Abstract:
A fastening device having a bellows made of a material that changes shape when activated by a catalyst, and having a pleated structure that contracts from an extended state to a contracted state upon activation. The shape changing material may be a shape memory metal alloy, shape memory polymer or elastic memory composite. A method of using this fastener provides apposition and compression of abutment surfaces to join together two pieces of material, and is suitable for joining apposing bone surfaces together to heal fractures via the use of orthopedic hardware.

Description:
TECHNICAL FIELD 
     The present invention relates generally to the joining and compressing together the surfaces of two or more pieces or parts by utilizing a bellows made from a shape memory material. Anchoring elements at opposite ends of the bellows are inserted into or attached to the respective pieces or parts to be joined together. These could be two or more pieces of wood, plastic, metal, bone, or combinations thereof, though not limited to any of these in particular. More specifically, the present invention has an application in the joining of two bone surfaces together for the purposes of osteosynthesis, or of bone fusion, and it relates particularly to a new and improved orthopedic endoprosthesis for fusing the bones together in a toe or finger. 
     BACKGROUND OF THE INVENTION 
     The medical term for a toe or finger is a phalange and any individual bone within a toe or finger is called a phalanx. Deformities of the phalanges are common conditions encountered by surgeons. These deformities can occur for numerous reasons and the deformities have acquired different names such as mallet toe, claw toe, hammertoe, boutonniere deformity, and swan neck deformity, amongst others. Surgeons often address these deformities surgically in an attempt to straighten the phalanges, to alleviate pain, provide stability to the digit, improve ambulation, gait, or dexterity, or prevent further sequelae of phalangeal deformities. 
     The fixation of bone fractures or surgically manipulated bones with orthopedic hardware such as screws, plates, pins, and staples helps bone to heal. Bone fixation was originally accomplished with externally applied casts or other forms of immobilization which led to high rates of nonunion or malunion as these forms of immobilization afforded little inherent stability at the bone-bone interface. Stability is a critical factor for obtaining consolidation or bone healing. Eventually metallic rods and pins were utilized to increase stability of bone fixation thereby improving healing rates. Eventually further stability was gained through the use of screws across bone and joint surfaces because they added a compressive force across the opposing bone surfaces. Further improvements were made to screws via cannulation which allowed the more rapid placement of the screws, more accuracy, and greater ease of use whether for the repair of fractures or fusing the bones of a joint. 
     Of particular interest is the fusion of the proximal interphalangeal joint (PIPJ) of the toes and fingers for stabilizing and correcting deformity of these structures. The procedure normally involves resecting or cutting away the joint surfaces of the PIPJ. The two phalanx bones are then placed end to end and a rod or pin is then driven axially along the internal diameter of the phalange providing stability for osteosynthesis. One end of the pin typically remains outside of the skin of the phalange at the tip of the toe or finger during the healing process. 
     There is concern for many surgeons about the use of pins with this type of surgery because an exposed pin at the distal toe tip may increase the risk of pin tract infections. There is also the possibility of undesired migration of the pins deeper into a bone or the accidental removal of the pin prior to healing of the bone ends. Placing the pin through the skin like this also introduces the pin across the distal interphalangeal joint (DIPJ) and thus violates that joint. Also, the use of pins provides no rotational stability and may allow the phalangeal bones to “piston” on the pin because it is smooth. Therefore some surgeons look toward devices that can be introduced across the PIPJ alone so they do not stick out through the skin, do not violate the DIPJ or the metatarsal phalangeal joint (MTPJ), do not increase the risk for infection, and will provide stability in all planes. However, though there is some legitimacy to these concerns, the use of pins is often necessary when performing toe or finger surgery. 
     There are times when the surgery for reduction of a toe or finger deformity requires more than just a joint fusion of the PIPJ for proper correction. The release of ligaments and the transfer of tendons are sometimes necessary more proximally at the MTPJ adjacent to the PIPJ or at the DIPJ. This is done at the surgeon&#39;s discretion as he or she sees fit and may thus require the use of a pin across one or both of these joints to provide fixation and stability. The DIPJ and MTPJ are rarely fused. Surgeons currently have the option to use a pin and accept its disadvantages, or use some other commercially available product without the use of a pin, each of these having their own disadvantages. 
     DESCRIPTION OF THE RELATED ART 
     One particular prior art device allows the placement of an internal fixation device into a PIPJ that does not violate the adjacent MTPJ or DIPJ. The device is comprised of two members that screw into the bone surfaces and are then joined together. One drawback of the device design is that it does not allow the simultaneous use of a pin in a toe in order to stabilize an MTPJ or a DIPJ. Nor does it provide compression across the joint fusion site which would allow for increased stability and thus improve healing. The device affords no rotational stability. Lastly, during clinical application, the device has been known to separate after implantation due to the patient accidently traumatizing the surgical site. Each of these problems is avoided with the use of the shape memory bellows fastener of the present invention. 
     Another prior art device is a bioabsorbable pin that is placed through the skin through the toe tip across the distal, middle and proximal phalanx of the digit. Like standard pins, they provide no rotational stability to the fusion site and no compression of the fusion site and are thus undesirable. 
     Other prior art intramedullary osteosynthesis devices are made of a material suitable for deformation by thermal or mechanical action. These devices provide increased stability over the above devices by providing compression at the osteosynthesis sites and may afford some rotational stability although their ability to do so effectively is limited. The dependability of these devices to maintain a strong bite or hold, or maintain alignment on the bones they are implanted into, while at the same time providing compression, has not been satisfactory due to design flaws. These devices also fail to provide the surgeon the option of placing percutaneous wires axially through bones of the phalanx and across the DIPJ and MTPJ when necessary. Furthermore, these devices are difficult to implant into bone due to size and tooling restrictions. 
     Still other devices are too complex to use or have multiple small parts making them impractical to use in a surgical setting. One such device is made up of two parts that screw into bone first and then screw into each other. However, this is not practicable because the bones of the phalange cannot rotate due to their ligament, tendon, and other soft tissue attachments. Another such device is hinged and allows a rectus or angular placement so the bones of the phalange can be fused straight or at an angle other than 180 degrees. However, multiple small parts make its use impractical and cumbersome. 
     None of the known prior devices used for the fixation or fusion of interphalangeal joints of the hands or feet are considered sufficient for surgical correction of deformed toes or fingers. The deficiencies include: not providing compression across the fusion site, not anchoring or holding well in bone to provide a firm grasp of the bone such that the device may be easily dislodged after implantation, not cannulated to allow for pinning of the DIPJ or MTPJ when this is necessary, causing nearly complete destruction of the adjacent DIPJ or MTPJ in order to implant the device, requiring very specialized tools for its application such that the implant is not useable without these tools, and/or having very small parts which make the device difficult to use in a clinical setting. These faults result in unwanted sequelae of the intended surgery. 
     SUMMARY OF THE INVENTION 
     In accordance with a first embodiment, a fastener comprises an elongated tubular member having a bellows made from a shape memory material and extending along the central aspect of the member for providing compression across two surfaces. The fastener also consists of tubular sleeves made from the same or similar shape memory material extending from both ends of the bellows, each of the two sleeves containing barbs or an anchoring modality to allow the fastener to grab or bite into bone. Shape memory metal alloys have characteristics that allow them to change shape when they go through a temperature change making them particularly useful for this application. The bellows portion of the embodiment as well as the anchoring barbs goes through a shape change allowing the embodiment to perform its function. The barbs change shape to anchor the embodiment in the bone while the bellows changes shape by contracting, in an accordion-like fashion, to pull together and compress opposing faces of the PIPJ. 
     Many shape memory materials exist. Shape memory metal alloys are probably the most well known and useful. Nitinol is a medical grade biocompatible memory metal alloy made of nickel and titanium currently used in many industrial and medical applications. There are other shape memory metal alloys available. These include but are not limited to alloys composed of iron, nickel, and manganese or iron, manganese, and silicon, some of which are not biocompatible and therefore not for use in human or animal subjects. Many others exist. The shape memory metal alloys have two phases, an austenite phase and a martensite phase. Shape memory metal products are originally manufactured in the austenite phase and annealed to relieve residual manufacturing stresses. The metal may then be cooled sufficiently whereupon it transforms to its highly plastic martensite phase. This phase facilitates manipulation into a new shape by large strain plastic deformation at a low applied stress. The new shape is stable as long as the alloy remains below the phase transition temperature. 
