MXPA98000528A - Flexi arrow - Google Patents

Abstract

The present invention relates to a flexible arrow comprising an elongated tubular member of a substantial wall thickness, the tubular member having: (i) a first end, (ii) a second end, and (iii) a central section, the central section is positioned between the first end and the second end, the central section having a groove extending in a generally helical coil path about along the central section of the tubular member, the helical path having from about 1 to about 4 cycles per revolution, the slot has a substantial length and width of up to about 0.1905 of a centimeter, the tubular member has a diameter in the range of about 0.381 cm to 10.16 cm, a helical angle of up to 20 degrees and a radius of amplitude from the serpentine path to an advance in the range of more than 0.1 to 0

Description

FLEXIBLE ARROW Cross Reference to Related Requests This application is a continuation in part of the pending provisional patent application with serial number 60 / 006,064 filed on October 23, 1995, and the pending provisional application with serial number 60 / 001,475 filed on October 18, 1995. July 1995, whose subject matters are incorporated herein by reference, as if they were fully cited.

BACKGROUND OF THE INVENTION Field of the Invention This invention relates to arrows and flexible couplings; specifically with an improved flexible arrow for the transmission of rotating movement and energy around, over or under obstacles. The invention specifically includes an improved flexible arrow for the purpose of widening the medullary canal of the bones.

