6 - Fractures Flashcards
List the 3 cell types involved in the maintenance and remodelling of bone.
- Osteoblasts
- Osteoclasts
- Osteocytes
What is osteomalacia?
Softening of the bone; caused by INSUFFICIENT MINERALIZATION
List 3 medical conditions associated with low trauma fractures.
- Osteoporosis
- Osteopenia
- Cancer
What type of collagen would you find in reticular fibres?
Type III
Remember: THREE is in reTHREEcular fibres
List 4 pharmacological treatments for osteoporosis.
- Bisphosphonates
- Calcium supplements
- Vitamin D supplements
- Hormone replacement therapy (in younger women)
What is the impact of steroids on bone cells?
INHIBIT OSTEOBLASTS
What type of connective tissue forms bone?
Dense connective tissue
Where does vitamin D come from?
- Sun exposure (70%)
2. Diet (30%)
List 2 activities signalled by calcium ions.
- Muscle contraction
2. Cellular secretion
What type of collagen would you find in bone?
Type I
Remember: ONE is in bONE
What is the major protein of bone?
Type I collagen
What does the T-score indicate?
Number of standard deviations above or below mean bone density for a healthy 30-year-old
What type of bone cells break down matrix and release minerals?
Osteoclasts
Which cells produce collagen?
Fibroblasts
Compact bone tissue organizes in concentric layers called ___ to form osteons.
Lamellae
What percentage of bone is replaced each year?
10%
Why is old age a risk factor for osteoporosis?
Bone mass declines with age
What is kyphosis?
Outward curvature of the upper back
Remember: Hunchback of Notre Dame
Compare the cartilage and bone changes in osteoarthritis.
Cartilage: thins and cracks
Bone: rubs against bone; may form osteophytes
Why is collagen abundant in connective tissue, bone, cartilage, tendons, etc.?
Provides strength
Which hormone stimulates osteoclast activity?
PTH
How does PTH raise blood calcium?
Stimulates osteoclast activity
Where would you find type IV collagen?
Basal lamina
Remember: FOUR is in the FLOOR
Compare a primary and secondary tumor.
Primary: at site of origin
Secondary: travelled from site of origin
How does a dramatic dip in estrogen hormones affect bone homeostasis in postmenopausal women?
Causes the amount of bone broken down by osteoclasts to exceed the amount of bone formed by osteoblasts
What is osteopenia?
Early stage bone density loss; precursor to osteoporosis
What causes calcium stones?
High calcium levels in the urine
What is the most common site of osteoporosis-related fracture?
Spine
What type of connective tissue forms bone?
Dense connective tissue
List 2 methods of identifying those at risk of osteoporosis.
- Presence of risk factors
2. DEXA scan (bone density screening)
At what age is peak bone mass reached?
25-30
You are performing a thyroidectomy. Why is it important to leave the parathyroid gland behind when the thyroid gland is removed?
Thyroid hormones are replaceable, but it is difficult to manage lost PTH
Bone is made up of calcium salts (mainly calcium hydroxyapatite) embedded in a(n) ___.
ECM
Compare a normal fracture and a pathological fracture.
Normal: huge force applied to normal bone
Pathological: small force applied to weakened bone
Describe how menopause increases risk of osteoporosis.
Low estrogen ->
Decrease in osteoblast activity +
Increase in osteoclast activity ->
Net bone loss
A patient has poor calcium and vitamin D intake early in life. How will this increase their risk of developing osteoporosis down the line?
Reduced peak bone density makes it easier for bone to wear down with age
What are the 4 stages of bone remodelling?
- Hematoma (blood clot)
- Fibrocartilaginous callus formation (fibres and cartilage)
- Bony callus formation (spongy bone)
- Remodelling (compact bone)
Why is spongy (a.k.a. trabecular) bone more susceptible to fractures from osteoporosis?
Osteoporosis weakens trabeculae
You suspect septic arthritis and decide to aspirate the joint in question. What features of the aspirate would support your diagnosis?
Pus
When is osteoporosis usually detected? (Hint: unfortunate timing.)
After first fracture
When does bone remodelling occur?
All times; process is constant
Where is collagen found in the bone?
ECM
How does the molecular structure of collagen relate to its mechanical strength?
Secondary structure of collagen is a triple helix
Compare the efficacy of hormone replacement as a treatment for osteoporosis in younger females vs. older females.
Younger: favourable
Older: unfavourable as it increases risk of HEART DISEASE
What are the 3 R’s of fracture treatment?
- Reduction (place bone in normal position)
- Retention (retain reduced position until bone has healed)
- Rehabilitation (restore previous function)
How does osteoporosis increase risk of bone fracture?
Deteriorates trabeculae, weakening the bone
Which component gives the ECM of bone its strength?
Type I collagen
How does the body compensate for insufficient levels of calcium ingestion or absorption?
Breaks down bone to increase blood calcium
What part of cancellous bone is broken down in osteoporosis?
Trabeculae
What type of collagen would you find in bone?
Type I
Remember: ONE is in bONE
Which component of bone ECM mediates the deposition of minerals?
Glycoproteins
Why is osteoarthritis more likely to develop in the hand than in the shoulder?
Joints in hand have more repetitive movements
Where is most calcium stored?
Bone
In broad terms, what characterizes osteoporosis?
Reduced bone mass
What is osteomalacia called in childhood?
Rickets
What is the hallmark sign of tetany?
Muscle spasms
What type of bone is most commonly broken down in osteoporosis?
Spongy bone
Which vitamin aids in the absorption of calcium?
