# Patent

## Title
Remote center positioner

## Abstract

The invention is directed to a remote center positioner used to support an instrument and provide a center of spherical rotation, remote from any bearings or mechanical supports, at a desired location of the instrument. The remote center positioner is particularly useful in laparoscopic surgery to constrain a surgical instrument to move around a fixed center of rotation remote from any bearings or mechanical supports and coincident with an entry incision in the abdominal wall.

## Background
CROSS-REFERENCES TO RELATED APPLICATIONS
This application is a divisional of U.S. application Ser. No. 10/133,206, filed on Apr. 26, 2002, now U.S. Pat. No. 6,758,843, which is a continuation of U.S. application Ser. No. 09/568,089, filed May 9, 2000, now U.S. Pat. No. 6,406,472, which is a continuation of U.S. application Ser. No. 09/149,828, filed Sep. 8, 1998, now U.S. Pat. No. 6,106,511, which is a continuation of U.S. application Ser. No. 08/504,620, filed Jul. 20, 1995, now U.S. Pat. No. 5,817,084, which is a continuation of U.S. application Ser. No. 08/298,550, filed Aug. 30, 1994, now abandoned, which is a divisional of U.S. application Ser. No. 08/062,404, filed May 14, 1993, now abandoned, the full disclosures of which are incorporated herein by reference.


STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
This invention was made with Government support under contract awarded by the National Institute for Health (NIH) under grant number 5R01GM-44902-02. The Government has certain rights in this invention.


