Chain saw, a component for a chain saw and a system for operating a saw

Abstract

Improved chain saws, components for chain saws, methods of manufacturing chain saws and components, and methods of using chain saws and components are disclosed.SOLUTION: In some embodiments, the chain saw has a saw bar and a plurality of links, wherein a first link has a hook that engages a recess of a second link, thereby coupling the first link and the second link together and allowing the links to articulate without disengaging. The sorbers may include rails and the links may include grooves such that the links straddle and rest on the rails. The rail may include a protrusion and the groove of the link may include a notch for receiving the protrusion such that the protrusion prevents misalignment of the links. The links may have conical or pyramidal blade teeth. The chain may be bidirectional. Robotic and automated manipulation of saws and other instruments is also disclosed. SELECTED DRAWING: Figure 5A

Description

[Technical Field]

[0001] The present disclosure relates to chainsaws, components for chainsaws, methods of manufacturing chainsaws and components, and methods of using chainsaws and components. The present disclosure also relates to systems for robotic and automated surgery, particularly orthopedic surgery, such as knee surgery or spine surgery.

[0002] REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 63 / 058,216, filed July 29, 2020, U.S. Provisional Patent Application No. 63 / 085,290, filed September 30, 2020, U.S. Provisional Patent Application No. 63 / 147,033, filed February 8, 2021, U.S. Provisional Patent Application No. 63 / 154,379, filed February 26, 2021, U.S. Provisional Patent Application No. 63 / 209,540, filed June 11, 2021, and U.S. Nonprovisional Patent Application No. 17 / 443,646, filed July 27, 2021. These earlier applications are incorporated by reference in their entireties. [Background technology]

[0003] Many people suffer from orthopedic conditions in which cutting bone or other tissue is necessary or effective. As an example, many people suffer from severe joint problems that require a surgical procedure or technique to implant an artificial joint. Each year, physicians implant millions of artificial joints, but these implantation procedures require the patient's bone to be reshaped to accept the implant. The most common joint surgery is knee replacement. Bone repair in knee replacement involves making a series of uniform incisions at the ends of the two major adjacent long bones that will be joined by the implant. Ideally, these incisions are made to precisely complement the shape of the implant. The flat surface of the healthy bone faces the corresponding surface of the implant, resulting in the strongest healing of the joint with reduced risk of complications or implant failure.

[0004] The requirements for sawing bone or other tissue during a surgical procedure exceed those for other sawing applications. Specifically, in a surgical procedure, the saw must be sterile, the saw burr must be easy to control by the surgeon, and vibration and loud noise must be minimized. Additionally, among other considerations, the saw must perform the cut in a manner that does not generate excessive heat, the surgical procedure must be free of metal particles or other contaminants in the surgical field, and the surgical procedure must result in the cutting of hard bone or other tissue while minimizing trauma to adjacent soft tissue.

[0005] Bone is a living material that contains cells that remodel bone and fight infection. After amputation, it is important that the hard parts of the bone remain intact and that the bone does not become devitalized (cells die within the bone). Devitalized bone heals poorly and is less resistant to infection. In implanted joints, devitalized bone compromises the interface between the bone and the implant, increasing the risk of failure.

[0006] One cause of bone devitalization is excessive heat caused by friction of the cutting device against the bone. Without preventative measures, bone temperatures can exceed 200°C. Avoiding high temperatures is important to avoid thermal necrosis, i.e., cell death due to heat, or damage to bone cells or delayed healing due to thermal effects. Bone temperature can be controlled by shortening the cutting time and by using water irrigation. However, this increases the overall procedure time, and irrigation can obscure the cutting field and cause splashing due to vibrations of the cutting device.

[0007] The remains of the cut bone must be removed from the body. Preferably, the bone cut debris is a mixture of powdered bone and body fluids. This slurry should be removed from the cut field. Leaving large amounts of bone fragments behind is undesirable, as they can act as nidus for infection if they become deposited in tissue.

[0008] Bones vary in hardness. Cortical bone—the weight-bearing bone tissue located on the outside of long bones—is relatively hard. In contrast, spongy bone—the marrow tissue located on the inside of long bones—is relatively soft. There is a great deal of variation in bone texture and hardness.

[0009] The cuts made by a bone saw are ideally uniform in the plane of the saw and ideally straight at the cut boundary. This is necessary to allow optimal healing when two bone surfaces face each other or when one bone surface faces an implant surface. Surfaces that are not coplanar, i.e., uneven surfaces, create voids that may take a long time to heal or may never heal. Some saws are prone to undesirable drift of the saw away from the intended plane, called skiving. Some saws also have cutting elements that are prone to a gripping action, resulting in unguided movement of the saw, which is also undesirable.

[0010] In surgical procedures, bone saws are operated by a surgeon in an operating room environment. Preferably, the saw produces minimal vibrations, which can then be easily controlled by the surgeon. This is important for a number of reasons. Bones are typically located next to important and sensitive soft tissues, such as blood vessels and nerves, and uncontrolled movement can result in damage to such tissues. Uncontrolled movement can also result in fewer desirable cuts.

[0011] It is preferable for saws to be thin. In common applications, it is desirable to minimize the amount of bone removal when cutting bone. Additionally, there are many other orthopedic indications where a miniature saw is required, one example being surgical implants into vertebrae. Therefore, it is desirable to provide a saw design that can be made small enough to perform its intended function.

[0012] In a typical bone cutting procedure, the device currently used to cut bone is a sagittal saw. The saw is rectangular in shape, with its cutting blade located at one end. The cutting blade moves back and forth in an arc, much like a pendulum. This movement occurs at extremely high speeds, i.e., up to 20,000 times per minute.

[0013] Sagittal saws have several drawbacks. They generate significant vibrations due to the rapid movements and large forces used, making it difficult for surgeons to use with precision. Sagittal saws can be extremely loud. In fact, noise-induced hearing loss is an occupational hazard for operating room personnel. Metal particles can be chipped off the sagittal saw and deposited in the wound. The high speed of the sagittal saw can also generate droplet pathogens, which can be harmful to the patient, the sterile field, and the medical personnel involved. The high speed of the sagittal saw also generates heat in the bone. This heat can kill cellular elements within the bone, thereby inhibiting bone healing. To reduce heat, surgeons often limit the continuous use of the sagittal saw. However, this increases the overall duration of the procedure. The sagittal saw often deviates from its intended path, resulting in a curved, rather than flat, bone surface. For these and other reasons, sagittal plane saws are not ideal.

[0014] While chainsaws have long been used for applications such as wood cutting, to date, they have not been successfully deployed for routine surgical use. This is due to the many technical challenges of chainsaws for the specific requirements of bone and other surgery. U.S. Patent No. 9,616,512 to Viola discloses a bone-cutting chainsaw. U.S. Patent No. 9,616,512 is incorporated by reference herein in its entirety. The embodiments described herein improve the safety and effectiveness of surgical chainsaws for cutting bone and other tissue.

[0015] Robotic systems for orthopedic surgery are currently known and in use. Some embodiments of the present invention relate to robotic or automated systems that have one or more advantages over such prior art systems.

[0016] An exemplary type of system in which robotics is used is an orthopedic stereotaxic instrument for guidance during orthopedic surgery. Such a system typically includes a camera, a computer, and a tracking array. The tracking array is placed at a fixed location on the patient's body, and the camera provides real-time images of the tracking array to a computer, which converts this image data into location data for tracking the patient's anatomy. A robot equipped with surgical tools can be guided based on the location data aligned with the patient's anatomy.

[0017] One example of such a robotic system currently in use is the Mako Total Knee Arthroplasty (TKA) System available from Stryker Corporation. The Mako TKA System includes a robotic unit with a robotic arm, a camera unit with a stereo 3D camera, and a guidance module. The Mako TKA System also includes tracking arrays, including a femoral tracking array attached to the patient's femur and a tibial tracking array attached to the patient's tibia, and a handheld probe that can be positioned at various locations by the surgeon. The tracking arrays and probe are equipped with reflective marker discs, allowing the camera to track their location. A saw attachment, such as a sagittal plane saw, can be attached to the robotic arm.

[0018] In use, the robotic unit sits loosely and securely on the floor. The camera unit is mounted on a mast that is also firmly positioned on the floor. The camera observes a tracking array placed on the patient's body, and the system converts the camera image data into location information aligned with anatomical points on the patient's body. The system uses this location information to adjust the location of the robotic arm and saw to align them with the desired location of the patient's knee joint. As the patient's lower limb moves, the robotic arm is realigned based on visual feedback from the camera.

[0019] Other examples of orthopedic stereotaxic instruments are known. For example, the Rosa Knee System, available from Zimmer Biomet, is another such instrument. Like the Mako TKA System, the Rosa Knee System utilizes visualization of anatomical markers to position the robotic arms. The robotic arms of the Rosa Knee System may carry incision guides to guide the surgical incisions. [Prior art documents] [Patent documents]

[0020] [Patent Document 1] U.S. Patent No. 9,616,512 Summary of the Invention [Problem to be solved by the invention]

[0021] Improvements in the art of such prior art systems are desirable. [Means for solving the problem]

[0022] The present invention relates to improved chainsaws, components for chainsaws, methods of manufacturing chainsaws and components, and methods of using chainsaws and components.Embodiments of the present invention provide improved efficiency and / or safety when cutting bone or other tissue in surgical procedures.

[0023] In some embodiments, the sawbar has rails and the links have grooves so that the links straddle the rails. The rails can have protrusions and the link grooves can have notches that receive the protrusions, so that the protrusions prevent displacement of the links from the sawbar away from the path of the chain around the sawbar.

[0024] In some embodiments, the chainsaw includes a sawbar and a plurality of links arranged around the sawbar in a chain-like fashion, with a first link having a hook that engages a recess in a second link, thereby coupling the first and second links and allowing the first and second links to articulate relative to one another without disengaging when the chain is driven around the sawbar. The links may have one or more cutting teeth oriented so that a force resulting from a cutting action is directed in a substantially vertical direction, i.e., perpendicular to the path of the chain and into the sawbar. The links may have cutting teeth in the shape of a cone or a pyramid, including an oblique pyramid. The links may have cutting teeth aligned along lateral sides of the links. The crests of the cutting teeth may be aligned along the lateral sides of the links. The cutting teeth along one lateral side may be staggered relative to the cutting teeth along the opposite lateral side.

[0025] In some embodiments, a hard coating can be applied to the contact surfaces of the sawbar, i.e., the surface of the sawbar that contacts the link, and / or the contact surfaces of the links, i.e., the surface of the link that contacts the sawbar. The hard coating reduces friction and heat generation. The hard coating can also reduce wear and avoid the need for lubricants, which is beneficial in medical equipment where most lubricants are not acceptable. The hard coating can be a diamond coating. Other exemplary coatings include titanium nitride and titanium alloys and other materials that can be applied by vapor deposition or other processes. Hard coatings, such as diamond coatings or other coatings disclosed herein, can also be used to coat the cutting teeth of the links to achieve similar benefits in terms of reduced friction, heat, and wear.

[0026] In some embodiments, the chainsaw can include a protective element that protects the chainsaw when threaded through the guide cutting block. The protective element can include first guide posts located adjacent to the chain and spaced apart from the chain along a first longitudinal side of the saw bar, and second guide posts located adjacent to the chain and spaced apart from the chain along a second longitudinal side of the saw bar. The guide posts can be wider than the chain. The guide posts can be retractable. In other embodiments, the protective element can be a retractable cover.

[0027] In some embodiments, a method of orthopaedic surgery can include operating a chainsaw chain in a first direction to cut bone, and operating the chainsaw chain in a second direction opposite the first direction. The blade teeth can be symmetrical or asymmetrical so that the cutting function is the same or different in the opposite directions.

[0028] In some embodiments, an orthopaedic surgical method may include cutting a precise recessed volume into the bone with a chainsaw and inserting an implant shaped to fit the recessed volume into the bone.

[0029] In some embodiments, systems and methods are provided for manufacturing links for chainsaws. In some embodiments, systems and methods are provided for inexpensively sharpening and / or creating profiles for blades on chainsaws and other saws.

[0030] In some embodiments, a method of manufacturing a link for a chainsaw includes using a metal injection molding process to mold a link having a first lateral side, a second lateral side, and a plurality of cutting teeth, and using a grinding process (e.g., a double-disc grinding process) to grind the first lateral side and the second lateral side of the link.

[0031] In some embodiments, a method of orthopaedic surgery may include robotically controlling a chainsaw to cut bone.

[0032] In some embodiments, a surgical robotic system includes an arm with a first end and a second end, the first end of the arm adapted to be coupled to a patient's bone, and the second end of the arm adapted to be coupled to an instrument, a robotic arm, or a computerized robotic unit including a robotic arm. The robotic arm can be configured to carry an instrument, such as a bone saw or a guide for a bone saw.

[0033] In some embodiments, an automated system for surgery includes a chainsaw configured to cut bone, a feedback system configured to measure one or more conditions of the chainsaw while the chainsaw is operating, and a control system configured to receive information from the feedback system and, based on the feedback, automatically modify inputs to the chainsaw to modify operation of the chainsaw.

[0034] Further examples and features of embodiments of the invention will be apparent from the drawings and detailed description.

