irreversible acetylation of COX leading to inhibition of thromboxane-A2 synthesis
heparins mechanism (IV, unfrac, and LMHW)
Enhances ability of ATIII to inhibit factors IIa, III, Xa
vitamin K 2,3-epoxide reductase prevents reduction of vitamin K epoxide back to active vitamin K
vitamin K is needed for gamma-carboxylation of glutamic acid for factors II (prothrombin), VII (first affected), IX, X
protein C, protein S
indirect factor Xa inhibitor
Sterilization by irradiation significantly decreases the structural and mechanical properties of an allograft at what dosage?
What complication is significantly more common among octogenarians who undergo concomitant bilateral total knee arthroplasty than those who undergo unilateral total knee arthroplasty?
CHF (Mayo data)
Following total hip arthroplasty, patients with Parkinson's disease would be expected to attain equivalent results to patients without neuromuscular disorders in which of the following clinical areas?
Rate of aseptic loosening
-higher rates of (postop medical complications, reoperation, dislocation, periop mortality)
part of the extrinsic coagulation pathway
Thromboplastin release activates Factor VII which activates Factor X which converts prothrombin to thrombin. Thrombin is the catalyst for converting fibrinogen to fibrin which induces clot formation
2 supplements effects blood clotting through its effect on platelets
Ginkgo and ginseng
inhibitory effects of platelet function
transient osteoporosis of the hip
usually a self-limited condition that is most frequently seen in women in the third trimester of pregnancy and in men in the sixth decade of life. Transient osteoporosis is best treated nonsurgically with protected weight bearing and anti-inflammatory drugs. The natural history is that of self-resolution
Adhesive wear definition
Adhesive wear occurs when 2 surfaces are forced together under a load experience motion. When the
adhesive forces exceed the material strength, material is removed from the weaker material. Adhesive
wear is the most common mechanism seen in well-functioning hips.
Abrasive wear definition
Abrasive wear occurs under 2 modes:
two-body and three-body abrasive wear. Two-body abrasive wear occurs when asperites or projections
from 1 surface remove material from the opposed articulating surface. This is seen with a roughened or
damaged surface such as a scratched femoral head. Three-body wear occurs when a third body particle is
interposed between the bearing surfaces and results in removal of material from 1 or both of the articular
Delamination is a type of surface damage seen with oxidized polyethylene. Delamination is
frequently seen in knees as a result of crossing wear patterns and high-contact stresses.
Fatigue wear definition
Fatigue wear occurs when surface and subsurface cyclic shear stresses or strains in the softer material of an articulation
exceed the fatigue limit for that material.
UHMWPE is a long polyethylene polymer with a high molecular weight. It is manufactured via ram bar
extrusion and compression molding. Radiation is used to sterilize and cross-link. Historically, gamma
was irradiated in air at 2.5-4.0 Mrad. This created free radicals, resulting in early oxidative degradation
with high wear rates, delamination, and fracture. Modern UHMWPE is highly cross-linked with higher
doses of radiation (5.0-10 Mrad) in an inert environment. The level of radiation directly increases the
amount of cross-linking and also improves wear resistance via cross-linking. Free radicals are still
generated during the radiation process and are quenched by either remelting or annealing.
Remelting is the heating of the polyethylene above its melt point, changing it from the partial crystalline state to the
amorphous state and removing all free radicals, but also reducing wear characteristics.
In annealing, the UHMWPE is heated below the melting point, which avoids the reduction in crystallinity but leaves more