Brief Description of the Prior Art Arrows and flexible couplings are used to transmit rotary energy between a power source and a driven part when a straight, unobstructed path is not available. A flexible arrow generally consists of a rotating arrow with end fittings for attachment to coupling parts, typically a power source and the driven part, as illustrated in Figure 3 of U.S. Patent No. 4,646,738, the Suhner catalog on page 6, and the SS catalog White Technologies Inc., page 4, (1994). A protective outer jacket can be used to protect the arrow when necessary. Flexible arrows are used in numerous applications anywhere where rotary power transmission is necessary, and is not .-..- ... .'1, -IO a straight unobstructed path, as illustrated "Atalogo de S.S. White Technologies Inc., page 5, and Suhner on page 6. Flexible arrows have been used in children's toys for aerospace applications. Examples of the use of flexible arrows have been presented in the articles "New Twists for Flexible Shafts" (Machine Design, 9/7/89), on particular pages as illustrated on pages 145 and 146, and "Flexible Shafts Make Obstacles Disappear "(Power Transmission Design, July 1993), in particular Figure 1. One example cited was a safety valve, located 9,144 meters away from the ground and not easily accessible, which had to be operated on a daily basis to remain operable , but did not exercise as regularly as required due to the difficulty in reaching it. With the installation of a flexible arrow from the valve to the floor level, the staff was able to operate the valve regularly and verify its proper function. Flexible arrows are used on aircraft to raise and lower ailerons, splints, and entry and exit edges. The flexible stainless steel arrows allow surgeons greater maneuverability with cutting tools and bone formation. Flexible arrows are also widely used to compensate for less than perfect alignment between an actuator and a driven component. The limitation for the use of flexible arrows is without 1, ifee !, and only limited by the capabilities of. of the arrow. The main application of a flexible arrow is to transmit rotational motion and energy in a curvilinear manner. Flexible arrows are used when there is little or no precise alignment between the power source and the driven part; when the path between the power source and the driven part is blocked or is in an environment or position that would not allow the power source; for the connection or activation of components that have relative movements; and to dampen and absorb the vibration of both the drive unit and the driven tool. Until now, the flexible arrows and couplings available for power transmission consisted of single or multiple wires wound onto a central drive core or a hollow core, as illustrated in U.S. Patent No. 5,108,411, Figure 2, and as illustrated in Suhner's publication, pages 15 and 16. The number of wires per layer, and the number of layers will vary in accordance with the application and the requirements for the transmission of torsion energy either unidirectional or bidirectional. Typically the flexible wire-wound arrows are designed and manufactured to be operated in only one direction of rotation; either in the clockwise direction of the clock or counterclockwise, when viewed from the - "• or drive, these are designed to maximize The torque conduction capabilities for the direction of rotation for which these were designed. The operation of a unidirectional arrow operated in the reverse direction is significantly less than the intended performance levels. A specific application of flexible arrows is with flexible reamers of the medullary canal. The reamers of the medullary canal are used to enlarge the medullary canal of the bones in preparation for the insertion of prosthetic components, the insertion of devices for fracture reduction and fixation, such as intramedullary nails, performing an intramedullary osteotomy, the insertion of a plug to prevent the bone cement from migrating while in its viscous state, stimulating bone growth, and for other purposes. Since the medullary canal is irregular in its internal diameter and end-to-end configuration, the surgeon prefers to enlarge the medullary canal to a more uniform diameter, or to a diameter that would allow the passage or insertion of the intended device. Because long-bony arrows bend or curl along their longitudinal axes, flexible bending arrows are necessary to follow this naturally curved path, while transmitting the necessary torsion required to cut the bone. If a straight, rigid, or inflexible arrow is used in the reaming process to enlarge the channel, there is a considerable chance that the reamer does not follow the natural curvature of the bone, does not remove the desired amount of bone, and does not produce a diameter uniform internal In addition, if a straight, rigid reamer is used, there is a high degree of likelihood that the reamer will get stuck, cause excessive bone removal, or penetrate the exterior integrity of the bone. For this reason, spinal canals are almost always prepared with reamers that have a flexible arrow. The flexible medullary reamers are of such a design that they use a central hole for the purpose of receiving a rod or long guide wire, of small diameter, which is initially inserted into the medullary canal. The wire or guide rod establishes a path for the reamer in advance. However, the use of a flexible reamer does not avoid the problem of jamming or stopping the reamer when the cutting head of the reamer is caught by the bone structure and does not turn over. A stuck cutting head can be extremely difficult, if not impossible to unclog or remove without further violation of the involved bone, or breakage of the reaming device. The preferred method for unclogging the reamer would be to invert reamer. However, the design of the devices more Used to prevent the reaming of the reamer without the destruction of the flexible shaft. Until now, the flexible spinal arrow reamers available to the orthopedic surgeon were of three types: (i) an arrow with a plurality of parallel flexible elements or rods joined together at opposite ends by means of a solder solder connection, ( ii) an arrow composed of wire (s) or metal strip (s) wound spirally or helically, and (iii) an arrow composed of a series of interengaged linkages, assembled on a guide rod. The first distinct type of flexible spindle reamer (i) encompasses a plurality of flexible, parallel elements joined together at opposite ends. One drawback is that this arrow occurs during use as the reamer rotates, causing the elements to twist and, by itself, become stiffer and reduce the flexibility of the arrow. Another drawback of this reamer is the tendency of the arrow, since the arrow rotates but is not yet completely inside the confines of the medullary canal, tearing tissue from structures that pass underneath as the individual elements are loaded and unloaded in a manner torsional, enlarging and contracting, by the same, the spaces between the individual wires to catch uninvolved tissue and throwing them to release them. Another drawback of this flexible reamer occurs during the insertion of the reamer on the guide rod. It is intended that the central hole receive the guide rod of small diameter. Except for their respective ends, this reamer lacks a well-defined and bounded central hole. Therefore, it is difficult to prevent the guide rod from leaving the reamer in the area of the free inactive elements during the insertion of the guidewire. Another drawback of this flexible arrow is the inefficient transfer of energy from the power source to the cutting head, which is caused by the twisting and coiling together of the individual elements as the reamer rotates. Another drawback of this type of reamer is that it is extremely noisy during the operation due to the multiple elements sinking together during the rotation. The second distinct type of flexible core reamer (ii) consists of coiled spiral metal wires or strips. This is the most widely used flexible arrow for medullary reaming. The main drawback of this reamer design is that it can only be operated in the forward operation mode. If the cutter jams and the surgeon reverses the reamer to unclog the cutter or to facilitate its * * '-' n, the arrow unrolls, producing in this way _ permanently deformed, unused, and irreparable damage. Another drawback of this spinal reamer is that the torsional load to which it is subjected when in use results in a poor energy transfer and variable degrees of arrow distortion. If the energy source that provides the rotational energy to the reamer is large enough, the coils can be tightened enough to adversely affect the structural integrity of the arrow, and cause the arrow to permanently deform to a helical shape. Another drawback of this type of reamer is the inability to clean the arrow and the cavities inside the helically wound strips of surgical waste, after the operation for the prevention of cross-contamination between the patients. If infectious blood or body fluids are infiltrated into the mechanism of the device, they are extremely difficult to remove and clean. The third distinct type of flexible arrow (iii) consists of a series of interengaged linkages assembled on a guidewire. A different drawback of this design is during the use and exchange of the cutting head. The current use of this design dictates that the linkages are held together by a longitudinal guide wire on which the linkages are assembled. In order to change the cutting head, a flexible tube must be inserted through the central hole of the linkages, and the assembled linkages of the centralization guide wire must be removed. In the process, linkages are often disassembled, and the surgeon is required to reassemble the linkages. U.S. Patent No. 5,488,761 to Leone, shows flexible, spirally wound arrows of the prior art, using a single arrow and a pair of arrows wound upside down. The patent also describes construction materials for the arrow, and a mechanism for cleaning the opening, after it is cut. Alternative cutting technologies are also described. In U.S. Patent No. 4,706,659 to Matthews, the prior art is described, showing two modifications of prior art devices, in Figures 1 and 2. The device of FIG.

