Surgical knife

A surgical instrument for operating percutaneously in a living body comprising:

• an elongated hollow handle,
• a shaft having a proximal portion extending within and secured, during use, to said handle and a distal portion extending distally of said handle,
• surgical cutting means fixedly supported during use by the distal end of said shaft,
• a slidable tubular sheath having a distal portion extending distally of said handle, about said shaft, to the region of said cutting means, said sheath sized and constructed for introduction into the living body through a puncture opening in its flesh,
• means for moving said sheath axially relative to said handle between a first position in which the distal portion of said sheath surrounds said cutting means, enabling safe positioning of said instrument in the body without cutting, and a second, retracted position exposing said surgical cutting means, the position of said cutting means relative to said handle being fixed during movement of said sheath, and
• a proximal cap removably connected to said handle, said sheath and said handle defining an elongated passage extending axially the length of said instrument, and said shaft and said cutting means being sized relative to said passage through said sheath and said handle whereby, upon disassembly of said cap from said handle, said shaft and blade are adapted for removal proximally through said passage, while said sheath remains in said puncture opening in the flesh of the living body.