Patent Description:
A prior art surgical bur is disclosed in <CIT>.

A surgical instrument may include a motor housing with a grip, an attachment, and a surgical tool. The attachment and the surgical tool may be replaced with other attachments and surgical tools. The attachment may connect to the motor housing and engage with a motor in the motor housing. The surgical tool may include a shaft and a surgical bur. The shaft extends from the surgical bur, engages with the attachment and is axially rotated by the motor.

Surgical burs are used to dissect, cut and/or shape bone during a surgical procedure. Surgical burs have various characteristics that can often conflict with each other. Some of these characteristics include cutting efficiency, stability, working length, and visibility. Improving one of these characteristics can negatively affect one or more of the other characteristics. As an example, when an enhancement is provided in an axial region (or at a tip of the surgical bur) or in a radial region (or at an equator of a surgical bur), cutting performance in other regions of the surgical bur can be negatively affected.

A length of a shaft of a surgical tool affects a working length of the surgical instrument. The working length refers to a length of the surgical instrument from a grip (or motor housing) to a cutting portion of a corresponding surgical bur. The working length includes an attachment length and an exposed length. The attachment length refers to a length of a corresponding attachment. The attachment is a portion of a surgical instrument extending from a motor (or main) housing to an exposed portion of a shaft of a surgical tool. The exposure length refers to a length of a surgical tool that is exposed subsequent to being engaged with an attachment of a surgical instrument. The exposure length is a length of a portion of the surgical tool extending from a distal end of the attachment. A distal end of a surgical bur can come in contact with tissue of a patient. The term "distal" means furthest away from a medical practitioner holding a surgical instrument with a surgical bur. The term "proximal" means towards the medical practitioner and away from the patient.

A surgeon may desire increased exposure without changing a length of a surgical tool (or working length). This may be provided by using a surgical tool with a shorter attachment and/or providing a variable exposure attachment. A variable exposure attachment allows a surgeon to change an amount of a shaft of a surgical tool that extends from the variable exposure attachment. Increasing the exposure tends to increase instability of the surgical tool. The longer the shaft of the surgical bur that extends away from the attachment, the more unstable the surgical bur can be during axial rotation of the surgical bur.

<CIT> discloses a surgical bur according to the preamble of claim <NUM>.

According to a first aspect, a surgical bur is provided according to claim <NUM>.

In a second aspect, a surgical bur is provided according to claim <NUM>.

The following examples include localized flute features for improving multiple characteristics of surgical burs. The term "localized" as used herein refers to one or more features of a surgical bur that are located in certain regions of the surgical bur and not located in other regions of the surgical bur. The localized flute features improve one or more characteristics in respective regions of the surgical burs without negatively affecting one or more characteristics of the surgical burs in other regions of the surgical burs. The localized flute features can augment cutting features of the surgical burs, provide stability, and/or improve cutting efficiency.

<FIG> shows a surgical instrument <NUM> incorporating a rotating surgical bur <NUM>, which is being used on a patient <NUM>. For example only, the patient <NUM> may be undergoing a neurological operation, as shown. <FIG> is provided for example purposes only. The surgical burs disclosed herein may be used in different tools and/or cutter assemblies and may be used for other procedures and/or operations. The surgical instrument <NUM> includes a tool driver <NUM> that has a motor <NUM> for axially rotating the surgical bur <NUM>. As shown, the surgical bur <NUM> may be used to dissect and/or shape a portion of bone and adjacent tissue of the patient <NUM> in a surgical access site <NUM>.

<FIG> is a perspective view of the surgical instrument <NUM>. The tool driver <NUM> includes a motor housing <NUM> connected to a hose or cable assembly <NUM>. The hose assembly <NUM> supplies external power and/or pneumatic pressure for the motor <NUM>. The tool driver <NUM> further includes an attachment <NUM> that connects to the motor housing <NUM> and engages with a surgical tool <NUM>. A distal end <NUM> of the surgical tool <NUM> includes the surgical bur <NUM> that is attached to a shaft <NUM>, which engages with the attachment <NUM>. Examples of surgical tools that may be used in replacement of the surgical tool <NUM> are shown and described below with reference to <FIG>.

