In various surgical procedures, it is necessary to dissect bone or other tissue. Many conventional surgical instruments used for the dissection of bone or other tissue employ pneumatic or electrical motors to rotate a cutting element. In their most basic form, such surgical instruments comprise a motor portion having a rotary shaft, a dissection tool having a cutting or abrading element that is rotated by the rotating shaft of the motor, and a coupling arrangement for connecting the dissection tool to a spindle or collet of the rotary shaft. The spindle or collet of the rotary shaft is usually housed within a base that is attached to the motor.
Because it is frequently necessary to replace the dissection tool, it is also known in the art to use a quick release coupling to secure the dissection tool to the surgical instrument. An example of such a quick release coupling is shown and described in commonly assigned U.S. Pat. No. 5,505,737 entitled “Quick Release Coupling For A Dissecting Tool.” The coupling device shown in U.S. Pat. No. 5,505,737 includes a spindle attachment which is secured to a spindle of a surgical instrument. The spindle attachment has a shaft engagement portion for engaging a shaft of the dissection tool. The shaft engagement portion of the spindle attachment is provided with apertures that terminate within a central bore of the engagement portion through which the shaft of the dissection tool extends.
Surrounding the spindle attachment is a cylindrical sleeve having a contact surface that engages several spherical locking members located within the apertures of the shaft engagement portion of the spindle attachment. A sleeve engagement member is coupled to the base of the surgical instrument and is movable between retracted and extended positions.
As the sleeve engagement member is moved between the retracted and extended positions, it causes the sleeve of the surgical instrument to be moved between an engaged and disengaged position with respect to the dissection tool. When the sleeve is moved to the engaged position, the contact surface of the sleeve forces the spherical locking members inward toward the central bore of the spindle attachment where the locking members contact the shaft of the dissection tool, thereby preventing removal of the dissection tool from the surgical instrument. When the sleeve is moved to the disengaged position in which the spherical locking members are allowed to retract within the apertures, the dissection tool is able to be removed from the socket.
While known surgical tools including replaceable dissection tools have proven to be acceptable for their intended applications, it remains desirable to further advance the pertinent art. For example, due to the high speed rotating action of the dissection tool, a need exists in the art for more precise alignment of the dissection tool within the surgical instrument. Further, in past designs, the coupling mechanism has not included means to limit the acceptance of non-approved tool shafts. Specifically, non-approved or qualified tool shafts may suffer from a number of problems. End users may improperly select a tool shaft of the incorrect strength for a given length, select the incorrect diameter, or attempt to utilize the incorrect cutting head configuration based on the motor design. Such variations in the tool shaft can result in damage to the motor coupling assembly and supporting bearings in the attachment housing, result in extreme cutting tip flail at high speed potentially causing injury to a patient and stressing the tool shaft with the possibility for breakage. Additionally, a need exists in the pertinent art for an improved surgical tool which permits telescoping of the dissection tool relative to a fixed sleeve.