Abstract:
Disclosed bone screws include multiple screw elements engaged together to provide the required strength along a longitudinal direction and the required flexibility in other degrees of freedom. The disclosed bone screws have a low profile. Further, the bone screws allow fine-tuning of the compression to be applied to bones or joints. Instrumentation for implanting and orienting the bone screws is also disclosed herein.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to systems, apparatuses, methods, and kits for joint repair. Specifically, this disclosure relates to syndesmosis fixation apparatuses, systems, kits, and methods suitable to accommodate or correct various patient deformities. 
       BACKGROUND 
       [0002]    A syndesmosis joint is formed by an interosseous membrane connecting the fibula to the tibia. The syndesmosis joint is a slightly movable articulation where the contiguous bony surfaces are united by the interosseous ligament. If undue stress is put on the ankle joint, the joint may fracture, with either the fibula or tibia fracturing, or possibly both. Syndesmotic injuries to the ankle occur in approximately 10% of cases of ankle fractures. However, these injuries can also occur with soft-tissue injuries in the absence of fracture. They usually result from severe external rotation of the ankle. If the syndesmosis is torn apart, the syndesmosis joint needs to be stabilized by holding the joint in position until the articulation heals. Surgeons often fix the relevant bones together with a syndesmotic screw, temporarily replacing the syndesmosis. The screw inhibits normal movement of the bones and, therefore, the corresponding joint. When the natural articulation is healed, the screw may be removed. Alternatively, surgeons use an elastic fiber wire loop tensioned and secured between metallic buttons to provide physiologic stabilization of the joint. This technique allows physiologic motion of the ankle. 
         [0003]    However, the syndesmotic screws are prone to fracture at the fulcrum of the screw around which the fibular side of the screw rotates during gait because they are inflexible in all degrees of freedom. Further, the elastic fiber wire loop may cause an inflammatory reaction, and the buttons used in the fixation may cause soft tissue irritation. Therefore, the existing systems and procedures for syndesmosis repair may not be as effective as desired. 
       SUMMARY 
       [0004]    The present disclosure relates to bone and joint fixation, and instrumentation and methods for preparation and implantation of these devices. Joint fixation may be necessary in cases of pain and inflammation due to cartilage degeneration, nerve impingement, spinal misalignment, and motion instability. The primary examples described herein illustrate how this concept is applied to the syndesmosis joint, but this concept applies equally to other joints where similar causes of pain and inflammation are indicated. The disclosed bone screw includes a first screw element and a second screw element inserted through the first screw element and engaged therewith. Each of the first screw element and second screw element include an external thread for threaded engagement with a bone. Further, the first screw element is capable of being selectively adjusted to achieve a required compression. The bone screw when secured to the tibia and the fibula provides resistance to distraction of the syndesmosis joint. The disclosed bone screw has a low profile and is less expensive than other systems. Further, the disclosed bone screw is intrinsically stronger than a standard screw as it provides only a limited resistance to bending movement. 
         [0005]    Those of skill in the art will recognize that the following description is merely illustrative of the principles of the disclosure, which may be applied in various ways to provide many different alternative embodiments and may be applicable outside the fields of surgery or medical devices. While the present disclosure is made in the context of syndesmosis joints for the purposes of illustrating the concepts of the design, it is contemplated that the present design and/or variations thereof may be suited to other uses, such as to support other joints in the human body and to stabilize bone fractures. Moreover, the implants, instrumentation, and methods set forth herein may be used in open, percutaneous, and/or minimally invasive procedures. 
         [0006]    All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Various embodiments of the present disclosure will now be discussed with reference to the appended drawings. It will be appreciated that these drawings depict only typical examples of the present disclosure and are, therefore, not to be considered limiting of its scope. 