     The two unique properties described above are made possible through a solid state phase change, that is, a molecular rearrangement, which occurs in the shape memory alloy. Typically when one thinks of a phase change a solid to liquid or liquid to gas change is the first idea that comes to mind. A solid state phase change is similar in that a molecular rearrangement is occurring, but the molecules remain closely packed so that the substance remains a solid. 
     Raising the temperature of the martensite phase metal to its transition temperature causes the metal to transform back to its austenite phase and thus back to its original shape. In other words, heat acts as a catalyst to cause or induce this shape change. The austenite phase is stable as long as the material is maintained above its transition temperature. Cooling the austenite phase back to its martensite phase after it has been heated, however, does not cause the material to revert back to the previously deformed shape; a deforming force being required. 
     The preferred embodiments of the shape memory metal bellows fastener are originally manufactured in their austenite phase. The bellows is in a shortened or contracted position (contracted state) and the barbs on the ends of the bellows are displaced radially outward. The fastener is then cooled to its martensite phase and a force is applied to the anchoring barbs forcing them to lie flush or very nearly so, with the tubular sleeves they are attached to. Also a force is applied to the bellows to stretch and elongate the bellows into an extended position (extended state). As long as the fastener remains below its transition temperature, the new shape of the fastener is maintained. The retained memory of the metal fastener allows the deformed device, upon an increase in temperature, to return to its austenite phase. When this happens, the barbs deploy radially outward to embed themselves into the interfacing material and the bellows shortens in an axial fashion, causing the barbs to pull upon the material. The return to the original shortened length of the bellows pulls together any surfaces intended to be compressed together. Thus, the fastener in its martensite phase or extended state may be referred to as a heat responsive fastener that is activated by heat to undergo the transformation from its extended state to its austenite phase or contracted state. 
     Aside from metal alloys there are other shape changing materials, including plastics. Plastics with these characteristics are often referred to as shape memory polymers, elastic memory composites or shape memory composites, and polymeric smart materials. These polymers have different states similar to the phases of the shape memory metal alloys, and these states are generally referred to as a soft phase or a hard phase. These states are also known as a rubbery state or a glassy state, respectively. The glass transition is the reversible transition from a hard phase (extended state) to a soft phase (contracted state) and is responsible for the shape memory effect of the polymer. These materials also need a catalyst for shape changing which may include heat, electricity, electromagnetic fields, light, or chemical solutions. 
     The hard or glassy state is the resting state of a shape memory polymer. A product made from shape memory polymer is originally manufactured in the glassy state by conventional methods. The shape memory product is then transformed into its soft or rubbery state by heating or through the use of other catalysts. Once in the rubbery state it is manipulated and deformed into a new shape and held constrained in this new shape. The shape memory polymer product is then cooled wherein it then returns to a glassy state. When the constraining forces are then removed, the polymer maintains this newly shaped glassy state. The product is then ready for use based on a utility for which it has been designed or created. For instance, the shape memory polymer product may be implanted into a body wherein body heat or some other catalyst has an effect on the newly shaped glassy product causing it to return back to its rubbery state. This last transition from the glassy state to the rubbery state also causes the product to change back to its original shape. These changes in shapes can be used to do work or cause an effect on the tissues surrounding it. 
     Some of the shape memory polymers have the ability to take on two, three, and maybe even four shapes and they can have a wide range of properties, from stable to biodegradable or elastic to rigid. Polymers that show shape memory effects include polyurethane, polyethylene oxide, and polyethylene terephthalate, among others. For example, poly(ε-caprolactone) dimethacrylate and n-butyl acrylate are biodegradable and can be made to change shape through the use of heat from a laser. Fasteners according to the invention made with these shape memory polymers could be used in some applications. 
     Some embodiments of the fastener provide angularity between the tubular members, and still other embodiments demonstrate that the tubular members do not need to be made of shape memory material entirely but may instead be of standard surgical materials and joined by bellows of shape memory material. The invention also includes fastening methods and medical procedures using the bellows fasteners described herein. 
     One or more aspects of the invention are as follows: to allow compression across an object&#39;s surfaces, to prevent slipping or accidental displacement of the implant, to intrinsically afford rotational and torsional stability, and to prevent destruction of adjacent joints. Several embodiments provide a cannulation for accurate placement, rapid placement, and the option of maintaining a pin across adjacent surgical sites if needed. Other aspects will be apparent from review and consideration of the drawings and description. Also, most of the tools required for the placement of the fastener are readily available in most operating rooms, negating the need for large amounts of specialized tooling. 
     The problems these embodiments resolve as pertains to osteosynthesis include: providing reliable compression across a fusion or osteosynthesis site, preventing unwanted distraction of an osteosynthesis site, provide rotational stability, preventing the destruction of adjacent joints, and allowing the option for a wire to remain in the surgical site and adjacent surgical sites at the same time as the invention if the surgeon so desires. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention may be further understood with reference to the accompanying drawings, which are briefly described as follows: 
         FIG. 1A  is a side elevation view of what a normal toe should look like, demonstrating three phalangeal bones that make up the toe and a metatarsal bone of the foot that articulates with the toe, the toe being linear across the joints with no flexion or extension contractures. 
         FIG. 1B  shows a side elevation view of a hammertoe where the toe is non-linear. There are extension and flexion contractures of the joints of the toe effectively causing the toe to be crooked. 
         FIG. 2A  is a profile perspective view of a first embodiment of a fastener according to the invention as shown in its martensitic phase. The fastener is in its elongated stressed phase where the central bellows is stretched and barbs at the ends of the fastener lie flush with the walls of sleeves integral with and extending outward from the bellows. 
         FIG. 2B  is a profile perspective view of a first embodiment of the fastener which has gone through a shape change from the martensitic phase of  FIG. 2A  to its axially shortened austenitic phase. This is the resting shape of the fastener and also the shape of the fastener after implantation into a toe or bone or other substrate. Here the central bellows has shortened axially and the barbs have deployed outwardly from the long axis of the fastener. 
         FIG. 2C  is a profile perspective view with partial cut away of the fastener in  FIG. 2B  in its austenitic phase showing the internal aspect of a main embodiment. 
         FIG. 3  is a perspective view of an alternative embodiment of the fastener in its martensitic phase. It shows the bellows portion of the fastener as an elongated square bellows instead of an elongated cylindrical or tubular bellows. 
         FIG. 4A  is a perspective view of the first embodiment of the fastener in its martensitic phase showing a guide wire being introduced into one end of the embodiment. 
         FIG. 4B  is a perspective view of the fastener of  FIG. 4A  in its austenitic phase with a guide wire passing centrally all the way through the hollow core of the fastener&#39;s long axis. The guide wire can be passed through the embodiment in either its martensitic or austenitic phases. 
         FIG. 4C  is an enlarged perspective view of one end of the embodiment as shown in  FIG. 4B  detailing the guide wire passing into the end of the fastener and the barbs of the fastener deployed outward in their austenitic phase. 
         FIG. 5A  is a side elevation view of a toe wherein the proximal interphalangeal joint has been surgically opened and a cutting blade demonstrates the resection area of bone from the proximal phalanx and middle phalanx that comprise the joint. 
         FIG. 5B  is a side elevation view showing the joint surfaces resected and creating a flat surface for the two bones to abut against each other. A guide wire has been introduced through the flat resected bone surface of the proximal phalanx and passed or driven down the central axis of the phalanx. 
         FIG. 5C  is a side elevation view showing the guide wire still in place in the proximal phalanx. A counter-borer has been placed over the guide wire and driven into the proximal phalanx, reaming the bone to create a void for placement of the fastener. 
         FIG. 5D  is a side elevation view showing the guide wire removed from the proximal phalanx and inserted into the middle and distal phalanx and sticking out passed the end of the toe. The counter-borer has been placed over the guide wire and the middle phalanx reamed with the counter-borer, creating a void for placement of the fastener in the middle phalanx. 
         FIG. 5E  is a side elevation view showing the guide wire repositioned in the toe so that its tip sits just proud of the resected bone surface of the middle phalanx. The view also shows a first embodiment of the fastener in its martensitic phase inserted into the bore hole created in the proximal phalanx. 