In the following sections various surgical tools and surgical burs are disclosed. Although each of the surgical tools are described as having certain features such as certain angles, depths, etc., the features of each one of the surgical burs may be implemented on any other one of the surgical burs.

<FIG> show a surgical bur <NUM> incorporating discrete auxiliary flutes <NUM>. The surgical bur <NUM> is a match head (or 'neuro') style surgical bur and extends from a tapered shaft <NUM>. The shaft <NUM> may have a smaller diameter at the surgical bur <NUM> than at a proximal portion of the shaft <NUM>, which engages with an attachment (e.g. attachment <NUM> of <FIG>). The surgical bur <NUM> includes a body <NUM> with primary (or main) flutes <NUM> and the auxiliary flutes <NUM>. The main flutes <NUM> extend a full length of the surgical bur <NUM> from a proximal end <NUM> to a distal end (or tip) <NUM> of the surgical bur <NUM>. The main flutes <NUM> provide more aggressive cutting (cut away more material per revolution of the surgical bur) than the auxiliary flutes <NUM>. The auxiliary flutes <NUM> are included to provide localized features, such as localized stability and/or localized increased cutting efficiency. These features may be localized to distal, central, and/or proximal regions of the surgical bur <NUM>. These features can be provided in one region without negatively affecting another region of the surgical bur <NUM>.

Each of the main flutes <NUM> includes a proximal clearance surface <NUM>, a distal clearance surface <NUM>, a proximal rake surface <NUM> and a distal rake surface <NUM>. The clearance surfaces <NUM>, <NUM> and the rake surfaces <NUM>, <NUM> may be planar surfaces. The proximal clearance surfaces <NUM> when viewed radially may have positive, neutral or negative taper angles relative to an axis-of-rotation <NUM> of the surgical bur <NUM>. The distal clearance surfaces <NUM> when viewed radially may have positive taper angles relative to an axis-of-rotation of the surgical bur <NUM>. Taper angles of the shown distal clearance surfaces <NUM> are more positive than taper angles of the proximal clearance surfaces <NUM>.

First transition regions <NUM> exist respectively between the proximal clearance surfaces <NUM> and the distal clearance surfaces <NUM>. The first transition regions <NUM> may be convex-shaped regions. Second transition regions <NUM> exist respectively between the proximal rake surfaces <NUM> and the distal rake surfaces <NUM>. Each of the main flutes <NUM> includes a third transition region <NUM> that exists between (i) one of the proximal clearance surfaces <NUM> and one of the distal clearance surfaces <NUM> and (ii) one of the proximal rake surfaces <NUM> and one of the distal rake surfaces <NUM>. The third transition regions <NUM> may be concave-shaped regions and extend from the distal end <NUM> to the proximal end <NUM>.

Each proximal rake surface and distal rake surface pair has a cutting edge <NUM> that extends along an outer perimeter of the surgical bur <NUM> from the proximal end <NUM> to the distal end <NUM>. Primary (or first) relief surfaces <NUM> exist (i) between the main flutes <NUM> and the auxiliary flutes <NUM>, and (ii) between the cutting edges <NUM> of the main flutes <NUM> and the auxiliary flutes <NUM>.

The auxiliary flutes <NUM> include clearance surfaces <NUM>, transition regions <NUM>, and rake surfaces <NUM>. The clearance surfaces <NUM> and the rake surfaces <NUM> may be planar surfaces and/or may be semi-circular shaped. The clearance surfaces <NUM> may be referred to as secondary relief surfaces for the main flutes <NUM>. The transition regions <NUM> are concave-shaped regions between the clearance surfaces <NUM> and the rake surfaces <NUM>. The rake surfaces <NUM> include respective cutting edges <NUM>.

