Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B17/00—Surgical instruments, devices or methods
  • A61B17/14—Surgical saws
  • A61B17/15—Guides therefor
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B17/00—Surgical instruments, devices or methods
  • A61B17/14—Surgical saws
  • A61B17/15—Guides therefor
  • A61B17/154—Guides therefor for preparing bone for knee prosthesis
  • A61B17/155—Cutting femur
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B17/00—Surgical instruments, devices or methods
  • A61B2017/00831—Material properties
  • A61B2017/0084—Material properties low friction

Definitions

• the field of the invention relates to surgical cutting devices, and more particularly to surgical cutting blocks used for guiding saws and similar cutting devices in the shaping of femurs for the receipt of knee prostheses.
• a cutting block to force, hold captive or guide a blade along a reference cutting surface of a cutting guide, which is positioned along one or more sides of the cutting block.
• the reference cutting surface assures that the plane of the cut will be properly aligned on the bone by guiding the cutting path of the saw blade.
• Standard surgical cutting blocks are made from various grades of stainless steel that are quickly eroded by the high speeds at which most surgical blades operate. The result of such erosion is the production of a slurry, commonly referred to in the industry as “sludge, " some of which is deposited at the surgical site during surgery.
• the sludge contains the various elements present within the steel alloy which makes up both the cutting block and the surgical blades.
• a number of metals often found in stainless steel alloys, including both nickel and chrome, are left behind in the joint and eventually make their way throughout the patient's body. Nickel in particular is a known carcinogen. In a recent study, Sunderman et al.
• known dual cutting block systems which comprise a first cutting block for making anterior and posterior cuts, and a second cutting block for making the posterior chamfer and anterior chamfer cuts, suffer from several inherent difficulties.
• the first cutting block is designed to remove bone sections from the front and back faces of the distal portion of the femur, it is common for the body of the cutting block to exceed, or "hang over, " the sides of the distal end of the femur.
• the reference cutting surface is not flush to the bone but rather separated from it by some amount of air space. This makes the anterior and posterior cuts more difficult because the surgeon is not under good control of the cutting edge of the saw blade. Skiving, a tendency of the blade to be deflected by the bone and thus produce an inferior cut, is a significant problem in these situations.
• Another difficulty with existing dual cutting systems for femoral resection is the relatively small surface area presented by either cutting guide surface in a typical prior art chamfer cutting block.
• the small extent of the surface area particularly the relatively short length of the cutting guide relative to the length of the saw blade, significantly reduces the surgeon's ability to guide and direct the blade in making a proper cut.
• a cutting block and method of use that does not deliver toxic elements to the patient as a by ⁇ product of erosion of the cutting block and/or blade.
• a cutting block with superior hardness that is capable of retaining its original configuration without unacceptable fretting during surgery.
• a further need is for a cutting block and blade combination that has a relatively low coefficient of friction during operation, thereby reducing blade heating and bone tissue degradation.
• a femoral cutting block system that increases surgeon control and cut precision during the resectioning of a femur in knee surgery.
• the invention meets these objects by providing an improved cutting block having one or more cutting guide surfaces composed of a composition having a Knoop hardness of 466 or greater (under a 500 gm load or greater) , a chrome content of less than 10% by weight and a nickel content that is substantially less than 4% by weight.
• the cutting block of the invention may be entirely composed of the desired composition or may be a composite construction having a core unit composed of stainless steel or other material suitable for surgical applications that is fitted with and coupled to one or more units composed of the composition described above and configured with a desired cutting guide surface.
• Such units may be discrete blocks or laminas that are physically affixed to or inlaid into a desired surface of the core unit or alternatively may constitute coatings or deposits that are bonded to a desired surface of the core unit using known techniques.
• an improved configuration for the reference cutting surface of the cutting guide is provided.
• the present invention utilizes the use of ridges or protuberances to define a reference cutting surface, thereby greatly reducing the extent of actual physical, and therefore frictional, contact between the surgical saw blade and the cutting guide.
• two or more raised rails are configured on the surface of the cutting guide.
• semi-spherical protuberances are arrayed in linear or curvilinear rows, or at random, across the surface of the cutting guide. The summits of the protuberances define the reference cutting surface and are the only part of the cutting guide that actually contacts the saw blade during an operation.
• a dual block femoral cutting block system comprises the use of two stationary cutting blocks, each designed to make a standard cut (posterior or anterior) in a plane more or less parallel to the anatomical axis of the femur, and a chamfer cut opposite the position of the standard cut in a plane at an acute angle to the anatomical axis of the femur.
• the blocks also differ in the configuration of means of attachment to the distal or knee-end of the femur.