         FIG. 5F  is a side elevation view showing that the toe has been manipulated and reduced into position wherein the tip of the guide pin just proud of the middle phalanx has been inserted into the end of the first embodiment of the fastener and the fastener inserted into the void of the middle phalanx. The fastener is still in its martensitic phase. The adjoining surfaces of the proximal and middle phalanx have not yet been compressed together. 
         FIG. 5G  is a side elevation view of the fastener having undergone its phase change and is now in its austenitic phase. The barbs on the fastener have deployed into the bone and the bellows has compressed the bone surfaces together via its shape change. The guide wire has also been driven all the way into the proximal phalanx. 
         FIG. 5H  is a side elevation view showing the fastener again in position across the proximal interphalangeal joint and having compressed together the bone surfaces. The guide wire has been driven across the metatarsal-phalangeal joint into the metatarsal, stabilizing the joint. 
         FIG. 6A  is a side elevation view showing an alternative embodiment of the fastener wherein the fastener is angled to allow fusion of the proximal interphalangeal joint at an angle. 
         FIG. 6B  is a side elevation view showing the alternative embodiment of  FIG. 6A  placed in the proximal interphalangeal joint, fusing the bones together at an angle. 
         FIG. 7A  is a side elevation view of an alternative embodiment of the fastener wherein it seemingly is identical to the main embodiment and is shown in its martensitic phase. However, this second alternative embodiment goes through an angular shape change built into the bellows as will be seen in  FIG. 7B . 
         FIG. 7B  is a side elevation view of the embodiment of  FIG. 7A  wherein the fastener is shown in its austenitic shortened phase and has also undergone an angular change for the purpose of fusing a toe in an angular position. 
         FIG. 8A  is a perspective view of an embodiment of the fastener having three separate component parts. There is a central bellows for undergoing a shape change and which is attachable to two identical screws that can be implanted into bones prior to coupling the bellows to these screws. One screw is designated to attach to one side of the bellows while the second screw attaches to the opposite side of the bellows. 
         FIG. 8B  is a perspective cut-away view of  FIG. 8A  showing the inside of the fastener of  FIG. 8A . 
         FIG. 8C  is an enlarged perspective and cut-away view showing details of the coupling mechanism for joining one end of the bellows to the proximal end of one of the screws of  FIG. 8B . 
         FIG. 8D  is an enlarged perspective and cut-away view showing details of the coupling mechanism for joining the other end of the bellows to the proximal end of the other screw of  FIG. 8B . 
         FIG. 8E  is a perspective cut away view showing an alternative embodiment of the fastener in its martensitic phase with each end of the bellows joined to a screw. 
         FIG. 8F  is a perspective view of the alternative embodiment of  FIG. 8F  showing the bellows in its austenitic shortened phase with each end of the bellows joined to a screw. 
         FIG. 9  is a side elevation view of the alternative embodiment of  FIG. 8F  showing the fastener implanted into a proximal interphalangeal joint. The bellows is in its austenitic shortened phase with a guide wire implanted through the toe and into the metatarsal, passing through the cannulation of the fastener. 
         FIG. 10  is an exploded perspective view of an alternative embodiment of the fastener showing two separated component parts of the embodiment. There is a central bellows and one end of the bellows has an integral sleeve with barbs for fastening into bone. The other end of the bellows has a coupling mechanism for attaching to a screw for implanting into another bone. 
         FIG. 11  is a perspective view of an alternative embodiment showing a single piece construct with integral sleeves. The central bellows has an integral screw at one end as a means for implanting and securing the fastener into bone and the opposite end has an integral sleeve with barbs for anchoring the fastener into another bone. 
         FIG. 12  is a perspective view of an alternative embodiment of the fastener showing a single piece construct wherein the central bellows portion of the fastener is integrally connected at each end to a screw. One screw has right hand turning threads while the other screw has left hand turning threads. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention is a fastener that provides axial compression of two opposing surfaces. The fastener is generally a linear, cylindrical tube made in whole or in part of shape memory metal, super elastic metal, or other material having similar shape changing characteristics. The central portion of this tube takes the shape of a bellows and preferably is made of a shape memory metal. The shape memory metal may be an alloy produced or made in its austenite phase and annealed to relieve residual manufacturing stresses. Subsequently, a change to a martensitic phase can be induced in the shape memory alloy by sufficiently cooling the metal. In the martensite phase, the bellows is plastically deformed into an elongated shape, which is its extended state. Additionally, anchoring barbs are plastically deformed to lie flush, or approximately so, with the tubular sleeves. The low temperature is maintained and functions to maintain the deformed shape until implantation. The shape memory of the metal allows the deformed device, upon an increase in temperature, to deploy the barbs radially outward to embed themselves into the interfacing material and the bellows to shorten in an axial fashion, causing the barbs to pull upon the material and compressing together any surfaces intended to be compressed together. 
     As an example of its use, the fastener may be implanted into opposing bone surfaces of a resected joint of a finger or a toe and a change in shape of the memory metal after implantation causes the two bone surfaces to be drawn and compressed together. The compression imparts a resistance to be being pulled apart as well as resistance to axial rotation, shearing and side to side bending. The forces from the shape change in the bellows are transmitted through the barbs into the bone they are embedded into, pulling the bone together as the bellows contracts. These barbs also add to the rotational stability of the fastener and offer resistance to distractive forces across the fusion surfaces which would delay bone healing. As described in the following embodiments, the fastener may be used for joining together the ends of bones, repair of bone fractures, or stabilizing surgically-induced bone cuts. The embodiments may also be used for joining or coupling other objects as well, such as a piece of plywood to a cement wall or a piece of plastic to a piece of metal, two wood surfaces, or a tooth to a bone. 
     First Embodiment 
     A first embodiment of a fastener  10  according to the invention is shown best in  FIGS. 2A and 2B , and  FIGS. 4A and 4B .  FIGS. 5A-5H  are side elevation views of the stepwise operation of the first embodiment. Fastener  10  is made of a shape memory metal alloy such as Nitinol, commonly used in medical applications, but other shape memory alloys and shape memory polymers could be used for non-medical applications. Shape memory alloys have two phases, an austenite phase and a martensite phase. Fastener  10  is originally manufactured in its austenite phase which is shown in  FIG. 2B . After fastener  10  is manufactured, it is cooled to its martensite phase to allow it to be changed by deformation from its original shape to the new shape shown in  FIG. 2A . As long as fastener  10  is kept cooled, it will remain in the deformed martensitic phase of  FIG. 2A . 
     In a first embodiment, the fastener  10  is generally tubular or cylindrical in design and is symmetrical around its longitudinal axis. In the central aspect of fastener  10 , the tubular shape is expanded into a folded, pleated or corrugated shape, hereinafter referred to as pleated, taking the form of a bellows  14 .  FIG. 3  shows an alternative to this embodiment wherein the expanded shape is generally square, but other cross-sectional shapes may be used as well, such as oval, rectangular or triangular, but all of these shapes are still pleated along the longitudinal axis of the bellows. The cross-sectional shape selected preferably has a continuous periphery, although the periphery could be segmented where all or a portion of the bellows is formed by strips of shape changing material. 
     As shown in  FIG. 2A , bellows  14  has a first end face  22 A and a second end face  22 B that serve as the ends of the bellows. Bellows  14  consists of a plurality of pleats  25 , the number of such pleats controlling the development of the compressive force and the length change of the embodiment after the bellows undergo a shape change. Extending axially outward from end faces  22 A and  22 B of bellows  14  are further elongated tubular structures  18 A and  18 B respectively, hereinafter called sleeves  18 A and  18 B. Sleeves  18 A and  18 B have distal ends  82 A and  82 B, respectively, as shown best in  FIGS. 2A ,  2 B and  4 C, which are opposite the sleeve end attached to the bellows and serve as the terminal ends of the fastener (hereinafter termed the terminal ends  82 A and  82 B). Terminal ends  82 A and  82 B are preferably circular and the axis through the centroid of each circular area is parallel and coincident with the long axis of the fastener. As seen best in  FIGS. 2A-2C , terminal ends  82 A and  82 B each have a centrally placed portal  84 A and  84 B. Portals  84 A and  84 B are the beginnings of central longitudinal and cylindrical lumens or passages  30 A and  30 B. As seen best in  FIGS. 2B and 2C , these lumens pass from the terminal ends  82 A and  82 B axially through the center of sleeves  18 A and  18 B, respectively. Hereinafter, lumens  30 A and  30 B will be termed cannulations  30 A and  30 B. 
