Motor assembly for a powered surgical instrument

(54) Title: ACCOMMODATION MEMBER AND (57) Summary:

SET FOR A MOTORIZED SURGICAL INSTRUMENT, AND METHOD FOR ACTIVATING A SURGICAL INSTRUMENT.

(30) Unionist Priority: 28/02/2007 us 11/680488 (73) Holder (s): Medtronic PS Medicai, INC.

(72) Inventor (s): Durrel Tidwell, Gabriel A. Johnston, Jonathan Morris (74) Attorney (s): Momsen, Leonardos & Cia.

(86) International Order: pct us2008053441 of 02/08/2008 (87) International Publication: wo 2008 / i06292de 04/09/2008

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“ACCOMMODATION AND JOINT MEMBER FOR A

MOTORIZED SURGICAL INSTRUMENT AND METHOD FOR

ACTIVATE A SURGICAL INSTRUMENT ”

FIELD OF THE INVENTION

The present description relates in general to surgical instruments and in particular to surgical instruments for dissecting bones and other tissues.

BACKGROUND OF THE INVENTION

Motorized surgical instruments can use a variety of methods to drive moving components. For example, a motorized surgical instrument used to dissect bone or tissue can use a pneumatic motor to drive a dissection tool. Pressurized fluid drives the motor, which can be mechanically connected to the dissection tool by means of a rotating shaft. The application of pressurized fluid to the motor results in rotation of the shaft, which in turn rotates the dissection tool.

Difficulties can arise in the assembly and operation of pneumatic surgical instruments. Conventional pneumatic surgical instruments house the rotating shaft in a rotor housing chamber defined by a rotor housing. In order to allow the shaft to rotate freely in the rotor housing chamber, a plurality of components are coupled to the rotor housing, such as bearings, bearing housings, fluid distributors and a variety of other components known in the art. In addition, to ensure that these components are positioned correctly in the assembly, an alignment pin can be used to align the components with the rotor housing and shaft. As the number of components coupled to the rotor housing increases, the tolerance between the components and the rotor housing makes the ability to repeat the assembly of the surgical instrument itself difficult. As a result, what is needed is an improved assembly for a surgical instrument.

SUMMARY

The present description provides many technological advances that can be used, either alone or in combination, to provide an improved motor assembly for a motorized surgical instrument and / or an improved system and methods for using motorized surgical instruments.

In one embodiment, a housing member for a motorized surgical instrument includes a one-piece base, a base-defined rotor housing, a first base-defined bearing housing and located adjacent to the rotor housing chamber, a second bearing housing defined by the base and located on an opposite side of the rotor housing chamber in relation to the first bearing housing and a passage defined by the base and operable to direct a pressurized fluid through the base to the rotor housing chamber.

Additional forms and achievements will be apparent from the detailed description provided below. It should be understood that the detailed description and specific examples, while indicating preferred embodiments, are intended for purposes of illustration only and are not intended to be limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

This description will be understood more fully from the detailed description and accompanying drawings, in which:

Figure 1 is an environmental view illustrating an embodiment of a surgical instrument for the dissection of bone and other tissue in accordance with the teachings of an embodiment of the present description operatively associated with a patient to perform a craniotomy.

Figure 2 is a perspective view illustrating an embodiment of the surgical instrument for dissecting bone and other tissue according to the teachings of an embodiment of the present description, the surgical instrument shown operatively associated with a hose assembly .

Figure 3a is an exploded perspective view illustrating an embodiment of a portion of the surgical instrument of Figure 2.

Figure 3b is a perspective view showing an embodiment of a housing member used in the surgical instrument of Figure 2 and illustrated in Figure 3a.

Figure 3c is a side view illustrating an embodiment of the housing member shown in Figure 3b.

Figure 3d is a cross-sectional view illustrating an embodiment of the housing member shown in Figure 3b taken along line 3d-3d in Figure 3b.

Figure 3e is a cross-sectional view illustrating an embodiment of the remaining portion of the housing member shown in Figure 3b and not shown in Figure 3d.

Figure 3f is a cross-sectional view illustrating an embodiment of the rotor housing shown in Figure 3b taken along line 3f-3f in Figure 3c.

Figure 3g is a partial cross-sectional view illustrating an embodiment of a portion of the assembled surgical instrument shown in Figure 3a.

Figure 4 is a partial cross-sectional view illustrating an embodiment of a portion of the surgical instrument illustrated in Figure 2.

Figure 5 is a perspective view illustrating an alternative embodiment of a housing member.