Although the auxiliary flutes <NUM> are shown as being located in distal regions of the surgical bur <NUM>, the auxiliary flutes <NUM> may be centrally located and extend across an equator <NUM> from the distal regions to proximal regions. The distal regions are distal of the equator <NUM>. The equator <NUM> refers to planar portion (or section) of the surgical bur <NUM> that is perpendicular to the axis-of-rotation <NUM> (or longitudinal axis) and is where a diameter of the surgical bur <NUM> is at a maximum. If the surgical bur <NUM> has a constant diameter for an extended portion of the surgical bur <NUM>, as in the example shown, the equator <NUM> is at the most distal portion of the surgical bur <NUM>, which has the maximum diameter. As another example, not forming part of the present invention, the auxiliary flutes <NUM> may extend from the distal regions to the proximal end <NUM>. As another example, the auxiliary flutes <NUM> may be in proximal regions of the surgical bur <NUM>. The proximal regions are proximal to the equator <NUM>.

The auxiliary flutes <NUM> are distinct from the main flutes <NUM>. Although the transition regions <NUM> of the auxiliary flutes <NUM> are shown as not extending radially from the axis-of-rotation <NUM>, the transition regions <NUM> may extend radially from the axis-of-rotation <NUM> and/or lie in a plane that includes the axis-of-rotation <NUM>. The auxiliary flutes <NUM> may be considered "cut-out" sections of relief surfaces of the main flutes <NUM>. As shown, each of the auxiliary flutes <NUM> extends from the distal end <NUM>, centrally between adjacent main flutes, and towards the equator <NUM> and/or proximal end <NUM>. Adjacent main flutes refer to two main flutes that do not have another main flute between the two main flutes. Similarly, adjacent auxiliary flutes refer to two auxiliary flutes that do not have another auxiliary flute between the two auxiliary flutes. A main flute may be adjacent to an auxiliary flute without any intervening flute between the main flute and the auxiliary flute.

As shown, the auxiliary flutes <NUM> are localized to the distal regions. The auxiliary flutes <NUM> provide increased relief angles for the main flutes <NUM>, which decreases drag during use, and as a result increases spinning efficiency at the distal end <NUM>. The additional cutting edges <NUM> of the auxiliary flutes <NUM> increase cutting efficiency at the distal end <NUM>.

Although the surgical bur <NUM> is shown as having two main flutes <NUM> and two auxiliary flutes <NUM> evenly distributed around the axis-of-rotation <NUM>, the surgical bur <NUM> may have any number of main flutes and auxiliary flutes. In addition, although the surgical bur <NUM> is shown as having a same number of main flutes as auxiliary flutes, the surgical bur <NUM> may have a different number of auxiliary flutes than main flutes. Further, more than one auxiliary flute may be cut-out of a relief surface of a main flute. For example, a first auxiliary flute may be located in a distal region of a relief surface of a main flute and a second auxiliary flute may be located in a central and/or proximal region of the relief surface. The second auxiliary flute may be distinct from the first auxiliary flute or the auxiliary flute may share a transition region between the first and second auxiliary flutes. The first and second auxiliary flutes may have respective taper angles, flute axial angles, inside angles, clock angles, radial rake angles, axial rake (or helix) angles, and depths. These angles are further defined below.

A single surgical bur may include auxiliary flutes of the same type and style or may include auxiliary flutes of different types and styles. The auxiliary flutes may have different taper angles, flute axial angles, inside angles, clock angles, radial rake angles, axial rake angles, and depths. Different types and styles of auxiliary flutes having different angles and depths are further described and illustrated below with respect to <FIG>. Although these angles and depths are described below with respect to ball head style surgical burs, the angles and depths apply to the surgical bur of <FIG> and/or other surgical burs encompassed by the numerous examples disclosed herein. Also, although specific angles and depths are shown in <FIG>, other angles and depths may be implemented.

<FIG> shows a surgical bur <NUM> incorporating auxiliary flutes <NUM>. The surgical bur <NUM> is a ball head style surgical bur. The auxiliary flutes <NUM> are in distal regions of the surgical bur <NUM>. The auxiliary flutes <NUM> may be similar to or different than the auxiliary flutes <NUM> of the surgical bur <NUM> of <FIG>.

