Long bone reamer

[0002] 1. Field of the Invention

[0003] The invention relates to surgical long bone reamers formed from a plurality of interlocking blades.

[0004] 2. Description of Related Art

[0005] The prior art patent literature discloses a small group of reamers and cutters for removing bone and tissue from joints that may be relevant to the state of the art. Many of those reamers are for shallow bone applications. For example, U.S. Pat. No. 4,621,637 entitled “SURGICAL DEVICE FOR REMOVING BONE AND TISSUE FROM JOINT MEMBERS” teaches a slotted, surgical device including a hemispheric housing that supports one or more cutting blades for bone and/or tissue cutting. Two and three blade embodiments are described. In both cases, the blades abut centrally of the device and interlock with the base at discrete points.

[0006] French Patent 1,031,888 describes a plurality of cutting blades which are radially disposed, equiangularly spaced atop a supporting plate and locked to the plate by fasteners. The resulting tool is used for cutting the acetabular portion of a hip prior to joint replacement.

[0007] Similarly, French Patent 1,041,311 describes a bone cavity forming tool which employs multiple blades in a hemispheric array.

[0008] Soviet Union Patent 1225-543-A entitled “BONE CUTTING TOOL FOR SURGERY” describes a cutter comprising multiple arcuate cutting elements extending from a central rod outwardly in an umbrella-like fashion.

[0009] French Patent 2,233,972 entitled “ARTIFICIAL HIP JOINT FITTING EQUIPMENT” describes another multi-blade, round headed milling cutter for acetabular applications.

[0010] U.S. Pat. No. 5,222,959 entitled “REMOVAL OF TISSUE” describes a soft tissue cutter having an oval, rather than hemispheric, shape.

[0011] U.S. Pat. No. 5,192,291 entitled “ROTATIONALLY EXPANDABLE ATHERECTOMY CUTTER ASSEMBLY” describes another soft tissue cutter in which the blades define a cylindrical, not hemispheric, structure.

[0012] U.S. Pat. No. 5,100,267 entitled “DISPOSABLE ACETABULAR REAMER CUP”describes a hemispheric, cup-shaped hip reamer. With regard to this structure, note also U.S. Pat. Nos. 5,116,165 and 5,376,092.

[0013] The following U.S. Patents describe prior art shallow bone reamers of possible interest, using multi-blade configurations, but for non-hip applications: U.S. Pat. Nos. 3,554,192; 5,122,134, 5,180,384 and 5,318,576.

[0014] In addition to shallow bone reamers, the prior art also discloses a few possibly relevant references to long bone reamers. For example, note U.S. Pat. No. 4, 473,070 entitled INTRAMEDULLARY REAMER. That device includes a circular, replaceable blade that fits onto a grooved body member. There does not appear, however, to be any suggestion of interlinking or cross over blades.

[0015] U.S. Pat. No. 314,086 entitled BUNG CUTTER is of possible interest even though it does not relate to bone surgery. That references describes a structure including a mortised disk which rotates into position and includes a plurality of longitudinally extending cutters which seat in the disk via notches or mortises F on the periphery thereof. The structure, however, appears to relate primarily to cutting a bung hole in a barrel rather than reaming a hole therethrough.

[0016] The following patents are all cited as being of general interest only and are essentially the same in that they describe a reamer head for a long bone. The blades appear to generally radiate from a central portion and do not appear to be interlinked: U.S. Pat. Nos. 3,554,192; 4,706,659; 5,122,134; and, 5,190,548.

[0017] Lastly, U.S. Pat. No. 3,633,583 entitled ORTHOPEDIC SINGLE-BLADE BONE CUTTER and U.S. Pat. No. 5,211,645 entitled DEVICE FOR GUIDING AN INTERNAL SAW FOR LONG TUBULAR BONE OSTEOTOMY are cited as being as general relevance only.

[0018] While a few long and shallow joint reamers are known in the prior art, they tend to be expensive, or hard to construct, or both. There clearly appears to be a need for a safe, easy to assemble, inexpensive and effective reamer especially for the femur or tibia. Insofar as understood, none of the prior art known to the inventor, whether taken individually or in combination, hints, teaches or suggests the novel long bone reamer disclosed herein.

