Spherical osteotomy device and method

A spherical osteotomy device for the efficient surgical sectioning of bone includes a part spherical body and a shank. The part spherical body includes an outer surface, an inner surface, a cutting end between the outer surface and the inner surface, an axis extending from the outer surface through the inner surface, and an origin on the axis. The inner surface has a substantially constant radius extending from the origin. The shank extends outwardly from the outer surface of the body and is substantially aligned with the axis. Other embodiments of an osteotomy device are described. Also provided is a method of using the osteotomy device for performing spherical osteotomies.

FIELD OF INVENTION

This invention relates generally to osteotomy devices for use in the surgical cutting of bones, and more specifically to spherical osteotomy devices for use in surgical division or sectioning of bones and a method therefore, particularly spherical osteotomy devices for use in performing “true dome” osteotomies.

BACKGROUND

Osteotomy is defined as a procedure for surgical division or sectioning of a bone. Displacement osteotomy is the surgical division of a bone and shifting of the divided ends to change the alignment of the bone or to alter weight-bearing stresses. This procedure is typically utilized by orthopedic surgeons to correct for malalignment and malorientation, including uniapical and multiapical deformities of the bone, as well as the treatment for compartmental diseases. The goal of displacement osteotomies is to create congruent matching surfaces to align, stabilize, and maximize contact between the corresponding bone sections. Osteotomies may include a number of different types of bone sectioning procedures that result in two corresponding sections of the bone which are then reoriented until a desired alignment between the bone sections is achieved. In order to improve stability, distribute the load evenly, eliminate abnormal stress, and aid healing, surgeons strive to maximize the match or contact area between two corresponding surfaces when surgically sectioning the bone. Representative types of bone cuts include simple transverse, obliqued cuneiform, stairstep, simple to complex wedges, barrel-vault, and dome shaped cuts. In practice, a surgeon may choose a specific cut configuration in order to achieve a particular reconfiguration of the bone being treated.

Although so called “dome osteotomy” has been known for decades, the term “dome osteotomy” has been used to refer conventionally to semi-cylinder, i.e., half or part (partially) cylindrical, shaped surgical cuts. Specifically, amongst experts within the field, “cylindrical osteotomy” would be a more accurate descriptor for these types of so called “dome” osteotomies, as it is well understood by all to be a cylindrically shaped cut. Although resulting shapes of so called “dome” osteotomy are not domes, the following terms have been used in the scientific literature to refer to osteotomies wherein corresponding bone cuts are shaped like a semi-cylinder: dome, spherical, barrel-vault, focal dome (reversed dome), crescentic, and arcuate. These conventional forms of semi-cylindrically shaped osteotomies are better described as barrel-vault osteotomies, and will be described accordingly herein below. Further, the term “dome osteotomy” has been used in the literature and within the field of corrective osteotomy to describe barrel-vault osteotomy, however, the field of corrective osteotomy has lacked a method and device to accomplish, as described below with respect to the invention herein presented, what will be termed “true dome” or spherical osteotomy.

In barrel-vault osteotomy, a bone is sectioned by oscillating a saw blade around the central axis of the cylinder while cutting the bone. Barrel-vault osteotomy may be used to correct angulation about the central axis of the cylindrical cut and translation along the central axis of the cylindrical cut. The barrel-vault osteotomy provides and allows correction in two-dimensions, which sometimes results in undesirable secondary translation because of imparted limitation of two-dimensional repositioning of the bone portions. In this respect, barrel-vault osteotomy cannot be used to correct axial rotations of the bone without creating gaps and instability between bone segments thereby being a major limitation of so called “barrel-vault” osteotomies. The success of barrel-vault osteotomies relies heavily on meticulous pre-operative planning, and while it may be used to correct radial deformities in the frontal and sagittal planes, one of its major disadvantages is the limited ability to correct axial rotational deformities. Accordingly, it would be desirable to provide a device capable of cutting a bone into corresponding sections that allows for correction in more than two-dimensions.

There are a variety of devices and methods available to accomplish these so called “barrel-vault” osteotomies. One method includes drilling a series of holes in the bone along a planned arc. In one example, U.S. Pat. No. 6,190,390 discloses an apparatus and method for the surgical realignment of the knee through proximal tibial osteotomy. The apparatus has an arcuate profile configuration for establishing a series of parallel holes forming the desired semi-cylindrical contour of the barrel-vault cut. In addition to the general disadvantages of “barrel-vault” osteotomies mentioned above, such a method undesirably creates ridges between adjacent sets of drilled parallel holes making alignment more difficult and gaps between bone portions more probable.

According to another example, U.S. Pat. No. 4,955,888 discloses a biradial saw blade with an arcuate body, powered by oscillating motion that is used to create the barrel-vault osteotomy. Such saw blades are typically associated with a saw assembly which operates to displace the blade in a reciprocating motion by oscillating the blade around the drive axis of the saw assembly. The saw blade has a curved cutting edge at the end of the body shaped as a part of a cylinder for making barrel-vault shaped surgical cuts. While the cut resulting from the use of the biradial saw blade provides for a better match of the two surfaces of both bone portions, the heat and friction produced by the saw blade may be detrimental to the bone, specifically for allowing proper healing thereof. Also, other conventional “barrel-vault” saw blades may include a partially cylindrically shaped body having a cutting member on its leading edge.

