Tapered compression screw with variable pitch for dynamic compression

Abstract

A bone screw having a resilient component is provided that allows a surgeon to measure the amount of compression due to the effect of the bone screw during installation and dynamically maintain that compression across the provided bone screw during fracture healing. The provided bone screw includes an anterior component, a posterior component, and a resilient component that can be compressed between the anterior and posterior components, positioned to maintain axial stiffness of the bone screw. The anterior and posterior components may be engaged with each other or independently by a screwing instrument. Advancing or retracting only the anterior component or only the posterior component changes the compression due to the effect of the bone screw between two bone fragments, allowing the surgeon to set the desired compression force. A measuring tool is further provided that can be used to measure the amount of compression due to the effect of an installed bone screw.

Description

Technical Field

[0001] Claim of Priority This application claims the benefit and priority of U.S. Provisional Application No. 63 / 112,425, filed on Nov. 11, 2020. The entire disclosure of this U.S. application is incorporated herein by reference.

[0002] This application generally relates to bone screws. More particularly, this application provides a new and innovative bone screw having an elastic component (e.g., a spring) and independently rotatable front and rear portions that enable measurement of compressive force and dynamic compressive maintenance.

Background Art

[0003] When promoting the healing of a fracture, it is desirable to compress the fracture site such that the fractured surfaces are pressed together. One common technique for compressing a fracture site is the use of bone screws that draw the fractured surfaces together to optimize the healing process.

[0004] When some common bone screws are used to fix two fragments together and the bone screw is tightened, the tension in the bone screw is initially very high and the fragments are held together. However, bone is a viscoelastic material and immediately after torque is applied to the bone screw, it causes a phenomenon known as stress relaxation. The stress relaxation response is very significant, leading to an immediate and rapid decrease in the tension of the bone screw, and thus a decrease in the force holding the fragments together. Further, after some common bone screws are tightened and the fragments are displaced in the lateral direction (e.g., by bending), the surrounding bone may break due to the rigidity of the bone screw because bone is less strong and rigid than the bone screw. This can lead to poor screw fixation, which can lead to nonunion or an undesirable healing of the two fracture surfaces.

[0005] Various bone screws exist that attempt to address stress relief. For example, U.S. Patent No. 4,959,064 and U.S. Patent No. 6,656,184 disclose bone screws with spring components that help adapt to stress relief in bone fragments, respectively. However, these bone screws are one-piece bone screws and do not allow for adjustable compression across the fracture site. In addition, common bone screws with spring components often lack axial rigidity because the spring component is tensed, which can limit the load that such bone screws can handle after being inserted into the bone and make them prone to breakage.

[0006] In other examples, U.S. Patents 7,582,107 and 7,794,483 disclose two-part bone screws that allow for adjustable compression across a fracture site by rotating the two parts relative to each other. However, these bone screws are prone to coming loose (for example, if overinserted), and may become dislodged or improperly fixed as the fracture healing progresses.

[0007] In another example, U.S. Patent No. 5,743,912 discloses a bone screw comprising two or more parts and a coil spring damping means for generating compression at a fracture site. However, in this bone screw, the anterior and posterior threaded portions do not rotate relative to each other, thereby limiting the ability to adjust the amount of compression produced by the bone screw.

[0008] Therefore, a bone screw is needed that at least solves the above-mentioned shortcomings. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] U.S. Patent No. 4,959,064 [Patent Document 2] U.S. Patent No. 6,656,184 [Patent Document 3] U.S. Patent No. 7,582,107 [Patent Document 4] U.S. Patent No. 7,794,483 [Patent Document 5] U.S. Patent No. 5,743,912 [Overview of the project]

[0010] This disclosure provides a novel, innovative bone screw having an elastic component (e.g., a spring) and independently rotatable anterior and posterior portions, which allows a surgeon to measure and adjust the amount of compression caused by the bone screw's effect during installation and to dynamically maintain that compression across the bone screw during fracture healing.

