Musculoskeletal

• what happens when RANK on osteoclast binds to RANKL? what is OPG?

  RANK binds to RANKL -> increased osteoclast differentiation and activation

  OPG - RANKL antagonist

  balance between RANKL and OPG determines bone loss and formation
• describe compartment syndrome

  rise in pressure in and around an injury, limiting blood flow and oxygen to those tissues

  causes - trauma, broken bone, bruised muscle, severe sprain, cast or bandage too tight, loss of blood due to tourniquet use

  complications - muscle ischemia, compartment tamponade, neural injury, Volkmann contracture, may lead to muscle infarction (crush syndrome)
• describe rhabdomyolysis

  causes - medication, trauma, ischemia, overexertion, infection, electrical shock

  patho - muscle cell infarction with cell lysis; myoglobin release into circulation transported to kidneys, obstructing renal tubules -> renal failure

  s/s - muscle pain, weakness, reddish brown urine, hyperkalemia, acidosis, hyperphosphatemia

  outcomes - kidney failure (release of myoglobin), DIC

  tx - identify and treat cause -> IV fluids, electrolytes, dialysis
• describe osteomyelitis

  bone infection

  sources - exogenous (contamination, extension from contagious site) or endogenous (hematogenous)

  s/s - local bone pain and swelling, drainage, loss of movement, fever, malaise, increased WBCs
• describe pathophysiology, differentiating features of chronic osteomyelitis & why it's difficult to treat?

  initial infection -> inflammatory response -> abscess formation -> disruption of blood supply -> sequestrum (dead bone) -> involucrum can develop (new bone formation)

  chronic - present for several months to years, necrotic bone

  difficult tx - difficulty of immune cells or antibiotics accessing the site, damaged microcirculation
• describe bone tumors

  s/s - pain, mass, impaired function

  benign - limited to bone, well-defined edges, compress or displace normal bone, may not require treatment

  malignant - rapid growth, ill-defined edges, extend beyond the bone

  often develops during adolescence since this is when most bodies go through growth spurt
• describe metastatic bone disease

  common sites - ribs, spine, femur, pelvis

  s/s - pain, pathologic fractures, elevated alkaline phosphatase and calcium

  dx - CT, bone scan
• describe osteoporosis

  decreased bone density and mineralization due to altered RANK, RANKL, OPG system

  risk factors - age, postmenopausal females, caucasian or asian women, decreased physical activity, insufficient calcium and vitamin D intake, excessive caffeine, excessive alcoholic drinks, smoking, medications, certain diseases

  most affected - spine, vertebrae, femoral neck, hip

  s/s - fractures, kyphosis, loss of height
• describe osteomalacia (rickets)

  inadequate mineralization of bone

  causes - vitamin D deficiency, GI disease, renal disease

  s/s - bone pain, tenderness, pathologic fractures, deformity (kyphosis, bowed legs)
• describe paget disease

  progressive disorder with excessive destruction and disorganized repair of bone

  patho - increased bone resorption -> disorderly bone formation -> thickened and enlarged bones with weak matrices

  most affected - skull, vertebrae, pelvis

  dx - xrays, bone scan, increased alkaline phosphatase

  s/s - often asymptomatic, bone pain, headache, vertigo, tinnitus, kyphosis, bowed legs, waddling gait, peripheral neuropathy
• describe osteoarthritis

  degenerative loss of cartilage

  patho - injury to cartilage -> inflammation -> release of enzymes and proteases -> breakdown of cartilage

  s/s - joint pain, stiffness, swelling, limited ROM, crepitus, joint effusions, unstable and deformed joints
• describe rheumatoid arthritis

  inflammatory destruction of cartilage, hyperplasia of synovial tissue (autoimmune)

  patho - inflammation of synovial membrane due to T cells and immune complexes -> inflammatory response and release of inflammatory mediators -> damage to joint

  s/s - painful, stiff, swollen, tender, warm joints; symmetrical joint involvement, deformity

  other tissue involvement - malaise, fatigue, low grade fever, rheumatic nodules, vasculitis, splenomegaly, lymph node enlargement
• describe gout

  causes - primary (overproduction or decreased elimination of uric acid) or secondary (CKD, hyperuricemia (tumor cell lysis), diuretics)

  uric acid crystal deposits in joints

  patho - high uric acid levels -> crystal formation in connective tissue and synovial joints -> inflammation -> pain and destruction of joint cartilage and bone

  most affected - toe, ankle, and knee joints

  s/s - red, swollen, painful joints, tophi
• what are contractures?

  shortening of connective tissue, muscle, tendons, or ligaments due to scarring, disuse, or muscle weakness