Surgical Cutting Instrument

The present invention relates to a surgical cutting instrument, and more particularly, to a surgical cutting instrument capable of, while being inserted into a body cavity, particularly a joint cavity of the knee, for example, performing a easy and reliable cutting and evacuating operation of a cartilage, bone, fibrous tissue, tumor or the like.

A conventional operation of a joint generally employs an incision method (open surgery). By way of example, a commonly used operation of the knee such as to remove a tumor on the patella or to excise a damaged cartilage or a bone from the knee joint requires a large incision of an epithelium. Consequently, the operation is attended with a trauma by the incision. Thus, the trauma will cause pain and limitations of movement. Furthermore, a considerable time is required for recovery from the trauma.

Accordingly, there has recently been proposed an instrument in which under observation with an arthroscope (endoscope) a small perforation is provided on an epithelium without incising the knee epithelium and an operation is effected inserting a probe into the perforation (closed surgery). For instance, such instruments are disclosed in U.S. Pat. No. 4,203,444 and U.S. Pat. No. 4,246,902.

The prior art instrument disclosed in U.S. Pat. No. 4,203,444 comprises an elongate external stationary tube defining a side-facing, axially extending shaving port on the periphery of the external tube, an internal tube which is rotatably mounted within the external tube and defines an internal, rotary blade at the shaving port, a suction apparatus and a drive motor. The instrument severs tissue or the like by rotating the rotary blade with the drive motor and draws shavings by suction to remove them through the internal member.

With the conventional instrument of the above construction, since in the shaving port, an outer cutting edge is formed on the inner periphery of the external tube and the rotary blade forms an inner cutting edge, it is difficult to take steady aim at a tissue to be cut and a bite between the outer and the inner cutting edges is not good. In addition, since the cutting operation is effected only after a tissue to be cut is drawn in the shaving port of the external tube by means of the suction apparatus, it is difficult to cut a tissue such as a cartilage or a bone. To rotate the internal tube forming a suction channel therein, a rotary shaft passes through the suction channel and therefore cut or shaved tissue is not smoothly sucked and withdrawn.

The prior art instrument disclosed in U.S. Pat. No. 4,246,902 comprises a probe-like outer, elongate member having a distal end with a cutting aperture in a side wall thereof, an inner cutting member which is slidably disposed within the outer member and has a distal end defining a cutting edge positioned at said distal end of the outer member, a suction apparatus and a drive mechanism for the inner cutting member. The instrument cuts a tissue to be cut which is drawn by suction in the cutting aperture by reciprocation of the inner cutting member and then the cut tissue is sucked and evacuated. The instrument thus constructed, however, has disadvantages as indicated in the former prior art, also. Specifically, since the inner cutting member which is disposed within the outer member forms an inner cutting edge, it is difficult to take steady aim at a tissue to be cut and a bite between the outer member and the inner cutting edge is not good. In addition, it is difficult to cut a comparatively hard tissue such as a cartilage or bone. Since the inner cutting member is slidably disposed within a suction channel passage, cut tissue is not smoothly sucked and withdrawn.

It is an object of the invention to provide a surgical cutting instrument which comprises an outer sheath tube having an open distal end, an inner stationary tube which is disposed within the outer sheath tube in such a manner that a closed distal end of the inner tube projects from the open distal end of the outer tube, a cutting opening for drawing tissue chips which is provided on the peripheral wall of the projected distal end portion of the inner tube to form an inner cutting edge at the edge of the cutting opening, a suction passage for cut tissue chips which is provided within the inner stationary tube acting as a suction tube and communicating with the cutting opening, and a sliding member which is disposed between the inner periphery of the outer tube and the outer periphery of the inner stationary tube so as to be slidable in the axial direction and to close and open the cutting opening of the inner stationary tube and which is provided with an outer cutting edge which engages the inner cutting edge at the distal end of the sliding member.

According to the invention, the arrangement in which the inner cutting edge is formed at the edge of the cutting opening on the outer periphery of the inner stationary tube and the outer cutting edge is formed on the sliding member which reciprocates on the outer periphery of the inner stationary tube makes it easy to take accurate aim at a tissue to be cut or shaved and to improve the bite of the tissue between the outer and the inner cutting edges so that escape of the tissue is avoided. Thus, the cutting and shaving operation can be assured.

