Barbed orthopedic compression implants

Abstract

A shape-memory alloy orthopedic implant for coupling a pair of bone segments includes a bridge having a longitudinal axis, a first end, and a second end opposite the first end, a first leg extending from the first end of the bridge, wherein the first leg has a radially outer surface extending axially from a fixed end of the first leg to a free end of the first leg, and a second leg extending from the second end of the bridge, wherein the second leg has a radially outer surface extending axially from a fixed end of the second leg to a free end of the second leg, wherein a plurality of axially spaced serrations are formed on first leg and the second leg, wherein each serration includes a curved engagement surface and a curved engagement shoulder for forming an interference fit with the pair of bone segments.

Description

BARBED ORTHOPEDIC COMPRESSION IMPLANTSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims benefit of U.S. provisional patent application Serial No. 63 / 435,152 filed December 23, 2022, and entitled "Barbed Orthopedic Compression Implants," which is hereby incorporated herein by reference in its entirety for all purposes.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable.BACKGROUND

[0003] Staple-style orthopedic implants are often used to provide fixation and stability at a fracture, osteotomy or arthrodesis site to enable fusion. Some orthopedic implants are shape memory compression implants that may change dimensions as a function of temperature to offer greater fixation and stability to enable improved fusion.BRIEF SUMMARY

[0004] An embodiment of a shape-memory alloy orthopedic implant for coupling a pair of bone segments, wherein the shape-memory alloy orthopedic implant comprises a bridge having a longitudinal axis, a first end, and a second end opposite the first end, wherein the bridge has a radially outer surface extending axially from the first end to the second end, a first leg extending from the first end of the bridge, wherein the first leg has a central axis, a fixed end fixably attached to the bridge, a free end distal the bridge, and a radially outer surface extending axially from the fixed end of the first leg to the free end of the first leg, and a second leg extending from the second end of the bridge, wherein the second leg has a central axis, a fixed end fixably attached to the bridge, a free end distal the bridge, and a radially outer surface extending axially from the fixed end of the second leg to the free end of the second leg, wherein a plurality of axially spaced serrations are formed on the radially outer surface of the first leg and the radially outer surface of the second leg, wherein each serration comprises a curved engagement surface and a curved engagement shoulder for forming an interference fit with the pair of bone segments. In some embodiments, the curved engagement surfaceof each serration has a shape extending along a curved longitudinal axis of the curved engagement surface between a distal edge and a tip opposite the distal edge along the longitudinal axis of the curved engagement surface. In some embodiments, the curved engagement shoulder extends along the distal edge of the curved engagement surface and is curved along a longitudinal axis of the curved engagement shoulder that extends in the direction of the curved engagement surface. In certain embodiments, the curved engagement shoulder projects concavely along the longitudinal axis of the curved engagement surface. In certain embodiments, the curved engagement surface projects convexly along the longitudinal axis of the curved engagement surface. In some embodiments, the curved engagement surface of each serration comprises a pair of opposing lateral sides and a curved lateral axis extending between the pair of lateral sides, the lateral axis of the curved engagement surface extending perpendicular to either the central axis of the first leg or the central axis of the second leg. In some embodiments, the plurality of serrations formed on the radially outer surface of the second leg face the plurality of serrations formed on the radially outer surface of the first leg. In certain embodiments, the central axis of the first leg is not parallel to the central axis of the second leg. In certain embodiments, the longitudinal axis of the bridge, the central axis of the first leg, and the central axis of the second leg are disposed in a common reference plane. In some embodiments, the orthopedic implant has a central axis disposed in the common reference plane, positioned between the central axes of the first leg and the second leg, and intersecting the longitudinal axis of the bridge, wherein the first leg is oriented at a leg angle a measured in the common reference plane between the central axis of the first leg and the central axis of the orthopedic implant, wherein the leg angle a is between approximately 0° and approximately 20°.

[0005] An embodiment of a shape-memory alloy orthopedic implant for coupling a pair of bone segments, wherein the shape-memory alloy orthopedic implant comprises a bridge having a longitudinal axis, a first end, and a second end opposite the first end, wherein the bridge has a radially outer surface extending axially from the first end to the second end, a first leg extending from the first end of the bridge, wherein the first leg has a central axis, a fixed end fixably attached to the bridge, a free end distal the bridge, and a radially outer surface extending axially from the fixed end of the first leg to the free end of the first leg, and a second leg extending from the second end of the bridge, wherein the second leg has a central axis, a fixed end fixably attached to the bridge, a free end distal the bridge, and a radially outer surface extending axially from the fixedend of the second leg to the free end of the second leg, wherein a plurality of axially spaced serrations are formed on the radially outer surface of the first leg and the radially outer surface of the second leg, wherein each serration comprises a curved engagement surface that is curved along a lateral axis of the curved engagement surface, the lateral axis of the curved engagement surface extending perpendicular to either the central axis of the first leg or the central axis of the second leg. In some embodiments, the curved engagement surface of each serration comprises a revolved surface. In some embodiments, the curved engagement surface projects convexly along the lateral axis of the curved engagement surface. In certain embodiments, the curved engagement surface of each serration extends along a curved longitudinal axis of the curved engagement surface between a distal edge and a tip opposite the distal edge along the longitudinal axis of the curved engagement surface. In certain embodiments, each serration comprises a pair of the curved engagement surfaces which share an edge formed between the pair of curved engagement surfaces. In some embodiments, each serration comprises a curved engagement shoulder flanking the curved engagement surface for forming an interference fit with the pair of bone segments. In some embodiments, the curved engagement shoulder is curved along a longitudinal axis of the curved engagement shoulder that extends in the direction of the curved engagement surface. In certain embodiments, the curved engagement surface projects convexly along the longitudinal axis of the curved engagement surface. In some embodiments, each serration comprises a pair of the curved engagement shoulders which share a crest extending in the direction of the curved engagement surface. In some embodiments, the plurality of serrations formed on the radially outer surface of the second leg face the plurality of serrations formed on the radially outer surface of the first leg.

[0006] Embodiments described herein comprise a combination of features and characteristics intended to address various shortcomings associated with certain prior devices, systems, and methods. The foregoing has outlined rather broadly the features and technical characteristics of the disclosed embodiments in order that the detailed description that follows may be better understood. The various characteristics and features described above, as well as others, will be readily apparent to those skilled in the art upon reading the following detailed description, and by referring to the accompanying drawings. It should be appreciated that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designingother structures for carrying out the same purposes as the disclosed embodiments. It should also be realized that such equivalent constructions do not depart from the spirit and scope of the principles disclosed herein.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] For a detailed description of various exemplary embodiments, reference will now be made to the accompanying drawings in which:

[0008] Figure 1 is an isometric view of an embodiment of an implant for compressing two bone segments together in accordance with the principles described herein;

[0009] Figure 2 is an isometric view of the implant of Figure 1 ;

[0010] Figure 3 is a front view of the implant of Figure 2;

[0011] Figure 4 is a side view of an embodiment of a serration of the implant of Figure 2 in accordance with the principles disclosed herein;

[0012] Figure 5 is a front view of the serration of Figure 4;

[0013] Figure 6 is an isometric view of an embodiment of an implant for compressing two bone segments together in accordance with the principles described herein;

[0014] Figure 7 is a front view of the implant of Figure 6;

[0015] Figure 8 is a side view of an embodiment of a serration of the implant of Figure 6 in accordance with the principles disclosed herein;

[0016] Figure 9 is a front view of the serration of Figure 8;

[0017] Figure 10 is an isometric view of an embodiment of an implant for compressing two bone segments together in accordance with the principles described herein;

[0018] Figure 11 is a front view of the implant of Figure 10;

[0019] Figure 12 is an isometric view of an embodiment of an implant for compressing two bone segments together in accordance with the principles described herein; and

[0020] Figure 13 is a front view of the implant of Figure 12.DETAILED DESCRIPTION

[0021] The following discussion is directed to various exemplary embodiments. However, one of ordinary skill in the art will understand that the examples disclosed herein have broad application, and that the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to suggest that the scope of the disclosure, including the claims, is limited to that embodiment.