Matthews is loosely related to the present invention because this is a mechanism for providing a flexible connection shaft for an intramedullary reamer. Although the solution proposed for the problem is different from that of the present invention, the patent describes the importance of a flexible connection, and describes reamer structures. The description of Matthews 4,706,659 is incorporated as ß eronC to a? A present, as if cited _námente. The Patent of the United States of North America Number 4,751,922 (DiPietropolo) also shows the importance of flexible spinal reamers, and explains some of the problems of the prior art. The patent also discloses the use of a hollow core 2 to receive a guide pin. The Patent of the United States of North America Number 5,122,134 (Borzone et al.) Is incorporated by reference as if cited completely, and note to describe in Figure 5, the use of a guide pin. Figure 1 of Zublin 2,515,365 illustrates a flexible drill pipe for use in drilling well holes. Additional Zublin patents include U.S. Patent Nos. 2,515,366, 2,382,933, 2,336,338, and 2,344,277. The drill pipe is a flexible, helically grooved drill pipe that has a groove that varies from 3/32 of an inch (0.238252 centimeters) to 5/32 of an inch (0.397002 centimeters) in width, and that has an advance of spiral of approximately 22.86 centimeters for a drill pipe with a diameter of 11.43 centimeters (propeller angle of 32.48 degrees). Zublin indicates that the flexible, resilient drilling pipe described has the capacity A * i to bend in a curve of a diameter of 5.4864 meters, -Dating a "dovetail" pattern of more than six cycles per revolution, to be used with a drilling pipe with a diameter of 11.43 centimeters. In the present invention, it has been found that arrows of 2.54 centimeters or less require the use of a helix angle of about half that described by Zublin, and that the number of repeat cycles of the lock pattern is less than the six cycles per revolution shown. For the smaller flexible arrows described, it is more appropriate to use approximately two repeats (cycles) of the pattern per spiral revolution. In accordance with the foregoing, it is an object of this invention to provide a flexible arrow that will flex, bend or bend to follow the natural intramedullary channel of the bone, while transmitting reaming torque. It is another object of this invention to provide a flexible arrow that can be operated in both forward and reverse directions, and consequently, with equal effectiveness. It is another object of this invention to provide a flexible shaft having considerable rotational or torsional rigidity, such that it will not store and then irregularly release rotational energy. It is another object of the invention to provide a flexible na that will be a single unit that does not have to be assembled from multiple units. It is another object of this invention to provide a flexible shaft that will flex, bend or bend while transmitting torsion. It is another object of this invention to provide a flexible arrow that can be operated in the directions both clockwise and counterclockwise, consequently with equal effectiveness. It is another object of this invention to provide a flexible shaft having considerable rotational or torsional rigidity, such that it will not store and then irregularly release rotational energy.

It is an object of the invention to provide a flexible shaft that will be a single unit that does not have to be assembled from multiple units. It is another object of this invention to provide a flexible coupling that will flex, bend or bend while transmitting torque.These and other objects, features, advantages and aspects of the present invention will be better understood with reference to the following detailed description of the invention. the preferred modalities, when read in conjunction with the attached drawing figures.

SUMMARY OF THE INVENTION The present invention overcomes the deficiencies and problems evident in the prior art, as described hereinabove, by combining the following characteristics into an integral, longitudinally flexible and torsionally inflexible shaft. A flexible arrow is provided for the transmission of rotating energy from a drive power unit to a driven unit. The driven unit may be a drill bit, a surgical reamer, a pump, or any similar device. The flexible shaft is an elongate tubular member of substantial wall thickness.