<FIG> shows a surgical bur <NUM> incorporating auxiliary flutes <NUM> (one is visible in <FIG>). The surgical bur <NUM> is a ball head style surgical bur. The auxiliary flutes <NUM> are in middle (or central) regions of the surgical bur <NUM>. As shown, the auxiliary flutes <NUM> include clearance surfaces <NUM> and rake surfaces <NUM> that are planar and semi-circular. Transition regions <NUM> between the clearance surfaces <NUM> and the rake surfaces <NUM> may extend parallel to or have a positive or negative taper angle relative to an axis-of-rotation <NUM>. The auxiliary flutes <NUM> may be centered over an equator <NUM> of the surgical bur <NUM>. Each of the auxiliary flutes <NUM>, in the shown example, has a -<NUM>° radial rake angle, a <NUM>° inside angle, a -<NUM>° (left-hand) flute axial angle, and has a clock angle such that the auxiliary flute is centered (or at a mid-point) between adjacent main flutes. This arrangement provides stability for cutting via regions of the surgical bur near a mid-line (or equator).

<FIG> show ball style surgical burs having auxiliary flutes with different radial rake angles. <FIG> shows a distal end view of a ball style surgical bur <NUM> incorporating auxiliary flutes <NUM> with neutral radial rake angles <NUM>. Rake surfaces <NUM> of the auxiliary flutes <NUM> extend parallel to an axis-of-rotation (designated as point <NUM>). Planes that respectively include the rake surfaces <NUM> extend through the axis-of-rotation <NUM>.

<FIG> shows a distal end view of a ball style surgical bur <NUM> incorporating auxiliary flutes <NUM> with positive radial rake angles. Rake surfaces <NUM> of the auxiliary flutes <NUM>, when viewed at the distal end of the surgical bur <NUM>, are at positive rake angles relative to respective planes extending from outermost points <NUM> on cutting edges <NUM> of the rake surfaces <NUM> through an axis-of-rotation (designated as point <NUM>). One of the positive rake angles is designated as <NUM>. As shown, the positive rake angles are <NUM>°. A positive radial rake angle can increase cutting efficiency.

<FIG> shows a distal end view of a ball style surgical bur <NUM> incorporating auxiliary flutes <NUM> with negative radial rake angles. Rake surfaces <NUM> of the auxiliary flutes <NUM>, when viewed at the distal end of the surgical bur <NUM>, are at negative rake angles relative to respective planes extending from outermost points <NUM> on cutting edges <NUM> of the rake surfaces <NUM> through an axis-of-rotation (designated as point <NUM>). One of the positive rake angles is designated <NUM>. As shown, the positive rake angles are -<NUM>°. A negative radial rake angle and a neutral radial rake angle can provide a stabilizing effect.

Different surgical instruments may have different working lengths (or distances from a grip (or motor housing) to (i) a cutting portion of the surgical tool, or (ii) a cutting portion of a corresponding surgical bur. Typically, the longer the working length and/or the longer an exposed length (distance from attachment to surgical bur), the less stable a surgical bur is during use.

Negative to neutral rake angles can provide a stabilizing effect, whereas positive rake angles can improve cutting efficiency. The auxiliary flutes disclosed herein may have positive, neutral and/or negative axial rake (or helix) angles. Negative axial rake angles in the distal region (or tip) can provide a stabilizing effect, whereas positive radial rake angles at an equator or proximal region of a surgical bur can provide increased cutting efficiency. Incorporating auxiliary flutes with axial and/or radial rake angles that provide a stabilizing effect, allows for an exposed length of a corresponding surgical tool to be increased without negatively affecting stability while cutting. The increased instability associated with increasing the exposure length may be compensated for by the increased stability provided by the negative and/or neutral rake angles.

In the example shown in <FIG>, main flutes <NUM> of the surgical bur <NUM> have primary relief surfaces <NUM> with positive relief angles. The relief angles of the primary relief surfaces <NUM> are measured between the relief surfaces <NUM> and tangential lines (one tangential line is designated <NUM>) extending (i) through first outermost points <NUM> on the cutting edges <NUM> of rake surfaces <NUM> of the main flutes <NUM>, and (ii) perpendicular to lines (one line is designated <NUM>) extending between the first outermost points <NUM> and the axis-of-rotation <NUM>. The relief angles (one relief angle is designated <NUM>) of the primary relief surfaces <NUM> may be neutral or negative. The positive relief angles do not track a circle <NUM> extending through the first outermost points <NUM>. The positive relief angles provide increased operating efficiency due to less surface (or tissue) contact and thus less drag. Clearance surfaces <NUM> (or secondary relief surfaces) of the auxiliary flutes <NUM> have higher positive relief angles than the relief angles of the primary relief surfaces <NUM>.