Conventional blades are limited in providing semi-cylindrical cuts of the bone which limit the correction in the bone, particularly when correcting deformities that lie in two planes, such as the frontal and sagittal planes. Correction of deformities in two planes requires meticulous preoperative planning in order to determine the central axis about which the cut in the bone is to be made. This is especially crucial if the bone portions are to be properly positioned to correct the deformity. Cutting the bone about a different central axis will only allow, at best, partial correction in the two planes. Further, it is desirable to provide improvement for the correction of malalignment, malorientation and compartmental disease, including other deformities of the bone by osteotomy procedures and tools. Accordingly, it would be desirable to provide an osteotomy tool for cutting bone that increases the adjustability of the bone portions, achieves optimal bone contact, and improves primary stability. It is also desirable to provide an osteotomy tool that is less dependent upon cutting the bone precisely about a determined central axis when attempting to achieve proper correction.

Another disadvantage associated with the use of so-called “barrel-vault” osteotomies is the limited ability to correct axial rotational deformities. Correction of other deformities may also be difficult to make, particularly when a correction of the deformity requires cutting the bone in a less accessible location. This makes it increasingly difficult for a surgeon to provide the corrective cut, as described above, where it is needed. Another disadvantage of barrel-vault osteotomies is the bone portions, after severance, may only be repositioned with respect to one another about two principal dimensions, one of the principal dimensions being an angular displacement or rotation about the central axis, and the other principal dimension being a lateral displacement or position along the central axis. The angular displacement or rotation allows the bone pieces to be rotated with respect to one another about the central axis to the desired correction. The lateral displacement or position allows the bone pieces to be positioned with respect to each other along the central axis to the desired correction. Also, the bone pieces may obtain the desired correction through a small combination of lateral displacements and angular displacements. Lateral displacement of the bone pieces is limited to the extent that the bone portions include sufficient surface contact for proper healing to occur. Angular displacement of the bone pieces provides for better bone-to-bone contact than lateral displacement, however, angular displacement is still limited if the bone portions are to be maintained with sufficient surface contact in order to provide for proper healing. Accordingly, it would be desirable to provide improved osteotomy of a bone to allow for greater surface contact between the repositioned cut pieces. It is further desirable to provide an osteotomy tool for severing a bone to provide correction of the bone pieces in more than two dimensions.

U.S. Pat. No. 5,643,270 discloses a multi-plane curvilinear saw to be used with corresponding guide, and particularly adapted for cutting the bones in a digit, and more specifically for shaping the end of a bone in a digit by ostectomy for fusion with another member of a joint in a digit. Ostectomy refers to surgical removal of a bone or part of a bone. The conventional device is specifically designed to work similarly to a surgical chisel removing cartilage and spongy bone from one side of the joint surface. The saw blade includes a hemispherically-shaped body having a flat top and a shank extending from the flat top, and a cutting edge along an exposed edge. This conventional device provides the use of a saw guide in order to ensure accuracy, restrict the movement of the cutting teeth to the path defined by the curved slots, and to avoid slipping of the saw and inadvertent cutting of the surrounding tissue. The saw can be delicately translated, tilted and/or rotated to a limited degree about the end of the bone by the surgeon to make the exact cut until the flat portion of the saw rests flat on the guide. The guide is a necessary component, as without it the saw would slide off the end of the bone. A curved shape occurs on the end of the bone, because the cutting edge with its arc is guided by a saw guide about the arcuate path. Whereas the conventional device is advantageous for general ostectomies for shaping the end of a bone, it is impractical for precise osteotomy of a bone. Such conventional devices undesirably require metal to metal contact between the cutting blade and the guide. Orthopedic surgeons try to avoid contact of the saw blade with other materials (such as metal or plastic) in order to protect their instruments (avoid unnecessary wear and galling), to avoid unnecessary heat production and potential thermal necrosis of the underlying tissue, as well as to avoid material shavings getting into the open wound. Moreover, this conventional device and method are not suitable for true dome osteotomies because, while it may create a curvilinear cut partially into the bone, the device would wedge itself between opposing bone portions during the cutting process due to the shape of the sectioning element or blade. Furthermore, the conventional device may damage the bone by creating too much pressure and heat, caused by friction, during the cutting procedure. Moreover, such conventional devices having a flat top on the upper end of the device restrict full cutting or sectioning of the bone into two portions, particularly when the flat top of the device reaches the parallel surface of the guide with respect to the axis of the bone that prevents complete cutting of the bone.

Accordingly, it would be desirable to provide a device capable to cutting a bone into corresponding sections resulting in a “true dome” or spherical osteotomy.

Accordingly, it is also desirable to provide an osteotomy tool and method for “true dome” or spherical osteotomies that result in two substantially congruent (one concave and one convex) surfaces after cutting a bone.

SUMMARY OF THE INVENTION

Accordingly, the invention presented herein accomplishes a substantially spherical or “true dome” shape when cutting bone, facilitating correction in three dimensions and aiding the healing process of the cut bones.