     Sleeves  18 A and  18 B and cannulations  30 A and  30 B are all axially aligned with each other.  FIG. 2C  shows the internal makeup of the main embodiment. The hollow internal diameter of bellows  14  is termed chamber  16 . Cannulations  30 A and  30 B become contiguous with chamber  16  where sleeves  18 A and  18 B meet the end faces  22 A and  22 B of bellows  14 . These are axially aligned such that a straight wire can be passed through portal  84 A and cannulation  30 A of sleeve  18 A, continue through chamber  16 , and further through cannulation  30 B of sleeve  18 B, and finally passed out of portal  84 B. As shown best in  FIGS. 4A ,  4 B, and  4 C, portals  84 A and  84 B and cannulations  30 A and  30 B have a diameter sufficient to accommodate a guide wire  34 , which can be used during a surgical procedure. The cannulation diameter is preferable only slightly larger than the wire diameter to precisely guide axial transport of the sleeves  18 A and  18 B and thereby insure accurate placement of the fastener  10  within the bones to be joined. Chamber  16  has an equal or greater diameter to accommodate guide wire  34 . 
     As seen best in  FIG. 2A , set inward from distal ends  82 A and  82 B along the length of each sleeve  18 A and  18 B are a plurality of tabs  26  cut into each sleeve and shown in their cold state with their surfaces aligned with the surfaces of the sleeves. These tabs will hereinafter be called barbs  26 , because of the purpose they serve in their heated state of anchoring fastener  10  into a bone substrate and thereby preventing the fastener from being pulled out when axial stress is applied to the fastener. In other words, the barbs  26  transform the terminal ends  82 A and  82 B into anchoring members.  FIGS. 2B and 2C  show four barbs  26  evenly spaced from each other around the periphery of each sleeve, and in their heated and expanded state wherein they are slanted substantially outward from the fastener axis in the direction of end faces  22 A and  22 B of bellows  14 . At least one and preferably two or more barbs would be acceptable for this embodiment and the other embodiments described herein. Multiple barbs could also be offset from each other length-wise along the sleeves or circumferentially around the outer periphery of the sleeves such that one could conceivably have six, eight or more of these barbs per sleeve. 
     In forming barbs  26 , each sleeve  18 A and  18 B is cut through its full wall thickness from the external side of its outer diameter to the internal cannulation  30 A and  30 B, as most notably seen in  FIG. 2C . Each barb  26  thus has the same thickness as the wall of sleeves  18 A and  18 B and, being cut from the metal of the sleeves, the outer and inner surfaces of the barb in its retracted position are substantially flush with the outer surface of the sleeve and the inner sleeve surface defining the cannulation, respectively, when the sleeve is in its cold or martensitic phase. 
     Thus, each barb  26 , being made from shape memory metal and in its cooled martensitic phase, lies parallel to the long axis of fastener  10 . As best shown in  FIGS. 2C and 4C , barb  26  has a proximate end set outward from bellows  14  closest to terminal ends  82 A and  82 B of sleeves  18 A and  18 B, which will be called base  28 . Base  28  functions as the hinge point of barb  26  when the barb goes through its shape change. Set opposite base  28  and substantially towards bellows  14  along the length of barb  26  is a distal end portion in the form of an apex  27 , which is generally pointed or arrowhead shaped. 
     Like the bellows, barbs  26  will undergo a shape change when transforming from a cooled martensite phase to an austenite phase as they are warmed to body temperature. This process is best seen in  FIG. 2A , wherein fastener  10  is in its martensite phase, and  FIG. 2B , wherein fastener  10  has changed back to its austenite phase. In so doing, each barb  26  will curl or bend outward away from the central longitudinal axis of fastener  10 . Base  28  serves as the pivot or bending point for each barb. Apex  27  is designed to help the barb cut into or push its way into the surrounding substrate that fastener  10  is being implanted into in order to anchor fastener  10  and prevent its rotation or pull-out. During this warming process, bellows  14  axially shortens during the change from its martensite phase to the austenite phase as shown best in the shape change from  FIG. 2A  to  FIG. 2B . Alternatively, barbs  26  may be partially deployed in their cold state by being partially bent outwardly at time of insertion into bone in order to mitigate slipping of the fastener and prevent accidental pullout before being fully deployed. 
     Operation of First Embodiment 
     Fastener  10 , as well as the other embodiments described herein, may be made from a shape memory alloy, such as Nitinol, though there are other shape changing materials available that also may be used. When any of these embodiments are used, say for a surgical procedure like a hammertoe correction, the properties of the metal or other material allow it to exist in different shapes at different temperatures. For example, when the Nitinol embodiment is moved from a cool or cold state, at which time it is in its martensite phase, and then implanted in the body and warmed to body temperature, it will undergo a change in its shape as it transforms to its austenite phase. 
     As shown again in  FIGS. 2A and 2B , bellows  10  will shorten along its axial length, like an accordion, during its phase change from a martensitic phase to an austenitic phase. At the same time, barbs  26  on sleeves  18 A and  18 B will go through a phase change as well, expanding radially outward from their base  28  such that they will anchor the embodiment into a substrate, for example, the bones of a proximal and middle phalanx of a toe or finger. This axial shortening of bellows  10  provides the necessary compressive force to draw together two bone ends that have been surgically prepared or fractured. 
       FIG. 1A  demonstrates a normal toe which is made up of multiple bones. The parts of a normal toe include a metatarsal bone  54  and a proximal phalanx  42 . Together the articulation of metatarsal bone  54  and proximal phalanx  42  make up a metatarsal phalangeal joint  62  or MTPJ  62 . More distally along the toe, a second articulation is made between proximal phalanx  42  and a middle phalanx  46 . This articulation constitutes a proximal interphalangeal joint  66  or PIPJ  66 . Even more distally along the length of the toe, a third articulation occurs between middle phalanx  46  and a distal phalanx  50 . This articulation constitutes a distal interphalangeal joint  70 , or DIPJ  70 . Anatomically, a normal toe lies in a straight or linear fashion along its length from metatarsal bone  54  to the distal end of distal phalanx  50 , as shown best in  FIG. 1A . PIPJ  66  and DIPJ  70  generally have no substantial angular deformity while MTPJ  62  normally rests at about a 15 degree angle. 
     Looking at  FIG. 1B , one can see a hammertoe, a toe that is deformed or not straight. Here the toe has angular contraction deformities at the joints along the length of the toe. In a classic hammertoe deformity, as demonstrated in  FIG. 1B , there is a contracture of MTPJ  62  well beyond a normal 15 degrees whereby proximal phalanx  42  is upwardly displaced on metatarsal bone  54 . Tight ligaments and tendons, not shown, facilitate holding the deformed MTPJ  62  in this position, contributing to the toe&#39;s pathology. Then, looking at PIPJ  66 , middle phalanx  46  is contracted downward. Again, tight ligaments and tendons facilitate holding deformed PIPJ  66  in this position. Lastly, at DIPJ  70 , distal phalanx  50  is contracted upward in relation to the downward positioned middle phalanx  46 . Yet again, tight ligaments and tendons facilitate holding the deformed PIPJ in this position. 
     In the surgical correction of a hammertoe, the general principle is to address the primary deformity at the level of PIPJ  66 . To do so requires making a surgical incision over PIPJ  66 , dissecting the soft tissues down to the ligaments and tendons of the joint, and cutting these to reflect them out of the way such that the surgeon can access the bones of PIPJ  66 , namely proximal phalanx  42  and middle phalanx  46 . Herein below is the application of the first embodiment. The application and operation can best be seen in  FIGS. 5A through 5H .  FIG. 5A  shows a hammertoe where surgical exposure of the bones of PIPJ  66  has been performed. A surgical saw  69  is used to cut the articulating portion of bone from proximal phalanx  42 , perpendicular to its long axis, effectively producing a flat cut surface  78  of proximal phalanx  42 . Subsequently a surgical saw is again used and the articulating portion of bone from the middle phalanx  46  is cut away, producing a flat cut surface  74  of middle phalanx  46 . The flat cut surfaces  74  and  78  are sometimes referred to hereinafter as abutment surfaces. 