The auxiliary flutes <NUM> have relief surfaces <NUM> that may have neutral relief angles (one relief angle is designated <NUM>), as shown. The relief angles of the relief surfaces <NUM> are measured between the relief surfaces <NUM> and tangential lines (one tangential line is designated <NUM>) extending (i) through second outermost points <NUM> on the cutting edges <NUM> of the rake surfaces <NUM>, and (ii) perpendicular to lines (one line is designated <NUM>) extending between the second outermost points <NUM> and the axis-of-rotation <NUM>. The relief angles of the relief surfaces <NUM> of the auxiliary flutes <NUM> may be positive or negative. The neutral relief angles (i) track an inner circle <NUM> that extends through the second outermost points <NUM>, and (ii) provide a stabilizing effect.

<FIG> show a ball style surgical bur <NUM> illustrating auxiliary flutes <NUM> with neutral flute axial angles. Transition regions <NUM> between clearance surfaces <NUM> and rake surfaces <NUM> of the auxiliary flutes <NUM> extend parallel to an axis-of-rotation <NUM>. Put another way, transition lines (one transition line is designated <NUM>) extending axially between the clearance surfaces <NUM> and the rake surfaces <NUM> are parallel to the axis-of-rotation <NUM>. The transition lines may be parallel to or refer to edges of the clearance surfaces <NUM>. The transition lines may be parallel to or refer to edges of the rake surfaces <NUM>. As a result, flute axial angles of the auxiliary flutes <NUM> relative to the axis-of-rotation are <NUM>°.

<FIG> show a ball style surgical bur <NUM> illustrating auxiliary flutes <NUM> with left-hand flute axial angles. Transition regions <NUM> between clearance surfaces <NUM> and rake surfaces <NUM> of the auxiliary flutes <NUM> do not extend parallel to an axis-of-rotation <NUM> when viewed head-on (or from a direction directly opposite the corresponding transition region). A left-hand flute axial angle <NUM> is shown between lines <NUM>, <NUM> that extend respectively parallel to (i) a transition line <NUM> extending in a corresponding one of the transition region <NUM> between one of the clearance surfaces <NUM> and one of the rake surfaces <NUM>, and (ii) the axis-of-rotation <NUM>. The transition line <NUM> may be parallel to or refer to an edge of the corresponding clearance surface. The transition line <NUM> may be parallel to or refer to an edge of the corresponding rake surface. In the example shown, the left-hand flute axial angle is <NUM>°.

<FIG> show a ball style surgical bur <NUM> illustrating auxiliary flutes <NUM> with right-hand flute axial angles. Transition regions <NUM> between clearance surfaces <NUM> and rake surfaces <NUM> of the auxiliary flutes <NUM> do not extend parallel to an axis-of-rotation <NUM> when viewed head-on. A right-hand flute axial angle <NUM> is shown between lines <NUM>, <NUM> that extend respectively parallel to (i) a transition line <NUM> extending in one of the transition regions <NUM> between one of the clearance surfaces <NUM> and one of the rake surfaces <NUM>, and (ii) the axis-of-rotation <NUM>. The transition line <NUM> may be parallel to or refer to an edge of the corresponding clearance surface. The transition line may be parallel to or refer to an edge of the corresponding rake surface. In the example shown, the right-hand flute axial angle is <NUM>°.

A flute axial angle may be set to improve stability and/or cutting efficiency. A radial rake angle is related to a flute axial angle, such that the radial rake angle may increase or decrease longitudinally along a length of the flute depending upon whether the flute axial angle is a left-hand flute axial angle or a right-hand flute axial angle. For example, a right-hand flute axial angle has a lowest corresponding rake angle at a distal end of the flute. The radial rake angle increases in size towards a proximal end of the flute.

