Bone Growth and Fractures

Question 1

When does growth in height end?

Answer 1

The end of puberty

Question 2

Describe the cessation of bone growth

Answer 2

Sex steroids stimulate growth spurt but promote closure of epiphyseal plates
Growth in length ceases, cell proliferation slows and plate thins
Plate is invaded by blood vessels, epiphyseal and diaphyseal vessels unite
May leave a line visible on x rays

Question 3

Where are the ossification centres in bones?

Answer 3

Depends:
Some have only one
• Carpals, tarsals, ear ossicles

Most bones have 2+
• Head of humerus has 3

Appearance in age varies
• Allows est. of skeletal vs chronological age
Rate of growth varies
• From bone to bone 
• Within same bone

Question 4

What are the zones of the epiphyseal plate?

Answer 4

Resting zone

Growth (proliferating) zone

Hypertrophic zone

Calcification zone

Ossification (osteogenic) zone

Question 5

What is an example of a disease in the resting zone of the epiphyseal plates?

Answer 5

Diastrophic dwarfism

- Defective collagen synthesis/processing of proteoglycans

Question 6

What is an example of a disease in the growth zone of the epiphyseal plates?

Answer 6

Achondroplasia Malnutrition
Irradiation injury
Gigantism

First 3 - Deficiency in cell proliferation and/or matrix synthesis

Gigantism - Increased cell proliferation

Question 7

What is an example of a disease in the hypertrophic zone of the epiphyseal plates?

Answer 7

Rickets
Osteomalacia

Insufficiency of calcium or phosphate for normal calcification

Question 8

What is an example of a disease in the metaphysis zone of the epiphyseal plates?

Answer 8

Osteomyelitis - Bacterial infection

Osteogenesis imperfecta - Abnormality of osteoblasts and collagen synthesis

Scurvy - Inadequate collagen turnover

Question 9

What does normal development of bone require?

Answer 9

– Calcium
– Phosphorus
– Vitamins A, C and D
– Balance between growth hormone, thyroid and parathyroid hormones, oestrogen and androgens

Question 10

What factors should be considered in describing mechanism of injury of a broken bone?

Answer 10

Direction of force
– Direct v angular
– Rotational
– Compression

Energy transfer
– Cause
– Site

Question 11

What can imaging tell you about a damaged bone?

Answer 11

Site & bones involved Clues on soft tissue injury Clues on energy transfer:
– Wide displacement
– Comminuted
– Multiple fracture sites
Pathological bone Paediatric bone

Question 12

What is the definition of a fracture?

Answer 12

A complete or incomplete break in a bone

Question 13

How should you describe a fracture?

Answer 13

Site
Open to surface Contaminated
Associated soft tissue injury
Joint involvement
Number of pieces 
Alignment
Degree of separation

Question 14

Name some fracture patterns yo

Answer 14

Traverse

Linear

Oblique non-displaced

Oblique displaced

Spiral

Greenstick

Comminuted

Question 15

What is an avulsion fracture?

Answer 15

– a fragment of bone is separated from the main mass

Question 16

What is a buckled fracture?

Answer 16

– a.k.a. impacted fracture, torus fracture
– ends are driven into each other
– commonly seen in arm fractures in children

Question 17

What is a compression or wedge fracture?

Answer 17

– usually involves the vertebrae

Question 18

What is a pathologic fracture?

Answer 18

– caused by a disease that weakens the bones

Question 19

What is a stress fracture?

Answer 19

– hairline crack

Question 20

What are some limb threatening or non-union risks?

Answer 20

– Dislocation
– Comminuted
– Compound
– Compartment syndrome
– Vascular / nerve injury
– Significant soft issue injury 
– Pathological bone

Question 21

What are ‘bone remodelling units’?

Answer 21

– Consist of osteoclasts and osteoblasts

– Keep adult bone mass relatively constant in the face of developmental, physiological and physical demands

Question 22

Discuss bone growth, remodelling and fracture repair

Answer 22

Depends on the activity of the cells of the periosteum
‘Bone Remodelling Units’
– Consist of osteoclasts and osteoblasts
– Keep adult bone mass relatively constant in the face of developmental, physiological and physical demands
Bone has a remarkable capacity to heal well (unlike articular cartilage).

Question 23

Discuss bone healing following a fracture

Answer 23

Fracture healing depends on the activity of osteoblasts in the local periosteum
Takes 2 -20 weeks for healing, depending on:
– Severity and position of the fracture
– Age of the patient

Question 24

What are the three major phases of fracture healing?

Answer 24

1. Reactive Phase
2. Reparative Phase
3. Remodelling Phase

Question 25

Discuss the reactive phase of fracture healing

Answer 25

• Fracture and inflammatory phase (haematoma)

* Fibroblasts in the periosteum proliferate to form granulation tissue around the fracture site

Question 26

Discuss the reparative phase of fracture healing

Answer 26

• Callus formation-osteoblasts quickly form woven bone, to bridge the gap
• Woven bone is weak as the collagen fibres are arranged irregularly
• Lamellar bone laid down-collagen organised in regular sheets to give strength and resilience

Question 27

Discuss the remodelling phase of fracture healing

Answer 27

• Remodelling by osteoclasts to restore original bone shape

Question 28

What are the treatments available for fractures?

Answer 28

Conservative
– Simple fracture with low risk of non-union
– Dependent on natural healing process
– +/- immobilisation
– Rehabilitation

Intervention
– Fractures with limb threat or risk of non union
– Augment natural healing with replacement or strengthening
– +/- immobilisation
– Rehabilitation

Question 29

What are the learning outcomes?

Answer 29

Recall the processes involved in endochondrial ossification
Recall the differences between a primary and secondary ossification centre
Recognise that disease and damage to the epiphyseal plate will affect bone growth
Classify different types of fracture patterns Describe the process of fracture healing