     In  FIG. 5B , a guide wire  34  attached to a wire driver  38  is then inserted into the abutment surface  78  of proximal phalanx  42  and advanced down the center of proximal phalanx  42  to the area of MTPJ  62  but not into it. Wire driver  38  is then removed from over guide wire  34 . As shown in  FIG. 5C , a counter-borer  108 , cannulated like fastener  10 , is then slid over guide wire  34  and used to ream out some of the bone from proximal phalanx  42 , leaving a hollow tubular shape or bore in the bone matching the shape of approximately one-half the length of fastener  10 . Hereinafter, this matching hollow tubular bore will be termed bore hole  110 . If one of the non-round embodiments is used, say a square or triangular embodiment, a similarly shaped broach may be used instead of a counter-borer. Counter-borer  108  is then removed from proximal phalanx  42  and guide wire  34  is subsequently removed with wire driver  38 . 
     In  FIG. 5D , guide wire  34  is placed into the center of abutment surface  74  of middle phalanx  46 . Guide wire  34  is then driven axially down the central long axis of middle phalanx  46 , driven across DIPJ  70  into distal phalanx  50 , and then out through the skin on the end of the toe. The wire driver  38  is then removed from a proximal end  100  of guide wire  34 . Counter-borer  108 , shown in  FIG. 5D , is then slid over proximal end  100  of guide wire  34  and used to bore into middle phalanx  46 , producing a hollow tubular shape that matches the other one-half of fastener  10 , hereinafter termed bore hole  111 . It is also contemplated for this embodiment and those described herein below that the respective sleeves and corresponding portions of the bellows of the fastener may differ from each other in size, length and/or shape with corresponding differences in their bore holes. Counter-borer  108  is removed from guide wire  34  and, as shown in  FIG. 5E , using wire driver  38 , guide wire  34  is then advanced further out the end of the toe so that proximal end  100  of the guide wire is sitting just proud of abutment surface  74  of middle phalanx  46 . Up until this point, the fastener has been previously sterilized and has been kept refrigerated so as to maintain the fastener at its martensite phase, elongated and the barbs lying flush with the sleeves of the fastener. 
       FIG. 5E  shows fastener  10  imparted into matching bore hole  110  of proximal phalanx  42 . The surgeon then manipulates the bones by grabbing proximal phalanx  42  and middle phalanx  46  and raising middle phalanx  46  upward and placing proximal end  100  of guide wire  34  into sleeve  18 B of the fastener. Middle phalanx  46  is then press fitted onto sleeve  18 B and the portion of fastener  10  that remains protruding from proximal phalanx  42 . As middle phalanx  46  is imparted onto fastener  10 , guide wire  34  passes along cannulation  30 B of the fastener. As shown in  FIG. 5F , abutment surface  78  of proximal phalanx  42  and abutment surface  74  of middle phalanx  46  are then manually approximated together such that they are contacting each other. At this point, the proximal phalanx  42 , middle phalanx  46 , and distal phalanx  50  are all now aligned straight and the fastener  10  warms to body temperature. 
     As the fastener  10  warms to body temperature, it changes from its cooled martensite phase to its warmed austenite phase, undergoing a shape change. In so doing, barbs  26  deploy by expanding radially outward from the central axis of the cannulation  30  and embed themselves into the bone of the surrounding proximal phalanx  42  and middle phalanx  46 . Transitioning from  FIG. 5F ,  FIG. 5G  shows that as this process occurs, the bellows, in accordion fashion, shortens along its axial length, drawing together into abutment and compressing together the cut surface  74  of middle phalanx  46  and the cut surface  78  of proximal phalanx  42 . This compressive force across the middle and proximal phalanx provides necessary stability to allow the two bones to heal together. It is at this point that the surgeon will decide if the procedure is complete. If he or she feels the procedure is complete, the guide wire  34  is removed from the toe as facilitated by use of wire driver  38  on distal end  96  of guide wire  34 . Then layered closure of the tendon, ligaments, and skin is performed. Fastener  10  remains in place to provide stability during healing. 
     There are times however when the surgery is not complete at this point. Oftentimes adjunctive procedures are performed on DIPJ  70  and MTPJ  62  at the same time as the osteosynthesis procedure on PIPJ  66 . Typically these procedures involve tendon or ligament surgery, or sometimes cutting of bone. Osteosynthesis is rarely performed on DIPJ  70  or MTPJ  62  but the tendon and ligament procedures that might be performed can leave the joints unstable due to soft tissue imbalances. If the surgeon decides that she or he needs to afford stability to these joints as well, then she or he may decide to utilize another important function of fastener  10 , that being cannulation  30 , which will allow guide wire  34  to be left within the toe during healing along with fastener  10 . As shown in  FIG. 5H , instead of removing guide wire  34  after the fastener has gone through its shape change, a surgeon may advance guide wire  34  through cannulation  30  and across MTPJ  62  into metatarsal  54 , providing stability to MTPJ  62  so that it cannot be moved during the healing process. Instead, the surgeon may leave the guide wire  34  in place across DIPJ  70  without crossing MTPJ  62 , as best shown in  FIG. 5G . This then affords stability only to DIPJ  70 , if necessary. The distal end  96  of guide wire  34  is then left sticking out the end of phalanx  50 . The wire is left in this position for approximately 4-6 weeks after the surgery while osteosynthesis or fusion occurs across proximal phalanx  42  and middle phalanx  46 . After healing has occurred, the surgeon may remove guide wire  34  in their office by grasping the exposed distal end  96  with a pliers and pulling it out, thus negating a return to the operating room. 
     Second Embodiment 
     Hereinabove has been set out a first embodiment for a shape memory metal bellows fastener. A second embodiment allows for angular positioning of the middle and proximal phalanx of the toe. As shown in  FIG. 6A , a fastener  10 B is not linear but rather angled and is seen here in its austenite phase, having shortened from an elongated position and barbs  26  having expanded outward as already described hereinabove. In this figure, the angularity of the fastener occurs in the mid-portion of bellows  14 B. Situated substantially towards the middle of bellows  14 B, one of pleats  25  of bellows  14 B is replaced by a boss  112 , wherein the ends of the boss are angled relative to each other instead of being parallel. Boss  112  has an end face  113 A that is positioned closest to sleeve  18 A and an end face  113 B positioned closest to sleeve  18 B. Boss  112  may divide the bellows approximately into two equal halves. However, boss  112  may instead replace the first pleat or be situated anywhere between the first pleat and the last pleat. 
     Boss  112  is symmetric about a plane whose normal direction is inclined at an angle to the axis of sleeve  18 A and inclined at an equal angle to the axis of sleeve  18 B, causing end faces  113 A and  113 B to slope towards each other, creating an angularity γ to the embodiment. Sleeves  18 A and  18 B are thus no longer coaxial in this embodiment and the angularity of boss  112  is translated to an angular relationship θ between the sleeves. Angle γ equals angle θ. Most surgeons prefer to fuse a toe straight or at zero degrees while some may prefer a ten to fifteen degree angle. When it comes to fingers, the joints are often fused at greater angles and so the embodiment may need an angularity of greater than fifteen degrees, such as twenty degrees to fifty degrees for a functional result. It is further contemplated that sets of fasteners may be provided to give boss angularities preferably at least between 1° to 15°, more preferably 1° to 45°, most preferably 1° to 60°, and preferably in increments of 5°. 
     Operation of Second Embodiment 
     The application of the second embodiment requires the proximal phalanx and the middle phalanx to be prepared with angular cuts. The cut surface of the proximal or middle phalanx, instead of being cut perpendicular to the long axis of the bone, is cut at an angle to the long axis. The sum of the angles cut into both phalanxes is such that it matches the built-in angle of the embodiment; say ten to fifteen degrees for a toe or whatever the angle of the embodiment. 
     The step wise application of the embodiment is otherwise the same as  FIGS. 5A through 5F . The proximal phalanx is cut and the middle phalanx is cut, each at one-half of the desired full angle. A guide wire is placed axially into the proximal phalanx and the phalanx is then counterbored to create a hole for the implant. The guide wire is then removed and driven axially into the middle phalanx and out the end of the toe. Again the guide wire is positioned so that it is nearly flush with the cut surface of middle phalanx or slightly protruding. A counter-borer is then placed over the guide wire and a hole created to appropriate depth to match one-half the shape of the second embodiment.  FIG. 6B  shows the angled fastener in place in a toe with a slight angularity to the fusion site. The guide wire is then left in place or it can be removed at this point. Fastener  10 B is inserted into matching bore hole  110  of proximal phalanx  42 . Middle phalanx  46  is positioned onto the portion of fastener  10 B that remains protruding from the proximal phalanx  42 , all in similar fashion as described for the first embodiment. 