The diameter of the arrow is preferably in the range of from about 0.381 centimeters to about 10.16 centimeters. The diameter ratio of the inner diameter of the arrow to the outer diameter of the arrow is suitably in the range of from about 1: 1.2 to 1: 3, and is preferably in the range of from about 1: 1.3 to about 1: 4. . The thinner the arrow wall, the more critical the slot configuration. Conveniently, the slot is cut at an angle 1 for the arrow, using a controlled cutting technique computer such as cutting with laser beam, water jet cutting, rolling, or other means. Additionally, this groove can be cut at an angle to normal, in order to provide a skewed cut groove, preferably the angle is in the range of from about 30 to about 45 degrees from normal. A groove of substantial length and width extends in a generally helical path, either continuously or intermittently, around and along the tubular member. The groove follows a serpentine path along the helical path, generally around and along the tubular member, which generally corresponds to the shape of the signal wave on a carrier wave, that is, a carrier wave of modulated amplitude. -5 A plurality of slots can be used, thereby increasing the flexibility of the arrow, relative to the arrow having a single slot of identical pattern. The coil path forms a plurality of teeth and complementary cavities on opposite sides of the slot. The slot has sufficient width to form an unbonded joint, allowing limited movement in any direction between the teeth and the cavities, thereby providing limited flexibility in all directions upon the application of tension forces, *; vas, and / or from torsion to arrow. The flexible arrow can have different degrees of flexibility along the length of that arrow. The varied flexibility can be achieved by having the advance of the variable helical groove, along the length of the arrow. The varied flexibility corresponds to the variation in the advance of the helical groove. The helical path can have an angle of the helix in the range of about 10 degrees to about 45 degrees, and the helix angle can be varied along the length of the arrow, to produce correspondingly varied flexibility. Alternatively, the width of the helical groove can vary along the length of the arrow to provide varied flexibility. Conveniently, the width of the slot is preferably in the range of from about 0.3127 centimeters to 1.1905 centimeters. Preferably the width of the slot is in the range of from about 0.0254 to about 3.127 centimeters. The stiffness of the flexible shaft can be achieved through the design of the groove pattern, thereby allowing the use of thinner walls that would otherwise be required to produce equivalent stiffness. In a preferred embodiment, the ratio of the amplitude of the coil path to the advance of the slot is in the range of more than 0.1 to about 0.5. The groove may be filled with a resilient material, partially or completely along the path of the groove. The resilient material may be an elastomer composite which may be of sufficient thickness to fill the groove and to encapsulate the entire arrow, thereby forming an elastomer encased member. The elastomer can be a resilient material such as a urethane or silicone compound. In a preferred embodiment, the driven unit is a spinal canal reamer, for use in reaming the medullary canal of the bones. In this application, the groove patterns and the arrow dimensions above are particularly critical. Preferably, the flexible shaft is formed by laser cutting an elongate tubular member of substantial wall thickness to form the groove around and along the tubular member. The coil path may be formed of a sine wave superimposed on a helical wave. Preferably, the sine wave forms dovetail-like teeth, which has a narrow base region and an anterior region that is wider than the base region. In this way, the adjacent teeth are locked. The teeth may have a configuration such as that illustrated in U.S. Patent No. 4,328,839, the disclosure of which is incorporated herein by reference, as if cited in detail.

BRIEF DESCRIPTION OF THE DRAWINGS These and other objects, features, advantages and aspects of the present invention will be better understood, with reference to the following detailed description of the preferred embodiments, when read together with the accompanying drawing figures. Figure 1 is a schematic representation of a flexible arrow of the present invention. Figure 2 is a schematic representation of the spiral groove of Figure 1, showing covered and uncovered regions. Figures 3 and 4 are schematic illustrations showing the angle of the slot. Figure 5 is a schematic representation of a flexible cable with a resilient filling in a portion of the slot. Figure 6 shows schematic representations of additional spiral slit patterns. Figure 7 is a schematic side view showing spiral grooves having different numbers of cycles per revolution, that is, different advances. Figure 8 is a fragmentary side view of the embodiment of Figure 7, showing the intermediate open space formed by the slot. Figure 9 is a fragmentary side view of the embodiment of Figure 8, showing a section of the '"-" device of the present invention, after having been twisted in the direction in the clockwise direction. Figure 10 is a fragmentary side view of the embodiment of Figure 8, showing a section of the device of the present invention, after being twisted in the counter-clockwise direction. Figure 11 is a perspective view of a flexible coupling, using the spiral groove of the present invention, and showing a plurality of grooves in and z) spiral. Figure 12 is a schematic and cut-away view of the arrow used in reaming a medullary canal of a femur.