[0035] The accompanying drawings illustrate examples of the devices, components, and methods disclosed herein and, together with the detailed description, serve to explain the principles of the invention. [Brief explanation of the drawings]

[0036] [Figure 1] 1A-1C illustrate an exemplary embodiment of a chainsaw cartridge according to the present disclosure. [Figure 2] 2 shows a single link for a cutting chain of a chainsaw, for example the cutting chain of the chainsaw cartridge of FIG. 1; FIG. [Figure 3] 1 is a schematic diagram of the layout of the teeth of the link. [Figure 4A]1 illustrates an exemplary embodiment of a sawbar that can be used with a chainsaw in accordance with the present invention. [Figure 4B] 10 illustrates another exemplary embodiment of a sawbar that can be used with a chainsaw in accordance with the present invention. [Figure 5A] 4B is an enlarged view of the sawbar of FIG. 4A and a partial cutaway view of one chain of links assembled to the sawbar. [Figure 5B] 4B is an enlarged end view of the sawbar of FIG. 4A at the distal end of the sawbar, showing a single link. FIG. [Figure 5C] FIG. 5C is an enlarged view of a portion of FIG. 5B. [Figure 6A] 1 is an exploded view of a drive cog assembly of a chainsaw according to the present invention; [Figure 6B] FIG. 6B is a side perspective view of the drive cog assembly of FIG. 6A. [Figure 6C] FIG. 6B is a top perspective view of the drive cog assembly of FIG. 6A. [Figure 7A] FIG. 1 shows an example of a sawbar with a sprocket wheel. [Figure 7B] FIG. 1 shows an example of a sawbar with a hard coating and no sprocket wheel. [Figure 8] 1 shows an exemplary embodiment of a chainsaw with a guide post according to the present invention; [Figure 9A] 1 shows an exemplary embodiment of a chainsaw with a protective cover according to the present invention; [Figure 9B] 9B shows the embodiment of FIG. 9A with the protective cover in a retracted state. [Figure 9C] 1 illustrates an exemplary embodiment of a chainsaw with the cutting element in a retracted position. [Figure 9D] FIG. 9D shows the embodiment of FIG. 9C with the cutting element in an extended state. [Figure 9E] 1 illustrates an exemplary embodiment of a chainsaw bar passing through a cutting guide. [Figure 10]1 is a diagram showing an embodiment of a chainsaw according to the present invention, illustrating a state in which a chainsaw drive head is attached to a chainsaw cartridge. FIG. [Figure 11A] 1 shows a cutting link of a prior art chainsaw; [Figure 11B] FIG. 11B is a cross-sectional view of the prior art link of FIG. 11A in a normal position. [Figure 11C] FIG. 11B is a cross-sectional view of the prior art link of FIG. 11A in a laterally offset position. [Figure 11D] FIG. 11B is a cross-sectional view of the prior art link of FIG. 11A in a tilted position. [Figure 11E] FIG. 11B is a side view of the prior art link of FIG. [Figure 11F] FIG. 11B is a plan view of the prior art link of FIG. 11A. [Figure 12A] 10A-10C show exemplary placement of cutting elements on three sides of a link. [Figure 12B] 10A-10C illustrate exemplary arrangements of cutting elements on two inclined surfaces of a link. [Figure 12C] 10A-10C illustrate exemplary placement of cutting elements on the top surface of a link. [Figure 12D] FIG. 10 illustrates an exemplary arrangement of cutting elements on the top surface of a link, with one row of cutting elements along one lateral side of the link and another row of cutting elements along the other lateral side of the link. [Figure 13A] FIG. 10 shows another embodiment of a sawbar with rails, where the links have grooves for slipping the links over the rails. [Figure 13B] 13B is a schematic diagram of the embodiment of FIG. 13A. [Figure 13C] FIG. 5B is another view of the embodiment shown in FIGS. 5A-5C. [Figure 13D] 13D is a schematic diagram of the embodiment of FIG. 13C. [Figure 13E] 10 is a schematic diagram of another embodiment of a sober with links. [Figure 14A]FIG. 1 is a top perspective view of an exemplary implant shaped to a vertebra. [Figure 14B] FIG. 14B is a bottom perspective view of the implant of FIG. 14A. [Figure 14C] 14A and 14B illustrate a vertebra with a recessed volume having a form-fitting shape that can be achieved by certain embodiments of the present invention to receive the implant of FIGS. 14A and 14B. [Figure 14D] FIG. 14D is a front view of a custom saw bar for cutting and forming the sculpted bone space of FIG. 14C in accordance with certain embodiments of the present invention. [Figure 15A] FIG. 1 is a top view of one embodiment of a chainsaw with a surgical handle. [Figure 15B] FIG. 15B is a side perspective view of a chainsaw with the surgical handle of FIG. 15A. [Figure 15C] FIG. 15B is a rear perspective view of a chainsaw with the surgical handle of FIG. 15A. [Figure 15D] 15B shows the chainsaw with the surgical handle of FIG. 15A being moved in a first direction. [Figure 15E] FIG. 15B shows the chainsaw with the surgical handle of FIG. 15A being moved in a second direction. [Figure 16] 1 shows a guard that can be attached to a chainsaw. [Figure 17A] 1 is a top view of an exemplary embodiment of a drive train mechanism for a chainsaw according to the present invention; [Figure 17B] FIG. 17B is an enlarged perspective view from below of the drive train mechanism of FIG. 17A. [Figure 18A] 10 is an edge view of another exemplary embodiment of a drive train mechanism for a chainsaw according to the present invention; [Figure 18B] 18B is a perspective view of the drive train mechanism of FIG. 18A from a first side of the chainsaw. [Figure 18C] 18B is a perspective view of the drive train mechanism of FIG. 18A from a second side of the chainsaw. [Figure 19]1 is a diagram of an exemplary mechanism for controlling the movement of a chainsaw. [Figure 20A] 1 illustrates an exemplary embodiment of a chainsaw with the saw blade in a horizontal position. FIG. [Figure 20B] FIG. 20B shows the chainsaw of FIG. 20A with the saw blade in a vertical position. [Figure 20C] FIG. 20B is a plan view of the chainsaw of FIG. 20A. [Figure 20D] FIG. 20B shows the chainsaw of FIG. 20A with the saw blade rotated slightly to the right. [Figure 20E] 20B shows the chainsaw of FIG. 20A with the saw blade rotated slightly to the left. FIG. [Figure 21] FIG. 1 is a partial view of a chainsaw link after a metal injection molding step. [Figure 22A] 22 shows a first lateral side of the chainsaw link of FIG. 21. FIG. [Figure 22B] 22 shows a second lateral side of the chainsaw link of FIG. 21. FIG. [Figure 23] 22 shows an example cutting edge of the chainsaw link of FIG. 21 after a grinding step. [Figure 24] FIG. 1 illustrates an example of a robotic system for surgical use having arms coupled to bones of a patient. [Figure 25] FIG. 10 illustrates another embodiment of a robotic system for surgical use having multiple arms coupled to a patient's bones. [Figure 26] 1 is a flow diagram of an exemplary method for automatic control of a saw. DETAILED DESCRIPTION OF THE INVENTION

[0037] The accompanying drawings can be better understood with reference to the following detailed description.

[0038] For the purposes of promoting an understanding of the principles of the present disclosure, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe these and other embodiments. Nevertheless, it will be understood that the scope of the invention as defined in the claims is not intended to be limited by the embodiments shown in the drawings or described herein. Any variations and further modifications of the systems, devices, components, or methods shown or described, and any further applications of the principles of the invention, as would normally occur to one skilled in the art to which the invention pertains, are fully contemplated. In particular, features, components, and / or steps described with respect to one embodiment of the invention may be combined with features, components, and / or steps described with respect to other embodiments of the invention.

[0039] The designators "first" and "second," as used herein, do not designate or imply any particular positioning or other characteristics. Rather, when used herein, the designators "first" and "second" are used solely to distinguish one component or part from another. The terms "attached," "coupled," "connected," and the like, unless direct or indirect attachment, connection, coupling, etc., are used to refer to the attachment, connection, coupling, etc. of one item to another item, either directly or indirectly, by one or more other items. The term "user" refers to one or more people who use the devices, systems, and / or methods described herein, e.g., one or more surgeons, physicians, operators, or other persons who use the devices, systems, and / or methods.

[0040] 1 shows a first exemplary embodiment of a chainsaw cartridge 10 suitable for cutting bone or other tissue in a surgical procedure or procedure, such as knee surgery, spinal surgery, and other potential bone or tissue cutting applications. The chainsaw cartridge 10 of FIG. 1 includes a saw bar 20, a plurality of links 40 assembled together into a cutting chain around the bar 20, and a drive cog assembly 70.

[0041] Figure 2 shows a single link 40 for a cutting chain of a chainsaw, such as the cutting chain of the chainsaw cartridge 10 of Figure 1. Link 40 has a top or cutting side 41, a bottom or bar side 42, a first adjacent link side 43, a second adjacent link side 44, a first lateral side 45, and a second lateral side 46.

[0042] Link 40 has a hook 50 and a recess 52. Link 40 has a rounded feature or protrusion 54 that forms one side of recess 52. In this exemplary embodiment, hook 50 extends outward from second adjacent link side 44 and upward from bottom side 42, and rounded protrusion 54 extends downward from top side 41 and inward from first adjacent link side 43. Recess 52 extends upward from bottom side 42 and is shaped to receive hook 50 of an adjacent link 40.

[0043] As shown in FIG. 1 , multiple links 40 can be connected together to form a chain that can move along a predetermined path around bar 20. The recess 52 of one link receives the hook 50 of an adjacent link, causing the hook 50 to fit into the recess 52. The hook 50 of one link then interlocks with the lobe 54 of the adjacent link. When two adjacent links are aligned or in a non-articulating configuration, such as along straight portion A of bar 20, a gap is left between the tip 51 of the hook 50 and the end 53 of the recess 52, allowing articulation. When two adjacent links are articulated together along a convex path, such as along convexly curved portion B of bar 20, the articulation causes the hook 50 to fit further into the recess 52, and the distance between the tip 51 of the hook 50 and the end 53 of the recess 52 is shorter than the distance along straight portion A. In some embodiments, at full articulation, i.e., maximum pivot between adjacent links, tip 51 of hook 50 is at its closest point to end 53 of recess 52, and in some embodiments may even touch end 53 of recess 52.

[0044] The configuration of the links 40 with the hooks 50 and corresponding recesses 52 allows the links 40 to rotate relative to one another and remain connected to one another even as they rotate away from one another along a convexly curved path. The links 40 remain interconnected, thereby avoiding longitudinal disarticulation without the need for separate connecting elements, such as rivets, pins, or other connectors. Thus, the width of the chain is as small as the width of the cutting links 40, thereby enabling a thin chain to be achieved for a thin cut edge.

[0045] 2, bottom side 42 of link 40 has a drive cog engagement recess 68. Drive cog engagement recess 68 is for allowing engagement by drive cog 72, as described in more detail below.

[0046] Link 40 has a plurality of blade teeth 60 at its top or cutting side 41. In the illustrated embodiment, each blade tooth 60 is pyramidal in shape, tapering from a relatively wide base 60B to a sharp or relatively sharp peak or apex 60A. The illustrated teeth are arranged in two parallel rows, each extending along a lateral side of top side 41 of link 40. Teeth 61, 63, and 65 are arranged along a first lateral side, and teeth 62 and 64 are arranged along a second lateral side.

[0047] FIG. 3 is a schematic diagram of the layout of blade teeth 60 of link 40, showing bases 61B, 62B, 63B, 64B, and 65B of teeth 61, 62, 63, 64, and 65, respectively, in solid lines. Bases 62B, 63B, and 64B of teeth 62, 63, and 64 are triangular and have a first size. Bases 61B and 65B of teeth 61 and 65 are triangular and have a second size that is approximately half (including half) of the first size. Each of teeth 61, 62, 63, 64, and 65 is in the shape of an oblique pyramid, with the peak or apex of the pyramid located approximately above points 61A, 62A, 63A, 64A, and 65A, respectively. One side of each oblique pyramid is approximately flush with a lateral side of link 40. That is, each of teeth 61, 63, 65 has a side that is generally flush with first lateral side 45 of link 40, and each of teeth 62, 64 has a side that is generally flush with second lateral side 46 of link 40. In the illustrated embodiment, the peaks of pyramidal teeth 61, 63, 65 located generally above locations 61A, 63A, 65A, respectively, are aligned with first lateral side 45 of link 40, and the peaks of pyramidal teeth 62, 64 located generally above locations 62A, 64A, respectively, are aligned with second lateral side 46 of link 40.

[0048] When a link 40 is arranged in a chain with similar links 40, tooth 61 lies adjacent to tooth 65 (shown in dotted lines) of its adjacent link, and the adjacent teeth 61, 65 together form a tooth profile that is substantially the same as that of tooth 63. Similarly, when a link 40 is arranged in a chain with similar links 40, tooth 65 lies adjacent to tooth 61 (shown in dotted lines) of its adjacent link, and the adjacent teeth 65, 61 together form a tooth profile that is substantially the same as that of tooth 63. In other words, tooth 61 and its adjacent tooth 65 together form a tooth that is substantially equivalent in size and shape to tooth 63. Thus, when arranged in a chain of links, the chain has two rows of teeth, with teeth 62, 64 alternating along one lateral side 46 and teeth 63, 61, 65 alternating along the other lateral side 45.

