PATHOLOGY- Bone Disorders Flashcards
What is bone?
Ridged inflexible mineralised connective tissue
What is bone mineralised by?
Calcium and phosphate salts
Why are bones important structurally and metabolically ?
Structural
1. Provides physical integrity/ support
2. Protects squishy organs
3. Allows for insertion of muscles and tendons
Metabolic
1. Provides minerals
2. Important in haematopoiesis
What minerals does bone provide
- Calcium
- Phosphorous
- Magnesium
What is haematopoiesis?
It is the formation, development and maturation of blood cells in adult bone marrow
Where does haematopoiesis occur in adults?
Bone marrow
Name the parts that make up bone
- Non cellular mineralised matrix
- Cells that maintain the matrix
What is the non cellular mineralised matrix that makes up bone made up of?
- Type I collagen- osteoid
- Calcium phosphate (calcium hydroxyapatite)
- Regulatory protein and growth factors
What is type 1 collagen in bone called?
Osteoid (extraceulluar matrix in bone)
List the cells that maintain the matrix in bone
- Osteoblasts
- Osteocytes
- Osteoclasts
Why is mineralisation critical?
The osteoid would be soft and bendy if it wasn’t mineralised
What do osteoblasts do?
They build up the bone
What is the origin of osteoblasts
Mesenchymal origin
What is the function of osteoblasts?
- They secrete osteoid
- Needed for mineralisation
What are osteocytes
Inactive osteoblasts that are trapped in the bone
What is the origin of osteoclasts
Macrophage lineage
What do osteoclasts do?
They are involved in bone resorption and remodelling
How can bone be categorised?
- Maturity type
- Location type
Name the different types of bone based on maturity
- Woven bone (immature bone)
- Lamellar bone
Describe woven bone
It is immature bone as the osteoid collagen is random
It is remodelled into lamellar bone
What causes the random osteoid formation in woven bones?
Rapid bone turnover by osteoblasts
What is woven bone remodelled into?
Lamellar bone
Where is woven bone found?
Fractures
Fetal developemt
Describe lamellar bone
Made up of parallel bands/ sheets of lamellae
Where is lamellar bone found?
Makes up the majority of normal healthy adult bone
What are the two different types of lamellar bone?
Compact/cortical bone
Cancellous/ trabecular bone
Which type of bone is stronger from woven and lamellar?
WHY?
Lamellar bone is much stronger due to regular arrangement of lamellae
Name the different types of bone based on location?
- Cortical/ compact
- Cancellous. trabecular
Describe Cortical bone
Forms hard outer shell and regular shape
It is highly organised
Follows the Haversian system
What system does cortical bone follow?
The Haversian system
What is the Haversian system
Columns of lamellar bone (v compact and dense)
Describe cancellous/ trabecular bone
Spongy non structural “filler” bone
What is found in the spaces between cancellous bone?
Bone marrow
How are the different bone types organised?
Cortical bone surrounds cancellous bone
Why is bone remodelling important?
- To maintain bone strength as your bones constantly suffer from trauma like micro fractures through the day
- To be able to release metabolites
List the stages of the bone remodelling cycle
- Activation
- Resorption
- Reversal
- Formation
How is bone remodelling activated?
By hormones or damage
What happens when bone remodelling is activated by hormones of damage>
- Osteoblasts are activated
- Cytokines are released
- Osteoclasts stick to the surface of the bone
What is the next stage after activation in the bone remodelling cycle
Resorption
What happens in the Resorption stage of the bone remodelling cycle
- Mono nuclear osteocytes that are stuck to the surface of bone secrete substances
- These substances reabsorb bone
- Create pits on the surface
- Mono nuclear osteocytes undergo apoptosis or migrate
What is the next stage after Resorption in the bone remodelling cycle
Reversal
What happens in the reversal stage of the bone remodelling cycle
Monocytes clear debris for bone formation
What is the last stage after reversal in the bone remodelling cycle
formation
What happens in the formation stage of the bone remodelling cycle
- Osteoblasts are recruited
- They secrete osteoid matrix and initiate mineralisation
- Osteoblasts sit on the new bone
- some undergo apoptosis and some are incorporated as osteocytes
What is another name for immature bones?
Woven bone
What is another name for mature bones
Lamellar bone
Compact and cancellous bone are both what type of bone?
Lamellar bone
What is osteoarthritis?
Progressive erosion of articular cartridge
Is osteoarthritis just erosion?
