Patent ID: 12256968

DETAILED DESCRIPTION

The present disclosure provides a bone screw with a spring component that enables a surgeon to measure the amount of compression effected by the bone screw during installation and dynamically maintain that compression across the provided bone screw during healing of a fracture. The provided bone screw includes a leading component, a trailing component, and a spring component that may be compressed between the leading component and the trailing component. The leading component and the trailing component are each constructed so as to effect compression between two boney structures when installed in bone. For example, the leading component may include two separate exteriorly threaded regions that have variable pitch threading and/or the trailing component may include a tapered body having constant pitch exterior threading.

The spring component may be positioned around a non-threaded region of the leading component and within the trailing component. The spring component may be attached to one of the leading component or the trailing component and be merely in contact with a surface of the other. This configuration enables the leading component and the trailing component to rotate relative to one another without twisting the spring component. When the provided bone screw is installed in bone, and the leading component or the trailing component is advanced or receded within the bone, the relative displacement between the leading component and the trailing component is altered. The altered relative displacement between the leading component and the trailing component causes an increase or decrease in the compression of the spring component. Accordingly, a compression force effected by the provided bone screw can be adjusted by advancing or receding either the leading component or the trailing component in bone. The adjustable compression force enables a surgeon to set a desired compression force across a fracture.

The active spring component additionally creates dynamic compression that helps enable the desired compression force to be maintained across the fracture during healing. For instance, the spring component's flexibility helps prevent or reduce the occurrences of screw stripping, pullout or failure that may occur with at least some typical bone screws when the fracture location is stressed. An advantage of the presently disclosed bone screw is that it provides the benefits of an active spring component while also maintaining the bone screw's axial rigidity, since the spring component is positioned around the leading component. The maintained axial rigidity helps the provided bone screw withstand greater loads when installed in bone as compared to at least some typical bone screws having a spring component.

In order to adjust the compression that the provided bone screw effects, the bone screw may be used with driving components particularly adapted for the provided bone screw. For example, a first driving component may be adapted to engage both a driver feature of the leading component and a driver feature of the trailing component at the same time so that both the leading and trailing components can be rotated together and be advanced or receded in bone together. This first driving component may be used to initially insert the bone screw and adjust the bone screw as a whole if needed. A second driving component may be adapted to engage only the leading component's driver feature or only the trailing component's driver feature so that only one component is rotated to the exclusion of the other. This second driving component enables altering the relative displacement between the leading component and the trailing component in bone and therefore may be used to adjust the compression force effected by the bone screw. In some instances, a third driving component may be adapted to engage the other of the leading component's driver feature or the trailing component's driver feature than the second driving component.

The present disclosure also provides a measurement tool that may be used to measure an amount of compression force effected by an installed bone screw. The provided measurement tool measures a displacement between the leading component and trailing component. This displacement may be converted to a compression force based on a spring constant of the spring component. In combination, the provided bone screw, driving components, and measurement tool enable a surgeon to set a desired compression force across a fracture for healing. Additional advantages of the provided bone screw, driving components, and/or measurement tool will be apparent from the following description of the figures.

Reference is made herein to a surgeon. It should be appreciated that a surgeon may alternatively be any other suitable healthcare professional or other user of the provided bone screw and systems.

FIGS.1A to1Cillustrate an example bone screw100. In at least some aspects, the bone screw100includes a leading component102, a spring component104, and a trailing component106. The components of the bone screw100may be adapted to effect compression across a fracture when the bone screw100is installed in bone across the fracture.FIG.1Aillustrates an exploded view of the bone screw100showing each of the leading component102, the spring component104, and the trailing component106separately. In at least some aspects, the leading component102includes a shaft having a cutting tip108at its distal end. In various examples, the cutting tip108may be self-cutting. In at least some aspects, the shaft of the leading component102may be cannulated, as shown by the channel134in the illustrated aspect.

In at least some aspects, the shaft of the leading component102includes exterior threading that contributes to effecting compression between two bone fragments. For example, the leading component102may include an exteriorly threaded region110. In some instances, the leading component102may include an exteriorly threaded region112. The threads in the exteriorly threaded region110and/or the exteriorly threaded region112may have a variable pitch in various instances. In an example, the pitch of the exterior threads of the leading component102may be greatest nearest the distal end (e.g., the cutting tip108) of the leading component102and may decrease moving away from the distal end through the exteriorly threaded region110and the exteriorly threaded region112. The pitch of the exterior threads is measured between corresponding points on consecutive thread crests. In another example, the crest radius of the exterior threads of the leading component102may be greatest nearest the distal end of the leading component102. For instance, the threads in the exteriorly threaded region110may have a greater crest radius than the threads in the exteriorly threaded region112. The crest radius of the exterior threads is measured from a central axis of the leading component102to an outermost point on an exterior thread.

