Osteonecrosis Osteoporosis

1. OsteonecrosisOsteoporosis F. ALHILLIPathology Department, AGU

2. OSTEONECROSIS OSTEONECROSIS AVASCULAR BONE NECROSIS ASEPTIC NECROSIS Death of bone and bone marrow due to interference of blood supply and in the absence of infection

4. IDIOPATHIC OSTEONECROSIS Legg-Calve-Perthes Disease Idiopathic femoral head osteonecrosis in children 10% bilateral Idiopathic Osteonecrosis Idiopathic femoral head ostonecrosis in adult

5. Healing of Osteonecrosis Necrotic bone heals differently in the cortex and in the underlying cancellous bone i.e a. Healing of necrotic cortical bone b. Cortical of necrotic cancellous bone Necrotic Cortical bone heal by �cutting cones�

6. Necrotic cancellous bone heals by �creeping substitution� i.e. necrotic marrow is replaced by invading �creeping� neovascular tissue providing pluripotential cells for bone remodeling resulting in: a. Resorption by osteoclasts b. Surrounded by woven or lamellar bone by osteoblasts

8. OSTEOPOROSIS - Definition Metabolic bone disease characterized by diffuse skeletal lesions in which the normally mineralized bone mass is reduced below level required to sustain structural function (i.e. mechanical support)

9. OSTEOPOROSIS Bone mass is reduced but remaining bone maintain chemical composition and mineralization Mass loss most marked at sites of rapid turnover e.g. cancellous bones of vertebrae, ribs, pelvis, and end of long bones

11. OSTEOPOROSIS � Biophysical Forces Balance of activity of osteoblasts vs osteoclasts i.e. Remodeling 1. Excess of bone resorption over normal formation 2. Increased resorption over decreased formation 3. Decreased formation with no change in resorption

12. OSTEOPOROSIS � Types /1 Physiological Osteoporosis is normal (i.e. senile, post-menopausal) Pathological Osteoporosis i.e. mechanical failure (as per definition) when weight bearing bones become susceptible to stress and fracture Vertebral crush fracture Neck of femur Neck of humerus Distal radius (Colle�s fracture)

13. OSTEOPOROSIS � Types /2 Localized Osteoporosis as in diffuse atrophy Generalized Osteoporosis Primary vs Secondary Osteoporosis

14. Primary Osteoporosis Type 1 Primary (Post-menopausal) Osteoporosis Increase number of osteoclasts enhancing its activity over accretion (i.e. bone formation) Oestrogen withdrawal ?? increased number of osteoclasts through action of cytokines Type 2 Primary (Senile) Osteoporosis Appear above the age of 70 Reflect attenuated osteoblasts i.e. no increased in number or activity of osteoclasts

16. Modifying factors in Primary Osteoporosis Genetic Factors Calcium Intake Calcium / Vitamin D metabolism Environmental factors