[0049] One result of this configuration is that tooth crests are located on each side of the cutting surface, with valleys between the crests. The teeth on opposite sides are staggered so that the crests on one side line up with the valleys between the crests on the opposite side. This reduces the time between cutting impacts, thereby minimizing vibration while allowing room for bone debris removal. The shape and placement of the teeth also promotes centering of the chain as the teeth are making the cut. That is, the geometry and placement of the teeth result in self-centering of the links.

[0050] The link 40 can have approximately the same width as the saw bar. In such a case, in a configuration where there are some pyramidal teeth with sides flush with the first lateral side 45 of the link 40 and some pyramidal teeth with sides flush with the second lateral side 46 of the link 40, the lateral sides of the link (including the teeth) and the bar are continuous and relatively smooth. This helps to create bone cuts with smooth surfaces.

[0051] The cutting width of the link needs to be equal to or greater than the width of the bar to prevent the saw from getting stuck. For the chainsaw to cut through bone, the width of the cut made by the chain must be equal to or greater than the width of the bar. If the bar is wider than the cut, it will extend beyond the cut and get stuck in the bone. In some embodiments, such as the examples shown in Figures 2 and 3, the pyramids or cutting elements are located on the sides of the links and do not extend laterally beyond the width of the saw bar. In other embodiments, the pyramids or cutting elements may extend laterally down the sides of the links and / or beyond the width of the saw bar.

[0052] The blade teeth can have other shapes and arrangements. The teeth can be shaped as other types of cones, with a pyramidal shape being one example of a cone. A pyramidal shape is a cone with a polygonal base. In the illustrated embodiment, the base of the cone or pyramid is triangular, but other base shapes with four, five, six, seven, or more sides can be used. The polygon can have any suitable angle between its sides. For example, if a triangular base is used, the triangle can have angles that are acute, 90 degrees, or obtuse. Exemplary triangles have 90-degree, 45-degree, and 45-degree angles at their corners, or 60-degree angles at each corner, or other suitable angular arrangements. Other shapes the teeth can have include cones with circular, elliptical, or irregularly shaped bases. The cone can be a right circular cone or an oblique circular cone. For example, teeth shaped as pyramids can be right or oblique pyramids. The edges, apexes, or corners of the teeth can be pointed or rounded. The apexes can be vertically oriented or angled or curved inward and / or outward. Other shapes the teeth can have include those with concave shapes that provide cutting edges (like a spoon with a sharp edge) designed to scrape away material. For example, such designs can be used to scrape away chunks of soft tissue, such as when resecting a cartilaginous disc between vertebrae. A single link or chain can have a mixture of different sizes, heights, and shapes of blade teeth, including any of the teeth described above.

[0053] The tooth configurations described above, such as those shown in Figures 2 and 3, orient the cutting edges of the teeth toward the bone or other tissue to be cut, such that the teeth act as cutting blades that facilitate slicing of the bone or tissue. This slicing function contrasts with the scraping action of traditional chisel-type teeth. Furthermore, the placement of the teeth with surfaces that are substantially flush with the lateral sides of the link facilitates achieving cuts that are relatively flat and relatively smooth-sided. Additionally, the tooth configuration helps prevent clogging by fibrous tissue.

[0054] By arranging the blade teeth along the lateral sides of the links with valleys between them, room is provided for the removal of bone or other debris within the valleys between the blade teeth. The valleys can also be used to deliver fluids, such as sterile saline or other fluids used for cooling or irrigation. The valleys can also provide channels for delivering drugs, such as drugs to reduce bleeding, prevent infection, or block other negative cellular responses. The valleys can also be used to deliver non-liquid or slurry-like products, such as human growth hormone, calcium, bone substitutes, collagen, etc., to facilitate delivery in very narrow areas or large volumes. The chain motion can also act as a conveyor for transporting materials. The chainsaw described above, with valleys or channels between the blade teeth, can also be used to harvest or harvest bone, for example, from the pelvic region of the iliac crest for use as autograft material for patients, commonly used in spinal surgery. The bone is harvested by the blade teeth and transported from the patient through the valleys between the blade teeth.

[0055] In some embodiments, it may be desirable to provide one or more cutting elements along the side, in the center of the link between the lateral rows of cutting elements. This may be desirable for cutting between the lateral rows. Thus, in some embodiments, one or more links may have one or more central cutting elements, such as one or more chisel-type teeth or squared teeth. Such one or more cutting elements need not be provided for every link. For example, half or a few, or even just one link in a chain may have such one or more cutting elements.

[0056] FIG. 4A illustrates a saw bar 21 that can be used with the chainsaw cartridge 10. The saw bar 20 of FIG. 1 and the saw bar 21 of FIG. 4A are substantially identical, except for a different hole 23 for securing the bar 21 to a suspension system attached to the drive head of the chainsaw. The saw bars 20 and 21 are generally flat, with the main body 22 contributing the bar's primary strength and stability, and the links capable of transmitting normal loads associated with downward cutting pressure, i.e., loads directed perpendicular to the chain path and toward the saw bar. The bar has two longitudinal sides 24 and 26 and a distal end 25 that, in the embodiment of FIG. 4A, is curved or semicircular. The bar has a recess at its proximal end 27 that receives the drive cog. The sides 24 and 26 have extensions 28 that facilitate the transfer of continuous-link chain from the bar to the drive cog and from the drive cog to the bar. The first longitudinal side 24 , the second longitudinal side 26 , and the distal end 25 define at least a portion of a chain path P around the sawbar 21 .

[0057] The burrs 20, 21 can have a variety of other configurations. For example, the distal end 25 can be symmetrical and semicircular, as shown in FIG. 4A, or can have other shapes. In one variation, as shown in FIG. 4B, the distal end 25A can be asymmetrical, providing a beveled face with a rounded end that protrudes more on one side of the saw than the other. The beveled face can be relatively straight and angled relative to the longitudinal axis of the saw, such that one longitudinal side of the saw is longer than the other, and the beveled face can have a rounded end that transitions to the longitudinal side. Such a distal tip can be desirable in some procedures to resist lateral forces created by a moving chain linearly approaching a portion of bone.

[0058] Figure 5A is an enlarged view of first side 24 of bar 21 at proximal end 27 of bar 21, showing with a partial cutaway a portion of a chain of links 40 assembled to bar 21. Figure 5B is an enlarged end view of bar 21 at distal end 25 of bar 21, showing a single link 40 for illustrative purposes. Figure 5C is an enlarged view of a portion of Figure 5B.

[0059] As shown in Figures 5A, 5B, and 5C, the bar 21 has a rail 30 extending from the body 22 of the bar 21. The rail 30 extends entirely or partially along the sides 24, 26 and distal end 25 of the bar 21. The rail 30 acts as a monorail along which the links 40 of the chain travel. The rail 30 extends generally away from the body 22 of the bar 21. The rail 30 has a protrusion 32 extending laterally beyond one or both sides of the rail 30. The protrusion 32 acts as a link lock or retaining element that prevents the links 40 from disengaging from the rail 30 in a direction away from the bar, i.e., away from the bar generally perpendicular to the direction of chain travel.

[0060] Grooves are provided between the links 40 so that the links 40 fit over and straddle the monorail 30. As shown in FIG. 2 , the illustrated link 40 has a groove 55 extending partially upward from the bottom side 42 of the link 40 toward the top side 41 of the link 40. The top end of the groove 55 is designated as top end 56. The groove 55 is located between and extends parallel to the first and second lateral sides 45 and 46 of the link 40. The groove 55 extends from the first adjacent link side 43, through the lobe 54, through the link body 47 and the second adjacent link side 44, and through the hook 50 along the longitudinal length of the link 40. The groove 55 has a notch 57 that extends laterally beyond one or both sides of the groove 55. The notch 57 is shaped to receive the protrusion 32 of the rail 30 .

[0061] As shown in FIG. 5C , the grooves 55 and notches 57 in the links 40 receive the rails 30 and protrusions 32 of the bars 20, 21, allowing the links 40 to travel around the bars 20, 21 while preventing the links 40 from disengaging from the rails 30 in a direction away from the bars 20, 21. In the illustrated embodiment, when the links 40 are assembled to the rails 30, a gap exists between the top of the rails 30 and the top end 56 of the grooves 55. Additionally, in this embodiment, a gap exists between the bottom of the notches 57 and the bottom of the protrusions 32. This allows for some slight movement or play of the links 40 in a direction away from the bars 20, 21, perpendicular to the direction of travel of the chain around the bars 20, 21. Also, in this embodiment, the width of the grooves 55 is slightly wider than the width of the rails 30. This allows for some slight movement or play of the link 40 in the direction transverse to the bars 20,21, while the rails 30 and grooves 55 prevent unwanted excessive movement of the link 40 in the direction transverse to the bars 20,21.

[0062] Also, as a result of the gap between the rail 30 and the groove 55, vertical loads from the links 40, i.e., loads perpendicular to the chain path directed at the sawbar, are absorbed by the body of the sawbar as opposed to the rail 30 itself. Vertical forces from the cutting pyramids of the links 40 are transferred directly from the links 40 to the sawbar skids or ledges 33 on each side of the rail 30. The rail 30 itself is not subjected to these vertical forces. This configuration tends to push the links 40 into position, while the rail 30 provides resistance to lateral movement or rocking of the links.

[0063] In other words, the ledge 33 is the primary support for the vertical downward load from the link. The tangent plane portions at the bottom of the link 40, i.e., the bottom of the hook 50 and the tangent plane portions at the protrusion 54, contact the ledge 33 on each side of the rail 30. Due to the presence of the groove 56, the link 40 straddles the rail 30, with one side of the link 40 contacting the ledge 33 on one side of the rail 30 and the other side of the link 40 contacting the ledge 33 on the other side of the rail 30. The separation between the contact point between the right side of the link and the ledge and the contact point between the left side of the link and the ledge provides inherent stability and planar control of the link relative to the bar. The ledge 33 receives the downward force from the link 40, thereby stabilizing the link 40 and keeping it flush with the plane of the bar. This helps ensure that the lateral sides of the link 40 remain substantially flush with the sides of the bars 20,21.

[0064] The protrusions 32 and notches 57 may have any suitable shape that allows the link 40 to travel around the bars 20, 21 while preventing the link 40 from disengaging from the rail 30 in a direction away from the bars 20, 21. For example, the protrusions 32 may have a circular, oval, polygonal, or irregular cross-sectional shape, and the notches 57 may have any suitable shape that receives the protrusions 32 while keeping the link 40 riding on the rail 30. The protrusions may be symmetrical or asymmetrical and may extend from one or both sides, and the notches may likewise be symmetrical or asymmetrical and may extend from one or both sides.

[0065] In an alternative embodiment, rail 30 has a notch (similar to notch 57) and groove 56 on link 40 has a protrusion (similar to protrusion 57) that fits into the notch. This alternative configuration (with the protrusion and notch swapped) provides the same link locking or retention element described above, thereby preventing link 40 from disengaging from rail 30 in a direction away from the bar. The link locking feature, i.e., protrusion or notch, on the saw bar may extend around the entire saw bar or may extend over only a portion or portions of the saw bar.

[0066] To attach the chain to the sawbar, the links can be joined together. The end of the chain can then be placed over the end of the rail 30 with the notch 57 in the end link 40 positioned around the protrusion 32. The chain can then be guided toward and onto the rail 30, and around the sawbars 20, 21 and along the rail 30. The chain can also fit around the drive cog 72, which applies tension to the chain.

[0067] Figure 6A is an exploded view of drive cog assembly 70 of the chainsaw of the present invention. Figure 6B is a side perspective view of drive cog assembly 70. Figure 6C is a top perspective view of drive cog assembly 70.

[0068] Drive cog assembly 70 includes a drive cog 72 with a series of drive cog teeth 73 disposed about the periphery of drive cog 72. In operation, the chain of links 40 travels around bars 20, 21 and drive cog 72, as shown in FIG. 1. The drive cog teeth 73 engage with drive cog engagement recesses 68 in links 40. When chainsaw cartridge 10 is attached to the drive mechanism, the drive mechanism rotates drive cog 72, which in turn moves the chain of links around bars 20, 21 due to engagement of drive cog 72 with links 40.

[0069] In the illustrated embodiment, the drive cog assembly 70 includes a body 74 having a plate or disk 75 and a central post 76. The central post 76 has a contoured hole or recess 77 having a hexagonal or other shaped cross-section to receive the drive element. For example, the hole or recess 77 can mate with gearing of a power adapter. The drive cog assembly 70 further includes a drive cog 72 and a cap 78. The drive cog 72 can be manufactured as a unit with the plate 75 or as a separate part that is assembled to the plate 75. For example, the drive cog 72 can have a central bore sized to receive the post 76, such that the drive cog 72 fits over the post 76, e.g., by a press fit, to position the drive cog 72 relative to the plate 75. The cap 78 can also have a central bore sized to receive the post 76, such that the cap fits over the post 76, e.g., by a press fit, to position the drive cog 72 relative to the plate 75. One or more of the components of drive cog assembly 70 may be attached to one another by laser welding or another suitable process.

[0070] In an embodiment, the chainsaw cartridge 10 is assembled by assembling the chain of links 40 around the bars 20, 21 and the drive cog 72. The components of the chainsaw cartridge 10 may be locked together by joining the cap 78 to the remainder of the drive cog assembly 70. Once the chainsaw cartridge 10 is assembled, the components of the chainsaw cartridge 10 do not separate due to their interlocking and overlapping assembly and configuration. Thus, the chainsaw cartridge 10 does not naturally fall apart. The chainsaw cartridge 10 may be a disposable item that is packaged in a sterile condition and sold separately from the power equipment used to drive the chain of the chainsaw. For example, the chainsaw cartridge 10 may be supplied as a one-piece assembly that can be attached to a chainsaw drive head, such as the chainsaw drive head 12 of FIG. 10, as further described below.

