A medical device (2) comprising an elongated needle assembly (4) having a distal end (6), a proximal end (8) and a longitudinal axis A, the needle assembly comprises a tubular cannula (10) having a sharpened distal end (12), a proximal cannula portion (14), and a longitudinal bore (16) along the longitudinal axis A, a stylet (18) configured to extend through the bore (16) of the cannula (10), and having a blunt distal end (20) and a proximal stylet portion (22). The needle assembly (4) is provided with a spring member (24) configured to urge the stylet in a distal direction along the longitudinal axis, such that the stylet is axially spring-biased in said distal direction. The medical device further comprises a connecting member (26) configured to detachably attach said stylet (18) to said cannula (10), wherein said stylet (18) is configured to be attached to the tubular cannula (10) by the connecting member (26) such the blunt distal end (20) protrudes just beyond the sharpened distal end (12) of the cannula (10) when no force is applied to the distal end of the stylet in a proximal direction along said longitudinal axis, and wherein the connecting member (26) is configured to enable detachment of the proximal portions (14, 22) from each other such that the stylet (18) may be withdrawn from the longitudinal bore (16).L'invention concerne un dispositif médical comprenant un ensemble aiguille allongé ayant une extrémité distale, une extrémité proximale et un axe longitudinal A, l'ensemble aiguille comprend une canule tubulaire ayant une extrémité distale aiguisée, une partie canule proximale, et un alésage longitudinal le long de l'axe longitudinal A, et un stylet conçu pour s'étendre à travers l'alésage de la canule, et ayant une extrémité distale émoussée et une partie stylet proximale. L'ensemble aiguille comprend un élément de ressort conçu pour pousser le stylet dans une direction distale le long de l'axe longitudinal, de telle sorte que le stylet est sollic
