Patent ID: 12256964

DETAILED DESCRIPTION

Shape memory K-wires and methods of use are disclosed that address challenges of existing hammertoe devices and procedures. A shape memory K-wire can comprise a malleable distal end, while the remaining portion of the K-wire is superelastic at room temperature. In use, a surgeon can use a nitinol K-wire to stabilize an osteotomy site. A proximal superelastic region will spring back to its original position after being bent while positioned in a joint of a patient, while the malleable region allows a surgeon to easily cut and crimp this distal end of the K-wire. The shape memory K-wire can be left in the bone for 3 to 6 weeks while the osteotomy heals. Post-surgery (e.g., 3 to 6 weeks), a surgeon can retract the nitinol K-wire out of the distal end of the toe, leaving no metal hardware behind in the patient. In another embodiment, a shape memory K-wire can be used during a procedure to guide a cannulated hammertoe implant into a joint. An implant is intended to stay in the patient in perpetuity, while the shape memory K-wire is either withdrawn during the procedure or retracted from the patient at a later time.

FIG.1illustrates an apparatus100comprising a wire102having a first end104and a second end106opposite the first end104. A first portion108of the wire102including the first end104comprises a malleable region110that is configured to remain deformed after bending. In one example, the malleable region110comprises the entirety of the first portion108of the wire102. In another example, the malleable region110comprises a subset of the first portion108of the wire102. A modulus of elasticity of the malleable region110of the wire102may be about 28 GPa to about 40 GPa (e.g., about 28, 30, 32, 33, 34, 36, 38, or 40 GPa).

A second portion112of the wire102including the second end106comprises a superelastic region114that is configured to return to a straight configuration after bending. As such, the second portion112may comprise an austenitic region of the wire102. The superelastic region114of the wire is superelastic at room temperature. In one example, the superelastic region114comprises the entirety of the second portion112of the wire102. In another example, the superelastic region114comprises a subset of the second portion112of the wire102. A modulus of elasticity of the superelastic region114may be about 40 GPa to about 80 GPa (e.g., about 40, 45, 50, 55, 60, 65, 70, 75, or 80 GPa).

In use, as shown inFIG.2and as discussed in additional detail below, any of the disclosed embodiments can be used in a hammertoe procedure and can be positioned in a digit115of a patient, more particularly across a joint of a toe of the patient. In an example, a second portion112, which includes a superelastic region114including a second end106, is positioned in the digit115of the patient and a first portion108, which includes a malleable region110including a first end104, extends out of the digit115of the patient. In an embodiment, the apparatus100can then be left in the patient post-surgery (e.g., 3-6 weeks) to provide temporary support while the joint is healing.

A superelastic region114of a wire102allows a second portion112of the wire102positioned in the patient to bend in response to movement of the patient post-surgery, but will snap back to its straight configuration due to its superelastic properties as illustrated inFIG.3. Such a configuration prevents permanent deformation of a second portion112of a wire102that is positioned in the patient, which can negatively affect the healing process of a joint. In addition, such a configuration keeps a second portion112of a wire102substantially straight, which makes removal of the apparatus from the patient easier. A malleable region110of the wire102allows a surgeon to cut and optionally crimp a first end104of the wire102to thereby prevent the wire102from sliding along the joint after the procedure. In another example, the surgeon may cut off a portion of the malleable region110of the wire102and leave the remaining malleable region110of the wire102substantially straight.

A wire102may comprise a shape memory alloy. The shape memory alloy may comprise a Ni—Ti alloy, or a Cu—Al—Ni—Mn alloy, as non-limiting examples. In one particular example, the wire102comprises Nitinol, which is a Ni—Ti alloy. A number of different Nitinol raw materials can be used for a wire102in order to optimize and achieve the desired characteristics (e.g., strength, transition temperature) of the wire102. A wire102can comprise Nitinol of varied ultimate tensile strengths, % elongation, loading and unloading plateaus, and austenite finishing temperatures.

In addition, Nitinol has a modulus of elasticity (˜40 GPa to 80 GPa) more comparable to bone (˜15 GPa) than stainless steel (˜200 GPa). Moreover, Nitinol's hysteresis (stress/strain curve) is more similar to human tissue than stainless steel. Superelastic Nitinol will allow the phalanges to flex in a more physiologically naturally manner than the stiffer stainless steel. Therefore, use of a Nitinol wire for a hammertoe procedure limits the potential for stress shielding and can result in better rates of proximal interphalangeal fusion healing.