In embodiments of the invention, a “true dome” or spherical osteotomy device may be used to cut a bone into two substantially mating portions, allowing correction of the bone to be accomplished by rotating bone portions about their substantially mating surfaces, which may also allow correction for axial rotation without unnecessary secondary translation. Moreover, “true dome” osteotomy provides for three-dimensional adjustability of the bone while maximizing bone-to-bone surface contact and stability. Advantageously, procedures utilizing the spherical osteotomy device require less complex pre-operative planning and provide more accurate correction.

Embodiments of the invention provide several important advantages. Specifically, a “true dome” or spherical osteotomy device, including a method of using the spherical osteotomy device, may create dome shaped mating surfaces as opposed to semi-cylindrical cuts conventionally made, may provide for match of the proximal and distal fragments of the osteotomy, may optimize dome height, may minimize bone loss, may decrease the complexity of pre-operative planning, may allow the surgeon to make intraoperative adjustments to attain desired correction, may not unacceptably wedge or heat bone portions during cutting, may avoid unnecessary heat and burning, may minimize damage to bone tissue and the surrounding soft tissue, may avoid metal to metal contact of surgical instruments, and may aid faster and more reliable healing of the bone. Another advantage, a spherical osteotomy device may be self-guiding and self-centering within the cut being made in the bone, giving the surgeon options in planning the surgical approach around soft tissue structures.

In one embodiment of the invention, a spherical osteotomy device for the efficient surgical sectioning of bone is described that includes a partially spherical body and a shank. The part spherical body includes an outer surface, an inner surface, a cutting end between the outer surface and the inner surface, an axis that extends from the outer surface through the inner surface, and an origin located on the axis. The inner surface has a substantially constant radius extending from the origin. The shank extends outwardly from the outer surface of the body and is substantially aligned with the axis. Optionally, the spherical osteotomy device may be attached to an osteotome handle or to a power tool such as an oscillating saw. The spherical osteotomy may be used to cut bones or other anatomical structures into two portions in such a way as to facilitate repositioning of oppositely opposed substantially mating surfaces in the desired position or orientation, thereby also to aid healing.

The bone saw bit advantageously allows the bone portions after surgical severance to be repositioned together in at least one of three different degrees of motion, because the bone saw bit cuts a “true dome” osteotomy into each bone portion. One of the bone portions will have a convex surface that substantially mates with the other bone portion having a concave surface. Because the surfaces have mating contours, the bone portions relatively may be rotated about the longitudinal axis of the bone and tilted in either of two dimensions about the bone to achieve repositioning in three dimensions.

Other embodiments of an osteotomy device are described.

Also provided is a method of using the osteotomy device for performing “true dome” or spherical osteotomies. The method of the instant invention involves the following:(1) Providing a sectioning blade of the type described herein, wherein the sectioning blade is operably secured to a device for oscillating the blade;(2) Defining a center of rotation in the bone to be sectioned;(3) Actuating the device to oscillate the blade about the origin of the blade;(4) Engaging the blade against the bone to be sectioned; and(5) Sectioning the bone by passing the blade through the bone while rotating the blade about the center of rotation.

In a preferred method the above indicated procedural steps are supplemented by the following additional steps, namely:(A) Defining a longitudinal axis of the bone to be sectioned;(B) Defining proximal and distal longitudinal axis lines of the bone to be sectioned;(C) Finding the intersection of the proximal and distal longitudinal axis lines, denominated as a center of rotation of angulation (CORA);(D) Generally aligning the origin of the sectioning blade with the CORA by positioning the blade so that the origin of the sectioning blade is at the same location as the point of intersection—in some cases the surgeon can choose an off-set CORA to accomplish the osteotomy;

Steps (A) through (D) are performed subsequent to step (2) above and prior to step (3) above.

In a further embodiment of the instant method steps A-D are supplemented by a further step (E) wherein step (E) comprises sectioning the bone by passing the blade through the bone while rotating the blade about the center of rotation while retaining the origin of the blade substantially at the defined CORA.

Step (E) is performed simultaneously with step (5) above.

Advantageously, the osteotomy device may be utilized in a variety of surgical procedures beyond “true dome” or spherical osteotomies, such as bone fracture repair in humans and animals.

Other advantages, features and alternative aspects of the invention will become apparent when viewed in light of the detailed description of the various embodiments of the invention when taken in conjunction with the attached drawings and appended claims.

DETAILED DESCRIPTION OF THE INVENTION

The illustrations presented herein are, in some instances, not actual views of any particular osteotomy device, “true dome” osteotomy device, spherical osteotomy device, bone saw bit, cutting element, hard facing material or other feature of an osteotomy bit or device, but are merely idealized representations which are employed to describe the invention. Additionally, like elements and features among the various drawing figures are identified for convenience with the same or similar reference numerals.

“True dome” or spherical osteotomy devices, hereinafter “bone saw bits,” suitable for osteotomy or other surgical cutting of bone are presented. Bone saw bits for surgically severing bone are now presented together with some terminology to facilitate a proper understanding of the invention.

The term “spherical” as used herein means a characteristic of a sphere over any portion of a sphere and is not to be limited to a complete sphere, including, but not limited to, a hollow spherical structure. Also, the term “spherical” may refer to an inner surface, an outer surface, or an inner surface and an outer surface of a sphere, including partial portions thereof.