• One block of the dual block system is adapted to be received over the planar surface of the distal femoral cut, which is substantially perpendicular to the anatomical axis of the femur and is the first cut made when a femur is being resectioned for receipt of a femoral component of a knee prosthesis. Because the first block in the system is used to make a chamfer cut, the distal end of the femur is converted from a planar to an angled surface having three distinct planes,- one the result of the original distal femoral cut and the other created by the chamfer cut and posterior or anterior cuts made using the first cutting block. For this reason, the attachment means of the second cutting block in each system must be angled in order to be snugly received over the end of the femur. It will be apparent therefore that two cutting block systems, comprising four distinctly configured cutting blocks are possible within this system.
• the surgical device and method of the invention are advantageous over prior art in that toxic deposits within the joint as a result of surgery are minimized, in that the tolerances of the reference cutting surface are maintained throughout surgery, and in that blade heating due to friction between the blade and cutting guide surface is reduced, in that surgeon control in making cuts, particularly chamfer cuts is improved and in that the placement and precision of cuts is improved.
• FIGS. 1A & IB are views in perspective of two embodiments of a cutting block of the invention.
• FIGS. 2A & 2B are views in perspective of two saw-captive embodiments of a cutting of the invention.
• FIGS . 3A & 3B are views in perspective of a cutting block of the invention showing a three-rail configuration of a the reference cutting surface.
• FIGS. 4A & 4B are views in perspective of a cutting block of the invention showing the use of protuberances to define a reference cutting surface,
• FIGS. 5A & 5B are views in perspective of cutting blocks of a first embodiment of the dual cutting block system of the invention showing cutting guides with planar cutting reference surfaces .
• FIGS . 6A, 6B & 6C are views in perspective of cutting blocks of a first embodiment of the dual cutting block system of the invention showing cutting guides using rails and protuberances to define the cutting reference surface.
• FIGS. 7A, 7B, 7C, & 7D are views in cross- section of first and second saw-free embodiments of the dual cutting block system of the invention.
• FIGS. 8A, 8B, 8C & 8D are views in cross- section of first and second saw captive embodiments of the dual cutting block system of the invention.
• FIG. 9A is a view in perspective of the adaptor of the invention.
• FIG. 9B is a view in cross section of the adaptor of the invention in combination with a cutting block.
• FIG. 10A is a view in perspective of the sizing plate of the invention.
• FIG. 10B is a view in cross section of the sizing plate of the invention.
• the cutting reference surface is a key element of any cutting block or other surgical device because it is the surface that the surgeon uses to guide a saw blade or similar instrument to cut and section bone tissue.
• the frictional and compositional characteristics of the cutting reference surface determine to a large degree the effectiveness of cut made by the surgeon.
• cutting reference surface 14 is a substantially even, continuous plane, across which and in physical contact with which a surgical saw blade passes: In this configuration of the invention, a flat surface of the more or less planar saw blade is in substantial physical contact with cutting reference surface 14.
• cutting guide 14 of cutting block 12 is provided with two or more rails 16. The rails 16 are elevated above the general surface 15 of cutting guide 12.
• the rails may be preformed on general surface 15 of cutting guide 12 by casting the cutting guide in a mold or tooling a cutting guide to form such rails according to methods well known in the art.
• the rails can be formed by partially capturing rods 18 within tracks 20 which have been formed within cutting guide 12 on general surface 15.
• Rods 18 may be comprised of the same composition as that of cutting guide 12, or may be fabricated from an entirely different composition as described further below.
• the number of rails 16 or rods 18 (collectively hereafter as “rails") is at least two and is preferably three in number.
• the rails are configured to rise an equal distance above general surface 15 so that the apices of the rails define a plane substantially parallel with the plane occupied by general surface 15.
• the plane defined by the rails forms the cutting reference surface of the cutting guide. It will be appreciated by those skilled in the art that the frictional contact between a saw blade and a reference surface defined by a limited number of rails will be substantially less than the frictional contact between two flush planar surfaces.
• the apices of the all three rails will define such a single plane.
• each rail may be curvilinear instead, each rail defining an arc the shape which is limited only by the physical dimensions of the general surface 15 of cutting guide 12.
• configuring the rails to be arc-shaped can further reduce frictional contact by further minimizing the amount of frictional contact between the saw blade surface and the rails.
• a third aspect of the cutting reference surface of the invention entails the use of convexly curved, lens--shaped protrusions 22, or alternatively, substantially spherical objects 24, in two or more linear or curvilinear arrays, as illustrated in Fig. 4, or scattered in or more or less random fashion across the cutting guide.
