Bone Growth and Fractures

Question 1

Describe the cessation of bone growth

Answer 1

Growth in height ceases at the end of puberty, sex steroids stimulate growth spurt but promotes closure of the epiphyseal plate

Question 2

Describe features ossification centres

Answer 2

Some bones have only 1 (carpals, tarsals ear ossicle). Most have two (head of humerus has 3), appearance in age varies which allows estimate of age via skeleton. The rate of growth varies.

Question 3

Describe the events at the epiphyseal plate (endochondrial ossification)

Answer 3

Resting zone - chondroblasts putting down cartilage model. Proliferating Zone - Chondoblasts under go mitosis and increase in No. Hypertrophic zone - Chondroblasts become entombed and differentiate into chondrocytes, they swell by increasing cytoplasm. Calcification Zone - Swelling causes spontaneous mineralisation. Ossification Zone - Bone becomes remodelled.

Question 4

Describe some of the pathological defects in the resting zone

Answer 4

Defective collagen synthesis/processing of proteoglycans which can lead to diastrophic dysplasia.

Question 5

Describe some pathological defects in the Growth zone

Answer 5

Deficiency in cell proliferation/matrix synthesis. Can lead to achondroplasia. Increased cell proliferation can lead to gigantism.

Question 6

Describe some defects in the hypertrophic zone

Answer 6

Insufficiency of calcium or phosphate for normal calcification. This can lead to rickets and osteomalacia.

Question 7

Describe the defects that occur in the metaphysis

Answer 7

Bacterial infection - osteomylitis. Abnormal osteoblasts and collagen synthesis - osteognesis imperfecta.

Question 8

Normal growth and development of bone requires

Answer 8

Calcium, phosphorus, vitamin A,C and D and a balance between growth hormones, thyroid and parathyroid hormones, oestrogens and androgens.

Question 9

Describe the normal structure of cortical bones

Answer 9

Long shafts, lamellae with haversian canals, mechanically strong, thick periosteum, slow turnover, slow blood supple and fracctures require force.

Question 10

Describe the structure of cancellous/trabecular bone

Answer 10

Ends of long bones, vertebral bodies or flatbones, meshwork of trabeculae, metabolic, thin periosteum, rapid turnover, rich blood supply, fracture as a result of compression.

Question 11

Where are the primary and secondary ossification zones?

Answer 11

Primary - diaphysis. Secondary - epiphysis

Question 12

What is a comminuted fracture?

Answer 12

A break or splinter of the bone into more than two fragments

Question 13

Define fracture and some of the descriptive factors.

Answer 13

A complete or incomplete break in bone. Descriptive factors - Site, open to surface, contamination, soft tissue injury, joint involvement, number of pieces, alignment, degree of separation.

Question 14

Name some of the typical fracture patterns

Answer 14

Question 15

Name some of the more complicated fracture patterns

Answer 15

Avulsion - Fragment of bone separated from main mass. Buckled fracture - (torus) ends of bone driven together, commonly seen in kids. Compression or wedge fracture - usually involves vertebrae. Pathological - Caused by disease. Stress - hairline crack.

Question 16

Fracture healing depends on what? How long can it take and what does this depend on?

Answer 16

Activity of osteoblasts in local periosteum. Can take 2-20 weeks and it depends on severity and age.

Question 17

Of the three main stages of fracture healing, name the first and describe it.

Answer 17

Reactive Phase - Fractire + inflammatory phase. Fibroblasts in periosteum proliferate to from granulation tissue around site.

Question 18

Of the three main stages of fracture healing, name the second and describe it.

Answer 18

Reparative phase - Callus formation (osteoblasts quickly form woven bone to bridge gap). Woven bone is weak as collagen fibres arranged irregularly. Lamellar bone laid down, collagen is organised into regular sheets to give strength

Question 19

Of the three main stages of fracture healing, name the third and describe it.

Answer 19

Remodelling phase - remodelling by osteoclasts to restore original bone

Question 20

Describe the conservative treatments

Answer 20

Treatment of simple fractures with low risk of non-union. May or may not be immobilised and use of rehabilitation.

Question 21

Describe the intervention treatment

Answer 21

Fracture with limb threat or risk on non-union. Augment natural healing with replacement or strengthening. May or may not use immobilisation and use of rehabilitation.