Ortho / MSK

Question 1

What are the two most common causative organisms of Osteomyelitis in a healthy host?

Answer 1

1) Staph aureus
2) Streptococci (Strep pneumoniae, GAS, GBS)

Question 2

What is the most common causative organism of Osteomyelitis in patients with sickle cell disease?

Answer 2

Salmonella typhi

This is due to functional asplenia

Question 3

Pathophysiology of Osteomyelitis

Answer 3

Osteomyelitis most commonly occurs through haematogenous spread to the bone from bacteraemia.

Can also be through non-haematogenous spread, e.g. trauma, surgical procedures, where bone tissue is compromised and subsequently infected.

Question 4

What are the most common sites of infection in Osteomyelitis?

Answer 4

Long bones (particularly the distal femur and proximal tibia) followed by the Vertebrae

Question 5

What is involucrum in Osteomyelitits and what are its complications?

Answer 5

Separated viable periosteum.

New bone formation can generate from it leading to remodelling and occasionally deformities.

Question 6

Consequences/sequelae of Osteomyelitis

Answer 6

Infection and inflammation of the bone and periosteum may progress to necrosis.
Necrosed bone is referred to as sequestrum.

Destruction of the growth plates can occur in neonates but not in older children.

Question 7

What is acute haematogenous osteomyelitis and its time course.

Answer 7

Acute bacterial illness with fever followed by localised bone symptoms within 1 week

Question 8

What is subacute haematogenous osteomyelitis and its time course.

Answer 8

Insidious onset over 1-4 weeks with fewer systemic features and more pronounced localised bone signs. Usually caused by more atypical organisms, e.g. mycobacteria

Question 9

What is chronic osteomyelitis and its time course.

Answer 9

Lasts for months and is often the result of infection that has spread from a contiguous site, e.g. fractured bone, or infection with an unusual organism (e.g. Mycobacteria)

Question 10

X-ray changes seen in Osteomyelitis

Answer 10

Characteristic x-ray changes occur after 10-14 days with periosteal elevation/reaction and radiolucent metaphyseal lesions.

Question 11

Management of Osteomyelitis

Answer 11

4-6 weeks of IV Abx

Subacute/chronic OM or atypical organisms may require longer treatment durations

Question 12

When is surgery required in OM

Answer 12

If associated with septic arthritis (especially the hip)

If dead or necrotic bone is present

Question 13

Difference between OM and septic arthritis

Answer 13

OM = infection of bone
Septic arthritis = infection of a joint

OM is often associated with SA

Question 14

What % curvature in scoliosis requires surgery?

Answer 14

> 50%

Question 15

What are the types of developmental hip dysplasia?

Answer 15

Dislocated hip
Dislocatable hip
Subluxable hip
Dysplastic hip

Question 16

Risk factors for DDH

Answer 16

Female
First born
Family history
Fixed foot deformities
Breech presentation
Swaddling
Spina bifida
Oligohydramnios

Question 17

Ortolani and Barlow test findings in DDH

Answer 17

Ortolani - reduces a dislocated hip
Barlow - identifies dislocatable and subluxable hips

Question 18

Complications of DDH

Answer 18

Avascular necrosis of the proximal femoral physis
Growth disturbances
Coxa magna (circumferential overgrowth and deformity of the femoral head and broadening of the femoral neck)
Residual acetabular dysplasia

Question 19

Management of DDH

Answer 19

Pavlik harness - if fitted <6 weeks of age will be successful in approx 90% patients

Children diagnosed later may require surgery (closed or open reduction, osteotomy)

Question 20

Incidence of DDH

Answer 20

1.2 per 1000 births

Question 21

What % of patients with DDH are girls?

Answer 21

80%

Girls are more affected due to the circulating maternal hormone relaxin which increase ligamentous laxity

Question 22

Which hip is more commonly affected in DDH?

Answer 22

Left - accounts for 60% cases

Note 20% cases are bilateral

Question 23

Why is there an increased risk of DDH in breech presentation?

Answer 23

In utero knee extension of the infant in breech results in sustained hamstring forces around the hip and contributes to subsequent hip instability

Question 24

What is rarefaction of bone on XR and what condition is this found in?

Answer 24

Rarefaction of bone on XR = thinning of bone tissue

This is seen in TB arthritis, osteoporosis

Question 25

What is the imaging modality of choice in DDH?

Answer 25

USS

Question 26

Most common organism in Reactive Arthritis (Reiter’s)

Answer 26

Chlamydia trachomatis

Question 27

Imaging of choice in OM

Answer 27

MRI

X-ray will only show changes after 1 week

Question 28

XR findings in septic arthritis

Answer 28

Widened joint space due to increased synovial fluid

Question 29

What are the most common causative organisms in septic arthritis?

Answer 29

Staph aureus and Group A Strep

Question 30

Treatment for Septic Arthritis

Answer 30

4-6 weeks of Abx: usually oral stepdown after 2-4 weeks if clinical improvement seen