[0019] Briefly described, the invention comprises a long bone reamer including a plurality of interlinking cutting blades which, when assembled, has a cutting head or tip with a cutting edge which lies in a hemispherical plane.

[0020] According to a first embodiment of the invention, the reamer comprises six blades each having a straight, long side and a curved tip. The six blades are held in position by a plurality of disks each having six blade receiving slots therein. Each blade also includes an inside surface having a plurality of tabs which, when assembled on the disks, overlap each other. The six blades actually comprise three sets of two blades each wherein the tabs of each of the three sets are offset so that they don't interfere with each other. When properly assembled, each of the tabs of the three sets of blades overlap each other and may be welded in that position.

[0021] According to a second embodiment of the invention, four blades are assembled in a boxlike structure to form the long bone reamer. Two sets of blades include a hollow aperture with inwardly facing tabs thereon, which mate with corresponding slots in the second set of blades. A rod or similar structure is located in the hollow interior of the boxlike structure for additional support.

[0022] When properly assembled, each of the two embodiments has edges which when rotated, all lie in a semi-circular surface. Moreover, when each of the embodiments is rotated, the longitudinal cutting edges of each of the blades lie in a cylindrical plane. The resulting structure is safe, easy to assemble, inexpensive and effective as a long bone reamer.

[0023] The invention may be more fully understood by reference to the following drawings.

[0024] FIG. 1 is a perspective view of a large diameter, long bone reamer according to a first embodiment of the invention.

[0025] FIG. 2 is an exploded perspective view of the large diameter, long bone reamer of FIG. 1.

[0026] FIG. 3A is a front view of the large diameter, long bone reamer of FIG. 1.

[0027] FIG. 3B is a rear view of the large diameter, long bone reamer of FIG. 1.

[0028] FIG. 3C is a side view of the large diameter, long bone reamer of FIG. 1.

[0029] FIG. 3D is a cross sectional view of the large diameter, long bone reamer of FIG. 3C as seen from perspective 3D—3D.

[0030] FIG. 4A illustrates one blade of the first set of blades of the large diameter, long bone reamer of FIG. 1.

[0031] FIG. 4B illustrates one blade of the second set of blades, of the large diameter, long bone reamer of FIG. 1.

[0032] FIG. 4C illustrates one blade of the third set of blades of the large diameter, long bone reamer of FIG. 1.

[0033] FIG. 5 is a front view of one of the supporting disks of the large diameter, long bone reamer of FIG. 1 showing the six blade receiving slots therein.

[0034] FIG. 6 is a perspective view of a small diameter, long bone reamer according to the preferred second embodiment of the invention.

[0035] FIG. 7 is an exploded view of the small diameter, long bone reamer of FIG. 6.

[0036] FIG. 8A is a front view of the small diameter, long bone reamer of FIG. 6.

[0037] FIG. 8B is a rear view of the small diameter, long bone reamer of FIG. 6

[0038] FIG. 8C is a side elevational view of the small diameter, long bone reamer of FIG. 6.

[0039] FIG. 9A is a top plan view of one of the two blades of the first set of blades included in the small diameter, long bone reamer of FIG. 6.

[0040] FIG. 9B is a top plan view of one of the two blades of the second set of blades included in the small diameter, long bone reamer of FIG. 6.

[0041] FIG. 10 illustrates the supporting and locking rod having a round cross section which goes down the center of the small diameter, long bone reamer.

[0042] FIG. 11 illustrates an alternative supporting and locking rod having a square cross section.

[0043] FIG. 12 illustrates a cylindrical reamer having cutting teeth on the leading edge thereof.

[0044] During the course of this description, like numbers will be used to identify like elements according to the different figures that illustrate the invention.

[0045] A large diameter long bone reamer 10 according a first embodiment of the invention is illustrated in FIG. 1. Each reamer 10 includes a rounded, hemispherical head 12, a plurality of blade edges 14 which lie in a cylindrical plane and a rear portion 16. Six long blades 18 are held in assembled position by disks 20. The six blades 18 are formed from three sets of two matching blades each. The first blade pair comprises blades 22aand 22b; the second blade pair comprises blades 34aand 34band the third pair of blades comprises blades 46aand 46b. Details of the blades are shown in FIGS. 4A, 4B and 4C.