[0071] The chainsaw may include a mechanism for determining the position of the chain around the bar. For example, the profiled hole or recess 77 that receives the drive element may be a single position key, so that the drive element fits in only one position. Thus, the position of the drive element relative to the drive cog 72 and thus the position of the chain on the link 40 may be known. Additionally or alternatively, the drive cog assembly or other portion of the chainsaw may include a position indicator, such as a mechanical, magnetic, or optical encoder or a Hall Effect mechanism, that provides feedback to the drive unit. Such feedback provides an operator or computer-operated controller with information regarding the rotation and / or positioning of the tooth run. In an exemplary embodiment, the chainsaw may have several segments of multiple teeth designed for specific purposes. For example, the chainsaw may have a segment with a significantly smaller, less aggressive cutting feature compared to the rest of the chain. By knowing the position of the chain, the operator or computer-operated controller can selectively position the tooth segments as desired. For example, the less powerful blade teeth can be positioned distally when penetrating potentially sensitive soft tissue or other physiological tissue, such as a nerve or artery, and the chain can be activated with an oscillating motion so that the less powerful teeth remain positioned distally. The cut can be performed while these less powerful teeth slowly crush the bone. After addressing the potentially sensitive section, the chain can be activated, rotating continuously to force the bone against the more powerful tooth profile.

[0072] One potential problem with conventional chainsaws is friction, for example, between the chain and the saw blade. Friction also generates heat, which can be detrimental in surgical equipment. In some prior art saws, the blade must be irrigated, for example with saline, to reduce the heat, or the saw may only be used for a short period of time.

[0073] According to some embodiments of the present invention, an extremely hard coating may be applied to the surfaces of either the burrs 20, 21 or the links 40 where they contact one another to reduce friction. One non-limiting example is a diamond coating. A hard coating, such as a diamond coating, significantly reduces friction between the surfaces of the burrs and links. Minimizing friction in this manner reduces heat generation from sawing. This allows the saw to be used continuously for extended periods of time, thereby shortening the overall procedure time. A hard coating may also reduce wear. Additionally, a hard coating may allow chainsaw embodiments disclosed herein to operate without the need for external lubricants to facilitate cooling or lubrication of the assembly. External lubricants may be disadvantageous because these lubricants can cause contamination. Additionally, the need for bur irrigation is reduced or eliminated. Irrigation can be troublesome because it can obscure the view of the cut and can splash irrigation fluid outside the surgical field.

[0074] An unexpected finding was that such a coating can reduce friction to the point that a sprocket wheel is not necessary. Without such a coating, significant friction occurs as the chain turns around the curved distal end of the saw. To reduce this friction, a sprocket wheel may be placed at the distal end. Figure 7A shows an example of a saw bar SB1 equipped with a sprocket wheel SW. This sprocket wheel SW can rotate at the speed of the chain around the saw bar and virtually eliminates friction caused by sharp turning at the end of the saw bar.

[0075] 7B shows an example sawbar SB2 in which a hard or friction-minimizing coating, such as a diamond coating, is applied to the sawbar, thereby eliminating the need for a sprocket wheel SW. Eliminating the sprocket wheel greatly simplifies the saw, making it easier and cheaper to manufacture while still making the sawbar stronger, and greatly facilitating the production of smaller versions of the device.

[0076] As mentioned above, the hard coating that may be applied to the contact surfaces of the sawbar and / or links may be a diamond coating. Other exemplary coatings include titanium nitride and titanium alloys, as well as other materials, which may be applied by vapor deposition or other processes. Hard coatings, such as the diamond coatings or other coatings disclosed herein, may be used to coat all or any portion of the sawbar and / or links. For example, the hard coatings disclosed herein may be used to coat the cutting teeth of the links, thereby reducing friction, heat, and wear. The entire link may be coated with the hard coating, resulting in coating both the cutting teeth and the surfaces of the links that contact the sawbar.

[0077] Figure 8 illustrates additional features that can be incorporated as part of the chainsaw or chainsaw system of the present invention. Certain procedures, such as knee replacement or other orthopedic procedures, may utilize a cutting block, such as cutting block C shown in Figure 8. Cutting block C has a window D through which the saw can be guided. In use, cutting block C may be secured to the patient, such as the patient's bone, so that the saw can be guided to make cuts in the desired location. Cutting block C helps to secure the cutting position and prevent unwanted movement of the saw.

[0078] Because the chainsaw chain must pass through window D in the cutting block C, the chain (one link 40 shown in FIG. 8) may contact the inside left or right side of the cutting block window D, which may cause damage to and debris from both the link / chain and the cutting block C. Additionally, because the chainsaw chain must pass through window D in the cutting block C, the width of window D needs to be greater than the width of the chain. However, this creates the same problems of undesirable chainsaw movement and the link / chain may contact the top or bottom of the cutting block window D, which may cause damage and debris.

[0079] According to the embodiment of Figure 8, the chainsaw has guide posts 91, 92 spaced from the chain on the longitudinal sides 24, 26 (sometimes referred to as top and bottom) of the sawbar 21 as shown and extending forward on each side of the sawbar 21. These stabilizing guide posts 91, 92 are rigidly secured at their proximal ends (not shown) to the same mechanism as the chainsaw cartridge 10, e.g., the drive head of the chainsaw, so that the guide posts 91, 92 are in a fixed position relative to the sawbar 21 and move together with it as a rigid assembly. That is, the guide posts 91, 92 are held a fixed distance from the sawbar 21 on each side of the sawbar 21.

[0080] Guide posts 91, 92 are provided on each side of the saw bar 21, which prevent the chain from contacting the left or right inside sides of the cutting block window D. In addition, the guide posts 91, 92 are slightly thicker than the chainsaw. As such, the guide posts 91, 92 come into contact with the top and bottom walls of the cutting block window D. This prevents undesired angular movement of the saw bar 21 and maintains the saw in a proper spaced position from the top and bottom surfaces of the window D. Thus, contact between the moving chain and the window surfaces is avoided.

[0081] Each of the guide posts 91, 92 is retractable along its longitudinal axis to prevent the guide posts 91, 92 from extending significantly beyond the distal side of the window D. Specifically, the guide posts 91, 92 may be comprised of telescoping sections, with stops 93, 94 provided on the distal sections. When the stops 93, 94 contact the entrance to the window D, they prevent further advancement. As the sawbar 21 continues to be advanced through the window D, the distal sections of the guide posts 91, 92 are prevented from advancing by the stops 93, 94, and the guide posts 91, 92 shorten as the proximal sections of the guide posts 91, 92 telescope into (or vice versa) the distal sections of the guide posts 91, 92. The guide posts 91, 92 may be manufactured with sufficient strength to avoid bending, particularly at their fixed bases. It is advantageous to prevent the guide posts 91, 92 from extending significantly beyond the distal sides of the window D in order to prevent the guide posts 91, 92 from blocking the chainsaw from cutting laterally or to prevent the guide posts 91, 92 from blocking the advancement or other positioning of the chainsaw.

[0082] 9A and 9B show another embodiment for the cutting guide or block C. The chainsaw includes a cover 95 that acts laterally as a block but also passes above and below the saw bar to protect all four sides of the window D from direct contact. In some embodiments, the cover 95 may be reinforced by connections on its upper and lower surfaces that pass through slots 29 in the saw bar. Like the guide posts 91 and 92, the cover 95 may be retractable, with the distal part 96 telescoping into the proximal part 97, or vice versa. The distal part 96 of the cover 95 may have one or more stops to prevent distal movement beyond a desired point, at which point further advancement of the saw shortens the cover 95 by telescoping the distal and proximal parts 96 and 97, as shown in FIG. 9B.

[0083] 9C and 9D show another embodiment for cutting block C. In this embodiment, the cutting elements 98 of the saw links retract or rotate inward when they are positioned within window D, as shown in FIG. 9C. Once the cutting elements 98 pass through window D, they can expand outward, as shown in FIG. 9D. The outward movement may occur automatically by spring action or due to contact with bone.

[0084] 9E shows another embodiment for cutting block C. In this embodiment, the chainsaw bar has cambered sides 80. The cambered sides 80 of the saw bar prevent the cutting element 81 from contacting the inside surface of the window D of the cutting block C. The body of the saw bar is located near the inside surface of the window D at the cambered sides 80, which keeps the saw in a stable position with minimal pitching within the window D and prevents the cutting element 81 from contacting the inside surface of the window D.

[0085] In certain variations, the saw bar may be manufactured to fit into the window D, for example, with a press fit, clearance fit, or slip fit. Some clearance around the saw bar allows the links to pitch at a small angle. One embodiment is to provide an interference fit between the height of the guide opening and the width of the saw. At the same time, friction must be minimized as the saw passes through the guide. The bar may also be spring-loaded or covered with a deformation layer so that the bar is stabilized within the window D but still able to move. The bar may be covered with a sheath that does not extend beyond the cutting block C. The links may be covered with titanium nitride or a similar material to minimize resulting wear or debris when the links (e.g., stainless steel links) contact the cutting block C.

[0086] The guide posts 91, 92, covers 95, or other similar longitudinal sliders or stabilizing guards may be computer-controlled or remotely controlled, for example, by pneumatic, electromechanical, or other actuators. The posts, covers, sliders, or guards may be equipped with a feedback system so that a computer or operator knows their position. They may also have fiber optics or a fiber optic camera to aid in visualization. This is facilitated by the reduced vibration of the chainsaw embodiments disclosed herein, compared to the high vibrations experienced with sagittal plane saws, which make visualization through such components difficult or impossible. The posts, covers, sliders, or guards may also be used to coordinate cleaning and maintain a clear view.

[0087] The protective element, such as the post, cover, slider, or guard described above, prevents the rotating chain and saw bar from contacting the walls of the slot in the cutting block or guide while maintaining the guiding function of the slot. Thus, the protective element aids in alignment of the chainsaw while preventing unwanted movement of the chainsaw or unwanted contact between the chainsaw and the cut or guide.

[0088] Figure 10 shows an example chainsaw, illustrating the attachment of a chainsaw drive head 12 to a chainsaw cartridge 10. The saw bars 20, 21 are attached to the drive head 12 by fasteners passing through holes 23 (see Figure 4A) for a suspension system. The drive head 12 has a drive rotor that is rotated by a motor and engages a drive recess 77 in the drive cog assembly 70 to drive the chainsaw chain.

[0089] The chainsaw may have various components that drive the chain of the chainsaw. The chainsaw may have a motor, such as a DC or AC motor, or an engine, that generates power. The chainsaw may also have a drive mechanism that transfers power from the motor or engine to the chain. The chain may be controllable with variable speed and torque.

[0090] The chainsaws and / or chainsaw components described herein have advantages over certain prior art chainsaws and components. One problem common to most prior art chainsaws is the stability of the chain and its links as it moves along the bar and when it is subjected to forces during cutting. The chain moves at high speed along guides at the boundaries of the bar. During cutting, upon interaction with an object, the chain experiences forces that encourage movement of the links out of their normal positions. In part, this is due to the shape of the cutting elements, which often have cutting edges at the top and sides, as shown in FIG. 11A, which shows a link from a typical prior art chainsaw. The two cutting edges create varying forces that tend to move the links as they move along the bar guide G, shown in FIG. 11B. FIG. 11B is a cross-sectional view of a prior art link in a normal position, FIG. 11C is a cross-sectional view of a prior art link in a laterally offset position, FIG. 11D is a cross-sectional view of a prior art link in a tilted position, FIG. 11E is a side view of a prior art link, and FIG. 11F is a top view of a prior art link. The two cutting edges of the link create various forces that tend to cause the link to move laterally as shown in FIG. 11C, tilt as shown in FIG. 11D, pitch as shown by the arrows in FIG. 11E, and / or rotate as shown by the arrows in FIG. 11F. In addition, the cutting elements of a series of links often point in opposite directions. These movements place significant stresses on the connections between the links and on the mechanical interaction between the links and the guide G. These stresses can cause component failure. Therefore, such components must be made relatively large and bulky, making this prior art design impractical for surgical use.

[0091] One advantage of certain embodiments of the links described herein, such as the link shown in FIG. 2, is that the cutting elements are designed to exert a force primarily in the same plane as the saw bar. This results in a single force vector that primarily pushes the link toward the bar, allowing the bar to withstand a normal force. For simplicity, this vector is referred to as normal because it is perpendicular to the chain path and pointed toward the bar. This avoids the eccentric forces that act on the links of most prior art chainsaws, resulting in less stress on the chain elements, allowing the chain design to be optimized for other aspects of the cutting process while minimizing chain breakage, resulting in less vibration and increased control over the chainsaw cut by humans and robots.

