Medical screwdriver
View Patent ↗A medical screwdriver configured to avoid disengaging from a screw during implantation of the screw at a surgical site, the screwdriver including an outer shaft having a housing in which is located a piston and a spring, an inner shaft, and a collar. When the collar is rotated in a first direction the collar is positioned at a first position and the inner shaft is rotationally coupled to the outer shaft. When the collar is rotated in a second direction opposite the first direction, the collar moves to a second position and the inner shaft is unlocked from the outer shaft.
1. A medical screwdriver configured to avoid disengaging from a screw during implantation of the screw at a surgical site, the screwdriver comprising:
an outer shaft having a distal end configured to engage a head of the screw, a housing defined at an opposite proximal end of the shaft, and a central bore extending through the length of the outer shaft, the housing including a cavity located to intersect the central bore;
a spring positioned within the cavity;
a piston positioned within the cavity of the housing of the outer shaft, the piston having an end extending outwardly of the cavity, an opposite base in contact with the spring, and a bore extending through the piston, the bore including an interior projection;
an inner shaft having a distal end configured for drivingly engaging a corresponding drive surface of the screw, an opposite proximal end, and a toothed circumferential surface located between the ends of the shaft, the inner shaft being positioned within the central bore of the outer shaft and passing through the bore of the piston and located so that the toothed surface of the inner shaft is proximate the bore of the piston for permitting selective engagement of the interior projection of the piston with the toothed surface of the inner shaft; and
a collar rotatably positioned on the housing of the outer shalt and rotatable between a first position and a second position, the collar including a sidewall and an interior profiled cam located along an interior portion of the sidewall, the cam including first and second cam surfaces;
wherein, when the collar is rotated in a first direction the collar is positioned at the first position with the first cam surface adjacent the piston and the first cam surface provides sufficient clearance for the piston so that the piston is positioned with the interior projection of the piston in engagement with the toothed circumferential surface of the inner shaft and the spring forces the piston to maintain such engagement of the piston and the inner shaft so that the inner shaft is rotationally coupled to the outer shaft, and wherein when the collar is rotated in a second direction opposite the first direction, the collar is positioned at the second position and the piston is engaged by the second cam surface of the collar to overcome force supplied by the spring and position the piston so that the interior projection of the piston is disengaged from the toothed circumferential surface of the inner shaft and the inner shaft is not rotationally coupled to the outer shaft.
2. The screwdriver of claim 1 , further comprising an exterior sleeve surrounding a portion of the outer shaft.
3. The screwdriver of claim 1 , wherein the head of the screw is tulip-shaped and includes internal threads and the outer shaft includes a threaded end configured to threadably engage the threads of the tulip-shaped head.
4. The screwdriver of claim 1 , wherein the outer shaft includes a pair of stop surfaces, one of which is contacted by the collar to transfer rotation of the collar in the first direction to the outer shaft, and the other of one of which is contacted by the collar to transfer rotation of the collar in the second direction to the outer shaft.