structure of physis

structure of physis

1. STRUCTURE OF PHYSIS PRESENTER:DR.TARUN KUMAR JUNIOR RESIDENT DEPT OF ORTHOPAEDICS RLJH TAMAKA KOLAR

2. SPECIFIC LEARNING OBJECTIVES At the end of the class , participants should be able to answer: What is physis What are zones of physis Vascular supply of physis Types of physeal injuries and management

3. PHYSIS Physis is also known as Growth plate The physis is a unique cartilaginous structure that varies in thickness depending on age and location Located between epiphysis and metaphysis of growing bones Responsible for longitudinal growth of the bones Appears radiolucent on X ray

4. The cells on epiphyseal surface of the epiphyseal cartilage plate continously proliferate until growth in length is completed. The mature cells on the diaphyseal surface of the epiphyseal cartilage plate degenerate and are replaced by bone from the diaphysis .

5. When full growth is attained, the epiphyeal cartilage turns into bone and can longer be found. This occurs between 18 to 25 years.

6. The peripheral margin of the physis consist of two specialized areas :- ZONE OF RANVIER It is a wedge-shaped group of germinal cells that is continous with the physis . It consists of three cell types- osteoblast , chondroblast and fibroblast.

7. Osteoblasts form the bony portion of the perichondrial ring at the metaphysis . Chondroblasts contribute to the longitudinal growth Fibroblasts circumcsribe the zone and anchor it to perichondrium above and below the growth plate.

8. PERICHONDRIAL RING OF LACROIX It is a fibrous structure that is continous with the fibroblasts of the zone of ranvier and the periosteum of the metaphysis . Perichondrial ring of LaCroix provides strong mechanical support for the bone-cartilage junction of the growth plate.

9. 1.GERMINAL ZONE (RESERVE ZONE) Chondrocytes here are spherical and seperated by more matrix compared with cells in other zones. The cells contain many lipid vacuoles and abundant endoplasmic reticulum, which is indicative of protien production.

10. ZONE OF PROLIFERATION In the proliferative zone , chondrocytes are flattened and alinged in columns parallel to the long axis of the bone. The oxygen tension is higher than in the other zones as is the cell metabolism, resulting in high concentration of cell metabolism. The primary function of this zone is cellular proliferation, other functions include the formation of intracellular matrix, proteoglycan and collagen.

11. ZONE OF HYPERTROPHY The chondrocyte become spherical and, at the base of the zone, are five times the size of chondrocyte in the proliferative zone. It has been found that insulin-like growth factor stimulates the hypertrophy of the chondrocytes in this zone, thus promoting longitudinal growth. The oxygen tension inn this part of the hypertrophic zone is low, anaerobic metabolism develops, and lactate accumulates.

12. ZONE OF PROVISIONAL CALCIFICATION Very thin layer and adjoins directly to the diaphysis . The cells are necrotic and the calcified substance undergoes cavitation and dissolution.

13. HISTOLOGY OF PHYSIS

14. VASCULAR SUPPLY OF PHYSIS EPIPHYSEAL ARTERIES supply blood to the epiphysis via multiple branches to the growth plate, providing vascularization into the proliferative zone. PERICHONDRIAL ARTERIES supply the fibrous structures of the growth plate.

15. NUTRIENT ARTERY provides four-fifths of the metaphyseal blood supply. METAPHYSEAL ARTERIES supply the remainder of the blood supply. The terminal branches of these vessels end in small vascular loops or capillary tufts below the last intact row of chondrocyte lacunae of growth plate.

16. VASCULAR SUPPLY OF PHYSIS

17. PHYSEAL INJURIES It has been estimated that 30% of fractures in children involve a physis and most heal with out any long-term complication. The hypertrophic zone has the lowest resistance to shear forces and thus is the most common anatomic site of physeal injuries. Ligaments in children are functionally stronger than the physis . Therefore a higher proportion of injuries that produce sprain in adults result in physeal fractures in children.

18. ETIOLOGY OF PHYSEAL INJURIES Trauma Infection Tumors Vascular injuries Repetitive stress

19. CLASSIFICATION –SALTER AND HARRIS

20. Type 1 fractures occur through the physis only , with or with out displacement. It has good prognosis Type 2 fractures have a metaphyseal spike attached to the seperated epiphysis with or with out displacemet . It is the most common type

21. Type 3 fractures occur through the physis and epiphysis into the joint with joint incongruity when the joint is displaced. Poor prognosis as the proliferative and reserve zones are interrupted. Type 4 fractures occur in the metaphysis and pass through the physis and epiphysis into the joint. Joint incongruity occurs with displaced fractures.

22. Poor prognosis as the proliferative and reserve zones are interrupted. Type 5 fractures, which are usually diagnosed only in retrospect, are compression or crush fractures of the physis , producing permanent damage and growth arrest. It has worst prognosis

23. MANAGEMENT: TYPE 1 and 2 fractures can be treated non operatively by closed reduction and immobiliztion with cast or slab Other types: open reduction and internal fixation

24. REFERENCES Turek’s textbook of orthopedics Campbell’s operative orthopedics

25. THANK YOU