OrthoNet

MCQs-Basic 5
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.