Osteology Flashcards
Explain cessation of bone growth
- Growth in height ceases at the end of puberty
- Sex steroids stimulate growth spurt but promotes closure of epiphyseal plates
- Growth in length ceases, cell proliferation slows and plate thins
- Plate is invaded by blood vessels, epiphyseal and diaphyseal vessels unite
- May leave a line visible on X-rays
Give some examples of bones with one ossification centre
- Carpals
- Tarsals
- Ear ossicles
How many ossification centres do most bones have?
2+
How many ossifications centres does the head of the humerus have?
3
Describe the 1st zone of the epiphyseal plate
Resting (quiescent) zone
Describe the 2nd zone of the epiphyseal plate
- Growth (proliferation) zone
- Cartilage cells undergo mitosis
Describe the 3rd zone of the epiphyseal plate
- Hypertrophic zone
- Older cartilage cells enlarge
Describe the 4th zone of the epiphyseal plate
- Calcification zone
- Matrix becomes calcified; cartilage cells die; matrix begins deteriorating
Describe the 5th zone of the epiphyseal plate
- Ossification (osteogenic) zone
- New bone formation is occurring
What does normal bone growth and development require?
- Calcium
- Phosphorus
- Vitamins A, C and D
- Balance between growth hormone, thyroid and parathyroid hormones, oestrogen and androgens
Describe the cortical/compact bone
- 80% of bone
- Location: shafts of long bones
- Structure: concentrically arranged lamellae - haversian systems
- Function: mechanically strong
- Periosteum: thick
- Turnover: slow
- Blood supply: slow
- Fracture patterns: direct or indirect violence may result in deficits at the fracture site leading to non-union
Describe the cancellous/trabecular bone
- 20% of bone
- Location: ends of long bones, vertebral bodies, flat bones
- Structure: meshwork of trabeculae with intercommunicating space
- Function: metabolic
- Periosteum: thin
- Turnover: rapid
- Blood supply: rich
- Fracture patterns: honeycomb structure fails as the result of compression
Define a fracture
A complete or incomplete break in a bone
What are ways of describing a fracture?
- Site
- Open to surface
- Contaminated
- Associated soft tissue injury
- Joint involvement
- Number of pieces
- Alignment
- Degree of separation
What are some fracture patterns?
- Transverse
- Linear
- Oblique non-displaced
- Oblique displaced
- Spiral
- Greenstick
- Comminuted
Describe the bone remodelling units
- Consists of osteoclasts and osteoblasts
- Keep adult bone mass relatively constant in the face of developmental, physiological and physical demands
What are the three major phases of fracture healing?
- Reactive phase
- Reparative phase
- Remodelling phase
Describe the reactive phase of fracture healing
- Fracture and inflammatory phase (haematoma)
- Fibroblasts in the periosteum proliferate to form granulation tissue around the fracture site
Describe the reparative phase of fracture healing
- Callus formation - osteoblasts quickly form woven bone, to bridge the gap
- Woven bone is weak as the collagen fibres are arranged irregularly
- Lamellar bone laid down - collagen organised in regular sheets to give strength and resilience
Describe the remodelling phase of fracture healing
-Remodelling by osteoclasts to restore original bone shape
What are the two types of treatment of fractured bone?
- Conservative
- Intervention
What is conservative treatment?
- Simple fracture with low risk of non-union
- Dependent on natural healing process
- +/- immobilisation
- Rehabilitation
What is intervention treatment?
- Fractures with limb threat or risk of non union
- Augment natural healing with replacement or strengthening
- +/-immobilisation
- Rehabilitation
Describe septic arthritis
- Hot swollen joint(s)
- All ages can be affected but septic arthritis is more common in elderly people and very young children
- Delayed treatment can lead to irreversible damage
- Case-fatality approximately 11-50%
- Resistance to conventional antibiotics is increasing
What are four ways to determine septic arthritis?
- Isolation of a pathogenic organism from an affected joint
- Isolation of a pathogenic organism from another source in the context of a hot red joint suspicious of sepsis
- Typical clinical features and turbid joint fluid in the presence of previous antibiotic treatment
- Post-mortem or pathological features suspicious of septic arthritis
What are some conditions that predispose septic arthritis?
- Rheumatoid arthritis or osteoarthritis
- Joint prosthesis
- Intravenous drug abuse
- Alcoholism
- Diabetes
- Previous intra-articular corticosteroid injection
- Cutaneous ulcers
What is osteomyelitis?
Inflammation of the bone and bone marrow usually caused by pyogenic bacteria, and rarely by mycobacteria or fungi
How can bones become infected?
- Haematogenous spread
- Local spread (from septic arthritis
- Compound fracture (open)
- Foreign body
Describe haematogenous spread to bones
- Usually asymptomatic
- Skin sepsis may be present but is usually absent
- Organisms settle in growing metaphysis near growth plate
What are some signs of osteomyelitis?
- Painful swollen site
- Fever
- Reduced movement
- Paraplegia
Describe osteoprogenitor cells
Stem cell population, give rise to osteoblasts
Describe osteoblasts
Responsible for bone formation, cover the surface of bone
Describe osteocytes
Mature bone cells - embedded in lacunae, relatively inactive. Maintain bone matrix through cell to cell communication and influence bone remodelling
Describe osteoclasts
Multinucleated, derived from haematopoietic cells. In response to mechanical stress and physiological demands they resorb bone matrix by demineralization
What are the two main types of osteoporosis?
Type 1 - post menopausal
Type 2 - age related in those over 75 years
Describe post menopausal osteoporosis
- Affects mainly cancellous bone
- Vertebral and distal radius fracture is common
- Related to loss of oestrogen
- F:M = 6:1
Describe age related osteoporosis in those over 75 years
- Affects cancellous and cortical bone
- It is related to poor calcium absorption
- Hip and pelvic fractures common
What are clinical consequences of osteoporosis?
Increase in bone fragility. Susceptibility to fracture: micro or fragility fracture
Describe a fragility fracture
- Low energy trauma
- Mechanical forces that would not ordinarily cause fracture
- WHO gives example of fall from a standing height or less
Describe a fragility fracture
- Low energy trauma
- Mechanical forces that would not ordinarily cause fracture
- WHO gives example of fall from a standing height or less
What are some non-modifiable risk factors for osteoporosis?
- Biological sex
- Age
- Previous fracture
- Family history
- Race
What are some modifiable risk factors for osteoporosis?
- Oestrogen deficiency
- Smoking
- Alcohol
- Low calcium
- Low BMI
- Vitamin D deficiency
- Inactivity
What drugs can be risk factors for osteoporosis?
- Chronic corticosteroid therapy
- Excessive thyroid therapy
- Gonadotrophin releasing hormone agonist or antagonist
- Anticoagulants
- Anticonvulsants
- Chemotherapy
What are some pharmacological treatments of osteoporosis?
- Bisphosphonates: e.g alendronate, risedronate - disrupt the activity of osteoclasts - side effects: GI upset, oesophagitis, mandibular necrosis
- Anabolic agents - e.g intermittent parathyroid hormone (PTH)
- Selective estrogen receptor modulators (SERMs) - e.g raloxifene
- Ca2+ supplement
- Hormone replacement therapy - carries an increased risk of breast cancer
What are some non-pharmacological interventions for osteoporosis?
- Exercise - weight-bearing exercise with impact - muscle-strengthening exercise
- Nutrition - not just calcium and vitamin D, needs a balanced and healthy diet
- Vitamin D and calcium intake - sunlight, food, supplements
- Reduce alcohol/cigarettes
