Shape-memory alloy clip for bone fractures - is made from nickel@-titanium@ alloy, and is in form of staple with two branches having contact zones and connection piece

摘要

Retaining piece for holding together two pieces of bone (20a, 20b) separated by a fracture (25) is formed from a metal having an austenite/martensite transition temp. close to ambient. The piece comprises an active section (1), between the contact zones (2a, 3a) of the bone, having a primary austenitic structure which takes a secondary martensitic structure by thermo-elastic transition, such that the distance between the contact zones (2a, 3a) is greater in the secondary form than the primary form. Separation is compensated by constant progression along length of one contact zone (2a) towards the other (3a) in direction parallel to active section (1) and inducing relative local deformation of less than 8%. Deformation between primary and secondary structures is 2-6%. Metal used is stoichiometric Nickel/Titanium alloy. Secondary form is rigid at low temp. or maintained at ambient temp. by external constraints. The clip is in the form of a staple with two branches (2, 3) having contact zones (2a, 3a) and connection piece (1). The primary form of the connection piece (1) is undulated in a plane perpendicular to the plane of the branches (2, 3). Secondary form of connection piece is straight. Branches (2, 3) are straight and normal to connection piece (1). Retaining is via either branches (2, 3) having curves with convex section turned towards fracture (25), or, in an alternative form, by extension of active section (1) into curved branches in primary structure. USE/ADVANTAGE - Nickel-titanium alloy has appropriate transition temp. and is bio-compatible. Simple operation. Immediate use or low temp. storage.