Since no other member such as a rotary shaft passes through the suction passage and the suction passage body itself does not reciprocate or rotate, cut or shaved tissue chips can be smoothly sucked and evacuated.

In addition, since the cutting opening for drawing tissue is provided at an easily visible position on the distal end of the instrument, it is possible to easily take accurate aim at a tissue to be removed. Thus, the cutting operation is reliably limited to merely the affected tissue to be cut or shaved.

FIG. 1 is a cross-sectional view of essential parts of one embodiment of a surgical cutting instrument according to the invention;

FIGS. 2(A) to 2(D) are enlarged plan views of essential parts of respective examples of cutting openings for withdrawing tissue in the surgical cutting instrument shown in FIG. 1;

FIG. 3 is a cross-sectional view taken on line III--III in FIG. 1;

FIG. 4 is a plan view illustrating essential parts of a drive mechanism for a sliding member shown in FIG. 1; and

FIG. 5 is a schematic view illustrating an example of the set-up for performing the joint operation using the surgical cutting instrument shown in FIG. 1.

Referring now to FIG. 1, a surgical cutting instrument 1 according to one embodiment of the invention comprises a grip 2 at its proximal side and an elongate inserter 3 forwardly extending from the grip 2 (left in FIG. 1) and is inserted into a body cavity, particularly the joint cavity. The inserter 3 comprises an outer sheath tube 4 which has its open distal and proximal ends, the latter of which ends is secured to the distal end of the grip 2, an inner stationary tube 5 which is disposed within the outer sheath tube 4 such that a closed distal end of the inner tube 5 projects from the open distal end of the outer sheath tube 4 and a sliding member 7 which is in a close sliding fit between the inner periphery of the outer sheath tube 4 and the outer periphery of the inner tube 5 so as to be axially slidable.

The inner tube 5 is provided with a cutting opening 8 for drawing tissue on the outer periphery of the distal end of the inner tube 5 which projects from the distal end of the outer sheath tube 4 and an inner cutting edge 9 is defined on the edge of the cutting opening 8. In addition, the inner tube 5 forms a suction channel 10 for withdrawing cut tissue chips passing through the inner tube communicating with the cutting opening 8 and the proximal end of the inner tube 5 is secured to a stationary member 11 which is fitted into the grip 2. The stationary member 11 has a passage 12 communicating with the suction channel 10 and the passage 12 further communicates with a fitting 13 which is threadably fitted into the stationary member 11 on the outer periphery of the grip 2. The fitting 13, as shown in FIG. 5, communicates with a suction and discharge apparatus 15 through a tube 14 whose one end is connected to the fitting 13 and the other end is connected to the suction and discharge apparatus 15. The cutting opening 8 of the inner tube 5 has a shape as shown in FIGS. 2(A) to 2(D), for example. The cutting opening 8 of FIG. 2(A) is in an axially elongated square shape. The cutting opening 8A of FIG. 2(B) is in a circumferentially extended square form and has the advantage that the extent of projection of the distal end of the inner tube 5 from the distal end of the outer sheath tube 4 can be reduced. The cutting opening 8B of FIG. 2(C) is in a triangular shape whose front side is the base. The cutting opening 8C of FIG. 2(D) is in a triangular shape whose pointed end is the vertex.

Turning to FIG. 1, the sliding member 7 is formed of a tube the distal end of which is provided with an outer cutting edge 16 which engages the inner cutting edge 9 of the cutting opening 8 and closes the cutting opening 8 when moved forwardly and opens the cutting opening 8 when moved backwardly. The proximal end of the sliding member 7 is inserted into a hollow chamber 2a of the grip 2 and is connected to a drive transmitter 17 which is disposed within the hollow chamber 2a. The drive transmitter 17 includes an output shaft 19 of a drive motor 18 and a cylindrical cam 21 having a circumferentially extended and longitudinally inclined cam groove 20 on the outer periphery of the cam 21. The output shaft 19 and the cam 21 are engaged each other by a spline 19a of the shaft 19 and a spline 22a of the cam 21. In addition, a fixed cam guide pin 23 is fitted into the cam groove 20 so that the cam 21 can be rotatably and slidably moved along the cam groove 21 A slidable shaft 25 is inserted into a rotary center hole 24 provided on the front of the cam 21 to prevent the shaft 25 from coming out and to be rotatably journaled. The slidable shaft 25, as best shown in FIG. 4, has two forked shafts 25a, 25b which respectively pass through through-holes 26, 26 (see FIG. 3) which are axially provided at the right and left positions of the stationary member 11. The distal ends of the forked shafts 25a, 25b are secured to a slidable attachment 27 which is disposed at the proximal end of the inner tube 5 so as to be axially slidable within the hollow chamber 2a. The slidable attachment 27 to which the proximal end of the sliding member 7 is secured is moved back and forth so that the sliding member 7 can be integrally and axially moved with the slidable attachment 27.