The term “part spherical” as used herein means a characteristic of a sphere or a part sphere over any portion of a sphere and is not to be limited to a sphere or part sphere or a hollow sphere. Also, the term “part spherical” may refer to an inner surface, an outer surface, or an inner surface and an outer surface of a sphere or part sphere, including partial portions thereof.

The term “hemispherical” as used herein means a characteristic of a hemisphere over any portion of a hemisphere and is not to be limited to a hemisphere. Also, the term “hemispherical” may refer to an inner surface, an outer surface, or an inner surface and an outer surface of a hemisphere, including partial portions thereof.

As used herein the term “true dome” will be defined as a curved surface, produced by a cutting action, wherein the radius of curvature of that curved surface is constant or substantially constant over the entire curved surface.

FIG. 1is a perspective view of a device, or bone saw bit,10in accordance with an embodiment of the invention.FIGS. 1A and 1Bare further views of the bone saw bit10. Reference may also be made toFIG. 2which shows another perspective view of the bone saw bit10. The bone saw bit10includes a part spherical body11and a cutting end12, which together form key features of the invention. The part spherical body11is made of a suitably rigid material such as surgical steel, and may include other materials suitable for the surgical severance of bone, particularly in aseptic environments.

The bone saw bit10provides for the efficient surgical sectioning of bone (described below) and includes the part spherical body11having a shank14extending therefrom along an axis16. The shank14allows the bone saw bit10to be attached to a chuck e.g. a three pronged chuck (not shown), of an oscillating saw (not shown). The oscillating saw rotationally drives the bone saw bit10, as indicated by the double-ended arrow15shown inFIG. 2, to efficiently penetrate a desired member, such as bone, in order to obtain an efficient, optimal or “true” dome on both pieces of the severed member. The dome on one severed member will result in a convex dome, while the dome on the other severed member will result in a concave dome.

The shank14may have any attachment connection, such as a threaded stem or a quick release, for example without limitation. The attachment connection will allow the bone saw bit10to be attached to any device, such as a power tool or hand operated tool for improved cutting control or usability. Also, while the shank14is shown as being integral with the part spherical body11, the shank14may also be a separate member that is coupled to the part spherical body11. Further, the shank14may include a hub13(seeFIG. 2) as shown.

The part spherical body11also includes an outer surface18, an inner surface20. The cutting end12extends between the outer surface18and the inner surface20. The axis16may extend axially inline with the shank14and passes from the outer surface18through the inner surface20of the part spherical body11. The axis16includes an origin or center as indicated by indicia O as labeled. The inner surface20is substantially characterized by having a constant radius R extending from the origin O Advantageously, the constant radius R allows the bone saw bit10to efficiently and smoothly transition over, and rotate about, the member it is cutting. Further, efficient usage of the bone saw bit10is provided for because the outer surface18may also be substantially characterized by a constant radius R′ over the substantial portion thereof, which also advantageously reduces heat generation on the bone caused by friction while helping to prevent necrosis of the bone. Another advantage of the substantially constant radius R of the inner surface20and the radius R′ of the outer surface18is that the bone saw bit10is less likely to impinge upon either piece of a bone during cutting thereby avoiding the ill healing effects caused by necrosis.

With reference also toFIG. 3and continued reference toFIG. 1, the cutting end12of the part spherical body11extends as an arc BDC that lies substantially within a plane24intersecting the origin O. The arc BDC has a radius SR that is substantially equal to the radius “R” of part spherical body11allowing a uniform and non-complex cut to be made by the bone saw blade10. The radius R and radius R′ allow the part spherical body11to substantially follow precisely within the path made by the cutting end12through the bone substantially without impingement thereupon. The dimensional difference between radius R and the radius R′ is the thickness of the bone saw blade11. While the radius SR of the arc BDC and the radius “R” are substantially equal, it is recognized that they may vary to a slight degree.

Optionally, the cutting end12may extend as an arc BDC between the outer surface18and the inner surface20of the part spherical body11.

Returning to the bone saw bit10ofFIG. 1, the bone saw bit10has a part spherical body11. The part spherical body11is shaped efficiently to allow the cutting end12to engage and cut through a bone at sufficiently steep angle without the bone engaging a substantial portion of the part spherical body11or the shank14as severance of the bone is completed. In other embodiments, the part spherical body11may be contained in less than one hemisphere, in this regard it is a partial hemispherical body. Moreover, the part spherical body11may have a shape substantially formed as a spherical triangle (seeFIG. 6A), wherein the cutting end12is one of the three arcs forming the spherical triangle.

Turning again toFIG. 1, the cutting end12comprises a plurality of cutting teeth26. Each cutting tooth26includes oppositely opposed cutting surfaces27,28arranged within a single row. It is to be recognized that other cutting teeth are contemplated within the scope of this invention for example, and without limitation, jagged serration, hyper- or hypo-extending surface edges and multiple rows of cutting teeth. The opposed cutting surfaces27,28of the plurality of cutting teeth are each symmetrically spaced and aligned.

Optionally, as shown inFIG. 17(not to scale), the plurality of cutting teeth26may also comprise a plurality of inner cutting teeth400and a plurality of outer cutting teeth402, where the inner cutting teeth400each have an inner tooth surface401, the inner tooth surface401having the radius R of the inner surface20of the part spherical body11, and the outer cutting teeth402each having an outer tooth surface403, the outer tooth surface403congruent with the outer surface18of the part spherical body10.

