Mechanical Role of the Skeleton

Question 1

What are the functions of the skeleton

Answer 1

- Locomotion
_Lever
- Respiration
- Protection
- Calcium store
- Haematogenetic factory (houses bone marrow).

Question 2

What role does the skeleton have in calcium storage

Answer 2

98% of the body’s calcium is stored in the skeleton. Calcium is the most regulated ion in the body. A vital level needs to be maintained - cannot be too high or too low.

Question 3

What seven adaptations does the skeleton have for bipedal locomotion

Answer 3

• Spinal curves
• Shock absorption of discs
• Weight bearing axis of hip and knee
• Tripod arrangement of the foot
• Shape of the thorax
• Soleus slow muscle
• TA (tendon achilies) energy absorption.

Question 4

How is the weight bearing axis of the hip and the knee adapted for bipedal locomotion

Answer 4

The centre of mass is close to the axis of rotation of the hip.

Question 5

How is the weight bearing axis of the knee compromised in osteoarthritis

Answer 5

The end result of OA is loss of extension in the knee. This makes you need to walk with bent knees which makes walking difficult.

Question 6

How is the shape of the thorax adapted for bipedal motion

Answer 6

Vertebral bodies are positioned quite far forwards.

Question 7

How is the tendon achilies adapted to bipedal motion

Answer 7

This tendon has elastin as well as collagen which enables travelling of long distances with little energy.

Question 8

In which age groups is the skeleton most likely to fail

Answer 8

In the young and the old.

Question 9

What are the three most likely modes of failure of the skeleton

Answer 9

• Perinatal - in the young
• Trauma - in the middle aged
• Osteoarthritis/osteoporosis in the older generation.

Question 10

How can perinatal segmentation fail

Answer 10

The mesoderm either side of the midline segments into block to form vertebral bodies. This segmentation can fail and this can lead to indiscreet vertebrae or failure of proper formation leading to the creation of a wedge shaped vertebrae.

Question 11

What can failure of segmentation lead to

Answer 11

Congenital scoliosis.

Question 12

Other than failure of segmentation, what is a second perinatal mode of failure of the skeleton

Answer 12

Failure of formation.

Question 13

What are the requirements for the healing of fractures

Answer 13

Cells, growth factors and blood vessels.

Question 14

What are the initial steps involved in fracture healing

Answer 14

Blood enters the gap in the broken bone. This acts as a scaffold as it beings to clot.

Question 15

What will stop the healing and formation of new bone

Answer 15

Movement of the broken bone.

Question 16

What is the possible yield strain for granulation tissue

Answer 16

Granulation tissue can be stretched quite a lot before it becomes damaged. The yield strain is 100% so granulation tissue can be stretched to double it’s size.

Question 17

Above what yield strain will prevent healing and formation of new bone

Answer 17

Movement causing more than 2% strain on the bone will prevent formation of new bone in healing.

Question 18

How do bones need to be aligned for proper healing

Answer 18

Bones do not need to be lined up to heal however to heal properly the bone should be placed in a good position in order for the least strain on the joint.

Question 19

What is the name of the new bone that begins to form to repair fractures

Answer 19

The callus

Question 20

What is the origin of the external callus

Answer 20

The periosteum and soft tissue which contributes cells and blood vessels to the healing process.

Question 21

What is the origin of a gap callus

Answer 21

Bone marrow

Question 22

What is the origin of a direct/primary callus

Answer 22

The cortex.

Question 23

What are the two mechanisms of fracture repair

Answer 23

Indirect and direct.

Question 24

What is formed in indirect fracture healing

Answer 24

An external callus. This is new bone of a semi-rigid fixation.

Question 25

How does direct fracture repair work

Answer 25

There is no callus formation - it is an extension of remodelling.

Question 26

What type of fixation occurs in direct fracture repair

Answer 26

Rigid fixation

Question 27

What type of fixation occurs in indirect fracture repair

Answer 27

Semi-rigid fixation.

Question 28

What are two bones in the body with poor healing ability

Answer 28

The clavicle and the tibia.

Question 29

What is the callus

Answer 29

New bone

Question 30

By which method - direct or indirect - do most bones heal

Answer 30

The indirect repair process.

Question 31

Why is the callus formed in indirect fracture repair semi-rigid

Answer 31

This is so that the body knows that it is damaged and reduces movement of the bone.

Question 32

Which part of the bone composition is gives it strength

Answer 32

The organic collagenous component

Question 33

Which part of the bone gives it stiffness

Answer 33

The inorganic hydroxyapatite component.

Question 34

What is the process of direct fracture repair

Answer 34

Osteoclasts go across the crack and bone is removed before new bone is laid down. This “fools” the body into thinking it has a giant microcrack therefore the healing process is just an extension of bone remodelling.

Question 35

What is the name of an infectious condition that can affect growth plates and therefore growth in children

Answer 35

Osteomyelitis.

Question 36

What is mechanotransduction

Answer 36

The sensing of a mechanical stimulus and conversion of this to a biological response. Bone cells must receive signals from movement of the bones in order to work.

Question 37

What are the possible consequences of treatment

Answer 37

Treatment can take up to two years and more. This can have a huge impact on the patients life in terms of independence and earning, as well as pain, muscle weakness etc.

Question 38

What is the big disadvantage of OP fractures in older people

Answer 38

Loss of independence which many people do not recover.