DEFINITIONS AND TERMS The term slot, as used herein, is defined in the American Heritage Dictionary, 3a. Edition, Literary Property 1994, as follows: The terms slot and slot are used interchangeably, in consistency with their definitions, as follows: slot - noun. 1. A narrow opening; a slot or slot: - • slot for coins in an automatic dispenser; a . Nura of mail. 2. An intermediate open space between two corresponding points in adjacent screw threads or gear teeth. The term advance, as used herein, is defined in the American Heritage Dictionary, 3a. Edition, Literary Property 1994, as follows: breakthrough - noun. 1. The distance a machine screw travels in one revolution. 2. The distance between two corresponding points on adjacent screw threads or gear teeth. The term helix angle, angle in the figure , as used herein, should define the angle formed between the plane perpendicular to the longitudinal axis of the arrow and the helical path of the spiral along the arrow. The term helix angle can also be defined mathematically as the tangent of the arc of the advance of the helix, divided by the circumference of the arrow. It is intended that the terms used herein have their customary meanings, as stated in the - '~ n Heritage Dictionary, 3rd. Edition, Literary Property Cycle. 1. A time interval during which an event or sequence of characteristic events occurs, frequently repeated on a regular basis: Sunspots increase and decrease in intensity in an 11-year cycle. 2a. A single complete execution of a phenomenon repeated periodically: One year constitutes a cycle of the seasons. 2b. A sequence of events repeated periodically: cycle includes two halves of the wave similar to the graphical wave of the sine of the path of the slot. Spiral the. A curve in a plane that winds around a fixed central point at a distance that continuously increases or decreases from the point. Ib. A three-dimensional curve that turns an axis at a constant or continuously changing distance, while moving parallel to the axis; a propeller lc. Something that has the shape of a curve like: a spiral of black smoke. 2. Printing. A spiral binding. 3. Course or flight path of an object that rotates along its longitudinal axis. 4. An increase or decrease that continually accelerates: the spiral of the wage price. Spiral (adjective) 1. From, or similar to a spiral. 2. Circling around a center at a distance that increases or decreases continuously. 3. Wind around an axis in a series of constantly changing planes; helical. The term amplitude, as used herein, is the maximum absolute value of the periodically changing amount of slot 30. The spiral is more explicitly a helix-like, in the sense that it is a three-dimensional curve resting on a cylinder, in such a way that its angle to a plane perpendicular to the axis is constant. However, along the length of the arrow, the angle of the helix can change in order to impart changes in flexibility to the entire arrow. Using an analogy of electronics, the helix can be seen as a carrier wave with the slot following the trajectory of the modulation of the carrier wave. The teeth or locking regions of the cycle form a ratchet-like structure, in which a Tooth teeth mesh the other set of inclined teeth, allowing movement only in one direction.The term frequency, the number of times a specified phenomenon occurs within a specified interval, as stated in the American Heritage Dictionary, 3a. Edition, Literary Property 1994. Frequency The number of repetitions of a complete sequence of values of a periodic function by unit variation of an independent variable Ib Number of complete cycles of a periodic process that occurs per unit of time lc Number of repetitions per unit of time of a complete waveform, such as an electric current.

