System and method for attaching a surgical instrument to a patient's bone

1. A surgical instrument system, comprising:

a bone fixation pin including a head and a shaft extending from the head to a distal end having a plurality of threads defined therein, and

a surgical instrument configured for use with the bone fixation pin, the surgical instrument comprising:

an elongated shaft defining a longitudinal axis extending through its proximal end and its distal end, a socket defined in the distal end of the elongated shaft, the socket being sized to receive the head of the bone fixation pin, and a shank extending outwardly from the proximal end of the elongated shaft along the longitudinal axis, the shank being configured to engage a surgical drill to rotate the elongated shaft about the longitudinal axis,

a sheath extending over the distal end of the elongated shaft, and

a locking mechanism coupled to the elongated shaft,

wherein the elongated shaft and the shank are configured to move along the longitudinal axis relative to the sheath, and the locking mechanism is operable to permit selectively movement of the elongated shaft and the shank along the longitudinal axis relative to the sheath,

wherein the locking mechanism includes a body that is positioned in a slot extending diametrically through the elongated shaft and a locking tab that extends outwardly from the body and is moveable between a locked position in which the locking tab is positioned in an opening of the sheath to prevent movement of the elongated shaft within the sheath and an unlocked position in which the locking tab is spaced apart from the opening while being coupled to the elongated shaft to permit movement of the elongated shaft within the sheath,

wherein: (i) the sheath includes a distal opening defined in its distal end and a central passageway that extends inwardly from the distal opening, (ii) the elongated shaft is positioned in the central passageway of the sheath, and (iii) when the elongated shaft is moved in a first direction relative to the sheath, the distal end of the elongated shaft is moved along the central passageway toward the distal end of the sheath,

wherein (i) the head of the bone fixation pin extends from a proximal end of the bone fixation pin to a distal edge, the threads of the shaft extend from the distal end to a proximal edge, and a first distance is defined between the distal edge of the head and the proximal edge of the threads, and (ii) when the elongated shaft is located in a first position relative to the sheath, a second distance is defined between the distal opening of the sheath and the distal end of the elongated shaft, the second distance being greater than the first distance such that a number of the threads of the bone fixation pin are positioned in the central passageway of the sheath when the head of the bone fixation pin is fully seated in the socket of the elongated shaft,

wherein the elongated shaft is moveable to a second position in which a third distance is defined between the opening of the sheath and the distal end of the elongated shaft, the third distance being less than the first distance, and

wherein (i) the locking mechanism is biased in the locked position in which the elongated shaft is prevented from moving relative to the sheath when the elongated shaft is in the first position, and (ii) when the locking mechanism is in the unlocked position, the elongated shaft is permitted to move relative to the sheath to move the elongated shaft between the first position and the second position;

wherein the body includes a biasing element that biases the locking tab radially outward in the opening in the locked position and allows the body to be radially compressed in the slot for the tab to disengage and be spaced apart from the opening in the unlocked position.

2. The surgical instrument system of claim 1 , wherein the slot defined in the elongated shaft extends longitudinally through the elongated shaft.

3. The surgical instrument system of claim 1 , wherein:

the body includes a first end engaged with an inner surface of the sheath, and

when the locking tab is in the locked position, a second end of the body is engaged with a distal-facing surface of the elongated shaft, and when the locking tab is in the unlocked position, the second end of the body is disengaged from the distal-facing surface of the elongated shaft.

4. The surgical instrument system of claim 3 , wherein the first end of the body is received in a groove defined in the inner surface of the sheath.

5. The surgical instrument system of claim 1 , wherein the elongated shaft includes a pair of tabs extending outwardly from its proximal end and the sheath includes a pair of guide slots that receive the pair of tabs, the guide slots and the tabs cooperating to prevent rotational movement about the longitudinal axis.

6. The surgical instrument system of claim 1 , wherein the socket and the head of the bone fixation pin have corresponding triangular cross sections.