Abstract:
A double-bladed cutting device providing a practical method for obtaining costal cartilage specimens in both an operating room and research setting. The device reduces the skill and time required to fashion cartilage slices, while increasing the uniformity of the cut specimens. Furthermore, via an adjustable guide, slices can be obtained precisely from the central core of the rib. Although specimen lengths up to 4 cm are preferred, longer lengths can be attained without modification of the device. The cartilage specimen may be held in place within the device via means of compression or tension.

Description:
STATEMENT OF GOVERNMENT SUPPORT 
     This invention was made with government support under grant number DR090349 awarded by Department of Defense Deployment Related Medical Research Program and grant number 1R21DE019026 awarded by the National Institute of Dental and Craniofacial Research. The government has certain rights in the invention. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to the field of medical tools, specifically to a cutting device used to obtain uniformly thick slices of cartilage from a costal (rib) cartilage sample. 
     2. Description of the Prior Art 
     Costal cartilage is becoming increasingly popular as a graft source for facial reconstruction. However, carving methods have not changed in decades, and continue to primarily rely upon detailed maneuvers with a scalpel. There are currently very few mechanical devices for shaping costal cartilage and the accuracy and precision of manual methods leave much to be desired. 
     Providing for a relatively abundant supply of cartilage, the costal margin is the only practical option for autogenous cartilage grafts when auricular and septal cartilage are depleted or if significant cartilage is required for extensive framework reconstruction. However, grafts harvested from peripheral regions of costal cartilage have the potential disadvantage of warping after graft placement. This undesirable effect is minimized and theoretically eliminated by obtaining balanced cross-sections from the central core of the rib. Such considerations demonstrate that the harvesting technique critically affects the shape dynamics and outcome of costal cartilage grafts, particularly in applications such as reconstructive rhinoplasty. 
     Techniques for carving cartilage have had modest progress over the past several decades. In the operating room, the scalpel remains the preferred instrument of choice. However, this method is hindered by imprecise and tune-consuming maneuvers. Obtaining flat grafts of uniform thickness using a scalpel requires skill and expertise, especially for thinner slices such as spreader grafts used for rhinoplasty. The ability to harvest uniform cartilage specimens is important because these specimens have a wide range of applications in nasal reconstruction. 
     Several cartilage cutting devices have been described or alluded to in the literature. Generally, these devices adhere to a common design of two parallel blades that are separated by a specific distance using a spacer at both ends. The piece of rib is first cut to a length that is no greater than the distance between the spacers. Then, the double-bladed device is pushed through the rib segment, producing a slice having approximately the same thickness as the spacer. Specifically, one device employs a guillotine-type apparatus fashioned from a traditional paper cutter lever utilizing two parallel blades. These blades are then swung down to section a rib segment. Other iterations include a cartilage cutting guillotine using razor blades in conjunction with securing the rib with gentle compression in a vise mechanism. Still other examples have adapted the guillotine concept by using four parallel blades in order to obtain a central slice and two peripheral slices. Although these devices offer a simple and rapid cutting approach alternative to the traditional scalpel, the accuracy of these devices is suspect at best. 
     What is needed is a simple device and method for cutting costal cartilage into well defined, uniformly thick user defined segments that are suitable for various delicate reconstructive surgeries. 
     BRIEF SUMMARY OF THE INVENTION 
     The current device is a cutting device that creates costal cartilage sections of a user-defined and highly uniform thickness. We describe our design effort and systematic examination of cutting mechanisms and designs, and then describe our prototype device and its performance capabilities. 
     A double-bladed cutting device providing a practical method for obtaining costal cartilage specimens in both an operating room and research setting is disclosed. The device reduces the skill and time required to fashion cartilage slices, while increasing the uniformity of the cut specimens. Furthermore, via an adjustable guide, slices can be obtained precisely from the central core of the rib. Although specimen lengths up to 4 cm are preferred, longer lengths can be attained without modification of the device. The cartilage specimen may be held in place within the device via means of compression or tension. 
     While the apparatus and method has or will be described for the sake of grammatical fluidity with functional explanations, it is to be expressly understood that the claims, unless expressly formulated under 35 USC 112, are not to be construed as necessarily limited in any way by the construction of “means” or “steps” limitations, but are to be accorded the full scope of the meaning and equivalents of the definition provided by the claims under the judicial doctrine of equivalents, and in the case where the claims are expressly formulated under 35 USC 112 are to be accorded full statutory equivalents under 35 USC 112. The invention can be better visualized by turning now to the following drawings wherein like elements are referenced by like numerals. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a perspective view of the cutting jig portion of the current device. 
         FIG. 1B  is top view of the cutting jig seen in  FIG. 1A . 
         FIG. 2  is a perspective view of the specimen assembly portion of the current device, the slide member and base of the specimen assembly being separated. 