No it is a complex imbalance of damage and repairs
What happens in osteoarthritis
Cartilage is worn away and underlying bone is exposed
This leads to damage and the formation of cysts / osteophytes causing inflammation pain
This ultimately leads to narrowing joint space
What are osteophytes
Abnormal growth in bone
How common is osteoarthritis?
uptown 80% of over 65s have evidence of having osteoarthritis
but only 1/4 have symptoms
What are some of the symptoms of osteoarthritis
- Pain/ functional limitation
- Morning stiffness
What are some of the signs of osteoarthritis
- Crepitus (crunchy)
- Restricted movements
- Bony enlargement
- Instability/ muscle wasting
What are the differences between signs and symptoms
Signs are something you observe as a
clinical
Symptoms are things patients present with
What is a primary cause for disease?
Unknown cause or unknown origin for a disease
no underlying cause for the disease
Give some secondary causes of osteoarthritis
- Pre existing joint damage
- Metabolic disease
- Systemic disease
How do you investigate osteoarthritis
- Blood tests to make sure rheumatoid factor is negative and to look for bone markers
- X-ray will show cartilage loss, joint space narrowing and cysts
What would a raised rheumatoid factor suggests?
the patient may have rheumatoid arthritis
How do we manage osteoarthritis
- Physical: weight loss, hydrotherapy
- Medications: NSAIDS, steroids
- Surgery: joint replacement
What is rheumatoid arthritis?
It is an autoimmune disease consisting of persistent inflammation (synovitis) leading to chronic symmetrical
List the 3 factors that strongly influences the progression of rheumatoid arthritis
- Gender: women at higher risk
- Genetic: associated with human leucocyte antigen (HLA)
- Environmental: periodontal disease may contribute to it
Who is most affected by rheumatoid arthritis?
Younger (30-50)
x3 more women
rarer 1%
What does synovitis
Inflammation
What happens in rheumatoid arthritis
Citrullination of self antigens leading to loss of normal tolerance as the antigens are no longer recognised as self cells
Auto immune response occurs leading to inflammation leading to damage
What is citrullination?
Protein modification from arginine to citrulline
What are the differences between rheumatoid arthritis and osteoarthritis?
Rheumatoid arthritis is an autoimmune synovitis leading to mass formation and sticking of joins together
Osteoarthritis is just breakdown of cartridge leading to damage to bone
What is ankylosis
Abnormal stiffening/ immobility in joint due to bony fusion
How do we investigate rheumatoid arthritis
- Blood tests: bony markers present and look for anti citrullinated peptide antibodies. Can also look for rheumatoid factor
- X rays show synovitis and joint damage
How do we manage rheumatoid arthritis
Theres no cure
Can give them anti inflammatories, steroids, anti-TNF, disease modifying anti rheumatic drugs (DMARD)
What is Paget’s disease?
A disorder of bone turnover/ remodelling
What happens in paget’s disease?
Increased osteoclastic bone resorption leading to increased new bone formation
Formation happens at a faster rate than resorption but woven bone is made
What is the problem with increased formation of woven bone?
Woven bone is weaker than lamellar bone
This can leaf to deformity and increased risk of fracture
What is the aetiology of paget’s disease
Unknown aetiology
Suggested to be a combination of environmental and genetic
Mutation in osteoblast gene
How is paget’s disease presented in most people?
60-80% asymptomatic
Some present with bone pain/ joint pain or bone deformities
If Paget’s disease is mainly asymptotic how is it diagnosed?
Usually patients come in for an X-ray and the x ray shows changes
Describe how the bone in patients with Paget’s disease may look
Cotton wool like appearance (hypercementosis)
What are some of of the side effects of having Paget’s disease?
- Nerve compression leading to deafness
- Spinal stenosis
- Hydrocephalus
- Cardiac failure, myocardial hypertrophy due to increased blood flow
- Pathological fractures
- Osteosarcoma
What is hypercementosis
Excessive cementum on the roots of teeth
Name the 3 stages of paget’s disease
- Hot osteolytic phase
- Mixed phase
- Cold osteosclerotic phase
What happens in the hot osteolytic phase of Paget’s disease?
Osteoclasts are breaking down bone
What happens in the mixed phase of Paget’s disease?
Both osteoclasts and osteoblasts are working
What happens in the Cold osteosclerotic phase of Paget’s disease?
Burn out inactive phase but bone is still weak and woven
How do we treat paget’s disease?
With bisphosphonates
How do biphosphonates work?
