Patent Description:
Over the past <NUM> years, several ultrasonic tools have been invented which can be used to ablate or cut tissue in surgery. <CIT> and <CIT> disclose such devices.

Ultrasonic surgical devices generally fall into two categories. One is a blunt tip hollow probe that vibrates at frequencies between <NUM> kc (<NUM>) and <NUM> kc (<NUM>), with amplitudes up to <NUM> microns or more. Such devices ablate tissue by either producing cavitation bubbles which implode and disrupt cells, tissue compression and relaxation stresses (sometimes called the jackhammer effect) or by other forces such as microstreaming of bubbles in the tissue matrix. The effect is that the tissue becomes liquefied and separated. It then becomes emulsified with the irrigant solution. The resulting emulsion is then aspirated from the site. Bulk excision of tissue is possible by applying the energy around and under unwanted tumors to separate it from the surrounding structure. The surgeon can then lift the tissue out using common tools such as forceps.

A second kind of ultrasonic device uses a sharp blade instead of a blunt hollow probe. Here a cutting action takes place. Such a sharp ultrasonic blade is the subject of <CIT>. As disclosed therein, the blade shape is semicircular at the distal portion with two straight sides parallel to the longitudinal axis and extending back to the shoulder that contacts the vibrating probe. Male threads are shown which mate with the female threaded socket of the probe (or transducer) to allow tight intimate contact of the probe and blade tip shoulder. When the two are torqued together, they form a single resonant body that will vibrate in sympathy with the transducer and generator combination. The distal end of the blade will vibrate with an amplitude set by the mechanical gain of the probe/tip geometry and the input amplitude provided by the transducer generator combination. This motion provides the cutting action for the tissue in question.

The blade of <CIT> was intended for the cutting or excising of bone or similarly hard tissue in surgical applications. The blade is more effective in cutting hard tissue. Soft tissue will bounce off the blade. Soft tissue trapped between the blade and a hard surface, i.e. spinal cord can be harmed. In delicate operations, such as sinus lift surgery or craniotomies where the goal is to cut an aperture in the front of the skull to expose sinus tissue or brain but not cut the membrane directly beneath the bony structure, this difference on hard and soft issue is very important. It is also important in spinal and brain surgery where bone tissue must be cut with a minimum of damage to underlying soft tissues such as the dura mater. It was noted in early in vitro testing that the blade, if it plunged rapidly through the cortex of the bone, could puncture the membrane or rip it. After some experience, competent surgeons were able to master the technique, but the learning curve was steep.

<CIT>, discloses a surgical method utilizing an ultrasonic surgical instrument with a blade having a thickness along a cutting edge of between about <NUM> inch (<NUM>) and about <NUM> inch (<NUM>). The method includes manually inserting the blade into bone tissue of a patient and ultrasonically vibrating the blade during the insertion procedure. Owing to the exigencies of the procedure, the blade prevents a surgeon from seeing at least a distal-most portion of the cutting edge during the inserting of the blade, as the distal-most portion of the cutting edge is located inside the patient. The surgeon manually terminates the inserting of the blade upon detecting via tactile sensation a change in resistance to advance of the blade indicating contact with soft tissue. While this technique is easier to master, there is still a need for an improved surgical methodology with ensured safety and efficacy. This is especially the case in spinal surgery where it is extremely important to avoid causing trauma to the spinal cord inside the spinal column.

<CIT> discloses a surgical manipulator for manipulating a surgical instrument and an energy applicator extending from the surgical instrument. The surgical manipulator has a controller configured to operate the surgical manipulator in a manual mode or a semi-autonomous mode. The controller has a feed rate calculator configured to calculate an instrument feed rate. The instrument feed rate is a velocity at which a distal end of the energy applicator advances along a path segment of a tool path in the semi-autonomous mode.

<CIT> discloses an energy supplier of an ultrasonic treatment system that outputs an electric power in a first output mode and a second output mode in which the electric power supplied to a drive force generation unit during a unit time is higher than in the first output mode. A controller maintains an output state of the electric power in the first output mode when a judgment section judges that a load on an ultrasonic probe is less than or equal to a threshold, and switches the output state of the electric power to the second output mode when the judgment section judges that the load is more than the first threshold.

An object of the present invention is to provide a surgical system for transecting osseous tissue in close proximity to vitally important structures, such as the spine.

A more specific object of the present invention is to provide such a surgical system that selectively transects osseous tissue while minimizing, and preferably eliminating, the risk of trauma to sensitive soft tissue nearby.

These and other objects of the invention will be apparent to those skilled in the art from the drawings and descriptions hereof. Although each object is attained by at least one embodiment of the invention, no embodiment need necessarily meet every obj ect.

The present invention is directed to a surgical system for transecting osseous tissue in the close proximity of vitally important structures such as the spine as defined in claim <NUM>. The system has, as principal components or subsystems, an ultrasonic waveform generator, a control unit, an ultrasonic instrument assembly including a electromechanical transducer and an ultrasonic blade, and a robotic system. The ultrasonic instrument assembly is attached to the robotic arm. In order to ensure safe operation, there should be no sudden surges in the instrument's penetration speed at the breakthrough point, that is at the point when the blade just penetrates through a distal side of a bone being cut. Pursuant to the invention, the surgical system is configured so that the robotic arm moves the ultrasonic blade at a constant forward feed speed through the bone during a cutting operation, the forward motion being reduced, and preferably halted automatically upon a reduction in load per unit time or applied power, as monitored by a pickup or sensor. Alternatively or additionally, power applied to the transducer via the waveform generator may be curtailed or interrupted.

The constant feed speed is maintained by servo controls of the robotic arm. The load change pickup is based on a feedback loop of the ultrasonic power application components (control unit, waveform generator, transducer), more precisely the variation of the drive voltage as a function of load. In order to maintain a constant motional amplitude, the ultrasonic controls maintain a constant motional current and phase angle while alternatively increasing and decreasing the ultrasonic voltage as a function of rising and falling load. At the breakthrough point, a voltage drop, associated with a decreased load, will be used as input to the servo controls for stopping the servo-driven motion. Additionally, the power output of the ultrasonic waveform generator may be at least substantially reduced or interrupted.

A surgical system comprises, in accordance with the present invention, a bone cutting blade, an ultrasonic electromechanical transducer, a robotic arm, a control processor, and an electrical waveform generator. The bone cutting blade has a cutting edge and is configured for transmitting ultrasonic vibrational energy, operatively connected to the ultrasonic electromechanical transducer, and mounted to the robotic arm. The control processor is operatively connected to the robotic arm and configured in part for controlling motion of the robotic arm so that the robotic arm moves the bone cutting blade at a constant or uniform rate through bone tissue during a cutting operation. The electrical waveform generator is operatively connected to the ultrasonic electromechanical transducer for energizing same to energize the bone cutting blade with ultrasonic mechanical waveform energy. The processor is operatively connected to the electrical waveform generator and configured therewith to monitor load on ultrasonic electromechanical transducer. The processor is further configured to undertake, upon sensing a reduction in load or applied power, a control action taken from the group consisting of inducing the robotic arm to halt motion of the bone cutting blade and at least substantially reducing waveform energy output of the waveform generator.

An associated surgical method, not belonging to the invention, comprises providing an ultrasonic bone cutting blade operatively connected to an ultrasonic electromechanical transducer; mounting the ultrasonic bone cutting blade and the ultrasonic electromechanical transducer to a robotic arm, and via a plurality of servomechanisms actuating the robotic arm to move the ultrasonic bone cutting blade at a constant or uniform rate through bone tissue during a surgical cutting operation. The method also comprises operating an electrical waveform generator to energize the ultrasonic electromechanical transducer to vibrate the ultrasonic bone cutting blade at an ultrasonic frequency during the surgical cutting operation. The operating of the electrical waveform generator includes adjusting power output thereof to maintain a constant vibrational amplitude of the ultrasonic bone cutting blade. Furthermore, the method includes automatically monitoring load or power output of the electrical waveform generator and, upon sensing a reduction in load or applied power, operating the servomechanisms to actuate the robotic arm to halt motion of the ultrasonic bone cutting blade and optionally at least substantially reducing waveform energy output of the waveform generator.

A surgical system for transecting osseous tissue in close proximity to vitally important structures comprises, in accordance with the present invention, an ultrasonic waveform generator, a control unit operatively connected to the ultrasonic waveform generator, and an ultrasonic instrument assembly including an electromechanical transducer and an ultrasonic blade. The ultrasonic waveform generator is operatively connected to the transducer for energizing same. The system further comprises a robotic subsystem including servomechanisms and a robotic arm movable by the servomechanisms. A load sensor or pickup component is operatively connected to the electromechanical transducer and included in the ultrasonic waveform generator, the load sensor or pickup component being operatively connected to the control unit. The ultrasonic instrument assembly is attached to the robotic arm, while the control unit is operatively connected to the servomechanisms and configured to actuate the robotic arm so as to move the ultrasonic blade at a constant forward feed rate through bone tissue during a cutting operation. The control unit is additionally configured to operate the servomechanisms, in response to a drop in load per unit time or applied power as detected by the load sensor or pickup component, to at least reduce forward motion of the ultrasonic blade through the bone tissue automatically. Optionally, the control unit is further configured to at least substantially reduce power output of the ultrasonic signal generator automatically in response to a drop in load per unit time or applied power as detected by the load sensor or pickup component.

A related surgical method, not belonging to the invention, for transecting osseous tissue in close proximity to vitally important structures comprises operating an ultrasonic waveform generator to output an ultrasonic waveform signal of a preselected frequency, feeding the ultrasonic waveform signal to an electromechanical transducer of an ultrasonic instrument assembly including an ultrasonic blade, generating an ultrasonic standing wave in the ultrasonic instrument assembly including the ultrasonic blade, and controlling a robotic subsystem including servomechanisms and a robotic arm movable by the servomechanisms, to move the ultrasonic blade at a constant forward feed rate through bone tissue during a cutting operation, where the ultrasonic instrument assembly is mounted to the robotic arm. In response to a drop in load or applied power as detected via a load sensor or pickup component, the robotic subsystem is controlled to terminate forward motion of the ultrasonic blade in the bone tissue.

Pursuant to another feature of the present invention, the operating of the ultrasonic waveform generator includes adjusting power output thereof to maintain a constant vibrational amplitude of the ultrasonic blade. Preferably, this is accomplished by adjusting voltage of the power output of the ultrasonic waveform generator while maintaining motional current and phase angle constant.

The controlling of the robotic subsystem preferably includes operating a digital processor of a control unit operatively connected to the servomechanisms.

In response to a drop in load or applied power as detected via a load sensor or pickup component, the ultrasonic waveform generator may be controlled to at least substantially reduce power output thereof automatically. The controlling of the robotic subsystem to reduce power output of the ultrasonic waveform generator may include operating a digital processor of a control unit operatively connected to the robotic subsystem.

The sole Figure of the drawing is a block diagram of a surgical system in accordance with the present invention.

A surgical system for transecting osseous tissue in the close proximity of vitally important structures such as the spine has, as principal components or subsystems, an ultrasonic waveform generator <NUM>, a control unit in the form of a digital processor <NUM>, an ultrasonic instrument assembly <NUM> including an electromechanical transducer <NUM> and an ultrasonic blade <NUM>, and a robotic system <NUM>. Ultrasonic instrument assembly <NUM> is attached to a robotic arm <NUM> of system <NUM>. Blade <NUM> is an integral or unitary part of a probe or tool <NUM> including a shank and a screw connector (neither shown separately) that couples the probe or tool to electromechanical transducer <NUM>.

In order to ensure safe operation of the surgical system, there should be no sudden surges in the penetration speed of blade <NUM> at a breakthrough point, that is, at a point when blade <NUM> just penetrates through a distal side of a bone being cut. The surgical system is configured so that robotic arm <NUM> moves ultrasonic blade <NUM> at a constant forward feed speed through the bone during a cutting operation. Digital processor or control unit <NUM> is connected to a plurality of translational servomechanisms 26a, 26b, 26c and a plurality of rotation servomechanisms 28a, 28b, 28c that implement degrees of freedom necessary for instrument control. Digital processor or control unit <NUM> reduces forward motion of blade <NUM> through the bone tissue at a preselected surgical site and preferably halts the forward motion automatically upon a reduction in load per unit time or applied power, as monitored by a pickup or load sensor <NUM>. Alternatively or additionally, power applied to transducer <NUM> by waveform generator <NUM> may be curtailed or interrupted.

Load sensor <NUM> may be part of a waveform generation subsystem <NUM>, included in effect as part of waveform generator <NUM>. The waveform generation control portion of digital processor <NUM>, as well as the waveform generation subsystem <NUM> may take a form as described in <CIT> and <CIT>.

The constant feed speed of blade <NUM> is maintained by robotic arm <NUM> in response to the selective activation of servomechanisms 26a, 26b, 26c and 28a, 28b, 28c by digital processor or control unit <NUM>. Load change pickup as detected via load sensor <NUM> is implemented in a feedback loop of the ultrasonic power application components (control unit <NUM>, waveform generator <NUM>, transducer <NUM>), more precisely the variation of the drive voltage as a function of load. See <CIT> and <CIT>. In order to maintain a constant motional amplitude, the ultrasonic controls maintain a constant motional current and phase angle while alternatively increasing and decreasing the ultrasonic voltage as a function of rising and falling load. At a breakthrough point, a voltage drop, associated with a decreased load, will be used as input to the servo controls (ditigal processor <NUM>) for stopping or interrupting the operation of servomechanisms 26a, 26b, 26c and 28a, 28b, 28c. Additionally, the power output of the ultrasonic waveform generator <NUM> may be at least substantially reduced or interrupted.

