fixation

1. The condition of being firmly attached or set. 2. In histology, the rapid killing of tissue elements and their preservation and hardening to retain as nearly as possible the same relations they had in the living body. SYN: fixing. 3. In chemistry, the conversion of a gas into solid or liquid form by chemical reactions, with or without the help of living tissue. 4. In psychoanalysis, the quality of being firmly attached to a particular person or object or period in one's development. 5. In physiologic optics, the coordinated positioning and accommodation of both eyes that results in bringing or maintaining a sharp image of a stationary or moving object on the fovea of each eye. [L. figo, pp. fixus, to fix, fasten]

- ammonia f. SYN: ammonia assimilation.

- bifoveal f. SYN: binocular f..

- binocular f. a condition in which both eyes are simultaneously directed to the same target. SYN: bifoveal f..

- circumalveolar f. stabilization of a fracture segment or surgical splint by wire passed through and around the dental alveolar process.

- circummandibular f. stabilization of a fracture segment or surgical splint by wire passed around the mandible.

- circumzygomatic f. stabilization of a fracture segment or surgical splint by wire passed around the zygomatic arch.

- complement f. f. of complement in a serum by an antigen-antibody combination whereby it is rendered unavailable to complete a reaction in a second antigen-antibody combination for which complement is necessary; the second system usually serves as an indicator (red blood cells plus specific hemolysin); if complement is fixed with the first antigen-antibody union, hemolysis does not occur, but, if complement is not so removed, it causes hemolysis in the second system; this technique is the basis for complement f. tests, which are widely used in laboratories for the detection of antigens or antibodies. SEE ALSO: Bordet-Gengou phenomenon, Wassermann test. SYN: CF test, complement binding assay.

- craniofacial f. stabilization of facial fractures to the cranial base by direct wiring or by external skeletal pin f..

- crossed f. in convergent strabismus, the use of the right inturned eye to look at objects to the left and the left inturned eye to look at objects to the right, in order to avoid ocular rotation.

- eccentric f. a monocular condition in which the line of sight connects the object and an extrafoveal retinal area.

- elastic band f. the stabilization of fractured segments of the jaws by means of intermaxillary elastics applied to splints or appliances.

- external f. f. of fractured bones by splints, plastic dressings, or transfixion pins.

- external pin f. in oral surgery, stabilization of fractures of the mandible, maxilla, or zygoma by pins or screws drilled into the bony part through the overlying skin and connected by a metal bar.

- external pin f., biphase pin f. by replacing the rigid metal bar connector with an acrylic bar adapted at the time of reduction of the fracture.

- freudian f. f. (4).

- genetic f. the increase of the frequency of a gene by genetic drift until no other allele is preserved in a specific finite population.

- intermaxillary f. f. of fractures of the mandible or maxilla by applying elastic bands or stainless steel wire between the maxillary and mandibular arch bars or other types of splint. SYN: mandibulomaxillary f., maxillomandibular f..

- internal f. stabilization of fractured bony parts by direct f. to one another with surgical wires, screws, pins, rods, or plates. SYN: intraosseous f..

- intraosseous f. SYN: internal f..

- mandibulomaxillary f. SYN: intermaxillary f..

- maxillomandibular f. SYN: intermaxillary f..

- nasomandibular f. mandibular immobilization, especially for edentulous jaws, with maxillomandibular splints, attached by connecting a circum-mandibular wire with an intraoral interosseous wire passed through a hole drilled into the anterior nasal spine of the maxillae.

- nitrogen f. process in which atmospheric nitrogen is converted to ammonia.

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fix·a·tion fik-'sā-shən n

1) the act, process, or result of fixing, fixating, or becoming fixated: as

a) the act or an instance of focusing the eyes upon an object

b) a persistent concentration of libidinal energies upon objects characteristic of psychosexual stages of development preceding the genital stage

c) stereotyped behavior (as in response to frustration)

d) an obsessive or unhealthy preoccupation or attachment

2) the immobilization of the parts of a fractured bone esp. by the use of various metal attachments

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n.

1. (in psychoanalysis) a failure of psychological development, in which traumatic events prevent a child from progressing to the next developmental stage. This is said to be a cause of mental illness and of personality disorder. See also psychosexual development.

2. a procedure for the hardening and preservation of tissues or microorganisms to be examined under a microscope. Fixation kills the tissues and ensures that their original shape and structure are retained as closely as possible. It also prepares them for sectioning and staining. The specimens can be immersed in a chemical fixative or subjected to freeze drying.

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fix·a·tion (fik-saґshən) [L. fixatio] 1. the act or operation of holding, suturing, or fastening in a fixed position. 2. the condition of being held in a fixed position. 3. in psychiatry, a term with two related meanings: (a) arrest of development at a particular stage, which if temporary is a normal reaction to difficulties but if continued is a cause of emotional problems; and (b) a close and suffocating attachment to another person, especially a childhood figure, such as a parent. Both meanings are derived from psychoanalytic theory and refer to “fixation” of libidinal energy either in a specific erogenous zone, hence fixation at the oral, anal, or phallic stage, or in a specific object, hence mother or father fixation. 4. the use of a fixative (q.v.) to preserve histological or cytological specimens. 5. in chemistry, the process whereby a substance is removed from the gaseous or solution phase and localized, as in carbon dioxide fixation or nitrogen fixation. 5. in ophthalmology, direction of the gaze so that the visual image of the object falls on the fovea centralis. 6. in film processing, the chemical removal of all undeveloped salts of the film emulsion, leaving only the developed silver to form a permanent image.