A length of the first portion108of the wire102can be less than a length of the second portion112of the wire102. In one particular example, a ratio of the length of the first portion108of the wire102to the length of the second portion112of the wire102can be about 6:1 to about 1:6, for example from about 3:1 to about 1:3. The length of the first portion108of the wire102can be about 10 mm to about 600 mm, and the length of the second portion112of the wire102can be about 10 mm to about 300 mm.

A diameter of the wire102can be about 0.7 mm to about 4.0 mm (e.g., about 0.7, 0.8, 0.9, 1.0, 1.1, 1.5, 2.0, 2.5, 3.0, 3.5, or 4.0 mm). The superelastic characteristics of the wire102can result in better fatigue resistance than a traditional stainless steel K-wire of the same size. Better resistance to fatigue, in turn, equates to less susceptibility to plastic deformation. Therefore, it is possible to achieve better resistance to plastic deformation with a smaller (e.g., 1.1 mm) wire than with a larger (1.6 mm) stainless steel K-wire. A smaller shape memory alloy K-wire diameter can result in bone preservation at the surgical site. In addition, a smaller diameter wire can increase the ability for the wire102to receive various hammertoe implants. For example, the wire102can have a 1.1 mm diameter, and therefore can be able to accept a hammertoe implant101such as a DynaNite® Hammertoe Implant (FIG.4). In an example, a diameter of the first portion108of the wire102is the same as a diameter of the second portion112of the wire102. In another example, a diameter of the first portion108of the wire102is different than a diameter of the second portion112of the wire102.

A malleable region110of a wire102can be created through a variety of processes. In an example, a malleable region110of a wire102is created through differential heat treatment during the manufacturing process. In one particular example, a differential heat treatment process comprises heating a first portion108of a wire102very quickly to red-hot and then rapidly cooling (e.g., quenching), turning only the first portion108into a malleable form but leaving a second portion112of the wire102in its unchanged superelastic form. In another example, a malleable region110of a wire102is created through ablation of the nickel content of a first portion108of the wire102. For example, an approximate 0.1% decrease in Nitinol's nickel alloy composition can equate to a change between about 20° C. to about 40° C. in austenitic finish transformation temperature. In one particular example, about 0.05% of the nickel from a first end104of a wire102can be ablated away, which will correspondingly increase the martensitic start and austenitic finish temperatures a malleable region110of the wire102. Such an ablation method is a precise method of controlling the length of a malleable region110of a wire102. A transition region between a malleable region110and a superelastic region114of the wire102can be non-existent (i.e., the malleable region110transitions to the superelastic region114without any region between them that exhibit blended properties) or the transition region between the malleable region110and the superelastic region114can be as long as the malleable region110itself, and exhibit properties of both regions.

In another example, a malleable region110of a wire102is created by processing the first portion108in a fully annealed condition, such that it will be completely malleable and have no superelastic or shape memory response with any temperature change. Annealing is a process of removing all residual stresses that were a result of cold work during the manufacturing process using high heat. Such an annealing process removes all superelasticity and shape memory properties of cold-worked Nitinol. In another example, partial annealing can be performed at a lower temperature and for specified amounts of time and will remove some, but not all of the residual stress and thus results in an increase in Afand altering of the original tensile properties.

In an example, a first portion108of the wire102can have an austenitic start temperature greater than 22° C. (e.g., 22, 23, 24, 25, 26, 27, 28, 29, 30° C. or more). Thereby, a first portion108can be malleable when positioned outside of the body in ambient air. Then a second portion112of a wire102can have an austenitic finish temperature less than 37° C. (e.g. 37, 36, 35, 34, 33, 32, 31° C., or less). In particular, the austenitic finish temperature of a second portion112of a wire102can be about −5° C. to about 26° C. (e.g., about −5, −4, −3, −2, −1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, or 26° C.). Thus, a second portion112can be superelastic when positioned in the body. A loading plateau of a first portion108of a wire102can be less than about 45 ksi (e.g., 45, 44, 43, 42, 41, 40, 35, 30 ksi or less), and a loading plateau of a second portion112of a wire102can be about 55 ksi to about 80 ksi (e.g., about 55, 60, 65, 70, 75, or 80 ksi).