Bone cutting blade <NUM> is formed at a distal end with a cutting edge <NUM> and may take the form shown in <CIT> and <CIT>. Blade <NUM> is configured for transmitting ultrasonic vibrational energy, more specifically being dimensioned with probe <NUM> and transducer <NUM> to carry therewith an ultrasonic standing wave of desired frequency, exemplarily <NUM>. As discussed above, control unit or processor <NUM> is operatively connected to robotic arm <NUM> and configured in part for controlling motion of robotic arm <NUM> so that the robotic arm moves the bone cutting blade <NUM> at a constant or uniform rate (speed) through bone tissue during a cutting operation. Electrical or ultrasonic waveform generator <NUM> is operatively connected to the ultrasonic electromechanical transducer <NUM> for energizing same to vibrate bone cutting blade <NUM> at the preselected (design) ultrasonic frequency. Processor <NUM> is operatively connected to the electrical waveform generator and configured therewith to monitor load on ultrasonic electromechanical transducer <NUM>. Processor <NUM> is further configured to undertake, upon sensing a reduction in load or applied power (via input from load sensor <NUM>), a control action of inducing the robotic arm <NUM> to halt motion of bone cutting blade <NUM> and/or at least substantially reducing waveform energy output of the ultrasonic electromechanical transducer <NUM>.

An associated surgical method, not belonging to the invention, utilizing the illustrated surgical system typically includes mounting ultrasonic bone cutting blade <NUM> and ultrasonic electromechanical transducer <NUM> to robotic arm <NUM>, and via servomechanisms 26a, 26b, 26c and 28a, 28b, 28c actuating the robotic arm to move the cutting blade at a constant or uniform rate through bone tissue during a surgical cutting operation. Electrical waveform generator <NUM> is operated to energize electromechanical transducer <NUM> to vibrate blade <NUM> at an ultrasonic frequency (e.g., <NUM>) during the surgical cutting operation. The operating of waveform generator <NUM> includes adjusting power output thereof to maintain a constant vibrational amplitude of the ultrasonic bone cutting blade, as disclosed in <CIT> and <CIT>. The method includes automatically monitoring load or power output of waveform generator <NUM> and, upon sensing a reduction in load or applied power, operating the servomechanisms 26a, 26b, 26c and 28a, 28b, to actuate robotic arm <NUM> to halt motion of blade <NUM> and optionally at least substantially reducing waveform energy output of waveform generator <NUM>.

Claim 1:
A surgical system for transecting osseous tissue in close proximity to vitally important structures, comprising:
an ultrasonic waveform generator (<NUM>);
a control unit (<NUM>) operatively connected to said ultrasonic waveform generator (<NUM>);
an ultrasonic instrument assembly (<NUM>) including an electromechanical transducer (<NUM>) and an ultrasonic blade (<NUM>), said ultrasonic waveform generator (<NUM>) being operatively connected to said transducer (<NUM>) for energizing same;
a robotic subsystem (<NUM>) including servomechanisms (26a, 26b, 26c, 28a, 28b, 28c) and a robotic arm (<NUM>) movable by said servomechanisms (26a, 26b, 26c, 28a, 28b, 28c); and
a load sensor or pickup component (<NUM>) operatively connected to said electromechanical transducer (<NUM>) and included in said ultrasonic waveform generator (<NUM>, <NUM>), said load sensor or pickup component (<NUM>) being operatively connected to said control unit (<NUM>);
said ultrasonic instrument assembly (<NUM>) being attached to said robotic arm (<NUM>);
said control unit (<NUM>) being operatively connected to said servomechanisms (26a, 26b, 26c, 28a, 28b, 28c) and configured to actuate said robotic arm (<NUM>) so as to move said ultrasonic blade (<NUM>) at a constant forward feed rate through bone tissue during a cutting operation;
said control unit (<NUM>) being further configured to operate said servomechanisms (26a, 26b, 26c, 28a, 28b, 28c), in response to a drop in load per unit time or a drop in applied power as detected by said load sensor or pickup component (<NUM>), to (a) at least reduce forward motion of said ultrasonic blade (<NUM>) through the bone tissue automatically or (b) at least substantially reduce power output of said ultrasonic signal generator (<NUM>) automatically.