Musculoskeletal System Structure, Function, and Injuries

STRUCTURE AND FUNCTION OF THE MUSCULOSKELETAL SYSTEM 2 STRUCTURE AND FUNCTION OF BONES Gives form to the body Supports tissues Permits movement by providing points of attachment for muscles Protects many vital organs Serves as a site for blood cell formatio...

STRUCTURE AND FUNCTION OF THE MUSCULOSKELETAL SYSTEM 2 STRUCTURE AND FUNCTION OF BONES Gives form to the body Supports tissues Permits movement by providing points of attachment for muscles Protects many vital organs Serves as a site for blood cell formation Plays a role in mineral and hormone homeostasis 3 ELEMENTS OF BONE TISSUE Rigid connective tissue Bone cells enable bone to grow, repair, change Constituents shape, synthesize new Cells bone tissue, and resorb Fibers old tissue Bone matrix Ground substance Calcification Crystallized minerals 4 BONE CELLS Osteoblasts Derived from mesenchymal stem cells Primary bone-producing cells Respond to parathyroid hormone Produce osteocalcin Synthesize osteoid Nonmineralized bone matrix Express the cytokine receptor activator nuclear factor kappa-B ligand (RANKL) Necessary for forming osteoclasts  5 BONE TISSUE Osteocytes Transformed osteoblasts that are surrounded in osteoid as it hardens from deposited minerals Synthesize matrix molecules Key regulators of both bone formation and resorption Osteoclasts The major reabsorptive cells of the bone Large, multinucleated cells  6 BONE MATRIX Collagen fibers Glycoproteins Control collagen interactions that lead to Make up bulk of bone matrix fibril formation Proteoglycans Sialoprotein, osteocalcin, bone albumin, alpha-glycoprotein Strengthen bone Bone minerals Play role in bone calcium deposition and calcification Two phases of mineralization Formation of the initial mineral deposit Proliferation or accretion of additional mineral crystals on the initial mineral deposits Calcium and phosphate 7 MAINTENANCE OF BONE INTEGRITY Remodeling Basic multicellular units Repair of microscopic bone injuries Existing bone is resorbed and new bone is laid down to replace it Three phases: Activation of the remodeling cycle Resorption Formation of new bone 8 BONE REPAIR New bone is the final result Stages: Inflammation/hematoma formation Procallus formation Callus formation Callus replacement Remodeling 9 STRUCTURE AND FUNCTION OF JOINTS Joint Also called articulation Site where two or more bones meet/attach Provides stability and mobility to the skeleton 10 AGING AND THE MUSCULOSKELETAL SYSTEM Bones Bone loss Less dense, less strong, more brittle Bone remodel time is lengthened Joints Cartilage becomes more rigid, fragile, susceptible to fraying Decreased range of motion Muscles Sarcopenia Decrease in muscle mass and strength Reduced oxygen intake, basal metabolic rate, and lean body mass Alterations of Musculoskeletal Function  Musculoskeletal Injuries Fractures  A fracture is a break in the continuity of a bone  Classifications ◦ Complete or incomplete◦ Greenstick ◦ Closed or open ◦ Torus ◦ Comminuted ◦ Bowing ◦ Linear ◦ Pathologic ◦ Oblique ◦ Stress ◦ Spiral ◦ Fatigue ◦ Transverse COPYRIGHT © 2017, ELSEVIER INC. ALL RIGHTS RESERVED. 12 Fractures (Cont.) Healing ◦ Direct ◦ Most often occurs when surgical fixation is used to repair a broken bone ◦ Intramembranous bone formation ◦ No callus formation ◦ Indirect ◦ Most often observed when a fracture is treated with a cast or other nonsurgical Manifestations method ◦ Unnatural alignment, ◦ Intramembranous and endochondral bone swelling, muscle spasm, formation tenderness, pain, impaired ◦ Callus formation sensation, and decreased ◦ Remodeling of solid bone mobility ◦ Often transient numbness due to nerve trauma 13 Dislocation and Subluxation Dislocation ◦ Displacement of one or more bones in a joint ◦ Loss of contact between articular cartilage Subluxation ◦ Contact between articular surfaces