<FIG> show ball style surgical burs <NUM>, <NUM> illustrating auxiliary flutes <NUM>, <NUM> having negative and positive taper. The auxiliary flutes <NUM>, <NUM> extend across corresponding equators of the surgical burs <NUM>, <NUM>. The auxiliary flutes <NUM>, <NUM> may be centered on the equators (one half of each of the auxiliary flutes <NUM>, <NUM> is located distal of the equator and the other half of each of the auxiliary flutes <NUM>, <NUM> is located proximal to the equator). A larger portion of the auxiliary flutes <NUM>, <NUM> may be located proximal to the equator, for example, when the auxiliary flutes <NUM>, <NUM> have a negative taper. A larger portion of the auxiliary flutes <NUM>, <NUM> may be located distal to the equator, for example, when the auxiliary flutes have positive taper. <FIG> shows the auxiliary flutes <NUM> having negative taper. Transition regions between clearance surfaces (one clearance surface is designated <NUM>) and rake surfaces (one rake surface is designated <NUM>) of the auxiliary flutes <NUM> do not extend parallel to an axis-of-rotation <NUM> when viewed radially from sides facing (or opposing) the corresponding rake surfaces. A taper angle <NUM> is shown between lines <NUM>, <NUM> that extend respectively parallel to (i) a transition line <NUM> extending in a transition region between the clearance surface <NUM> and the rake surface <NUM>, and (ii) the axis-of-rotation <NUM>. The transition line <NUM> may be parallel to or refer to an edge of the clearance surface <NUM>. The transition line <NUM> may be parallel to or refer to an edge of the rake surface <NUM>.

<FIG> shows the auxiliary flutes <NUM> having positive taper. Transition regions between clearance surfaces (one of the clearance surfaces is designated <NUM>) and rake surfaces (one of the rake surfaces is designated <NUM>) of the auxiliary flutes <NUM> do not extend parallel to an axis-of-rotation <NUM> when viewed radially from sides facing (or opposing) the corresponding rake surfaces. A taper angle <NUM> is shown between lines <NUM>, <NUM> that extend respectively parallel to (i) a transition line <NUM> extending in a transition region between the clearance surface <NUM> and the rake surface <NUM>, and (ii) the axis-of-rotation <NUM>. The transition line <NUM> may be parallel to or refer to an edge of the clearance surface <NUM>. The transition line <NUM> may be parallel to or refer to an edge of the rake surface <NUM>.

The taper angles of the auxiliary flutes disclosed herein may be set to locate the auxiliary flutes in regions of the corresponding surgical burs for predetermined stability and cutting effects. For example, a more positive taper moves the corresponding auxiliary flute towards a distal end of the corresponding surgical bur. A more negative taper moves the corresponding auxiliary flute towards a proximal end of the corresponding surgical bur.

<FIG> illustrate ball style surgical burs <NUM>, <NUM>, <NUM> having auxiliary flutes <NUM>, <NUM>, <NUM> with different depths D1, D2, D3. <FIG> and <FIG> show the surgical bur <NUM> with the auxiliary flutes <NUM> that have the shallow depth D1 (a depth less than or equal to a first predetermined depth). <FIG> and <FIG> show the surgical bur <NUM> with the auxiliary flutes <NUM> that have the deep depth D2 (a depth greater than or equal to the second predetermined depth). <FIG> shows the surgical bur <NUM> with the auxiliary flutes <NUM> with an intermediate depth D3 (a depth within a predetermined range that is greater than the first predetermined depth and less than a second predetermined depth). The depth D3 is greater than the depth D2, which is greater than the depth D1. The depth of an auxiliary flute refers to how far into a surgical bur the auxiliary flute is cut relative to (i) a corresponding relief surface of a main flute, and/or (ii) a relief surface of the auxiliary flute. Length (or surface area) of an auxiliary flute and how much (or magnitude at which) a flute affects surgical tool performance are based on a depth of the auxiliary flute. In general, the deeper the auxiliary flute the longer the auxiliary flute. Also, deeper auxiliary flutes tend to move clearance surfaces (non-cutting surfaces) of the auxiliary flutes closer to adjacent main flutes, which increase sizes of "bites" of the auxiliary flutes and as a result increase cutting efficiency.