[0092] Figures 12A-12D show cutting element profiles that may limit cutting element forces exerted primarily in the same plane as the bar. Figure 12D is a schematic diagram similar to blade tooth 60 of Figure 2. The shape and positioning of the cutting elements balances the lateral forces, leaving a net normal force vector perpendicular to the bar. In Figure 12A, conical, e.g., pyramidal, cutting elements are positioned on three sides of the link: the top side and two lateral sides. Again, the lateral forces are balanced, leaving a net normal force vector perpendicular to the bar. In Figure 12B, the link itself has an apex with two inclined surfaces, and conical, e.g., pyramidal, cutting elements are positioned on the two inclined surfaces at the apex of the link. As in Figure 12A, the lateral forces are balanced, leaving a net normal force vector perpendicular to the bar. In Figure 12C, a series of conical, e.g., pyramidal, cutting elements are positioned on the apex of the link. As in Figures 12A and 12B, the lateral forces are balanced, leaving a net normal force vector perpendicular to the bar. In Figure 12D, as in Figure 2, a series of conical, e.g., pyramidal, cutting elements are positioned on top of the links, with one row of cutting elements along one lateral side of the link and another row of cutting elements along the other lateral side of the link. As in Figures 12A-12C, the lateral forces are balanced, leaving a net normal force vector perpendicular to the bar.

[0093] Another advantage of links such as that shown in Figure 2 and various other links described herein is that the shape of the perpendicular cutting element improves cutting and surgical outcomes. Such a shape allows for straight cuts, facilitates removal of bone debris, and allows for reduced chain speeds, which minimizes friction and tissue damage. Such a shape also allows for cutting in both directions of chain movement.

[0094] In the example of FIG. 2 and various other embodiments described above, the cutting elements are pyramidal in shape. The pyramidal elements have peaks that can cut bone and valleys that can remove bone debris. The peaks are located relatively close together, so that during cutting, the bone is subjected to small cutting element impacts at short time intervals, thereby minimizing vibration. In contrast, long time intervals between cutting element impacts can cause a sudden increase in impact force, resulting in saw vibration.

[0095] Another factor that contributes to vibration is the shape of the cutting element. The cutting elements of wood-cutting chainsaws have sharp, chisel-shaped cutting edges. These cutting elements remove a single piece of material. These chisel-shaped cutting elements, as in wood-cutting saws, deliver a stronger impact to the bone than thin, pyramidal teeth as disclosed herein. Additionally, the sharp point tips of the pyramids disclosed herein quickly catch or pin the bone, even when approached at an angle. In contrast, many other saw designs often jump to different spots when first striking the bone.

[0096] Most chainsaws rotate in one direction and have their cutting elements oriented in that direction. Chain movement in the direction of the cutting edge is required, while movement in the opposite direction will not cut. One reason is that cutting some materials, such as wood, requires a relatively complex cutting configuration with many components. When cutting a fallen tree from the top, only the bottom of the chainsaw bar can be used. Then, when using the chainsaw to cut the underside of a log, the saw must be flipped over so that the original bottom of the bar faces up. Cutting the underside of a log can be dangerous because most saws are designed to be held in one ergonomic position.

[0097] In bone surgery, it is an advantage to be able to cut in both directions. In some embodiments disclosed herein, such as the embodiment shown in FIG. 2, the cutting surface has symmetrical elements, allowing for similar cutting action when the chain is moving in either direction. In this case, the cutting effect is the same in both directions of chain movement. In alternative embodiments, the cutting elements may have cutting surfaces in both directions, but may be asymmetrical, with one side having a stronger configuration than the other. For example, the blade teeth may be pyramidal in shape, with sharper cutting edges in one direction but not the other. Asymmetric blade teeth may perform different functions in opposite directions.

[0098] Cutting in both directions, or bidirectional cutting, can be useful in removing debris that can interfere with the efficiency and directional control of a bone saw. Specifically, sawing to the right favors moving the cutting blade toward the operator (clockwise), thereby efficiently clearing debris. Cutting with the chain toward the left side removes debris better when the chain is moving in a counterclockwise direction, which also clears debris toward the operator. Thus, according to certain embodiments of the present invention that facilitate bidirectional cutting, the cutting saw links can be oriented toward the operator regardless of whether the saw is cutting to the right or left. Additionally, the operator may find it easier to control the saw when the cutting force is the same on both sides. Also, when approaching sensitive tissue, it may be desirable to rotate the chain away from the operator at the cutting surface to avoid unintentionally driving the saw toward the sensitive tissue. A chainsaw with bidirectional cutting allows for desired switching of cutting direction.

[0099] Asymmetric blade teeth can be useful for cutting different types of bone or tissue. Bone hardness varies significantly in different regions. A single cutting configuration cannot effectively cut all types of bone. As an extreme example, the exterior of a long bone is made of extremely hard bone, called cortical bone. Cortical bone performs the bone's weight-bearing function. In contrast, the interior of a long bone contains bone marrow, which produces blood cells. This material, called cancellous bone, is very soft yet has a consistency similar to soft tissue. Ideally, these types of bone would be cut with a saw suited to their different qualities. Instead of two saws, a single saw disclosed herein with asymmetric blade teeth that cut differently depending on the chain direction could be used. In one direction, the links could have a stronger blade tooth surface for cutting cortical bone, for example, and in the opposite direction, the links could have a less powerful blade tooth surface for cutting cancellous bone, for example.

[0100] Additionally, the exposed surgical field around a joint often has unwanted soft tissue, such as ligament fibers, overlapping the bone cutting field. As a result, current sagittal plane sawing procedures require the surgeon to remove the saw from the surgical field and switch to a different instrument, such as scissors or a scalpel, to cut this soft tissue. This can be extremely time-consuming, especially in robotic systems where the entire system must be repositioned each time. In contrast, the chainsaws disclosed herein can orient a powerful bone-cutting element in one direction of chain movement and a less powerful soft-tissue-cutting element in the other direction.

[0101] Another problem surgeons face is the presence of arteries and nerves that rest directly on the surface of the bone. When cutting long bones for knee replacement surgery, these structures exist behind the cortical bone, very deep within the surgical field. Cutting the cortical bone in this surgical field with a powerful cutting instrument can easily penetrate the cortical bone, causing catastrophic damage. In such situations, the chainsaw disclosed herein can function as an oscillating saw. The chainsaw can be switched to an oscillating mode, which allows the chain to rapidly alternate its direction of motion, causing the chain to move back and forth rapidly over a very short distance, i.e., a very short stroke or travel distance of the chain. This results in the desired cut of the bone while avoiding the cutting of tissue that should remain intact. For example, a small hole through the posterior wall of the bone can occur, causing minimal damage to soft tissue.

[0102] The chain can be ultrasonically driven to move the chain with high frequency vibrational motion in very short strokes. High frequency motion can generate heat. For this or other embodiments, one or more temperature sensors can be embedded in the chainsaw, for example, in the saw bar.

[0103] Another advantage of certain chainsaws disclosed herein results from the interface between the saw bar and the links. One such embodiment was described above with reference to Figures 5A-5C, which show a bar 21 with rails 30 extending from the body 22 of the bar 21. As noted above, grooves 55 are provided between the links 40 so that the links 40 fit over and straddle the rails 30.

[0104] Figure 13A shows another embodiment of a bar 34 with rails 35. Links 36 have chisel-type cutting elements and grooves that allow the links 36 to fit over the rails 35 so that the links 36 straddle the rails 35. Figure 13B is a schematic diagram of the bar 34, rails 35, and links 36.

[0105] Figure 13C is another view of the embodiment shown in Figures 5A-5C. Figure 13D is a schematic diagram of bar 21, rail 30, and link 40 (protrusion 32 is not shown in Figure 13D).

[0106] In these embodiments, the increased stability is determined by how the link interfaces with the bar. By employing a novel design in which the link straddles a single rail on the saw bar, lateral displacement of the link is prevented, increasing the lateral stability of the chainsaw. These embodiments provide greater strength to the overall mechanism while offering greater design versatility.

[0107] One advantage of these embodiments is that the links are less likely to tilt or rock laterally, as opposed to saw chains in which the bar has gutters and the links move within them (e.g., FIG. 11B). Additionally, the upper link section of the saw bar can be wider (compared to saw chains in which the bar has gutters and the links move within them, e.g., see FIG. 11B), thereby increasing the area of ​​interlocking engagement between adjacent links. The increased width also allows for greater flexibility in cutting edge design. Furthermore, the monorail design increases resistance to lateral displacement and link pitching. Another advantage is that this design simplifies the bar and reduces the stresses it experiences. This allows the bar to be constructed from a variety of materials, including extremely hard plastics such as Corian® or other plastics. As a result, the bar can be manufactured very cost-effectively, for example, by injection molding. Some materials made possible by the bar design, such as certain plastics, increase lubricity, thereby reducing friction.

[0108] In other embodiments, the bar can be made of a dielectric material and the chain can be electrified for use as an electrocautery system. Such a chainsaw system can be used to cauterize blood vessels, which helps prevent excessive blood loss.

[0109] For example, in the embodiment shown in Figure 13D, due to the gap between the rail 30 and the groove 55, the vertical load from the link 40 is transferred directly from the link 40 to the skids or ledges 33 of the sawbar 21 on each side of the rail 30. Thus, the vertical force from the link 40 is absorbed by the body of the sawbar 21, and not by the rail 30 itself.

[0110] 13E is a schematic diagram of another embodiment of a bar 37 with a link 39. In this embodiment, the link 39 has a downwardly projecting ridge 31 that fits correspondingly into a slot 38 in the bar. The ridge 31 acts like a keel, providing stability to the link 39. As a result of the embodiment of FIG. 13E, a rigid link 39 is guided along the bar 37. In one variant, the ridge 31 may have laterally extending protrusions (such as protrusion 32) that fit complementary to laterally recessed notches (such as notch 57) in the bar 37 at the sides of the slot 38. In another variant, the walls of the slot 38 may have laterally extending protrusions (such as protrusion 32) that fit complementary to laterally recessed notches (such as notch 57) in the sides of the ridge 31. These variations (with interlocking protrusions and notches) provide a link lock or retention element similar to that described above, preventing link 39 from disengaging from bar 37 in a direction away from bar 37.

[0111] Another advantage of certain chainsaws disclosed herein is derived from the link locking mechanism, one example of which is the use of the protrusion 32 and corresponding notch 57 as described above.

[0112] In certain prior art chainsaws, if the chain breaks during cutting, the links come off the chain in individual pieces. While not presenting a significant hazard in themselves as a result of the inertia of the individual links, these pieces must be removed from the surgical field, which can be difficult if they are deep within the cut bone or soft tissue. Additionally, some pieces may fall out of the surgical field and onto the surgical drape, which can make them extremely difficult to locate.

[0113] One solution is to make the links magnetic, so that detached links can be collected with a magnet, making them easier to collect.

[0114] To prevent links from being lost in the event of chain breakage, a link locking mechanism as disclosed herein can be used. One embodiment of a link lock is the protrusion from the rail or other guide element described above that serves to hold the link. As can be seen in Figures 5A-5C, even a small protrusion will prevent the link from disengaging from the rail. The protrusion can be symmetrical or asymmetrical. The protrusion need not extend around the entire sawbar, but may be located on only some portions of the sawbar.

[0115] The retaining protrusions also provide another advantage. Typically, a chainsaw traveling at operating speed experiences forces as it passes through curves at each end of the saw bar. The typical chain profile along the long sides of the saw is not straight, but bows outward. Cutting with a typical saw tends to create a slight curve. The link locking mechanisms disclosed herein, such as protrusions 32 and corresponding notches 57, hold the chain against the bar, thereby preventing this undesirable bowing. The result is a cut with a straight lateral boundary.

[0116] The chainsaws disclosed herein may include additional elements for safety or other functionality. For example, the chainsaws disclosed herein may include a torque limiting device, such as an electronic torque limiter, via a motor or slip clutch incorporated into the drive train. In other examples, torque limiting means may be implemented by monitoring the current and therefore the power transmitted to the drive train by a friction clutch, a torque limiting device using a detent and spring-loaded pawl, or other torque limiting mechanism.

[0117] Another advantage of certain embodiments of the chainsaws disclosed herein is that the chainsaw design facilitates precision bone cuts, thereby improving, refining, or tightening the bone-to-implant fit. A precision fit better locks the implant in place, reducing the risk of displacement and promoting rapid healing. This tight fit results in better short- and long-term outcomes for the patient. For example, improved fit allows the implant to support stress more quickly. This may allow the patient to walk sooner post-operatively with less risk of damaging the implant-tissue interface. Bone growth and integration of the implant with the surrounding bone must ultimately occur. The precision fit surface achievable with the embodiments disclosed herein facilitates this healing process.

[0118] Additionally, the precision cutting enabled by the embodiments disclosed herein allows for implant indications that are not currently treatable. Certain embodiments of the present invention also facilitate more customized implantation.

[0119] Figure 14 shows an example of a precision cutting application that can be achieved with certain embodiments. Figures 14A and 14B show an exemplary shaped implant Y for a vertebra. Figure 14C shows a vertebra V with a recessed volume X with a precision stepped shape that can be achieved with certain embodiments of the present invention to receive the implant of Figures 14A and 14B. The implant Y can be manufactured with a shape that corresponds to the recessed volume X. In this example, the stepped portion of the implant Y locks the implant Y in place in the anterior-posterior direction. The shelf shape of the implant Y stabilizes the implant Y in the superior-inferior direction.