is only partially lost Associated with fractures, muscle imbalance, rheumatoid arthritis, or other forms of joint instability 14  Rhabdomyolysis Rapid breakdown of muscle that causes the release of intracellular contents, including the protein pigment myoglobin, into the extracellular space and bloodstream Can result in hyperkalemia, cardiac arrhythmia, or acute renal failure Triad of manifestations ◦ Muscle pain ◦ Weakness ◦ Dark urine Diagnosed when CK level five to ten times upper limit of normal (about 1000 units/L) Renal failure likely when CK reaches 15,000 units/L 15 Rhabdomyolysis (Cont.) 16 Compartment Syndrome Result of increased pressure within a muscle compartment Can be caused by any condition that disrupts the vascular supply to an extremity Muscle ischemia causes edema  rising compartment pressure, and tamponade  muscle infarction and neural injury “6 Ps” of compartment syndrome 17 Osteoporosis Poorly mineralized bone and increased Potential causes risk of fractures due to alterations in ◦ Endocrine dysfunction bone microarchitecture ◦ Parathyroid hormone, cortisol, thyroid hormone, and growth hormone Old bone resorbed faster than new bone ◦ Medications made ◦ Vitamin D deficiency ◦ Spontaneous fractures ◦ Underlying diseases ◦ Low physical activity ◦ Abnormal BMI Fractures are the major complication 18  Osteoporosis (Cont.) Postmenopausal osteoporosis ◦ Middle-aged and older women ◦ Estrogen deficiency and secondary causes ◦ Remodeling imbalance between the activity of osteoclasts and osteoblasts 19 COPYRIGHT © 2017, ELSEVIER INC. ALL RIGHTS RESERVED. 20 Osteoporosis (Cont.) Dual x-ray absorptiometry (DXA) ◦ Gold standard for detecting and monitoring osteoporosis Trabecular bone score (TBS) ◦ Evaluates pixel variations in the gray-level areas of lumbar spine images from DXA scans ◦ Enhanced predictions of fracture risk 21  Osteomalacia Inadequate or delayed mineralization of osteoid Remodeling cycle proceeds through osteoid formation but calcification does not occur; the result is soft bones ◦ Pain, bone fractures, vertebral collapse, bone malformation Results from vitamin D deficiency 22  Osteomyelitis Bone infection often caused by bacteria, usually Staphylococcus aureus Hematogenous ◦ Pathogens carried through the bloodstream ◦ Cutaneous, sinus, ear, and dental infections ◦ Insidious onset ◦ Vague symptoms ◦ Fever, malaise, anorexia, weight loss, and pain Contiguous ◦ Infection spreads to an adjacent bone ◦ Open fractures, penetrating wounds, surgical procedures ◦ Manifested by signs and symptoms of soft tissue infection ◦ Low-grade fever, lymphadenopathy, local pain, and swelling 23  Osteoarthritis Characterized by Manifestations ◦ Loss and damage of articular cartilage ◦ Pain (worsens with activity) ◦ Inflammation ◦ Stiffness (diminishes with ◦ New bone formation of joint margins activity) ◦ Subchondral bone changes ◦ Enlargement of the joint ◦ Variable degrees of mild synovitis ◦ Tenderness ◦ Thickening of the joint capsule ◦ Limited motion ◦ Muscle wasting Prevalence increases with age ◦ Partial dislocation ◦ Deformity 24 Osteoarthritis (Cont.) Risk factors ◦ Increased age ◦ Joint trauma, long-term mechanical stress ◦ Obesity Characteristics ◦ Local areas of damage and loss of articular cartilage ◦ New bone formation of joint margins ◦ Subchondral bone changes ◦ Variable degrees of mild synovitis and thickening of the joint capsule 25 Classic Inflammatory Joint Disease Inflammatory damage or destruction in the synovial membrane or articular cartilage Systemic signs of inflammation Infectious or noninfectious 26 Rheumatoid Arthritis Inflammatory autoimmune joint disease Systemic autoimmune damage to connective tissue, primarily in the joints (synovial membrane) Cause unknown; multifactorial with strong genetic predisposition Pathogenesis ◦ Three processes ◦ Neutrophils and other cells in the synovial