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127 Cards in this Set
- Front
- Back
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Virchow’s Triad
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Endothelial damage, hypercoagulability, stasis
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Thrombin role
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converts fibrinogen to fibrin (meshwork holding RBC’s together) - both normal clotting and DVT
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Protein C and Protein S
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anti clotting
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Most common hypercoagulability condition
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Factor V Leiden
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Hemophilia A
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Low factor VIII
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Role of ultrasound in DVT
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OK below inguinal ligament and above popliteal vessels
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Pulm embolism W/U
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ABG, EKG to r/o MI, CXR, and ultimately VQ or CT PA or pulmonary angiogram
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What minimizes DVT aside from anticoagulants
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regional anesthesia,
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Does CPM help prevent DVT?
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No
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Acceptable DVT prophy in normal patient
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Warfarin, Heparin, LMWH, Fondaparinux
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Acceptable DVT prophy in patient w/ high bleeding risk
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Aspirin
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Warfarin
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prevents Vit K carboxylation; Factors 2,7,9,10; antidote Vit K, FFP
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What happens in Hep Induced Thrombocytopenia?
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reaction to platelet factor 4 causing platelet loss, LMWH does not have platelet factor 4
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LMWH
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blocks factor Xa and IIa; protamine will deactivate; use after 12-24 hours to avoid hematoma
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Fondaparinux
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blocks factor Xa only; no known antidote;
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Hirudins
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Thrombin IIa inhibitor; antibodies can develop with long term use
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Aspirin
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irreversibly binds COX in platelets
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Length of DVT prophy in Total Hip
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up to 35 days
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Fat emboli Syndrome- clinical findings
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Petechial rash upper part of body, neurologic symptoms, pulmonary collapse (ARDS); CXR: snowstorm; often after asymptomatic interval
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Fat emboli Syndrome- treatment
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prophylaxis by early long bone stabilization; ventilation with PEEP
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Malignant Hyperthermia
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ranitidine recept defect on the sarcoplastm reticulum; sustained Ca release contractions; Muscle damage releases myoglobin; classic finding is increased end tidat CO2
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Syndromes at high risk for Malignant Hyperthermia
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Muscular dystrophy, OI, Arthrogryposis
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Treatment Malignant Hyperthermia
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Dantrolene
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Signs of poor nutrition
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Albumin < 3.5; Total lymphocytes < 1500
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Type of bacteria in gas gangrene
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Anaerobic gram pos rod; Clostridium perfringes; Abx Pen G, Clindamycine, Ceftriaxone
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Superantigens
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M protein (Strep pyog) ; TSS toxin-1 (S. aureus)- leads to massive immune respone (T-cell mediated)
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Human bite organism
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Eikenella corodens (Tx: Augmentin)
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Cat bite organism
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Pasteurella multocida (Tx: Augmentin or cefoxitin)
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Marine injury organism
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Mycobacterium marinum; if you suspect- they need to grow in cool culture for a long period of disease
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Lyme disease organism
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Spirochete- Borrelia Burgdorferi; Vector is tick- Ixode Ricinus; 60% intermittent monoarthritis; Tx: 3-6 wks doxy
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Most sensitive and specific tests for osteomyelitis in children
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Sensitive: CRP; Specific: sub-periosteal or bone aspiration
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Involucrum vs Sequestrum
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Involucrum: reactive living bone around a... Sequestrum: floating dead bone inside involucrum
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Empiric Abx if suspecting osteo in child
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Nafcillin, Clindamycin, or Cefazolin
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Organism in Brody’s abscess
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S. aureus
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Most common bone infection in sickle cell
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S. aureus; also prone to salmonella; Tx: salmonella: third generation cephalosporin
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Triple Abx Tuberculosis
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Isoniazid, Rifampin, Ethambutol (x 12 months)
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Cell analysis indicative of septic joint
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Cells > 50K with increased PMNs
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# cause of septic arthritis in sexually active young adults
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Neisseria Gonorhoeae; Tx: Ceftriaxone
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Acute versus chronic Paronychia
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S. aureus in acute; chronic is Candida Albicans- treat non-operatively. Common in dishwashers
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RIsk of single stick transmission HIV and Hep C
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about 3% for both
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Anisotropic
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mechanical properties are different depending on the direction of stress
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Screw dimensions: Pitch, Lead, Root diameter, outer diameter
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Pitch: distance between streads; Root diameter (shank), Outer diameter (diameter of threads)
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Load bearing versus Load sharing
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Plates: Load bearing; IMN : Load sharing
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Rigidity of nail increases by
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radius to the 4th power
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ex-fix rigidity
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different planes, near-near/far-far; thicker pins, thicker bar, bars closer to the bone, more pins, more bars
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Coefficient of Friction in healthy human joints
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0.002 - 0.04 (vs > 0.05 in prosthetic implants)
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How much does cane ambulation decrease contra-lateral hip reaction force?