BACKGROUND OF THE INVENTION
The present invention is directed to a remote center positioner used to support an instrument and provide a center of spherical rotation, remote from any bearings or mechanical supports, at a desired location of the instrument. Specifically, the remote center positioner is useful in laparoscopic surgery to constrain a surgical instrument to move around a fixed center of rotation remote from any bearings or mechanical supports and coincident with an entry incision in the patient's abdominal wall.
In standard laparoscopic abdominal surgery, the patient's abdomen is insufflated with gas, and cannulas are passed through small (approximately 1⁄2 inch) incisions to provide entry ports for laparoscopic surgical instruments. The laparoscopic surgical instruments generally include an laparoscope for viewing the surgical field, and working tools such as clamps, graspers, scissors, staplers, and needle holders. The working tools are similar to those used in conventional (open) surgery, except that the working end of each-tool is separated from its handle by an approximately 12-inch long extension tube. To perform surgical procedures the surgeon passes instruments through the cannulas and manipulates them inside the abdomen by sliding them in and out through the cannulas, rotating them in the cannulas, and “levering” (pivoting) them around centers of rotation approximately defined by the incisions in the muscles of the abdominal wall. The abdominal incisions do not provide stable reference positions or points of rotation, and so in order to maintain accurate positional control of an instrument during manipulation, the surgeon may need to manually constrain it to pivot around a fixed point coincident with the incision. Manual support of the pivot point is particularly important when the surgeon manipulates laparoscopes or other heavy instruments. Mechanical clamping devices' are used to support the instruments in fixed orientations, but these devices do not provide a remote center of rotation for positioning the instruments.
In robotically assisted and telerobotic laparoscopic abdominal surgery the position of the surgical instruments is controlled by servo motors rather than directly by hand or with fixed clamps. With servo control, a means must be provided to ensure that the surgical instrument is constrained to move around a fixed center of rotation coincident with an entry incision in the patient's abdominal wall. Any other types of motion such as translation or rotation about other centers could cause patient injury.
Heretofore, there have been mechanisms directed to providing assistance in surgery. Thus, U.S. Pat. No. 4,756,655 to Jameson is directed to a manipulating mechanism having a control handle adapted to be positioned freely in three dimensions, a fixture for supporting a tool to be positioned, a linkage system which causes the end of the tool to move in the same direction as the control handle and a support structure. The linkage system includes a first linkage connected between the control handle and an effective ball-and-socket joint and a second linkage connected between the effective ball and socket joint and the fixture. Each linkage includes four link members rotatably connected in a parallelogram and a gimbal connected to one of the link members for mounting the linkage from the support structure.
The linkage system includes a first linkage connected between the control handle and a joint and a second linkage connected between the first linkage and the fixture. In the preferred embodiments, the linkage system is comprised of two motion translation mechanisms connected in series through an effective ball-and-socket joint, where each translation mechanism is essentially a pantograph adapted for rotation with respect to the support structure about two perpendicular axes. The motion of the control handle induces oppositely (or similarly, depending on the embodiment) directed motion of the ball-and-socket point by means of one translation mechanism which in turn causes similarly directed motion of the tool by means of the second translation mechanism so that the motion of the tool is in the same direction as the motion of the control handle. The linkage system is directed to a master reflection system controlling a slave reflection mechanism and does not provide a remote center of spherical rotation.
U.S. Pat. No. 4,143,652 to Meier and Dbaly discloses a surgical retaining device for holding a surgical instrument in place, typically with hooks. The device includes a holder block for displaceably securing the surgical retaining device at a stationary object and at least one insert element into which there can be inserted and fixedly clamped the surgical instrument. Between the insert element and the holder block there is arranged a double-arm pivotable stand possessing an intermediate pin joint. The pivotable stand is connected at one end by means of a ball-and-socket joint at the insert element and at its other end by means of a further ball-and-socket joint with an overhang arm which can be fixedly clamped at random elevational and angular positions with respect to the holder block at the latter.
A paper given at the IEEE Engineering in Medicine and Biology Society 11th Annual International Conference in 1989 entitled SMOS: Stereotaxical Microtelemanipulator for Ocular Surgery shows a structure for use in ocular vitrectomy, and other medical fields such as radial keratotomy and plastic surgery. FIGS. 2 and 3 of the paper shows the mechanical structure of the SMOS. A carrier holds a rotatably mounted curved wrist. An instrument holder is movably mounted to the wrist for carrying an instrument or needle for working in the eye keeping the needle centered on the entrance aperture. This is described as realized in spherical coordinates in a reference whose zero point is the entrance aperture A. The mechanism creating these movements, which are in themselves the main actions of the vitrectomy operation, is called the wrist of the microtelemanipulator.
An article entitled “Robotic Surgery” in the March 1993 issue of IEEE Engineering in Medicine and Biology shows a motorized frame (FIG. 8) for use in prostate surgery. FIG. 8 shows a schematic layout of the main mechanical components of the device called SARP. The working envelope is small and can be flexibly constrained using mechanical stops to improve safety. The envelope is approximately the frustum of a cone. Several cones may be needed, depending on the size of the prostate, to remove the unwanted enlarged tissue from within the prostate.