     As the middle phalanx  46  is installed onto fastener  10 B, guide wire  34  is free to pass along cannulation  30  of the fastener up to the point where the angularity prevents it from passing any further and so this embodiment is more desirable when pinning of the MTPJ  62  is not necessary. Cut surface  78  of proximal phalanx  42  and cut surface  74  of middle phalanx  46  are manually held together such that they are in intimate contact with each other until fastener  10 B goes through its shape change. Thus, other than the bone cuts and angular shape of fastener  10 B, the function of the embodiment is the same as the first embodiment. 
     Third Embodiment 
       FIGS. 7A and 7B  show another alternative embodiment wherein a fastener  10 C again allows bone fusion in an angular fashion but this time there is an axial shortening of bellows  14 C simultaneous with an angular shape change. Prior to its shape change, fastener  10 C looks identical to the first embodiment (fastener  10  as shown in  FIG. 2A ). The difference is shown in  FIG. 7B , wherein fastener  10 C is originally manufactured in its austenite, resting, or unstressed phase with a bend in bellows  14 C. The end faces  22 A and  22 B are angled towards each other at pre-determined angles, say anywhere from five degrees to fifty degrees, or from one degree to 60 degrees, or within the other angle ranges as discussed above in regard to the second embodiment. Fastener  10   c  is manufactured in its austenite phase, as shown in  FIG. 7B , and bellows  14 C subtends angle β which imparts an angle α to the long axis of fastener  10 C. Angle α equals angle β. 
     After the fastener  10 C is manufactured, it is cooled from its austenite to martensite phase to allow its shape to be changed by deformation. The barbs are pressed flat so that they are flush and in alignment with the walls of sleeves  18 A and  18 B. The fastener is then stretched or elongated and angles α and β are eliminated so that the fastener is now linear and not angular. The shape is stable as long as it remains in its martensite phase. When the martensitic phase of the fastener  10 C of  FIG. 7A  is implanted into the body and brought to body temperature, the fastener will deform back to its original austenitic shape of  FIG. 7B , thereby shortening along the length of bellows  14 C. It will also bend through angle α along the length of the bellows so that the bones of the phalanx can be compressed and fused at the resulting angle β. 
     Operation of Third Embodiment 
     The joint surfaces are prepared as before for the second embodiment. Proximal phalanx  42  and middle phalanx  46  are surgically prepared as before as shown in  FIG. 6B . Here abutment surface  78  of proximal phalanx  42  and abutment surface  74  of middle phalanx  46  are prepared so they are at an angle to the long axis of each phalanx respectively. If the surgeon or user wants to fuse the two bones at ten degrees, for instance, then the cut surfaces must be prepared so that the angle formed between the long axes of proximal phalanx  42  and middle phalanx  46  equals ten degrees when both cut surfaces are placed end to end. For example, one surface could be cut at zero degrees or perpendicular to the long axis of the phalanx while the surface of the other phalanx is cut at ten degrees. Alternatively, both phalanges could be cut equally at five degrees. The surgeon will need to choose the implant that is designed to bend ten degrees. 
     If the surgeon wants to fuse the two bones at fifteen degrees, then she or he would have to prepare the cut surfaces to equal fifteen degrees total angulation. For example, one surface could be cut at zero degrees or perpendicular to the long axis of the phalanx while the surface of the other phalanx is cut at fifteen degrees. Alternatively, both phalanges could be cut equally at seven and one-half degrees and the surgeon would need to use an implant designed to bend fifteen degrees. 
     After the respective cut surfaces are prepared, each phalanx is then counter-bored preferably to equal depths as in the first embodiment and the implant is then inserted into each phalanx as previously described. The middle and proximal phalanx are then manually held pressed together while fastener  10 C goes through its shape change. Herein again barbs  26  deploy and expand outward, being embedded into the surrounding bone. Bellows  14 C also goes through its shape change and shortens axially to draw the cut faces of the middle and proximal phalanx toward each other and to bring and compress together these surfaces of the proximal and middle phalanx. Simultaneously, bellows  14 C bends along the length of the bellows positioning the phalanxes in an angled arrangement. 
     Fourth Embodiment 
     A fourth embodiment includes some substantial differences relative to the above three embodiments with the same end result.  FIGS. 8A through 8F  shows fastener  10 D. Bellows  14 D has again an end face  22 A and end face  22 B. Extending outward in an axial direction from end face  22 A and  22 B are male connectors or couplers  114 A and  114 B. Passing axially down the center axis of fastener  10 C through male connectors  114 A and  114 B is cannulation  30  to again accommodate guide wire  34 . Hereinafter, the description of male connector  114 A will be inclusive of male connector  114 B since they are otherwise identical. As best shown in  FIGS. 8B and 8D , male connector  114 A is formed as a hollow cylindrical tube or sleeve  116 A to extend axially from end face  22 A of bellows  14 D. Sleeve  116 A includes an integral ring  118 A formed around its end that is opposite to its attachment to end face  22 A. Ring  118 A extends radially outward from the outer diameter of sleeve  116 A and forms a collar  119 A, as seen best in  FIG. 8D . A collar  119 B is formed by a ring  118 B on sleeve  116 B, which also includes a cannulation  30 B, and is easier to see in  FIG. 8C . 
     The sleeve  116 A has two cross-cuts along its length to form four slots  117 A passing through and extending from ring  118 A along sleeve  116 A a substantial distance towards end face  22 A. Four sections of a spring collet are thus formed out of male connector  114 A wherein the sections of the collet can be compressed together towards the center axis of sleeve  118 A and will spring back to their original position with removal of the compressive force. Male connector  114 A can then be used to couple bellows  14 D to a female connector or coupling  115  integrally formed as the proximate end portion of a threaded anchoring member  122 , as best seen in  FIGS. 8A and 8B . Anchoring member  122  is used twice in this embodiment and for the operation of the embodiment one of the members  122 ,  122  is positioned at each end of bellows  14 D. Anchoring members  122 ,  122  may be made from shape memory metal though it is not absolutely necessary because they need not undergo any change in its shape. Therefore they may be made from a material that is compatible with the shape memory alloy to avoid any corrosion and should also be biocompatible for implantation into a human or animal body. For instance, if bellows  14 D is made from a nickel-titanium shape memory alloy, then members  122 ,  122  may be of titanium and therein fit the aforementioned criteria. Members  122 ,  122  could also be made from a biocompatible polymer that may or may not be bioabsorbable. 
     As shown best in  FIGS. 8A and 8B , each member  122  has a cylindrical body  128  and its female connector  115  has an end face  127 . Male connector  114 B is used to couple bellows  14 D to the second member  122  by engaging its female connector or coupling  115  integrally formed as its proximate end portion as best seen in  FIG. 8C . A central longitudinal cylindrical cavity  124 , as seen best in  FIGS. 8C and 8D , extends longitudinally into body  128  of members  122 ,  122  through the end face  127 . Passing axially through body  128  is a cannulation  140  to allow passage of guide wire  34 . Cavity  124  has an internal diameter and length to accommodate male connectors  114 A and  114 B. To allow for coupling to occur, cavity  124  has a circular recess  126  set radially around its inner wall. It is positioned and extends substantially along the circumference of the wall of the cavity opposite end face  127 . Collars  119 A and  119 B of rings  118 A and  118 B, respectively, will snap into recesses  126 ,  126  when male connectors  114 A and  114 B are inserted forcefully into cavities  124 ,  124 . Upon insertion of male connectors  114 A,  114 B into cavities  124 ,  124 , the internal wall of these cavities will maintain the sections of the spring collets compressed together until collars  119 A,  119 B reach recesses  126 ,  126 . Thereat, rings  118 A,  118 B seat themselves into recesses  126 ,  126  locking together the bellows  14 D and the two threaded members  122 ,  122 . 