           [0008]      FIG. 1A  is a left-side view of a bone screw in accordance with one example of the present disclosure; 
           [0009]      FIG. 1B  is a right-side view of a bone screw in accordance with another example of the present disclosure; 
           [0010]      FIG. 1C  is an isometric left-side view of the bone screw in  FIG. 1A ; 
           [0011]      FIG. 1D  is an isometric right-side view of the bone screw in  FIG. 1B ; 
           [0012]      FIG. 2A  shows a first screw element and a second screw before they are assembled together; 
           [0013]      FIG. 2B  shows a bone screw assembly after the first screw element and the second screw are assembled together; 
           [0014]      FIG. 3A  is a side view of a bone screw in accordance with another example of the present disclosure; 
           [0015]      FIG. 3B  is a cross-section view of the bone screw in  FIG. 3A  taken along the lines of  3 B- 3 B of  FIG. 3A ; 
           [0016]      FIG. 4  is a side view of a bone screw in accordance with another example of the present disclosure; 
           [0017]      FIG. 5A  is a side view of a second screw element of the bone screw in  FIG. 1A ; 
           [0018]      FIG. 5B  is a section view of the second screw element of the bone screw in  FIG. 5A  taken along lines  5 B- 5 B of  FIG. 5A ; 
           [0019]      FIG. 5C  is an enlarged view of a portion  5 C marked in  FIG. 5B ; 
           [0020]      FIG. 5D  is a top view of the second screw element of  FIG. 5A ; 
           [0021]      FIG. 6A  is an isometric view of a first screw element of the bone screw in  FIG. 1A ; 
           [0022]      FIG. 6B  is a top view of the first screw element in  FIG. 6A ; 
           [0023]      FIG. 6C  is a side view of the first screw element in  FIG. 6A ; 
           [0024]      FIG. 6D  is a cross-section view of the first screw element in  FIG. 6C  taken along lines  6 D- 6 D of  FIG. 6C ; 
           [0025]      FIG. 7A  is a cross-section view along a longitudinal axis of the bone screw in  FIG. 1A ; 
           [0026]      FIG. 7B  is a top view of the bone screw in  FIG. 7A ; 
           [0027]      FIG. 8A  is a cross-section view along a longitudinal axis of a bone screw in  FIG. 1B ; 
           [0028]      FIG. 8B  is a top view of the bone screw in  FIG. 8A ; 
           [0029]      FIG. 9A  is a top view of a driver to install the bone screw in  FIG. 8A ; 
           [0030]      FIG. 9B  is an isometric view of the driver in  FIG. 9A ; 
           [0031]      FIG. 10  shows a portion of a foot with the bone screw inserted across the syndesmosis joint according to the present disclosure; and 
           [0032]      FIG. 11  is a flowchart illustrating a method for inserting a bone screw into the pair of bones, according to one aspect of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0033]    While certain embodiments are shown and described in detail below by way of illustration only, it will be clear to the person skilled in the art upon reading and understanding this disclosure that changes, modifications, and variations may be made and remain within the scope of the technology described herein. Further, while various features are grouped together in the embodiments for the purpose of streamlining the disclosure, it is appreciated that features from different embodiments may be combined to form additional embodiments which are all contemplated within the scope of the disclosed technology. 
         [0034]    Not every feature of each embodiment is labeled in every figure where that embodiment appears, in order to keep the figures clear. Similar reference numbers (for example, those that are identical except for the first numeral) may be used to indicate similar features in different embodiments. 
         [0035]    Any of the devices described herein may be fabricated from metals, alloys, polymers, plastics, ceramics, glasses, composite materials, or combinations thereof, including but not limited to: PEEK, titanium, titanium alloys, commercially pure titanium grade 2, ASTM F67, Nitinol, cobalt chrome, stainless steel, UHMWPE, and biodegradable materials, among others. Different materials may be used within a single part. The implants disclosed herein may also encompass a variety of surface treatments or additives to encourage bony attachment, including but not limited to: porous coatings, hydroxyapatite, TCP, anti-microbial additives, analgesics, anti-inflammatories, BMP&#39;s, PMA material, bone growth promoting material, PLLA (poly-L-lactide), PGA (polyglycolide), TCP (tricalcium phosphate), demineralized bone, cancellous bone chips, etc. Any implant disclosed herein may include a radiographic marker for imaging purposes. Any implant disclosed herein may be colored, coded, or otherwise marked to make it easier for the surgeon to identify the type and size of the implant. 
         [0036]      FIGS. 1A-1D  illustrate one example of a bone screw  100  useful for fixing a bone fracture or a joint. The bone screw  100  includes a first screw element  102  and a second screw element  104 . The first screw element  102  includes an external thread  106  with a first thread pitch. The second screw element  104  includes a shaft  108 . The second screw element  104  may have a fully threaded shaft or a thread configuration with a lag (as shown in  FIGS. 1A-1D ). Accordingly, the shaft  108  includes a threaded portion  110 . The threaded portion  110  may partially taper toward the tip of the second screw element  104 . Further, the threaded portion  110  may include an external thread  112  with a second thread pitch. The external thread  106  and the external thread  112  allow the bone screw  100  to have a threaded engagement with one or more bones. When used to stabilize the syndesmosis joint, the external thread  106  engages with the fibula and the external thread  112  engages with the tibia. The first thread pitch and the second thread pitch may be the same. In another example, the first pitch and the second pitch may be different to provide compression along the screw. 
         [0037]    Further, the first screw element  102  includes a self-tapping feature  114  (or self-threading) to tap a drilled hole when the bone screw  100  is inserted into the one or more bones. Similarly, the second screw element  104  includes a self-tapping feature  116 . Further, the second screw element  104  is cannulated down its center so that it can be placed into the one or more bones with a Kirschner wire (K-wire). The first screw element  102  and the second screw element  104  are explained in further detail in conjunction with  FIGS. 6A-6D  and  5 A- 5 D below, respectively. 
         [0038]    Referring now to  FIG. 2A , the second screw element  104  is inserted through the first screw element  102  and engaged therewith to obtain the bone screw  100 . The first screw element  102  may have a partial spherical-shaped capsule to receive a complementarily shaped partial spherical fastener head  202  of the second screw element  104 . The engagement between the first screw element  102  and the second screw element  104  prevents distraction along the longitudinal axis of the bone screw  100  but permits motion in one or more other degrees of freedom. 
         [0039]    As shown in  FIG. 1D , the engagement between the first screw element  102  and the second screw element  104  permits the second screw element  104  to be moved by an angle  118  of 0 to 15 degrees with respect to a coaxial alignment with the first screw element  102 . Further, as shown in  FIGS. 2A and 2B , the first screw element  102  allows the fastener head  202  to be recessed within the first screw element  102  to provide a smooth, low-profile implant. A smooth, low-profile implant can help reduce irritation to surrounding soft tissue. This example is explained in further detail in conjunction with  FIGS. 4 ,  5 ,  6 , and  7  below. 
         [0040]    In a second example depicted in  FIG. 3A  and  FIG. 3B , a bone screw  300  is shown comprising a first screw element  302  engaged with a second screw element  304 . In this example, the second screw element  304  includes a partial spherical-shaped capsule  306  to receive a complementarily shaped, partial spherical fastener head  308  of the first screw element  302 . 
         [0041]    Referring back to  FIG. 1B , the first screw element  102  also includes a stiffness reduction hole  120 , near the distal end of the first screw element  102 , such that the stiffness reduction hole  120  is placed on the side portion of the first screw element  102  for securely engaging the second screw element  104  with the first screw element  102 . The first screw element  102  may include a plurality of stiffness reduction holes arranged in line with the stiffness reduction hole  120 , on the circumference of the first screw element  102 . Alternatively, as shown in  FIG. 4A , the first screw element  102  may include one or more slits  402  on the distal end, such that the one or more slits  402  are aligned along the side portion of the first screw element  102  for securing the second screw element  104  with the first screw element  102 . 
         [0042]    Further, the first screw element  102  and the second screw element  104  may engage using one of a ball joint, a yoke joint, a universal joint, and a flat slider plate joint. Accordingly, the first screw element  102  and the second screw element  104  are suitably modified to engage with the used joint. Alternatively, a dumbbell element is placed between the first screw element  102  and the second screw element  104 . The first screw element  102  and the second screw element  104  are suitably modified to receive one ball of the dumbbell element each, with a similar partial spherical-shaped capsule as described in conjunction with  FIG. 2  above. The dumbbell element provides an additional set of degrees of freedom to the bone screw  100 . Moreover, the first screw element  102  may be further secured to the second screw element  104  using a set screw. 
         [0043]    Referring now to  FIG. 5A , a second screw element  502  is shown with an external thread  504  and a partial spherical fastener head  506 .  FIG. 5B  shows a cross section view along the line  5 B- 5 B of  FIG. 5A .  FIG. 5C  shows an enlarged view of a portion marked “ 5 C” in  FIG. 5B  illustrating a hexalobe drive  508 .  FIG. 5D  shows a top view of the second screw element  502  of  FIG. 5A . 
         [0044]    Referring now to  FIG. 6A , a first screw element  602  is shown with an external thread  604  and a three-slot drive  606 .  FIG. 6B  shows a top view of the first screw element  602  of  FIG. 6A .  FIG. 6C  shows a side view of the first screw element  602 .  FIG. 6D  shows a cross-section view along the line  6 D- 6 D of  FIG. 6C . A partial spherical-shaped capsule  608  is provided to receive the complementarily shaped, partial spherical fastener head  506  to obtain the bone screw of the present disclosure. 
         [0045]      FIGS. 7A-7B ,  8 A- 8 B show two examples of drives that may be used in accordance with some examples of the present disclosure.  FIG. 7A  shows a cross-section view along a longitudinal axis of a bone screw  700 , obtained after inserting a second screw element  702  through the first screw element  704  and engaged therewith. A partial spherical-shaped capsule  706  of the first screw element  704  receives a complementarily shaped, partial spherical fastener head  708  of the second screw element  702 . Further, the first screw element  704  includes a three-slot drive  710 . The second screw element  702  includes a hexalobe drive  712 .  FIG. 7B  shows a top view of the bone screw  700 . A stepped driver is used to simultaneously engage both the three-slot drive  710  and the hexalobe drive  712 . A separate driver is used to engage only the three-slot drive  710  to selectively adjust the first screw element to achieve desired compression between bones. 
         [0046]      FIG. 8A  shows a cross-section view along a longitudinal axis of a bone screw  800 , a obtained after inserting a second screw element  802  through a first screw element  804  and engaged therewith.  FIG. 8B  shows a top view of the bone screw  800 . The first screw element  804  includes a stiffness reduction hole  806  on distal end of the first screw element  804 . The stiffness reduction hole  806  allows for securely engaging the second screw element  802  with the first screw element  804 . Further, the first screw element  804  includes a hex drive  808 . The hex drive  808  may also include a tab  810  on each edge of the drive to allow a driver to engage with the first screw element  804 . In addition, the tab  810  interacts with the driver to hold the first screw element in a specific orientation during insertion. The second screw element  802  includes a hexalobe drive  812 . 
         [0047]    Referring now to  FIG. 9A  showing a top view of a driver  900  that may be used to install the bone screw  800  in the bone.  FIG. 9B  shows an isometric view of the driver  900 . The driver  900  includes two arms  902  and  904 . One end of the arm  902  is partially inserted into a receptacle  906  in the side of the arm  904  and removably secured therewith. The other end of the arm  902  includes a stepped drive bit  908 , comprising a first drive bit  910  that engages with the hex drive  808  and a second drive bit  912  that engages with the hexalobe drive  812 . Further, one end of the arm  904  includes a drive bit  914  that engages only with the hex drive  808 . A similar driver may be used for the bone screw  700 , wherein instead of the first drive bit  910  and the drive bit  914 , an alternative drive bit is used that engages with the three-slot drive  710 . 
         [0048]    A bone screw kit or system comprises a plurality of bone screws, wherein each bone screw includes a first screw element and a second screw element inserted through the first screw element and engaged therewith. The kit further includes at least one drill to provide clearance for both the first screw element and the second screw element in at least one bone, a first driver to drive the bone screw into the at least one bone, such that external thread on each of the first screw element and second screw element engages with the at least one bone, wherein the first driver is a stepped driver and the second driver selectively adjusts the first screw element to achieve a required compression. 
         [0049]    Further, the at least one drill of the bone screw kit includes a cannulated major drill to provide clearance for the shaft of the second screw element, a cannulated minor drill to provide clearance for the threaded portion of the second screw element and a cannulated reamer to provide clearance for the first screw element. 
         [0050]    Moreover, each bone screw in the kit is of a different configuration, wherein the configuration of a bone screw is defined by one or more parameters including a major diameter, a pitch, a length, a lag thread, and a drive connection. The bone screw kit may further include one or more of a K-wire, one or more tapping tools capable of accommodating all bone screws in the kit, and one or more driving tools. 
         [0051]      FIG. 10  shows an example of the placement of the bone screw  100  across a syndesmosis joint  1002  between a tibia  1004  and a fibula  1006 . The shown placement of the bone screw  100  is easily achievable with the screw features, guides, drivers, and instrumentation disclosed herein. The external thread  112  of the second screw element  104  engages with the tibia  1004  and the external thread  106  of the first screw element  102  engages with the fibula  1006 . The first screw element  102  may be made of PolyEther Ether Ketone (PEEK) and the second screw element  104  may be made of a titanium alloy. 
         [0052]    As shown, the bone screw  100  when installed in the bones has a zero profile, which helps reduce irritation to surrounding soft tissue. Further, the fibula  1006  provides a measure of resistance to disengagement of the first screw element  102  and the second screw element  104 . In addition, the joint between the first screw element  102  and the second screw element  104  allows for normal fibular motion, thereby reducing the chances of fracture of the bone screw  100 . Further, the first screw element  102  may be selectively adjusted to fine-tune the syndesmosis compression. 