[0022] The drawing figures are not necessarily to scale. Certain features and components herein may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in interest of clarity and conciseness.

[0023] In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to... .” Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection of the two devices, or through an indirect connection that is established via other devices, components, nodes, and connections. In addition, as used herein, the terms “axial” and “axially” generally mean along or parallel to a given axis (e.g., central axis of a body or a port), while the terms “radial” and “radially” generally mean perpendicular to the given axis. For instance, an axial distance refers to a distance measured along or parallel to the axis, and a radial distance means a distance measured perpendicular to the axis. As used herein, the terms “approximately,” “about,” “substantially,” and the like mean within 10% (i.e., plus or minus 10%) of the recited value. Thus, for example, a recited angle of “about 80 degrees” refers to an angle ranging from 72 degrees to 88 degrees.

[0024] Unless the context dictates the contrary, all ranges set forth herein should be interpreted as being inclusive of their endpoints, and open-ended ranges should be interpreted to include only commercially practical values. Similarly, all lists of values should be considered as inclusive of intermediate values unless the context indicates the contrary.

[0025] As previously described above, staple-style orthopedic implants are designed to provide fixation and stability at a fracture, osteotomy, or arthrodesis site to enable fusion. Such implants may include 2, 3, 4 or more legs. Generally, the legs of the implant are connected with a bridge that may come in various forms, sizes and shapes depending on the particular application and anatomy. The implants are often part of system that includes instruments for use with the implants and an associated surgical techniques. The instruments may include for example: sizing guides / templates, drill guides, drill or drilling pins, locating pins / pull pins, tamps, insertion tools, removal tools, and possibly heat source instruments for shape memory alloys.

[0026] One type of orthopedic staple-style implants are shape memory compression staples that are often made from medical grade Nitinol suitable for medical deviceapplications. Nitinol exhibits phase transformation whereby the molecular arrangement of Nitinol can vary according to the temperatures to which it is exposed. At lower temperatures, the crystalline architecture of Nitinol resembles an accordion making it relatively unstable, malleable, and weak. This is referred to as the martensitic phase of Nitinol (martensite). At higher temperatures, the crystalline structure of Nitinol is rearranged into a cubic form making it contracted, rigid, and strong. This is referred to as the austenitic phase of Nitinol (austenite). The temperature range at which Nitinol transforms from the martensitic phase into austenitic phase can be adjusted and manipulated through manufacturing processes. During manufacturing, a Nitinol device undergoes heat treatments that “program” the temperature ranges that trigger the transition between the martensitic and austenitic phases. For example, when a Nitinol device is heated, the programing dictates the beginning of the phase transformation from martensite to austenite (Austenite Start temperature or As) and the end of the transformation (Austenite Finish temperature or Af). In addition, when a Nitinol device is cooled, the programming dictates the beginning of the phase transformation from austenite to martensite (Martensite Start temperature or Ms) and the end of the transformation (Martensite Finish temperature or Mf).

[0027] In addition to the aforementioned phase transformation, Nitinol exhibits shape memory and superelastic / pseudoelastic characteristics. With regards to shape memory, a Nitinol device can be designed to transform from one shape to another when exposed to heat. For example, prior to heat treating, the Nitinol device may be cooled, and thus become malleable in the martensite material phase and shaped into a particular form that imparts internal residual stresses. Heat treatment can then be applied, which sets or “bakes” this established shape into the memory of the implant. Then, when the Nitinol device is heated through its transformation temperature range, the device will revert to its predetermined final shape as it undergoes the phase transformation to Austenite. The superelastic characteristic of Nitinol is displayed when a Nitinol staple is warmed through its transformation temperature range but is constrained and prevented from returning to its original shape. While constrained in a deformed shape, as is the case when a Nitinol bone staple is in bone, continuous exposure to sufficient heat allows the implant to behave like an elastic spring. This superelastic effect thus may be used to maintaining a long-term compressive force between bone segments over a large displacement range.

[0028] There are two varieties of staples are made from Nitinol: Thermally-activated and Superelastic. The transition temperature ranges of these types of implants vary and can be classified as either heat-activated or body temperature-activated. Heat-activated Nitinol bone staples have an Asand Af above body temperature. These implants are inserted into bone in the malleable martensitic phase and are exposed to an external heat via electrocautery or bi-polar electrical resistance to convert the implant from martensite to austenite, and thus, promote shape change that creates initial compression between joined bone segments. Body temperature-activated Nitinol bone staples have a transition temperature range that is slightly lower than body temperature. Since their austenite start temperature (As) may be at or below room temperature, these implants may utilize freezer storage to prevent premature closure. These implants are placed into the osteotomy or arthrodesis site while still in a frozen state, and then compress the joined bone segments through the shape memory effect as they warm to body temperature. Compression for each type of implant is maintained through the superelastic effect as the implant is constrained in an open position by the bone segments. However, due to manufacturing limitations of thermally-activated Nitinol, traditional machining methods (milling, grinding, turning, etc.) have generally not been cost-effective. Thus, many Nitinol staples are created using raw Nitinol wire material that is bent to the desired shape and heat treated to set the shape, generally limiting implant geometries to simple U-shaped staples having two legs and a constant cross-section between the distal ends of the implant legs.

[0029] Superelastic shape memory compression staples are the latest generation of Nitinol bone implants. The austenite finish temperature (Af) for these implants is significantly below room temperature, for example 10 to -20 degrees C, thus freezer storage to maintain an initial shape in the martensite material phase may not be sufficient, as implants may begin to deflect before being placed into the osteotomy or arthrodesis site. Thus, in some instances, external constraint devices may be used to mechanically open and constrain the legs of the implant prior to inserting them into pre-drilled holes in bone. Upon release of the constraining tool, the superelastic effect is transferred from the tool to the bone to achieve compression across the osteotomy or arthrodesis site.

[0030] Due to a relatively low Af (e.g., 10 to -20 degrees C), superelastic Nitinol implants may utilize different manufacturing approaches as compared to implants made from wire raw material, and thus, may include more configurations and geometries, such as additional staple legs. For example, starting with bulk raw material with low Af, implantsmay be machined using wire Electrical Discharge Machining (EDM) to create the desired shapes. The shapes of these implants are however generally limited to the shapes that may result from the intersection of wire paths from two planes, and thus, such implants may not conform to the complex anatomies of the body. Additionally, due to the EDM manufacturing process, the leg features typically have square or rectangular cross- sectional shapes that do not match the shape and size of the round drilled holes in which the legs are installed. A result of this mismatch is that the implant leg strength may not be maximized, and thus, the most common fracture location of a staple is in the leg features. This typically limits the use of staples to applications in lower biomechanical loading areas. However, as staples become more common practice for surgeons, there is a continued desire to use staples in a broader array of applications, including high biomechanical loading applications.

[0031] Accordingly, embodiments disclosed herein include staple-style implants (which may be alternatively referred to herein as “implants,” or “orthopedic implants,” “staples,” or “orthopedic staples”) that may be produced with more complex geometries than what is typically possible with EDM manufacturing processes. In particular, some embodiments disclosed herein may utilize advanced milling techniques and or electrochemical machining (ECM) to produce implants having rounded or partially rounded legs that maximize strength within a given drilled hole. In addition, some embodiments disclosed herein may include rounded legs having a plurality of axially spaced serrations or barbs formed thereon for forming an interference fit with a pair of bone segments to which the staple-style implant is attached. Particularly, embodiments of serrations disclosed herein include one or more curved engagement surfaces or features for engaging or contacting the bone segments to thereby anchor the implant to the pair of bone segments. The curved surfaces of the serrations may maximize the surface area of the serration in contact with the given bone segment so as to more securely attach the implant to the bone segment while minimizing the formation of stress concentrations in either bone segment or the implant.