[0046] FIG. 4A illustrates blade 22aof pair 22aand 22b. Blade 22bis substantially identical to 22a. Blades 22aand 22beach include a straight, longitudinal cutting edge 24aand 24b; a rounded cutting tip 26aand 26b, an inside edge 28aand 28b; tabs 30aand 30blocated on the inside edges 28aand 28b; and a rear edge 32aand 32b. Likewise, blade 34ais illustrated in FIG. 4B but is substantially identical to its mating blade 34b. Blades 34aand 34bare similar, but not identical, to blades 22a, 22b, 46aand 46b. In particular, blades 34aand 34beach include a straight, longitudinal cutting edge 36aand 36b; a rounded cutting tip 38aand 38b; an inside edge 40aand 40b; tabs 42aand 42blocated on the inside edge 40aand 40b; and a rear edge 44aand 44b. Note that tabs 42aare offset with respect to the relative position of tabs 30aon blade 22aas shown in FIG. 4A. Lastly, blade 46aof blade pair 46aand 46b, is illustrated in FIG. 4C. Blade 46ais substantially identical to blade 46b. Both blades 46aand 46beach include a straight, longitudinal cutting edge 48aand 48b; a rounded cutting tip 50aand 50b; an inside edge 52aand 52b; tabs 54aand 54blocated on the inside edges 52aand 52b, respectively; and, a rear end 56aand 56b. Tabs 54aand 54bare aligned to match with each other but are offset so that they do not align with tabs 42aand 42bof the first pair of blades 34aand 34b; nor do they align with tabs 30aand 30bof the first pair of blades 22aand 22b.

[0047] Blades 18 (22a, 22b, 34a, 34b, 46aand 46b) are received in slots 60 of the disks 20 illustrated in FIG. 5. Disks 20 have a center point 62 and each of the slots 60 has a major axis 64. Each axis 64 is slightly offset from disk center 62 so that tabs 30a, 30b, 42a, 42b, 54aand 54boverlap but do not interfere with each other.

[0048] When the apparatus 10 is assembled, the front tip 12 appears as shown in FIG. 3a and the rear end 16 appears as shown in FIG. 3B. FIG. 3D is a cross-sectional view of the assembled reamer 10 as illustrated in FIG. 3C and as seen from perspective 3D—3D. Note that tabs 54aand 54bof blades 46aand 46boverlap and touch each other. They are preferably welded in this position. In a similar fashion, tabs 30aand 30bof blades 22aand 22boverlap each other as do tabs 42aand 42bof blades 34aand 34b. To achieve this structure, slots 60 have a long access 64 that when extended slightly misses the center 62 of the disks 20 so that the tabs 30a, 30b, 42a, 42band 54aand 54bslightly overlap each other and do not interfere. Tabs 30a, 42a, 54aare preferably welded respectively to tabs 30b, 42band 54b.

[0049] When the apparatus 10 is assembled, the cutting tips 26a, 26b, 38a, 38band 50aand 50bhave edges which lie in essentially the same rounded, hemispherical plane so that the reamer 10 is rotated it cuts smoothly and evenly into the bone. Likewise, the sidewall 14 comprises the exterior long, straight cutting edges 24a, 24b, 36a, 36b, 48aand 48ball of which lie in the same, round cylindrical plane so that the reamer 10 is rotated, it cuts smoothly. The tabs may be welded to each other and/or disks 20 in order to keep the device in a permanent, assembled state.

[0050] The foregoing reamer is especially useful for large diameter, long bones. The interlinking of the blades gives the structure additional rigidity. In addition, it is relatively easy to manufacture and assemble and, therefore, it is inexpensive to distribute to the public.

[0051] FIG. 6 illustrates the second or preferred embodiment 100 of a small diameter, long bone reamer. The small diameter, long bone reamer 100 includes a cutting head 102, a cutting sidewall 104 and a rear end 106.

[0052] FIG. 7 illustrates the small diameter, long bone reamer 100 in an exploded view. Reamer 100 includes a group of four blades 150 divided into two sets or pairs. The first pair of blades in the group 150 comprise elements 110aand 110b; the second pair of blades in the group 150 comprise elements 130aand 130b. A central rod 140 is received in the boxlike cavity formed by the blades and serves to give additional rigidity to the resulting structure.