[0011] In a first aspect of the disclosure of this application, which may be combined with any other aspect unless otherwise specified, in light of the technical features described herein, the bone screw comprises a front part, a rear part, and an elastic part. The front part includes a first external threaded region and a second external threaded region. The rear part includes a third external threaded region. The elastic part is positioned around a portion of the front part and inside the rear part. The first end of the elastic part is attached to either the front part or the rear part, and the other of the front part and the rear part is configured to prevent axial movement of the second end of the elastic part relative to the other of the front part and the rear part in at least one direction.

[0012] In a second aspect of the disclosure of this application, which can be combined with any other aspect (e.g., the first aspect) unless otherwise specified, the first end of the elastic component is attached to the rear component, and the front component includes a ridge that contacts the second end of the elastic component, thereby preventing axial movement of the second end relative to the front component in the direction of the ridge.

[0013] In a third aspect of the disclosure of this application, which can be combined with any other aspect (e.g., the first or second aspect) unless otherwise specified, the first and second external thread regions have a non-constant pitch.

[0014] In a fourth aspect of the disclosure of this application, which can be combined with any other aspect (e.g., the first to third aspects) unless otherwise specified, the front part further includes an outer smooth region, the portion of the front part on which the elastic part is arranged around it is the outer smooth region.

[0015] In a fifth aspect of the disclosure of this application, which can be combined with any other aspect (for example, the first to fourth aspects) unless otherwise specified, the elastic member is a spring.

[0016] In a sixth aspect of the disclosure of this application, which can be combined with any other aspect (e.g., the first to fifth aspects) unless otherwise specified, the third external thread region extends along the entire length of the main body portion of the rear component.

[0017] In a seventh aspect of the disclosure of this application, which can be combined with any other aspect (e.g., the first to sixth aspects) unless otherwise specified, the bone screw is configured such that the front and rear parts rotate independently of each other.

[0018] In an eighth aspect of the disclosure of this application, which can be combined with any other aspect (e.g., aspects 1 to 7) unless otherwise specified, the bone screw is configured such that the elastic component rotates when the rear component rotates, but the elastic component does not rotate when the front component rotates.

[0019] In a ninth aspect of the disclosure of this application, which can be combined with any other aspect (e.g., the first to eighth aspects) unless otherwise specified, the front part comprises a first driver function and the rear part comprises a second driver function, the first driver function being different from the second driver function.

[0020] In a tenth aspect of the disclosure of this application, which can be combined with any other aspect (e.g., aspects 1 through 9) unless otherwise specified, the bone screw is configured to compress the bone across the fracture once it has been inserted into the bone across the fracture.

[0021] In a 11th aspect of the disclosure of the present application that can be combined with any other optional aspect (for example, aspects 1 to 10) unless otherwise specified, the bone screw is configured such that when the bone screw is attached to the bone, the elastic component is compressed by advancing the front component into the bone while keeping the position of the rear component constant.

[0022] In a 12th aspect of the disclosure of the present application that can be combined with any other optional aspect (for example, aspects 1 to 11) unless otherwise specified, the system for compressing the fracture site includes a bone screw, a first screwing component, and a second screwing component. The bone screw includes a front component, a rear component, and an elastic component. The front component includes a first outer screw region, a second outer screw region, and a first driver function. The rear component includes a third outer screw region and a second driver function. The elastic component is disposed around a part of the front component and inside the rear component. The first end of the elastic component is attached to the front component or the rear component, and the other of the front component and the rear component is configured to prevent the axial movement of the second end of the elastic component in at least one direction with respect to the other of the front component and the rear component. The first screwing component is configured to engage with the first driver function of the front component and the second driver function of the rear component. The second screwing component is configured to engage with only the first driver function of the front component or only the second driver function of the rear component.

[0023] In a 13th aspect of the disclosure of the present application that can be combined with any other optional aspect (for example, aspect 12) unless otherwise specified, the system further includes a measurement tool configured to measure the displacement between the front component and the rear component of the bone screw.