[0032] Referring now to Figure 1 , an embodiment of a staple-style implant 100 is shown. In this exemplary embodiment, implant 100 is a U-shaped staple used to fix, stabilize, and apply compression (illustrated with arrows 19 in Figure 1 ) to a break or fracture 12 between a first bone segment 2 and a second bone segment 4 of a broken bone. Each bone segment 2, 4 has a curved outer surface or curved profile 7, 9, respectively, proximal implant 100. Bone segments 2, 4 represent an exemplary curved profile (e.g.,round, elliptical, etc.) such as that of a generally cylindrical long bone (e.g., femora, tibiae, humeri, ulnae, metacarpals, clavicle, etc.), however, as will be described more fully below, implant 100 may be used with any classification of bone (e.g., short, flat, sutural, irregular, sesamoid, or long), and in locations with or without a curved profile. Additionally, although break 12 is shown extending generally along a plane oriented perpendicular to curved profiles 7, 9, it is to be understood that break 12 may be positioned at any angle with respect to curved profiles 7, 9.

[0033] In this exemplary embodiment, implant 100 generally includes a bridge 110 and a plurality of legs 130 extending from bridge 110. When secured to bone segments 2, 4, bridge 110 extends across or spans break 12, while legs 130 penetrate into corresponding bone segments 2, 4 via holes 14, 16, respectively. In particular, a first hole 14 is drilled into first bone segment 2 and a second hole 16 is drilled into second bone segment 4. First hole 14 is defined by a generally cylindrical inner surface 18 and has a central or longitudinal axis 15, and second hole 16 is defined by a generally cylindrical inner surface 20 and has a central or longitudinal axis 25 that is spaced apart from and oriented parallel to central axis 15. Legs 130 are pressed into and secured within holes 14, 16 via an interference fit, and maintain static positions relative to bone segments 2, 4, as elastic energy stored within implant 100 applies compression 19 across the break 12 between the bone segments 2, 4.

[0034] Referring now to Figures 2 and 3, implant 100 has a central axis 105 passing through the geometric center of bridge 110 and centered between legs 130 in front view (Figure 3). In addition, bridge 110 has a curved central or longitudinal axis 115, a first terminal end 110a, and a second terminal end 110b opposite end 110a. Each leg 130 extends longitudinally from bridge 110, and in particular, extends from a corresponding end 110a, 110b of bridge 110. Each leg 130 has a central or longitudinal axis 135 laterally spaced apart from central axis 105, a first or fixed end 130a fixably attached to and integral with the corresponding end 110a, 110b of bridge 110, and a second or free end 130b distal bridge 110. In this embodiment, longitudinal axis 115 of bridge 110 intersects axes 105, 135, and axes 105, 115, 135 lie in a common plane. For purposes of clarity and further explanation, the common plane within which axes 105, 115, 135 are disposed may also be referred to herein as the “reference plane.’’ In Figure 3, the reference plane is a plane oriented parallel to the sheet of paper on which the drawing is shown.

[0035] As best shown in Figure 3, each leg 130 is oriented at a leg angle a measured between the corresponding axis 135 and the central axis 105 in the reference plane (in front view of Figure 3). In this exemplary embodiment, leg angle a of each leg 130 ranges from about 0 degrees to about 20 degrees, alternatively from about 0 degrees to about 15 degrees, and alternatively from about 0 degrees to about 10 degrees. However, it is to be understood that angle a may vary from the exemplary ranges provided herein in other embodiments. In embodiments where the leg angles a are greater than 0 degrees, such as that shown in Figures 2 and 3, second ends 130b of legs 130 are positioned closer to central axis 105 than first ends 130a, the legs 130 may be referred to herein as “inwardly biased.” Thus, in some embodiments, linear central axis 135 of the first leg 130 is not parallel to linear central axis 135 of the second leg 130. In general, the leg angles a of the legs 130 may be the same or different. In this embodiment, each leg angle a is an acute angle between 0 degrees and 10 degrees, legs 130 are inwardly biased, and each leg angle a is the same.

[0036] As previously described, central axis 115 of bridge 110 is curved. In general, the central axis 115 may have a constant or variable radius of curvature Rus measured in the reference plane in front view (Figure 3) from a point along central axis 105 to central axis 115 of bridge 110. In embodiments described herein, the radius of curvature Rus of central axis 115 at any point along central axis 115 can range from about 0 millimeters (mm) to about 200 mm, alternatively from about 15 mm to about 50 mm, and alternatively from about 20 mm to about 30 mm. It should be appreciated that the radius of curvature Rus of central axis 115 can vary along its length between ends 110a, 110b or be constant along its length between ends 110a, 110b.

[0037] As best shown in Figure 2, bridge 110 has a radially outer surface 111 extending axially (relative to axis 115) from end 110a to end 110b. In addition, bridge 110 has a cross-section 116 taken in a plane oriented perpendicular to axis 115. In cross-section 116, outer surface 111 of bridge 110 defines a non-rectangular outer shape or profile . In this embodiment, the outer profile at cross-section 116 is generally D-shaped. In particular, outer surface 111 includes a first or upper surface 112, a second or lower surface 114, and a pair of fillet or lateral surfaces 118 extending from upper surface 112 to lower surface 114. Upper surface 112 and lower surface 114 are oriented parallel to each other and central axis 115 in the front view (Figure 3). In a cross-section of bridge 110 taken in a plane oriented perpendicular to axis 115 (e.g., cross-section 116), bridge 1 10 has an outer profile defined by outer surface 11 1 thatis generally flat along upper surface 112 and generally flat along lower surface 114. Fillets 118 are curved, convex surfaces extending axially from end 110a to end 110b. Although bridge 110 has an outer surface 11 1 defining a D-shaped profile in crosssection 1 16 taken perpendicular to axis 115 in this exemplary embodiment, in other embodiments, the bridge (e.g., bridge 110) may have an outer surface with a geometry that defines other non-rectangular profiles in cross-sections taken perpendicular to the central axes of the bridge (e.g., such as polygonal, semi-circular, elliptical, and circular). In addition, the non-rectangular profile of the legs (e.g., legs 130) in crosssections taken perpendicular to the central axes of the legs may be the same or different from the non-rectangular profile of the bridge in cross-sections taken perpendicular to the central axis of the bridge.

[0038] In this embodiment, the cross-sectional area of the bridge 110 in any plane oriented perpendicular to axis 115 (e.g., cross-section 116) is equal to or greater than the cross-sectional area of each leg 130 taken in any plane oriented perpendicular to axis 135 (e.g., cross-section 134). In embodiments described herein, the ratio of (i) the cross-sectional area of the bridge (e.g., bridge 110) in any plane oriented perpendicular to the central axis of the bridge (e.g., axis 115) to (ii) the cross-sectional area of each leg (e.g., leg 130) in any plane oriented perpendicular to the central axis of the leg (e.g., axis 135) is 1.0 to 10.0, alternatively about 1.5 to 3.0, and alternatively about 1.5 to 2.0.As described further below, in some applications, the D-shaped cross-section of bridge 110 and the radius of curvature Rus between ends 110a, 110b in the reference plane provide a conforming fit along the generally convex, cylindrical outer surface of a bone (as shown in Figure 1 ). Without being limited to this or any other theory, the lower surface 114 defining a generally flat profile in cross-sectional view in a plane oriented perpendicular to axis 115 may reduce the height to which the implant 100 extends from the bone segments 2, 4, while the upper surface 112 having a generally curved convex profile in cross-sectional view in a plane oriented perpendicular to axis 115 may provide a smooth, gradual transition to minimizes irritation of soft tissue adjacent the bone.

[0039] Referring still to Figures 2 and 3, each leg 130 has a radially outer surface 131 extending axially (relative to corresponding axis 135) between ends 130a, 130b, a plurality of axially spaced serrations or barbs 140 disposed along outer surface 131 , and a relief or bevel 180 disposed along outer surface 131 at end 130b. Bevel 180 isgenerally planar in this exemplary embodiment and is located on the inside of each leg 130 at end 130b to define tapered tips 132 at the ends 130b of legs 130. Additionally, in this exemplary embodiment, legs 130 and bridge 110 have different cross-sectional geometries. To smoothly blend legs 130 and bridge 110 where fixed ends 130a of legs 130 meet lower surface 114 of bridge 110, in this exemplary embodiment, implant 100 includes smoothly curved concave transition surfaces 120 (Figure 3) between fixed ends 130a and lower surface 114.