FIG. 3shows a schematic representation, circumscribed about a sphere, illustrating a bone saw bit10in accordance with another embodiment of the invention. Reference may also be made toFIG. 4. The part spherical body11includes an outer surface18, an inner surface20, a cutting end12extending between the outer surface18and the inner surface20, an axis16extending from the outer surface18through the inner surface20, and an origin O located on the axis16. The cutting end12extends as an arc BDC lying substantially within (e.g., disposed substantially within) a plane24intersecting the origin O. An integral shank14extends outwardly from the outer surface18of the part spherical body10and is substantially aligned with and extends parallel to the axis16.

The part spherical body11has a shape substantially formed as a spherical triangle wherein the cutting end12is one of the three arcs forming the spherical triangle and the other two arcs are represented by numerals30and32. As shown more specifically byFIG. 4, the spherical triangle is formed by a first arc defined by the cutting end12which extends between vertex B and vertex C. A second arc30extends from vertex B to vertex A. The third arc32extends from vertex A to vertex C. A cord M extends from the vertex A to the vertex B. Similarly, a cord P extends from vertex A to vertex C. In the preferred construction of the invention, cord M is dimensionally equivalent to cord P. A cord T extends from vertex B to vertex C. As further shown inFIG. 3, vertices B and C are each positioned at a radial distance SR from the origin O. A point D is defined as being positioned midway on the arc12extending between vertices B and C. The cord T is shown as being formed of two elements, each element being designated BR. The elements BR are dimensionally equivalent to one another. An arc m extends from the vertex A to the point D as shown inFIG. 4. A radius SR extends from the origin O to the point D. The intersection of the radius Z, which extends from the origin O to the vertex D, with the cord T defines a point G. Line Y extends from the vertex A to the point G as shown. Similarly, the line X extends from the origin O to the point G. The inner surface20is positioned at a radial distance SR from the origin O. Similarly arc BDC which defines the cutting end of the saw bit, is also positioned substantially at a radial distance defined by the radius SR.

As shown inFIG. 5, the inner surface20of the shank14is also disposed at a radial distance corresponding to the length of the same radius SR, which, in addition to the benefits provided herein, allows the bone saw bit10to make an efficient cut of a bone by taking advantage of the entire part spherical body11. As further illustrated inFIG. 5, two reference points E and H are defined at the intersection of opposing edges of the shank14and the outer surface20of the bit11.

Advantageously as shown inFIG. 3, the alternative embodiment of the bone saw bit11, designated bone saw bit11A is designed for continuous cutting of a bone, when the bone is equal to or smaller in diameter than the length of the cord T or 2BR, i.e., the length of a cord between points B and C. In this particular embodiment, the length of cord T is dimensionally less than 2R where R is the length of the radius SR for the inner surface18of the bit11A as previously described. For the illustrated bit11A,FIGS. 3 and 3Aillustrate that the cutting end12, defined along the arc BDC, lies in a plane24which intersects the origin O preferentially and substantially at an angle θ from the axis16. InFIG. 3Athe angle θ is an angle having a degree measure between 35 degrees and 145 degrees as measured from the axis16. In another aspect of the invention, the angle θ may be between about 60 degrees and about 120 degrees. In yet another aspect of the invention the angle θ may be about 90 degrees.

FIGS. 6A-Dshow various views of a pictorial representation of a bone saw bit100in accordance with yet another embodiment of the invention. The bone saw bit100has a part spherical body11that includes a cutting end12, an outer surface18, an inner surface20, an axis16extending from the outer surface18through the inner surface20, and an origin O on the axis. The cutting end12extends between the outer surface18and the inner surface20of the part spherical body11and substantially lies within a plane24intersecting the axis16. The cutting end forms an arc BDC. The plane24is aligned approximately 120 degrees to the axis16and intersects the origin O in this embodiment allowing the cutting end12to efficiently cut or surgically sever a bone into two pieces having convex and concave domes, respectively.

Optionally, the plane24containing the cutting end12may intersect the axis16at a location positioned between the origin O and the point A. Where the plane24intersects the axis16at a location between the origin O and the point A, the radius of the cutting end12will have an effective radius equal to the radius SR of the inner surface20of the part spherical body11allowing for the same “dome” osteotomy to be performed even though the theoretical radius is potentially smaller than the actual radius SR of the inner surface. To obtain the effective radius, a surgeon, for example, may have to rotate the saw blade bit100about a greater circle while completing an operation (to be described below). Conventional saw blades can not complete this type of “dome” osteotomy because the cutting end resides in a plane that is below the origin which will cause, as described above, the blade to become wedge between the pieces of a bone being severed or cause damage thereto during severance.

Optionally, plane24containing the cutting end12of the bone saw bit100that intersects the axis between the origin O and the inner surface20and may lie substantially between 35 degrees and 135 degrees from the axis16. While the plane24, in this embodiment of the invention, may lie at angles greater than 135 degrees, it is expected that this to may cause undesirable binding of the bone saw bit100between the bone pieces being cut as described above. The plane24may lie with respect to the axis16to a lesser extent than the 35 degrees described herein without consequence, but becomes less effective for cutting bones.

