Medical retriever device

Claim 1

In a medical retriever device sized and adapted for use through the working channel of an endoscope for removing stones and the like from the kidneys, ureter or biliary duct, said device comprising an elongated, narrow sheath, a basket of relatively large diameter extendible from the distal end of said sheath and collapsible when withdrawn into said sheath, said basket defined by a multiplicity of spaced apart, outwardly bowed spring arms which extend generally axially of said sheath and are joined at respective distal and proximal ends of said basket, and remote means to project, retract and rotate said basket relative to the distal end of said sheath, the improvement wherein said basket has a generally bulbous form adjacent its distal end, the maximum diameter of said basket being spaced from the distal end of said basket a distance of equal to between about one quarter and one third the overall length of said basket. said bulbous form defined by a set of generally flat spring strips, first portions of said generally flat spring strips closely adjacent the distal extremity of said basket lying at an angle close to the axis of said basket in a manner to facilitate collapse of said basket during withdrawal into said sheath, and second portions of said strips proximal of said first strip portions extending outwardly of the first strip portions, and having a curved shape comprised sequentially of oppositely directed arcs, the ratio of radial to circumferential dimensions of the material of said strips of said basket being between about 1:2 and 1:4, at least two of said strips at the distal extremity of said basket being disposed face to face and joined together in a manner contributing stiffness to said bulbous end of said basket.