Children's Orthopaedics Flashcards
What is intramembranous ossification used for?
Flat bone development - clavicle and cranium
Describe process of intramembranous ossification
- A group of mesenchymal cells in the central ossification centres differentiate first into preosteoblasts and then intoosteoblasts.
- Cells then synthesize and secreteosteoidand the trapped osteoblasts further differentiate into osteocytes.
- Then collectively create the immature woven trabecular matrix and immature periosteium.
- Angiogenesis occurs and blood vessels incorporated between the woven bonetrabeculaewill form the future bone marrow. Later, the woven bone is remodeled and is progressively replaced by mature lamellar bone.
Describe stages of endochondral ossification
Used to form all other long bones. Occurs at primary and secondary ossification centres. Primary ossification centres are sites of pre-natal bone growth through endochondral ossification from the central part of the bone. Secondary ossification centres occur post-natally after the primary ossification centre and long bones often have several (the physis).
Describe process of endochondral ossification
The first site of ossification occurs in the primary center of ossification, which is in the middle ofdiaphysis of the bone – prenatal.
a) Mesenchymal Differentiation at the primary centre
b) The cartilage model of the future bony skeleton forms
c) Capillaries penetrate cartilage.
Calcification at the primary ossification centre – spongy bone forms
Perichondrium transforms into periosteum
d) Cartilage and chondrocytes continue to grow at ends of the bone
e) Secondary ossification centres develop with its own blood vessel and calcification at the proximal and distal end – calcification of the matrix
f) Cartilage remains at epiphyseal (growth) plate and at joint surface as articular cartilage.
What happens at secondary ossification centres?
In the children’s skeleton, cartilage remains at the joint surface as articular cartilage and between the diaphysis and epiphysis as the epiphyseal plate (physis). Physis is responsible for the futher growth of bones.
The physis has various zones. On epiphyseal side, hyaline cartilage active and dividing to form hyaline cartilage matrix. On diaphyseal side, cartilage calcifies and dies and is then replaced by bone.
How does growth at physis occur and why is it key?
By the proliferation of chondrocytes and the subsequent calcification of the extracellular matrix into immature bone that is then subsequently remodelled. Physis is responsible for skeletal growth of child. Any congenital malfunction to this area or acquired insult – weather it is traumatic/infective or otherwise will therefore have a subsequent impact on growth of the child.
Why are children’s skeletons more elastic than adult ones?
Increased density of Haversian canals as bone is more metabolically active since continuously growing. Hence more plastic deformity occurs (bending before breaking). Torus fractures (buckle) common in children following FOOH as wrist absorbs impact and compresses on one side but remains intact on other side creating bulge. Greenstick fractures also common where bone doesn’t break all the way through.
What are 2 points about physis?
- Growth occurs at varying rates at varying sites
- Growth stops as the physis closes - gradual physeal closure depends on puberty, menarche and parental height - occurs for girls around 15/16 and boys 18/19.
What is the consequence of physeal injury?
Categorised by Slater-Harris and lead to growth arrest. This leads to deformity.
What is the speed and remodelling of bone dependent on?
Location and age of patient. Younger child heals more quickly. Distal femur and proximal tibia grow more – injuries in areas where there is more growth heal faster in a child as physis at knee and extremes of upper limb grow more.
What is developmental dysplasia of the hip?
Group of disorder of the neonatal hip where the head of the femur is unstable or incongruous in relation to the acetabulum. Normal development relies on the concentric reduction and balanced forces through the hip in utero and hence is a packaging disorder.
Describe spectrum of developmental dysplasia of hip
Mild cases dysplasia – hip within socket but not centrally placed and therefore socket doesn’t develop into cup shape.
Subluxation more severe – hip in the socket but due to shallow nature of socket, pops in and out.
Dislocation – hip has never been in the socket and develops outside of it so acetabulum is extremely shallow as never had the pressure.
Dysplasia affects 2 in 100
Dislocation affects 2 in 1000
What are risk factors for developmental dysplasia of hip?
Female 6:1
First born
Breech position of baby
Family history
Oligohydramnios - when not even amniotic fluid
Native American/Laplanders – swaddling of hip
Rare in African American/Asian
Describe examination and investigations used for developmental dysplasia of hip
Usually picked up on baby check screening - range of movement limited in hip abduction and Galaezzi test (leg length). Barlow and Ortalani test insensitive in those 3 months or older.
Ultrasound used to investigate from birth to 4 months as secondary ossification centres not developed and so X-ray cannot be used. If prior to 6 weeks, must be age adjusted.
What is the treatment for developmental dysplasia of hip?
If reducible hip and less than 6 months old, Pavlik harness is 92% effective. Pavlik harness holds the femoral head within the acetabulum so as child grows, get the concentric pressures through the hip joint which supports further normal development. If Pavlik harness fails or abnormalities picked up too late, surgical intervention may be needed. Manipulation under anaesthetic with closed reduction and spica may be needed.