The manual frame can only produce conical cavities because it is manually driven. However, the motorized frame is capable of producing both conical and barrel shape cavities. As a start, conical cavities are advocated to avoid moving along more than one axis at a time. Conical cavities are easy to produce using hot loop electrosurgery. Similar to the manual frame, a ring shape frame fitted with a diametrical arch is a carriage that carries the resectoscope. A C-shaped bracket fixed to the resectoscope helps ease the introduction of the motorized frame to the resectoscope. The axes are designed to be driven by motors. Back driving is possible when the servo action is disabled. Successive cuts are made by extending and retracting the cutting loop repeatedly and turning on the cutting current at the return stroke of the cutter. The ring moves to a new position for each cut. Several conical cavities can be resected from the prostate to relieve blockage. To achieve one or more of these conical cavities inside the prostate, the frame is fixed to a head travel so that it can move axially along the rotation axis of the ring axis.
None of the above-mentioned devices provide a light weight simple apparatus for providing a remote center of rotation for use in surgery with minimal obstruction of the surgical field as is disclosed and claimed herein.
BRIEF SUMMARY OF THE INVENTION
In a broad aspect an apparatus is provided for moving an instrument about a spherical center of rotation at a desired location of the instrument. A base support means is adapted to be fixedly mounted to a surface. First linkage means are pivotally mounted on the base support means for rotation about an axis. Holding means are provided for holding an instrument in a position so that the desired remote center of spherical rotation of the instrument lies on the axis of rotation of the first linkage means. A second linkage means is connected to the holding means and pivotally connected to the first linkage means so that the remote center of spherical rotation of the instrument is maintained at the desired location.
The present invention provides a device for providing a remote center of spherical rotation for an instrument. A pivot joint having an x-x axis of rotation has a first linkage having one end pivotally mounted thereon. The axis of rotation of the first linkage is normal to and intersects the x-x axis. The other end is remote from the pivot joint. A parallelogram linkage is provided with a driving end and a remote end. The parallelogram linkage includes two sets of two corresponding members pivotally connected in a parallelogram. The parallelogram linkage is located in a plane parallel with the first linkage and has the driving end pivotally connected to the remote end of the first linkage. A mounting means for an instrument extends from the remote end of the parallelogram linkage. The mounting means is adapted to position the axis of the instrument held thereby to intersect the x-x axis to provide a center of spherical rotation for the instrument at a desired location.
In a more specific aspect the invention provides a device for providing a remote center of spherical rotation for an instrument for conducting laparoscopic surgery including a base support means adapted to be fixedly mounted to a surface and a pivot plate pivotally mounted to the base support means and having a rotational axis thereabout. At least a pair of linkage elements are extended from the pivot plate in parallel plane relationship. One end of the linkage elements is pivotally mounted in spaced apart relationship to the pivot plate. A parallelogram linkage means is connected to the linkage elements and includes two sets of two corresponding link members pivotally connected in a parallelogram, one of the sets of two sets of the two corresponding link members adapted to remain always parallel to the rotational axis, one of the link members of the set of corresponding link members adopted to remain always parallel to the rotational axis being pivotally connected to both linkage elements, one of the linkage elements being pivotally connected to both link members adopted to remain always parallel to the rotational axis. The parallelogram linkage means has an operating end and a driving end. An instrument element extends from the operating end of the parallelogram linkage means for movement therewith. The instrument element intersects the rotational axis at the location on the element desired for the remote center of rotation.
The remote center positioner is useful in a variety of applications. For example, supporting a microscope or other instrument to scan over and inspect a spherical surface. Various tools or instruments (manually or robotically positioned) that are passed through narrow entry ports can be supported by the apparatus of the present invention. Other uses include robotically-assisted positioning of an laparoscope for laparoscopic surgery, with the user commanding the position and orientation of the laparoscope via digital speech recognition, foot-switches, head-tracking or eye-tracking devices; support of manually-positioned laparoscopes or other surgical instruments during laparoscopic surgery; and telerobotic manipulation of laparoscopic surgical instruments (laparoscopes and various working tools) in which the positions of the working end of the tools are under servo control, and follow the motions of a surgeon's hands as he manipulates input control devices at a location that may be remote from the patient. Position, force, and tactile feedback sensors may be employed to transmit position, force, and tactile sensations from the working tool tips back to the surgeon's hands as he operates the telerobotic system.
OBJECT OF THE INVENTION
A particular object of the present invention is to provide apparatus useful to support an instrument or the like and includes the ability to move the instrument to perform a variety of tasks while maintaining a center of spherical rotation at a desired location of the instrument. Additional objects and advantages of the present invention will become apparent from the description of the various embodiments thereof read in light of the attached drawings which are made part of this specification.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a elevation view of an embodiment of a remote center positioner;
FIG. 2 is an elevation view of the preferred embodiment of a remote center positioner,
FIG. 2a is an enlarged sectional view taken at section a—a of FIG. 2;
FIG. 3 is an end view of the preferred embodiment of the remote center position of FIG. 2;
FIG. 4 is a elevation view illustrating an embodiment of the remote center positioner in accordance with the invention having an adjustable center distance;
FIG. 5 is an elevation view illustrating a motor driven application of the remote center positioner in accordance with the present invention;
FIG. 6 is an elevation view illustrating a manual application of the remote center positioner in accordance with the present invention;
FIG. 7 is an elevation view of another embodiment of apparatus of the invention;
FIG. 7a is a sectional view taken at line a—a of FIG. 7;
FIG. 8 is an elevation view of another embodiment of apparatus or the invention; and
FIG. 8a is a sectional view taken at line a—a of FIG. 8.



DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is an elevation view of an embodiment of a remote center positioner in a basic form in accordance with the present invention. A first linkage means is indicated generally by the numeral 21 and a second linkage in the form of a parallelogram is indicated by the numeral 23. The first linkage means is pivotally mounted on a base plate for rotation about an x-x axis. The second linkage means is pivotally connected to the first linkage means and is adapted to move in a plane parallel to the first linkage. Five link members (including extensions thereof), 11, 12, 13, 14, and 15 are connected together with pivot joints 16–20. A portion of element 13 extends beyond pivot 20 of the parallelogram linkage. The parallelogram linkage has an operating end at link member 13 and a driving end at link member 12. The elongated element 13 may, as desired later, carry a surgical instrument or other device. The pivot joints allow relative motion of the link members only in the plane containing them.
A parallelogram linkage is formed by corresponding link members 14, 15 and link members 12 and 13. The portions of link members 14 and 15 of the parallelogram are of equal length as are the portions of members 12 and 13 of the parallelogram. These members are connected together in a parallelogram for relative movement only in the plane formed by the members. A rotatable joint generally indicated by the numeral 22 is connected to a suitable base 24. The rotatable joint 22 is mounted on a base plate 26 adapted to be fixedly mounted to the base support means 24. A pivot plate 28 is pivotally mounted to base plate 26 by suitable means at, such as, pivots 30, 32. Thus pivot plate 28 may be rotated about axis x-x through a desired angle θ2. This may be accomplished manually or by a suitable pivot drive motor 34.
A first linkage is pivotally mounted on the pivot plate 23 of the rotatable joint 22. The linkage elements 11, 12 and the link members relatively stiff or inflexible so that they may adequately support an instrument used in surgical operations. Rods made of aluminum or other metal are useful as such links. The linkage elements 11 and 12 are pivotally mounted on base plate 28 for rotation with respect to the rotatable joint by pivots 36 and 38. At least one of the pivots 36, 38 is positioned so that its axis of rotation is normal to and intersects the x-x axis. Movement may occur manually or may occur using a linkage drive motor 40. The first linkage is also shaped in the form of a parallelogram formed by linkage elements 11, and 12; the portion of link member 15 connected thereto by pivots 16, 18; and base plate 28. One of the link members 15 is thus utilized in both the first 21 and second 23 linkage means. Linkage element 12 also forms a common link of both the first linkage means 21 and the second linkage means 23. In accordance with the invention, a remote center of spherical rotation 8 is provided by the above described embodiment of apparatus when the linkage element 11 is rotated and/or when pivot plate 28 is rotated about axis x-x. Thus the end of element 13 can be moved through desired angles θ1 and θ2 or rotated about its own axis while the remote center of rotation remains at the same location.
The preferred embodiment of apparatus assembled in accordance with the present invention is illustrated in FIGS. 2, 2a and 3. FIG. 2 is an elevation view, FIG. 2a is an enlarged sectional view taken at a—a of FIG. 2 and FIG. 3 is an end view of the remote positioning apparatus. Many of the elements of the preferred embodiment are the equivalent to elements of the FIG. 1 embodiment. These elements will be designated with the same numbers primed in FIGS. 2 and 3. Thus a pivot plate 28′ is rotatably mounted on a base support means 26′ by suitable means such as pivots 30′, 32′. The pivot plate and the base plate form a rotatable joint 22′ which has a rotation axis designated as x-x. The base plate may be fixedly mounted to a suitable base support means 24′.
Two linkage elements 11′ and 12′ extend from the pivot plate 28′. Mounting means 36′ and 38′ are provided to pivotally mount one end of each of the linkage elements to the pivot plate. The axis of rotation of the linkage elements are normal to and intersecting the x-x axis. A channel shaped link member 115 is pivotally connected by suitable pivot joints 16′ and 18′ to the other ends of linkage elements 11′, 12′ (respectively) equidistant from pivot plate 28′. A corresponding link member 15′ is located internally of link member 115 and is pivotally connected to the upper end of linkage element 12′. A link member 13′ corresponding in length to the link member 12′ between pivots 17′, 18′ is pivotally connected to link member 15′ at pivot 19′ and to link member 115 at pivot 20′. An instrument mounting means 44 is fixedly mounted to link member 13′ for movement therewith. The axis of an instrument held in the instrument mounting means 44 intersects the x-x axis of the rotating joint 22′. Thus an instrument held in the mounting means would have a remote center of spherical rotation about the position indicated by the numeral 8′ in FIG. 2.
A drive motor 434 incorporating a shaft-angle position sensor is operably connected to the pivot plate 28′. A second drive motor 440 incorporating a shaft-angle position sensor is operably connected to linkage element 11′. Suitable motor drive and control circuits may be connected to motor/sensor 440 and motor/sensor 434 via power and sensor cables 436 and 435 (respectively) to operate the present apparatus under open-loop or closed-loop servo control. The details of the mounting arrangement for the instrument mounting means are shown in FIG. 2a which is a sectional view taken at a—a of FIG. 2. As there shown the mounting means 44 is fixedly connected via multiple-axis force and torque sensor 400 and pin member 118 to link member 13′ for movement therewith. Link member 13′ is pivotally connected at pivot 20′ to the channel shaped link member 115 by bearing means 116, 117 formed about pin member 118. Link member 15′ is pivotally connected to link member 13′ at 19′ by means of bearing means 120 and pin member 121.
A suitable sensor interface circuit may be connected to the force and torque sensor 400 via cable 401 so that sensor signals arising from forces and torques applied to an instrument supported in the mounting means 44 can be detected and used for monitoring or controlling operation of the present apparatus. For example, the sensor signals can be used as feedback signals in master-slave force-reflecting telerobotic servo control of the invention such that the input control device responds to forces exerted on the supported instrument and is not affected by inertial loads, gravity forces, or external forces acting on linkage elements other than mounting means 44.
