Bone Remodelling

Normal Bone remodelling system

Osteoporosis

Key Players

Osteoclasts: Resposible for bone resorption

Osteoblasts: Resposible for synthesis and mineralization of bone

Osteocytes: Bone cells formed with osteoblasts become embedded in matrix

Remodelling Process

Resting Stage -> Resorption -> Reversal phase with osteoblasts -> Formation -> remodelling complete

Definition

Characterized by compromised bone strength leading to enhance bone fragility and increase risk in fracture

Tests for Osteoporosis

low eight (<51 kg), tooth count <20, rib-pelvis <2 finger breadths, wall-occiput distance >0 cm, humped back

Dexa can measure bone mineral density

Risk factors

Previous fracture, glucocorticoids, >2 falls iin last year, fractured him, low BMI, smoking, alcohol, vertebral fracture

Indications for testing

70 years of age, 65-69 with 1 risk factor, 50-64 with previous fracture or >2 risk fractures

Previous hip/spine fracutre, >2 fracture events

BMD test Interpretation

T score # of SDs from average person at peak bone mass

Z score: # of SDs compared to average person of same gender, age, race

Diagnostic Critea

Normal: T score >-1

Osteopenia: T score between -1 and -2.5

Osteroporotos T score <-2.5

Severe Osteoporosis: T score <-2.5 with Hx of fragility fractures

Types

Priamry Osteoporosis

Type 1: Loss of trabecular bone

Type 2: Predominantly cortical bone loss

Secondary Osteoporosis

Specific clinical disorders that cause low bone mineal ensity

Idiopathic juvenille osteoporosis

Transient that affects previously healthy 87-14 year olds

Tests

Calcium, albumin, CBC, creatinine, ALP, TSH, SPEP, 25-OH

Fracture Risk Assessment

CAROC

Age, Sex, Femoral neck T-Score

Increase to higher category if: Fragility fracture after 40 or >3 mos of high dose glucocorticoid

FRAX

2nd osteoporosis

Type 1 diabetes, untreated hyperthyroidism, hypogonadism, chornic malnutrition, malabsotrption, chronic liver disease

Typical Osteoporotic Fractures

Clkinical vertebral fractures, hip fracture, wrist fractures, proximal humerus fracture

Pharmacotherapy

Indications

Suggest: 10 yr fracture risk 15-19.99%, T score <2.5 and age <70, and if not started reassess in 5 year if 10 year fracture is 10-15 or in 3 year if >15%

Recommend if: Previous hip/spine fracture, >2 fracture events, 10 yre fracture risk >20, T score <2.5 and >70

Biphosphonates

Common 1st line treatment which inhibits osteocalsts

Pros: reduces fracture, increased benefit/safety

Cons: Esophagitis, soteonecrosis, atypical subtrochanteric fractures

Rank Ligand inhibitor (Denosumab)

Pros: Reduces fracture vertebral and non-vertebral fractures

Cons: osteonecrosis, atypical subtrochanteric fracture,s rebound bone lsos

Selective Esttrogen Receptor Modulator

Pros: Decrease in Breast cancer

Cons: Increase in hot flashes,. thromboembolic disease, and no evidence in reduction in non-vertebral fractures

Hormone Replacement therapy

Pro: Decrease osteoblastic activity, increases bone density, treat symtpoms of estrogen deficiency

Cons: Increase CVD and PE risk, increase breast cnacer risk, adverse effect on cognition