The drive motor 18 is electrically connected to a monitor controller 29 (see FIG. 5) through a cable 28 which is extended from the grip 2. The revolution of the motor 18 is controlled by a current, voltage or frequency employing an on-off or a speed controller with an at hand switch provided on the grip 2.

The operation of the surgical cutting instrument 1 of the invention will be explained with reference to FIG. 5. To cut a body region to be excised such as tissue of the knee joint, a small perforation into which the inserter 3 of the instrument 1 is inserted is provided on the knee 30 by a puncture operation as by a trocar. The inserter 3 is then inserted into the joint cavity directly or through a trocar. Prior to the insertion of the inserter 3, an inserter 32 of an arthroscope 31 in which an illumination and observation optical system is disposed is inserted into the joint cavity by a puncture operation as by a trocar so as to permit the cutting operation of tissue to be excised to be effected under observation of the inside of the joint cavity. The inside of the joint cavity and the inserter 3 inserted thereinto can be made observable by an eyepiece of the arthroscope 31 directly or through a display 34 which displays a visual image of a television camera 33 mounted on the eyepiece. Furthermore, to facilitate the cutting operation by inflating the inside of the joint cavity, a physiological solution of sodium chloride is supplied from a solution supplier 35 into the joint cavity with a controlled pressure through a water supply tube 36 which is inserted into the joint cavity. On the other hand, the tube 14 is connected to the fitting 13 on the grip 2 and is further connected to the suction and discharge apparatus 15. A connector (not shown) of the cable 28 is connected to the motor controller 29 to supply a power to the motor 18.

Under these circumstances, an operator takes a step to render the cutting opening 8 bear against tissue to be cut observing the inside of the joint cavity and the distal end of the inserter 3 with an arthroscope or the display 34 to introduce the tissue into the cutting opening 8. Under this condition, a switch is turned on to drive the motor 18. The drive force of the motor 18 actuates the sliding member 7 to axially and slidingly reciprocate it through the drive transmitter 17 so that the outer cutting edge 16 engages the inner cutting edge 9 of the cutting opening 8 to cut or shave the tissue introduced in the cutting opening 8. The tissue chips thus cut are discharged into the suction and discharge apparatus 15 by suction through the suction channel 10, communicating passage 12 of the inner tube 11, fitting 13 and tube 14 activating the suction and discharge apparatus 15 when necessary or normally.

A means for converting the rotary force of the motor to the reciprocating motion to move the sliding member 7 back and forth may be not only the means of the aforesaid embodiment but also one of other various well known means. In addition, in the aforesaid embodiment, the sliding member 7 is illustrated by a tubular body but may be formed with a tubular body merely at the distal end portion of the sliding member 7 on which the outer cutting edge 16 is defined. Alternatively, the sliding member 7 need not be in a tubular shape when it has such width and shape that the distal end portion of the sliding member 7 can close the cutting opening 8. Furthermore, the proximal side of the sliding member 7 may be in any of a tubular, ring and plate shapes.

In the surgical cutting instrument of the invention, the cross sectional form of the inserter 3 may be in any of a circular, elliptic, rectangular and triangular shapes. The sliding member 7 may be reciprocated axially with a manual operation (means for moving the sliding member back and forth by a cruciform handle, a lever or the like). It is to be noted that surgical cutting instrument of the invention can be applied to not only the excising operation of tissue of the joint cavity but also that of another body cavity.