An apparatus is provided for moving an instrument about a spherical center of rotation at a desired location of the instrument. A base support means is adapted to be fixedly mounted to a surface. First linkage means 11′, 12′ are pivotally mounted on the base plate for rotation about an axis. A holding means 44 is provided for holding an instrument in a position so that the desired remote center of spherical rotation of the instrument intersects the axis and a second linkage means 15′, 115 and 13′ is connected to the holding means and pivotally connected to the first linkage means by pivots 17′, 18′, 16′ whereby the remote center of spherical rotation of the instrument is maintained at the desired location.
FIG. 4 is a schematic elevation view of another embodiment of apparatus assembled in accordance with the present invention. In many instances it may be desirable to have a means of adjusting the remote center of rotation 8′ relative to the mounted position of base plate 26′. Thus it would be desirable to axially extend or retract the horizontal members 14′, 15′ of the parallelogram linkage. The length of the two corresponding members 14′, 15′ must be increased or decreased in equal amounts to maintain the parallelogram geometry of the linkage.
The axial length adjustment could be provided in many ways. For example, as shown in FIG. 4, a portion of members 14′, 15′ are provided with racks 42, 44. Tubular members 46, 48 enclose members 14′, 15′. The members 14′, 15′ are extended or retracted by suitable means such as drive motor 50, motor lead 51 and drive belt 52. Other means for axially extending or retracting the members are available. For example, coupled lead screws could be used or the members could be manually fixed into the desired position in the tubular members using ratchets, pins or spring detents.
FIG. 5 illustrates an embodiment of apparatus assembled in accordance with the invention wherein a motor driven arrangement is positioned on the operating end of the parallelogram linkage. A drive unit 60 is connected by power and control cable 62 to a source of power and control and a cannula 64 is provided which may be passed through a patient's abdominal wall. An instrument 66 is attached to an operating element 68 and may be manipulated as indicated in FIG. 5. The remote center positioners as described heretofore will maintain the center of spherical rotation at position 80 while the instrument 66 is being manipulated.
FIG. 6 is an elevation view illustrating a manual application of the remote center positioner of the present invention. A handle 71 for operating a surgical instrument 73 is connected to the operating end of the remote center positioner. Movement of the cannula 75 will be constrained to rotation about the center 80′ of spherical rotation.
FIG. 7 is an elevation view and FIG. 7a is a sectional view taken at a—a of FIG. 7 of an embodiment of the invention which utilizes a flexible drive element in the linkage of the remote center positioner. A rotatable joint is indicated by the numeral 122. The rotatable joint rotates about an x-x axis. Thus pivot plate 128 can be rotated about pivots 130, 132 through a desired angle θ2 with respect to base plate 126. A linkage element 111 is pivotally mounted on the pivot plate by pivot 133. The pivot 133 is positioned so that its axis of rotation is normal to and intersects the x-x axis. A pulley 101 is positioned to be coaxial with the axis of rotation of the pivot 133. It is evident that the term pulley can include wheels, sprockets or the like. The pulley is fixedly connected to the base plate 128 by suitable means such as screws 105, 107. Thus the pulley will not rotate with respect to the base plate 128.
A link member 114 is pivotally connected by pivot joint 116 to linkage element 111. A second pulley 121 coaxial with pivot 116 is fixedly connected to link member 114 by screws 146 and 147. A flexible drive link 135 such as a belt, chain, or a cable is connected around the pulleys 121, 101 in a non slip mode such as a bicycle chain or timing belt. Pulleys 121 and 131 are of equal diameter as are pulleys 142 and 137. A link member 140 is pivotally connected to the operating end of link member 114 by means of pivot joint 141.
A third pulley 137 coaxial with pivot 141 is fixedly connected to link member 140 by means of screws 143, 145. A fourth pulley 142 coaxial with pivot 116 is fixedly connected to link element 111 by screws 160 and 16.1. A second flexible drive link 150 is connected around pulleys 137 and 142 in non slip relationship. Thus when linkage element 111 is rotated about pivot 133 by linkage drive motor 149 for example, the motion is transmitted by the pulleys to link member 140 which is constrained to move in parallel relationship with element 111. In this manner a remote center of rotation is maintained as indicated by 180 in FIG. 7.
FIG. 8 is an elevation view and FIG. 8a is a sectional view taken at a—a of FIG. 8 of another embodiment of the present invention.
A rotatable joint is shown and is indicated generally by the number 222. The rotatable joint rotates about a x-x axis. Thus pivot plate 228 can be rotated around pivots 230, 232 through a desired angle θ2. A linkage element 211 is pivotally mounted on the pivot plate 228 by pivot 233. The axis of the pivot 233 is located normal to and intersecting the x-x axis of rotation. A pulley 201 is positioned to be coaxial with the axis of rotation of the pivot 233. The pulley is fixedly connected to the base plate by suitable means such as screws 205, 207.
A pair of link members 214, 215 are pivotally connected to linkage element 211 by pivots 212 and 216 respectively. The other end of the link members 214 and 215 are pivotally connected to an instrument holding means or the like indicated by 240 by suitable pivot joints 241, 242. A second pulley 231 is fixedly connected to link element 215 by suitable screws 251, 252. The pulley 231 is mounted coaxially with the axis of rotation of the pivot joint 216. A flexible drive link 260 is connected around both pulleys 201 and 231 in non slip relationship. The effect of this construction constrains link members 215 and 214 to remain parallel with the x-x axis during movement and also constrains element 240 to remain parallel with linkage element 211 during movement, thus causing the center of spherical rotation of the instrument or the like to remain at point 280.
The principles, preferred embodiments and modes of operation of the present invention have been described in the foregoing specification. However, the invention which is intended to be protected is not to be construed as limited to the particular embodiments disclosed. The embodiments are to be construed as illustrative rather than restrictive. Variations and changes may be made by others without departing from the spirit of the present invention. Accordingly, all such variations and changes which fall within the spirit and scope of the present invention as defined in the following claims are expressly intended to be embraced thereby.