The frequency of the slot pattern is the number of times the cycles form a repeating pattern in one unit of length. Reference is made to the number of cycles "C" of the grooves of the groove superimposed on the helical path, which are present in one revolution around the arrow, as the cycles per revolution.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES The arrow of the device of the present invention, generally indicated as 10, as illustrated in Figure 1, "includes an end 14 provided for connection with an element-drive, such as an electric or driven motor. by gas At the other end 13 of the device 10 is included a connecting member 11 which is provided for attachment to a driven part 15 such as a tool, gearbox, or connecting arrow The device 10 includes a longitudinal orifice 20 which arrives from one side to the other from end 13 to end 14, thereby providing a channel for the passage of wires and other instruments, as is well known in the art and discussed above. cut through the wall 22 of the arrow 10, in order to form a coil path that extends generally along the path of a spiral to about the arrow 10, as shown in Zublin, 2,515,365, as the dotted line 20, Figure 1. When the flexible arrow 10 is used for the transmission of energy from the driven end 14 to the driven part 15, the slot 32 in The coil along the spiral path allows the device 10 to be folded along the longitudinal axis of the device 10. The dovetail configuration of the coil slot 32 is composed of the teeth 36 and 38. The teeth 36 and 38 will effectively lock the sections of the dovetail "on and under the teeth 36 and 38, and by the same means-they will transmit the torsion. Where the device is to be used as a flexible arrow for energy transmission, the arrow typically has a diameter less than 2.54 centimeters, but may be larger depending on the specific application. The slot characteristics shown in U.S. Patent No. 2,515,365 can not be applied to this application. An arrow of 2.54 centimeters or less must have a helix angle lower than the helical path, a frequency of the spiral higher, and fewer cycles of groove ripples toward the helical path, to provide the required combination of structural strength and flexibility. Conveniently, the slot is cut perpendicular to a plane tangent to the outer surface of the arrow, as shown in Figure 2a. Alternatively, the slot can be cut at some angle to the longitudinal axis of the arrow and / or the plane tangent to the outer surface, as shown in Figure 2b. The angle can be in the range from zero (perpendicular) to approximately 75 degrees, thereby forming an undercut. Preferably, if the angle is not perpendicular, it is in the range of approximately 30 to 43 degrees from the perpendicular. The undercut can be formed by cutting misaligned radius, or misaligning from a tangential plane to the surface of the arrow in the slot. Additionally, in a preferred embodiment, the body of the arrow has a high level of flexibility to facilitate movement around, over or under an obstacle. The preferred embodiment can be constructed in such a way as to provide varying degrees or segments of custom flexibility. Variations in flexibility can be achieved more quickly by varying the length of the region provided with the spiral grooves, and by varying the angle of the groove relative to the long axis of the arrow. In this way, where high flexibility is required, a longer length of the spiral groove can be used and, conversely, where less flexibility is required, a short groove length can be used. Tailoring improves the ability to drive the arrow in a straight line where required, to negotiate about, over or under obstacles and / or to be driven by a rotating power source whose axis is substantially out of line with the axis of the driven part. While Figure 1 of Zublin, 2,515,365 illustrates more than six cycles per revolution, for use with a drill pipe with a diameter of 11.43 centimeters, in the present invention it has been found that the arrows of --- meters or less require the use of one to four ., _ per revolution, depending on the diameter of the arrow.