[0040] As best shown in Figure 2, each leg 130 has a cross-section 134 taken in a plane oriented perpendicular to the corresponding axis 135. In cross-section 134, outer surface 131 defines a non-rectangular outer shape or profile 136. In this exemplary embodiment, outer surface 131 of each leg 130 is a cylindrical surface extending axially (relative to corresponding axis 135) from end 130a to end 130b, and thus, profile 136 at cross-section 134 is generally circular. As described in more detail below, in some applications, the cylindrical shapes of the legs of an implant (e.g., cylindrical radial outer surface 131 of legs 130) may be advantageous as the cylindrical geometry can more completely fill the drilled hole (as shown in Figure 1 at holes 14, 16), as compared to a rectangular prismatic geometry, and thus, offers the potential for enhanced bending strength and fixation within the bone segments (e.g., bone segments 2, 4). More specifically, rectangular cross-sectional dimensions of legs having a rectangular prismatic shape are limited as the sharp corners of the crosssection contact the cylindrical inner surface of the bone defined by the drilled hole, and any increases in one of the cross-sectional dimensions of the rectangular crosssection may result in sufficient interference between the legs and bone segments to restrict insertion of the legs into the bone segments. However, it is to be understood that although legs 130 have cylindrical outer surfaces 131 defining circular profiles 136 in cross-sections 134 taken perpendicular to axes 135 in this exemplary embodiment, in other embodiments, the legs (e.g., legs 130) may have outer surfaces with other geometries that define other non-rectangular profiles (e.g., profiles 136) in crosssections taken perpendicular to the central axes of the legs (e.g., such as polygons, semi-circular, elliptical, etc. along cross-section 134).

[0041] In this exemplary embodiment, outer surface 131 of each leg 130 is cylindrical, and thus does not taper along central axis 135. However, in other embodiments, the outer surface of each leg (e.g., outer surface 131 of each leg 130) may be frustoconical and characterized by a non-zero taper along the longitudinal length of the leg. In someapplications, a non-zero taper may advantageously facilitate a wedging fit between the legs and a cylindrically shaped drilled hole, which may enhance the retention of the implant with the bone segments.

[0042] Each leg 130 comprises a plurality of serrations 140 that are axially spaced (relative to corresponding axis 135) between ends 130a, 130b and provided along outer surface 131 on the inside of each leg 130 (i.e., along the sides of legs 130 that face toward each other and axis 105). Serrations 140 of legs 130 are generally configured to form an interference fit or “bite” into the inner surfaces 18 and 20 defining the holes 14, 16 of bone segments 2 and 4, respectively, of bone segments 2 and 4 to secure or anchor the staple-style implant 100 to the bone segments 2 and 4. In this exemplary embodiment, serrations 140 are formed in the outer surface 131 such that the cross-sectional area of profile 136 is greater than a maximum cross-sectional area of each serration 140. However, it is to be understood that in other embodiments serrations 140 may project outwardly from the outer surface 131 of each leg 130 along the side of the leg 130. In other words, a maximum cross-sectional area of each outwardly projecting serration 140 may be greater than the cross-sectional area of profile 136.

[0043] Referring now to Figures 4 and 5, one of the serrations 140 is shown in greater detail. In this exemplary embodiment, serration 140 is generally defined by a proximal curved engagement surface 142 and a pair of distal curved engagement shoulders 160. Curved engagement surface 142 has a generally triangular or shark tooth shape and extends longitudinally between a pair of distal edges 143 and a pointed tip 144 opposite the distal edges 143 along a curved first or longitudinal axis 145 of the curved engagement surface 142. The longitudinal axis 145 of curved engagement surface 142 extends generally parallel to the central axis 135 of the leg 130 in that axis 145 extends in the direction of ends 130a, 130b of leg 130. While in this exemplary embodiment the serrations 140 comprising curved engagement surfaces 142 are positioned along legs 130 having curved outer surfaces 131 , it may be understood that in other embodiments the serrations 140 having curved engagement surfaces 142 (as well as other curved features described further herein) may be positioned on legs having shapes or geometries which vary from the shape of legs 130. For example, in some embodiments, serrations 140 (including curved engagement surfaces 142) may be positioned along legs having a square or rectangular cross-section.

[0044] Curved engagement surface 142 is curved along the longitudinal axis 145 such that the curved engagement surface 142 curves or projects convexly (away from central axis 135 of the leg 130) along the longitudinal axis 145. Additionally, curved engagement surface 142 is .curved along a curved second or lateral axis 146 that extends between a pair of opposing lateral edges or sides 147 of the curved engagement surface 142. The lateral axis 146 of curved engagement surface 142 extends generally perpendicular to the longitudinal axis 145 thereof in this exemplary embodiment. Additionally, lateral axis 146 extends perpendicular to the central axis 135 of the leg 130 comprising the serration 140. Curved engagement surface 142 curves or projects convexly (away from central axis 135) along the lateral axis 146. As shown particularly in Figure 5, the pair of lateral edges 147 intersect at the tip 144 of curved engagement surface 142. In some embodiments the radius of curvature of the curved engagement surface 142 along longitudinal axis 145 is equal to or greater than 25% of the maximum diameter of the leg 130 comprising the serration 140. For example, in some embodiments, the maximum diameter of the leg 130 may range approximately from 2 millimeters (mm) to 4 mm while the radius of curvature of curved engagement surface 142 correspondingly ranges from 0.5 mm to 1.0 mm. However, it may be understood that in some embodiments the radius of curvature of curved engagement surface 142 may be substantially greater than 25% of the maximum diameter of the leg 130.

[0045] In this exemplary embodiment, each curved engagement shoulder 160 extends longitudinally along a curved first or longitudinal axis 163 between a corresponding distal edge 143 of the curved engagement surface 142 and a distal edge 162 opposite the distal edge 143. Additionally, each curved engagement shoulder 160 extends laterally along a curved second or lateral axis 165 between a curved outer side or edge 164 and a central crest 166 shared by the pair of curved engagement shoulders 160. The lateral axis 165 of each curved engagement shoulder 160 extends generally perpendicular to the longitudinal axis 163 thereof. The outer edges 164 of curved engagement shoulders 160 extend from the distal edges 162 of shoulders 160 to the distal edges 143 of the curved engagement surface 142. In this exemplary embodiment, each curved engagement shoulder 160 is .curved or projects concavely (towards central axis 135 of leg 130) along the longitudinal axis 163 thereof in this exemplary embodiment. Additionally, each curved engagement shoulder 160 is curved or projects convexly (away from central axis 135) along the lateral axis 165thereof in a saddle-shaped configuration. In certain embodiments the radius of curvature of each curved engagement shoulder 160 along longitudinal axis 163 may range from zero to substantially larger than the maximum outer diameter of the leg 130 comprising the serration 140. In some embodiments, the radius of curvature of each curved engagement shoulder 160 ranges approximately between 0.10 mm and 0.25 mm. In certain embodiments, the radius of curvature of each curved engagement shoulder 160 along lateral axis 165 ranges approximately between 0.10 mm and 0.25 mm; however, it may be understood that the radius of curvature of curved engagement shoulder 160 along both the longitudinal axis 163 and lateral axis 165 may vary in some embodiments from the ranges provided herein. In this exemplary embodiment, the lateral axes 165 of curved engagement shoulders 160 are disposed at a non-zero angle relative to each other, thereby defining the central crest 166 formed between the pair of curved engagement shoulders 160. Additionally, while in this exemplary embodiment each serration 140 comprises a plurality of curved engagement shoulders 160, in other embodiments, serrations 140 may include only a single curved engagement shoulder 160 flanking the curved engagement surface 142.