<FIG> illustrate ball style surgical burs <NUM>, <NUM>, <NUM> with auxiliary flutes <NUM>, <NUM>, <NUM> having corresponding inside flute angles <NUM>, <NUM>, <NUM>. The inside flute angles <NUM>, <NUM>, <NUM> refer to angles between clearance surfaces <NUM>, <NUM>, <NUM> and respective rake surfaces <NUM>, <NUM>, <NUM> of the auxiliary flutes <NUM>, <NUM>, <NUM>. <FIG> shows the ball style surgical bur <NUM> illustrating the first inside flute angle <NUM> (e.g., <NUM>°). <FIG> shows the ball style surgical bur <NUM> illustrating the second inside flute angle <NUM> (e.g., <NUM>°). <FIG> shows the ball style surgical bur <NUM> illustrating a shallow auxiliary flute with the third inside flute angle <NUM> and a particular radial rake angle (e.g., -<NUM>°).

Similar to depths of auxiliary flutes, inside flute angles can be adjusted to move clearance surfaces (non-cutting surfaces) of the auxiliary flutes towards cutting edges of adjacent main flutes. The larger the inside flute angles the closer the clearance surfaces of the auxiliary flutes are to the cutting edges of the adjacent main flutes. Also, similar to depths of auxiliary flutes, inside flute angles move where non-cutting surfaces of the auxiliary flutes intersect a tool surface (e.g., a relief surface of a main flute). The inside flute angles may be maintained at constant values while radial rake angles and flute depths are changed.

<FIG> illustrate ball style surgical burs <NUM>, <NUM>, <NUM> having auxiliary flutes <NUM>, <NUM>, <NUM> having different clock angles <NUM>, <NUM>, <NUM>. The clock angles <NUM>, <NUM>, <NUM> refer to, when viewing the auxiliary flutes <NUM>, <NUM>, <NUM> at a distal end of the surgical burs <NUM>, <NUM>, <NUM>, angular positions of the auxiliary flutes <NUM>, <NUM>, <NUM> relative to respective adjacent main flutes <NUM>, <NUM>, <NUM>. The clock angles indicate (i) angular distances about axis-of-rotations <NUM>, <NUM>, <NUM> between the main flutes <NUM>, <NUM>, <NUM> and the auxiliary flutes <NUM>, <NUM>, <NUM>, and (ii) widths of primary relief surfaces <NUM>, <NUM>, <NUM> between the main flutes <NUM>, <NUM>, <NUM> and the auxiliary flutes <NUM>, <NUM>, <NUM>.

<FIG> shows a distal end view of the ball style surgical bur <NUM> having the auxiliary flutes <NUM> with <NUM>° clock angles. <FIG> shows a distal end view of the ball style surgical bur <NUM> having the auxiliary flutes <NUM> with <NUM>° clock angles. <FIG> shows a distal end view of the ball style surgical bur <NUM> having the auxiliary flutes <NUM> with <NUM>° clock angles.

Clock angles locate auxiliary flutes relative to main flutes at positions about an axis-of-rotation of the corresponding surgical bur. If the auxiliary flutes (first auxiliary flutes) have small clock angles or large clock angles, additional (or second) auxiliary flutes may be incorporated between the first auxiliary flutes and the corresponding main flutes. For example, a ball style surgical tool may include both the auxiliary flutes of <FIG> and the auxiliary flutes of <FIG>. The clocking angles (or clocking positions) affect how much (or magnitude at which) the auxiliary flutes affect stability and/or cutting performance.

In the following <FIG>, ball style surgical burs <NUM>, <NUM>, <NUM> are disclosed with auxiliary flutes <NUM>, <NUM>, <NUM> located in distal regions and proximate to tips <NUM>, <NUM>, <NUM> of the surgical burs <NUM>, <NUM>, <NUM>. In these locations, the auxiliary flutes <NUM>, <NUM>, <NUM> have radial rake angles and axial rake angles. The radial rake angles affect lateral cutting and the axial rake angles affect distal cutting of the surgical burs <NUM>, <NUM>, <NUM>.

<FIG> show the ball style surgical bur <NUM> illustrating the auxiliary flutes <NUM> with neutral rake angles (<NUM>°). <FIG> shows a distal end view of the surgical bur <NUM> and illustrates the auxiliary flutes <NUM> with neutral axial (or helix) rake angles. A circled dashed line region <NUM> indicates a portion of a corresponding auxiliary flute with an effective axial rake component. <FIG> shows a radial side view of the ball style surgical bur <NUM> and illustrates the auxiliary flutes <NUM> with neutral radial rake angles. A circled dashed line region <NUM> indicates a portion of a corresponding auxiliary flute with an effective radial rake component.