Therefore, the change in diameter of the arrow does not result in a proportional change in the size of the slot pattern. It has been found that the lower number of helical cycles per revolution produces greater resistance to fracture under torsion, while providing a less flexible arrow. More preferably, the flexible arrows have a helix angle of less than twenty degrees, in order to produce the required balance between flexibility and structural strength. The range is preferably from about 15 to 20 degrees, which results in an advance equal to the diameter of the arrow. Although the use of a small helix angle, which results in a higher number of revolutions per unit length of arrow, is not preferred unless a very flexible arrow is desired, fewer revolutions per unit length can be used in where less flexibility is required. For example, in the flexible arrow of variable flexibility, the number of revolutions in relatively rigid regions can be reduced, compared to regions of greater flexibility. As shown in Figure 2, the flexible arrow indicated generally as 80, has the advantage of providing a capability for driving around, over or under an obstacle, connecting to a moving obstacle, - • - * - - - - connection to a non-aligned component or to a _._ ^ _ in a severe environment that requires energy. The use of a highly flexible arrow 86 allows for the ease of guiding the energy required to be transmitted to the required part. The advantage of this variable flexible arrow is for a control arrow that must meander around obstacles of different sizes. In sections that require a smaller radius of curvature, that arrow can be made for more flexibility. In areas that require a straight portion, the arrow may remain uncut, and in areas with a very large radius of curvature, the arrow may be less flexible. Figure 5 shows the helix angle,?, Of the spiral. The smaller the angle, the greater the number of revolutions "R" of the helical path per inch, and the greater the flexibility of the arrow. In Figure 6 a variety of slot patterns are illustrated. The patterns are representative of patterns that can be used, and not all are intended to be inclusive. As illustrated in Figure 6A, the pattern has a cycle length C, which includes a neck region NA. The wider the neck region, the greater the strength of the connector, that is, the torsional forces that the flexible arrow can transmit are greater. The capacity of - '' -'ive to lock depends in part on the amount of .position or nesting, indicated as DTA for the Figure 6A and DTB for Figure 6B. The 6C pattern does not provide engagement, and requires a helix angle that is relatively small. The pattern of Figure 6G is an interrupted spiral in which the groove follows the helical path, deviates from the original angle for a given distance, and then recovers the angle of the original helix or other angle of the helix. As shown in Figure 7C, rotation in the direction of the arrow 110 can open the spiral. The inclination angles of Figures 7B and 7C progressively provide greater resistance to the opening, even without the embedding effect being present. It should be noted that in certain patterns, it is preferred to provide an odd number of cycles per revolution, as shown in Figures 7A, 7B and 7C. In this way the peak point of the cycle 41 is out of phase with the peak point 42 of the next revolution. Where the two points are in phase, the amount of material between the two points is so small as to provide adequate structural strength. Obviously, an inclined helix angle, that is, a very low number of cycles per revolution, can be used to provide adequate space between the peak points 41 and 42. The flexible shaft can be produced by any convenient means. More conveniently, computer controlled lamination or cutting, electrical wire discharge machining, water jet machining, spark erosion machining, and most preferably laser cutting, are used to produce the desired pattern. The advantages of laser-controlled laser cutting are the infinite variety of groove patterns that can be produced, the ability to change the angle of the helix at any point along the arrow, the variations with respect to the width of the groove, and the overall accuracy produced, compared to conventional cutting mechanisms. The combination of laser beam cutting with the groove patterns of this invention can produce custom made arrows, which not only have previously determined flexibility, but also variations in flexibility previously determined, while providing substantially uniform characteristics with rotation counterclockwise and clockwise. In Figures 8, 9 and 10 the effect of the rotational forces on the flexible shaft is shown. The rotation in the direction of arrow 62 applies a force in the direction of arrow 62, in the neck region. Conversely, rotation in the direction of arrow 70 applies a force in the direction of force 70 in the neck region. Figure 11 shows the design of a connector 90 that can be inserted between, for example, a rotating power supply and an inflexible or moderately flexible shaft. The flexible connector can be used to provide power transmission between misaligned parts, as described above. In this embodiment, conveniently, a plurality of slots 92, 94 and 96 can be used, as shown in Figure 11. Figure 2 shows the design of a flexible arrow or connector 100 in which an elastomer or flexible material of another way, it is interposed within the slot 102 to further improve the flexibility of the arrow, and to alter the response or torsional rigidity of the member. The elastomer can be used as an absorbing or shock absorbing member. To facilitate manufacturing, to provide protection of the tubular member, to provide a fluid conduit or for other reasons, the elastomer can encapsulate the entire shaft or coupler, thereby forming a tubular construction 104. In a preferred embodiment of the invention the flexible arrow is to be used as a flexible arrow to widen the medullary canal of the bones, the arrow must have a smaller diameter than that of the reamer, which typically has a cutting diameter of approximately .508 centimeters to less than 1,905 centimeters. The spiral pattern shown in the Patent of the United States of America Number ._, ^ 65 can not be applied to this application. The arrow of 1. 905 centimeters or less should have a higher spiral frequency (lower helix angle), and fewer overlapped slot cycles, to provide the required combination of structural strength and flexibility. As shown in Figure 12, during reaming the medullary canal of the femur it is preferred that the arrow be capable of flexing, up to about 45 degrees. The flexible arrow indicated generally as 80, has the advantage of providing a capability to widen the medullary canal of the femur 82, with the end 84 driven by the arrow at approximately a right angle to the axis of the femur. The use of a highly flexible reamer end 86 provides ease of reamer guidance through bone fragments 85, 87 and 89.

Claims (28)

1. A flexible arrow for the transmission of rotating energy, comprising an elongated tubular member with a substantial wall thickness, the tubular member having: (i) a section for connecting to a drive power unit; (ii) a section for connecting to a driven unit; and (iii) a central section element for .idier the first section with the second section, the central section having a groove of substantial length and width, extending in a generally helical path around and along the tubular member.

2. The flexible shaft of claim 1, wherein the groove of the center section follows a serpentine path along the helical path, generally around and along the tubular member.

The flexible shaft of claim 1, wherein the groove of the center section is a plurality of grooves, wherein at least two of the plurality of grooves follow a coil path around and along the tubular member.

The flexible shaft of claim 2, wherein the coil path forms a plurality of teeth and complementary cavities on opposite sides of the groove, the groove having sufficient width to form an unbonded joint, allowing limited movement in any direction between the teeth and the cavities, providing by the same limited flexibility in all directions on the application of tension, compressive, and / or torsional forces to the arrow.

5. The flexible arrow of claim 2, wherein the flexible arrow has different degrees of flexibility along the length of that arrow.