fluid become activated ◦ Inflammatory cytokines: tumor necrosis factor- alpha (TNF-α), interleukin-1 beta (IL-1β), interleukin-6 (IL-6), interleukin-7 (IL-7), interleukin- 21 (IL-21), induce enzymatic breakdown of cartilage and bone ◦ T cells also interact with synovial fibroblasts through TNF-α, converting synovium into a thick, abnormal layer of granulation tissue (pannus) 27 28 Rheumatoid Arthritis (Cont.) Insidious onset Systemic manifestations ◦ Inflammation, fever, fatigue, weakness, anorexia, weight loss, and generalized aching and stiffness Painful, tender, stiff joints Joint deformities Rheumatoid nodules ◦ Caplan syndrome 29 Rheumatoid Arthritis (Cont.) 30 COPYRIGHT © 2017, ELSEVIER INC. ALL RIGHTS RESERVED. 31  Gout Syndrome caused by either Manifestations overproduction or underexcretion of ◦ An increase in serum urate uric acid concentration (hyperuricemia) ◦ Recurrent attacks of monoarticular Manifests high levels of uric acid in arthritis (inflammation of a single the blood and other body fluids joint) ◦ Occurs when the uric acid ◦ Deposits of monosodium urate concentration increases to high monohydrate (tophi) in and around enough levels to crystallize the joints ◦ Crystals deposit in connective tissues ◦ Renal disease involving glomerular, throughout the body Risk factors tubular, and interstitial tissues and ◦ When these crystals occur in the ◦ Male sex blood vessels synovial fluid, the inflammation is ◦ Increasing age◦ Formation of renal stones known as gouty arthritis ◦ High intake of alcohol, red meat, and ◦ Linked to purine metabolism fructose ◦ Drugs 32 Gout (Cont.) Trauma is most common aggravating factor Primary symptom is severe pain Approximately 50% of the initial attacks occur in the metatarsophalangeal joint of the great toe ◦ Other areas include the heel, ankle, instep of the foot, knee, wrist, or elbow 1000 times more likely to develop renal stones than general population 33 Gout (Cont.) Manifestations of acute gouty attack ◦ Severe pain, especially at night ◦ Hot, red, tender joint ◦ Signs of systemic inflammation ◦ Increased sedimentation rate ◦ Fever ◦ Leukocytosis 34 Secondary Muscular Dysfunction Contractures ◦ Muscle fiber shortening without an action potential ◦ Caused by failure of the calcium pump, even with available ATP Stress-induced muscle tension ◦ Neck stiffness, back pain, and headache ◦ Associated with chronic anxiety 35 Fibromyalgia Autoimmune disorders often coexist Studies of genetic factors have implicated alterations in genes affecting serotonin, catecholamines, and dopamine Chronic widespread diffuse joint pain, fatigue, and tender points Vague symptoms ◦ Increased sensitivity to touch ◦ Absence of inflammation ◦ Fatigue ◦ Sleep disturbances/nonrestorative sleep ◦ Anxiety and depression 36 Fibromyalgia (Cont.) Manifestations ◦ Prominent symptom of fibromyalgia is diffuse, chronic (present more than 3 months) pain that is burning or gnawing in nature ◦ Only reliable finding on examination is the presence of multiple tender points; the pain often begins in one location, especially the neck and shoulders, but then becomes more generalized ◦ Profound fatigue Diagnosis ◦ Axial pain, left- and right-sided pain, and upper and lower segment pain; and a symptom severity (SS) score ◦ SS score includes symptoms such as fatigue, waking unrefreshed, and cognitive difficulty 37 COPYRIGHT © 2017, ELSEVIER INC. ALL RIGHTS RESERVED. 38 Bone Tumors May originate from bone cells, cartilage, fibrous tissue, marrow, or vascular tissue ◦ Osteogenic ◦ Chondrogenic ◦ Myelogenic Osteosarcoma ◦ Most common malignant bone-forming tumor ◦ Predominantly in persons under 20 years; occurs in 50- to 60-year-olds if they have a history of radiation therapy ◦ Tumors contain osteoid produced by anaplastic stromal cells ◦ Deposited as thick masses or “streamers” ◦ Located in the metaphyses of long bones 39