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.
Information on benign bone lesions and examples
Normally solitary
Localised and slow-growing
E.g. Osteoma, Osteochondroma, Aneurysmal Bone Cyst, Fibrous Dysplasia
information on malignant bone lesions and examples
May spread
More diffuse and can be fast-growing
E.g. Osteosarcoma, Chondrosarcoma, Ewings Sarcoma, Multiple Myeloma
What is a neoplasm?
An abnormal mass of tissue that forms when cells grow and divide more than they should or do not die when they should. Neoplasms may be benign (not cancer) or malignant (cancer).
Examples of bone lesions?
Osteoid Osteoma (OO)
Osteochondroma
Osteosarcoma
Ewing’s Sarcoma
Osteoid Osteoma (OO) information
Benign bone lesions
Can be visible on X-ray but usually require CT/MRI for treatment planning
Can be painful even though they are benign – typically at night
Typically have a visible “nidus”
The “nidus” typically forms the centre of the growth process and contains a mix of blood vessel, mixed bone and osteoblasts&osteoclasts.
It is surrounded areas of sclerosis.
Osteochondroma information
Also benign
Arise from overgrowth of bone and cartilage
Sometimes considered a developmental abnormality
Can be genetic classed as “hereditary multiple osteochondromas” (HMO)
Develop in childhood but remain into adulthood.
Bone grows in projections and theoretically can happen anywhere but more common in areas where bone has formed from cartilage (such as the joints). They are covered in a layer of cartilage.
Osteosarcoma information
Note the “sunburst” periosteal reaction. This is typical of OS but not exclusive to it.
Malignant bone primary.
Usually requires surgical excision.
Ewing’s Sarcoma information
Rare form of bone cancer
Occurs in children and young adults.
Malignant and can spread.
Classifications of bone lesions? what do they depend on
Age of the Skeleton
Mets most common over age of 45, primary malignant tumours are rare in under 5s
Number of lesions
Benign lesions are solitary, malignant can spread
Site of the lesion
Some tumours are only found at particular sites, e.g. simple bone cyst at proximal humerus, chondromas in the hands and feet
Also are they centrally located to the bone?
Bone destruction
Cortical bone is destroyed more slowly than trabecular bone but will show earlier on imaging as we recognise a change in its normally homogenous density sooner
Loss of 70% of bone mineralisation before changes are seen in trabecular bone
Periosteal Reaction
Borders of the lesion
Is it intercellular? Or is there a wide zone of transition – undefined edges?
Order of bone on inmature skeleton
Epiphysis
Physis (growth plate)
metaphysis
diaphysis
Order of bone on mature skeleton
Articular surface
Epiphyseal scar
Diaphysis
Descriptive terminology-Eccentric or Central
Is lesion in the centre of the bone or on the periphery?
Descriptive Terminology- Expansile or non expansile
Is lesion contained within the normal confines of the bone or has it enlarged the bone width?
Can be benign or malignant though more commonly malignant lesions that grow the periosteal confines
Descriptive Terminology- Lytic or Sclerotic
Lytic lesions appear less dense than surrounding bone
Sclerotic lesions appear more dense than surrounding bone
Common bone pathologies
Osteomyelitis
Avascular Necrosis (AVN)
Pathological Fractures
Multiple Myeloma
Osteogenesis Imperfecta
Osteomalacia
Osteoporosis
Pagets Disease of Bone
Osteomyelitis
Bone infection
Infection impedes blood flow = bone death (necrosis)
Bony matrix is destroyed
Usually as a result of:
Fracture
Infection elsewhere in the body
Surgery (especially with prosthesis)
Treatment involves:
Surgical debridement (removal of dead bone)
IV antibiotics
Antibiotic beads inserted into cavity.
Avascular Necrosis (AVN)
Cell death due to interrupted blood supply
Can be caused by:
Infection (as just seen)
Chronic steroid use
HIV
Diabetes
Trauma
Most commonly seen in the head and neck of femur
Idiopathic AVN of the hip is also known as “Legg-Calvé-Perthes” disease or “Perthes” for short.
Pathological Fractures
Fractures that occur through areas of bone that harbour pathology.
The indwelling pathology weakens the bone making it more prone to fracture.
Common pathological fractures presentations:
In areas of bone infection
Through tumours
Through bony metastases
In osteoporosis
In osteomalacia
Other bony diseases like Paget’s and OI
Multiple Myeloma
Cancer of plasma cells found in bone marrow
Typically occurs in the spine, skull and ribs but can occur anywhere.
Imaged using whole body MRI or whole body low-dose CT.
X-ray “skeletal surveys” used if CT/MRI not possible.
Osteogenesis Imperfecta
Also known as Brittle Bone Disease
Gene defect
A result of a collagen deficiency (a type of connective tissue)
Bones do not develop and form as they should
Weaker, thinner and more fragile bones
Deformities may occur
Osteomalacia
Adult form of Rickets
Due to low vitamin D in the diet
Could also be low calcium or phosphorus
Causes an overall decrease in bone density
Narrow bands of decalcification
Osteoporosis
Deficiency in the bone due to a reduction in bone formation
Bones are more likely to fracture
Cause’s:
Lack of vitamin C
Old age
Reduced oestrogen levels
Pagets Disease of Bone
Disorder of bone renewal and remodelling
Osteoclasts are larger and more active than usual
Osteoblasts respond by building more bone than needed.
Can lead to pain and deformity.
Limbs can curve causing mobility issues.
Prone to fracture.