<FIG> show the ball style surgical bur <NUM> illustrating the auxiliary flutes <NUM> with negative rake angles. <FIG> shows a distal end view of the ball style surgical bur <NUM> and illustrates the auxiliary flutes <NUM> with negative axial rake angles. An arrow <NUM> indicates a portion of a corresponding auxiliary flute with a rake surface <NUM> that is exposed when viewed from a distal end or tip <NUM> of the surgical bur <NUM>. Exposure of rake surfaces of the auxiliary flutes <NUM> is increased over that shown in <FIG>, which indicates magnitude of the negative axial rake of the auxiliary flutes <NUM>. <FIG> shows a radial side view of the ball style surgical bur <NUM> and illustrates the auxiliary flutes <NUM> with negative radial rake angles. An arrow <NUM> indicates a portion of a corresponding auxiliary flute with the rake surface <NUM> that is exposed when viewed radially. As shown, the auxiliary flutes <NUM> have increased rake surface exposure over the rake surfaces of the auxiliary flutes <NUM> of <FIG>, illustrating the negative radial rake of the auxiliary flutes <NUM>.

<FIG> show the ball style surgical bur <NUM> illustrating the auxiliary flutes <NUM> with negative rake angles. The rake angles of the ball style surgical bur <NUM> are more negative than the rake angles of the ball style surgical bur <NUM> of <FIG>. <FIG> shows a distal end view of the ball style surgical bur <NUM> and illustrates the auxiliary flutes <NUM> with negative axial rake angles. Exposure of rake surfaces <NUM> of the auxiliary flutes <NUM> is increased over that shown in <FIG>, which indicates magnitude of the negative axial rake of the auxiliary flutes <NUM>. The auxiliary flutes <NUM> have a left-hand flute axial angle which manifested the increase in negative axial rake over the auxiliary flutes <NUM> of <FIG>. <FIG> shows a radial side view of the ball style surgical bur <NUM> and illustrates the auxiliary flutes <NUM> with negative radial rake angles. As shown, the auxiliary flutes <NUM> have increased rake surface exposure over the rake surfaces of the auxiliary flutes <NUM> of <FIG>, illustrating the increased negative radial rake of the auxiliary flutes <NUM>.

Auxiliary flute features are described above that are localized on surgical burs to augment cutting performance for particular uses during, for example, dissection. Auxiliary flutes and/or flute features are disclosed as being localized in a distal region, a middle region (or near an equator), and/or a proximal region of a surgical bur. The auxiliary flutes may transition between regions of the surgical bur, such that the auxiliary flutes provide a certain feature in a first region and a different feature in a second region. The auxiliary flutes do not extend continuously from a proximal end of a surgical bur to a tip (or distal end) of the surgical bur. The disclosed features provide numerous surgical bur geometries that may be incorporated into a surgical bur to achieve requirements for cutting efficiency and/or cutting stability.

Numerous specific details are set forth to provide a thorough understanding of embodiments of the present disclosure. In some example embodiments, well-known device structures, and well-known technologies are not described in detail.

Claim 1:
A surgical bur comprising:
a plurality of primary flutes (<NUM>) comprising (i) first clearance surfaces (<NUM>), and (ii) first rake surfaces (<NUM>) with first cutting edges (<NUM>), wherein the plurality of primary flutes extend from a proximal end of the surgical bur to a distal end (<NUM>) of the surgical bur; and
a plurality of auxiliary flutes (<NUM>, <NUM>, <NUM>) comprising (i) second clearance surfaces (<NUM>), and (ii) second rake surfaces (<NUM>) with second cutting edges (<NUM>), wherein at least one of the plurality of auxiliary flutes is located between a pair of adjacent ones of the plurality of primary flutes;
characterized in that the plurality of auxiliary flutes are localized in distal regions, or are centrally localized and extending from distal regions to proximal regions of the surgical bur.