## Claims

1. A surgical manipulator for moving an instrument about a desired spherical center of rotation at a desired location along the instrument, the manipulator comprising:
a first linkage, including at least a first rod, pivotally mounted for rotation about a first axis;
an instrument holder holding the instrument in a position so that the desired remote center of spherical rotation of the instrument intersects a second axis and the first axis;
a second linkage, including at least a second rod, pivotally connected to the first linkage and the instrument holder such that the spherical center of rotation is maintained at the desired location along the instrument; and
wherein the first or second linkages includes a flexible drive element comprising a pulley and a flexible element connected around the pulley, the pulley rotationally affixed to one of the rods such that a movement of one of the linkages is transmitted to the other of the linkages by the flexible drive element.

2. A surgical manipulator for moving an instrument about a desired spherical center of rotation at a desired location along the instrument, the manipulator comprising:
a base support adapted to be mounted to a surface;
a first linkage pivotally mounted on the base support, the first linkage including a pulley rotationally fixedly mounted thereon adjacent to the base support;
an instrument holder for holding the instrument in a position with the desired remote center of spherical rotation;
a second linkage connected to the instrument holder and pivotally connected to the first linkage, the second linkage including a pulley rotationally fixedly mounted thereon adjacent the pivotal connection to the first linkage; and
a flexible element connected around the pulleys such that the remote center of spherical rotation of the instrument is maintained at the desired location as the linkages are moved.