DETAILED DESCRIPTION

The present description refers to surgical tools and, more particularly, to a housing member and motor assembly for use in motorized surgical instruments. However, it is understood that the following description provides many different embodiments, or examples, for implementing different features of the invention. Specific examples of components and arrangements are described below to simplify the present description. These are, of course, only examples and are not intended to be limiting. In addition, the present description may repeat reference numerals and / or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself determine a relationship between the various embodiments and / or configurations discussed. Initially using Figure 1, a surgical instrument for the dissection of bone and other tissue constructed in accordance with the teachings of a first preferred embodiment of the present invention is illustrated and generally identified by reference numeral 100. Surgical instrument 100 is shown associated operatively with patient A to perform a craniotomy. It will be apparent to those skilled in the art that the present invention is not limited to any particular surgical application, but is useful for various applications in which it is desired to dissect bone or other tissue.

Referring to Figure 2, surgical instrument 100 is illustrated to generally include a motor assembly 102, an accessory 104 coupled to motor assembly 102 and a surgical tool 106 attached to accessory 104 and motor assembly 102. In the form of preferred embodiment, surgical tool 106 is a cutting tool or dissection tool, although the type of tool is not essential to implement the present invention. A distal end of the dissection tool 106 includes a member adapted for a particular procedure, for example, a cutting member. Accessory 104 can provide a handle surface for use by a surgeon and can also protect underlying portions of the instrument 100 during a surgical procedure. The surgical instrument 100 is shown connected to a hose assembly 108 to provide a source of pressurized fluid (e.g., air or nitrogen) for the motor assembly 102 through a tube 110 and a passageway 112 in the hose assembly 108 to exhaust fluid after going through the motor assembly 102. Typically, hose assembly 108 is connected to a filter system (not shown) away from the patient and the discharge fluid is allowed to exit the system after passing through the filter system. In the exemplary embodiments that will be described, surgical instrument 100 is pneumatically powered. However, it is further understood that many of the teachings discussed here will have equal application for surgical instruments that use other power sources.

Reference is now made to Figure 3a, an embodiment of the motor assembly 102 of Figure 2 is shown in detail. The motor assembly 102 includes a motor housing 200 having an inner surface 202 that defines an inner chamber 204 generally cylindrical. The motor housing 200 may include, for example, internal shoulders (not shown) that extend into the inner chamber 204 and seals (not shown) to create a seal between the motor housing 200 and the other components of the motor assembly 102 , described in further detail below. The seals can be made of a material that includes a form composed of PTFE fluorocarbons and other inert ingredients, such as the product RULON-J. This material provides seals with a relatively low coefficient of friction while requiring little or no lubrication.

The motor assembly 102 further comprises a bearing retaining member 300 having a bearing engaging surface 300a, a fastener 302 including a coupling member 302a, a first bearing 304 defining a first bearing opening 304a, a plug 306, a rotary axis 308 that includes a plurality of vanes 308a that extend along its length and a pair of opposite coupling ends 308b and 308c, a bearing plate 310 which defines a bearing plate opening 310a and a second bearing 312 defining a second bearing opening 312a, all located within and / or coupled to a housing member 400 in a manner described in more detail below .

Reference is now made to Figs. 3a, 3b, 3c, 3d, 3e and 3f, the housing member 400 includes an elongated and generally cylindrically formed base 402 which has a first end 402a and a second end 402b located opposite the first end 402a. In the illustrated embodiment, the housing member 400 is a unitary piece of material with various characteristics, described below, defined in or for the material. Although a homogeneous unitary material that forms the housing member 400 is shown, it is contemplated that non-homogeneous materials such as, for example, a substrate material coated with a different material can be coupled to form the one-piece housing member 400. In one embodiment, housing member 400 is made of stainless steel. In one embodiment, housing member 400 may be made of ceramic and / or may include a coating to make housing member 400 more resistant to abrasive wear. In one embodiment, the housing member is machined. A pressurized fluid inlet 404 is defined by the base 402 and extends from the first end 402a of the base 402 along a longitudinal axis B of the base 402 towards the second end 402b of the base 402. A first bearing housing 406 is defined by the base