In still other embodiments of the invention, a plane containing the cutting end and intersecting the axis between the origin and the inner surface may be substantially perpendicular to the axis in order to achieve greater cutting surface area of a bone while making a dome osteotomy with cutting radius SR.

As with the other embodiments of the invention, the cutting end12may also comprise a plurality of cutting teeth. The cutting end12may include other cutting structures suitable for cutting material, such as bone, as would be recognized by a person having ordinary skill in the art.

FIG. 7shows a graphical view200of various dome heights211,213,215,217achieved in a bone202using various sized bone saw bits210,212,214,216, respectively, in accordance with embodiments of the invention.

Each of the bone saw bits210,212,214,216comprise a part spherical body11having an outer surface18, an inner surface20, a cutting end12extending as an arc “BDC” between the outer surface18and the inner surface20, an axis16extending from the outer surface18through the inner surface20, and an origin O on the axis16, the inner surface20and the arc BDC have a radius R or SR extending from the origin O as described inFIGS. 1-6.

The bone202includes surgically severed bone portions203and204. The bone portion203is a concave dome and the bone portion204is a convex dome. Each of the dome heights211,213,215,217achieved by using various sized bone saw bits210,212,214,216, respectively, are shown between the outer edges205,206of the bone, but include for illustrative purpose the entire circular envelope represented by the cutting radius SR.

The dome height211is achieved by using the bone saw bit210having radius SR that is exactly one half the width of the bone202and a cutting end12that has an arc BDC. In order to sever the bone202into portions203,204, the bone saw bit210, while engaging the bone, is rotated about cutting center point220. The center point220is representative of the center point about which the bone saw bit may be rotated while cutting a bone and may remain stationary or transition with respect to the bone depending upon the cut being made. In this respect, the cutting center point220generally denotes a floating point about which the tool may be rotated by a surgeon. The dome height211is the theoretically largest dome height obtainable and requires precise control by a surgeon in order to accomplish the osteotomy, particularly considering that the cutting end may interfere with opposing bone portions and due to interference from the hub it may be difficult to accomplish.

The dome heights213,215,217, obtained by using larger more forgiving bone saw bits212,214,216, range between approximately 75% and 25% of maximum dome height211. However, greater or lesser dome height may be obtained by using other sized bone saw bits. Each of the bone saw bits212,214,216have a cutting end12with an associated cord BDC substantially equal or greater than the diameter of the bone. As is shown in the illustration ofFIG. 7, bone saw bits212,214,216are each rotated about center points of rotation222,224,226, respectively, in order to complete severance of the bone202.

It is to be recognized that the greater the dome height, such as dome heights211,213,215,217, the greater the surface or contact area for bone portions203and204when repositioned in any of the three degrees of freedom mentioned above. Also, “true dome” osteotomies described herein provide for the optimal contact or surface area for each bone portion203,204for any given dome height.

Generally in the embodiments of the invention, the thickness of the part spherical body11between the inner surface20and the outer surface18is mostly constant. However, it is recognized that the part spherical body11may include corrugations, ribs, cutouts or low friction coatings on or between either of the inner surface20and the outer surface18in order to enhance the cutting efficiency of the bone saw bit or to minimize heat generation thereby minimizing necrosis of the bone. Corrugations, cutouts and ribs may act as channels for allowing a cooling fluid to be directed towards the cutting end of the bone saw bit during a surgery to further facilitate the minimization of heat generation. Another aspect of the bone saw bit is it will be self-guiding and self-centering while cutting bone, because of its substantially spherical design.

In still other embodiments of the invention, the bone saw bit may include a balance member coupled to a portion of the part spherical body, such as the hub, and or the shank in order to balance the bone saw bit about the axis of oscillatory motion. By providing a balance member, the vibration is minimized during a cutting proceeding that facilitates manipulation and control of the bone saw bit by the surgeon.

It is to be recognized that the bone saw bit10as shown inFIG. 1includes the cutting end12that lies substantially in a plane that intersects the origin O. In this regard, the cutting end12lies substantially about a great circle of the bone saw bit10, which advantageously allows the bone saw bit10to be used with an oscillating saw having any magnitude of oscillatory motion consistent for use with the invention.

FIGS. 8A-Eillustrates an embodiment of the instant method of performing an osteotomy of a bone202. Initially, a bone saw bit212as described above with respect toFIG. 7is provided. The user determines the location of the spherical center or origin O of the bone saw bit. Next, the user identifies a longitudinal or central axis201of the bone202to be sectioned. A location203on the outer surface of the bone202where the cut is to be initiated is next identified. Alternatively, the apex223of the anticipated cut may be identified.

Utilizing the location of the origin O relative to the cutting end12of the bone saw bit212, i.e. the radius SR, and the location of the longitudinal axis201, the user calculates the location of a center of rotation222for the bone saw bit212for the anticipated sectioning. The center of rotation is typically located at a radial distance W from either the location203or the apex223. Radial distance W typically corresponds to the length of the radius SR of the bone saw bit. In many instances, the center of rotation222will be located on the longitudinal axis201of the bone202. In the embodiment of the method shown inFIGS. 8A-E, the center of rotation222is positioned on the longitudinal axis201at a location207wherein the radial distance W is substantially identical to the length of the radius SR of the saw bit212.