The flexible shaft of claim 5, wherein the advance of the helical groove varies along the length of the shaft, thereby providing varied flexibility corresponding to the variation in the advance of the helical groove.

The flexible arrow of claim 4, wherein the width of the helical groove varies along the length of the arrow, thereby providing varied flexibility corresponding to the variation in the width of the helical groove.

8. The flexible arrow of claim 4, wherein the width of the slots is in the range of from about 0.0127 centimeters to 0.1905 centimeters.

The flexible arrow of claim 8, wherein the width of the slot is in the range of from about 0.0254 to about 0.127 centimeters.

The flexible arrow of claim 4, wherein the ratio of the amplitude of the coil path to the advance of the slot is in the range of more than 0.1 to about 0.5.

11. The flexible arrow of claim 4, wherein the slot is at least partially filled with a - * --1 resilient.

12. The flexible shaft of claim 11, wherein the elastomer composite is of sufficient thickness to encapsulate the entire arrow, thereby forming an enclosed member.

The flexible shaft of claim 11, wherein the elastomer is urethane.

14. The flexible shaft of claim 11, wherein the elastomer is a silicone compound.

15. The flexible shaft of claim 4, wherein the helical path has an angle of the helix in the range of about 10 degrees to about 45 degrees.

16. The flexible shaft of claim 4, wherein the arrow has a diameter in the range of from about 0.381 centimeters to about 10.16 centimeters.

17. The flexible shaft of claim 4, wherein the diameter ratio of the inner diameter of the arrow to the outer diameter of the arrow is in the range of from about 1: 1.2 to about 1: 3.

18. The flexible shaft of claim 4, wherein the diameter ratio of the inner diameter of the arrow to the outer diameter of the arrow is in the range of from about 1: 1.3 to about 1: 2.

19. The flexible arrow of claim 4, wherein the diameter ratio of the inner diameter of the arrow to the outer diameter of the arrow is in the range of from about 1: 1.2 to about 1: 3, the width of the slot being in the range of from about 0.0127 centimeters to 0.1905 centimeters, the ratio of the amplitude of said coil path to the advance of the groove is in the range from more than 0.1 to about 0.5, the helical path has a helix angle in the range of about 10 degrees to about 45 degrees , the arrow has a diameter in the range from approximately 0.381 centimeters to approximately 10.16 centimeters.

The flexible shaft of claim 1, wherein the driven unit is a spinal canal reamer, for use in reaming the medullary canal of the bones.

21. A method of reaming the medullary canal of the bones, comprising transmitting rotational motion from an energy source to a reamer of medullary bone channel, by means of a flexible arrow, the flexible arrow comprising an elongate tubular member with a thickness of substantial wall, subdivided into: (i) a section to be connected to a drive power unit; (ii) a section for connecting to a driven unit; and (iii) a central section element for -the first section with the second section, the nitral section having a groove of substantial length and width, extending in a generally helical path around and along the tubular member, rotating said reamer in the direction in the direction of clockwise and counterclockwise, and widening the bone marrow canal.

The method of claim 21, wherein the slot is in the form of a coil path and forms a plurality of teeth and complementary cavities on opposite sides of the slot, with sufficient free space of the slot to form a joint without gluing, allowing limited movement in any direction between the teeth and the cavities, thereby providing limited flexibility in all directions on the application of tension, compressive, and / or torsional forces to the arrow, and through which they are transmitted rotational forces substantially equivalent in the directions in the clockwise and counterclockwise directions.

23. A method for producing a flexible arrow, for the transmission of rotating energy, comprising the steps of laser cutting an elongate tubular member with substantial wall thickness, to form a groove of substantial length and width, the slot extending into a generally helical path around and along the tubular member.

The method of claim 17, wherein the groove follows a serpentine path around and along the tubular member, forming teeth and complementary cavities.

25. The flexible shaft of claim 3, wherein the coil path is in the form of a repeating waveform.

26. The flexible shaft of claim 3, wherein the coil path is generally a sinusoidal wave superimposed on a helical wave.

27. The flexible arrow of claim 3, wherein the sine wave forms teeth, and wherein the teeth have a narrow base region and an anterior region that is wider than the base region, thereby locking the teeth adjacent.

28. The flexible shaft of claim 4, wherein the slot is undercut at an angle to a radial line or a plane tangential to the surface of the arrow in the slot, the angle being at least approximately 15 degrees from the perpendicular.