[0120] The exact space, e.g., volume X, can be created with a chainsaw, as described above. For example, a chainsaw cartridge 10 can be used to precisely cut and form such a space. In other embodiments, links or saw bars can be shaped to create this irregular space. The saw links can have a custom profile to create the appropriate corresponding recess shape for the shaped implant. For example, in a link having two rows of teeth, with the first row of teeth along a first lateral side and the second row of teeth along a second lateral side, the first row of teeth can be taller than the second row of teeth. A chain made up of such links can be used to mill a stepped shape, as in FIG. 14C, with the higher row of teeth milling the wider portion and the lower row of teeth milling the narrower portion. In a variation, the links can have teeth that are taller along the middle than along the lateral sides, and the teeth can be rounded to create convexly curved sides of the extraction space. In another variation, the links can have teeth that are taller along the lateral sides than along the middle, to create concavely curved sides of the extraction space. In another variation, FIG. 14D is a front view of a custom sawbar 99 that allows the irregular bone space of FIG. 14C to have a single stab cut. Multiple chains can be driven simultaneously around the same sawbar, one along the wide portion of the bar and one along the narrow portion of the bar. The shape of the cutting profile of the links and / or sawbar can be customized for the implant so that a single pass of the chainsaw is highly consistent, repeatable, and can create a tight fit in the implant. The cutting profile of the saw and / or links can be specifically designed to create the required shape for the implant.

[0121] Improving the fit of the implant with bone or other tissue helps improve outcomes for patients. Implants with a good fit are less likely to displace and can support stresses more quickly. Patients can regain mobility sooner with less risk of damage to the tissue-implant interface.

[0122] 15A-15E show one embodiment of a chainsaw 100 with a surgical handle 101. The chainsaw 100 may be substantially similar to the chainsaws described above. The surgical handle 101 may be attached to a saw mechanism to allow for precise linear, diagonal, or lateral movements with manual movements. The surgical handle 101 may be removably attached to the saw mechanism. In the illustrated embodiment, the surgical handle 101 protrudes laterally from the saw mechanism and includes protrusions that can be easily grasped by a user (surgeon). By grasping the handle 101, the surgeon can move the chainsaw blade laterally to the left (FIG. 15D) or right (FIG. 15E) within the plane of the blade. The chainsaw blade may be rotatable about an axis of rotation.

[0123] FIG. 16 shows a guard or protector 110 that can be attached to a chainsaw 100. The chainsaw 100 can be similar to the chainsaws described above. The guard 110 can be attached around one longitudinal side and distal end of the chainsaw, thereby protecting the chain in these areas. In an alternative embodiment, the guard can be designed to cover some of the chain path, for example, along only one longitudinal side, leaving the distal end exposed. If only a portion of the chainsaw, for example, one longitudinal side, is used for cutting, the guard 110 can prevent unwanted cuts, such as inadvertent tissue damage, from the other longitudinal side of the chainsaw. The guard 110 can be removable. The guard 110 can also be reversed to protect the other side of the saw. In the illustrated embodiment, the guard 110 has a U-shaped base at one end. Each arm of the U can be placed in a tubular restraint attached to the chainsaw. The double locking stabilizes the device. A guard 110 extends along the length of the cutting chain on one side.

[0124] Figures 17A and 17B show an exemplary embodiment of a drive train mechanism for a chainsaw 120. The chainsaw bar 121 and link 122 may be substantially similar to one or more of the chainsaw bars and links described above. The housing 123 is shown in phantom in Figures 17A and 17B to show details of the drive train mechanism.

[0125] As can be seen in Figures 17A and 17B, the drive gear 124 interfaces with the saw gear 125 at a 90-degree angle. The drive gear 124 may be driven by a suitable drive mechanism, such as the motor described above. The drive gear 124 and the saw gear 125 may be bevel gears that engage with each other. Rotation of the drive gear 124 results in rotation of the saw gear 125. In the illustrated embodiment, the axis of the drive gear 124 is aligned with the axis of the saw bar 121. In alternative embodiments, the axis of the drive gear 124 need not be aligned with the axis of the saw bar 121. For example, the axis of the drive gear 124 may be at a 90-degree angle with the axis of the saw bar 121.

[0126] The saw gear 125 is rigidly coupled to the chain drive cog 126 such that rotation of the saw gear 125 rotates the chain drive cog 126. In this embodiment, both the saw gear 125 and the chain drive cog 126 are rigidly attached to an axle 127 that extends the length of the housing 123 and rotates freely relative to the housing 123. Thus, in this embodiment, the saw gear 125 is rigidly coupled to the chain drive cog 126 by the axle 127. In other embodiments, the saw gear 125 may be directly coupled to the chain drive cog 126. The saw gear 125 and the chain drive cog 126 may rotate about fixed axles.

[0127] The chain drive cog 126 interfaces with the inner edge of the chain of the link 122 such that the cog teeth of the chain drive cog 126 interface with the drive cog engagement recesses on the chain link 122. Thus, rotation of the chain drive cog 126 causes rotation of the chain. The chain drive cog 126 may be substantially similar to the drive cog 72 described above.

[0128] 17A and 17B, one or more set screws 128 may be used to stabilize the saw bar 121. Also, a protective guard 129 may be used to cover the chain teeth on one side of the chainsaw, thereby protecting adjacent tissue from inadvertent damage. The protective guard 129 may be substantially similar to the protective guard 110 described above.

[0129] Figures 18A-18C show another embodiment of a drive train mechanism for a chainsaw 130. The chainsaw bar 131 and links 132 may be substantially similar to one or more of the chainsaw bars and links described above. A housing 133 is shown in phantom in Figures 18A-18C to show details of the drive train mechanism.

[0130] The illustrated embodiment of FIGS. 18A-18C includes a saw position drive gear 134A and a chain drive gear 134B. Each of the drive gears 134A, 134B interfaces with a saw gear 135A, 135B, respectively. Each drive gear 134A, 134B and its respective saw gear 135A, 135B may be bevel gears that engage with each other. Rotation of each drive gear 134A, 134B results in rotation of the corresponding saw gear 135A, 135B. In the illustrated embodiment, the axis of each drive gear 134A, 134B is parallel to the axis of the saw bar 131. In alternative embodiments, the axes of the drive gears 134A, 134B need not be parallel to the axis of the saw bar 131. For example, the axes of the drive gears 134A, 134B may be offset from and at a 90-degree angle relative to the axis of the saw bar 131.

[0131] The chain drive gear 134B is used to drive the chain around the saw bar and may be driven by a suitable drive mechanism, such as the motor described above. The saw gear 135B may be rigidly coupled to a chain drive cog (not shown) such that rotation of the saw gear 135B causes rotation of the chain drive cog. In one embodiment, the saw gear 135B and chain drive cog are rigidly attached to an axle 137 that extends the length of the housing 133 and rotates freely relative to the housing 133. Thus, in such an embodiment, the saw gear 135B is rigidly coupled to the chain drive cog by the axle 137. In other embodiments, the saw gear 135B may be directly coupled to the chain drive cog (the axle may or may not rotate).

[0132] The chain drive coke interfaces with the inner edge of the chain of link 132 such that the coke teeth of the chain drive coke interface with the drive coke engagement recesses on the chain link 132. Thus, rotation of the chain drive coke causes rotation of the chain. The chain drive coke may be substantially similar to the drive coke 72 described above.

[0133] A saw position drive gear 134A is used to position the saw bar and may be driven by a suitable drive mechanism, such as a motor (e.g., a stepper motor). The saw gear 135A may be rigidly coupled to the saw bar such that rotation of the saw gear 135A causes rotation of the saw bar about the axis of the axle 137. In one embodiment, the saw gear 135A and saw bar are rigidly attached to the axle 137, and the axle 137 rotates with the saw bar. In another embodiment, the saw gear 135A and saw bar rotate about the axle 137.

[0134] By controlling the saw position drive gear 134A, the user can rotate the saw bar to a desired angle about the axis of the axle 137. Thus, the drive mechanism of Figures 18A-18C can be used to drive the chain around the saw bar as well as to pivot the saw bar.

[0135] 18A-18C, a protective guard 139 may be used to cover the chain teeth on one side of the chainsaw, thereby protecting adjacent tissue from inadvertent damage. The protective guard 139 may be substantially similar to the protective guard 110 described above.

[0136] Several embodiments of the present invention described herein are useful in a variety of surgical applications. One such application is minimally invasive surgery. Currently, many surgical specialists perform minimally invasive surgery. Large incisions result in high levels of post-operative pain and morbidity. In minimally invasive surgery, surgeons operate through several small incisions. Through these incisions, surgeons pass cannulae, which are essentially tubes that are threaded into the body. By using specialized instruments through the cannulas, surgeons can perform surgery without the disadvantages of large incisions.

[0137] Another surgical technological advancement is the use of robots during surgery. Robots can operate in tight spaces with greater precision than humans. However, certain existing instruments, such as oscillating bone saws, vibrate too much to be effectively controlled by current robotic technology. As a result, orthopedic surgery, a specialty that can greatly benefit from precise bone cutting and shaping, is limited in its ability to utilize robotic technology.

[0138] Clearly, there is a need for a small bone saw that can pass through a cannula and produces little vibration. Some embodiments of the chainsaw disclosed herein can pass through relatively small cannulas, e.g., cannulas having an inner diameter of 10 mm or less, and cut bone with little vibration.

[0139] FIG. 19 is a schematic diagram of an example mechanism 140 for controlling the movement of a chainsaw. The mechanism 140 includes a robotic arm 141 that can move in any direction in a plane perpendicular to the chainsaw's longitudinal axis, as indicated by arrow 141A. The robotic arm 141 can tilt from a fixed point at its proximal end through various angles, up to large obtuse angles, as indicated by arrow 141B. The mechanism 140 can be repositioned to place the fixed point of the robotic arm 141 in any desired location. The robotic arm 141 can also rotate around its longitudinal axis through any angle, as indicated by arrow 141C. The robotic arm 141 can also extend and retract, as indicated by arrow 141D. A tubular extension 142 extends from the robotic arm 141. The tubular extension 142 is the portion of the device that enters the body. Tubular extension 142, like robotic arm 141, can rotate any angle about its longitudinal axis, as shown by arrow 142A, and the tubular extension can extend and retract, as shown by arrow 142B. Saw blade 143 can rotate up to 360 degrees about pivot axis 144 relative to tubular extension 142, as shown by arrow 143A. All of these positions and movements can be performed by computer control of the robotics. The mobility of robotic arm 141 allows for nearly unlimited saw location and angle settings, as shown in FIG. 19.

[0140] Figures 20A-20E show an exemplary embodiment of a chainsaw 150. Figure 20A shows the chainsaw 150 with the saw blade 151 in a horizontal position. Figure 20B shows the chainsaw 150 with the saw blade 151 in a vertical position. Figure 20C is a top view of the chainsaw 150. Figure 20D shows the chainsaw 150 with the saw blade 151 slightly rotated to the right. Figure 20E shows the chainsaw 150 with the saw blade 151 slightly rotated to the left.

[0141] Various methods can be used to manufacture the chainsaw links of the embodiments disclosed herein. In accordance with the present invention, a chainsaw link, such as the chainsaw link 40 shown in Figure 2, can be manufactured by the following process.

[0142] First, the link is formed into its overall shape using a metal injection molding (MIM) process. Links can be manufactured inexpensively in large quantities using MIM. In MIM, powdered metal and powdered plastic are mixed together (heated) and then injected into a mold. At this point, the molded part has the overall molded shape, but is in a "green" state that is less dense than the final product. A debinding and sintering process transforms the part into a nearly 100% dense metal component.

[0143] FIG. 21 is a partial view of a chainsaw link 40 after the metal injection molding step. While components can be molded with many fine features, creating extremely sharp edges at this stage can be difficult. As shown in FIG. 21, the leading and trailing cutting edges, as well as the top of each cutting tooth 61, 63, and 65, are rounded. In the example shown in FIG. 21, the average edge radius is between 0.002 inches (0.0508 mm) and 0.004 inches (0.1016 mm). While this less-than-razor-sharp edge may be sufficient for cutting bone, it may not be optimal for certain applications.

[0144] 22A and 22B show the first lateral side 45 and second lateral side 46 of the chainsaw link 40 after shaping but before the grinding step. Grinding converts the bulbous tip and rounded edges into ground cutting surfaces, resulting in sharp cutting edges 61, 62, 63, 64, 65.

[0145] In accordance with the present invention, after the chainsaw link is formed, a grinding step is performed. The grinding step includes double-disc grinding. Double-disc grinding allows for extremely precise surface finishes, similar to those of flat, planar surfaces. The parallelism of the lateral sides 45, 46 of the link 40 can be precisely controlled, as can the thickness of the link 40. For example, the link 40 can be ground down to a thickness (end to end) of 2 mm (0.078 inches).

[0146] Due to the unique configuration of the pyramidal teeth of the exemplary chainsaw link 40, with the cutting edges aligned with the lateral sides 45, 46 of the link 40, double disc grinding can sharpen and / or profile all necessary cutting edges. The combination of metal injection molding and tooth design, along with double disc grinding, achieves the production of links with sharp teeth at an extremely low manufacturing cost.

[0147] In dual-disc grinding, two abrasive discs are spaced apart and counter-rotate while the chainsaw links 40 are fed rotary or linearly into the space between the rotating discs. The chainsaw links 40 may be fed along a conveyor so that they pass continuously between the discs. One disc grinds the first lateral side 45 of the link 40, while the other disc grinds the second lateral side 46 of the link 40. Dual-disc grinding is a highly efficient grinding process using abrasive wheels positioned opposite each other to grind and remove equal amounts of material from both sides of the blank. The result is flat surfaces, parallel sides, and a smooth finish. In one example, this process can provide a parallelism tolerance of 0.0005 inches (0.0127 mm) and a finish of up to 16 Ra.

