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2012-04-06 13:11:46

Alterations of Musculoskeletal Function
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  1. Musculoskeletal Injuries
    • The most serious musculoskeletal in jury is a fracture. A bone can be completely or incompletely fractured. A closed fracture leaves the skin intact. An open fracture has an overlying skin wound. The direction of the fracture line can be linear, oblique, spiral, or transverse. Greenstick, torus, and bowing fractures are examples of incomplete fractures that occur in children. Stress fractures occur in normal or abnormal bone that is subjected to repeated stress. Fatigue fractures occur in normal bone subjected to abnormal stress. Normal weight bearing can cause an insufficiency fracture in abnormal bone.
    • Dislocation is complete loss of contact between the surfaces of two bones. Subluxation is partial loss of contact between two bones. As a bone separates from a joint, it may damage adjacent nerves, blood vessels, ligaments, tendons, and muscle.
    • Tendon tears are called strains, and ligament tears are called sprains. A complete separation of a tendon or ligament from its attachment is called an avulsion.
    • Myoglobinuria (rhabomyolysis) can be a serious life-threatening complication of severe muscle trauma.
  2. Disorders of Bones
    • Metabolic bone diseases are characterized by abnormal bone structure. In osteoporosis the density or mass of bone is reduced because the bone-remodeling cycle is disrupted. Osteomalacia is a metabolic bone disease characterized by inadequate bone mineralization. Excessive and abnormal bone remodeling occurs in Paget disease.
    • Osteomyelitis is a bone infection caused most often by bacteria. Bacteria can enter bone from outside the body (exogenous osteomyelitis) or from infection sites within the body (hematogenous osteomyelitis).
  3. Disorders of Joints
    • Because of improved imaging technology, inflammation has been identified as an important feature of osteoarthritis.
    • Osteoarthritis (OA) is a common, age-related disorder of synovial joints. The primary defect in OA is loss of articular cartilage.
    • Rheumatoid arthritis is an inflammatory joint disease characterized by inflammatory destruction of the synovial membrane, articular cartilage, joint capsule, and surrounding ligaments and tendons. Rheumatoid arthritis is a systemic disease that affects the heart, lungs, kidneys, and skin as well as the joints.
    • Ankylosing spondylitis is a chronic, inflammatory joint disease characterized by stiffening and fusion of the spine and sacroiliac joints. It is a systemic, immune inflammatory disease.
    • Gout is a syndrome caused by defects in uric acid metabolism with high levels of uric acid in the blood and body fluids. Uric acid crystallizes in the connective tissue of a joint where it initiates inflammatory destruction of the joint.
  4. Disorders of Skeletal Muscle
    • A pathologic contracture is permanent muscle shortening caused by muscle spasticity, as seen in central nervous system (CNS) injury or sever muscle weakness.
    • Stress-induced muscle tension is presumably caused by increased activity in the reticular activating system and gamma loop in the muscle fiber. The use of progressive relaxation training and biofeedback has been advocated to reduce muscle tension.
    • Fibromyalgia is a chronic musculoskeletal syndrome characterized by diffuse pain and tender points. Unknown but suspected is that muscle is the end organ responsible for the pain and fatigue. Most cases are women, and the peak age is 30 to 50 years.
    • Atrophy of muscle fibers and overall diminished size of the muscle are seen after prolonged inactivity. Isometric contractions and passive lengthening exercises decrease atrophy to some degree in immobilized patients.
    • Hyperexcitable membranes cause the physical and electrical phenomenon of Myotonia. The disorder is treated with drugs that reduce muscle fiber excitability. Periodic paralysis is caused by an unresponsive muscle membrane and is accompanied by changes in serum potassium. The biochemical defect is possibly related to changes in the muscle membrane and sarcoplasmic reticulum.
    • Metabolic muscle diseases are caused by endocrine disorders, glycogen storage disease, enzyme deficiencies, and abnormal lipid function. The muscle depends on a complex system of carbohydrates and fats converted by enzymes to produce energy for the muscle cell. Abnormalities in these pathways can inhibit function or cause damage to the muscle fiber. These illnesses are rare, yet they account for significant functional abnormalities.
    • Viral, bacterial, and parasitic infections of muscles produce the characteristic clinical and pathologic changes associated with inflammation. These are usually treatable and self-limiting disorders.
    • Polymyositis (generalized muscle inflammation) and dermatomyositis (polymyositis accompanied by skin rash) are characterized by inflammation of connective tissue and muscle fibers and muscle fiber necrosis. Cell-mediated and humoral immune factors have been implicated. Treatment with immunosuppressive agents is effective in many cases.
    • The most common toxic myopathy is caused by alcohol abuse. Direct toxic effects of alcohol-producing necrosis of muscle fibers and nutritional deficiency have been suggested. The only treatment is abstinence and improved nutrition. The toxic effects of many drugs on muscle fibers cause local trauma to the muscle fibers caused by direct effects of the needle, secondary infection, and changes caused by non-physiologic acidity and alkalinity in the fibers.
  5. Musculoskeletal Tumors
    • Sarcomas of muscle tissue are rare. Rhabdomyosarcoma has uniformly poor prognosis because of an aggressive invasion and early, widespread dissemination. The usually treatment include surgical excision, radiation therapy, and systemic chemotherapy.
    • Bone tumors originate from bone cells, cartilage cells, fibrous tissue cells, or vascular marrow cells. Each cell produces a specific type of ground substance that is used to classify the tumor as osteogenic (bone cell), chondrogenic (cartilage cell), collagenic (fibrous tissue cell, or myelogenic (vascular marrow cell). Malignant bone tumors are usually large, aggressively destroy surrounding bone, invade surrounding tissue, and initiate independent growth outside the site of origin. Benign bone tumors are less destructive, limit their growth to the anatomic confines of the bone, and have a well-demarcated border.