1. Metabolic Bone Diseases BY Dr. Abdullah H.A. Juma, FRCS Ed Associate Professor & Consultant Orthopaedic Surgeon

2. Introduction Metabolic bone Metabolic bone diseases describes a group of disorders due to abnormalities of formation ( bone morphology ) and metabolism of bone ( functions ). Bone : An active tissue undergoing continuous structural & metabolic changes. The bone is surrounded by a bone fluid different from the whole body extracellular fluid.

3. Bone characteristics 1. 1. Bone Morphology. 2. 2. Bone Functions.

4. 1. Bone Morphology Morphologically, bone can be mature (lamellar ) or immature ( woven ) or unmineralized ( osteoid ). 2 types of bone in mature skeleton :.. Compact cortical bone. Consists of 50% Haversian systems (osteons) & 50% interstitial bone. Osteons consist of rings of osteocytes around central canal which carries blood & lymph vessels. The cortical bone surrounds marrow cavities & form shafts of long bones... Cancellous bone. Anastomosing trabeculae within cortical bone and predominantly seen in vertebrae,flat bones & ends of long bones.

5. Bone Morphology 1. 1. Organic matrix. 2. 2. Bone cells. 3. 3. Bone mineral. 4. 4. Blood vessels. 5. 5. Bone marrow.

6. 1. Organic Matrix It ’ s the frame work of bone. 2 types : collagenous ( 90% ) and non – collagenous ( 10% ). Collagen is triple helix consist of 3 polypeptide alpha chains. Each chain has 1000 amino acids & synthesized within the fibroblasts or osteoblasts and is broken down by collagenases to hydroxyproline & hydroxylysine and excreted in urine.

7. Collagen stability decreases with age. Collagen stability decreases with age. 4 types of collagen. Type I only occurs in bone with low carbohydrate & < 10 hydroxylysine residues per alpha chain. 4 types of collagen. Type I only occurs in bone with low carbohydrate & < 10 hydroxylysine residues per alpha chain. Non-collagenous is protein linked to substances forming proteoglycans & glycoproteins or exist as an isolated material such as Albumin & Alpha – Carboxyglutamic acid. Non-collagenous is protein linked to substances forming proteoglycans & glycoproteins or exist as an isolated material such as Albumin & Alpha – Carboxyglutamic acid.

8. Proteoglycans consist of a protein core linked to carbohydrate units such as mucopolysaccharides. Glycoproteins.. 2 forms exist in the bone :. Sialoprotein. A high metal-binding capacity.. Alpha 2 heat-stable glycoprotein. Synthesized in liver.

9. Bone Morphology 1. 1. Organic matrix. 2. 2. Bone cells. 3. 3. Bone mineral. 4. 4. Blood vessels. 5. 5. Bone marrow.

10. 2. 2. Bone cells Control formation, composition & resorption of bone. Types of cells :. Osteoblasts.. Osteoclasts.. Osteocytes.. Fibroblasts.. Myeloproliferative cells.

11. Osteoblasts Bone forming cells, synthesizing collagen, non-collagen & mineralization of bone. Uniform in size. Mononuclear & basophilic cytoplasm. Lie in single layers close to the osteoid tissue of newly formed bone. High content of Alkaline Phosphatase. Have fine processes which extend into the osteoid tissues. If resting, appear spindle & flat. If active, appear larger & plump.

12. 2. 2. Bone cells Types of cells :. Osteoblasts.. Osteoclasts.. Osteocytes.. Fibroblasts.. Myeloproliferative cells.

13. Osteoclasts

14. Metabolic bone diseases are caused by an imbalance in the metabolism of bone resorption & deposition due to : 1. Defect of Mineralization. 2. Defect of bone matrix. 3. Excessive bone resorption. 4. Paget ’ s disease.

15. 1. Defect of Mineralization. 2. Defect of bone matrix. 3. Excessive bone resorption. 4. Paget ’ s disease.