[0046] In addition to curved engagement surface 142 and the pair of curved engagement shoulders 160, each serration 140 is defined by a pair of lateral chamfers 149 which flank the pair of lateral edges 147 of curved engagement surface 142. Additionally, each curved engagement shoulder 160 is flanked by an outer curved chamfer or edge 168 which flanks the outer edge 164 of the curved engagement shoulder 160, and a distal chamfer or edge 170 that extends along the distal edge 162 of the curved engagement shoulder 160. In this configuration, curved edges 168 and 170 curve or wrap partially around the leg 130, increasing the contact length formed between edges 168 and 170 and the inner surface of the hole formed in the bone segment (e.g., bone segments 2 and 4 shown in Figure 1 ) in which the leg 130 is positioned. The increased contact length between edges 168 and 170 and the bone segment more securely anchors the leg 130 to the bone segment, increasing the pullout resistance of the leg 130 with respect to the bone segment. Particularly, in this exemplary embodiment, a curved lip 172 (Figure 4) is formed between the distal edge 162 of each curved engagement shoulder 160 and the corresponding distal edge 170, where each curved lip 172 terminates at the central crest 166 formed between the curved engagement shoulders 160. It may be understood that at least in someembodiments the radius of curvature of the curved engagement shoulder 160 along longitudinal axis 163 may not be so large as to eliminate curved lip 172.

[0047] In this exemplary embodiment, implant 100 is made of a Nitinol material, and thus, can be heat treated and programed, as discussed above, to have shape memory and superelastic / pseudoelastic characteristics such that implant 100 may be classified as a superelastic shape memory implant, and may transform from one shape to another when exposed to heat.

[0048] Referring now generally to Figures 1- 5, the surgical use of implant 100 may utilize the shape memory characteristics of Nitinol to impart compressive loads across a fracture, osteotomy, or arthrodesis site (e.g., compression 19 across break 12 as shown in Figure 1) to enable fusion. In the manner previously described, implant 100 can be made of Nitinol and programed though deformation and heat treatment, such that the shape memory of the Nitinol material increases leg angle a (e.g. ends 130b move inward toward axis 105) and / or translates ends 110a, 110b of bridge 110 towards central axis 105 in response to heating of implant 100. Such heating of implant 100 may be accomplished with an external source (e.g., heat-activated), or as implant 100 is brought to room temperature or body temperature (e.g., body temperature-activated). In addition, in some embodiments, the shape transformation may have already occurred and an external tool may be used to restrain the deformation of implant 100. For example, in some embodiments, the external tool may engage with bridge 110 and thereby apply forces to bridge 110 to elastically flex bridge 110 at ends 110a, 110b to bring axes 135 into parallel with central axis 105 to reduce each leg angle a. Thus, in some embodiments, legs 130 may be constrained with axes 135 oriented parallel and coaxially aligned with central axes 15, 25 of holes 14, 16 in bone segments 2, 4, respectively (as shown in Figure 1 ), and then inserted into corresponding holes 14, 16. Legs 130 are advanced into holes 14, 16 until lower surface 114 of bridge 110 is pressed into contact (or approximate contact) with bone segments 2, 4, as the curvature of bridge 110 may be specifically designed and selected to accommodate the underlying curved profiles 7, 9 of bone segments 2, 4 to allow a low implant profile and establish an anatomically conforming fit. Next, the external tool may be removed, to release the strain energy of the elastically deformed implant 100 and allow legs 130 to apply compression across break 12 as the free ends 130b of legs and / or ends 110a, 110b of bridge 110 are biased inward toward central axis 105 in an anchored configuration of the implant 100.

[0049] In the anchored configuration of implant 100, the serrations 140 of legs 130 thereof the serrations 140 of each leg 130 form an interference fit or bite into the inner surfaces 18 and 20 defining the holes 14 and 16 of bone segments 2 and 4, respectively, to anchor the staple-style implant 100 to the bone segments 2 and 4 whereby relative movement between the legs 130 and the bone segments 2 and 4 in which they are received is restricted. Additionally, it is to be noted that the curved surface geometry of the curved engagement surface 142 and curved engagement shoulders 160 defining serrations 140 serves to maximize the surface area of each serration 140 in engagement or contact with inner surfaces 18 and 20 of holes 14 and 16. Particularly, curved engagement surface 142 and curved engagement shoulders 160 each have a greater surface area as compared to a similarly sized but planar in shape engagement surface and engagement shoulder. To state in other words, for a given perimeter or circumference of the curved engagement surface 142 / curved engagement shoulder 160, an increase in curvature of curved engagement surface 142 / curved engagement shoulder 160 results in a corresponding increase in the surface area of the given curved engagement surface 142 / curved engagement shoulder 160.

[0050] By applying curvature and thereby increasing the surface area of the curved engagement surface 142 and curved engagement shoulders 160, the amount of surface area of each serration 140 in contact with the inner surfaces 18 and 20 of holes 14 and 16, respectively. By increasing the amount of surface area of each serration 140 in contact with inner surfaces 18 and 20, stress concentrations applied to either serrations 140 or the inner surfaces 18 and 20 of holes 14 and 16 may be minimized, reducing the likelihood of structural failure of either the serrations 140 or the inner surfaces 18 and 20 of bone segments 2 and 4, respectively.

[0051] In some embodiments, staple-style implant 100, including legs 130 and their associated serrations 140, is formed using an ECM manufacturing process to thereby permit the formation of the curved features of the implant 100 including the curved features (e.g., curved engagement surface 142 and curved engagement shoulders 160) of serrations 140. For example, the curved engagement surfaces 142 of serrations 140 may comprise “revolved” surfaces or “surfaces of revolution” formed by sweeping a curve (defining the curved engagement surface 142) across a selected axis. However, it is to be understood that the method of manufacture of staple-style implant 100 and the surface geometry of the curved features of serrations 140,including curved engagement surface 142 and curved engagement shoulders 160, may vary in other embodiments.

[0052] Referring now to Figures 6 and 7, another embodiment of a staple-style implant 200 is shown. In general, implant 200 can be used in place of implant 100 previously described and shown in Figure 1. Implant 200 is substantially the same as implant 100 previously described above, and thus, features of implant 200 that are the same as and shared with implant 100 are identified with the same reference numerals, and the discussion below will focus on the features of implant 200 that are different from implant 100.

[0053] Similar to implant 100 previously described, implant 200 is a U-shaped staple including a bridge 210 and a plurality of legs 230 extending from bridge 210. Implant 200 has a central axis 205 passing through the geometric center of bridge 210 and centered between legs 230 in front view (Figure 6). In addition, bridge 210 has a curved central or longitudinal axis 215, a first terminal end 210a, and a second terminal end 210b opposite end 210a. Each leg 230 extends from bridge 210, and in particular, extends from a corresponding end 210a, 210b of bridge 210. Each leg 230 has a central or longitudinal axis 235 laterally spaced apart from central axis 205, a first or fixed end 230a fixably attached to and integral with the corresponding end 210a, 210b of bridge 210, and a second or free end 230b distal bridge 210. In this exemplary embodiment, each central axis 235 is linear, longitudinal axis 215 of bridge 210 intersects axes 205, 235, and axes 205, 215, 235 lie in a common plane. For purposes of clarity and further explanation, the common plane within which axes 205, 215, 235 are disposed may also be referred to herein as the “reference plane.” In Figure 6, the reference plane is a plane oriented parallel to the sheet of paper on which the drawing is shown. As best shown in Figure 6, each leg 230 is oriented at a leg angle a measured between the corresponding axis 235 and central axis 205 in the reference plane (in front view of Figure 6). Leg angles a may be the same as previously described with respect to implant 100. In this exemplary embodiment, each leg angle a is the same.

[0054] As previously described, central axis 215 of bridge 210 is curved. Similar to central axis 115 of bridge 110 previously described, the central axis 215 may have a constant or variable radius of curvature R215 measured in the reference plane in front view (Figure 6) from a point along central axis 205 to central axis 215 of bridge 210. The radius of curvature R215 may be the same as previously described with respect to radius of curvature R115 of central axis 115. Bridge 210 may have the same or similargeometry as bridge 110 previously described. For example, as shown at section 216 of Figure 4, bridge 210 has a D-shaped cross-section in a plane oriented perpendicular to axis 215, which may again provide a conforming fit along the convex cylindrical outer surface of a bone (as shown in Figure 1 ). Similar to implant 100, to smoothly blend legs 230 and bridge 210 where fixed ends 230a of legs 230 meet lower surface 114 of bridge 210.