     Bellows  14 D and male connectors  114 A and  114 B are generally all made from the shape memory metal, although the male connectors themselves are not cold deformed and therefore do not undergo a shape memory change. There is motion across the male connectors when the spring collet is compressed by the internal diameter of anchoring member  122  but this is due to force applied on the spring collet and not action of the shape memory metal. However, collars  119 A and  119 B could be designed to change shape. For example, the collar could be designed such that in the austenite phase, the collar is angled or bent axially in the direction of bellows  14 D. In the martensite phase, the collar would be in a position where it is angled axially away from the bellows. Then, upon implantation into the body and warming of the metal, phase change from martensitic back to austenitic would cause collars  119 A and  119 B to change its shape. This would cause the collars to bend or angle back toward their original positions, directed substantially in the direction of the bellows. When bellows  14 D is coupled to member  122 , the phase change in the collar would help to further pull together the two devices, adding to the compression provided by the fastener. 
     When anchoring members  122 ,  122  and bellows  14 D are coupled together, cannulations  140 ,  140  are axially aligned with the bellows chamber  16 D as shown best in  FIGS. 8B and 8E .  FIGS. 8A ,  8 C, and  8 F show that at the end of member  122  adjacent to end face  127 , there extends along the female coupling portion of body  128  in a direction opposite to end face  127  a tool receiving surface  130  for engagement by a tool such as a screw driver having a correspondingly shaped receptacle or cannulation. The outer perimeter of surface  130  has a hexagonal cross-sectional shape in this embodiment, although square, tom or cruciate cross sectional shapes would also be acceptable as these are other common shapes for screwdrivers available in an operating room. In this embodiment with the hexagonal shaped tool surface  130 , a screwdriver (not shown) with a hexagonal receptacle may be slid over surface  130  for the purposes of turning member  122  axially into a bone. Member  122  includes a thread or plurality of threads  134  formed around a body  128  and extending the length of body  128  from the inner end of the surface  130  opposite end face  127  to the end face  129  at the opposite end of body  128 . These threads are for anchoring member  122  into a middle or proximal phalanx. As stated earlier, member  122  does not go through a shape change and therefore does not necessarily need to be made from a shape memory metal. 
     However, member  122  can be made from a shape memory metal which would allow some modifications of the anchoring method into bone. For instance, instead of body  128  having threads  134 , the body could have barbs, similar to the prior embodiments, that expand when implanted into a proximal or middle phalanx or other substrate. Male connector  114 A of bellows  14 D would then be inserted into cavity  124  and coupled with member  122 , effectively achieving the same goal. Other anchoring methods could be used as well. Two different types of screws could be used or two members that are only differentiated by the thread patterns going in opposite directions. One screw would be screwed into the bone clockwise, the other counterclockwise. Furthermore, as alternatives to these designs, bellows  14 D can be made in a similar angular manner as that shown for bellows  14 B in  FIG. 6A  or bellows  14 C of  FIG. 7B . 
     Other coupling arrangements besides the spring collet design could also be used to join together anchoring members  122 ,  122  and bellows  14 D. A strike-and-latch type coupling mechanism or push-lock mechanism could be employed in the design as well for any of the embodiments hereinafter described. Also, although the male couplings  114 A and  114 B and the female couplings  115 ,  115  are not designed to be detachable after being joined, other coupling arrangements designed to be detachable after joinder are well known in the coupling art. In addition, the coupling mechanisms of other coupling arrangements could have shape memory capabilities as described above for the collars  119 A and  119 B on the spring collets of this embodiment. 
     Operation of Fourth Embodiment 
     As seen in  FIGS. 5A and 5B , the joint surfaces of proximal phalanx  42  and middle phalanx  46  are again prepared as previously described for the first embodiment. The cut surfaces  78  and  74  are prepared so that their surfaces are perpendicular to the long axis of the bones. Herein again guide wire  34  is driven axially into proximal phalanx  42  using wire driver  38 . A counter-borer, as in the first embodiment in  FIG. 5C , that matches the thread root diameter of member body  128  is placed over guide wire  34  and used to make matching bore holes in proximal phalanx  42  and middle phalanx  46 . The counter-borer is removed from the guide wire. Member  122  is then placed over guide wire  34  followed by a screwdriver (not shown) having a hexagonal shaped cannulation. This screwdriver is then mated with tool surface  130 , shown best in  FIG. 8A , and then member  122  is screwed into proximal phalanx  42  to appropriate depth. A similar procedure is then performed on middle phalanx  46  and a second member  122  is screwed into middle phalanx  46 . 
     Refrigerated bellows  14 D is now manually implanted into the proximal phalanx  42  and the middle phalanx  46  per the following. Male connector  114 A, again shown best in  FIGS. 8A and 8D , is pushed into cavity  124 . The spring collet is compressed by the walls of cavity  124  until collar  119 A of ring  118 A slips into recess  126 , locking male connector  114 A and bellows  14 D to member  122 . Proximal phalanx  42  and middle phalanx  46  are grasped by the surgeon&#39;s hands, just as in the main embodiment, and male connector  114 B is manually inserted into cavity  124  of the second member  122  in middle phalanx  46 . Again collar  119 B of ring  118 B snaps into recess  126  locking together bellows  14 D and the second member  122 . At this point, bellows  14 D is connected on both its ends to a member  122  in proximal phalanx  42  and a member  122  in middle phalanx  46 .  FIG. 8F  shows fastener  10 D as assembled with bellows  14 D situated between the two anchoring members  122  and coupled together with them. The fastener is shown here in its austenite phase with bellows  14 D contracted and shortened. 
     As the temperature of shape memory bellows  14 D increases to body temperature, it undergoes a change in shape from its annealed elongated martensite phase to its shortened austenite phase, drawing together surface  78  of proximal phalanx  42  and surface  72  of middle phalanx  46 .  FIG. 9  shows fastener  10 D implanted into a PIPJ and in its austenite phase. After the two surfaces become compressed, the surgeon may then decide whether he or she needs to place proximal end  100  of guide wire  34  across MTPJ  64 , and leave it within fastener  10 D, or remove guide wire  34  entirely from the fastener and the toe. Wire driver  38  is used to place the guide wire in the appropriate position. After removal of the guide wire, the surgeon then closes the wound utilizing a standard surgical technique. 
     Fifth Embodiment 
     Another alternative embodiment is shown in  FIG. 10  wherein the embodiment shows combinations of components of the previous embodiments. Here, fastener  10 E has a sleeve  18 E which extends axially outward from bellows  14 E. Again barbs  26  are substantially positioned outward from the bellows along the length of sleeve  18 E. At the end of bellows  14  E opposite the sleeve  18 E extending axially is a male connector  114 E. Cannulation  30 E passes along the internal central axis of the sleeve and bellows. A member  122  is the same as described in the fourth embodiment. Member  122  may be made from a shape memory metal alloy, shape memory polymer, or other biocompatible alloy or polymer. 
     Male connector  114 E has similar design and makeup as male connectors  114 A and  114 B from the fourth embodiment. Male connector  114 E has two cross-cuts  117 E down its length to form four sections of a spring collet. At the end of male connector  114 E is collar  119 E which engages the internal diameter of member  122  as described for the fourth embodiment. The collar may have shape memory action as previously described or may be made without it and the collar and the entire male connector may or may not be made from shape memory materials. The action of the male connector is likewise the same as previously described for the fourth embodiment. Here again the coupling mechanism of this embodiment need not be based on a spring collet design. A strike and latch mechanism or a push-lock mechanism, either one with or without shape memory action, could be employed to achieve coupling of screw member  122  to bellows  14 E of the fastener  10 E. Also, as shown in prior embodiments, the present embodiment and all others to follow may be angular in design to allow a joint to be fused in a position other than straight. 
     Operation of Fifth Embodiment 
     In using fastener  10 E, the bones of a toe are prepared as previously described in  FIGS. 5A and 5B . Here again a guide wire  34  is driven axially into proximal phalanx  42  using a wire driver  38 . A counter-borer, as in the first embodiment in  FIG. 5C , that matches the thread root diameter of member body  122  is placed over guide wire  34  and used to make a bore hole  110  in proximal phalanx  42 . The counter-borer is removed from the guide wire. Member  122  is then placed over guide wire  34  followed by a screwdriver having a hexagonal shaped cannulation to fit over the tool surface  130  of member  122 . This screwdriver is then mated with tool surface  130  and then member  122  is screwed into proximal phalanx  42  to appropriate depth. Next the guide wire is placed into middle phalanx  46  and a counter-borer is used to create a matching bore hole  111  in abutment surface  74  of the middle phalanx. 