[0024] In a 14th aspect of the disclosure of the present application that can be combined with any other optional aspect (for example, the 13th aspect) unless otherwise specified, the measurement tool includes a shaft having a window and a rod disposed within the shaft. The rod includes an indicator and is configured to be slidable within the shaft. The indicator can be seen through the window of the shaft.

[0025] In a 15th aspect of the disclosure of the present application that can be combined with any other optional aspect (for example, the 13th or 14th aspect) unless otherwise specified, the front end of the shaft of the measurement tool is configured to receive the first driver function of the front component.

[0026] In a 16th aspect of the disclosure of the present application that can be combined with any other optional aspect (for example, the 14th or 15th aspect) unless otherwise specified, the measurement tool disposes the front end of the shaft around the first driver function, and in that the rod is in the initial position, the first driver function is configured to slide the rod within the shaft.

[0027] In a 17th aspect of the disclosure of the present application that can be combined with any other optional aspect (for example, the 13th to 16th aspects) unless otherwise specified, the measurement tool is integrated with one or both of the first threaded component and the second threaded component.

[0028] In an 18th aspect of the disclosure of this application, which can be combined with any other aspect (e.g., aspects 1 to 17) unless otherwise specified, a method for compressing a fracture includes the step of drilling a bone hole to receive a bone screw. The bone screw comprises an anterior part, a posterior part, and an elastic part. The anterior part includes a first external threaded area, a second external threaded area, and a first driver function. The posterior part includes a third external threaded area and a second driver function. The elastic part is positioned around a portion of the anterior part and inside the posterior part. The first end of the elastic part is attached to either the anterior or posterior part, and the anterior and posterior parts are configured to prevent axial movement of the second end of the elastic part relative to the anterior and posterior parts in at least one direction. The bone screw may be inserted into the drilled bone hole via a first threaded part configured to engage with both the first driver function of the anterior part and the second driver function of the posterior part. The compressive force due to the effect of the inserted bone screw can be measured. The compressive force due to the effect of the inserted bone screw can be adjusted via a second screw-in component configured to engage only with the first driver function of the anterior component or only with the second driver function of the posterior component.

[0029] In a 19th aspect of the disclosure of this application, which can be combined with any other aspect (e.g., the 18th aspect) unless otherwise specified, the step of adjusting the compressive force due to the effect of the bone screw includes advancing or retracting the anterior or posterior part within the bone hole via a second threaded component.

[0030] In a 20th aspect of the disclosure of this application, which can be combined with any other aspect (e.g., aspect 18 or 19) unless otherwise specified, the bone screw is inserted into the bone hole above the guide wire.

[0031] Additional features and advantages of the disclosed methods and apparatus will be described in the following detailed description and figures and will be apparent therefrom. The features and advantages described herein are not exhaustive, and many additional features and advantages will be apparent to those skilled in the art in consideration of the figures and description. Furthermore, it should be noted that the language used herein has been chosen primarily for readability and explanatory purposes and does not limit the scope of the subject matter of the invention. [Brief explanation of the drawing]

[0032] [Figure 1A] This is an exploded view of a bone screw according to one aspect of the present disclosure.

[0033] [Figure 1B] This is a partially exploded view of the bone screw shown in Figure 1A, according to one aspect of the present disclosure.

[0034] [Figure 1C] Figures 1A and 1B show perspective views of a bone screw according to one aspect of this disclosure.

[0035] [Figure 2A] This is a cross-sectional view of the bone screw shown in Figure 1C, according to one aspect of the present disclosure.

[0036] [Figure 2B] Figure 2A is a cross-sectional view of a bone screw according to one aspect of the present disclosure, in which the spring component is partially compressed.

[0037] [Figure 3] This is a perspective view of a driver component for a rear-threaded component according to one aspect of the present disclosure.

[0038] [Figure 4] This is a perspective view of a driver component for a front screw component according to one aspect of the present disclosure.

[0039] [Figure 5A] This is a perspective view of a compression measurement tool according to one aspect of the present disclosure.

[0040] [Figure 5B] Figure 5A shows an enlarged cross-sectional view of the measurement window of the compression measurement tool according to one aspect of this disclosure.