In an example, as shown inFIG.1, an apparatus100can also include a transition zone marker116positioned on a transition region of the wire102between a first portion108and a second portion112of the wire102. The transition zone marker116can comprise a brightly colored band that provides a visual indication for the surgeon on where the superelastic region114transitions to the malleable region110, thereby enabling the surgeon to know where to cut and optionally crimp the malleable region110after positioning the superelastic region114of the wire102in the patient. In another example, a first portion108of a wire102includes one or more measurement markings118indicating a length of the first portion108. Such an arrangement may provide an indication of the depth of the wire102in the patient.

In another example, a first portion108of a wire102and/or a second portion112of a wire102includes a marker120A,120B. Such a marker may take a variety of forms, including a radio-opaque marker, a laser marking, or a color coating, as non-limiting examples. In one particular example, an entirety of the malleable region110may be coated a different color than the rest of the wire102. In another particular example, a first portion108of a wire102includes a first a radio-opaque marker120A visible under fluoroscopy, and a second portion112of the wire102includes a second a radio-opaque marker120B visible under fluoroscopy (for example, Platinum or Tantalum). Such a configuration enables the surgeon to view the respective regions of the apparatus100as they are positioned in the patient. In one example, the first radio-opaque marker120A is the same as the second radio-opaque marker120B. In another example, a first radio-opaque marker120A is different than a second radio-opaque marker120B. In another example, only a first portion108of a wire102includes a radio-opaque marker120A. In another example, only the second portion112of a wire102includes a radio-opaque marker120B.

A first end104and/or a second end106of the wire102can comprise a sharp tapered end to help with positioning the apparatus100across a joint of the patient, as shown inFIG.1. In one particular example, the first end104and/or the second end106of the wire can be pyramidal in shape, providing three or more cutting edges where each face joins and adjacent face. In another example, the first end104and/or the second end106of the wire102can be threaded to enable attachment of additional components having complementary threads. In another example, the first end104and/or the second end106of the wire102can be blunt.

FIGS.5A-5Cillustrates another embodiment of an apparatus200. InFIG.5A, the apparatus200comprises a wire202having a first end204and a second end206opposite the first end204. A first portion208of the wire202including the first end204comprises a shape set superelastic region210. In an example, the wire202can be manufactured entirely of superelastic nitinol, and can have a first end204that is shape set in a bent configuration. The shape set superelastic region210is then straightened in a constrained condition when a sleeve212is positioned over the first end204of the wire202, as shown inFIG.5A. Once the constraint of the sleeve212is removed as illustrated inFIG.5B, the shape set bent shape can be recovered. This as-manufactured shape of a first portion208of a wire202will specifically conform to the desired post-surgical shape. Namely, a first end204of the wire202can be bent upwards at the point that will extrude beyond the tip of the digit214. As such, the shape set superelastic region210of the wire202has a non-zero angle with respect to a second portion216of the wire202when a first portion208of the wire202is in an unconstrained state.FIG.5Cillustrates a wire202in an unconstrained state after the wire202has been positioned in a digit214of a patient.

A second portion216of the wire202including the second end206comprises a straight superelastic region218that is configured to return to a straight configuration after bending. Such a configuration prevents permanent deformation of the wire202in a patient, which can negatively affect the healing process of the joint as discussed above. In addition, such a configuration keeps a second portion216of a wire202substantially straight, which makes removal of the apparatus200from the patient easier.

An apparatus200as disclosed herein can also include a sleeve212having a lumen213. The sleeve212can be made from aluminum, steel, or titanium as non-limiting examples. A first portion208of a wire202can be removably positioned at least partially in the lumen213of the sleeve212. A first portion208of a wire202is in a constrained state when the first portion208of the wire202is positioned at least partially in the lumen213of the sleeve212. A first portion208of a wire202can be substantially straight in the constrained state. In particular, a longitudinal axis of a first portion208of a wire202can be coaxial with a longitudinal axis of a second portion216of the wire202when the first portion208of the wire202is in the constrained state, as shown inFIG.5A. A first portion208of a wire202can be in an unconstrained state when the first portion208of the wire202is removed from a lumen213of a sleeve212. A first portion208of a wire202can have a non-zero angle with respect to a second portion216of a wire202in the unconstrained state, as shown inFIG.5B. In particular, a longitudinal axis of a first portion208of a wire202can have a non-zero angle with respect to a longitudinal axis of a second portion208of a wire202when the first portion208of the wire202is in the unconstrained state.

