Patent ID: 7156815

Claim:
A soft tissue biopsy instrument comprising: (a) a housing member comprising a generally hollow handle partitioned into first and second compartments, the housing member having a closed distal end and a closed proximal end, there being an aperture through the distal end; (b) a tubular cannula defining a lumen and having a tubular hub affixed to a proximal end of said cannula and a beveled, tissue piercing distal end, the cannula extending though said aperture; (c) a stylet adapted to be slidably inserted and removed from the lumen of the cannula, the stylet having a slide member affixed to a proximal end thereof and a sharpened distal end, the stylet further including a notch of a predetermined length and depth formed proximal of said sharpened distal end, the slide member being reciprocally movable in a guideway formed in the housing member; (d) first and second helically wound compression springs individually disposed in said first and second compartments, the first spring operatively disposed between the housing and slide member on the proximal end of the stylet and the second spring operatively disposed between the housing and the tubular hub on the proximal end of the cannula; (e) a cocking assembly slidably mounted on the housing operatively coupled to the first and second springs for compressing the springs while simultaneously retracting the cannula and the stylet in a proximal direction in a series of discrete steps of a predetermined length without exposing the notch out from the lumen of the tubular cannula; (f) means coupled to the cocking assembly for reducing a force needed to compress the first and second springs; and (g) a release button for sequentially releasing energy stored in the first and second springs to first drive the stylet in a distal direction and then drive the cannula in a distal direction whereby a tissue specimen of a selectable length is captured in the notch of the stylet.