1B children orthopaedics Flashcards
How many bones in a child skeleton?
270
What are the blue lines?
- The physis (growth plates) that are the areas from which long bone growth occurs post-natally
- Each long bone usually has 2- one at proximal and one at distal end
Describe the steps of intramembranous ossification
1) Condensation of mesenchymal cells which differentiate into osteoblasts- ossification centre forms
2) Secreted osteoid traps osteoblasts which become osteocytes
3) Trabecular matrix and periosteum form
4) Compact bone develops superficial to cancellous bone. Crowded vessels condense into red bone marrow
5) Immature woven bone remodelled and progressively replaced by mature lamellae bone
What bones use intramembranous ossification?
Flat cranial bones and clavicle
Describe endochondral ossification in terms of what the ossification centres do
- Primary ossification centres
- Sites of pre-natal bone growth through endochondral ossification from the central part of the bone
- Secondary ossification centres
- Occurs post-natal after the primary ossification centre and long bones often have several (the physis)
Describe primary ossification steps
1) Mesenchymal differentiation at the primary centre (in the diaphysis or middle of the shaft of bone) in the prenatal period
2) Cartilage model of future bony skeleton forms
3) Capillaries penetrate cartilage and calcification occurs to form spongy bone which forms up the shaft. Perichondrium transforms into periosteum
4) Cartilage and chondrocytes continue to grow at ends of the bone
5) Secondary ossification centres develop at proximal and distal ends of long bones with its own blood supply which begins to calcify matrix into immature spongy bone
Left with cartilage at distal and proximal ends of bone with epiphyseal growth plate which will be point of secondary endochondral ossification in post natal period
Describe secondary ossification steps
- By the time the child is born the cartilage remains at the front surface as articular cartilage and in between diaphysis and epiphysis as the epiphyseal plate (aka physis)
- These physes are responsible for elongation of the long bone
- Epiphyseal side- hyaline cartilage is active and dividing to form hyaline cartilage matrix
- Diaphyseal side- cartilage calcifies and dies and then replaced by bone
What are the 4 ways a child’s skeleton differs to that of an adult?
- Elasticity
- Physis
- Speed and remodelling potential
- Remodelling
How does a child’s skeleton elasticity differ to that of an adult?
- Children’s bones have increased elasticity than adults
- This is due to increased density of Haversian canals (tunnels in bone cortices that circulate the blood supply) due to child bones being more metabolically active since they continually grow
What does increased elasticity lead to in child bones?
- Plastic deformity- bends before breaks
- Buckle fracture- Torus structure like columns
- Greenstick- like the tree- one side snaps and other side buckles instead of breaking
How does a child’s skeleton physis differ to that of an adult?
Growth occurs at varying rates at different physis sites
Growth stops as physis closes- what influences this to happen?
- Gradual physeal closure
- Puberty
- Menarche
- Parental height
What age does physis close?
- Girls 15-16
- Boys 18-19
What can physeal injuries lead to?
Growth arrest which can lead to deformity- one part of bone continues to grow but other has stopped
How are physeal injuries classified?
Salter-Harris
How is a child’s skeleton speed and remodelling potential different from an adults?
- Speed of healing and remodelling potential is dependent on the location and the age of the patient
- Younger child heals more quickly
- Physis at knee grows more (distal femur and proximal tibia)
- Physis at extremes of upper limb grows more (around shoulder and wrist)
How is a child’s remodelling skeleton different from an adults?
Remodelling potential in a child is way more than in an adult e.g. below proximal humeruses are very broken in a 9 year old child but in 2 years (below image) it has completely remodelled to show no visible deformity or functional restriction
What are some common children’s congenital conditions?
- Developmental dysplasia of hip
- Congenital Talipes Equinovarus
- Achondroplasia
- Osteogenesis Imperfecta aka brittle bone disease
Define developmental dysplasia of hip
- A 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’
- The normal development of hip and acetabulum relies on the concentric reduction and balanced forces through the hip
Describe the spectrum of developmental dysplasia of hip
- Dysplasia (mild cases)- hip may be within socket but not centrally placed so socket doesn’t develop into a cup
- Subluxation- hip may be in socket but socket is shallow so hip can pop in and out
- Dislocation (severe)- hip develops outside of socket and socket develops as a very shallow cup
How common is dysplasia?
2:100
How common is dislocation?
2:1000
What are risk factors of developmental dysplasia of hip?
- Female children 6:1
- First born
- Breech position
- Family history
- Oligohydramnios (abnormally low level of amniotic fluid)
- Native American/Laplanders due to habit of swaddling of hip once child is born
- Rare in African American and Asian populations
What is oligohydramnios?
Not enough fluid in amniotic sac
How is developmental dysplasia of the hip investigated?
Ultrasound from birth to 4 months
What investigation for developmental dysplasia of the hip is used for premature babies/ babies older than 4 months and why?
- After 4 months X-ray done since US isn’t sensitive after 4 months
- If prior to 6 weeks you need to age adjust the test since you can find abnormal results in premature children
How is developmental dysplasia of the hip treated?
Pavlik harness
92% effective in a reducible hip and <6 months
What do we do if Pavlik harness fails or baby is 6-18 months (so DDH picked up late)?
Surgery- MUA + closed reduction and Spica
What is the aim of developmental dysplasia of the hip treatment?
It’s not about preventing morbidity but to give child normal development of hip because DDH is progressive so when adolescent the patient has no issues
What is clubfoot/ congenital talipes equinovarus?
Congenital deformity of the foot
Which groups is clubfoot more common in?
- 1 in 1000
- Highest in Hawaiians
- M:F is 2:1
- 50% are bilateral
How is clubfoot caused?
- Genetic- PITX1 gene
- Approx 5% likely to affect future siblings
- Familial in 25% of cases
What are the deformities present in clubfoot?
- CAVE deformity due to muscle contracture- described as club foot overall
- Cavus- high arch- tight intrinsic, FHL (flexor halluces longus), FDL (flexor digitorum longus)
- Adductus of foot: tight tibia posteriorly and anteriorly
- Varus: tight tendoachilles, tibial post and tib ant
- Equinous: tight tendoachilles
What is the gold standard for treatment of clubfoot?
1) Gold standard is the Ponseti method: a series of casts are used to correct deformity
2) Many require operative treatment e.g. soft tissue releases
3) Foot orthosis brace (bottom pic)
4) Some will require further operative intervention to correct final deformity
What is achondroplasia a form of?
The most common skeletal dysplasia
What causes achondroplasia?
- Autosomal dominant
- G380 mutation of FGFR3
- Causes inhibition of chondrocyte proliferation in the proliferative zone of the physis
- Results in defect in endochondral bone formation
How does achondroplasia present?
Rhizomelic dwarfism
- Humerus shorter than forearm
- Femur shorter than tibia
- Normal trunk
- Adult height of approx 125cm
- Normal cognitive development
- Significant spinal issues
What is the heredity of osteogenesis imperfecta like?
Autosomal dominant or recessive
What does osteogenesis imperfecta cause a problem in?
Decreased Type I collagen due to either:
- Decreased secretion (quantity of collagen)
- Production of abnormal collagen (quality of collagen)
How does osteogenesis imperfecta manifest in bones?
- Fragility fractures
- Short stature
- Scoliosis