[0041] [Figure 6] A flowchart illustrating an exemplary method for compressing a fracture site according to one aspect of this disclosure is shown. [Modes for carrying out the invention]

[0042] This disclosure provides a bone screw having a spring component that allows a surgeon to measure the amount of compression due to the effect of the bone screw during installation and to dynamically maintain that compression across the bone screw during fracture healing. The bone screw provided comprises an anterior component, a posterior component, and a spring component that can be compressed between the anterior and posterior components. The anterior and posterior components are respectively configured to provide compression between two bone structures when installed in the bone. For example, the anterior component may include two separate external threaded regions having threads of a non-constant pitch, and / or the posterior component may include a tapered body having an external thread of a constant pitch.

[0043] The spring component may be positioned around the non-threaded area of ​​the anterior component and inside the posterior component. The spring component may be attached to one of the anterior or posterior components and merely in contact with the surface of the other. This configuration allows the anterior and posterior components to rotate relative to each other without twisting the spring component. When the provided bone screw is attached to the bone and the anterior or posterior component is advanced or retracted within the bone, the relative displacement between the anterior and posterior components is changed. This change in relative displacement between the anterior and posterior components results in an increase or decrease in the compression of the spring component. Thus, the compressive force due to the effect of the provided bone screw can be adjusted by advancing or retracting either the anterior or posterior component within the bone. The adjustable compressive force allows the surgeon to set the desired compressive force across the fracture site.

[0044] The active spring component further generates dynamic compression, which helps to maintain the desired compressive force across the fracture site during healing. For example, the flexibility of the spring component helps to prevent or reduce the occurrence of the screw coming loose, coming out, or breaking, which can occur with at least some common bone screws when stress is applied to the fracture site. The advantage of the bone screw of this disclosure is that the effect of the active spring component is exerted while maintaining the axial stiffness of the bone screw, as the spring component is positioned around the anterior component. By maintaining axial stiffness, the bone screw provided helps to withstand a greater load when attached to bone compared to at least some common bone screws with a spring component.

[0045] To adjust the compression exerted by the provided bone screw, the bone screw may be used with a threaded component specifically adapted to the provided bone screw. For example, a first threaded component may be adapted to engage simultaneously with both the driver function of the anterior component and the driver function of the posterior component, so that both the anterior and posterior components can be rotated together to advance or retract into the bone. This first threaded component may be used to initially insert the bone screw and, if necessary, to adjust the bone screw as a whole. A second threaded component may be adapted to engage only with the driver function of the anterior component or only with the driver function of the posterior component, so that only one component rotates except the other. This second threaded component may be used to allow a change in the relative displacement between the anterior and posterior components within the bone and thus adjust the compressive force due to the effect of the bone screw. In some cases, in addition to the second threaded component, a third threaded component may be adapted to engage with the driver function of either the anterior component or the posterior component.

[0046] This disclosure further provides a measuring tool which can be used to measure the amount of compressive force due to the effect of an attached bone screw. The provided measuring tool measures the displacement between the anterior and posterior parts. This displacement can be converted into a compressive force based on the spring constant of the spring part. By combining the provided bone screw, threading part, and measuring tool, a surgeon can set a desired compressive force across the fracture site to promote healing. Further advantages of the provided bone screw, threading part, and / or measuring tool will become apparent from the description of the drawings below.

[0047] This specification refers to surgeons. It should be understood that surgeons may be any appropriate medical professional or other user of the bone screws and systems provided.

[0048] Figures 1A to 1C show an exemplary bone screw 100. In at least some embodiments, the bone screw 100 comprises an anterior component 102, a spring component 104, and a posterior component 106. The components of the bone screw 100 may be adapted to provide compression across the fracture site when the bone screw 100 is attached to the bone across the fracture site. Figure 1A is an exploded view of the bone screw 100, showing the anterior component 102, the spring component 104, and the posterior component 106 individually. In at least some embodiments, the anterior component 102 comprises a shaft having a cutting tip 108 at its distal end. In various examples, the cutting tip 108 may be self-perforating. In at least some embodiments, the shaft of the anterior component 102 may be cannular, as indicated by the channel 134 in the illustrated embodiment.