• the protrusions can be formed on general surface 15 of cutting block 12 by casting the cutting block as a single piece or by attaching preformed, lens-shaped objects having the desired dimensions to the general surface 15 by any means well-known in the art.
• substantially spherical objects 24, such as ball bearings and the like can be captured within tracks 26 on the reference surface 15.
• a plurality of substantially spherical objects 24 are captured within the adjacent tracks.
• the objects 24 may be free to move within the tracks 26, or more preferably are arrayed adjacent to one another in fixed position.
• the objects 24 are captured so that a portion of each object protrudes a substantially equal distance above the cutting reference surface, such that the apices together will define a single plane that is substantially parallel to the general surface 15. This plane constitutes the cutting reference surface of cutting guide 12 across which the surgical saw blade or similar instrument may pass.
• the cutting reference surface 14 is comprised of a material or materials designed both to reduce friction between the cutting surface and a surgical saw blade and, more importantly, to reduce the introduction and deposition of toxic materials to the patient at the surgical site.
• cutting reference surface 14 is preferably comprised of a material having a high degree of harness coupled with low chrome and nickel content. Satisfactory parameters for such a material include Knoop hardness of 466 or greater (under a 500 gm load or greater) , a chrome content of from 0% up to 10% and a nickel content of from 0% up to 4%.
• a preferred material would have a Knoop harness of 800 or greater (under a 500 gm load or greater) , a chrome content of from 0% to 8% and a nickel content of from 0% to 3%.
• a most preferred material would have a Knoop hardness of 1000 or greater (under a 500 gm load or greater) , a chrome content of from 0% to 6% and a nickel content of from 0% to 2% or less.
• cutting guide 12 can itself be entirely composed of one of the desired materials discussed above and can be laminated or otherwise affixed at desired positions an angles on a core unit that may or may not have the Knoop hardness and alloy characteristics of the cutting guide material.
• such cutting surface may be achieved by directly depositing a material having these characteristics on a preformed cutting guide surface having a desired configuration, so long as the thickness of the material deposited is sufficiently thick to perform under normal surgical conditions.
• the entire block may be fabricated out of a composition having the desired hardness and chemical composition outlined above, provided that doing so is time and cost effective.
• Suitable materials having the desired hardness and alloy characteristics include ceramics such as zirconia, aluminas; certain borides such as titanium diaboride and boron carbide; nitrogen-hardened titanium and similar materials. Such materials are known in the art and can be readily obtained, for example, from Coors Ceramic Company (Golden, Colorado) . Although any of the materials just listed have the desired characteristics for cutting surface material as described above, ceramics like zirconia with very high Knoop hardness, high fracture toughness and low thermal conductivity are preferred. Such compounds are additionally advantageous because they have particularly low coefficients of friction when used with standard metallic cutting blades, thus reducing heat generation, and are essentially nickel and chrome- free.
• the system of the present invention comprises the use of two stationary cutting blocks, each designed to make a standard cut (posterior or anterior) in a plane more or less parallel to the anatomical axis of the femur, and a chamfer cut opposite the position of the standard cut in a plane at an acute angle to the anatomical axis of the femur.
• the blocks also differ in the configuration of means of attachment to the distal or knee-end of the femur.
• One block of the dual block system is adapted to be received over the planar surface of the distal femoral cut, which is more or less perpendicular to the anatomical axis of the femur and is the first cut made when a femur is being shaped for receipt of a femoral component of a knee prosthesis. Because the first block in the system is used to make a chamfer cut and the opposing posterior or anterior cut, the distal end of the femur is converted from a planar to an angled surface having two distinct planes, one the result of the original distal femoral cut and the other created by the chamfer cut made using the first cutting block. For this reason, the attachment means of the second cutting block in each system must be angled in order to be snugly received over the end of the femur.
• a first cutting block system 28 shown in FIG. 7A-B is provided with a first cutting block 30 and a second cutting block 38.
• First cutting block 30 is provided with an anterior cutting guide 32, a posterior chamfer cutting guide 34, and an attachment means 35, which further comprises a planar attachment surface 36 and attachment pins 37 and 37' .
• Second cutting block 38 is provided with a posterior cutting guide 40, an anterior chamfer cutting guide 42 and an attachment means 43, which further comprises a biplanar, angled attachment surface 44 and attachment pins 45.
• a second cutting block system 46 as shown in FIG. 5, 6 & 7C-7D, comprises a first cutting block 48 and a second cutting block 56.
• First cutting block 48 is provided with a posterior cutting guide 50, an anterior chamfer cutting guide 52, and an • attachment means 53, which further comprises a uniplanar attachment surface 54 and attachment pins 55 and 55' .
