Disorders of bone .pptx

bone healing

1. Skeletal system DR N MANJULA

2. INTRODUCTION The skeletal system consists of the bones, their associated cartilages, and the joints. Bone is a specialized connective tissue which has structural, protective, metabolic and hematopoietic functions (produces blood cells).

3. Cells of the Bone Tissue Osteoblasts: produce osteoid - bone forming cells. Osteoclasts : These are mature multinucleated cells - responsible for bone resorption.

4. FRACTURE A fracture is a broken bone. It can range from a thin crack to a complete break in the bone. Phases of Fracture Healing: 1. Inflammatory Phase 2. Reparative Phase 3. Remodeling Phase

5. Fracture and Hemorrhage Soon after fracture, blood vessels rupture which leads to extensive hemorrhage (hematoma) at the fracture site and surrounding tissue. Necrosis of bone also occurs at the fracture site.

6. Inflammatory Phase

7. Inflammatory Cells Fibrin meshwork in the clotted blood helps to seal the fracture site. Influx of inflammatory cells (neutrophils and macrophages) to the a rea. I n growth of fibroblasts and new capillary vessels to the site, producing granulation tissue between the fracture fragments.

8. Activation of osteoprogenitor cells: The inflammatory cells and platelets release cytokines → activate the osteoprogenitor cells in: Periosteum Medullary cavity Surrounding soft tissues.

9. Formation of Granulation Tissue It consists of proliferating capillaries and fibroblasts and are formed at the site of fractures. Simultaneously, degranulated platelets and migrating inflammatory cells release PDGF, TGF-β, FGF.

10. Callus Osteoprogenitor cells → activate both osteoblastic and osteoclastic activities at the fracture site. Osteoblasts derived from activated osteoprogenitor cells migrate into the granulation tissue and differentiate into osteoid synthesizing units. They deposit large quantities of osteoid collagen in a haphazard pattern producing woven bone (unmineralized bone is called osteoid).

11. Stages of bone healing

12. Granulation tissue containing (mineralized or unmineralized) bone or cartilage is termed a callus. At this stage, callus is predominantly uncalcified and is called soft-tissue callus or pro callus , which provides a type of temporary connection between the ends of the fractured bones. However, pro callus does not have any structural rigidity for any weight-bearing. The callus depending on its site and appearance can be divided into external and internal callus . The repair tissue attains maximal thickness at the end of the second or third week and consists of hyaline cartilage and woven bone.

13. Internal callus It is derived from osteoprogenitor cells of medullary cavity and grows outward towards the fracture site. This bridges the fracture in the region of medullary cavity. External callus It is formed from the osteoprogenitor cells of periosteum and is found on the surface of the bone. It bridges the fracture site outside the bone and continues to grow inwards toward the fracture site. In this region, the osteoprogenitor cells may differentiate into cartilage around the fracture site.

14. Reparative Phase

15. Lamellar Bone Formation As the healing advances, the hyaline cartilage and woven bone of the original fracture callus are replaced by lamellar bone. This is stronger and consists of parallel collagen fibers. Endochondral Ossification The replacement process is known as endochondral ossification with respect to the hyaline cartilage and bony substitution with respect to the woven bone.

16. Bony Callus Mineralized (calcified) callus - Bony (osseous) callus . As the mineralization proceeds, the stiffness and strength increases. By the second or third week , controlled weightbearing can be tolerated.

17. Remodeling Phase

18. Several weeks after a callus has sealed the bone ends , the remodeling phase begins. During healing, excess of bony callus is formed around the fracture site which is resorbed. As the callus is subjected to weight-bearing forces , the portions of bony callus that are not physically stressed by this weight are slowly resorbed by osteoclasts. Thus, the osteoclasts act to remodel bone and decrease the size of callus.

19. The remodeling phase substitutes the trabecular bone with compact bone. Remodeling phase continues till the original bone shape (contour), outline and strength of the fractured bone is re-established. The whole process of healing of a bone fracture usually takes about 6–8 weeks.