In an example, a diameter of a lumen213of a sleeve212is adjustable. As such, the sleeve212can transition from a first diameter where the lumen213of the sleeve212contacts a wire202to hold a first portion208of the wire202in the constrained state, to a second larger diameter that enables the first portion208of the wire202to be removed from the lumen213of the sleeve212to transition the first portion208of the wire202to the unconstrained state.

The wire202of the apparatus200of, for example,FIGS.5A-5Ccan be similarly configured to the wire102of the apparatus100of, for example,FIG.1. In particular, a length of a first portion208of a wire202can be less than a length of a second portion216of the wire202. In one particular example, a ratio of the length of a first portion208of a wire202to the length of a second portion216of the wire202can be about 6:1 to about 1:6, for example from about 3:1 to about 1:3. The length of a first portion208of a wire202can be about 10 mm to about 100 mm, and the length of a second portion216of the wire202can be about 10 mm to about 100 mm.

A diameter of a wire202can be about 0.7 mm to about 4 mm (e.g., about 0.7, 0.8, 0.9, 1.0, 1.1, 1.5, 2.0, 2.5, 3.0, 3.5, or 4.0 mm). In an example, a diameter of a first portion208of a wire202is the same as a diameter of a second portion216of the wire202. In another example, a diameter of a first portion208of a wire202is different than a diameter of a second portion216of the wire202.

In an example, a first portion208of a wire202includes one or more measurement markings220indicating a length of the first portion208of the wire202. Such an arrangement may provide an indication of the depth of the wire202in the patient. In another example, a first portion208of a wire202and/or a second portion216of a wire202includes a marker222A,222B. Such a marker may take a variety of forms, including a radio-opaque marker, a laser marking, or a color coating, as non-limiting examples. In one particular example, an entirety of a first portion208of a wire may be coated a different color than the rest of the wire202. In another particular example, a first portion208of a wire202includes a first a radio-opaque marker222A visible under fluoroscopy, and a second portion216of the wire202includes a second a radio-opaque marker222B visible under fluoroscopy (for example, Platinum or Tantalum). Such a configuration enables the surgeon to view the respective regions of the apparatus200as they are positioned in the patient. In one example, the first radio-opaque marker222A is the same as the second radio-opaque marker222B. In another example, a first radio-opaque marker222A is different than a second radio-opaque marker222B. In another example, only a first portion208of a wire202includes a radio-opaque marker222A. In another example, only a second portion216of a wire202includes a radio-opaque marker222B.

A first end204and/or a second end206of a wire202can comprise a sharp tapered end to help with positioning the apparatus across a joint of the patient. In one particular example, a first end204and/or a second end206of a wire202can be pyramidal in shape, providing three or more cutting edges where each face joins and adjacent face. In another example, a first end204and/or a second end206of a wire202can be threaded to enable attachment of additional components having complementary threads. In another example, a first end204and/or a second end206of a wire202can be blunt.

In operation, an example method can include (a) introducing a second end106of a wire102into a joint, wherein a superelastic portion114of the wire102including the second end106is configured to return to a straight configuration after bending to thereby maintain the joint in a straightened position, and (b) cutting a first end104of the wire102. A wire102can be introduced following removal of one or more portions of a joint in a toe of a patient. The methods can result in straightening the joint.

In one example, the first end104of the wire is superelastic such that the entirety of the wire102is superelastic. In another example, the first end104of the wire is malleable. In such an example, an embodiment of the methods can further include bending the malleable first end110of the wire102to permanently deform the first end104such that the malleable first end110of the wire102has a non-zero angle with respect to the superelastic second end114of the wire102. The methods can further include positioning a second end106of a wire102through a lumen in a hammertoe implant101, and positioning the hammertoe implant101in a joint prior to cutting a first end104of the wire102. The methods can further include removing the wire102from the joint. In one particular example, the wire102is removed from the joint after 3-6 weeks.