[0148] 23 shows the resulting sharp cutting edges and apex of the link after grinding. An exemplary cutting tooth 63 with a sharp cutting edge is shown.

[0149] Another advantage of certain embodiments of the chainsaw disclosed herein is that the chainsaw can be used in robotic surgery. Surgical robots can be of great value in orthopedic surgery because of the potential for the robot to make precise cuts regardless of the surgeon's condition or skill. Current surgical robots equipped with sagittal saws experience irregularities and inaccuracies due to the vibrations of the sagittal saw. In the embodiments disclosed herein, the reduced vibrations, reduced saw blade size, reduced cutting force, minimal deviation from the intended cutting path (no skiving), reduced inaccuracy, and / or minimal heat generation make the chainsaw particularly well-suited for use in robotic systems. This is especially true for surgical applications requiring precise bone cuts.

[0150] Additionally, sagittal plane saws are not designed to remove soft tissue (e.g., ligaments). Therefore, if soft tissue is introduced into the cutting field, the saw must be removed and the soft tissue must be manually cut using conventional surgical instruments. The bidirectional capability of some embodiments of the present invention with asymmetric cutting elements allows bone cutting in one direction and soft tissue cutting in the other direction. Thus, robotic control of the saw can continue for bone and soft tissue cutting without the need to remove the robotic saw.

[0151] The saw can be guided using a robotic control mechanism, such as a robotic control arm powered by gearing, cams, electromechanical, pneumatic, hydraulic, biochemical fluids, or any combination or permutation thereof. The robotic control scheme, in some embodiments, automatically corrects for bias in a direction opposite to the direction of travel of the links. The force required to resist the bias can be computed using a calculation of the amount of power being delivered to the saw. The resisting force can also be computed using input from other systems, such as optical systems, such as laser systems or 3D vision systems, ultrasonic systems, hall sensors, or sonar systems.

[0152] In some embodiments of the invention, the robotic system includes at least one arm that is mechanically coupled at one end to a bone of the patient, and the other end of the arm may be mechanically coupled to an instrument, a robotic arm, or a computerized robotic unit that includes a robotic arm.

[0153] The arm coupled to the patient's bone, or the robotic arm to which the arm is coupled, can carry or be configured to carry an instrument, such as a bone saw and / or a cutting guide for a bone saw. For example, the arm coupled to the patient's bone, or the robotic arm coupled to the patient's bone, can carry or be configured to carry a chainsaw as disclosed herein and / or a cutting guide for a chainsaw as disclosed herein. In some embodiments, other types of saws can be used, such as a sagittal saw. In other embodiments, the arm coupled to the patient's bone, or the robotic arm to which the arm is coupled, can carry a non-cutting instrument, including, but not limited to, a scanning probe, a temperature probe, a drug delivery system or instrument, or another instrument.

[0154] The arms of the robotic systems disclosed herein may be secured to the patient's bones by suitable support mounts that can be attached to the patient's bones. Bone support mounts, such as cutting guides, are known. Another example of a support mount that can be attached to the patient's bones is shown and described in U.S. Provisional Patent Application No. 63 / 195,994, filed June 2, 2021, entitled "Cutting Guide Systems and Methods." This U.S. Provisional Patent Application discloses a support mount suitable for attachment to, for example, the patient's tibia and / or femur.

[0155] The arm, which is fixed to the patient's bone, can be adjustable in six degrees of freedom: positioning along the x-y-z axes and rotational orientation relative to the x-y-x axes. The arm can have one or more arm segments and / or one or more joints. The joints can connect the arm segments to a support mount, to adjacent arm segments, and / or to an instrument, robotic arm, or robotic unit. The joints can have any suitable configuration that allows adjustment of the arm, thereby adjusting the positioning and / or rotational orientation of the arm relative to the bone. Exemplary joints include ball-and-socket joints, swivel joints, and hinge joints, among others.

[0156] In some embodiments, the arm coupled to the patient's bone can include a feedback system that can transmit information about its position and / or rotational orientation to a control system. For example, the joints and / or arm segments can include transducers that read information about its position and / or rotational orientation and connections (wireless or wired) that transmit such information to the control system. Thus, the device provides a telemetry stream that updates the robotic system regarding the position and rotational orientation of the bone being resected. In this manner, the position and / or rotational orientation of the bone relative to the robotic arm and / or instrument can be constantly monitored and known. The position and / or rotational orientation of the robotic arm and / or instrument can be automatically adjusted based on the bone position and / or rotational orientation determined from the feedback system.

[0157] In some embodiments, the arm coupled to the patient's bone can have one or more actuators, such as electromagnetic actuators (e.g., one or more stepper motors, servo motors, or other actuators), that move the arm to a desired position. These actuators can adjust the position and / or rotational orientation of the arm. These actuators can move the arm at high or low speeds, maintain the position of the instrument relative to the bone, and can include braking to lock the position when real-time repositioning is not required.

[0158] In embodiments in which an instrument is attached to the other end of an arm coupled to a patient's bone, the position and / or rotational orientation of the instrument can be adjusted by adjusting the position and / or rotational orientation of the arm coupled to the bone. Similarly, in embodiments in which the arm is directly attached to a robotic arm (as opposed to a floor-mounted robotic unit that includes a robotic arm), an actuator can be used to adjust the bone-coupled arm to adjust the position and / or rotational orientation of the robotic arm. This can adjust the position and / or rotational orientation of an instrument carried by the robotic arm.

[0159] In some exemplary embodiments, the arm is coupled at one end to a support mount attached to the patient's bone and at the other end to a computerized robotic unit including a robotic arm. The computerized robotic unit may be installed on the floor of the operating room. The bone-coupled arm may be substantially similar to the arm described above. As the patient's bone moves relative to the robotic unit and thus the robotic arm of the robotic unit, the arm coupled to the bone provides feedback to a control system for the robotic unit regarding the position and / or orientation of the patient's bone relative to the robotic unit and thus the robotic arm. The control system may control the robotic arm, and any instruments carried by the robotic arm, based on the position and / or orientation of the patient's bone.

[0160] In some embodiments, the arms can be attached to the patient's femur and / or the patient's tibia. Separate arms can be attached, one to the patient's femur and one to the patient's tibia, such that both arms are associated with a control system. The femoral arm and the tibial arm can be used together to provide range of motion feedback for positioning the knee joint in all planes and all axes.

[0161] In some embodiments, one or more arms described herein can be secured to a patient's bone at one or more locations. For example, in one embodiment that can be attached to a patient's femur, a first arm can be secured to the medial epicondyle and a second arm can be attached to the lateral epicondyle. The other ends of both arms can be coupled to an instrument or a robotic arm carrying the instrument. For example, the instrument or robotic arm can be attached between two bone-connecting arms. The attachment points of the bone-connecting arms to the instrument or robotic arm can create an axis about which the instrument or robotic arm can rotate. The attachment points of the bone-connecting arms to the two epicondyles can create an axis between the epicondyles about which the structure (the two bone-connecting arms and the instrument or robotic arm) can rotate. This allows the robotic arm or instrument to be positioned to achieve various desired cuts in the femur. The entire assembly can be movable by the actuators described above to move the robotic arm or instrument to various desired positions.

[0162] In some embodiments, if an instrument or a robotic arm carrying the instrument is attached directly to one or more arms attached to the patient's bone (e.g., the arms described above attached to the medial and lateral epicondyles), the instrument or robotic arm can be supported by the bone-coupled arms without the need for a floor-mounted robotic unit as used in prior art systems. These devices, in such embodiments, may be attached solely to the patient and thus can move with the patient's movements.

[0163] FIG. 24 shows one example of a robotic system 160 for surgical use having an arm 162 coupled to a patient's bone, e.g., femur F. Arm 162 may additionally or alternatively be attached to tibia T. In the illustrated embodiment, a first end of arm 162 is coupled to bone F at joint 163, thereby allowing movement in any direction and any rotational orientation. Arm 162 has a series of arm segments 164, 166, and 168. Arm segment 164 is coupled to arm segment 166 by joint 165, thereby allowing relative movement therebetween. Arm segment 166 is coupled to arm segment 168 at joint 167, thereby allowing relative movement therebetween. A second end of arm 162 is coupled to robotic arm 170 at joint 169, thereby allowing relative movement therebetween. The robotic arm 170 carries an instrument 172 (e.g., a bone saw, a bone saw guide, or other instrument). The robotic arm 170 may be part of a robotic unit 174, which may include a base unit 175 mounted on the operating room floor 176. In an alternative embodiment, the second end of the arm 162 may be directly coupled to the instrument 172 without the intermediate robotic arm 170, such that the arm 162 serves as the robotic arm that controls the positioning of the instrument 172. In another alternative embodiment, the robotic arm 170 is not part of a floor-mounted robotic unit, but is instead supported entirely by the arm 162. Thus, structure located below point 178 on the robotic arm 170 can be eliminated (the electronics of the base unit 175 may be incorporated into the robotic arm 170).

[0164] The arm 162 coupled to the patient's bone can include a feedback system that can transmit information regarding its position and / or rotational orientation to a control system of the robotic system 160. For example, the joints 163, 165, 167, 169 and / or the arm segments 164, 166, 167 can include transducers that read information regarding its position and / or rotational orientation and connections (wireless or wired) that transmit such information to the control system. The control system can use such information to adjust the position of the arm 162, the robotic arm 170, and / or the instrument 172. In some embodiments, the arm 162 coupled to the patient's bone can include one or more actuators, such as electromagnetic actuators (e.g., one or more stepper motors, servo motors, or other actuators), that move the arm 162 to a desired position.

[0165] FIG. 25 shows another embodiment of a robotic system 180 for surgical use having multiple arms 182, 184, 186, and 188 coupled to a patient's bone, e.g., femur F. The first end of each arm 182, 184, 186, and 188 is coupled to the bone at a joint 181, thereby allowing movement in any direction and any rotational orientation. Each arm 182, 184, 186, and 188 may have multiple arm segments connected to one another by one or more joints, thereby allowing relative movement between the segments. The second end of each arm 182, 184, 186, and 188 is coupled to a robotic arm 170A at a joint 183, thereby allowing relative movement between the arms. The second end of arm 188 is coupled to arm 182, which is coupled to robotic arm 170A via arm 182. The second end of arm 188 is coupled to arm 182 at joint 185, allowing relative movement between the arms. Robotic arm 170A carries instrument 172A. In the illustrated embodiment, robotic arm 170A is not part of a floor-mounted robotic unit, but instead is supported entirely by arms 182, 184, 186, and 188. In an alternative embodiment, arm 170A may be part of robotic unit 174, which may be placed on the operating room floor. In an alternative embodiment, the second ends of arms 182, 184, 186, and 188 may be directly coupled to instrument 172A, such that arms 182, 184, 186, and 188 function as robotic arms that control the positioning of instrument 172A.

[0166] The arms 182, 184, 186, 188 coupled to the patient's bones can include a feedback system that can transmit information regarding their position and / or rotational orientation to a control system of the robotic system 180. For example, the joints and / or arm segments can include transducers that read information regarding their position and / or rotational orientation and connections (wireless or wired) that transmit such information to the control system. The control system can use such information to adjust the position of the arms 182, 184, 186, 188, the robotic arm 170A, and / or the instrument 172A. In some embodiments, the arms 182, 184, 186, 188 coupled to the patient's bones can include one or more actuators, such as electromagnetic actuators (e.g., one or more stepper motors, servo motors, or other actuators), that move the arms 182, 184, 186, and / or 188 to a desired position.

[0167] Similar to arm 188 in Figure 25, robotic systems of the present invention may have arms that are connected to other arms, thereby forming a branched system between the bone and the instrument or instrument-carrying robotic arm, which may aid in instrument stability and fine positioning.

[0168] The devices disclosed herein can achieve one or more advantages. For example, certain embodiments described herein can provide more direct feedback regarding the position and / or orientation of a patient's bones (e.g., the femur and / or tibia) than currently used optical systems. Certain embodiments disclosed herein can also reduce the latency between the patient's movement and the robotic arm's response, thus providing smooth and safe control of the saw blade or other instrument. Certain embodiments disclosed herein can achieve extremely high accuracy with significantly less equipment and software, particularly because the devices disclosed herein use stereo cameras and do not require the computing power required for a stereotactic system to convert images into position and / or rotational orientation information. Certain embodiments disclosed herein can be less expensive and / or less complex than prior art systems and can occupy less space than prior art systems. Certain embodiments disclosed herein can keep the attachment and saw control very close to the structural components of the robot, thereby inherently creating its stability, precision, and reliability.

[0169] In certain embodiments, mechanical coupling of the instrument or robotic arm to the bone via the bone coupling arm (and in some embodiments, the robotic unit) provides greater stability during the procedure. In other words, in the example of knee surgery, the system can stabilize the patient's knee, which is subjected to stresses from the cutting action.

[0170] In summary, certain embodiments disclosed herein may achieve one or more advantages, such as lower cost, ease of use, fewer malfunctions, more precise incisions, shorter procedure times, shorter recovery times, and / or better outcomes.