[0049] In at least some embodiments, the shaft of the anterior component 102 includes an external thread that contributes to applying compression between two bone fragments. For example, the anterior component 102 may include an external thread region 110. In some cases, the anterior component 102 may include an external thread region 112. In various cases, the threads in the external thread region 110 and / or external thread region 112 may have a non-constant pitch. In one example, the pitch of the external thread of the anterior component 102 may be greatest near the distal end of the anterior component 102 (e.g., cutting tip 108) and decrease as it moves away from the distal end through the external thread region 110 and external thread region 112. The pitch of the external thread is measured between corresponding locations of a series of thread vertices. In another example, the vertex radius of the external thread of the anterior component 102 may be greatest near the distal end of the anterior component 102. For example, the threads in the external thread region 110 may have a larger vertex radius than the threads in the external thread region 112. The apex radius of the external thread is measured from the central axis of the front part 102 to the outermost point of the external thread.

[0050] In at least some embodiments, the front part 102 may include a non-threaded region 114. For example, the non-threaded region 114 may have a smooth outer surface. In various cases, the non-threaded region 114 terminates with a ridge 116, which extends outward from the outer surface of the shaft of the front part 102. In at least some embodiments, the shaft of the front part is provided with a driver function 118 at its proximal end. The driver function 118 may have any suitable configuration that allows it to be engaged by a component of a screw-in device. In the illustrated example, the driver function 118 has a hexagonal outer circumference.

[0051] The spring component 104 has a front end 120 opposite to its rear end 124. Between the front end 120 and the rear end 124, the spring component 104 includes an elastic portion 122. In some embodiments, such as the illustrated embodiment, the elastic portion 122 may be a machined spring. In other embodiments, the elastic portion 122 may be a coil spring or other suitable resilient member. As shown in Figure 1B, the spring component 104 may be located around the front component 102, such as around the non-threaded region 114. As shown in Figure 1C, the spring component 104 may be located inside the rear component 106. As will be explained in more detail below, the characteristic of the elastic portion 122 is the spring constant, which is a coefficient of the amount of compressive force due to the effect of the bone thread 100.

[0052] The posterior component 106 comprises a body having a proximal end 126 opposite to its distal end 130. The posterior component 106 is configured to help contribute to applying compression between two bone fragments. For example, the body of the posterior component 106 may be tapered so that the body has a larger diameter at its distal end 130 compared to its proximal end 126. The body of the posterior component 106 may be equipped with an external thread 128 having a constant pitch. In at least some embodiments, the posterior component 106 includes a driver function 132 that begins at its distal end 130. The driver function 132 may have any suitable configuration (e.g., a modified hexalobular) that allows it to be engaged by a component of a screw-in device.

[0053] In the configuration of the bone screw 100 shown in Figure 1C, the front part 102 and the rear part 106 rotate independently of each other. In at least some embodiments, the spring part 104 can be attached to either the front part 102 or the rear part 106. For example, as best illustrated in the embodiment shown in Figure 1B, the rear end 124 of the spring part 104 is in contact with the ridge 116 of the front part 102, but is not attached to it. On the other hand, the front end 120 of the spring part 104 is attached to the rear part 106. For example, the front end 120 of the spring part 104 may be attached to the rear part 106 by welding or mechanical fitting. In this exemplary embodiment, once the bone screw 100 is attached to the bone, the spring part 102 rotates in conjunction with the rear part 106 because they are attached to each other. The spring part 102 can rotate freely around the front part 102. Conversely, rotating the front part 102 does not cause the spring part 102 to rotate. In addition, the ridge 116 prevents the mounted pair of rear part 106 and spring part 104 from sliding out of the front part 102.

