Ortho / MSK Flashcards
What are the two most common causative organisms of Osteomyelitis in a healthy host?
1) Staph aureus
2) Streptococci (Strep pneumoniae, GAS, GBS)
What is the most common causative organism of Osteomyelitis in patients with sickle cell disease?
Salmonella typhi
This is due to functional asplenia
Pathophysiology of Osteomyelitis
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.
What are the most common sites of infection in Osteomyelitis?
Long bones (particularly the distal femur and proximal tibia) followed by the Vertebrae
What is involucrum in Osteomyelitits and what are its complications?
Separated viable periosteum.
New bone formation can generate from it leading to remodelling and occasionally deformities.
Consequences/sequelae of Osteomyelitis
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.
What is acute haematogenous osteomyelitis and its time course.
Acute bacterial illness with fever followed by localised bone symptoms within 1 week
What is subacute haematogenous osteomyelitis and its time course.
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
What is chronic osteomyelitis and its time course.
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)
X-ray changes seen in Osteomyelitis
Characteristic x-ray changes occur after 10-14 days with periosteal elevation/reaction and radiolucent metaphyseal lesions.
Management of Osteomyelitis
4-6 weeks of IV Abx
Subacute/chronic OM or atypical organisms may require longer treatment durations
When is surgery required in OM
If associated with septic arthritis (especially the hip)
If dead or necrotic bone is present
Difference between OM and septic arthritis
OM = infection of bone
Septic arthritis = infection of a joint
OM is often associated with SA
What % curvature in scoliosis requires surgery?
> 50%
What are the types of developmental hip dysplasia?
Dislocated hip
Dislocatable hip
Subluxable hip
Dysplastic hip
Risk factors for DDH
Female
First born
Family history
Fixed foot deformities
Breech presentation
Swaddling
Spina bifida
Oligohydramnios
Ortolani and Barlow test findings in DDH
Ortolani - reduces a dislocated hip
Barlow - identifies dislocatable and subluxable hips
Complications of DDH
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
Management of DDH
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)
Incidence of DDH
1.2 per 1000 births
What % of patients with DDH are girls?
80%
Girls are more affected due to the circulating maternal hormone relaxin which increase ligamentous laxity
Which hip is more commonly affected in DDH?
Left - accounts for 60% cases
Note 20% cases are bilateral
Why is there an increased risk of DDH in breech presentation?
In utero knee extension of the infant in breech results in sustained hamstring forces around the hip and contributes to subsequent hip instability
What is rarefaction of bone on XR and what condition is this found in?
Rarefaction of bone on XR = thinning of bone tissue
This is seen in TB arthritis, osteoporosis
What is the imaging modality of choice in DDH?
USS
Most common organism in Reactive Arthritis (Reiter’s)
Chlamydia trachomatis
Imaging of choice in OM
MRI
X-ray will only show changes after 1 week
XR findings in septic arthritis
Widened joint space due to increased synovial fluid
What are the most common causative organisms in septic arthritis?
Staph aureus and Group A Strep
Treatment for Septic Arthritis
4-6 weeks of Abx: usually oral stepdown after 2-4 weeks if clinical improvement seen