         FIG. 3  is a top down perspective view of the specimen assembly, the slide member being coupled to the base. 
         FIG. 4  is an exploded view of the cutting jig seen in  FIG. 1A  and the specimen assembly seen in  FIG. 3 . 
         FIG. 5  is a side view of the specimen assembly with a cartilage specimen inserted between a slide post of the slide member and a fixed post of the base. 
         FIG. 6A  is side view of the device after the slide member has been tightened to hold the specimen In a compressed grip. The cutting jig is also seen being prepared for insertion into the guide. 
         FIG. 6B  is a side view of the device seen in  FIG. 6A  after the cutting jig has been inserted into the guide and placed just over the specimen. 
         FIG. 6C  is a side view of the device seen in  FIG. 6B  after the cutting jig has been pushed downward into the cartilage specimen, the double blades of the cutting jig creating a graft from the specimen. 
         FIG. 7A  is side view of an alternative embodiment of the current device in which a cartilage specimen is inserted between a slide post of the slide member and a fixed post of the base. 
         FIG. 7B  is a side view of the alternative embodiment seen in  FIG. 7A  in which a vertical spacer has been inserted in between the specimen  66  and the fixed post of the base. 
         FIG. 7C  is a side view of the alternative embodiment seen in  FIG. 7B  in which a plurality of sutures have been threaded through the specimen and then tied to the fixed post of the base. 
         FIG. 7D  is a side view of the alternative embodiment seen in  FIG. 7C  in which the vertical spacer has been removed and an additional plurality of sutures have been threaded through the specimen and then tied to the slide post of the slide member. 
         FIG. 8  is a top down view of a graft that has been cut from the cartilage specimen by the cutting jig. 
         FIG. 9  is a top down view of the cartilage graft after being removed from the remainder of the cartilage specimen seen in  FIG. 8 . 
     
    
    
     The invention and its various embodiments can now be better understood by turning to the following detailed description of the preferred embodiments which are presented as illustrated examples of the invention defined in the claims. It is expressly understood that the invention as defined by the claims may be broader than the illustrated embodiments described below. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The current device comprises three main components, a cutting jig  12  seen in  FIGS. 1A and 1B , a slide member  14  and a base  16  seen in  FIGS. 2 and 3 . When the slide member  14  and base  16  are coupled together as seen in  FIG. 3  and as further described below, a specimen assembly  10  is formed. 
     Turning now to the cutting jig  12  and  FIGS. 1A and 1B , it can be seen that the cutting jig  12  comprises two substantially U-shaped halves, namely a top half  18  and a bottom half  20 . The bottom half  20  further comprises a substantially “T” shaped jig key  30  disposed along one of its outer edges. The jig key  30  helps to guide the cutting jig  12  through the specimen assembly  10  as is further detailed below. Disposed between the top half  18  and the bottom half  20  is a pair of parallel blades  22  separated by a pair of identical aluminum spacers  24 . The halves  18 ,  20  effectively sandwich the pair of blades  22  and spacers  24  there between and due to their substantial U-shape, define an aperture  26  in the center of the cutting jig  12 . The spacers  24  maintain the blades  22  a fixed distance apart and define an aperture or cutting segment  28  which is used to cut a cartilage specimen. The cutting jig  12  is held together with the blades  22  in a locked position with the aid of a pair of jig bolts  32  inserted through both the top half  18  and bottom half  20 . A corresponding pair of washers  36  and a pair of knurled nuts  34  lock the halves  18 ,  20  into position and prevent the blades  22  and spacers  24  from any extraneous movement. 
     The size and shape of the cutting segment  28  and thus the ultimate size and shape of the cut cartilage specimen may be changed or altered by the user by exchanging the spacers  24  and the blades  22  seen in  FIGS. 1A and 1B  for alternative blades or spacers of a differing size according to preference. 
     For example, the cut cartilage specimen may be altered by the bevel characteristic of the blades  22 . The bevel of a blade considerably affects uniformity of the resulting cut cartilage slice. Thousands of blades for commercial and industrial purposes are available from innumerable vendors and are well known in the art. In general, most blades are typically beveled on both sides of the cutting edge forming a “V” shape. This provides a thin, sharp edge for cutting. The concern of using a bi-bevel design in a double-bladed cutting device is that the distance between the beveled cutting tips of the blades is greater than the distance between the bodies of the blades themselves. Therefore, as a slice is being cut, the thickness of the slice is forced through the smaller region between the bodies of the blades and causes the blades to diverge. This leads to an even greater thickness of cartilage to be cut, and the cycle self perpetuates, leading to the creation of a wedge shaped specimen. Correspondingly, thicker blades would cause increased wedging due to a more prominent bevel and thus an even greater distance between the tips of the blades as compared to the distance between the bodies of the blades. Therefore, thinner blades will reduce this effect, but will not entirely eliminate the wedging effect. Furthermore, extremely thin blades will introduce the potential of blade flexure unless expensive stainless steel alloys or exotic aerospace industry materials are employed. The preferred embodiment is to use single beveled blades with the bevel facing outwards, which eliminates the source of wedging. 