- Inhibit osteoclasts recruitment
- Inhibit osteoclast activity
- Slow bone loss
Other than Paget’s disease what else can biphosphonates treat?
Used in osteoporosis
What is a serious side effect of using biphosphonates?
BRONJ
Bisphosphonate
Related
Osteonecrosis of
Jaw
What is osteomyelitis?
Inflammation of bone / bone marrow
What is osteomyelitis almost always due to?
Virtually always secondary to infection
How do most people develop osteomyelitis
- Haematogenous spread (through blood)
- Extension from adjacent site
- Direct implantation
What is the most common cause for children developing osteomyelitis
Haematogenous spread
What is the most common cause for adults developing osteomyelitis?
Fractures
Surgical infections
Diabetic foot
Describe the clinical presentation of osteomyelitis
- Fever
- Localised bone pain
- Overlying tenderness/ erythema
How do you diagnose osteomyelitis
- MRI / bone scan
- Blood cultures
- Bone culture and sensitivity test
How do we treat osteomyelitis
Immobilise
Antibiotics
Can drain or make excision
How common is chronic osteomyelitis
Occurs in 5-25% of cases
What is the cause of osteomyelitis of the jaw and when does it happen?
It has a poly microbial cause and is secondary to odontogenic infection
Name some different types of osteomyelitis
- Chronic osteomyelitis
- Osteomyelitis of the jaw
- Tuberculosis osteomyelitis
what is tuberculous osteomyelitis
Haematogenous spread from reactivated primary TB focus
Spine involvement = (Pott’s disease - Percival Pott )
Define fractures
Loss of bone integrity
What can fractures be caused by?
Mechanical injury and/or diminished bone strength
Give examples of different types of fractures
- Simple
- Compound
- Comminuted
- Displaced
- Stress
- Greenstick
- Pathologic
what is a simple fracture
skin intact
What is a compound fracture?
A fracture where bone is exposed
what is a comminuted fracture
fragmentation
what is a displaced fracture
misaligned ends
What is a stress fracture
A slow developing fracture due to repeated repetitive loads
What is a greenstick fracture
Partial fracture through bone
What is a pathologic fracture
Weakened bone due to existing disease
List the 3 phases of fracture healing
- Inflammatory phase
- Reparative phase
- Remodelling phase
What is another name for the reparative phase of fracture healing
Endochondral
What happens in the inflammatory phase of fracture healing
- Haematoma forms
- Macrophages, neutrophils and platelets release cytokines
- Fibroblasts and mesenchymal cells go to fracture site
- Granulation tissue forms around the fracture ends
- Neurovascularisation
- Osteoblasts, chondrocytes, fibroblasts proliferate
- Fibrosis results in callus formation
What are the benefits of a haematoma forming?
Stems blood flow from site of injury and is also a source of haemopoietic cells and growth factors
What is granulation tissue?
Vascular tissue
What does the inflammatory phase ultimately lead to the formation of?
A callus
What happens in the reparative phase of bone healing
- Primary callus forms quickly
- Cartilage provides provisional stabilisation
- Endochondral ossification converts soft callus to hard callus
Why is the reparative phase also known as the endochondral phase
As endochondral ossification converts soft callus into hard callus
What is soft callus?
Cartilage
What is hard callus
Woven bone
What happens in the remodelling phase of bone healing
- Bony callus tissue is resorbed
- Osteoblast and osteoclast remodel to bones original cortex structure
What is osteonecrosis?
Infarction of bone/marrow
What is osteonecrosis also known as?
Avascular, aseptic or ischaemic necrosis
What are most cases of osteonecrosis due to?
Alcohol
Steroids
Fractures
What is the underlying cause of ALL cases of osteonecrosis?
Vascular insufficiency through mechanical injury to blood vessels, thromboembolism, external pressure
how do you get osteonecrosis in the head and neck
BRONJ/MRONJ
traumatic injury
radiation (osteoradionecrosis)
Is osteonecrosis due to infection?
NO it is aseptic
What do patients with osteonecrosis osteoarthritis display?
Joint pain (shoulder or hip)
Can be asymptomatic
What will an MRI of osteonecrosis show?
Bone marrow oedema / plain x ray
How do we manage osteonecrosis
- Surgical decompression
- Grafts
- Joint replacement
What controls serum calcium in the body
Vitamin D
Parathyroid hormone
What is released if calcium levels are low?