In one example, when the apparatus100is positioned in the patient, the entire malleable region110of the first portion108of the wire102is outside of the body of the patient. In another example, when the apparatus100is positioned in the patient, a portion of the malleable region110of the first portion108of the wire102remains inside of the body of the patient. In yet another example, when the apparatus100is positioned in the patient, the entire malleable region110of the first portion108of the wire102is positioned distal to a distalmost joint of the patient though which the wire102is positioned.

Another example method can include (a) introducing a second end206of a wire202into a joint, wherein a straight superelastic region218including the second end206of the wire202is configured to return to a straight configuration after bending to thereby maintain the joint in a straightened position, and (b) removing a first end204of the wire202from a lumen213of a sleeve212to transition the wire202from a constrained state to an unconstrained state, wherein the first end204of the wire202has a non-zero angle with respect the second end206of the wire202in the unconstrained state. A wire202also can be introduced following removal of one or more portions of a joint in a toe of a patient. The methods can result in straightening the joint.

The methods can further include positioning a second end206of a wire202through a lumen in a hammertoe implant101, and positioning the hammertoe implant101in a joint. The method can also include removing the wire202from the joint. In one particular example, the wire202is removed from the joint after 3-6 weeks.

In one example, when the apparatus200is positioned in the patient, the entire shape set superelastic region210of the first portion208of the wire202is outside of the body of the patient. In another example, when the apparatus200is positioned in the patient, a portion of the shape set superelastic region210of the first portion208of the wire202remains inside of the body of the patient. In yet another example, when the apparatus200is positioned in the patient, the entire shape set superelastic region210of the first portion208of the wire202is positioned distal to a distalmost joint of the patient though which the wire202is positioned.

As used herein, with respect to measurements, “about” means +/−10%.

As used herein, “substantially straight” means a structure having a radius of curvature less than 5°.

Unless otherwise indicated, the terms “first,” “second,” etc. are used herein merely as labels, and are not intended to impose ordinal, positional, or hierarchical requirements on the items to which these terms refer. Moreover, reference to, e.g., a “second” item does not require or preclude the existence of, e.g., a “first” or lower-numbered item, and/or, e.g., a “third” or higher-numbered item.

As used herein, apparatus, element and method “configured to” perform a specified function is indeed capable of performing the specified function without any alteration, rather than merely having potential to perform the specified function after further modification. In other words, the apparatus, element, and method “configured to” perform a specified function is specifically selected, created, implemented, utilized, programmed, and/or designed for the purpose of performing the specified function. As used herein, “configured to” refers to existing characteristics of an apparatus, element, and method which enable the apparatus, element, and method to perform the specified function without further modification. For purposes of this disclosure, an apparatus, element, and method described as being “configured to” perform a particular function can additionally or alternatively be described as being “adapted to” and/or as being “operative to” perform that function.

As used herein, “first end” refers to the end that will be a “distal end” relative to an operator of the apparatus.

As used herein, “second end” refers to the end that will be a “proximal end” relative to an operator of the apparatus.

As used herein, “lumen” refers to a passage within a structure having a diameter sized to receive a wire therethrough.

As used herein, “austenite start temperature” is the temperature at which the martensite to austenite transformation begins on heating of an alloy.

As used herein, “austenite finish temperature” is the temperature at which martensite to austenite transformation is completed on heating of an alloy.

As used herein, “constrained state” refers to when the apparatus is disposed in or partially with a sleeve and is substantially straight.

As used herein, “unconstrained state” refers to when the apparatus has been positioned in the patient and is unsheathed from a sleeve.

As used herein, “loading plateau” means a region after a first yield point, where several percent strain can be accumulated with only a small stress increase. The end of the loading plateau is reached at about 8% strain. After that, there is another linear increase of stress with strain. Unloading from the end of the plateau region, causes the stress to decrease rapidly until an unloading plateau is reached where several percent strain is recovered with a minimal decrease in stress.

As used herein, “shape set” means resetting a shape of the wire or base material to a new, desired shape, with the same mechanical properties. The wire or base material will return to the new, desired shape in the absence of outside forces acting on the wire or base material.

It will be appreciated that other arrangements are possible as well, including some arrangements that involve more or fewer steps than those described above, or steps in a different order than those described above.

While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. All embodiments within and between different aspects of the devices and methods can be combined unless the context clearly dictates otherwise. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the claims.