Vitamin D
Which hormone controls blood calcium?
Parathyroid hormone (PTH)
How does osteoporosis lead to kyphosis?
Vertebral collapse causes spinal curvature
Why does women’s bone mass dip sharply at menopause while men’s declines gradually?
Gonadal hormones build bone mass; estrogen levels plummet at menopause while testosterone levels decline gradually
List 2 reasons why arthritis would develop after an injury or fracture.
- DAMAGE to the articular surface
2. Disturbed BALANCE of bone turnover
Which population do T-scores apply to?
Post-menopausal women and older men
What is the effect of low levels of gonadal hormones on peak bone density?
Lower peak bone density
What type of collagen would you find in hyaline and elastic cartilage?
Type II
Remember: TWO is in carTWOlage
List 8 risk factors for osteoporosis.
- Old age
- Female
- Estrogen deficiency (e.g., menopause)
- Hypogonadism
- Long term steroid treatment
- Diet (poor calcium or Vitamin D)
- Immobility
- Family history
List 12 parameters used by the FRAX tool.
- Age
- Sex
- Weight
- Height
- Previous fracture?
- Hip fracture in the subject’s mother or father?
- Smoking?
- Glucocorticoid treatment?
- Rheumatoid arthritis?
- Presence of disease strongly associated with osteoporosis?
- Alcohol > 3 units/day?
- Femoral neck BMD
How is bone able to resist fracture?
Balance between its flexibility and rigidity; lamellae are usually able to “slip” relative to each other to disperse forces
Steroid drugs are analogues of ___ from the adrenal cortex.
Glucocorticoids
What are the 4 most common sites of injury for patients with osteoporosis?
- Wrist (Colles’ fracture)
- Spine (vertebral collapse)
- Hips
- Ribs
What procedure would confirm gout, and what would you look for?
Joint aspiration to check for urate crystals
Why is the 1st MTP joint the most common site of osteoarthritis in the foot?
Under most strain due to a) weight-bearing and b) repetitive movements during walking
Which fracture has the most serious consequences?
Hip
What is the major protein of bone?
Type I collagen
The FRAX tool combines clinical risk factors and bone density at the femoral neck to calculate the ___ year probability of bone fracture.
10
List 2 synonyms for spongy bone.
- Cancellous bone
2. Trabecular bone
List 5 conditions that would cause low bone mineral density.
- Osteoporosis
- Hyperparathyroidism
- Vitamin D deficiency
- Rheumatoid arthritis
- Chronic kidney disease
Which class of drugs inhibit osteoclast activity?
Bisphosphonates
List 2 impacts of estrogen and testosterone (i.e., gonadal hormones) on bone activity.
- Stimulate osteoblast activity
2. Inhibit osteoclast activity
What would differentiate a fragility fracture from a normal fracture?
Low impact
Where would you find type VII collagen?
Anchoring the basement membrane to underlying connective tissue
Compare a primary and secondary tumor.
Primary: at site of origin
Secondary: travelled from site of origin
List 2 proteins found in the ECM of bone.
- Type I collagen
2. Glycoproteins
Why might you refrain from operating on an osteoporosis patient with a bone injury?
Bone could be too weak to withstand stress of surgery
Why do women reach a lower peak bone density?
Testosterone builds more bone mass than estrogen
In broad terms, what determines bone mass?
Balance between osteoblast and osteoclast activity
Compare a Colles’ fracture and a Smith’s fracture.
Colles’: fractured wrist with hand pointing OUTWARDS
Smith’s: fractured wrist with hand pointing INWARDS
List 5 evidence-based recommendations for preventing falls in the elderly.
- Training for STRENGTH and BALANCE (e.g., Tai Chi)
- Medication review (i.e., eliminate side effects)
- Diet (i.e., increase calcium and vitamin D)
- Home hazard assessment
- Safety education
What is the cause of tetany?
Low blood calcium
Increased hydroxylation of proline and lysine strengthens collagen’s triple helix via H bonds. However, the stability of the final collagen fibre is reduced. Why?
Formation of covalent cross-links requires free lysine residues; increased hydroxylation prevents these bonds from being formed
What is the basic unit of compact bone?
Osteons
Compare intra-cellular and extra-cellular calcium concentration.
Intra-cellular: lower
Extra-cellular: higher
List 2 components of calcium hydroxyapatite.
- Calcium
2. Phosphate
You are a GP. A patient presents with septic arthritis. What is the next step in management?
Administer antibiotics and admit patient to the hospital
What is the WHO definition of osteoporosis?
T-score of -2.5 or lower
What would be the first investigation in a patient with a suspected low trauma fracture?
X-ray
What is the most common bone disease?
Osteoporosis
List 5 conditions that would cause low bone mineral density.
- Osteoporosis
- Hyperparathyroidism
- Vitamin D deficiency
- Rheumatoid arthritis
- Chronic kidney disease
How does immobility increase risk of osteoporosis?
Bones need stress to remodel; no stress causes osteoblast activity < osteoclast activity
Remember: use them or lose them
Corticosteroids increase risk of contracting which joint disease?
Osteoporosis
What type of bone cells secrete matrix and facilitate mineralisation?
Osteoblasts
What is the term used to describe a joint infection?
Septic arthritis
What is the T-score range in osteopenia?
-1 to -2.5
Which 2 areas are common sites for DEXA (bone density) scans?
- Lumbar spine
2. Femoral neck
What are the two main estrogen hormones in humans?
- Estriol
2. Estradiol