• Second cutting block 56 is provided with an anterior cutting guide 58, a posterior chamfer cutting guide 60 and an attachment means 61, which further comprises an angled, biplanar attachment surface 62 and attachment pins 63.
• each of the cutting guides 40, 42, 50 and 52 can be provided with a reference cutting surface having any of the configurational or compositional characteristics described in Section I above.
• the cutting may be nothing more than the substantially planar side of cutting block itself, as shown in FIG. 5A, or it may be formed on an insert (or lamination) 64, as shown in FIG. 5B.
• the configuration of the reference cutting surface will be defined by the presence of two or more rails 16, created either by molded raised portions of the cutting block or by captured rods 18, as shown in FIGS. 6A-6B.
• the reference cutting surface is defined by three substantially linear rods which are captured within the cutting block, each having an exposed curved portion equivalent in extent and elevation to each other rod.
• the summit or ridge of each rod collectively defines a reference cutting surface for the cutting guide of the cutting block.
• Such a configuration is preferentially employed in each of the type of cutting guide present in each cutting block of the two cutting block systems.
• composition of the body of the cutting blocks it is preferred to use surgical grade steel, although any hard, durable, erosion- resistent, non-toxic composition would be acceptable, including the compositions discussed above that are preferred for that portion of the cutting guide that defines the reference cutting surface.
• compositions discussed above that are preferred for that portion of the cutting guide that defines the reference cutting surface.
• the cutting guides themselves, and in particular the cutting reference surfaces it is highly preferred to use compositions having a high Knoop hardness and very low or non- existent levels of chrome and nickel, such as ceramics as is discussed in greater detail in Section I above.
• the cutting blocks of these systems can be configured with captured cutting guides in which the cutting guide takes the form of a through channel and the reference cutting surface is defined on of the interior surfaces of the through channel.
• cutting blocks with cutting guides positioned on one or more outside faces of the cutting block are suitable for virtually all types of bone surgery, saw-captive blocks are preferred by some surgeons.
• the cutting blocks described immediately above can be configured with saw-captive cutting guides in which the cutting guide takes the form of a through channel and the reference cutting surface is defined on one or both of the broad interior surfaces of the through channel.
• Such saw-captive guides can be also be configured to provide open channels extending laterally from each end of the cutting block.
• a first saw-captive cutting block system 66 shown in FIG. 8A-8B is provided with a first cutting block 68 and a second cutting block 80.
• First cutting block 68 is provided with an anterior cutting guide 72 in a first through channel 73, a posterior chamfer cutting guide 74 in a second through channel 75, and an attachment means 76, which further comprises a planar attachment surface 77 and attachment pins 78 and 78' .
• Second cutting block 80 is provided with a posterior cutting guide 82 in a first through channel 83, an anterior chamfer cutting guide 84 in a second through channel 85, and an attachment means 86, which further comprises a biplanar, angled attachment surface 87 and attachment pins 88.
• a second cutting block system 90 comprises a first cutting block 92 and a second cutting block 106.
• First cutting block 92 is provided with a posterior cutting guide 94 in a first through channel 96, an anterior chamfer cutting guide 98 in a second through channel 100, and an attachment means 102, which further comprises a uniplanar attachment surface 104 and attachment pins 105.
• Second cutting block 106 is provided with an anterior cutting guide 108 in a through channel 110, a posterior chamfer cutting guide 112 in a second through channel 114, and an attachment means 116, which further comprises an angled, biplanar attachment surface 117 and attachment pins 118.
• an adaptor 100 is provided for use with the cutting blocks and cutting block systems just described.
• the adaptor 100 is comprised of a plate 102, placement prongs 104 and 104', and an alignment prong 106.
• the adaptor 100 is configured to be received over the planar distal femoral cut of a femur or similar cut on some other bone.
• Adaptor 100 is received over the distal femoral cut by receipt of the placement prongs within drill holes that would otherwise receive the placement prongs of various cutting blocks.
• adaptor 100 is used as the coupling for attaching various instruments, including the cutting blocks and cutting block systems of the present invention, as shown in FIG. 9B.
• Adaptor 100 can be comprised on any strong, durable, non-rusting product such as plastic or various metals alloys, although surgical steel is preferred
• a sizing plate 110 will now be described. Because all bones, including femurs, vary in size and morphology, it is necessary to configure cutting blocks and similar instruments in a variety of sizes, so that the cutting planes of the cutting block can be matched to the bone shape and size. Proper sizing is important because too shallow a cut will result in poor fit of the prosthesis and too deep a cut will expose the femoral cortex, decreasing the stability of the femur and longevity of the prosthetic implan . Thus, according to one aspect of the invention, a cutting block sizing plate 110 is provided. Sizing plate 110 is comprised of a substantially planar block member 112 in which are arrayed a series of through channels 114.