[0055] Referring still to Figures 6 and 7, each leg 230 has a radially outer surface 231 extending axially (relative to corresponding axis 235) between ends 230a, 230b, a plurality of axially spaced barbs or serrations 240 disposed along outer surface 231 , and a bevel 180 disposed along outer surface 231 at end 230b. As with the serrations 140 shown in Figures 4 and 5, serrations 240 of legs 230 are generally configured to bite into the inner surfaces of holes formed in opposing bone segments (e.g., holes 14 and 16 of bone segments 2 and 4 of Figure 1) to secure or anchor the staple-style implant 200 to the bone segments. As with serrations 140 shown in Figures 4 and 5, in this exemplary embodiment, serrations 240 are formed in the outer surface 231 such that the cross-sectional area of profile 136 is greater than a maximum cross- sectional area of each serration 240. However, it is to be understood that in other embodiments serrations 240 may project outwardly from the outer surface 231 of each leg 230 along the side of the leg 230. In other words, a maximum cross-sectional area of each outwardly projecting serration 240 may be greater than the cross-sectional area of profile 136.

[0056] Referring now to Figures 8 and 9, one of the serrations 240 is shown in greater detail. In this exemplary embodiment, each serration 240 is generally defined by a pair of flanking proximal curved engagement surfaces 242, and a pair of distal curved engagement shoulders 258. Each curved engagement surface 242 of the serration 240 has a generally triangular or shark tooth shape and extends longitudinally along a curved first or longitudinal axis 245 of the curved engagement surface 242 between a separate distal edge 243 and a separate rounded tip 244 opposite the distal edge 243. The longitudinal axis 245 of each curved engagement surface 242 extends generally parallel to the central axis 235 of the leg 230 in that axis 245 extends in the direction of ends 230a, 230b of leg 230. In this exemplary embodiment, each curved engagement surface 242 of the serration 240 is curved along the longitudinal axis 245 such that the curved engagement surface 242 curves or projects convexly (away from central axis 235 of the leg 230) along the longitudinal axis 245.

[0057] Additionally, each curved engagement surface 242 of serration 240 is .curved along a curved second or lateral axis 246 that extends between an outer lateral edge or side 247 of the curved engagement surface 242 and a curved central edge 248 that is shared between the pair of curved engagement surfaces 242. The lateral axis 246 of curved engagement surface 242 extends generally perpendicular to the longitudinal axis 245 thereof in this exemplary embodiment. Additionally, lateral axis 246 extends generally perpendicular to the central axis 235 of the leg 230 comprising the serration 240. Each curved engagement surface 242 curves or projects convexly (away from central axis 235) along the lateral axis 246. In some embodiments the radius of curvature of each curved engagement surface 242 along longitudinal axis 245 ranges approximately between near zero and 6 mm. In some embodiments, the radius of curvature of each curved engagement surface 242 along lateral axis 246 ranges approximately between near zero and 6 mm depending on the configuration of the serration 240. Additionally, in other embodiments, engagement surface 242 may not be curved and instead may comprise a planar surface. It may be understood that the radius of curvature of curved engagement surface 242 along axes 245 and 246 may vary from the ranges provided herein.

[0058] In this exemplary embodiment, each curved engagement shoulder 258 of serrations 240 extends longitudinally along a curved first or longitudinal axis 263 between a corresponding distal edge 243 of the curved engagement surfaces 242 and a distal edge 262 opposite the distal edges 243. Additionally, each curved engagement shoulder 258 extends laterally along a curved second or lateral axis 265 between a curved outer side or edge 264 and a central crest 266 shared by the pair of curved engagement shoulders 258. The lateral axis 265 of each curved engagement shoulder 258 extends generally perpendicular to the longitudinal axis 263 thereof. The outer edges 264 of curved engagement shoulders 258 extend from the distal edges 262 of shoulders 258 to the distal edges 243 of the curved engagement surface 242. In this exemplary embodiment, each curved engagement shoulder 258 is .curved or projects concavely (towards central axis 235 of leg 230) along the longitudinal axis 263 thereof in this exemplary embodiment. Additionally, each curved engagement shoulder 258 is curved or projects convexly (away from central axis 235) along the lateral axis 265 thereof in a saddle-shaped configuration. In certain embodiments the radius of curvature of each curved engagement shoulder 258 along longitudinal axis 263 may vary substantially but in at least some embodiments is notso large as to eliminate lips or shelves 270 discussed further below. In certain embodiments, the radius of curvature of each curved engagement shoulder along longitudinal axis 263 and / or lateral axis 265 ranges approximately between 0.10 mm and 0.25 mm; however, it may be understood that the radius of curvature of each curved engagement shoulder 258 along axes 263 and 265 may vary from the ranges provided herein. In this exemplary embodiment, the lateral axes 265 of curved engagement shoulders 258 are disposed at a non-zero angle relative to each other, thereby defining the central crest 266 formed between the pair of curved engagement shoulders 258, where the central crest 266 may join or intersect a distal terminal end of the central edge 248 formed between curved engagement surfaces 242. Additionally, while in this exemplary embodiment each serration 240 comprises a plurality of curved engagement shoulders 258, in other embodiments, serrations 240 may include only a single curved engagement shoulder 258 flanking the curved engagement surface 242.

[0059] In addition to the pair of curved engagement surfaces 242 and the pair of curved engagement shoulders 258, each serration 240 is defined by the pair of shelves 270 (shown in Figure 8) that extend from the distal edge 262 of curved engagement shoulders 258 to a terminal edge 272. Unlike curved engagement surfaces 242 and engagement curved shoulders 258 in this exemplary embodiment, shelves 270 are generally planar defining the sharp terminal edge 272.

[0060] For similar reasons as previously described, in some surgical applications, the semi-cylindrical shape and geometry of legs 230 may be advantageous, as it may enable close mating and conforming contact with a substantial portion of the inner cylindrical surface of a drilled hole (e.g., as shown in Figure 1 at holes 14, 16), as compared to a rectangular prismatic shape. In addition, serrations 240 are configured to provide an interference fit along portions of serrations 240, which may increase the retention (herein also referred to as “bite”) with portions of the bone engaged by serrations 240 when staple-style implant 200 is in an anchored configuration coupled to the bone segments.

[0061] Similar to the anchored configuration of staple-style implant 100 described above, in the anchored configuration of implant 200, the serrations 240 of legs 230 thereof the serrations 240 of each leg 230 form an interference fit or bite into the inner surfaces 18 and 20 defining the holes 14 and 16 of bone segments 2 and 4, respectively, to anchor the staple-style implant 200 to the bone segments 2 and 4whereby relative movement between the legs 230 and the bone segments 2 and 4 in which they are received is restricted. Additionally, the curved surface geometry of the curved engagement surfaces 242 and curved engagement shoulders 258 defining serrations 240 serves to maximize the surface area of each serration 240 in engagement or contact with inner surfaces 18 and 20 of holes 14 and 16 to more securely attach the staple-style implant 200 to the bone segments 2 and 4 while reducing or minimizing the formation of stress concentrations in either the serrations 240 or the bone segments 2 and 4 themselves.

[0062] In some embodiments, staple-style implant 200, including legs 230 and their associated serrations 240, is formed using an ECM manufacturing process to thereby permit the formation of the curved features of the implant 200 including the curved features (e.g., curved engagement surfaces 242 and curved engagement shoulders 258) of serrations 240. For example, the curved engagement surfaces 242 of serrations 140 may comprise “draft” surfaces” which may be designed (prior to manufacturing) by pulling a selected plane along a vector extending normal to the selected plane. Curved engagement surfaces 242, being draft surfaces, have a different curved surface geometry from the curved engagement surfaces 142 of serrations 140 described above which may instead comprise revolved surfaces.

