BIOMECHANICS PROPERTIES OF BONE - Padmashree Institute of Physiotherapy

Biomechanics properties of bone

1. BIOMECHANICS PROPERTIES OF BONE SUBMITTED BY: LALRUATKIMI MODERATOR : MR. NAGARAJ S(MPT) MPT 1 ST YEAR PADMASHREE INSTITUTE OF PHYSIOTHERAPY

2. CONTENTS   Introduction Types of bone Bone Healing Behavioral Properties of bone Characteristics of bone Applied aspects

3. INTRODUCTION It is the study of science concern with internal and external acting forces on the bone .Bone tissue is a specialized connective tissue whose solid composition suits it for supportive and protective rolls.

4. Components of bone

5. Composition of Human Bone WATER- 25-30% MINERAL- 60-70% (Resists compression) Calcium phosphate-e 85% Calcium carbonate -10% Calcium fluoride - 2-3% Magnesium fluoride - 2-3% PROTEIN (Collagen) 5-15% (Resists tension)

6. BONE TYPE (density) CORTICAL BONE/ COMPACT -80% of adult skeleton -more resistant to bending and torsional force -slow turnover -Relatively high Young’s Modulus

7. CANCELLUS/TREABECULAR -Less dense -More remodeling along lines of stress (Wolff’s law) -Much larger surface area -Higher turnover -Lower apparent modulus -More elastic

8. BONE HEALING: Phases of Fracture Healing There are three major phases of bone healing and two of these can be sub-divided to make a total of five phase R eactive phase. R eparative phase . Remodeling phase

9. Reactive phase:   The reactive phase includes the trauma of the fracture and the first few hours following the initial injury. During this time granulation tissue starts to form from the replication of fibroblasts. These fibroblasts survive in spite of the fact other cells and blood cells are degenerating and dying in and around the hematoma that is forming.

10. Reactive phase:   In the days following the injury, replication and transformation of periosteal cells continues. Those cells proximal to the fracture develop into chondroblasts and form hyaline cartilage. The cells distal to the fracture develop into osteoblasts. Osteoblasts produce osteoid which is composed mainly of Type 1 collagen, they are also responsible for mineralization of the osteoid matrix. Although osteoblasts implies an immature cell type, osteoblasts are in fact the mature bone cells entirely responsible for generating bone tissue or osteocytes. As the osteoids form woven bone and the fibroblasts develop into chondroblasts and form into hyaline cartilage, these two new tissues grow and join together to form the fracture callus. .

11. After the callus restores some of the bones original strength, the next phase begins with the replacement of the two new tissues with lamellar bone. This is known as endochondral ossification. The lamellar starts forming soon after the collagen matrix of either tissue becomes mineralized. As the osteoblasts penetrate the mineralized matrix they form lamellar bone called cancellous bone. Eventually the fracture callus is replaced by cancellous bone and more of the bones original strength is restored.   .

12. Remodeling   Remodeling is the final phase of bone healing and involves the body's use of osteoclasts. Osteoclasts are a type of bone cell that removes bone tissue by removing the mineralized matrix. The process know as resorption happens when the cancellous bone is first absorbed leaving a shallow pit, “ Howship's lacuna”, while osteoblasts deposit cortical bone in its place. This process remodels the bone into a new shape leaving it to closely resemble the bones original shape and strength. .

13. Behavioral Properties of bone Forces and moments can be applied to a structure in various directions, producing. Tension Compression Shear Bending Torsion Stress

14. 1. Tension: During tensile loading, equal and opposite loads are applied outward from the surface of the structure, and tensile stress and strain result in the structure.

15. 2.Compression During compressive loading equal and opposite loads are applied toward the surface of the structure and compressive stress and strain result inside the structure.It can be thought of as many of the small forces directed into the surface of the structure.

16. 3.Shear force T he load is applied parallel to the surface of the structure. It is subjected deforms internally in an angular manner.

17. 4.Bending In bending, loads are applied to a structure in a manner that causes it to bend about an axis. When a bone is a loaded bending, it is subjected to its combination of tension and compression. Bending Forces

18. 5.Torsion In torsion ,a load is applied to a structure in a manner that it causes it to twist about an axis c aused by a twisting force produces shear, tensile, and compressive loads

19. Relative strength of bone

20. CHARACTERISTICS OF BONE : STRESS –STRAIN CURVE(load deformation curve)

21. YOUNG’S MODULUS: The modulus of elasticity defines the mechanical behavoir of the material and is a measure of material(resistance offered by the material to the external loads.) When the portion of the curve is a straight line.The deformation is directly proprtional to the material ability to resists the load. A value for stiffness can be found by dividing the load by the deformation for any two successive sets of points in the elastic range of the curve. The inverse of resistance is called compliance. If the slope of the curve is steep and the modulus of elasticity is high, the material will exhibit a high degree of stiffness and low compliance. If the slope of the curve is gradual and the modulus of elasticity is low, the material will exhibit a low degree of stiffness and a large compliance. Modulus = tensilestress (load) Tensile Strain(deformation)

22. APPLIED ASPECTS: Chondromalacia Patella The softening and breakdown the tissue(Cartilage)on the underside of the patella.As knee articulation moves in amplitude of movement,the patella moves up and down in its sulcus.High compressive strength in flexion,breakdown primarily on the patellar surface,is the source of the destructive process that breakdown the cartilage and underlying surface of patella.

23. Bone injury (e.g. endplate fracture) is far from the common cause of most back pain. However, extensive research has been conducted into disc compression as it is thought to be largely responsible for vertebral end-plate fracture, disc herniation, and resulting nerve root irritation. Back compression has been argued to be a good predictor of low-back and other overexertion injuries. Due to the clinical interest in this area data exists on the compressive strength of the lumbar vertebral bodies and intervertebral disks Bone injury and Low Back Pain.

24. Fatigue Failure Compression fracture is the common failure mode of the vertebra-disc complex in severe axial loading. . Low back pain and back disorders associated with frequent lifting, whole-body vibration and repeated shocks point to a chronic degeneration of tissues, rather than acute failure.

25. A typical ankle sprain in inversion occurs when the foot is roll to the side, elongating the ligaments. Ankle Strain

26. An epiphyseal fracture of the ditaleapiphysis isusualy created by a sheraing strength.A strength applied in valgus on the thigh or shin with foot fixed and hyperextened knee is commonly produced Epiphyseal Fracture

27. Changes of bone over a period of time In Adult Years little change in length most change in density l ack of use decreases density activity - increased activity leads to increased diameter, density, cortical w idth . Marked reduction in amount of cancellous bone and thinning cortical bone lead to increaed in bone fragility.

28. Summary Bone is a complex two phase material. One phase is composed of inorganic material and the other is an organ matrix of collagen and ground substance. Bone is having a behavioral properties exhibiting different mechanical load in different directions. Mature bone is strongest and stiffness in compression. Muscle contraction affects stress patterns in bone producing compressive stress that partially neutralize tensile stress acting on the bone. With aging comes a marked reduction in the amount of the cancellous bone. These changes diminish the strength and stiffness