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60%
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Patello-femoral stess highest during which activity?
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Running (7 x body weight); stairs (3 x body weight)
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Knee fusion position
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10 degrees flexion; 7-8 degrees valgus
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Creep
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deformity with time for constant force
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Shoulder motion- GH vs ST
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Glenohumeral (120 degrees) Scapulothoracic (60 deg); 2:1 ratio
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Elbow arthrodesis position
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90 degrees flexion; if Bilateral, do one at 110 and one at 60.
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wrist joint axial load distribution
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80% radius, 20%ulna
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viscoelastic material
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mechanical properties are different at different rates of loading
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Isotropic
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mechanical properties are the same, independent of which direction the load is applied
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Doubling thickness of plate increases bending thickness by how much?
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8X
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Bone is strongest in:
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compression; weakest in shear
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Immune response to metallic implants is typically what type?
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Type IV (delayed type hypersensitivity reaction); NOT IgE mediated
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Where do you see woven bone?
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fracture callus, infection, malignancy; random organization of osteocytes- not stress oriented
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Wolff’s Law
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bone remodels in response to the stress it experiences.
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What bone cell is responsive to PTH
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Osteoblasts which then releases messenger to stimulate osteoclasts
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1,25 dihydroxy vitamin D
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stimulates matrix, alk phos synthesis
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Describe activity of osteocytes
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maintain bone; mechanosensing and control extra-cellular concentration of calcium and phosphorous; directly stimulated by calcitonin and PTH; communicate through canaliculi
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Osteoblast vs osteoclast origin
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Osteoblasts come from osteo-progenitor cells; osteoclasts crome from monocytes
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How do osteoclasts resorb bone?
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Howships lacunae; ruffled border- carbon dioxide is converted to carbonic acid by carbonic anhydrase (non-functional in osteopetrosis); carbonic acid pumped across ruffled border by ATP-dependent pumps
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Stain for osteoclasts
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tartrate-resistant acid phosphatase
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What cell has receptos for calcitonin and PTH
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PTH = osteoblasts; calcitonin = osteoclasts
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Hydroxyapetite formula
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Ca 10 (PO4)6 OH2 - 60% of dry weight of bone
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Most abundant non-collagenous protein in bone
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osteocalcin = produced by osteoblasts; regulates bone density (inhibited by PTH)
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Adhesive proteins in bone matrix
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Fibronectin (osteoblast adhesion to bone); vitronectin (osteoclast adhesion to bone)
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Wolff’s vs Hueter-Volkmann
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Wolffs = bone goes where the stress is; Hueter-Volkmann = bone growth related to stress (Blounts)
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Inner layer of periosteum
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Cambium layer: has osteoblastic progenitor cells and is responsible for thickening of bones in children
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Enchondral bone formation
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ossification of secondary ossification centers (epiphyseal cartilage); fracture callus; longitudinal growth through physis
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Layers of physis
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Reserve zone - proliferative zone (increased oxygen tension inhibits calcification) - hypertrophic zone <maturation - degeneration - calcification >
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In what zone of physis is type X collagen
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Hypertrophic zone (Schmid’s chondrodysplasia)
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Intramembranous ossification examples
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flat bones; distraction osteogenesis
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Continuum of events in fracture repair
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Inflammation (bleeding w/ fibrin clot, etc); soft callus fibrocartilage w/in 2 weeks); hard callus (by enchondral ossification) Remodeling (Wolff’s)
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BMP function
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undifferentiated mesenchymal cell- leads to differentiation into osteoblasts
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Osteoconductive vs inductive vs osteogenic
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conductive = scaffold; inductive = BMP, TGF-beta; genic = has osteocytes/osteoblasts
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How long for heterotopic ossification maturity before resection?
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24-48 months; when it shows that it is matured (may be able to use bone scan to determine)
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How much of body’s Ca is in bone?