[0054] In other embodiments, the rear end 124 of the spring component 104 may be attached to the front component 102 so as to be attached to the ridge 116. In such other embodiments, the rear component 106 may have an internal ridge (similar to the ridge 116 in the illustrated embodiment) that contacts but is not attached to the front end 120 of the spring component 104. In addition, in such other embodiments, the internal ridge prevents the rear component 106 from sliding out of the attached pair of the front component 102 and the spring component 104.

[0055] The above-described configuration of the bone screw 100 allows for adjustment of the amount of compressive force due to the effect of the bone screw 100 by making the relative displacement between the anterior part 102 and the posterior part 104 adjustable. For example, once the bone screw 100 is attached to the bone, the anterior part 102 may be advanced or retracted within the bone, while the posterior part 106 remains stationary, and vice versa. Figure 2A is a cross-sectional view of the fully configured bone screw 100 shown in Figure 1C. In one example, the anterior part 102 may be advanced in the direction of arrow 204 (e.g., via a screw-in device that engages with the driver connector 118). When the anterior part 102 is advanced, it compresses the spring part 104, and an exemplary result is shown in Figure 2B. The amount of compression of the spring part 104 and its spring constant are coefficients of the amount of compressive force due to the effect of the bone screw 100 across the fracture site.

[0056] The spring component 104 further generates dynamic compression across the fracture site, which helps to maintain the desired compressive force across the fracture site during healing. For example, if a conventional compression screw without a spring component is installed across a fracture site and stress is applied to the fracture site (e.g., a force trying to move the two bone fragments toward each other), the conventional compression screw has little to no elasticity, so stress may concentrate at the connection between the threaded portion of the conventional compression screw and the bone. Repeated stress on the fracture site may cause this conventional compression screw to come loose, fall out, or break. The advantage of the bone screw 100 is that the spring component 104 provides some elasticity that removes some of the stress from the connection between the threaded portion and the bone, concentrating the stress within the spring component 104. This helps to reduce the occurrence of the screw coming loose, falling out, or breaking, which can occur with conventional compression screws without a spring component. At the same time, the bone screw 100 maintains its axial rigidity and strength despite having a spring component, unlike at least some common compression screws that have a spring component, by positioning a spring component 104 around the front component 102. The axial rigidity and strength of the bone screw 100 helps it withstand greater loads than at least some common compression screws that have a spring component.

[0057] In some embodiments, the bone screw 100 may be configured for use in the elbow, carpal, foot, or ankle to apply dynamic compression to the fracture site, healing, and osteotomy. Because the elbow, carpal, foot, or ankle contains bone structures with lower bone density, they can benefit from a screw with some elasticity, such as the elasticity provided by the spring component 104 of the bone screw 100. In other embodiments, the bone screw 100 may be configured for use in the buttocks or shoulder. Because the bone structures of the buttocks and shoulders are larger than those of the elbow, carpal, foot, or ankle, the bone screw 100 configured for the buttocks or shoulder may be larger (e.g., have a larger spring component 104) and have a greater range of motion than the bone screw 100 configured for the elbow, carpal, foot, or ankle. In yet another embodiment, the bone screw 100 may be configured for other suitable bone structures in the patient.

[0058] In various embodiments, the bone screw 100 may be made of a suitable biocompatible material such as titanium, stainless steel, or nitinol. In some examples, the anterior component 102, the spring component 104, and the posterior component 106 may each be made of the same suitable material. In other examples, at least one of the anterior component 102, the spring component 104, or the posterior component 106 may be made of a different suitable material than the others.

[0059] As described above, the anterior part 102 or the posterior part 106 of the bone screw 100 may be advanced or retracted within the bone independently of the other. To do so, a threaded component fitted to the anterior part 102 and the posterior part 104 of the bone screw 100 may be provided. Figure 3 is a perspective view of an exemplary threaded component 300. The threaded component 300 comprises a shaft 302. It should be understood that the shaft 302 may be of any suitable length and may not be drawn to scale. In some embodiments, the posterior end 306 of the shaft 302 of the threaded component 300 may be fitted to connect to a driver or handle (for example, for manual screwing). For example, the posterior end 306 may be an AO connector as shown. In other embodiments, the posterior end 306 of the shaft 302 may be integrally connected to a driver or handle. The threaded component 300 may be made of a suitable biocompatible material.