3. A surgical manipulator system comprising.
a surgical instrument having an elongate shaft with proximal and distal ends, an end effector coupled to the distal end, and means for actuating the end effector at the proximal end;
a rotatable joint having an x—x axis of rotation;
a first linkage comprising one member having a first end pivotally mounted on the rotatable joint and a second end remote from the rotatable joint, the axis of rotation of the member of the first linkage being normal to and intersecting the x—x axis, the first linkage further comprising a first pulley rotationally fixedly mounted on the rotatable joint in coaxial relationship with the axis of rotation of the member;
a parallelogram linkage having a driving end and a remote end, the parallelogram linkage including two sets of two corresponding members pivotally connected in a parallelogram, the parallelogram linkage being in a parallel-plane relationship with the first linkage and having the driving end pivotally connected to the remote end of the first linkage, a second pulley rotationally fixedly mounted to one of the two corresponding members at the driving end of the parallelogram linkage coaxial with the pivotal connection between the driving end and the remote end of the first linkage, the first and the second pulleys having the same diameter;
a flexible element coupling the first pulley to the second pulley;
a drive for pivoting the end effector with respect to the instrument shaft; and
a mount for the instrument extending from the remote end of the parallelogram linkage, the mount adapted to position the instrument axis to intersect the x—x axis of the rotatable joint at a location on the instrument desired for a remote center of spherical rotation.

4. A surgical manipulator for moving an instrument about a desired spherical center of rotation at a desired location along the instrument, the manipulator comprising:
a first linkage, including at least a first pivotally mounted rod;
an instrument holder for holding the instrument;
a second linkage including a second rod connected to the instrument holder, the second linkage being pivotally connected to the first linkage so that the second rod such that the spherical center of rotation is maintained at the desired location of the instrument;
wherein the linkages include a channel-shaped element disposed around the second rod, the second rod and the channel-shaped element transmitting the movement of the first rod to the instrument holder.

5. The surgical manipulator of claim 4, wherein the channel-shaped element comprises a substantially rigid sleeve disposed around the second rod, the second rod and the rigid sleeve transmitting the movement of the first rod to the instrument holder such that the instrument is constrained to move in parallel relationship with the first rod.

6. A surgical manipulating system comprising:
a surgical instrument having an elongate shaft with a proximal end and a distal end configured for introduction into a patient;
an instrument holder coupled to the shaft of the surgical instrument;
a rotatable joint having an x—x axis of rotation;
a first linkage including one member having one end pivotally mounted on the rotatable joint and the other end remote from the rotatable joint, an axis of rotation of the member intersecting the x—x axis;
a second linkage comprising a sleeve and a rod disposed within the sleeve, the rod and sleeve being connected to the instrument holder for constraining the instrument holder to move such that the spherical center of rotation is maintained at the desired location of the instrument;
wherein the instrument comprises an end effector coupled to the distal end, means for actuating the end effector, and means for pivoting the end effector with respect to the instrument shaft.

7. A position constraint apparatus for constraining the position of a surgical instrument during operation in a minimally invasive surgical procedure, the surgical instrument including at least an elongate shaft, the shaft having a distal working end, at least the distal working end of the shaft configured for insertion into a body cavity of a patient, the position constraint apparatus comprising:
an articulate support assembly having a plurality of linkages and joints wherein the plurality of linkages and joints comprise at least one pulley and at least one flexible element coupled to the pulley that is configured to constrain shaft motion relative to a center of rotation;
an instrument engaging structure coupled to the a distal portion of the articulate support assembly;
the instrument engaging structure arranged to engage the surgical instrument so that the elongate shaft of the instrument is permitted to move relative to the instrument engaging structure;
the articulate support assembly configured to constrain the position of the elongate shaft of the instrument relative to the center of rotation, so that the shaft is maintained substantially aligned through the center of rotation; and
the position constraint apparatus configurable by an operator so as to permit the center of rotation to be positioned at a selected point.