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402 and is located immediately adjacent to the pressurized fluid inlet 404. A coupling opening 408 is defined by the base 402, by an inner plate 410 which is located immediately adjacent to the first bearing housing 406. A rotor housing chamber 412 is defined by base 402 and located immediately adjacent to the inner plate 410 and the coupling opening 408 opposite the first bearing housing 406. A second bearing housing 414 is defined by the base 402 and extends between a plate engaging wall 414a adjacent the rotor housing chamber 412 and the second end 402b of the base 402. A passage 416 is defined by the base 402 and extends in a substantially parallel orientation, but radially spaced from the longitudinal axis B of the base 402 of a passage inlet 416a such that passage 416 is axially placed adjacent to the pressurized fluid inlet 404, the first bearing housing 406, the inner plate 410 and a portion of the rotor housing chamber 412. A passage inlet 418 is defined by the base 402 oriented at an angle to the passage 416 and provides a fluid passage between the pressurized fluid inlet 404 and the passage 416. In the illustrated embodiment, the passage inlet 418 is oriented to a 45 degree angle for passage 416. A plurality of high-pressure fluid inlets in the rotor housing 420 are defined by the base 402 and provide a fluid passage between the high-pressure passage 416 and the rotor housing chamber 412. A plurality of fluid outlets from the rotor housing rotor 422 are defined by the base 402 and provide a fluid passage between the rotor housing chamber 412 and the outside of the base 402.

Reference is now made particularly to Figs. 3 a and 3g, in an assembled form, the plurality of vanes 308a are attached to the rotary axis 308 which is positioned within the rotor housing chamber 412 of the base 402. The coupling end 308b of the rotating shaft 308 extends through the coupling opening 408 and for the first bearing housing 406 and the coupling end 308c of the rotating shaft 308 extends through the second bearing housing 414 and out close to the second end 402b of base 402. The bearing plate 310 is located in the second bearing housing 414 and in engagement with the plate engaging wall 414a such that the rotary axis 308 extends through the opening of the bearing plate 310a defined by the bearing plate 310. The second bearing 312 is located in the second bearing housing 414 and in engagement with the bearing plate 310 such that the rotary shaft 308 extends through the second bearing opening 312a and is rotatably supported by the second bearing 312. In the illustrated embodiment, the second bearing 312 is held in place by a friction engagement or interference fit with the inner wall of the bearing housing 414. In an alternative embodiment, adhesives can be used to hold the second bearing 312 in position.

The first bearing 304 is located in the first bearing housing 406 and in engagement with the inner plate 410 such that the coupling end 308b of the rotary shaft 308 extends to the first bearing opening 304a and is rotatably supported by the first bearing 304. Coupling member 302a on fastener 302 engages coupling end 308b on rotary shaft 308 and fastener 302 engages on first bearing 304. The bearing retainer member 300 is partially located in the first bearing housing 406 and the pressurized fluid inlet 404 such that the bearing engagement surface 300a engages the first bearing 304.

The plug 306 is located in the passage opening 416a such that pressurized fluid in passage 416 cannot escape from passage 416 through passage opening 416a. In the illustrated embodiment, the passage opening 416a is a result of manufacturing the passage 416 which requires the passage 416 to be drilled into the base 402 of the first end 402a of the housing member 402. The plug 306 is then permanently snapped into the passage opening 416a to prevent pressurized fluid from escaping from passage 416 through the passage opening 416a. However, alternative embodiments may include manufacturing techniques for passage 416 that eliminate passage opening 416a and the need for plug 306, as the alternative embodiment 500 described below and illustrated in Figure 5. In a further embodiment, additional seals may be provided on the housing member 400 such that a fluid-tight passage is provided between the first bearing housing 406, the rotor housing chamber 412 and the second bearing housing 414 and pressurized fluid introduced into passage 416 flow through the fluid inlets 420 of the rotor housing to the rotor housing chamber 412 and out of the fluid outlets of the rotor housing 422 and do not escape through the first bearing housing 406 or the second bearing housing 414.

With continued reference to Figs. 3a and 3g, and with additional reference to Figure 4, in operation the housing member 400, which includes the bearing retaining member 300, the fastener 302, the first bearing 304, the plug 306, the rotary axis 308, the plate bearing 310 and the second bearing 312, is positioned in the inner chamber 204 in the motor housing 200. In the illustrated embodiment, the engagement between housing member 400 and motor housing 200 allows exhaust pressure to surround housing member 400 such that a majority of the exhaust pressure flows into hose assembly 108 and through passage 112 In another embodiment, the engagement between the housing member 400 and the motor housing 200 creates a fluid tight seal. In a further embodiment, fluid tight seals are provided between housing member 400 and motor housing 200. Hose assembly 108 is then joined to motor housing 200 such that tube 110 is joined to first end 402a of the housing member 402 and provides a sealed passage for pressurized fluid between the tube 110 and the pressurized fluid inlet 404. A seal is also provided between the hose assembly 108 and the motor housing 200. The coupling end 308c of the rotary shaft 308 can be coupled to the surgical tool 106 (not shown) using, for example, tweezers.