[0060] In an exemplary example, the threaded component 300 is configured to engage simultaneously with both the driver connector 118 of the anterior component 102 and the driver connector 132 of the posterior component 106. For example, the threaded component 304 is configured to engage with the driver connector 132 of the posterior component 106, and the threaded component 308 is configured to engage with the driver connector 118 of the anterior component 102. The threaded component 300 may be positioned around the driver connector 118 and inside the driver connector 132. By simultaneously engaging with both the driver connector 118 of the anterior component 102 and the driver connector 132 of the posterior component 106, the surgeon can advance the bone screw 100 as a whole into the bone via the threaded component 300. For example, this may be done when the bone screw 100 is first inserted.

[0061] Figure 4 is a perspective view of an exemplary screw-in component 400. The screw-in component 400 comprises a shaft 402. It should be understood that the shaft 402 may be of any suitable length and may not be drawn to scale. In some embodiments, the rear end 406 of the shaft 402 of the screw-in component 400 may be adapted to connect to a screwdriver or handle (for example, for manual screwing). For example, the rear end 406 may be an AO connector as shown. In other embodiments, the rear end 406 of the shaft 402 may be integrally connected to the screwdriver or handle. The screw-in component 400 may be made of a suitable biocompatible material.

[0062] In an exemplary example, the threaded component 400 is configured to engage only with the driver connector 118 of the anterior component 102. For example, the threaded connector 408 is configured to engage with and correspond to the driver connector 118 of the anterior component 102. The threaded component 400 may be located around the driver connector 118 and inside the driver connector 132. However, the connector 404 does not correspond to the driver connector 132 of the posterior component 106 and therefore does not engage with the driver connector 132. In some embodiments, the connector 404 may be smooth as shown. By engaging only with the driver connector 118 of the anterior component 102, the surgeon can advance or retract only the anterior component 102 via the threaded component 400. For example, the surgeon can advance or retract only the anterior component 102 to adjust the compressive force due to the effect of the bone screw 100.

[0063] In some aspects of this disclosure, although not shown, screw-in components are provided that are configured to engage only with the driver connector 132 of the rear component 106. For example, in some cases, the connector 404 of the screw-in component 400 may be configured to engage with and correspond to the driver connector 132 of the rear component 106, while the screw-in connector 408 may be configured not to engage with the driver connector 118 of the front component 102 by not corresponding to it. By engaging only with the driver connector 132 of the rear component 106, the surgeon can advance or retract only the rear component 106. For example, the surgeon can advance or retract only the rear component 106 to adjust the compressive force due to the effect of the bone screw 100.

[0064] In at least some cases, it is useful for surgeons to know how much compressive force is applied across a fracture site by a bone screw (e.g., bone screw 100). For example, this information may allow a surgeon to adjust the anterior part 102 or posterior part 106 of the bone screw 100 to achieve a desired amount of compressive force across the fracture site. Figure 5A shows an exemplary measuring tool 500 for measuring the compressive force due to the effect of a bone screw (e.g., bone screw 100) across a fracture site. The measuring tool 500 comprises a shaft 502. The posterior end 516 of the shaft 502 may form any suitable end of the measuring tool 500, such as a handle.

[0065] In various embodiments, the rod 510 is positioned within the shaft 502. In such embodiments, the rod 510 can slide within the shaft 502. In some examples, the rod 510 may be cannular in shape, including a channel 518 (Figure 5B). The front end of the shaft 502 includes a connector 504 and a connector 506. In at least some embodiments, the connector 506 is configured to correspond to a driver connector 118 and / or the connector 504 is configured to correspond to a driver connector 132. This configuration of the connectors 504 and / or 506 helps to keep the measuring tool 500 axially aligned with the bone screw 100 in order to achieve accurate measurements. In the initial position, before the measurement is performed, the rod 510 may be positioned toward the front end of the shaft 502. For example, one end of the rod 510 may be aligned with the front end of the shaft 510.

