Children's orthopedics Flashcards
What are the 2 types of bones in our body?
- Flat bones
- Long bones
What process of bone development is used to form long bones and flat bones?
Flat bones= Intramembranous
Mesenchymal cells»bone
Long bones= Endochondral
Mesenchymal»cartilage»bone
Which bone development process is more clinically relevant?
Endochondral- based on ossification centres
Describe the process of Intramembranous ossification
- Condensation of mesenchymal cells which differentiate into osteoblasts – Ossification centre forms (start building bone without any cartilage model)
- Secreted osteoid traps osteoblasts which become osteocytes
- Trabecular matrix and periosteum form
- Compact bone develops superficial to cancellous bone. Crowded blood vessels condense into red bone marrow
Describe the process of endochondral ossification?
- Mesenchymal cells first differentiate into chondrocytes, that build a hyaline cartilage model, which will then turn into bone
- The centre/ diaphysis of this cartilage model is the primary ossification centre and blood vessels (nutrient artery) enter it, which bring in nutrients, osteoblast cells (to build bone) and osteoclast cells (to reabsorb bone)
- The osteoblasts start to replace the chondrocytes and they replace the cartilage with bone
- As the bone grows thicker and sturdier, osteoclasts start to reabsorb bone in the middle of the bone, making it more prous- bone marrow formation and elongation of diaphysis and epipheyseal plate formation (as you continue to get bone deposition by osteoblasts)
- Secondary ossification forms at epiphysis, and spongy bone is formed, cartilage only remains at the articular cartilage and epiphyseal plate
What is the primary ossification centre?
Sites of pre-natal bone growth through endochondral ossification from the central part of the bone
What is the secondary ossification centre?
Occurs post-natal after the primary ossification centre and long bones often have several (the physis)
In what 2 ways can bones grow?
- Interstital growth (elongation)
- Appositional growth (getting wider)
Describe the process of bone lengthening
“Interstitial growth”
1. At epiphyseal side- hyaline cartilage gets activated and chondrocytes in cartilage proliferate and mature to produce hyaline cartilage matrix, as more cartilage is produced the bones lengthen
2. At diaphyseal side- as cartilage calcifies and it gets older, chondrocytes die off, osetoblasts move into cartilage and start to ossify it (turn it into bone)
3. Articular cartilage covering tips of the bone also expands by secreting more matrix to cover the expanding bone
4. By the end of adolescence, the growth plate is completely ossified and at that point a person can’t grow taller
Describe the process of bone widening
“Appositional growth”
- Happens by osteoblasts laying down new circumferential lamellae in periosteum, so the bone grows outwards. At the same time osteoclasts in medullary cavity reabsorb bone so bone doesn’t get too heavy
What are the key differences in the bone of children vs adults?
Children:
- Presence of physis (growth plate) and epiphysis
- Less lamella
- Immature bone- less dense with greater porosity. (blood vessels to carry nutrients)
- Thick periosteum (soft tissue layer that surrounds bone- provides remodelling potential, harder for kids to break; stays intact for them even if bone is broken
What is the clinical significance of the ossification centres?
We need to know at what age different ossifications form- to determine what children have damaged secondary centres from injuries
Compare the elasticity in children’s bones with adults
Children’s bone can bend – more elastic than adult
Increased density of haversian canals
What type of “bone bending” fractures can occur in children?
- Plastic deformity – bends before breaks
- Buckle fracture – Torus like the column:
* One side of a bone bends, raising a little buckle, without breaking the other side of the bone
* usually happens when the bone is compressed (pressed together with force) - Greenstick – like the tree: One cortex fractures but does not break the other side
How are bends/ these fractures treated?
- Treated like a normal fracture- still displaced (some bends can be left with no intervention- straightens on it’s own)
- Chance of remodeling depends on the age of the child
What is the significance of the physis in bone growth?
- Growth occurs at varying rates at varying sites (some physis of different bones more active than others (fracrure where there is more growth + remodelling- much more worried about injuries)
- Growth stops as the physis closes (different physis close at different times
- Gradual Physeal closure, Puberty, Menarche, Parental height: Complete at (Girls 15-16 and Boys 18-19)
- Physeal injuries are catgorised by Salter-Harris
- Physeal injuries can lead to growth arrest (can occur on one side of a physis= bending deformity)
- Growth arrest can lead to deformity
What is the speed of healing and remodeling of bone?
- The speed of healing and remodeling potential is dependent on the location and the age of the patient
- Younger child heals more quickly
- Physis at the knee grows more
- Physis at extreme of upper limb grows more
Why is rotation important to note in a fracture?
Fractures in the direction/ plane as the movement of a joint more likely to heal than a fracture from a joint rotated; rotation is v. important to follow
What are the possible patterns of fractures?
- Transverse
- Oblique
- Spiral (spiral fracture is always rotational)
- Comminuted
- Avulsion (bone is pulled off by ligament/ tendon)
What is a transverse fracture?
Transverse fractures occur when your bone is broken perpendicular to its length