| inorganic compound | A compound in which the atoms or radicals consist of elements other than carbon and are typically held together by electrostatic forces rather than by covalent bonds; often are capable of dissociation into ions in polar solvents (e.g., H2O). Compare: organic compound. (05 Mar 2000) |
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| isocyclic compound | Any compound in which the constituent atoms, or any part of them, form a ring. Used mainly in organic chemistry where: 1) numerous compound's contain rings of carbon atoms (carbocyclic compound's) or carbon atoms plus one or more atoms of other types (heterocyclic compound's), usually nitrogen, oxygen, or sulfur; 2) where the atoms in the ring are all of the same element (homocyclic or isocyclic compound); 3) where the ring is saturated or contains nonconjugated double bonds (alicyclic compound), the compound is similar in properties to the corresponding acyclic compound (e.g., cyclohexane resembles hexane); 4) where the ring contains conjugated double bonds in a closed loop in which there are 4n + 2 (where n is an integer) delocalised π electrons (Huckel's rule) (aromatic compound; e.g., benzene, pyridine), it is more stable than the corresponding saturated ring and exhibits unusual chemical properties characteristic of itself and not of other types of rings or of acyclic compound's. These aromatic compounds have the ability to sustain an induced ring current. Synonym: closed chain compound, ring compound. (05 Mar 2000) |
| open chain compound | An organic compound in which the chain does not form a ring. Synonym: aliphatic compound, open chain compound. (05 Mar 2000) |
| organic compound | <chemistry> A compound containing carbon. (11 Jan 1998) |
| lens, compound | <microscopy> A lens composed of two or more separate pieces of glass or other optical maternal. These component pieces or elements may or may not be cemented together. A common form of compound lens is a two-element objective, one element being a converging lens of crown glass and the other a diverging lens of flint glass. The combination of suitable glasses or other optical materials (plastics, minerals) properly ground and polished reduces aberrations normally present in a single lens. (05 Aug 1998) |
| apophysial fracture | Separation of apophysis from bone. (05 Mar 2000) |
| articular fracture | A fracture involving the joint surface of a bone. (05 Mar 2000) |
| atlas fracture | <radiology> Incidence: 4% of cervical spine injuries, site: posterior arch, anterior arch, massa lateralis, Jefferson fracture associated with: fractures of C7 (25%), fractures of C2 pedicle (15%), extraspinal fractures (58%) (12 Dec 1998) |
| avulsion fracture | A fracture that occurs when a joint capsule, ligament, or muscle insertion of origin is pulled from the bone as a result of a sprain dislocation or strong contracture of the muscle against resistance; as the soft tissue is pulled away from the bone, a fragment or fragments of the bone may come away with it. (05 Mar 2000) |
| axis fracture | <radiology> Incidence: 6% of cervical spine injuries, associated with atlas fractures in 8%, hyperflexion injury: odontoid fracture, type I avulsion of tip of odontoid (5-8%) difficult to detect, type II fracture through base of dens (54-67%) complication: nonunion, type III subdental injury (30-33%) prognosis: good, Differential diagnosis: os odontoideum, ossiculum terminale, hypoplasia/aplasia of dens, hyperextension injury: hangman's fracture (12 Dec 1998) |
| barton fracture | <radiology> Intra-articular fracture of distal radius, dorsal displacement of separated fragment, due to fall on outstretched hand see: wrist fractures (12 Dec 1998) |
| Barton's fracture | Fracture of the distal radius with dislocation of the radiocarpal joint. (05 Mar 2000) |
| basal skull fracture | <orthopaedics> A fracture involving the base of the cranium. This fracture is often difficult to detect clinically. Findings may include raccoon eyes, Battle's sign, haemotympanum and cerebrospinal fluid rhinorrhoea. Plain skull X-ray will often not reveal the basal skull fracture, making a CT scan or MRI the most reliable diagnostic investigation. (15 Nov 1997) |
| bending fracture | <orthopaedics, radiology> An injury in which a long bone or bones, usually the radius and ulna, are bent due to multiple microfractures, none of which can be seen by X-ray imaging. (14 Aug 2000) |
| bennett fracture | <radiology> Mechanism: forced abduction of thumb, findings: intraarticular fracture/dislocation of the base of the 1st metacarpal at the ulnar aspect, small fragment of metacarpal continues to articulate with the trapezium, lateral retraction of metacarpal shaft by abductor pollicis longus, difficult to keep in anatomical alignment, complication: pseudoarthrosis, better prognosis than Rolando fracture see: thumb fractures (12 Dec 1998) |