Having identified the point207and determined the orientation of the center of rotation222, the bone saw bit212is then positioned on the bone202in an orientation and angle β predetermined by the surgeon such that the bone saw bit212may be rotated as shown by arrow230to produce dome height213. In one embodiment of the invention as illustrated inFIG. 8A, the origin O of the bone saw bit is positioned at the point207.

In this embodiment the center of rotation222may be determined by utilizing the methodology for determining the location of a center of rotation of angulation as described in Principles of Deformity Correction, New York: Springer, 2005, by Dror Paley and Contributor J. E. Herzenberg., the text of which is hereby incorporated by reference. Specific reference is made to pages 61 et seq. of the Paley book wherein a method of determining a CORA (center of rotation of angulation) for a deformed bone is described. The Paley methodology utilizes a visualization of a deformed bone which has been divided into segments. The segments are visualized as being angulated to an orientation which will meet the objectives of the surgeon user. Each of the segments defines a respective longitudinal axis, i.e. respectively a proximal longitudinal axis for one segment and a distal longitudinal axis for the other segment. In the visualized orientation, the pair of proximal and distal longitudinal axes intersect and form an angle. The point at which the proximal and distal axis lines intersect is called the center of rotation of angulation (CORA). In one embodiment of the method of the instant invention, the Paley method for determining the CORA of a subject bone is utilized as a means of locating a CORA which is then used as the center of rotation222for purposes of the instant method, i.e. once the location of the CORA is identified utilizing the method of Paley the location of the CORA may be used for purposes of the instant method by either locating the center of rotation point222at the same location as the CORA or alternatively, the CORA may be utilized to otherwise identify a location203or233at which the sectioning should preferably be performed. Should the user adopt the latter approach, the above described methodology may be then employed to determine the location of the center of rotation222.

The driver240, an oscillating or reciprocating saw of a type conventionally associated with surgical saws, is then energized to actuate, i.e. oscillate the cutting end of the bone saw bit212. The bone saw bit212having been positioned at the initial angle β determined by the surgeon relative to the center of rotation222such that the origin O of the bit is positioned on or substantially on the point of intersection of the center of rotation222and the longitudinal axis201engages the bone202at point203and thereafter is rotated about the center of rotation222to cut a path (represented by the dome height213) by pitching or rotating the driver forward and downward.

In the embodiment of the instant method illustrated inFIGS. 8A-E, the center of rotation222remains spatially fixed throughout the procedure.

Advantageously, the surgeon will control the orientation of the saw, while the bone saw bit212will guide or self-guide and self center itself while making the dome shaped cut between opposing portions203,204of the bone. The procedure is completed when the bone saw bit212cuts through the bone202. In this osteotomy example, bone saw bit212is properly sized allowing the positional angle β at the beginning of the cut to be approximately 35 to 45 degrees with respect to the longitudinal axis201of the bone202, which allows the bone saw bit212to be rotated through about 135 to 145 degrees in order to finish cutting the bone202.

In order to balance the need for efficient cutting, the need to sever the bone in a single pass and the need to provide three dimensional adjustment of the bone pieces, the cutting plane may intersect the origin O at a greater or lesser angle than the 120 degrees illustrated inFIG. 8C.

FIG. 9shows two bone portions303,304of a bone302having “true dome” or spherical osteotomy surface having been surgically severed with a saw blade bit. Bone portion303includes a concave surface305defined by the radius J extending from an origin L that corresponds to center of rotation222and the axis201of the bone303. Bone portion304includes a convex surface306defined by the radius G extending from an origin K that corresponds to central point222and the longitudinal axis201of the bone304. It is to be recognized that the origins L and K may extend from a location other than the longitudinal axis201of the bone or the center of rotation222depending upon how the surgeon makes the cut through the bone with a bone saw bit. The bone302was severed into bone portions303,304with a bone saw bit in accordance with embodiments of the invention as the surgeon transitioned the bone saw bit about point222as described above.

Advantageously, the concave surface305substantially mates with the convex surface306allowing the bone portions303,304to be repositioned together about any of three degrees of freedom, because the concave surface305and the convex surface306are both “true dome” or spherical osteotomies that substantially mate. Furthermore, the surgeon may perform the osteotomy by positioning the central point222, or allowing it to transition, where it is convenient to sever the bone302, because the “true dome” or spherical osteotomy result is obtained anywhere about the bone, particularly their central axis, when the novel bone saw bit is used.

FIGS. 10-12illustrate an alternative embodiment of the invention wherein the thickness of the bit11is altered from the bit constructions described above. As shown inFIG. 10a saw bit of the constructions heretofore described has a constant thickness307over its entire length. Stated otherwise, the distance between the inner surface20and the outer surface18remains constant over the body of the bit. The bit shown inFIG. 11alters this construction in that the thickness310of the bit proximate the opposing ends312and323of the bit11is dimensionally larger than the thickness311of the bit proximate the central region of the bit. As shown, in this embodiment, the inner surface20is configured as a smooth curved surface. In this construction, the radius of curvature of a location315on the inner surface20typically has a smaller radius of curvature than a corresponding location323on the outer surface18positioned along a radial line321.