         [0053]    A method  1100  of inserting the bone screw  100  into the pair of bones, including a first bone and a second bone as disclosed herein, is described in  FIG. 11 . As shown in  FIG. 10 , the pair of bones includes the tibia  1004  and the fibula  1006 . At step  1102 , a surgeon inserts a guide wire (for example, a K-wire) to a desired location into the foot of a patient. In one example, the K-wire is inserted such that it reaches the fibula  1006 . Once the guide wire is in the desired location, the surgeon may insert a dilator over the guide wire into the soft tissue of the patient to provide sufficient access to the bones. Once the tissue is dilated, the surgeon removes the dilator thus exposing the bones for the remainder of the surgery. 
         [0054]    Next at step  1104 , the surgeon guides a cannulated major drill over the guide wire to drill through the fibula  1006  and then through the tibia  1004 . The major drill provides clearance for the shaft  108  (major diameter) of the second screw element  104 . Then at step  1106 , the surgeon uses a cannulated minor drill to provide clearance for threaded portion  110  (minor diameter). Further, at step  1108 , the surgeon uses a fibular reamer to ream the fibula to provide clearance for the first screw element  102 . The cannulated major drill, the cannulated minor drill and fibular reamer may be manually operated or may be operated by, or as, powered devices. 
         [0055]    Once the implant site is sufficiently prepared to receive the bone screw  100 , the guide wire is used to orient and insert the bone screw  100  into the fibula  1006  and the tibia  1004 , at step  1110 . The surgeon uses a first screwdriver that engages with both the first screw element  102  and the second screw element  104  to insert the bone screw  100  into the fibula  1006  and the tibia  1004 . For example, if the bone screw  100  has a drive arrangement as shown in  FIG. 8B , then the surgeon uses the stepped drive bit  908  of the driver  900  to engage with both the first screw element  102  and the second screw element  104 . The self-tapping feature  114  and the self-tapping feature  116  tap the bones as the surgeon inserts the bone screw  100  into the fibula  1006  and the tibia  1004 . The first screw element  102  engages with the fibula  1006  and the second screw element  104  engages with the tibia  1004 . 
         [0056]    Finally, at step  1112 , the surgeon selectively adjusts the first screw element  102  to achieve a required compression between the bones. The surgeon uses a second screwdriver to selectively adjust the first screw element  102 . The second screwdriver engages the first screw element  102  only. For example, if the bone screw  100  has a drive arrangement as shown in  FIG. 8B , then the surgeon uses the driver bit  914  of the driver  900  to engage with the first screw element  102  only. Then, the surgeon may use a set screw to further secure the engagement of the first screw element  102  and the second screw element  104 . 
         [0057]    Once the bone screw  100  is in the proper location, the surgeon can remove the guide wire, the drivers, and any other instrumentation used, and then close the incision site. 
         [0058]    It should be understood that the present components, systems, kits, apparatuses, and methods are not intended to be limited to the particular forms disclosed. Rather, they are intended to include all modifications, equivalents, and alternatives falling within the scope of the claims. They are further intended to include embodiments which may be formed by combining features from the disclosed embodiments, and variants thereof. 
         [0059]    The claims are not to be interpreted as including means-plus- or step-plus-function limitations, unless such a limitation is explicitly recited in a given claim using the phrase(s) “means for” or “step for,” respectively. 
         [0060]    The term “coupled” is defined as connected, although not necessarily directly, and not necessarily mechanically. 
         [0061]    The use of the word “a” or “an” when used in conjunction with the term “comprising” in the claims and/or the specification may mean “one,” but it is also consistent with the meaning of “one or more” or “at least one.” The term “about” means, in general, the stated value plus or minus 5%. The use of the term “or” in the claims is used to mean “and/or” unless explicitly indicated to refer to alternatives only or the alternative are mutually exclusive, although the disclosure supports a definition that refers to only alternatives and “and/or.” 
         [0062]    The terms “comprise” (and any form of comprise, such as “comprises” and “comprising”), “have” (and any form of have, such as “has” and “having”), “include” (and any form of include, such as “includes” and “including”), and “contain” (and any form of contain, such as “contains” and “containing”) are open-ended linking verbs. As a result, a method or device that “comprises,” “has,” “includes,” or “contains,” one or more steps or elements, possesses those one or more steps or elements, but is not limited to possessing only those one or more elements. Likewise, a step of a method or an element of a device that “comprises,” “has,” “includes,” or “contains” one or more features, possesses those one or more features, but is not limited to possessing only those one or more features. Furthermore, a device or structure that is configured in a certain way is configured in at least that way, but may also be configured in ways that are not listed. 
         [0063]    The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. It is appreciated that various features of the above-described examples can be mixed and matched to form a variety of other alternatives. As such, the described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.