In at least some aspects, the leading component102may include a non-threaded region114. For example, the non-threaded region114may have a smooth exterior surface. In various instances, the non-threaded region114terminates at a ridge116. The ridge116extends outward from the exterior surface of the shaft of the leading component102. In at least some aspects, the shaft of the leading component at its proximal end includes a driver feature118. The driver feature118may have any suitable configuration that enables it to be engaged by a component of a driving instrument. In the illustrated example, the driver feature118has a hexagonal-shaped outer perimeter.

The spring component104includes a leading end120opposite a trailing end124. Between the leading end120and the trailing end124, the spring component104includes an elastic portion122. In some aspects, such as the illustrated one, the elastic portion122may be a machined spring. In other aspects, the elastic portion122may be a coil spring or other suitable resilient elastic member. The spring component104may be positioned around the leading component102, such as around the non-threaded region114as illustrated inFIG.1B. The spring component104may be positioned within the trailing component106as illustrated inFIG.1C. As discussed more below, a property of the elastic portion122is a spring constant which is a factor in the amount of compression force effected by the bone screw100.

The trailing component106includes a body having a proximal end126opposite a distal end130. The trailing component106is constructed to help contribute to effecting compression between two bone fragments. For instance, the body of the trailing component106may be tapered such that the body has a greater diameter at its distal end130as compared to its proximal end126. The body of the trailing component106may include exterior threading128that has a constant pitch. In at least some aspects, the trailing component106includes a driver feature132initiating at its distal end130. The driver feature132may have any suitable configuration (e.g., a modified hexalobe) that enables it to be engaged by a component of a driving instrument.

In the constructed state of the bone screw100shown inFIG.1C, the leading component102and the trailing component106rotate independently of one another. In at least some aspects, the spring component104may be attached to either the leading component102or the trailing component106. For example, as best shown inFIG.1Bof the illustrated aspect, the trailing end124of the spring component104is in contact with, but is not attached to, the ridge116of the leading component102. The leading end120of the spring component104, on the other hand, is attached to the trailing component106. For example, the leading end120of the spring component104may be attached to the trailing component106by a weld or mechanical fit. In this example aspect, once the bone screw100is installed in bone, the spring component102rotates as a pair with the trailing component106, since they are attached to one another. The spring component102is able to rotate freely about the leading component102. Conversely, rotating the leading component102does not rotate the spring component102. Additionally, the ridge116prevents the trailing component106and spring component104attached pair from sliding off the leading component102.

In other aspects, the trailing end124of the spring component104may be attached to the leading component102, such as to the ridge116. In such other aspects, the trailing component106may include an interior ridge that contacts, but is not attached to, the leading end120of the spring component104(e.g., similar to the ridge116in the illustrated aspect). Additionally, in such other aspects, the interior ridge prevents the trailing component106from sliding off the leading component102and spring component104attached pair.

The above-described construction of the bone screw100enables an adjustable amount of compression force to be effected by the bone screw100by enabling an adjustable relative displacement between the leading component102and the trailing component104. For instance, when the bone screw100is installed in bone, the leading component102may be advanced or receded in the bone while the trailing component106remains stationary, or vice versa.FIG.2Aillustrates a cross section of the fully-constructed bone screw100shown inFIG.1C. In an example, the leading component102may be advanced (e.g., via a driving instrument engaging the driver interface118) in the direction of the arrow204. As the leading component102is advanced, it compresses the spring component104, an example result of which is illustrated inFIG.2B. The amount that the spring component104is compressed, and its spring constant, are factors in the amount of compression force effected by the bone screw100across a fracture.

The spring component104additionally creates dynamic compression across a fracture that helps enable a desired compression force to be maintained across the fracture during healing. For instance, when a typical compression screw without a spring component is installed across a fracture and the fracture site is stressed (e.g., a force attempts to move the two bone fragments relative to one another), this typical compression screw has minimal, or does not have any, give and thus stress may be concentrated at the interface of the typical compression screw's threads and the bone. Repeated stresses at the fracture site may cause stripping of this typical compression screw or pullout or failure. An advantage of the bone screw100is that the spring component104provides some give that removes some of the stress from the thread and bone interface and concentrates it in the spring component104. This helps reduce the occurrences of screw stripping, pullout or failure that may occur with the typical compression screw without a spring component. At the same time, the bone screw100maintains its axial rigidity and strength despite having a spring component, unlike at least some typical compression screws having a spring component, by positioning the spring component104around the leading component102. The axial rigidity and strength of the bone screw100helps it withstand greater loads than at least some typical compression screws having a spring component.

In some aspects, the bone screw100may be structured to be used in the elbow, wrist, foot, or ankle to apply dynamic compression of fractures, fusions and osteotomies. The elbow, wrist, foot, and ankle include boney structures with lower bone density and therefore may benefit from a screw that has some amount of give, such as the give provided by the spring component104of the bone screw100. In other aspects, the bone screw100may be structured to be used in the hip or shoulder. The boney structures in the hip and shoulder are larger than those in the elbow, wrist, foot, and ankle, and therefore a bone screw100structured for the hip or shoulder may be larger (e.g., a larger spring component104) and have a larger dynamic range than a bone screw100structured for the elbow, wrist, foot, or ankle. In other aspects still, the bone screw100may be structured for other suitable boney structures in a patient.

In various aspects, the bone screw100may be constructed of a suitable biocompatible material, such as titanium, stainless steel, or nitinol. In some examples, each of the leading component102, the spring component104, and the trailing component106may be constructed from the same suitable material. In other examples, at least one of the leading component102, the spring component104, or the trailing component106may be constructed from a suitable material different than the others.

As described above, the leading component102or the trailing component106of the bone screw100may be advanced or receded in bone independently of the other. To do so, driving components may be provided that are adapted for the leading and trailing components102and104of the bone screw100.FIG.3illustrates a perspective view of an example driving component300. The driving component300includes a shaft302. It should be appreciated that the shaft302may be any suitable length and might not be illustrated to scale. In some aspects, a trailing end306of the shaft302of the driving component300is adapted to connect to a driver or handle (e.g., for manual driving). For example, the trailing end306may be an AO connector as illustrated. In other aspects, the trailing end306of the shaft302may be integrally connected to a driver or handle. The driving component300may be constructed of a suitable biocompatible material.

In the illustrated example, the driving component300is constructed to engage both the driver interface118of the leading component102and the driver interface132of the trailing component106at the same time. For instance, the driving interface304is constructed to engage the driver interface132of the trailing component106and the driving interface308is constructed to engage the driver interface118of the leading component102. The driving component300may be positioned around the driver interface118and within the driver interface132. Engaging both the driver interface118of the leading component102and the driver interface132of the trailing component106at the same time enables a surgeon to advance the bone screw100as a whole into bone via the driving component300. For example, this may be done during initial insertion of the bone screw100.

FIG.4illustrates a perspective view of an example driving component400. The driving component400includes a shaft402. It should be appreciated that the shaft402may be any suitable length and might not be illustrated to scale. In some aspects, a trailing end406of the shaft402of the driving component400is adapted to connect to a driver or a handle (e.g., for manual driving). For example, the trailing end406may be an AO connector as illustrated. In other aspects, the trailing end406of the shaft402may be integrally connected to a driver or a handle. The driving component400may be constructed of a suitable biocompatible material.

In the illustrated example, the driving component400is constructed to engage only the driver interface118of the leading component102. For instance, the driving interface408is constructed to engage, and corresponds to, the driver interface118of the leading component102. The driving component400may be positioned around the driver interface118and within the driver interface132. The interface404, however, does not correspond to the driver interface132of the trailing component106and therefore does not engage the driver interface132. In some aspects, the interface404may be smooth as illustrated. Engaging only the driver interface118of the leading component102enables a surgeon to advance or recede only the leading component102via the driving component400. For example, the surgeon may advance or recede only the leading component102in order to adjust the compression force affected by the bone screw100.

In some aspects of the present disclosure, though not illustrated, a driving component may be provided that is constructed to engage only the driver interface132of the trailing component106. For example, in some instances, the interface404of the driving component400may be constructed such that it may engage, and corresponds to, the driver interface132of the trailing component106while the driving interface408may be constructed such that it does not correspond to, and therefore does not engage, the driver interface118of the leading component102. Engaging only the driver interface132of the trailing component106enables a surgeon to advance or recede only the trailing component106. For example, the surgeon may advance or recede only the trailing component106in order to adjust the compression force affected by the bone screw100.

In at least some instances, it is helpful for a surgeon to know how much compression force is applied across a fracture by a bone screw (e.g., the bone screw100). For example, with this information, the surgeon may adjust the leading component102or the trailing component106of the bone screw100to achieve a desired amount of compression force across the fracture.FIG.5Aillustrates an example measurement tool500for measuring compression force effected by a bone screw (e.g., the bone screw100) across a fracture. The measurement tool500includes a shaft502. The trailing end516of the shaft502may form any suitable end of the measurement tool500, such as a handle.

In various aspects, a rod510is positioned within the shaft502. In such aspects, the rod510may slide within the shaft502. In some examples, the rod510may be cannulated such that it includes a channel518(FIG.5B). A leading end of the shaft502includes an interface504and an interface506. In at least some aspects, the interface506is constructed to correspond to the driver interface118and/or the interface504is constructed to correspond to the driver interface132. This construction of the interface504and/or the interface506helps the measurement tool500remain in axial alignment with the bone screw100to achieve accurate measurements. In an initial position, prior to a measurement being taken, the rod510may be positioned towards the leading end of the shaft502. For example, an end of the rod510may be flush with the leading end of the shaft510.