[0063] In this embodiment, implant 200 is made of a Nitinol material, and thus, can be heat treated and programed, as discussed above, to have shape memory and superelastic / pseudoelastic characteristics such that implant 200 may be classified as a superelastic shape memory implant, and may transform from one shape to another when exposed to heat.

[0064] Referring now to Figures 10 and 11 , another embodiment of a staple-style implant 250 is shown. In general, implant 250 can be used in place of implant 100 previously described and shown in Figure 1 . Implant 250 is substantially the same as implants 100 and 200 previously described above, and thus, features of implant 250 that are the same as and shared with implants 100 and 200 are identified with the same reference numerals, and the discussion below will focus on the features of implant 250 that are different from implants 100 and 200.

[0065] Similar to implants 100 and 200 previously described, implant 250 is a U- shaped staple including a bridge 260 and a plurality of legs 280 extending from bridge 260. Implant 250 has a central axis 255 passing through the geometric center of bridge 260 and centered between legs 280 in front view (Figure 11 ). In addition, bridge 260has a first terminal end 260a, and a second terminal end 260b opposite end 260a. Each leg 280 extends from bridge 260, and in particular, extends from a corresponding end 260a, 260b of bridge 260. Additionally, each leg 280 has a central or longitudinal axis 285 laterally spaced apart from central axis 255, a first or fixed end 280a fixably attached to and integral with the corresponding end 260a, 260b of bridge 260, and a second or free end 280b distal bridge 260. In this exemplary embodiment, each central axis 285 is linear, and a longitudinal axis of bridge 260 intersects axes 255, 285, and axes 255, 285 and the central axis of bridge 260 lie in a common plane. For purposes of clarity and further explanation, the common plane within which axes 255 and 285 are disposed may also be referred to herein as the “reference plane.” In Figure 11 , the reference plane is a plane oriented parallel to the sheet of paper on which the drawing is shown. As best shown in Figure 11 , each leg 280 is oriented at a leg angle a measured between the corresponding axis 285 and central axis 255 in the reference plane (in front view of Figure 11 ). Leg angles a may be the same as previously described with respect to implant 100. In this exemplary embodiment, each leg angle a is the same.

[0066] The geometry of bridge 260 may varies from the geometry of bridge 110 previously described. Particularly, bridge 260 has a square or rectangular crosssection in a plane oriented perpendicular to the central axis of bridge 260. However, it may be understood that the geometry of the cross-section of bridge 260 may vary in other embodiments.

[0067] Referring still to Figures 10 and 11 , each leg 280 has a radially outer surface 281 extending axially (relative to corresponding axis 285) between ends 280a, 280b, and a plurality of axially spaced barbs or serrations 290 disposed along outer surface 281. As best shown in Figure 10, each leg 280 has a cross-section 284 taken in a plane oriented perpendicular to the corresponding axis 285. In cross-section 284, outer surface 281 defines a generally rectangular outer shape or profile 286 having rounded corners or edges, unlike the circular profile 136 of legs 130 described above. However, it may be understood that the geometry of rectangular profile 286 may vary in other embodiments.

[0068] As with the serrations 140 shown in Figures 4 and 5, serrations 290 of legs 280 are generally configured to bite into the inner surfaces of holes formed in opposing bone segments (e.g., holes 14 and 16 of bone segments 2 and 4 of Figure 1 ) to secure or anchor the staple-style implant 250 to the bone segments. In this exemplary embodiment, serrations 290 project outwardly from the outer surface 281 of each leg280 along the side of the leg 280. In other words, a maximum cross-sectional area of each outwardly projecting serration 290 may be greater than the cross-sectional area of each leg 280. In this exemplary embodiment, each serration 290 includes or is defined by one or more curved engagement features such as curved engagement surfaces or edges intended to maximize the area of contact between the given serration 290 and the bone segment engaged by the serration 290. The curved engagement features of each serration 290 may curve in a direction generally parallel and / or perpendicular with the central axis 285 of the leg 280 comprising the serration 290. Additionally, in this exemplary embodiment, the curved engagement features of serrations 290 may comprise “draft” features designed (prior to manufacturing) by pulling a selected plane along a vector extending normal to the selected plane. The curved engagement features of serrations 290, being draft surfaces, have a different curved surface geometry from the curved engagement surfaces 142 of serrations 140 described above which may instead comprise revolved surfaces. However, it may be understood that the curved engagement features may not comprise draft features in other embodiments, and instead may be formed in other ways such as via revolving the features as described in greater detail above.

[0069] In this embodiment, implant 250 is made of a Nitinol material, and thus, can be heat treated and programed, as discussed above, to have shape memory and superelastic / pseudoelastic characteristics such that implant 250 may be classified as a superelastic shape memory implant, and may transform from one shape to another when exposed to heat.

[0070] Referring now to Figures 12 and 13, another embodiment of a staple-style implant 300 is shown. In general, implant 300 can be used in place of implant 100 previously described and shown in Figure 1 . Implant 300 is substantially the same as implants 100, 200, and 250 previously described above, and thus, features of implant 300 that are the same as and shared with implants 100, 200, and 250 are identified with the same reference numerals, and the discussion below will focus on the features of implant 300 that are different from implants 100, 200, and 250.

[0071] Similar to implants 100 and 200 previously described, implant 300 is a U- shaped staple including a bridge 310 and a plurality of legs 330 extending from bridge 310. Implant 300 has a central axis 305 passing through the geometric center of bridge 310 and centered between legs 330 in front view (Figure 11 ). In addition, bridge 310 has a first terminal end 310a, and a second terminal end 310b opposite end 310a. Eachleg 330 extends from bridge 310, and in particular, extends from a corresponding end 310a, 310b of bridge 310. Additionally, each leg 330 has a central or longitudinal axis 335 laterally spaced apart from central axis 305, a first or fixed end 330a fixably attached to and integral with the corresponding end 310a, 310b of bridge 310, and a second or free end 330b distal bridge 310. In this exemplary embodiment, each central axis 335 is linear, and a longitudinal axis of bridge 310 intersects axes 305, 335, and axes 305, 335 and the central axis of bridge 310 lie in a common plane. For purposes of clarity and further explanation, the common plane within which axes 305 and 335 are disposed may also be referred to herein as the “reference plane.” In Figure 13, the reference plane is a plane oriented parallel to the sheet of paper on which the drawing is shown. As best shown in Figure 13, each leg 330 is oriented at a leg angle a measured between the corresponding axis 335 and central axis 305 in the reference plane (in front view of Figure 13). Leg angles a may be the same as previously described with respect to implant 100. In this exemplary embodiment, each leg angle a is the same.

[0072] The geometry of bridge 310 may varies from the geometry of bridge 110 previously described. Particularly, bridge 310 has a square or rectangular crosssection in a plane oriented perpendicular to the central axis of bridge 310. However, it may be understood that the geometry of the cross-section of bridge 310 may vary in other embodiments.

[0073] Referring still to Figures 12 and 13, each leg 330 has a radially outer surface 331 extending axially (relative to corresponding axis 335) between ends 330a, 330b, and a plurality of axially spaced barbs or serrations 340 disposed along outer surface 331. As best shown in Figure 12, each leg 330 has rectangular profile 286 as described further above. However, it may be understood that the geometry of rectangular profile 286 may vary in other embodiments.

[0074] As with the serrations 140 shown in Figures 4 and 5, serrations 340 of legs 330 are generally configured to bite into the inner surfaces of holes formed in opposing bone segments (e.g., holes 14 and 16 of bone segments 2 and 4 of Figure 1 ) to secure or anchor the staple-style implant 300 to the bone segments. In this exemplary embodiment, serrations 340 project outwardly from the outer surface 331 of each leg 330 along the side of the leg 330. In other words, a maximum cross-sectional area of each outwardly projecting serration 340 may be greater than the cross-sectional area of each leg 330. In this exemplary embodiment, each serration 340 includes or is defined by one or more curved engagement features such as curved engagementsurfaces or edges intended to maximize the area of contact between the given serration 340 and the bone segment engaged by the serration 340. The curved engagement features of each serration 340 may curve in a direction generally parallel and / or perpendicular with the central axis 335 of the leg 330 comprising the serration 340. Additionally, in this exemplary embodiment, the curved engagement features of serrations 340 may comprise “draft” features designed (prior to manufacturing) by pulling a selected plane along a vector extending normal to the selected plane. The curved engagement features of serrations 340, being draft surfaces, have a different curved surface geometry from the curved engagement surfaces 142 of serrations 140 described above which may instead comprise revolved surfaces. However, it may be understood that the curved engagement features may not comprise draft features in other embodiments, and instead may be formed in other ways such as via revolving the features as described in greater detail above.

