Bones Biomechanics PDF

Bones biomechanics 1. Bone composition and structure BONE TISSUE Specialized connective tissue that has a mineralized extracellular matrix Its main properties are: hardness, strength and high tensile and compressive resistance Its main functions are: body support, organ prote...

Bones biomechanics 1. Bone composition and structure BONE TISSUE Specialized connective tissue that has a mineralized extracellular matrix Its main properties are: hardness, strength and high tensile and compressive resistance Its main functions are: body support, organ protection, calcium deposit and blood cell formation (Constant remodeling) GROSS ORGANIZATION OF BONE There are 2 ways to structure: - Compact bone: dense, solid, without cavities - Cancellous bone: fine network-like trabeculae LONG BONES: - Epiphysis: cancellous bone with a fine layer of compact bone - Metaphysis: hyaline cartilage in children and epiphyseal line in adults - Diaphysis: compact bone cylinder with internal cavity SHORT BONES: - Cancellous bone with a fine layer of compact bone BONE FACING PERIOSTIUM: - Covers the external surfaces - Dense connective tissue - Osteoprogenitor cells, osteoblast, and bone lining cells. ENDOSTIUM: - Fine layer that covers internal surfaces - Osteoprogenitor cells. BONE TISSUE COMPONENTS CELLS: - Osteoprogenitor cells - Osteoblast - Bone lining cells - Osteocytes - Osteoclasts EXTRACELLULAR MATRIX: - Mineralized bone matrix - Calcium phosphate in the form of hydroxyapatite crystals - Fibers and ground substance HIERARCHICAL STRUCTURE OF THE BONE To understand the biomechanical properties of the bone — take into account — structural levels  2. Biomechanical properties of bone BIOMECHANICS OF THE ENTIRE STRUCTURE - Greater resistance to compression than to traction - Weakness against shear forces - The flexural resistance will depend on the stiffness and the value of the expiration or fracture load. For example, Krohn-Dehli suffers and avulsion fracture of the lower pole of patella BIOMECHANICS OF TISSUE COMPONENTS Biomechanics of the compact bone: - Greater resistance to compression than to traction - A huge weakness against torsion - 60% of the resistance of whole bone Biomechanics of the cancellous bone: - Greater resistance to compression than to traction - Trabeculae are reorientated depending on the loads to which they are subjected more frequently BIOMECHANICS OF OSTEONS AND INDIVIDUAL TRABECULAE Longitudinal lamellae: - Greater resistance to traction and torsion Transverse lamellae: - Greater resistance to compression, shear forces and flexion Individual trabeculae: - The longitudinal modulus of elasticity is considerably less than that of the osteons of the cortical bone BIOMECHANICS OF MOLECULAR COMPONENTS Collagen fibers: - Under tensile stress — initial linear strain of all the fibers - From the point of “critical strain” — heterogeneous strain — Changes in mineral composition within each fiber? Hydroxyapatite crystals: - Greater hardness and elasticity on the basal faces but greater resistance on the laterals - Greater tolerance to microfractures JOINT - Elements of union between bone and bone - According to mobility: - Synarthrodial: without mobility - Amphiarthrodia: little movement - Diarthrodial: great rage on moving - Diarhtroamphiarthrodia: mix of the two above - According to components: - Membranous - Cartilaginous - Synovial - Bone  3. Surgical effects FRACTURES Total or partial breakage of the bone - Open fracture: the bone pokes through the skin and can be seen, or a deep wound exposes the bone - Closed fracture: the bone is broken but the skin remains intact. Most common type of fractures - Green stem: incomplete fracture. A portion of the bone break causing the other side to bend - Transverse: the break occurs in a straight line through the bone - Spiral: the break is diagonal across the bone - Compression: the bone is crushed, causing the broken bone to become wider or flatter - Comminuted: the break occurs in 3 or more pieces, and fragments are present at the fracture site - Segmental: the same bone is fractured in two places, leaving a “floating” segment Etiology of fractures Fractures occurs when there is more force applied to the bone than the bone can withstand - Traumatic failure: falls or direct hits - Stress fracture: overuse or repetitive motion - Disease fractures: osteoporosis or bone cancer Symptoms and diagnosis of fractures CLINICAL DIAGNOSIS - Sudden pain - Difficulty to move the injured and surrounding areas - Swelling - Obvious deformity - Warmth or redness IMAGING DIAGNOSIS - Radiography - Magnetic resonance imaging - Computed tomography Management of fractures - Conservative treatment: immobilization is performed with a plaster to keep it align and promote the consolidation of the fracture - Surgical treatment: surgery may be required to put certain types of broken bones back to place. Occasionally, internal or external fixation devices (plates, nails or rods) are used to hold the bone fragments in place while they weld. BONE DEFORMITIES Atypical, structural deviation or distortion of bone shape from its normal alignment, length and size. Could be congenital or acquired. Symptoms: - Pain - Discomfort - Difficulty moving - Problems in development and growth - Pathologies or injuries as a result of misalignment Treatment: it can be tried with orthopedic devices such as splints but in most cases they end up in surgery. Most common in bone deformities - Bone dysplasias: alteration in the formation of bone tissue, that causes an absence or less growth in a bone than the physiological - Bone misalignments: alteration of the mechanical axes of the body due to discrepancies or abnormal rotations that cause loss of intrinsic stability of the skeleton. - Bone malformations: abnormal development of bone either in shape, union with other bones or internally in terms of bone density Diagnosis and treatment of bone deformities DIAGNOSIS: - Treatment obvious deformity - Abnormal movement patterns - Sometimes symptoms or other injuries such as joint dislocations or repeated fractures as associated - Imaging tests detect a clear deformity TREATMENT: - Splints (they don’t usually solve the problem) - Cuts into the bone and placement of plates to reeling - Bone grafts to supply the absences of these - Metal rods and tensioners to guide growth OSTEOPOROSIS A disease characterized by a decrease in bone density due to the loss of normal bone tissue Decrease in the resistance of the bone against load or trauma, with the consequent appearance of fractures Etiology: - Menopause - Alcoholism - Some drugs - Rheumatic, endocrine or inflammatory disease - Natural loss of bone mass typical of aging Symptoms, diagnosis and treatment SYMPTOMS: - “Silent disease” - Fractures: vertebrae, hip and wrist DIAGNOSIS: - Bone densitometry: