these proteoglycans (which are usually aggrecan) bind via a link protein to hyaluronic acid to form a proteoglycan aggregate.
– place plates on the tension side of fractures because they are loaded best in tension and can act as tension band system.
– forged cobalt chrome is stronger than cast cobalt chrome
– fatigue failure of a metal implant occurs with cyclic loading past the endurance limit, which is usually in the elastic range, not plastic range.
– titanium has a lower modulus of elasticity than cobalt chrome. It is less resistant to surface wear, making it a poor bearing surface. The histiocytic response to titanium is apparently less than for cobalt chrome.
– ossification of the embryo begins between 7 and 12 weeks.
– PTH is synthesized and secreted by the chief cells of the parathyroid gland.
– 1, 25 dihydroxyvitamin D (and 24,25 dihydroxyvitamin D) is made in the proximal tubule of the kidney
– 25 hidroxyvitamin D is made in the liver
– Vitamin D facilitates production of calcium binding protein in the intestinal mucosa – increases intestinal absorption of calcium.
– in stored blood, factor VIII is negligible at 72 hours, factor V by 3-5 days.
– massive transfusion with citrated blood – will cause hypocalcemia which can cause cardiac arrhythmias; hyperkalemia can result from broken down blood cells, but more common to have hypocalcemia.
– stress is defined as force/unit area (it is not the same measurement as load)
– disc degeneration; in the young adult – nucleus is 85% water, and the annulus is 78% water. The water content of both falls to about 70% with aging. This is largely due to changes in the proteoglycan and collagen network.
– warfarin acts to inhibit the production of vitamin K-dependent clotting factors – II, VII, IX, X. Metronidazole, septra, and cimetidine all prolong the PT by interacting with warfarin.
– methylmethacrylate monomer may have a direct effect on cardiac system (cardiodepressant); as the cement is mixed, it increases in volume about 3-5%; as the monomer polymerizes, the volume decreases 5-7%.
– malignant hyperthermia is caused by a uncontrolled release of calcium in the skeletal muscles from the sarcoplasmic reticulum.