PAEDIATRIC ORTHOPAEDICS
SPINE EMBYROLOGY
Development of the spine
spine derived from notocord (from ectoderm) è notocord secretes Shh (sonic hedgehog) to stimulate ectoderm to produce neural tube,
Week 2:
somite and subsequent sclerotome
Paraxial mesoderm develops into segments of somite è divides into sclerotome (vertebra/ribs), dermatome (skin) and myotome
(muscle)
Week 3: • Myotome ® SKM of neck, trunk and limbs
• Dermatome ® CT, dermis of skin
• Scleroteome ® vertebra, thoracic ribs and Cartilage (brown) derived from sclerotome surrounds neural tube
spinous process and vertebral body develops as well as nucleus pulposus (formed from notocord)
• Upper limbs buds develop 1st (2 days before lower limbs) è digit formmation
Week 4:
o Incomplete apoptosis = syndactylyl or polydactyly
• Closure of neural tube to protect spinal cord è failure = spina bifidia occulta è hunched back, lower limb paralysis
• RIBS: develop from transverse processes of thoracic vertebrae
a. Fibrous septa between body wall muscle è becomes cartilaginous è start to ossify by week 8.
Week 4-5:
• STERNUM: Parallel fibrous sternal bars è become cartilaginous è start to ossify by week 8.
• 2 manubrium and 2 left/right sternum fuse by birth (BUT ossification not completed as xiphisternum ossifies later in life)
Week 6 Synovial joints develop ® peripherally forms joint capsule and centrally disappears to form joint cavity
Motor axons from spinal cord enter the limb buds
Week 5-7
• Sensory axons enter the limb after the motor axons
• Upper limbs rotate dorsally
Week 8
• Lower limbs rotate ventrally – extensors anteriorly and flexors posteriorly
(a)What induces the neural tube to form? (b) what vitamin is essential? (c) name a neural tube defect.
(a) Notocord
(b) Neural Tube Defects è linked to insufficient maternal intake of folate acid (vitamin B9)
(c) Spinal bifida occulta, meningocoele (i.e. meninges + CSF bulging out), anencephaly
What problem can a cervical rib cause?
• if cervical transverse process develops a cervical rib è thoracic outlet syndrome è occupies space in thoracic outlet
and compress neurovascular structures
Have the left and right sternal bars fused by birth?
Yes, but no ossification
o if no fusion èsternal cleft è gap between ribs è abnormal respiration and no protection of heart and lungs
o if incomplete fusion è sternal foramina (holes in sternum)
SPINE EMBYROLOGY
Development of the spine
spine derived from notocord (from ectoderm) è notocord secretes Shh (sonic hedgehog) to stimulate ectoderm to produce neural tube,
Week 2:
somite and subsequent sclerotome
Paraxial mesoderm develops into segments of somite è divides into sclerotome (vertebra/ribs), dermatome (skin) and myotome
(muscle)
Week 3: • Myotome ® SKM of neck, trunk and limbs
• Dermatome ® CT, dermis of skin
• Scleroteome ® vertebra, thoracic ribs and Cartilage (brown) derived from sclerotome surrounds neural tube
spinous process and vertebral body develops as well as nucleus pulposus (formed from notocord)
• Upper limbs buds develop 1st (2 days before lower limbs) è digit formmation
Week 4:
o Incomplete apoptosis = syndactylyl or polydactyly
• Closure of neural tube to protect spinal cord è failure = spina bifidia occulta è hunched back, lower limb paralysis
• RIBS: develop from transverse processes of thoracic vertebrae
a. Fibrous septa between body wall muscle è becomes cartilaginous è start to ossify by week 8.
Week 4-5:
• STERNUM: Parallel fibrous sternal bars è become cartilaginous è start to ossify by week 8.
• 2 manubrium and 2 left/right sternum fuse by birth (BUT ossification not completed as xiphisternum ossifies later in life)
Week 6 Synovial joints develop ® peripherally forms joint capsule and centrally disappears to form joint cavity
Motor axons from spinal cord enter the limb buds
Week 5-7
• Sensory axons enter the limb after the motor axons
• Upper limbs rotate dorsally
Week 8
• Lower limbs rotate ventrally – extensors anteriorly and flexors posteriorly
(a)What induces the neural tube to form? (b) what vitamin is essential? (c) name a neural tube defect.
(a) Notocord
(b) Neural Tube Defects è linked to insufficient maternal intake of folate acid (vitamin B9)
(c) Spinal bifida occulta, meningocoele (i.e. meninges + CSF bulging out), anencephaly
What problem can a cervical rib cause?
• if cervical transverse process develops a cervical rib è thoracic outlet syndrome è occupies space in thoracic outlet
and compress neurovascular structures
Have the left and right sternal bars fused by birth?
Yes, but no ossification
o if no fusion èsternal cleft è gap between ribs è abnormal respiration and no protection of heart and lungs
o if incomplete fusion è sternal foramina (holes in sternum)
