebalinitis
• Keratodermablennorrhagica
• HLA B27
• Associated with Clamydial infection

Question 26

Describe rheumatic fever.

Answer 26

• An example of post-infectious arthritide
• Occurs after streptococcal infection
• 70% of those affected with rheumatic get arthritis