[0075] In this embodiment, implant 300 is made of a Nitinol material, and thus, can be heat treated and programed, as discussed above, to have shape memory and superelastic / pseudoelastic characteristics such that implant 300 may be classified as a superelastic shape memory implant, and may transform from one shape to another when exposed to heat.

[0076] In general, embodiments of staple-style implants disclosed herein (e.g., implants 100, 200, 250, and 300) can be held, retained, manipulated, and installed in bone or other anatomical site using any suitable and compatible insertion devices or instruments. Insertion devices (not shown) for installing the staple-style implants disclosed herein can be operated by a surgeon or other user to securely hold the implant such as during installation in bone segments 2, 4, and selectively release the implant after installation in bone segments 2 and 4. Thus, insertion devices for installing the staple-style implants disclosed herein may be described has having a first or closed configuration for securely gripping and holding the implant (e.g., for and during installation), and a second or open configuration for disengaging and releasing the implant (e.g. following installation).

[0077] In the manner described, embodiments disclosed herein include staple-style implants that may include rounded or partially rounded legs that maximize strength within a given drilled hole. In addition, some embodiments disclosed herein include axially spaced serrations formed on the legs of the implant, the serrations defined by one or more curved surfaces or features configured to maximize the surface area of theserration in contact with a bone segment when the implant is coupled to the bone segment.

[0078] While exemplary embodiments have been shown and described, modifications thereof can be made by one skilled in the art without departing from the scope or teachings herein. The embodiments described herein are exemplary only and are not limiting. Many variations and modifications of the systems, apparatus, and processes described herein are possible and are within the scope of the disclosure. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims. Unless expressly stated otherwise, the steps in a method claim may be performed in any order. The recitation of identifiers such as (a), (b), (c) or (1 ), (2), (3) before steps in a method claim are not intended to and do not specify a particular order to the steps, but rather are used to simplify subsequent reference to such steps.

Claims

CLAIMSWhat is claimed is:1 . A shape-memory alloy orthopedic implant for coupling a pair of bone segments, the shape-memory alloy orthopedic implant comprising: a bridge having a longitudinal axis, a first end, and a second end opposite the first end, wherein the bridge has a radially outer surface extending axially from the first end to the second end; a first leg extending from the first end of the bridge, wherein the first leg has a central axis, a fixed end fixably attached to the bridge, a free end distal the bridge, and a radially outer surface extending axially from the fixed end of the first leg to the free end of the first leg; and a second leg extending from the second end of the bridge, wherein the second leg has a central axis, a fixed end fixably attached to the bridge, a free end distal the bridge, and a radially outer surface extending axially from the fixed end of the second leg to the free end of the second leg; wherein a plurality of axially spaced serrations are formed on the radially outer surface of the first leg and the radially outer surface of the second leg, wherein each serration comprises a curved engagement surface and a curved engagement shoulder for forming an interference fit with the pair of bone segments.

2. The shape-memory alloy orthopedic implant of claim 1 , wherein the curved engagement surface of each serration has a shape extending along a curved longitudinal axis of the curved engagement surface between a distal edge and a tip opposite the distal edge along the longitudinal axis of the curved engagement surface.

3. The shape-memory alloy orthopedic implant of claim 2, wherein the curved engagement shoulder extends along the distal edge of the curved engagement surface and is curved along a longitudinal axis of the curved engagement shoulder that extends in the direction of the curved engagement surface.

4. The shape-memory alloy orthopedic implant of claim 3, wherein the curved engagement shoulder projects concavely along the longitudinal axis of the curved engagement surface.

5. The shape-memory alloy orthopedic implant of claim 2, wherein the curved engagement surface projects convexly along the longitudinal axis of the curved engagement surface.

6. The shape-memory alloy orthopedic implant of claim 1 , wherein the curved engagement surface of each serration comprises a pair of opposing lateral sides and a curved lateral axis extending between the pair of lateral sides, the lateral axis of the curved engagement surface extending perpendicular to either the central axis of the first leg or the central axis of the second leg.

7. The shape-memory alloy orthopedic implant of claim 1 , wherein the plurality of serrations formed on the radially outer surface of the second leg face the plurality of serrations formed on the radially outer surface of the first leg.

8. The shape-memory alloy orthopedic implant of claim 1 , wherein the central axis of the first leg is not parallel to the central axis of the second leg.

9. The shape-memory alloy orthopedic implant of claim 1 , wherein the longitudinal axis of the bridge, the central axis of the first leg, and the central axis of the second leg are disposed in a common reference plane.

10. The shape-memory alloy orthopedic implant of claim 9, wherein the orthopedic implant has a central axis disposed in the common reference plane, positioned between the central axes of the first leg and the second leg, and intersecting the longitudinal axis of the bridge, wherein the first leg is oriented at a leg angle a measured in the common reference plane between the central axis of the first leg and the central axis of the orthopedic implant, wherein the leg angle a is between approximately 0° and approximately 20°.

11. A shape-memory alloy orthopedic implant for coupling a pair of bone segments, the shape-memory alloy orthopedic implant comprising: a bridge having a longitudinal axis, a first end, and a second end opposite the first end, wherein the bridge has a radially outer surface extending axially from the first end to the second end; a first leg extending from the first end of the bridge, wherein the first leg has a central axis, a fixed end fixably attached to the bridge, a free end distal the bridge, and a radially outer surface extending axially from the fixed end of the first leg to the free end of the first leg; and a second leg extending from the second end of the bridge, wherein the second leg has a central axis, a fixed end fixably attached to the bridge, a free end distal the bridge, and a radially outer surface extending axially from the fixed end of the second leg to the free end of the second leg; wherein a plurality of axially spaced serrations are formed on the radially outer surface of the first leg and the radially outer surface of the second leg, wherein each serration comprises a curved engagement surface that is curved along a lateral axis of the curved engagement surface, the lateral axis of the curved engagement surface extending perpendicular to either the central axis of the first leg or the central axis of the second leg.

12. The shape-memory alloy orthopedic implant of claim 11 , wherein the curved engagement surface of each serration comprises a revolved surface.

13. The shape-memory alloy orthopedic implant of claim 11 , wherein the curved engagement surface projects convexly along the lateral axis of the curved engagement surface.

14. The shape-memory alloy orthopedic implant of claim 11 , wherein the curved engagement surface of each serration extends along a curved longitudinal axis of the curved engagement surface between a distal edge and a tip opposite the distal edge along the longitudinal axis of the curved engagement surface.

15. The shape-memory alloy orthopedic implant of claim 14, wherein each serration comprises a pair of the curved engagement surfaces which share an edge formed between the pair of curved engagement surfaces.

16. The shape-memory alloy orthopedic implant of claim 11 , wherein each serration comprises a curved engagement shoulder flanking the curved engagement surface for forming an interference fit with the pair of bone segments.

17. The shape-memory alloy orthopedic implant of claim 16, wherein the curved engagement shoulder is curved along a longitudinal axis of the curved engagement shoulder that extends in the direction of the curved engagement surface.

18. The shape-memory alloy orthopedic implant of claim 17, wherein the curved engagement surface projects convexly along the longitudinal axis of the curved engagement surface.

19. The shape-memory alloy orthopedic implant of claim 16, wherein each serration comprises a pair of the curved engagement shoulders which share a crest extending in the direction of the curved engagement surface.

20. The shape-memory alloy orthopedic implant of claim 11 , wherein the plurality of serrations formed on the radially outer surface of the second leg face the plurality of serrations formed on the radially outer surface of the first leg.

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