Methods and devices for soft tissue dissection

Abstract

Methods and devices for blunt dissection include a differential dissecting instrument (DDI) comprising a rotary drive train having a distal end configured to be pointed substantially at a complex tissue and a proximal end pointed substantially at, and associated with, a mounting base. The DDI comprises a drive wheel possessing an axis of wheel rotation coaxial with a central, longitudinal axis of the rotary drive train, the drive wheel located distally to, and rotated by, the rotary drive train. The drive wheel comprises a drive point located at a non-zero radius from the axis of wheel rotation. The DDI also comprises a differential dissecting member rotatably mounted distally to the drive wheel and having an axis of member rotational oscillation.

We claim: 
     
         1 . A differential dissecting instrument for differentially dissecting complex tissue comprising:
 a rotary drive train, having a central, longitudinal axis;   a distal end of the rotary drive train substantially pointed at a complex tissue, and a proximal end of the rotary drive train substantially pointed at, and associated with, a mounting base;   a drive wheel, possessing an axis of wheel rotation coaxial with the central, longitudinal axis of the rotary drive train, located distally to, and rotated by, the rotary drive train;   a drive point located at a non-zero radius from the axis of wheel rotation; and   a differential dissecting member rotatably mounted distally to the drive wheel, the differential dissecting member having an axis of member rotational oscillation.   
     
     
         2 . The differential dissecting instrument of  claim 1 , wherein the differential dissecting member comprises:
 at least one tissue-engaging surface substantially pointed at the complex tissue;   a torque-point disposed proximally to the axis of member rotational oscillation of the differential dissecting member, and operably associated with the drive point, such that the torque-point travels rotatably around the central, longitudinal axis; and   a motion filter operably connecting the differential dissecting member and the torque-point, and further permitting only a planar component of the rotatable travel of the torque-point to actuate the differential dissecting member, thus driving the differential dissecting member in planar rotary oscillation about the axis of member rotational oscillation;   wherein the rotary drive train rotates the drive wheel, which rotates the torque-point, which transmits oscillatory planar motion to the differential dissecting member around the axis of wheel rotation, thereby causing the at least one tissue-engaging surface to move in at least one direction against the complex tissue, and   wherein the at least one tissue-engaging surface is configured to selectively engage the complex tissue such that when the differential dissecting member is pressed distally along a forward tunneling axis into the complex tissue, the at least one tissue-engaging surface moves across the complex tissue and the at least one tissue-engaging surface disrupts at least one soft tissue in the complex tissue, but does not disrupt firm tissue in the complex tissue.   
     
     
         3 . The differential dissecting instrument of  claim 2 , wherein the motion filter is a substantially flat, elastic member. 
     
     
         4 . The differential dissecting instrument of  claim 3 , wherein the substantially flat, elastic member is a steel leaf spring. 
     
     
         5 . The differential dissecting instrument of  claim 3 , wherein the substantially flat, elastic member is formed out of a same material as, and is unitary with, the differential dissecting member. 
     
     
         6 . The differential dissecting instrument of  claim 2 , wherein the motion filter is comprised of a substantially flat plate operably connected by a hinge joint to the differential dissecting member. 
     
     
         7 . The differential dissecting instrument of  claim 6 , wherein the hinge joint is further provided with a spring. 
     
     
         8 . The differential dissecting instrument of  claim 1 , wherein the rotary drive train comprises at least one rotary electric motor possessing a driveshaft defining an axis of motor rotation. 
     
     
         9 . The differential dissecting instrument of  claim 8 , wherein the rotary drive train further comprises a gearhead operably connecting the at least one rotary electric motor to the drive wheel. 
     
     
         10 . The differential dissecting instrument of  claim 8 , wherein the rotary drive train further comprises a plurality of motors operably associated in a coaxial fashion, forming an elongate differential dissecting attachment for differentially dissecting the complex tissue. 
     
     
         11 . The differential dissecting instrument of  claim 10 , wherein the plurality of motors are rotationally phase-locked. 
     
     
         12 . The differential dissecting instrument of  claim 11 , wherein each of the plurality of motors has a respective driveshaft, and the driveshaft of each of the plurality of motors is connected to one another by a respective universal joint, each universal joint being torsionally rigid about the driveshaft and possessing a center of bending articulation, thus maintaining mutually rotationally phase-locked status of each of the plurality of motors even though one or more driveshafts may deviate from a parallel relationship to one another. 
     
     
         13 . The differential dissecting instrument of  claim 10 , further comprising a cover, the cover configured to surround, protect, and support components of the rotary drive train. 
     
     
         14 . The differential dissecting instrument of  claim 13 , further comprising a plurality of cover segments, wherein each motor of the plurality of motors possesses its own cover. 
     
     
         15 . The differential dissecting instrument of  claim 14 , wherein the plurality of cover segments are articulated with one other, permitting the elongate differential dissecting attachment for differentially dissecting the complex tissue to bend in an arbitrary fashion while each of the plurality of motors is rotating. 
     
     
         16 . The differential dissecting instrument of  claim 1 , further comprising an elastic sheath providing a smooth, compliant surface to a patient's tissues. 
     
     
         17 . The differential dissecting instrument of  claim 1 , wherein the torque-point comprises a ball, and the drive point comprises a socket. 
     
     
         18 . The differential dissecting instrument of  claim 17 , wherein either the ball or the socket is further fitted with a roller bearing. 
     
     
         19 . The differential dissecting instrument of  claim 15 , wherein a degree of bending of the elongate differential dissecting attachment is controlled. 
     
     
         20 . The differential dissecting instrument of  claim 19 , wherein a degree of bending between each of the plurality of motors is controlled. 
     
     
         21 . The differential dissecting instrument of  claim 20 , wherein the elongate differential dissecting attachment is longitudinally incompressible, allowing the entire differential dissecting instrument to be pushed forward from the proximal end, moving distally into a patient's tissues. 
     
     
         22 . The differential dissecting instrument of  claim 20 , wherein the elongate differential dissecting instrument is longitudinally stiff in tension, allowing the entire differential dissecting instrument to be either pulled forward from the distal end, moving distally into a patient's tissues, or pulled backward out of the patient's tissues from the proximal end. 
     
     
         23 . The differential dissecting instrument of  claim 1 , wherein rotational motion of the rotary drive train can be varied at will, permitting arbitrary, non-sinusoidal planar motion of the differential dissecting member. 
     
     
         24 . The differential dissecting instrument of  claim 23 , wherein the differential dissecting member is configured to differentially dissect a patient's tissue in a direction of dissection that can be operatively directed off-center. 
     
     
         25 . The differential dissecting instrument of  claim 24 , wherein the differential dissecting instrument is configured to dissect an arbitrary path through the patient's tissue. 
     
     
         26 . The differential dissecting instrument of  claim 15 , wherein the differential dissecting instrument is configured to provide operator control of a degree of bending of at least a distal-most segment of the elongate differential dissecting attachment. 
     
     
         27 . The differential dissecting instrument of  claim 26 , wherein the differential dissecting instrument is configured to differentially dissect tissue in a direction of dissection, and wherein the differential dissecting instrument is further configured to provide independent control of both rotational motion of the rotary drive train and a degree of bending of the at least the distal-most segment of the elongate differential dissecting attachment, such that the direction of dissection is not coaxial with a longitudinal axis of the elongate differential dissecting attachment. 
     
     
         28 . The differential dissecting instrument of  claim 27 , wherein the differential dissecting instrument is configured to provide asymmetrical motion which changes the direction of dissection, thus permitting an operator to arbitrarily steer the differential dissecting instrument.