5 - Ageing and Metabolic Bone Conditions Flashcards
What percent of bone mass is usually lost in a year from the age of 40+?
0.7% a year
After menopause, what is the percentage of bone mass loss in women?
2-9% a year
What is a T score
number of standard deviations from the mean young (30 yr) same gender and ethnicity
What is the Z score
number of standard deviations from mean aged, same gender and ethnicity
What is osteopenia
A precursor to osteoporosis
Where do you usually measure for osteoporosis
Neck of femur
Vertebral bodies
What does the DEXA scan measure
Bone density
Osteopenia T score
-1 to -2.4
Osteoporosis T score
below -2.5
What does DEXA stand for
Dual Energy X-ray Absorptiometry
Prevalence of osteoporosis
2% at 50 years
Greater than 25% at 80 years
What bones are more susceptible to osteoporotic bone loss
Neck of femur
Vertebral bodies
High proportion of trabecular bone
What treatments are given for osteoporosis?
Calcium supplements Vitamin D supplements HRT Selective oestrogen receptor modulator Biphosphonates Denosumab Teriparatide
What is the minimum time HRT is given for
5 years
Example of a Selective Oestrogen Receptor Modulator
Raloxifene
What is the MoA of biphosphonates
Inhibitors of bone reabsorption Inhibit osteoclast activity Promote osteoclast apoptosis Increase OPG production Decrease RANKL expression
Complications of biphosphonates
Giant osteoclasts
Osteoncrosis of the jaw
Atypical fractures
What is teriparatide
A recombinant PTH
Will activate osteoblasts without activating osteoclasts
What is Denosumab + how often does it need to be given
Monoclonal antibody which binds to RANKL and prevents it’s signalling
therefore inhibits the formation of osteoclasts
Needs to be given every 6 months via subcutaneous injection
What is osteomalacia
Insufficient calcium and phosphate to mineralise bone osteoid
The bones are softer and more liable to bend or fracture
Cause of osteomalacia
Lack of vitamin D
What is rickets and why is it more deforming
Childhood osteomalacia
More deforming as in children the epiphyseal growth plate is open
What would lab results show in osteomalacia
Low serum calcium and phosphorus
High alkaline phosphatase
Why is alkaline phosphatase high in osteomalacia
Due to high osteoblast activity
What would an X-ray look like in someone with osteomalacia
Pseudofractures = unmineralised sections of bone
Areas of unmineralised bone
What is the normal level of unmineralised osteoid?
<20%
What colour is unmineralised and mineralised osteoid on biopsy
Orange - unmineralised (up to 100% in osteomalacia)
Green - mineralised
How do you treat osteomalacia
Vitamin D supplements
Increase calcium in diet
Sun or UV exposure
Calcium containing foods
Milk
Bread
Beans
Green leafy vegetables
What is Pagets disease also called
Osteitis Deformans
Percentage population with pagets
3% >50 y/o
What are the 3 stages of Pagets disease
1) Increased rate of bone resorption (large no of giant osteoclasts)
2) Compensatory phase (Increased bone formation as woven bone, accelerated deposition in a disorganised manner)
3) Burn out phase (Sclerotic) - Bone hypercellularity may deminish leaving dense pagetic bone
Hypervascular bone marrow
Irregular thickened trabeculae
Bone marrow replaced by fibrovascular CT
Which bones are most commonly affected in osteomalacia?
Pelvis Femur Vertebrae Skull Tibia
What is osteosarcoma?
A rare complication of pagets disease where a cancer forms
Where are osteosarcomas usually
Long bone
Near the knee
How do you treat osteosarcoma
Remove part of the bone
Limb amputation
How do you treat osteomalacia
Biphosphates
Calcium and vitamin D supplements
Pain management
Surgery
How long does an osteomalacia patient have to take biphosphates
Oral - 2-6 months
IV single infusion to 3 infusions
What is sclerostosis also known as
Aka van buchem syndrome
Genetics of sclerostosis
Autosomal recessive
Features of sclerostosis
Endosteal hyperostosis
Resistance to fracture
Excessive height
Pathophysiology of sclerostosis
Absence or reduced production of sclerostin
therefore osteoblasts are not inhibited