• Block member 112 may also be provided with a slot 116 that is configured to allow the sizing plate to be snugly fitted over adaptor 100.
• Sizing plate 110 may be comprised of any suitable material that is both strong and durable, such as metal alloys and some plastic polymers, however, surgical steel is preferred because of it is both strong and inexpensive.
• the through channels 114 of sizing plate 110 are aligned at an angle to simulate the angle of a particular cutting guide in a cutting block.
• the channels 114 are configured to receive a drill bit of a desired length, which is extended through the channels and into the bone.
• the drill bit is extended through the channel and into the femur. If the bit does not emerge from the femur, then the cut is too deep and a larger cutting block is chosen. If the drill bit passes through air before entering the femur then the cut is too shallow and a smaller block must be chosen.
• a method of resectioning the distal or knee-end of a femur for receipt of the femoral component of a knee prosthesis is described using the second cutting block system 46 and unique reference cutting surfaces of the invention described above in Sections I and II.
• Resection of a patient's knee begins with the surgical opening of the knee and exposure of the distal end of the femur. Although this procedure is well known to knee surgeons and other skilled in the art, a standard medial parapatellar arthrotomy is made and anterior skin incision at the knee to expose the patella. After the patella is exposed, it is everted and the knee flexed for the remainder of the operation.
• the intramedullary channel of the femur is identified so that an initial distal femoral cut can be made to produce a flat surface across the top of the femur that occupies a plane substantially perpendicular to the intramedullary channel.
• the location pins of first cutting block 48 are hammered into the flat surface at the distal end of the femur created by the distal femoral cut in an orientation to secure removal of a posterior section of the femur.
• the pins 55 of attachment means 53 secure the block to femur and help to prevent the block from torquing out of proper alignment.
• a section of the posterior lateral portion of the femur is removed using a powered hand or similar device, using the posterior cutting guide 50 as a reference.
• the resulting cut produces a planar surface on the posterior side of the distal end of the femur that occupies a plane substantially perpendicular the intramedullary channel of the femur.
• resection of an anterior portion of the femur is accomplished with a powered surgical saw using the anterior chamfer cutting guide 52 as a reference.
• the resulting cut produces a planar surface on the anterior side of the femur that intersects the surface created by the initial distal femoral cut at an acute angle, generally of substantially 45°.
• first cutting block 48 is removed and the second cutting block 56 is affixed.
• the contour of the attachment surface 62 of the second cutting block is biplanar and angled to compliment precisely and snugly receive the angled surface created on the end of the femur using the first cutting block 48.
• a first cut is made using the anterior cutting guide 58 to remove much of the anterior condyles and form a flat surface more or less parallel to the surface created using the posterior cutting guide 50 of the first cutting block.
• the final resection of the femur is accomplished using the posterior chamfer cutting guide 60 to remove a small portion of bone at the end of the original posterior cut, thereby creating five distinct and sequentially intersecting surfaces of the distal end of the femur.
• these cut and prepared surfaces compliment the angled interior surface of the femoral component of a knee prosthesis, allowing the prosthesis to be closely fitted over the femur with substantially complete contact between the bone of the femur and the inner angled surfaces of the implant. From the foregoing, it will be appreciated how the objects and features of the invention are met.
• the hardness of the cutting guide surface helps to maintain an even cutting reference surface that is not liable to fret.
• the preferred materials are also low in toxic metal ions which my be shed in residue during surgery. Further, the hardness of the material, particularly ceramics such as zirconia, ensure that fretting is minimized which reduces friction and thus heat generation during operation and reduces sludge production that can be shed during the operation in the treatment area.

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• Health & Medical Sciences (AREA)
• Surgery (AREA)
• Life Sciences & Earth Sciences (AREA)
• Biomedical Technology (AREA)
• Public Health (AREA)
• Oral & Maxillofacial Surgery (AREA)
• Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
• Veterinary Medicine (AREA)
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• Engineering & Computer Science (AREA)
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• Heart & Thoracic Surgery (AREA)
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• Surgical Instruments (AREA)
• Prostheses (AREA)

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• 1993
  • 1993-12-28 EP EP94905533A patent/EP0675698A4/fr not_active Withdrawn
  • 1993-12-28 WO PCT/US1993/012601 patent/WO1994014366A2/fr not_active Ceased
  • 1993-12-28 AU AU59609/94A patent/AU5960994A/en not_active Abandoned

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