Fracture and Bone Healing

Question 1

In relation to bone what is meant by stress and strain?

Answer 1

• stress is the force per unit area

* strain is the degree of deformation (worked as a percentage of change of length /original length)

Question 2

What is meant by centrifugal and centripetal blood supply?

Answer 2

Centrifugal blood supply is out to in.

Centripetal blood supply is in to out.

Question 3

Blood supply to the head of the femur is poor because blood supply has to come from the neck as the head is covered with avascular cartilage.

Answer 3

Understood.

Question 4

What are bones with a poor blood supply?

Answer 4

Navicular
Talus
Head of the femur
Scaphoid 
Humeral head

Question 5

Blood supply to the scaphoid

Answer 5

The major blood supply to the scaphoid is via the radial artery.

Question 6

Primary bone healing

Answer 6

Remodelling

Question 7

Secondary bone healing

Answer 7

Intramembranous ossification and endochondral ossification to form woven bone.

Question 8

Intramembranous ossification occurs from

Answer 8

mesenchyme (forms from the osteoblast)

Question 9

Endochondral ossification occurs from

Answer 9

cartilage

Question 10

What is needed for primary bone healing to occur?

Answer 10

Absolute stability - 0 strain on the bone.

Question 11

What are the steps of secondary bone healing following a fracture?

Answer 11

1. Clotting cascade forming a haematoma to prevent blood loss.
2. Neutrophils gather at the site of injury - attracted by the dead cells and debris. Neutrophils secrete chemokines and IL-6.
3. Macrophages enter present on the endosteal and periosteal surfaces are involved in intramembranous bone formation. Inflammatory macrophages recruited to the site of injury are involved in endochondral ossification. Produce cytokines.
4. Fibroblasts enter and lay down ECM.
5. Angiogenesis - new blood supply - most important part of bone healing.

Question 12

Which type of ossification forms the major part of secondary bone healing?

Answer 12

Endochondral ossification.

Question 13

Perrens strain theory

Answer 13

The strain dictates the tissue formed in bone healing.
Bone formed at lowest strain.
Fibro-cartilage formed in some strain.
Fibrous connective tissue formed in highest strain.

Question 14

Once fracture ends are linked by a soft callus what happens next?

Answer 14

• Once fracture ends linked by soft callus, hard calus stage starts
• Osteoblasts lay down woven bone at periphery (from
periosteum) - intramembranous ossification
• Chondroid matrix calcifies, new woven bone is laid down - endochondral ossification.

Question 15

H A E M summary of bone healing?

Answer 15

• H aematoma - platelets stop bleeding
• A cute inflamation - neutrophils then macrophages
• E arly (soft) callus - fibroblasts and chondroid tissue
• M ature (hard) callus - ossifying chondroid tissue
(endochondral ossification) and intramembranous
ossification from periosteum.

Question 16

How does site of fracture change the treatment?

Answer 16

Example fracture neck of femur - poor blood supply so needs more aggressive management such as hip replacement.
- hip replacement ideal for elderly patients as they can then mobilise quicker.

Question 17

How does a scaphoid fracture present?

Answer 17

A scaphoid fracture is a break of the scaphoid bone in the wrist. Symptoms generally includes pain at the base of the thumb which is worse with use of the hand.

Question 18

Why are scaphoid fractures serious?

Answer 18

The Scaphoid receives its blood supply primarily from lateral and distal branches of the radial artery. Blood flows from the top/distal end of the bone in a retrograde fashion down to the proximal pole; if this blood flow is disrupted by a fracture, the bone may not heal.

Question 19

Scaphoid fracture treatment.

Answer 19

There are two general approaches for treatment of a scaphoid fracture: cast immobilisation or surgical stabilisation. As long as the scaphoid fracture is not displaced (out of position), cast immobilisation is a very reasonable treatment. The cast must extend over your thumb to limit the mobility of your thumb.

Question 20

Monteggia fracture

Answer 20

Proximal ulna fracture with radial head dislocation.

Question 21

Galeazzi fracture

Answer 21

Radial shaft fracture - with radio ulnar joint disruption.

Question 22

Hume fracture

Answer 22

Olecranon fracture with radial head dislocation (paeds)

Question 23

Hemiarthroplasty vs total hip replacement

Answer 23

Hemiarthroplasty done in less fit patients that may not be able to cope with total hip replacement.

Question 24

When would you x-ray an ankle?

Answer 24

Pain around the medial malleolus / over the navicular bone. Posterior edge of the medial malleous.

Ottawa ankle rules:
Weight bearing: Able to immediately after the injury?
Able to currently?

Establish no vascular or neural compromise.