     Additionally, increasing blade length results in flexure during guillotine sectioning and significantly reduces specimen thickness uniformity. To minimize blade flexure, stiffer and thicker blades can be used, but at a higher cost. To circumvent vent the necessity of using longer blades, the cartilage specimen can simply be cut through its long axis instead of being cut longitudinally through its short axis. This not only minimizes the blade length, but also allows any arbitrary length of cartilage to be cut using this reduced blade length. 
     Turn now to the slide member  14  and base  16  seen in  FIG. 3 . The slide member  14  comprises of a slide key  38  disposed along its bottom surface. Like the jig key  30 , the slide key  38  comprises a substantially “T” shaped cross section. Disposed on the top surface of the slide member  14  is a slide post  40  which remains fixed relative to the rest of the slide member  14 . 
     The base  16  in turn comprises a slidable or adjustable guide  48  which is anchored to a substrate  54  via a plurality of guide bolts  52 . The guide  48  comprises a vertical portion  62  and a horizontal portion  64 . The guide bolts  52  at first hold the guide  48  to the substrate  54  but do not tightly bind the guide  48  to it, leaving the guide  48  free to slide about a guide track  58  defined within the horizontal portion  64  as best seen in  FIG. 3 . The vertical portion  62  of the guide  48  comprises a substantially “T” shaped jig aperture  50  defined throughout its length. Disposed next to the guide  48  and coupled to the substrate  54  is a fixed post  42 . The substrate  54  further comprises a post track  56  that is defined along its longitudinal axis. Like the jig aperture  50 , the post track  56  comprises a substantially “T” shaped cross section sized and shaped to fit the slide key  38 . Within the post track  56  is a gap  60  which is defined into the substrate  54  at a perpendicular orientation to that of the post track  56 . 
     To couple the slide member  14  to the base  16  and thus form the completed specimen assembly  10  seen in  FIG. 3 , the slide key  38  is first inserted into the post track  56  and then slid distally. The entirety of the slide member  14  is slid past the gap  60  and a clamping bar  44  is then inserted into the gap  60  blocking any movement of the slide member  14  back in the proximal direction. A post bolt  46  is then inserted into the post track  56  and threaded through a hole defined in the clamping bar  44  thereby providing a means for the slide member  14  to be tightened against a cartilage specimen as further detailed below. 
     With the specimen assembly  10  fully assembled, a cartilage specimen or sample  66  is placed on the substrate  54  between the fixed post  42  and the slide post  40  in the upright position as seen in  FIG. 5 . While it is seen in  FIG. 5  that the cartilage specimen  66  is substantially cylindrical, other shapes or sizes of cartilage may be used by one skilled in the art without departing from the original spirit and scope of the invention. Furthermore, it is to be expressly understood that materials or substances other than human costal cartilage may be cut using the current invention and that what is described herein is for illustrative purposes only. 
     After sliding member  14  placement, the post bolt  46  is then rotated against the sliding member  14 , pushing it distally through the post track  56 . The post bolt  46  is continually manipulated until the slide post  40  is brought up against the cartilage specimen  66  and presses it against the fixed post  42 , thus trapping the cartilage specimen  66  in a vice-like hold within the specimen assembly  10  as best seen in  FIG. 6A . Stabilization of the cartilage specimen  66  during cutting is important to prevent specimen movement, facilitate user safety, and to provide proper positioning so that precise cuts can be made at specific regions. Ideally, the method of stabilization would also straighten curved pieces of the specimen  66 , so that the blades  22  can precisely traverse the center of the specimen  66  with simple downward force. Securing the cartilage specimen  66  using a clamp is a simple option that can provide stabilization. 
     The cutting jig  12  is then brought in over the top of the cartilage specimen  66  by inserting the jig key  30  into the jig aperture  50  of the guide  48 . The cutting jig  12  is then slid down towards the cartilage specimen  66  until surface contact is made between the cartilage specimen  66  and the blades  22  as seen in  FIG. 6B . The tops of the slide post  40  and fixed post  42  penetrate the aperture  26  defined within the cutting jig  12  so as to give the blades  22  easy and continual access to the cartilage specimen  66 . The user may adjust the specific location of the blades  22  with respect to the cartilage specimen  66  by sliding the guide  48  and thus the cutting jig  12  distally and proximally through the guide track  58 . When the desired cutting position has been obtained, the user fixes the guide  48  into a stationary position by tightening of the guide bolts  52  as is known in the art. 