20. Fracture healing: Three phases 1. Inflammatory - Fracture and inflammatory cells & Granulation tissue formation. Callus: Granulation tissue containing (mineralized or unmineralized) bone or cartilage. Fracture healing: First forms woven bone followed by lamellar bone. 2. Reparative 3. Remodeling - Remodeling to original bone contour. Mineralized callus is called bony/osseous callus. Complications of fracture healing : • Delayed union / nonunion • Pseudoarthrosis • Large callus with deformity

21. CAUSES OF DELAYED HEALING

22. Complications of Healing Delayed union and nonunion of fracture. Pseudoarthrosis. Large callus with deformity.

23. OSTEOMYELITIS

24. Definition Osteomyelitis is defined as inflammation of the bone and marrow. Primary: Where bone is the primary solitary focus of disease. Secondary: Develops as a complication of any systemic infection.

25. Pyogenic Osteomyelitis It is usually caused by bacteria . Most common pathogens are Staphylococcus aureus. Others: Escherichia coli , Pseudomonas , Klebsiella, Neisseria gonorrhoeae, Haemophilus influenzae and Salmonella species. Escherichia coli  genitourinary tract infections / intravenous drug abusers. Neonatal period : Haemophilus influenzae and group B streptococci. S ickle cell disease : Salmonella infection. Mixed bacterial infections : It is due to direct spread or surgery or open fractures. In about 50%, no organisms can be isolated.

26. Portal of Entry of Organism 1. Hematogenous Spread 2. Direct Implantation 3. Spread from Adjacent (Contiguous) Site

27. TYPES BASED ON DURATION ACUTE SUB ACUTE CHRONIC

28. PATHOGENESIS

29. sequestrum The fragment of dead necrotic piece of bone , which is embedded in the pus, is known as a sequestrum. The pus penetrates the periosteum and leads to a soft-tissue abscess → may penetrate the skin → form a draining sinus . Hole formed in the bone during the formation of a draining sinus is known as cloaca .

30. Involucrum After first week, chronic inflammatory cells become more numerous and the cytokines released stimulates osteoclastic bone resorption and deposition of reactive bone in the periphery . Reactive new bone forms a sheath around the necrotic (segment of devitalized infected bone) sequestrum. This reactive new bone formed is known as involucrum .

31. BRODIE’S ABSCESS : CHRONIC OSTEOMYELITIS WHICH IS LOCALIZED AND WALLED OFF BY FIBROUS TISSUE. POTT’S DISEASE / POTT’S SPINE : TUBERCULOUS INFECTION OF VERTEBRAL DISC.

32. Complications Septicemia Acute suppurative arthritis Pathologic fractures Chronic osteomyelitis

33. TUBERCULOUS OSTEOMYELITIS Mycobacterium tuberculosis  is the organism that is the causative agent for tuberculosis (TB, or MTB). There are other "atypical" mycobacteria such as  M. kansasii  that may produced a similar clincal and pathologic appearance of disease.  M. avium-intracellulare  complex (MAI, or MAC). Skeletal Tuberculosis:   Tuberculous osteomyelitis involves mainly the thoracic and lumbar vertebrae (known as Pott disease) followed by knee and hip. There is extensive necrosis and bony destruction with compressed fractures (with kyphosis ) and extension to soft tissues, including psoas "cold" abscess. 

34. osteoporosis

35. Reduction in bone mass due to increased bone porosity, which predisposes bones to fracture. Usually refers to postmenopausal or senile loss of bone severe enough to cause fractures

36. Osteopenia : defined as radiologic decrease in density of skeleton Primary causes : due to postmenopausal condition. Secondary causes : Age related changes (SENILE) : osteoblasts have reduced reproductive and biosynthetic potential in elderly Immobilization : Genetics : variation in Vitamin D receptor type S moking, alcohol abuse Bone mass : peak bone mass occurs in young adults, based on physical activity, muscle strength, diet, hormones.

37. Clinical Features The clinical manifestations depend on which bones are involved. Vertebral fractures that frequently occur in the thoracic and lumbar regions are painful. Fractures of the femoral neck, pelvis, or spine lead to immobilization and complications such as pulmonary embolism and pneumonia, resulting in death.

38. DIAGNOSIS The best estimates of bone loss is by: Dual-energy x-ray absorptiometry (DEXA) Quantitative computed tomography Calcium estimation Alkaline phosphatase level

39. TREATMENT Preventive and therapeutic management of osteoporosis includes exercise, calcium and vitamin D intake, and bisphosphonates . Denosumab, an anti-RANKL antibody, has shown promise in treating some forms of postmenopausal osteoporosis.

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