[0053] Blade 110ais illustrated in detail in FIG. 9A. Blade 110ais substantially identical to blade 110band lies on the opposite side of the apparatus 10 from blade 110a. Blade 110aincludes an interior cavity 112a, a rounded cutting tip 114a, a straight, longitudinal cutting edge 116a, a rear end 118a, and a plurality of inward facing tabs 120aalong the two long edges 122aof the interior cavity 112a.

[0054] FIG. 9B illustrates blade 130ain detail. Blade 130ais substantially identical to blade 130band includes a partially rounded cutting tip 132a, a long, straight, cutting edge 134a, a rear end 136a, and a plurality of tab receiving slots 138a. Slots 138areceive the tabs 120aand 120bof blades 110aand 110bof the first set.

[0055] The small diameter, long bone reamer 100, as seen in profile in FIG. 8C, is assembled in the following manner. First, the two blades 110aand 110bare placed side by side. Second, blade 130ais placed between the two blades 110aand 110bin such a way that tabs 120aand 120bengage the tab receiving slots 138a. Third, blade 130bis placed between blades 110aand 110band has its slots 138aengaged with the remaining tabs 120a. Fourth, rod 140 is placed down the middle of the structure to keep the blades 130aand 130bin position with respect to the tabs on blades 110aand 110b. When properly assembled, the cutting head 102 appears as shown in FIG. 8A and the rear 106 of the device appears as shown in FIG. 8B. The central rod 140 is illustrated in FIG. 10.

[0056] When the small diameter, long bone reamer 100 is assembled as shown in FIGS. 6, 7 and 8C, the tips 114a, 114b, 132aand 132bhave points which define a rounded, semi-circular form such that when the reamer 100 is rotated it cuts evenly and smoothly. Similarly, the cutting edges 116a, 116b, 134aand 134bdefine eight cutting edges which lie in a generally cylindrical plane such that when the reamer 100 is rotated it cuts smoothly.

[0057] The small diameter, long bone reamer 100 is somewhat different in structure from the large diameter, long bone reamer 10 because the dynamics of the cutting operation in a small bone are different from the dynamics of the cutting operation in a long bone. Four cutting blades 10a, 110b, 130aand 130bare required for the small diameter, long bone reamer because there isn't room to fit additional blades. In contrast, the large diameter, long bone reamer 10 has more room and, therefore, can accommodate six blades 18, namely blades 22a, 22b, 34a, 34b, 46aand 46b.

[0058] The small diameter, long bone reamer 100 according to the preferred embodiment of the invention is very strong, especially given the central support of rod 140; is relatively easy to manufacture; and, relatively inexpensive to distribute.

[0059] Long bone reamer 100 can be modified to achieve different performance characteristics. First of all, the round rod 140 shown in FIG. 10 can also have a square cross section as shown by rod 150 in FIG. 11. A square rod 150 produces a more rigid reamer 100 and also helps to keep debris out of the middle channel of the apparatus. It has also been found that if the square rod is welded at just one location to the blade package that the reamer apparatus 100 becomes relatively flexible—a characteristic that is desirable if a femur or tibia is curved. It is also possible to replace the metal rod 140 or 150 with a high temperature plastic rod for additional flexibility and ease of cleaning.

[0060] The four blade second embodiment 100 is preferred over the six blade first embodiment 10 because it is easier to construct the four blade embodiment 100 in smaller diameter sizes. While the small diameter reamer 100 preferably has four blades it would be possible to use the same interlocking concept to construct a reamer 100 with 4, 6, 8, 10 blades, etc.

[0061] Lastly, it may be desirable to add teeth to the leading edge of reamer 10 (or reamer 100) so that the reamer 10 can both drill and ream. FIG. 12 illustrates such a reamer 200 having teeth 202 on its leading edge 12.

[0062] While the invention has been described with respect to the preferred embodiment thereof, it will be appreciated by those of ordinary skill in the art that various modifications can be made to the structure and function of the invention without departing from the spirit and scope thereof.