Bone pathology 7/11/22 Flashcards
Bone cells, types and function
The osteogenic cells are located in the periosteum; these are where the osteoblasts and osteoclasts form.
Osteoblasts are responsible for producing collagen. They are very active in the growing skeleton and in the mature skeleton. They are also activated when a fracture occurs. Osteoblasts form the bone tissues we will look at next, as they mature, they become osteocytes.
Osteoclasts help with remodelling. The reabsorb the bone matrix; which is especially useful following a fracture.
What is the Periosteum?
The periosteum is a membrane of specialised connective tissue that covers the surface of bones
Has an outer fibrous layer and an inner cellular layer
It has collagen fibres which support the bone and connect it to surrounding structures
Osteogenic cells in the periosteum are used in the growth and repair of bones.
Examples of periosteal reactions? Uninterrupted
Periosteal Reactions
Uninterrupted Periosteal Reactions
(usually benign)
Example would be with fracture healing
Solid buttress
Solid longitudinal
Solid undulated
Examples of periosteal reactions? Interrupted Periosteal Reactions
Interrupted Periosteal Reactions
(Malignant or Aggressive Non-Malignant Process)
Sunburst
Perpendicular (Velvet)
Lamellated (onion skin)
Codman Triangle
Rate of Growth and Periosteal Reactions?
With slow-growing processes, the periosteum has time to respond and so it produces new bone at the same speed as the lesion is growing. This enables us to see a solid, uninterrupted margin of new bone.
With rapid-growing processes, the periosteum can’t keep up with the rate the lesion is growing at so we see an interrupted pattern of new bone growth.
Lesion Growth and Type of Reaction -Lamellation explain?
If the lesion grows in steps (e.g. intermittently);
The periosteum may have time to lay down a thin layer before the lesion grows again
Here we see an onion peel type effect
This is known as Lamellation
Lesion Growth and Type of Reaction- Sunburst sign explain?
If the lesion grows at a rapid rate consistently (fast but steady growth);
The Sharpey’s Fibres connecting the periosteum to the bone become stretched and ossify to look like small hairs
This is known as a Sunburst Reaction or Sunburst Sign
Lesion Growth and Type of Reaction- Codman Triangle explain?
If the lesion grows very quickly;
Only the leading edge of the periosteum ossifies
This is sometimes seen in the “transition zone” between normal and abnormal bone
Zone of transition types
3 types
clear sclerotic border
Clear non sclerotic border
No border
Border between the lesion and normal bone
ZOT is said to be narrow if a line can be drawn around the border of a lesion
If undetectable, it is said to be wide
If a lesion has a sclerotic border, it has a narrow zone of transition.
Types of bone cysts?
Simple Bone Cysts
Aneurysmal Bone Cysts
Subchondral Cysts
Simple Bone Cysts information
Common, benign fluid filled lesion usually in metaphysis
Cause unknown – could be due to blocked interstitial drainage in a rapidly growing area
Cortex expands but periosteum is intact over thin cortical shell
Cyst contains clear serous fluid
Fibrous septa can form which can lead to a multilocular appearance
Half of all SBC’s lead to #
More frequent in boys 4 – 10 years
Early cysts lie in metaphysis of proximal humerus or femur
Symmetrical bone expansion
Thinning of cortex can lead to fracture.
Lucency with thin sclerotic rim
Aneurysmal Bone Cysts information
Osteolytic
Rapidly grows and expands
Stabilises to form bony shell and septa to give a trabeculated appearance like soap bubbles
Finally ossifies to an irregular, dense bony mass
Females generally 10 – 30 years (peak at 16)
Upper and lower extremeties more common
Radiographs good – CT for when lesions in axial skeleton therefore harder to define
Benign vascular lesion but secondary to preceding benign or malignant lesions.
Cavity filled with blood
Typical sites – vertebrae and long bones common but anywhere!
< 20 years typical
Expansile thin walled cystic lesion which is blood filled
Trauma is an initiating factor or if there is a arteriovenous fistula (reactive vascular lesion)
Often occurs in abnormal bone (existing tumour benign or malignant) which causes haemodynamic changes leading to ABC
What does Osteolytic mean?
Osteolysis is a progressive condition where bone tissue is destroyed. In this process, bones lose minerals (mostly calcium), softens, degenerates and become weaker
Subchondral Cysts information
A cyst occurring close to a joint and beneath the cartilage around a joint
Pockets of synovial fluid in bone
Due to pressure or stress on articular cartilage and subchondral bone which leads to synovial fluid leaking through weak areas of cartilage and into bone. Associated with OA.
Lytic appearance
Characteristic feature of OA
What does lesion mean?
Remember “lesion” doesn’t necessarily mean “cancer”. It simply means an abnormal growth of cells and can be caused by a number of things and can also be benign.