     With the cartilage specimen  66  and guide  48  firmly locked down into place, a downward pressure is exerted on the cutting jig  12 , pressing the blades  22  into the cartilage specimen  66 . The cutting jig  12  is pressed downward with the jig key  30  within the jig aperture  50  of the guide  48  until contact is made with the substrate  54  as seen hi  FIG. 6C . The cutting jig  12  is then pulled upward in the opposing direction until the jig key  30  is free of the guide  48 . The post bolt  46  is then loosened allowing the slide member  14  to be slid back proximally and the cartilage specimen  66  removed from the base  16 . 
     The resultant cut made by the cutting jig  12  on the cartilage specimen  66  can be seen in  FIG. 8 . The double bladed design of the cutting jig  12  splits the cartilage specimen  66 , producing a user-defined cartilage graft  68  suitable for a number medical procedures including but not limited to rhinoplasty. The cartilage graft  68  may be removed from the remainder of the cartilage specimen  66  as seen in  FIG. 9  by a simple razor, knife, or other means known in the art. 
     An alternative means to secure the cartilage specimen  66  is through tension and can be seen in  FIGS. 7A-7D . As seen in  FIG. 7A , the cartilage specimen  66  is first placed between the fixed post  42  and the slide post  40  as described above. A vertical spacer  70  is then inserted between the fixed post  42  and the specimen  66  in order to provide a snug or tight fit as seen in  FIG. 7B . A plurality of sutures  72  are then inserted through the specimen  66  using a common needle and thread or other means well known in the art. The free ends of the sutures  72  are then tied around the fixed post  42 , thereby fixing the specimen  66  into position on at least one side as best seen in  FIG. 7C . After the sutures  72  are tied to the fixed post  42 , the vertical spacer  70  is removed. As seen  FIG. 70 , an additional plurality of sutures  72  are threaded through the opposing side of the specimen  66 . The free ends of these sutures  72  are tied around the slide post  40 , thereby holding the specimen  66  in a fixed vertical position. Securing the specimen  66  to the posts  40 ,  42  with more sutures  72  will increase the stability of the specimen  66  during cutting. This minimizes the chance of error and prevents listing of the blades  22  away from the core of the cartilage specimen  66 . Therefore in critical settings, it is preferred to use at least one suture  72  per 1 cm of cartilage specimen  66  length per post  40 ,  42 . After the cartilage specimen  66  has been properly secured to the posts  40 ,  42 , the cutting jig  12  may then be used to cut the graft  68  in the same manner as shown and described above. After the cutting jig  12  is removed, the specimen  66  is removed from the specimen assembly  10  by severing the sutures  72 . 
     Many alterations and modifications may be made by those having ordinary skill in the art without departing from the spirit and scope of the invention. Therefore, it must be understood that the illustrated embodiment has been set forth only for the purposes of example and that it should not be taken as limiting the invention as defined by the following invention and its various embodiments. 
     Therefore, it must be understood that the illustrated embodiment has been set forth only for the purposes of example and that it should not be taken as limiting the invention as defined by the following claims. For example, notwithstanding the fact that the elements of a claim are set forth below in a certain combination, it must be expressly understood that the invention includes other combinations of fewer, more or different elements, which are disclosed in above even when not initially claimed in such combinations. A teaching that two elements are combined in a claimed combination is further to be understood as also allowing for a claimed combination in which the two elements are not combined with each other, but may be used alone or combined in other combinations. The excision of any disclosed element of the invention is explicitly contemplated as within the scope of the invention. 
     The words used in this specification to describe the invention and its various embodiments are to be understood not only in the sense of their commonly defined meanings, but to include by special definition in this specification structure, material or acts beyond the scope of the commonly defined meanings. Thus if an element can be understood in the context of this specification as including more than one meaning, then its use in a claim must be understood as being generic to all possible meanings supported by the specification and by the word itself. 
     The definitions of the words or elements of the following claims are, therefore, defined in this specification to include not only the combination of elements which are literally set forth, but all equivalent structure, material or acts for performing substantially the same function in substantially the same way to obtain substantially the same result. In this sense it is therefore contemplated that an equivalent substitution of two or more elements may be made for any one of the elements in the claims below or that a single element may be substituted for two or more elements in a claim. Although elements may be described above as acting in certain combinations and even initially claimed as such, it is to be expressly understood that one or more elements from a claimed combination can in some cases be excised from the combination and that the claimed combination may be directed to a subcombination or variation of a subcombination. 
     Insubstantial changes from the claimed subject matter as viewed by a person with ordinary skill in the art, now known or later devised, are expressly contemplated as being equivalently within the scope of the claims. Therefore, obvious substitutions now or later known to one with ordinary skill in the art are defined to be within the scope of the defined elements. 
     The claims are thus to be understood to include what is specifically illustrated and described above, what is conceptionally equivalent, what can be obviously substituted and also what essentially incorporates the essential idea of the invention.