Pressurized fluid in the range 0 to 150 psi (0 to 1.03 MPa) then enters the pressurized fluid inlet 404 from the tube 110 in the hose assembly 108 and a control can be provided to allow a user of the instrument surgical 100 adjust the pressure of the pressurized fluid between this range. In one embodiment, the pressure of the pressurized fluid upstream of the engine assembly is adjusted to 120 psi (0.83 MPa). In one embodiment, the pressure of the pressurized fluid upstream of the engine assembly adjusts to 100 psi (0.7 MPa). In one embodiment, pressure losses in the pressurized fluid upstream of the engine assembly can be between 10 to 30 psi (69 kPa to 206.8 kPa). The pressurized fluid is directed to passage 416 through passage inlet 418 due to the seal between the bearing retaining member 300 and the first bearing 304 and the seal between the plug 306 and the passage opening 416a. The pressurized fluid is then directed to the rotor housing chamber 412 through the fluid inlets in the rotor housing 420. As the pressurized fluid moves through the rotor housing chamber 412 of the fluid inlets in the rotor housing 420 towards the fluid outlets of the rotor housing 422, the fluid impacts the vanes 308a and causes the rotary shaft to rotate 308. In one embodiment, the centerline of the rotary axis 308 can deviate from the centerline of the rotor housing chamber 412 to create increased torque relative to when the centerlines of the rotary axis 308 and the housing chamber of rotor rotor 412 are co-linear. The lower pressure fluid then exits the rotor housing chamber 412 through the fluid outlets in the rotor housing 422 and resumes through the exhaust fluid passage 112 in the hose assembly 108 between the pipe 110 and the hose assembly 108. In one embodiment, the fluid loses pressure due to expansion and energy exchange and can be, for example, between 20-30 psi (0.14 to 0.21 MPa) dynamic when the fluid pressure upstream of the set of engine 102 is 120 psi (0.70 to 0.82 MPa). Thus, a surgical instrument is presented that includes a housing member that allows a simplified assembly of the motor assembly in relation to a conventional rotor housing and reduces the passages available to provide a fluid leak by reducing the number of components used in the assembly of engine. Although the surgical instrument 100 has been described as being pneumatically powered by a gaseous fluid, other driving schemes are contemplated, for example, hydraulic actuation of the surgical instrument with a liquid fluid.

Reference is now made to Figure 5, in an alternative embodiment, a housing member 500 is substantially similar in design and operation to the housing member 400 described above with reference to Figs. 3a, 3b, 3c, 3d, 3e, 3f, 3g and 4, with the proviso that an opening 502 defined by the base 402 of the housing member 500 is located adjacent to the passage 416. A sealing groove 504 is defined by the base 402 and is located around the perimeter of aperture 502. A sealing groove 506 is defined by the base 402 and is located around the circumference of the base 402 and between the opening 502 and the second end 402b of the base 402. In assembly, the housing member 500 is positioned in the inner chamber 204 of the motor housing 200 in substantially the same manner as described above for the housing member 400, with the proviso that seals (not shown) are located in the sealing grooves 504 and 506 such that the seals engage the inner surface 202 of the motor housing 200 and provide a fluid tight seal between the housing member 500 and the motor housing 200. In operation, the housing member 500 operates substantially similarly to the housing member 400, with the seals in the sealing grooves 504 and 506 directing pressurized fluid through passage 416 and to the high pressure fluid inlets in the rotor housing 420 . The opening provision 502 provides a greater volume for the pressurized fluid to travel through the housing member 500 relative to the housing member 400 and reduces the pressure drop experienced by the pressurized fluid when it travels through passage 416 of the housing member 500 with respect to housing member 400. In addition, opening 502 allows manufacture of passage 416 without the need to manufacture passage opening 416a and eliminates the need for plug 306.

Although the invention has been shown and described particularly with reference to the preferred embodiment thereof, those skilled in the art will understand that various changes in shape and details can be made to it without departing from the spirit and scope of the invention. In addition, housings and / or components can be replaced with other satisfactory members to achieve similar results. In addition, a variety of materials can be used to form the various components and the relative sizes of the components can be varied. As a result, the claims are interpreted in a broad manner, consistent with the present invention.