     Refrigerated bellows  14 E is now manually implanted into the proximal phalanx  42 . Male connector  114 E is pushed into cavity  124  of member  122 . The spring collet is compressed by the walls of cavity  124  until collar  119 E slips into recess  126  of member  122 , locking male connector  114 E and bellows  14 E to member  122 . Proximal phalanx  42  and middle phalanx  46  are grasped by the surgeon&#39;s hands, just as in the main embodiment, and sleeve  18 E of the fastener is slid into matching bore hole  111  in middle phalanx  46 . The two abutment surfaces are brought together and the bellows is warmed by body heat. This allows the bellows and the barbs to change shape. The barbs expand radially outward into the surrounding bone and the bellows contracts axially to compress the abutment surfaces together. 
     Sixth Embodiment 
       FIG. 11  shows another embodiment where again there is a single construct for implantation into bone. A fastener  1  OF is shown having components of the previous embodiments. A bellows  14 F is again noted centrally along the axis of fastener  10 F. Extending axially outward away from bellows  14 F is again an integral sleeve  18 F with barbs  26 . Extending axially outward away from bellows  14 F opposite sleeve  18 F is screw member  122 F. Member  122 F has threads  134 F extending inward from its end substantially toward bellows  14 F. In this embodiment, however, screw member  122 F is attached to bellows  14 F either directly or via a small arm  147  situated between the bellows and body. Again, sleeve  18 F, bellows  14 F, arm  147 , and body  122 F are all generally axially aligned and there is a longitudinal central cannulation  30 F to the entire fastener as noted in the first embodiment. Situated substantially opposite barbs  26  and adjacent bellows  14 F, sleeve  18 F is modified into a tool surface  131 . Tool surface  131  is generally hexagonal shaped to allow a hex screwdriver to slide over sleeve  18 F and engage the tool surface. A screwdriver may then be used to turn the entire fastener  10 F to first drive screw member  122 F into a bone. 
     Being a single construct, the entire fastener  10 F is preferably made of a shape memory alloy though it is still possible that screw member  122 F could be made of a non-shape memory metal like titanium. The screw part and the bellows part could be integral or instead made independently and then welded together to form a single construct. Again, this embodiment may also be made angularly instead of straight as set forth in prior embodiments. Conceivably the sleeve end of fastener  10 F could be made as a separate piece from bellows  14 F. A coupling arrangement as previously described, say a spring collet mechanism, a push-lock mechanism or a strike and latch mechanism, could then be used as a way of joining together the barbed sleeve  18 F and bellows  14 F with its attached screw member  122 F after both segments of the embodiment have been separately implanted into the bones to be fused. 
     As with embodiments one to five above, an angularity could be imparted to this sixth embodiment so that the bones to be fused are set at an angle to one another. Also, the entire construct need not necessarily be entirely made up of shape memory metal or polymer as long as the parts of the embodiment needing to undergo a shape change are made of shape memory material. As previously indicated, when the fasteners described above change shape from an extended state to a contracted state upon being heated, they are considered to be heat responsive and may be referred to as heat responsive fasteners. 
     Operation of Sixth Embodiment 
     In using fastener  10 F, the bones of a toe are prepared as previously described in  FIGS. 5A and 5B . Here again a guide wire  34  is driven axially into proximal phalanx  42  using a wire driver  38 . The counter-borer matches the thread root diameter of member body  122 F. It is placed over guide wire  34  and used to make a bore hole  110  in proximal phalanx  42 . The counter-borer is removed from the guide wire. Fastener  10 F is then placed over guide wire  34  followed by a screwdriver having a hexagonal shaped cannulation to fit over the tool surface  131  of fastener  10 F. This screwdriver is then mated with tool surface  131  and the entire fastener  10 F, not just body  122 F, is screwed into proximal phalanx  42  to appropriate depth. Next the guide wire is removed and placed into middle phalanx  46  and a counter-borer is used to create a matching bore hole  111  in abutment surface  74  of the middle phalanx that will match the half of fastener  1  OF that encompasses sleeve  18 F and barbs  26 . Proximal phalanx  42  and middle phalanx  46  are grasped by the surgeon&#39;s hands, just as in the main embodiment, and sleeve  18 F of the fastener is slid into matching bore hole  111  in middle phalanx  46 . The two abutment surfaces are brought together and the bellows is warmed by body heat. This allows the bellows and the barbs to change shape. The barbs expand radially outward into the surrounding bone and the bellows contracts axially to compress the abutment surfaces together. 
     Seventh Embodiment 
       FIG. 12  shows an embodiment similar in appearance to the fourth embodiment. The most notable difference in a fastener  10 G are integral screws  200  and  202  solidly attached to each end of a bellows  14 G wherein screws  200  and  202  have oppositely handed thread patterns to each other. Screw  200  has an end face  209  set on the end of the screw opposite the direction of the centrally positioned bellows  14 G. A set of threads  201  extending inwardly from end face  209  surrounds the periphery of screw  200 . Threads  201  are left hand turning in their operation. A set of threads  203  extending inwardly from an end face  210  surrounds the periphery of screw  202 . Threads  202  are right hand turning in their operation. An arm  207  connects screw  200  to bellows  14 G whereas an arm  206  connects screw  202  to bellows  14 G. Screw  200 , arm  207 , bellows  14 G, arm  206 , and screw  202  are all axially aligned. Fastener  10 G has a cannulation  300  running centrally down the long axis of the fastener for passage of a guide wire as in prior embodiments. The cannulation extends from end face  209  of screw  200  to end face  210  of screw  202 . The circumference of the central pleat of bellows  14 G is modified into a hexagonal shaped tool surface  214 , or hex nut, dividing the bellows in half. Each half of the bellows is integrally connected to each side of the hex shaped tool surface  214 . 
     Bellows  14 G is again preferably made entirely of a shape memory material but those parts that do not undergo shape change do not necessarily need to be. Since the tool surface  214  does not undergo a change in its shape, it could be made from an alternative biocompatible alloy or metal and the two halves of the bellows may be welded to it. Screws  200  and  202  also could be made from a metal or alloy other than a shape memory alloy since this portion of the embodiment also need not undergo a shape change. These too could be welded to the bellows directly or via arms  207  and  206 . As with the previously described embodiments, when the bellows changes shape from an extended state to a contracted state upon being heated, the fastener is considered to be heat responsive and may be referred to as a heat responsive fastener. 
     Though  FIG. 12  represents an embodiment where screws  200  and  202  are solidly attached, conceivably a mechanism could be used for detachably coupling the screws to the bellows. Here a strike and latch coupling mechanism may be appropriate or some similar design such that the coupling mechanism permits the transfer of torque to screws  200  and  202 , described below in the operation of fastener  10 G. If the screws are not integral to the bellows, then they could be made from a biocompatible polymer which could again be detachably coupled to the bellows  14 G. 
     Operation of Seventh Embodiment 
     Placing the embodiment across the PIPJ for joint fusion is not unlike the prior embodiments. The joint surfaces are again prepared as before. A guide wire and counter-borer are again used in the proximal phalanx and a matching bore hole is made. Again, one end of fastener  10 G is slid over the guide wire in the proximal phalanx and placed inside the phalanx. The guide wire is then removed and directed into the middle phalanx and out the end of the toe. A matching bore hole is then made in the middle phalanx. The middle phalanx is then slid over the other end of the fastener and the guide wire allowed to slide down cannulation  30 G. Once the fastener is in position spanning the joint space, the design and operation of the embodiment is such that the hexagonal tool surface is centrally aligned over the joint space with the screws and bellows inside the bones. There is some space or gapping between the abutment surfaces of the proximal and middle phalanx. A hex shaped wrench is then placed over the hex tool surface  214  and used to turn the fastener. This transmits torque to screws  200  and  202  such that, coupled with the action of the left and right hand screws, turning the fastener in only one direction drives both of the screws into the respective bones thereby embedding them therein and anchoring them into the phalanges. This then draws the proximal and middle phalanx closer together. The hex wrench is then removed and the shape change of bellows  14 G, upon warming up, completes the process of compressing together the abutment surfaces of the proximal and middle phalanx. Subsequently the surgeon may then decide whether to drive the guide wire across the MTPJ, leave it where it is, or remove it altogether prior to closure of the surgical wound.