The bit11ofFIG. 11may be utilized in the instant invention to produce a bone sectioning of the configuration shown inFIG. 12. As shown a bone has been sectioned into two elements313and314, utilizing the bit ofFIG. 12. The upper surface configuration of the element313exhibits a surface which does not have a constant radius of curvature over its entire surface. Indeed as can be noticed, the edges316and317of the upper region of the bone313have a much smaller radius of curvature than their counterpart surfaces on the sectioned portion of bone314. As shown inFIG. 12, the radius RR from the origin O or point of rotation222is dimensionally larger than either of the radii RT which extend from the origin O to either of the edges of the upper sectioned end of the bone313. This particular configuration may prove useful in certain circumstances, notably in acute angular correction where the friction between bone sections may be high enough to prevent proper positioning.

FIGS. 13 and 14illustrate a further embodiment of the invention wherein the inner surface20of the bit11is configured to define a recess319. In the illustrated embodiment of the bit, the thickness of the bit11remains constant over the length of the bit with exception of the region defining the recess. In use the bit ofFIG. 13will produce a section configuration corresponding toFIG. 14in which the bone element320will define an upstanding ridge317and corresponding voids326on either side of the ridge which separate the two bone elements from one another.

In acute angular correction where the friction between bone sections is high enough to prevent proper positioning.

FIGS. 15 and 16illustrate a structure for interconnecting the bit11of the invention with an actuating device (not shown). The end of the bit11is shown coupled with a connection structure which includes a threaded shaft334adapted for coupling with an actuating device of the type conventionally used with surgical saws. A housing331defining a void therein configured to receive a threaded element332is positioned on the bit11. Element332defines a cavity333therein dimensioned to receive a connection nut secured to the bit11.FIG. 16is a top view of the element332.

While embodiments of the invention have been described generally with respect to part hemispherical body, a spherical body and a sphere, it is to be recognized that a prolate or oblate spheroid shape may also be used with the teaching disclosed herein.

The bone saw bit in accordance with the embodiments described above may be used to make “true dome” or dome-shaped cuts in solid materials, but are preferentially directed toward making dome-shaped cuts in bones, such as dome osteotomies. The bone saw bit has many applicable uses including osteotomy procedures in both veterinary and human medicine/surgery.

The saw blade bit may be provided for disposable or reusable uses and may be available in sterile or non-sterile conditions. The saw blade bit described herein is not limited to the specific applications disclosed, but may be utilized for many types of surgical procedures in humans and animals requiring the severing, cutting or removing sections of anatomical structures, including but not limited to: general long bone osteotomies for correction of angular deformities, resection of the diseased bone area or section between two joints of the same bone, osteotomy of bones with malunions after improper healing of fractures, osteotomy for proximal humeral deformity correction, distal humeral osteotomy for correction of cubitus varus, osteotomy of distal humerus for correction of medial compartmental disease of the elbow, osteotomy of the distal radius for correction of premature physeal closure of the ulna and/or radius, periacetabular osteotomy for the correction of hip dysplasia, proximal femural osteotomy for correction of hip dysplasia and femural head and neck angle correction, distal femural and supracondylar osteotomy, proximal tibial and high tibial osteotomy for unicompartmental disease correction and valgus varus correction, calcaneal osteotomy, proximal metatarsal osteotomy, Tibial Plateau Leveling Osteotomy (TPLO) etc. The saw blade bit may be of any size and preferably constructed of stainless steel.

Generally, the invention provides a saw blade bit, and method therewith, that provides for cutting true dome shape surfaces, is self-guiding, aides healing, minimizes damage to surrounding soft tissue by self-centering, as well as provides for maximum contact of the substantially mating surfaces, optimal dome height, enhanced stability and adjustability.

The saw blade bit described above may come in different sizes and attachment configurations for use with different bone sizes and surgical procedures. The saw blade bit may be assembled into kits. The kits may further include tools associated with the blades, such as various handles, screws, clamps, locking mechanisms, fastening devices, measuring devices, brackets, power tools, etc.

Also, the saw blade bit may be used to make dome shaped or substantially spherical cuts through solid substance.

From the foregoing the invention provides a novel device and method to perform “true dome” or spherical osteotomies. The invention attains several advantages, some of which are summarized as follows: it is an advantage of the invention to provide a device and method for making a dome shaped cut through a solid substance resulting in two substantially congruent mating surfaces, and more specifically a device and method to perform true dome osteotomies as opposed to conventional barrel-vault osteotomies for the purpose of correcting malalignment and malorientation of bones in humans and animals. Another advantage of the invention is to provide a dome saw blade and method to perform improved corrective osteotomies that produce two bone sections with congruent dome shaped mating surfaces that may be realigned and fixation applied as understood by a person having skill in the art, and which may provide for optimal dome height, increased stability of the rejoined bone sections, minimized bone loss, decreased chance of damage to bone tissue and the surrounding soft tissue, rapid and structurally effective mending or knitting of the bone, faster and more reliable healing, as well as the orthopedic surgeon's ability to make intraoperative adjustments to attain the desired correction, including correcting for large rotational deformities.

Changes may be made to the embodiments described in this disclosure without departing from the broad inventive concepts they illustrate. Accordingly, this invention is not limited to the particular embodiments disclosed, but is intended to cover all modifications that are within the scope of the invention as defined by the appended claims.