Children's Orthopaedics Flashcards
How does a child’s skeleton differ from an adult’s skeleton?
Paediatric skeleton is NOT a miniaturised version of an adult
Children have more bones - 270 bones that are in continuous change
- Bones contain physis (growth plates) - in long bones (2 physes in each long bone)
- More elastic
- Increased speed of healing
- Greater remodeling potential - i.e. amount of deformity that can be corrected as a result of the growth that the child is going through
What are the two pathways of bone development?
Intramembraneous = development of flat bones i.e. how the cranial bones and clavicle are formed Endochondral = how all the other long bones in the body are formed
How does intramembraneous ossification take place?
Condensation of mesenchymal cells which differentiate into osteoblasts – ossification centre forms
These cells secrete osteoids, which trap further osteoblasts
Osteoblasts become osteocytes –> these create the immature, woven trabecular matrix and periosteum
After this, angiogenesis occurs and the crowded blood vessles incorporated between the woven and trabecular bone condence to form the future red bone marrow
Finally, this immature woven bone is remodelled ad progressively replaced by mature lamellar bone
Compact bone develops superficial to cancellous bone
What is endochondral ossification?
The tissue that will become bone is firstly formed as cartilage
How does endochondral ossification take place?
Occurs in 2 different ways:
- Primary Ossification Centres = sites of pre-natal bone growth through endochondral ossification from the central part of the bone i.e. the diaphysis
- Secondary Ossification Centres = occurs post-natal after the primary ossification centre at the physis, and long bones often have several physis
What is primary endochondral ossification?
Occurs at the primary centres i.e. the middle of the diaphysis / shaft of the bone
Occurs during the prenatal period
- Mesenchymal Differentiation at the primary centre
- Develops into a cartilage model of the future bony skeleton forms
- Via angiogenesis, capillaries penetrate cartilage creating the primary ossification centre
Calcification at the primary ossification centre = spongy bone formation in the middle of the bone sfhaft, spreading to the ends
Perichondrium transforms into periosteum - Cartilage and chondrocytes continue to grow at ends of the bone
- Secondary ossification centres develop with its own blood vessel and the blood supply allows for calcification at the proximal and distal end = calcification of the previously uncalcified matrix into immature spongey bone
- Cartilage remains at epiphyseal (growth) plate and at joint surface as articular cartilage
What is the role of the physis?
It is the secondary ossification centre - responsible for the further growth of bones via secondary endochondral ossification
What happens if the physis are faulty?
Any congenital malfunction to this area or acquired insult – whether it is traumatic/infective or otherwise will therefore have a subsequent impact on growth of the child
What is secondary endochondral ossification?
Responsible for long bone lengthening
Once the child is born, cartilage remains at the joint surface as articular cartilage between the diaphysis and epiphysis as the epiphyseal plate AKA a physis
Physis contain various zones
All zones have a role in the growth of the long bone - occurs via proliferation of the chondrocytes and subsequent calcification of extracellular matrix into immature bone, which is then remodelled
How do the different zones in the physis carry out secondary endochondral ossification?
Zone of elongation in long bone
Contains cartilage
Epiphyseal side – hyaline cartilage active and dividing to form hyaline cartilage matrix
Diaphyseal side – Cartilage calcifies and dies and then replaced by bone
Why are children’s bones more elastic (more bendy) than an adults?
Children’s bones have an increased density of Haversian Canals - these are microscopic tunnels within the cortices of the bones that circulate the blood supply
Why do children have more Haversian Canals?
Children’s bones are more metabolically active as they are continuously growing so they require a greater density of haversian canals
What are the 3 properties of a child’s bone due to the increased elasticity from the Haversian Canals?
- Plastic deformity - when an energy is dissipated though the bone, the bone will bend more before it eventually breaks, therefore differet fracture patters are seen when children sustain injuries
- Buckle fracture - caused from the bone bending more before fracturing, e.g. when a child falls onto an outstretched hand, instead of the bone fractures, it actually buckles in on itself and creates this tarus like structure
- Greenstick injury - bone does not snap in half, bendiness causes one side to break but the other side buckles and bends
Are the growths at all the physis the same?
No, growth rates at different physis vary
Upper limb = extremes i.e. shoulder and wrist
Lower limb = around the knees i.e. distal femur, proximal tibia
When and why does growth stop?
When the physis close (gradual physeal closure) - dependent on puberty, menarche, parental height
When does growth stop in girls and boys?
Girls = 15-16 Boys = 18-19
How are physeal injuries categorised and what are physeal growth deformities?
Physeal injuries are categorised by Salter-Harris
Physeal injuries can lead to growth arrest
Growth arrest can lead to deformity
What does the speed of healing and remodeling depend on?
Age and location
So esp. in children, at the physis where there is the greatest growth, there is the fastest healing due to the largest remodelling potential
Why do children heal more quickly?
As they have significantly greater remodelling potential
What are common children’s congenital conditions?
Development dysplasia of the hip
Club foot
Achondroplasia
Osteogenesis Imperfecta
What is Development dysplasia of the Hip (DDH)?
Group of disorders of the neonatal hip where the head of the femur is unstable or incongruous in relation to the acetabulum
A ‘Packaging Disorder’
When and why does DDH occur?
Occurs in utero and depends on how they sit in the womb - affects the way the hip sits within the acetabulum as the normal development of the hip and acetabulum rely on the concept of concentric reduction and blances forces through the hip
As DDH is a group of disorders, what is it comprised of?
It is a spectrum, from mild to severe:
Dysplasia (mild - hip within the socket but not quite centrally placed so socket does not develop into ‘cup’) –> subluxation (moderate - at times the hip is in the socket, but the shallow nature of the socket means the hip pops in and out) –> dislocation (severe - the hip has never been inside the socket and so develops outside of it so cup is v. v. shallow)
How common is dysplasia and dislocation?
Dysplasia = 2:100 Dislocation = 2:1000