To take a measurement, the measurement tool500may be placed around the leading component102(e.g., the driver interface118) and within the trailing component106(e.g., the driver interface132) of the bone screw100such that the driver interface118is within the interface506of the measurement tool500. In at least some aspects, the measurement tool500may be advanced into the trailing component106as far as the measurement tool500can be advanced. As this is done, the driver interface118of the trailing component106forces the rod510to slide within the shaft502of the measurement tool500. In at least some aspects, the rod510includes an indicator512, such as a line marking. In various aspects, the shaft502may include a window508through which the indicator512on the rod510is visible. In at least some examples, the shaft502includes a scale514adjacent to the window508. A measurement corresponds to where the indicator512lines up on the scale514. In at least some aspects, the measurement tool500measures a displacement between the leading component102and the trailing component106of the bone screw100. This displacement can be converted into an amount of compression force based on a spring constant of the spring component104. In some aspects, the scale514may include displacement values (e.g., millimeters). In other aspects, the scale514may include compression force values (e.g., Newtons).

In some aspects of the present disclosure, the measurement tool500may be its own separate component. In such aspects, a surgeon may take measurements with the measurement tool500when needed and use a separate driving component (e.g., the driving components300and400) to install or adjust the bone screw100. In other aspects of the present disclosure, the measurement tool500may be integrated with a driving component. For example, in such aspects, the measurement tool500may be constructed of one or more materials suitable to act as a driving component. Additionally, in such other aspects, a surgeon may install or adjust the bone screw100and take measurements with the same tool.

FIG.6shows a flow chart of an example method for compressing a bone fracture, according to an aspect of the present disclosure. Although the example method600is described with reference to the flow chart illustrated inFIG.6, it will be appreciated that many other methods of performing the acts associated with the method600may be used. For example, the order of some of the blocks may be changed, certain blocks may be combined with other blocks, and some of the blocks described are optional.

In some instances, the method600may begin by preparing a bone hole to receive a bone screw (e.g., the bone screw100) (block602). In some aspects, preparing the bone hole includes inserting a guidewire at the intended location for the bone screw100. A first drill or drill component may be used to create a hole in the bone (e.g., in the proximal cortex) having a profile similar to a posterior section (e.g., the trailing component106) of the bone screw100. A second drill or drill component may be used to create a hole in the bone having a profile similar to an anterior section (e.g., the leading component102) of the bone screw100. In at least some aspects, once the bone hole is prepared to receive the bone screw100, a desired length and/or diameter of the bone screw100is determined using radiographic imaging and/or a measurement instrument. A surgeon may then choose a bone screw100having the determined length and/or diameter.

In at least some aspects, the surgeon may insert the chosen bone screw100into the prepared bone hole via a first driving component (e.g., the driving component300) (block604). The driving component300engages both the leading component102(e.g., the driver interface118) and the trailing component106(e.g., the driver interface132) at the same time to enable the surgeon to advance the bone screw100as a whole into the bone hole. The surgeon may advance the bone screw100to a desired position across a fracture between two bone fragments.

In various instances, the surgeon may then measure a compression force effected by the inserted bone screw100(block606). For example, the surgeon may use the measurement tool500to measure the compression force effected by the inserted bone screw100. In some instances, the compression force effected by the inserted bone screw100may be adjusted via a second driving component (e.g., the driving component400) (bock608). For example, the measured compression force might not be equal to a compression force that the surgeon desires for healing a particular fracture. In this example, the driving component400engages only the leading component102(e.g., the driver interface118) to enable the surgeon to advance or recede only the leading component102. Doing so alters the relative displacement between the leading component102and the trailing component106, which adjusts the compression force effected by the bone screw100across the fracture. In other examples, a driving component may be used that engages only the trailing component106(e.g., the driver interface132), as described above, to adjust the compression force in a similar manner.

In some instances, after adjusting the compression force, the surgeon may again measure the compression force effected by the bone screw100. If the measured compression force is not the surgeon's desire compression force, then the surgeon may again adjust the compression force via a driving component that engages only the leading component102or only the trailing component106. As described above, in some aspects, the surgeon may adjust the compression force and measure the compression force using the same tool or driving component. Once the surgeon is satisfied with the compression force effected by the bone screw100across the fracture, the bone screw100is set and the fracture is allowed to heal.

The examples and aspects disclosed herein are to be construed as merely illustrative and not a limitation of the scope of the present disclosure in any way. It will be apparent to those having skill in the art that changes may be made to the details of the above-described examples without departing from the underlying principles discussed. In other words, various modifications and improvements of the examples specifically disclosed in the description above are within the scope of the appended claims. For instance, any suitable combination of features of the various examples described is contemplated.