(19)

(11)

EP 0 493 570 A1

(12)

(43) Date of publication: 08.07.1992 Bulletin 1992/28 (21) Application number: 91913369.0 (22) Date of filing: 23.07.1991

(51) International Patent Classification (IPC):  A61B 17/ 58( . ) A61B 17/ 17( . ) (86) International application number: PCT/GB1991/001235 (87) International publication number: WO 1992/001422 (06.02.1992 Gazette 1992/04)

(84) Designated Contracting States: CH DE FR GB LI (30) Priority: 24.07.1990 GB 19900016205 (71) Applicant: BRITISH TECHNOLOGY GROUP LIMITED London SE1 6BU (GB)	(72) Inventor: CHADWICK, Christopher, John Queensgate, Halifax HX3 0DH (GB) (74) Representative: Hulse, Thomas Arnold  Hulse & Co. Eagle Star House, Carver Street Sheffield S1 4FP Sheffield S1 4FP (GB)