Electricity: motive power systems – Positional servo systems – With protective or reliability increasing features
Reexamination Certificate
2000-01-26
2002-04-23
Ro, Bentsu (Department: 2837)
Electricity: motive power systems
Positional servo systems
With protective or reliability increasing features
C345S215000, C345S184000, C606S001000, C901S034000
Reexamination Certificate
active
06377011
ABSTRACT:
BACKGROUND
Minimally invasive surgery techniques reduce the amount of extraneous tissue that are damaged during diagnostic or surgical procedures, thereby reducing patient recovery time, discomfort, and deleterious side effects, such as infection. Millions of the surgeries performed each year in the United States can be performed in a minimally invasive manner. However, far fewer of the surgeries performed currently use these techniques, due to limitations in minimally invasive surgical instruments and techniques and the additional training required to master them.
Advances in MIS technology could have a dramatic impact. The average length of a hospital stay for a standard surgery may be double that for the equivalent minimally invasive surgery. Thus, an increase of use of minimally invasive techniques could save many millions of hospital days and attendant costs alone. Patient recovery times, patient discomfort, surgical side effects, and time away from work are also reduced with minimally invasive surgery.
Endoscopy, a variety of MIS, generally refers to inserting tools into the body through natural orifices. Laparoscopy, another variety of MIS, refers to inserting tools through tiny incisions with sealed ports. In standard laparoscopic surgery, as shown schematically with reference to
FIG. 1
, a patient's abdomen is insufflated with gas, and cannula sleeves
510
are passed through small (approximately ½ inch (1 cm.)) incisions in the body wall
512
to provide entry ports for laparoscopic surgical instruments
514
. The cannula holes may be created by a sharp pointed trocar, which may be equipped with an integral cannula. The following discussions are generally cast in terms of laparoscopy. However, the general principles apply to endoscopy also, and to most MIS.
The MIS instruments generally include a scope (endoscope or laparoscope), for viewing the surgical field, and working tools, such as blunt probes, dissectors, clamps, graspers, scissors, staplers, and needle holders. The working tools are similar to those used in conventional (open) surgery, except that, as shown in
FIG. 1
, the working end
516
of each tool is separated from its handle end
518
by an approximately 12-inch (30 cm) long extension tube
520
. The view is typically displayed on a monitor.
To perform MIS procedures, the surgeon passes instruments through the cannula
510
and manipulates them inside the body by sliding them in and out through the cannula, along the z axis, as shown, rotating them in the cannula around the z axis, levering (i.e., pivoting around the x and y axes, as shown) the instruments in the body wall
512
and operating end effectors (not shown) on the distal end
516
of the instruments. The instruments pivot around centers of rotation approximately defined by the incisions in the muscles of the body wall
512
.
The tools are selected from among a family of approximately 33 cm long, 5-10 mm diameter surgical instruments. During the operation, the surgeon is frequently working with two toolhandles, while looking away from the patient at a television monitor, which displays the internal worksite image provided by the scope camera.
A representative handle end
518
, with a cover piece removed, is shown with reference to
FIG. 2
, and a representative scissor tool end
516
is shown with reference to FIG.
3
. An outer shaft
524
is connected to two jaws
86
a
and
86
b
, which are both also hingedly connected to an inner shaft
526
, such that when the shafts translate relative to each other, the jaws open, or close, depending upon the direction of relative motion. This type of linkage can be used with grippers, scissors, or other types of jawed tools. There are also other types of linkages. However, in general, all have a relative translation of two shafts that causes opening and closing of gripper or cutting jaws. Typically jawed instruments have two jaws, however, there can be more than two, such as when several jaws are attached to a collar, and are closed by retraction into a narrow sleeve.
In general, the handle
518
incorporates a lever
522
, which amplifies the force applied by the human hand by a factor of around four, and transmits this force to the inner shaft
526
, which runs the length of the tool to the working end
516
. The travel extent of the inner shaft
526
depends on the individual lever design for the brand of tool, typically between 1 and 8 mm. The finger loops
528
a
and
528
b
of the handle
518
may be decoupled from the twisting of the outer and inner shafts
524
,
526
about their long (parallel to the z) axis. Twisting can be controlled by placing the index finger on a wheel
534
at the top of the shaft. Typically, the inner shaft
526
is coupled to one
528
a
of the two handles through a ball joint
532
and the outer shaft
524
is held translationally in place by the wheel
534
, which has an internal flange that mates with the outer shaft to fix it translationally. The wheel also has a key on its inside that fits into a slot on the outside of the outer shaft, which key/slot pair couple the shaft and wheel rotationally. The wheel fits in an opening in the handle
528
b
, with respect to which the wheel and outer shaft can rotate about the z axis, as described above. The two handles
528
a
and
528
b
are fixed to each other with respect to rotation around the z axis. A cover to the handle (not shown) is essentially congruent with the larger handle piece
528
b
, trapping the wheel
534
, outer and inner shafts
524
and
526
, and the smaller handle piece
528
a
therebetween.
Thus, the wheel essentially permits decoupling rotation of the outer shaft from rotation of the handle. The inner and outer shafts are coupled to each other in a typical tool by the linkages that join each to the jaws, which are connected to each other such that they rotate with each other. There are some tools that do not have a decoupling wheel, and with those tools, rotating the handle around the shaft axis also rotates the outer shaft.
A typical MIS jawed tool has five degrees of freedom, relative to the axes shown in FIG.
1
. These are: translation along the z axis, rotation around the z, x and y axes, and motion of the jaws
86
a
,
86
b
relative to each other. The insertion force (z axis), pitch and yaw torques (x and y axes), and the jaw force are all significant in surgery and training. Active twisting around the tool (z) axis is not always applied, but is present in many procedures. Translation along the x and y axes does not occur, due to the constraint of the cannula and the patient's body wall
512
.
Similar MIS techniques are employed in arthroscopy, retroperitoneoscopy, pelviscopy, nephroscopy, cystoscopy, cisternoscopy, sinoscopy, hysteroscopy and urethroscopy, just to name a few. The common feature of all of these MIS techniques is that they obtain and display a visual image of a worksite within the human body and pass specially designed surgical instruments through natural orifices or small incisions to the worksite to manipulate human tissues and organs, thus avoiding the collateral trauma caused to surrounding tissues, which would result from creating open surgical access. These techniques may be variously referred to herein as minimally invasive surgeries, MIS, generic endoscopies, or key-hole surgeries.
Current MIS technology presents many difficulties. First, the image of the worksite is typically a two-dimensional image displayed on an upright monitor somewhere in the operating room. The surgeon is deprived of three-dimensional depth cues and may have difficulty correlating hand movements with the motions of the tools displayed on the video image. Second, the instruments pivot at the point where they penetrate the body, causing the tip of the instrument to move in the opposite direction to the surgeon's hand. Third, existing MIS instruments deny the surgeon the flexibility of tool placement available in open surgery. Most MIS tools have rigid shafts and are constrained to approach the worksite from the direction o
Massachusetts Institute of Technology
Ro Bentsu
Weissburg Steven J.
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