extension (eks-ten´shun)

1. The act of bringing the distal portion of a joint in continuity (though only parallel) with the long axis of the proximal portion. 2. A pulling or dragging force exerted on a limb in a distal direction. 3. Obsolete term for traction. [L. extensio, to stretch out]
Buck's e. apparatus for applying longitudinal skin traction on the leg through contact between the skin and adhesive tape; friction between the tape and skin permits application of force, which is applied through a cord over a pulley, suspending a weight; elevation of the foot of the bed allows the body to act as a counterweight.Buck's traction;
nail e. an obsolete method of e., by a weight on a nail or pin in the distal fragment of a fracture.
primer e. a technique for determining the 5´-untranslated region of a specific mRNA molecule. Uses an oligonucleotide complementary to the known RNA sequence as a primer for cDNA synthesis via reverse transcriptase.
ridge e. an intraoral surgical operation for deepening the labial, buccal, and/or lingual sulci; it is performed to increase the intraoral height of the alveolar ridge in order to assist denture retention.
skeletal e. skeletal traction


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