Parathyroid hormone
How does the parathyroid hormone help increase low calcium levels
- Increased osteoclast bone resorption
- Increased intestinal calcium absorption
- Increased synthesis of 1,25-dihydroxyvitamin D3
- Increased renal tubular resorption Ca
- Increased renal excretion of PO4
How does vitamin D increase calcium levels?
Increases intestinal absorption of calcium which increases mineralisation of bone
What effect does serum calcium have on vitamin D?
When there is low calcium levels, there is Vitamin D induced bone resorption which then increases calcium levels
decreases bone resorption with HIGH serum calcium
what happens to calcium in vitamin d defiicnecy and what does this cause
- Vitamin D deficiency causes low Ca levels
- This increases PTH
- This increases calcium but lowers PO4
Vit D increases bone resportion with low serum calcium but does opposite with high serum calcium
What is another term for rickets
Osteomalacia
What causes rickets?
Defective mineralisation
What is rickets
Defective mineralisation of epiphyseal plate in children that can lead to weakened (bendy) bones
What is osteomalacia?
Defective mineralisation of epiphyseal plate in adults that can lead to weak bone formation during remodelling and makes the patient vulnerable to fractures
What is the aetiology of rickets/ osteomalacia
Anything that interferes with bone mineralisation Eg
- Deficient intake or absorption of vitamin D
- Defective 1alpha hydroxylation eg renal failure
- Primary renal phosphate wasting
- Inhibitors or mineralisation
- Defective vitamin D receptors
What causes vitamin D deficiency?
- Nutritional (dietary, inadequate exposure to sunlight)
- Malabsorption e.g. coeliac disease, IBD
- Vitamin D dependent rickets (VDDR) type 1 and 2
What happens in vitamin D deficiency?
- Reduced serum calcium phosphate
- Parathyroid hormone secreted causing bone to demineralise
- Increased serum calcium
- Bone is now poorly mineralised
Give some dentinal complications of rickets
- Familial hypophospataemia
- Hypoplasia
- Missing teeth
Give some signs and symptoms of Familial hypophospataemia
- Abnormally large pulp chamber
- Thin enamel
- Dentinal defects/ globular dentin
- Dentinal abscesses more common
What is hyperparathyroidism?
Anything that causes pathological increase of parathyroid hormone
What can increased parathyroid hormone lead to ?
- Increased osteoclast bone resorption
- Increased intestinal calcium absorption
- Increased synthesis of 1,25- dihydroxyvitamin D3
- Increased renal tubular resorption of calcium
- Increased renal excretion of PO4
Name the 3 types of hyperparathyroidism
- Primary: Autonomous hyperparathyroidism
- Secondary: Compensatory hyper secretion
- Tertiary: persistent hyperparathyroidism even when decreased calcium corrected
What is primary hyperparathyroidism the most common cause of?
Asymptomatic hypercalcemia
What is primary hyperparathyroidism caused by?
- Adenoma
- Hyperplasia
- Malignancy
What symptoms do patients with primary hyperparathyroidism present with?
- Bone disease/ bone pain (BONE)
- Renal stones (STONES)
- GI disturbances including constipation, nausea, peptic ulcers (GROANS)
- CNS alterations eg depression and seizures(MOANS)
What is secondary hyperparathyroidism categorised by?
Any condition that causes reduced calcium leading to increased para thyroid hormone
What is osteogenesis imperfecta also known as?
Brittle bone disease
What is osteogenesis imperfecta caused by?
Gene mutation affecting the type 1 collagen gene (osteoid)
What is osteogenesis imperfecta usually presented with?
Increased fractures (can start in utero)
List some dentinal manifestations of osteogenesis imperfecta
Dentinogeneisis imperfecta type II
Name the 2 types of ossification
- Endochondral
- Intramembranous
Which type of ossification occurs in the maxilla and mandible?
Intramembranous ossification
What is Intramembranous ossification
Deposition of bone within primitive mesenchymal tissue
What is achondroplasia due to?
FGFR3 gene mutation
What is the purpose of the FGFR 3 gene
It inhibits endochondral growth
What happens with the FGFR 3 gene undergoes gene mutation?
Can impair cartilaginous growth
What does FGFR3 stand for
Fibroblast growth factor receptor
What can patients with achondroplasia present with?
Short limbs
Normal skull/ trunk
List some craniofacial issues patients with achondroplasia may suffer from
- Macrocephaly / prominent forehead
- Flattened/ depressed nasal bridge
- Hypoplasia of midfacial structures
- Maxilarry hypoplasia
- Relative overgrowth of the mandible
- Narrowing of anterior palate, open Bute
- Orthodontic intervention