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99%
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Ca absorption and resorption
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Active absoprtion in duodenum, resorption in kidney; mediated by activated vit D
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Ca supplement per day
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1300 mg/day for adolescent/young adults; 750 mg/day for pre-menopausal adults; post-menopausal 1500mg/day; breast-feeding 2000mg/day
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PTH vs 1,25 OH2 vit D effect of Ca ad Po4 serum concentration
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Vit D increases Ca, decreases PO4; vit D increases both Ca and PO4
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What cells have PTH receptors
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kidney (proximal tubule to activate vit D, increases resorption Ca, excretion PO4), osteoblasts (which in-turn will stimulate osteoclasts)
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What cells have 1,25 OH vit D receptors
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duodenum (increased absorption of Ca and Phos);
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Chief cells- what do they do?
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releases PTH in response to low Ca; inhibited by elevated Ca and 1,25 OH vit D
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what stimulates vit D activation
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if high PTH, low Ca or low PO4 in serum, kidney will convert it to active form by 1-alpha-hydroxylase to 1,25 OH vit D
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1-alpha hydroxylase
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in kidney to convert vit D to active form
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Calcitonin function
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stimlates osteoclasts;
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Other factors which lead to decreased bone density?
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Corticosteroids and thyroid
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Growth hormone and mineral metabolism?
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increased Ca absorption in stomach, increased serum Ca, increased bone density
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Markers of bone resorption
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Urinary hydroxyproline and pyridinoline cross links
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Hypercalcemia symptoms
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Bones, stones, abdominal moans and psychiatric overtones
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Primary hyperparathyroidism: describe labs
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Net increase in plasma Ca, decrease in plasma PO4; Labs: increased serum Ca and vit D (due to low PO4); increased urinary PO4
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Loop diuretics and Calcium
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Loop diuretics decrease urinary resorption of Ca
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Pseudohypoparathyroidism: describe labs
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target cell resistance to PTH; labs: decreased active vit D, leading to decreased calcium, high phos,
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Renal osteodystrophy: describe labs
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inability for kidneys to excrete phosphorus leads to high phosphorus , which decreases serum Ca leading to secondary hyperparathyroidism
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Area of the physis in Rickets
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zone of provisional calcification
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Calcium deficiency rickets: describe labs
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low Ca, low Pi; reactive high 1,25 vit D and PTH; despite high absorption Pi (vit D mediated), high Pi excretion (PTH mediated)
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vit D deficient rickets: describe labs
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Type I pseudo vitamin D deficiency
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1-alpha-hydroxylase enzyme deficiency; treatment is 1,25 OH vit D
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Type II pseudo vitamin D deficiency
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receptor insensitivity to 1,25 OH vit D
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Familial hypophosphatemic rickets: describe labs
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decesed serum phos; low 1,25 OH vit D <<given low serum phos, should have reactive increase in active vit D>>
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Hypophosphatasia: describe labs
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decreased alkaline phosphatase
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Z vs T score
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Z score is comparison to age-matched; T score is comparison to 25 year old
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Bisphosphonate mechanism of action
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inhibit osteoclastic ruffled border
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When to treat osteoporosis?
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T score worse than -2.5; any osteoporotic fracture; treating osteopenia not clearly indicated
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Issue with growth hormone and rickets?
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inability to calcify hypertrophic zone
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Motor unit
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motor nerve; motor end plate where Ach is released, which binds to muscle membrane; calcium then released from sarcoplasmic reticulum
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What part of sarcomere is Ca sensitive
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Troponin (induces conversion to tropomysine and crossbridges)
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Isotonic contraction
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constant weight, but length of muscle changes (dumbells)
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Eccentric contracture
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muscle lengthens during contraction
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Isometric contraction
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muscle length remains constant; resistance changes (pushing against a wall)
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Isokinetic contraction
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lengthening or shortening of muscle during contraction at a constant speed (isokinetic)
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isokinetic eccentric exercise
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most efficient for strengthening muscle
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Fast twitch vs slow twitch
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Fast twitch = sprinters (white fibers); slow twitch = endurance (red fibers)
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Plyometrics
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eccentric stretch followed by powerful concentric contraction
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neuropraxia
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selevtive demylenation
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neurotmesis
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axonotmesis
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Demyelinating neuropathies: conduction velocity
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<40 mm/sec upper extremity; <30 mm/sec lower extremity.
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Myopathies
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Fibrillations and sharp waves early on EMG, late fasciculations (sign of denervation)
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Sharpey’s fibers
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mineralized fibrocartilage where tendons insert into bone
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Paratenon covered tendons- describe
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well vascularized, not sheathed; extensor tendons, achilles
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Sheathed tendon blood supply
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vinculae; with watershed areas (flexor tendon)
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Time-dependent strength of repaired tendon
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weakest at 7-10 days, maximum strength 6 months
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