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- It is a progressive systemic skeletal disease characterized by normal mineralization but reduced density
- Defined by WHO as T score < -2.5 (race and sex matched young adult)
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- T score is race and sex matched, comparing to 25-35 year old adults
- Z score is race, sex and AGE matched
- Z score is useful to diagnose secondary osteoporosis
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- 68-95-99.7 (1SD-2SD-3SD)
- 2SD = 95%, 2.5SD ~98.8%
- So < -2.5SD means 0.62%
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- Primary
- Type 1 (postmenopausal) - mainly cancellous loss, higher bone turnover
- Type 2 (senile, age-related) - both cortical and cancellous loss
- Secondary – Role of the Z score → due to steroids, endocrine
- Z score is BMD relative to similar-aged patients
- If Z score < -2.0, there is risk of secondary causes ("even compared to same-age people, bone is poor")
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- It is a Fracture Risk Assessment Tool developed by University of Sheffield
- It is a score to calculate 10-year probability of fracture - hip fractures and major osteoporotic fractures (wrist, shoulder, hip, spine)
- It has a calculator considering age, alcohol consumption, femoral neck BMD, weight, height, smoking, and steroid use
- Stratifies into risk levels:
- < 10% risk per year
- 10-20%
- 20%
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- Dual Energy X-Ray Absorptiometry
- Machine that produces two different X-ray beams of different energies that are absorbed in different proportions by bone and soft tissue
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- Based on the FRAX score, it only looks at the femoral neck T score because there is more data available for this skeletal site,
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- False positive (bone density lower than it is) - Conditions that cause removal of local bone
- Laminectomy defects and lytic lesions, spina bifida
- This is why they provide the images - to look for possible false positives or negatives
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- Opportunistic screening can be done with abdominal CT scans of patients
- CT attenuation measured in Hounsfield Units (HU) is lower in osteoporosis (less bone to attenuate radiation)
- CT-attenuation values were significantly lower at all vertebral levels for patients with DXA-defined osteoporosis (P < 0.001). An L1 CT-attenuation threshold of 160 HU or less was 90% sensitive and a threshold of 110 HU was more than 90% specific for distinguishing osteoporosis from osteopenia and normal BMD.
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3736840/#:~:text=CT%2Dattenuation%20values%20were%20significantly,from%20osteopenia%20and%20normal%20BMD
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- It examines trabecular lines, dividing into 6 grades depending on which lines are not present
- Trabecular groups of the proximal Femur
- There are 5 trabecular groups
- Ward's triangle is the confluence of these groups, which is an area of weakness where fracture can propagate
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- Antiresorptive medications that inhibit osteoclastic activity, classified into nitrogenous and non-nitrogenous types
- Nitrogenous type (more common) directly inhibits osteoclastic action by blocking farnesyl pyrophosphate synthase enzymes in the mevalonate cholesterol pathway and inhibits brush border
- E.g. Alendronate (Fosamax), Risedronate (Actonel), Zoledronate (Aclasta)
- Non-nitrogenous type - induces osteoclast apoptosis
- Complications: Jaw osteonecrosis, Gastroesophageal reflux disease (GERD), Atypical femoral fractures (AFF)
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- Based on the National Osteoporosis Guidelines Group, endorsed by NICE guidelines in 2022 (https://www.nogg.org.uk/full-guideline/summary-main-recommendations)
- FRAX score shows intermediate or high fracture risk
- After osteoporotic fracture
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- Based on the National Osteoporosis Guidelines Group, endorsed by NICE guidelines in 2022 (https://www.nogg.org.uk/full-guideline/summary-main-recommendations)
- When FRAX score indicates a 10-year risk of major osteoporotic fracture >20% (BMD measurement optional) FRAX score (can exclude entering BMD levels) - if 10 year risk of major osteoporotic # > 20%
- When a person over 50 years has a minimal trauma fracture of the hip or spine in a person older than 50 years of age is presumptive of osteoporosis.
- Treatment can begin without BMD confirmation.
- For postmenopausal women over 50 starting oral steroids (>7.5mg/day prednisolone for 3+ months), begin bone protection simultaneously.
- For fractures at other sites, use BMD to guide treatment decisions.
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- National University Hospital Guidelines
- Prior to starting, check renal function, history of GERD
- There is no consensus on the duration of bisphosphonate treatment or the timing and length of drug holidays
- According to NICE NOGG guidelines (https://www.nogg.org.uk/full-guideline/summary-main-recommendations)
- Recommend a temporary treatment pause of 18 to 36 months after 5 years of oral bisphosphonates
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3707342/
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- A calcium-like element that increases bone formation while decreasing bone resorption
- Due to risks of DVT and serious allergic reactions, it is restricted to patients who cannot tolerate bisphosphonates
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- RANKL inhibitor = Denosumab (Prolia)
- Antiresorptive that binds to RANKL (receptor activator of nuclear factor-kappa B) receptor, preventing maturation of pre-osteoclasts into osteoclasts
- Once every 6 months injection
- Other Uses - multiple myeloma, GCT
- Teriparatide (Forteo) Recombinant PTH. Intermittent exposure to PTH paradoxically activates osteoblasts more than osteoclasts
- Delivery: SC 20mcg/day
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- For people more than 50 years old
- Calcium 1200 - 1500mg/day
- Vitamin D 800 - 1000IU/day
- Practical management:
- Calcium + Vitamin D 1 tablet OM
- If Vitamin D level 20-30: Add Lynae (Cholecalciferol/Vitamin D3)
- If Vitamin D < 20: Add 50,000U/week Ergocalciferol (Vitamin D2) for 8 weeks → Then 1000U Cholecalciferol → Start Bisphosphonates once Vitamin D >20
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- Evidence suggests that AFF are stress fractures.
- There is generalized suppression of bone remodeling due to bisphosphonates.
- Since remodeling normally occurs at areas developing stress fractures, this suppression impairs the intracortical repair of developing stress fractures
OSTEOMALACIA
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- Compared to Osteoporosis, there is deficiency in mineralization (NORMAL STRUCTURE/OSTEOID, ABNORMAL MINERALIZATION)
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- Etiology = vitamin D deficiency
- Primary from nutritional deficit
- Secondary to renal failure, Rickets (Vitamin D resistant/Vitamin D dependent/nutritional)
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- Osteomalacia makes bone less stiff (lower Young's modulus) and more ductile (longer plastic deformation phase)
- Osteopetrosis makes bone stiff (higher Young's modulus) and more brittle (short plastic deformation phase)
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- Varus deformity due to recurrent stress fractures and healing
- Milkman Lines, also known as Looser's zones or Pseudofractures - Wide, transverse lucencies with sclerotic borders traversing partway through a bone, usually perpendicular to the involved cortex
- (appears as AFF black line on proximal femur)
- BUT IN MEDIAL CORTEX as opposed to lateral cortex in AFF
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Do not withhold good from those to whom it is due, when it is in your power to do it. Proverbs 3:27