[0171] In other variations of robotic or automated systems (with or without the bone-connecting arms described above), the saw (e.g., a chainsaw) can be coupled to a feedback system that measures one or more of the following conditions when cutting bone (e.g., cutting or other forces, rotational forces, various forces on the links, forces on the bar, forces on the drive pin, forces in the gears, vibration levels, noise pitch and magnitude, and / or deflection from an ideal plane). These measurements are then analyzed by software, thereby providing intelligent control of the saw, drive, and / or robot.

[0172] For example, bone is heterogeneous, possessing varying degrees of density, hardness, and dryness, among other properties. Saws work differently on different types of bone in terms of speed, vibration, noise (pitch and volume), and ability to hold a flat surface. A bone saw needs to be able to cut bone safely without endangering the soft tissue surrounding the bone.

[0173] As an example of using a feedback system based on measurements, a cutting system can determine whether the saw is to be used on hard bone, soft bone, or soft tissue. As the saw moves through soft cancellous bone and encounters hard cortical bone, the control system can identify the hard bone and determine whether the saw is approaching or engaging the edge of the bone within the cutting zone, beyond which is sensitive soft tissue, such as the medial cruciate ligament and, on the other side, the lateral cruciate ligament. Based on measurements and software analysis, the control system can control the saw speed to cut faster or slower and / or shift into vibration mode to protect the soft tissue. The control system can immediately stop the saw when cutting bone (recognizing that the force on the saw has dramatically decreased) before the saw injures the soft tissue.

[0174] FIG. 26 is a flow chart of an exemplary method for automatically controlling a saw. An exemplary automated system for surgical use includes a saw, e.g., a chainsaw, for cutting bone, a feedback system that measures one or more conditions of the chainsaw while it is operating, and a control system that receives information from the feedback system and automatically modifies inputs to the chainsaw to modify operation of the chainsaw based on the feedback. In a first step 191, the saw is operated based on operating parameters sent to the saw. In a second step 192, the feedback system measures one or more conditions of the saw while it is operating. For example, the feedback system can measure one or more forces or other conditions, such as vibration, noise, and / or deflection, as described above. The feedback system sends these signals to the control system. In a third step 193, the control system receives information from the feedback system and automatically modifies inputs to the saw to modify operation of the saw based on the feedback. For example, the control system may change the input to the saw to change its speed or manner or direction of movement (e.g., reverse the direction of the chain and / or switch between unidirectional and oscillating modes). Input from the control system based on information from the feedback system is shown as line 194 in Figure 26. This process may be repeated continuously or as desired to continue automatically updating the operation of the saw based on feedback.

[0175] In addition to cutting bone for implants, such as knee implants, spinal implants, and other implants, embodiments of the chainsaws disclosed herein can be used for other procedures involving cutting bone or tissue. For example, embodiments of the chainsaws disclosed herein can be used to cut bone to join bones, correct conditions, or for other purposes. Thus, the use of the chainsaws disclosed herein is not limited to total knee replacements or total implant arthroplasty. The use of the chainsaws disclosed herein is not limited to use with guidance systems. The chainsaws disclosed herein can be used in many procedures where precise bone or tissue cutting is advantageous.

[0176] As one example, chainsaw embodiments disclosed herein can be used to fuse spines. Using a chainsaw, parallel cuts can be made in adjacent vertebral bodies, removing the intervertebral disc between them and joining two flat surfaces of natural human bone. The precise cuts create a highly stable joint with the opportunity for the mating bones to shift and transform into one unified bone. Chainsaw embodiments disclosed herein can also be used to remove bones that may contain disease, such as tumors or other deformities. An example of this is a foot or toe condition such as hammertoe, where the big toe points toward the midline of the foot, a condition that can result from wearing high heels. Using chainsaw embodiments disclosed herein, one or more cuts can be made to realign the toes into a more natural position.

[0177] Advantages of certain embodiments of the chainsaw disclosed herein compared to prior art oscillating sagittal plane saws include the ability to continuously move the blade teeth without reversing direction and to move the blade teeth in a linear direction across the surface to be cut. Prior art bone-cutting sagittal plane saws typically oscillate slightly about a pivot axis, causing the saw cutting surface to move back and forth against the bone and in an arc relative to the bone. In contrast, in chainsaw embodiments as disclosed herein, the links can move continuously around the sawbar without reversing direction, and the links can move in a linear direction along the longitudinal sides of the sawbar. For example, punctures or other cuts can allow the chain to move continuously around the sawbar without reciprocating, thereby providing a continuous, non-reciprocating cutting action at the longitudinal sides and distal end of the sawbar. Additionally, when the longitudinal sides of the chainsaw are placed against the surface to be cut, the links and their blade teeth can move in a continuous, linear direction across the surface being cut. When the cutting elements have cutting edges that facilitate slicing of bone or other tissue, such as the pyramidal teeth described above, the chainsaw allows for a continuous slicing action through bone or other tissue. The ability to combine a continuous cutting action without reversing direction and / or in a straight line with cutting teeth having the shapes described herein to achieve continuous slicing as the primary cutting method provides unique advantages over prior art saws.

[0178] Another advantage of certain embodiments of the chainsaws disclosed herein is that they can be operated at slow operating speeds. In certain embodiments, the chainsaw can be run at a slow speed while still being able to make a bite or edge on even an inclined or irregular surface, or a foothold on bone. This is a significant advantage over current sagittal saws, which in virtually all cases must be run at a high speed to initiate a cut.

[0179] Another advantage of certain embodiments of the chainsaws disclosed herein is the compactness achievable with the disclosed designs, thereby facilitating their usefulness in certain surgical applications. As a result of the sawbar and link design, the chainsaws can be manufactured in a size small enough to operate safely, reliably, and efficiently.

[0180] Various variations of the above-described embodiments are possible while still retaining one or more features of the present invention. For example, the links of a single chain can be shaped differently from one another. For example, a first type of link can have hooks on both ends, a second type of link can have recesses on both ends, and the first type of link can alternate with the second type of link in the chain. The components of the chainsaw, including the links and sawbar, can be constructed of any suitable material, including metal (e.g., stainless steel), plastic, composite, ceramic, carbon, or carbon fiber materials. Some of these materials can reduce debris and heat, and minimize wear, for example, as a result of the use of biocompatible ceramics.

[0181] The inventions disclosed herein can be practiced together or separately. For example, a chainsaw having links with teeth having the features disclosed herein, such as a pyramidal shape and / or rows along its lateral sides, can be used with different saws, such as a saw with channels or gutters as in FIG. 11B or a saw without rails as in FIG. 11A. As another example, a saw with rails, such as in FIGS. 5A-5C, can be used with links having grooves as disclosed herein but with teeth different from those disclosed herein.

[0182] As will be understood by those skilled in the art, the embodiments included in the present disclosure are not limited to the specific exemplary embodiments described above. While exemplary embodiments have been shown and described, a wide range of variations, modifications, and substitutions are contemplated in the foregoing disclosure. It will be understood that such variations can be made to the above without departing from the scope of the present invention. Accordingly, it is appropriate that the scope of the present invention, as set forth in the appended claims, be construed broadly and in a manner consistent with the present disclosure.

Claims

1. A chainsaw, a sawbar having a first longitudinal side, a second longitudinal side, and a distal end, the first longitudinal side, the second longitudinal side, and the distal end defining at least a portion of a chain path located around the sawbar; A plurality of links are arranged in a chain along the chain path around the sawbar; the sawbar has a rail extending along at least a portion of the chain path around the sawbar; Each of the plurality of links has a groove such that the link straddles the rail of the sawbar.

2. 2. The chainsaw of claim 1, wherein the rail of the sawbar has a protrusion, the groove of the link has a notch that receives the protrusion, and the protrusion prevents the link from shifting away from the sawbar.

3. The chainsaw of claim 1 , wherein the link is disposed on the rail, and a gap exists between the link and the rail.

4. 4. The chainsaw of claim 3, wherein the links are positioned on the rails such that the bottom surface of each lateral side of each link abuts a ledge of the sawbar on each side of the rail, such that forces applied to the links are transmitted to the ledge of the sawbar on each side of the rail.

5. A chainsaw, Sober and a plurality of links arranged in a chain along a chain path located around the saw bar; a first link having a hook that engages a recess in a second link, thereby coupling the first link and the second link together and allowing the first link and the second link to articulate relative to one another without disengaging when the chain is driven around the sawbar; The at least one link has one or more cutting teeth oriented such that a cutting action by the link results in a force being directed at the sawbar perpendicular to the chain path.

6. A chainsaw, Sober and a plurality of links arranged in a chain shape around the saw bar; a first link having a hook that engages a recess in a second link, thereby coupling the first link and the second link and allowing the first link and the second link to articulate relative to one another without disengaging when the chain is driven about the sawbar; The at least one link has cutting teeth in the shape of a cone or pyramid.

7. 7. The chainsaw of claim 6, wherein the cutting teeth are in the shape of an oblique pyramid.

8. The chainsaw of claim 6 , wherein the ridges of the blade teeth are aligned with lateral sides of the at least one link.

9. The chainsaw of claim 6 , wherein the at least one link has a plurality of pyramidal cutting teeth.

10. 7. The chainsaw of claim 6, wherein the at least one link has a first row of pyramidal teeth along a first lateral side of the at least one link and a second row of pyramidal teeth along a second lateral side of the at least one link.

11. 11. The chainsaw of claim 10, wherein the blade teeth located along the first lateral side of the at least one link are staggered relative to the blade teeth located along the second lateral side of the at least one link such that peaks along the first lateral side are aligned with valleys located along the second lateral side.

12. 11. The chainsaw of claim 10, wherein a first link has first pyramidal teeth with a first profile and second pyramidal teeth at an edge of the first link with a second profile that is half the size of the first profile, and a second link located adjacent to the first link has third pyramidal teeth with a profile that is half the size of the first profile, and when the chain is assembled to the sawbar, the third pyramidal teeth of the second link abut against the second pyramidal teeth of the first link.

13. A chainsaw, a sober having a contact surface; a plurality of links arranged in a chain around the sawbar, each of the plurality of links having a contact surface; the plurality of links are arranged around the saw bar such that, when the chain is driven around the saw bar, the contact surfaces of the links slide against the contact surfaces of the saw bar; The chainsaw further comprises a hard coating applied to the contact surface of the saw bar or the contact surface of the link.

14. 14. The chainsaw of claim 13, wherein the hard coating is a diamond coating.

15. A chainsaw, a sawbar having a first longitudinal side, a second longitudinal side, and a distal end; a plurality of links arranged in a chain around the first longitudinal side, the second longitudinal side, and the distal end of the sawbar; and a protective element that prevents the saw bar and the link of the chainsaw from contacting the cutting block when the chainsaw is threaded through the cutting block.

16. the protective element comprises a first guide post spaced apart from the chain along the first longitudinal side of the saw bar when it bears against the chain, and a second guide post spaced apart from the chain along the second longitudinal side of the saw bar when it bears against the chain, 16. The chainsaw of claim 15, wherein the first guide post and the second guide post are wider than the chain.

17. The chainsaw of claim 16, wherein the first guide post and the second guide post are retractable.

18. 16. A chainsaw according to claim 15, wherein the protective element comprises a pushable cover.

19. 1. An orthopedic surgical method comprising: (i) operating a chainsaw in a first direction to cut a bone, the chainsaw comprising: Sober, and a plurality of links arranged in a chain around the saw bar; a first link having a hook that engages a recess in a second link, thereby coupling the first link and the second link together and allowing the first link and the second link to articulate relative to one another without disengaging when the chain is driven around the sawbar; operating the chainsaw in the first direction includes driving the chain in a first direction about the saw bar; (ii) operating the chainsaw in a second direction, wherein operating the chainsaw in the second direction includes driving the chain around the sawbar in a direction opposite to the first direction.

20. 1. An orthopedic surgical method comprising: (i) cutting a precise recessed volume into the bone using a chainsaw, said chainsaw comprising: Sober, and a plurality of links arranged in a chain around the saw bar; a first link having a hook that engages a recess in a second link, thereby coupling the first link and the second link together and allowing the first link and the second link to articulate relative to one another without disengaging when the chain is driven around the sawbar; (ii) inserting into said bone an implant shaped to fit said recessed volume.

21. A method for manufacturing a link for a chainsaw, comprising: molding a link using a metal injection molding process, the link including a first lateral side, a second lateral side, and a plurality of blade teeth; and grinding the first lateral side and the second lateral side of the link using a grinding method.

22. 1. An orthopedic surgical method comprising: robotically controlling a chainsaw to cut bone, said chainsaw comprising: a sawbar; a plurality of links arranged in a chain around the saw bar; A method wherein a first link has a hook that engages a recess in a second link, thereby coupling the first link and the second link together and allowing the first link and the second link to articulate relative to one another without disengaging when the chain is driven around the sawbar.

23. 1. A surgical robotic system, comprising: an arm having a first end and a second end; the first end of the arm is adapted to be coupled to a bone of a patient; The second end of the arm is adapted to be coupled to one of an instrument, a robotic arm adapted to be coupled to an instrument, or a robotic unit including a robotic arm adapted to be coupled to an instrument.

24. 24. The robotic system of claim 23, wherein the tool is one of a bone saw or a bone saw guide.

25. 1. An automated system for surgery, comprising: A chainsaw for cutting bones, a feedback system that measures one or more conditions of the chainsaw as the chainsaw is operating; and a control system that receives information from the feedback system and automatically modifies inputs to the chainsaw based on the feedback to modify operation of the chainsaw.

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