[0066] To perform the measurement, the measuring tool 500 may be positioned around the front part 102 of the bone screw 100 (e.g., driver connector 118) and inside the rear part 106 (e.g., driver connector 132), so that the driver connector 118 is inside the connector 506 of the measuring tool 500. In at least some embodiments, the measuring tool 500 may be advanced into the rear part 106 as far as the measuring tool 500 can advance. When this is done, the driver connector 118 of the rear part 106 causes the rod 510 to slide within the shaft 502 of the measuring tool 500. In at least some embodiments, the rod 510 is provided with an indicator 512, such as a line marking. In various embodiments, the shaft 502 may be provided with a window 508 through which the indicator 512 of the rod 510 can be seen. In at least some examples, the shaft 502 is provided with a scale 514 adjacent to the window 508. The measured value corresponds to the point where the indicator 512 aligns with the scale 514. In some embodiments, the measuring tool 500 measures the displacement between the front part 102 and the rear part 106 of the bone screw 100. This displacement can be converted into a quantity of compressive force based on the spring constant of the spring part 104. In some embodiments, the scale 514 may include the displacement value (e.g., millimeters). In other embodiments, the scale 514 may include the value of the compressive force (e.g., Newtons).

[0067] In some aspects of this disclosure, the measuring tool 500 may be a separate component itself. In such aspects, the surgeon may use the measuring tool 500 to perform measurements as needed and separate threaded components (e.g., threaded components 300 and 400) to install or adjust the bone screw 100. In other aspects of this disclosure, the measuring tool 500 may be integrated with the threaded components. For example, in such aspects, the measuring tool 500 may be composed of one or more materials suitable for acting as a threaded component. In addition, in such other aspects, the surgeon may install or adjust the bone screw 100 and perform measurements with the same tool.

[0068] Figure 6 shows a flowchart of an exemplary method for compressing a fracture site according to one aspect of the present disclosure. While exemplary method 600 is described with reference to the flowchart shown in Figure 6, it will be understood that many other methods may be used to perform the actions related to method 600. For example, some order of blocks may be changed, certain blocks may be combined with others, and some of the described blocks are optional.

[0069] In some cases, method 600 may begin by drilling a bony hole to receive a bone screw (e.g., bone screw 100) (block 602). In some embodiments, the step of drilling a bony hole includes inserting a guidewire at the intended location for the bone screw 100. A first drill or drilling component may be used to create a hole in the bone (e.g., proximal cortex) having a contour similar to that of the posterior portion of the bone screw 100 (e.g., posterior component 106). A second drill or drilling component may be used to create a hole in the bone having a contour similar to that of the anterior portion of the bone screw 100 (e.g., anterior component 102). In at least some embodiments, once the bony hole has been drilled to receive the bone screw 100, the desired length and / or diameter of the bone screw 100 is determined using radiographic and / or measuring instruments. The surgeon can then select a bone screw 100 having the determined length and / or diameter.

[0070] In at least some embodiments, the surgeon may insert the selected bone screw 100 into the open bone hole via a first threaded component (e.g., threaded component 300) (block 604). The threaded component 300 engages simultaneously with both the anterior component 102 (e.g., driver connector 118) and the posterior component 106 (e.g., driver connector 132) so that the surgeon can advance the bone screw 100 as a whole into the bone hole. The surgeon can advance the bone screw 100 to the desired position across the fracture site between the two bone fragments.

[0071] In various cases, the surgeon may then measure the compressive force due to the effect of the inserted bone screw 100 (block 606). For example, the surgeon may use a measuring tool 500 to measure the compressive force due to the effect of the inserted bone screw 100. In some cases, the compressive force due to the effect of the inserted bone screw 100 may be adjusted via a second threaded component (e.g., threaded component 400) (block 608). For example, the measured compressive force may not be equal to the compressive force desired by the surgeon to treat a particular fracture site. In this example, the threaded component 400 engages only with the anterior component 102 (e.g., driver connector 118) so that the surgeon can advance or retract only the anterior component 102. By doing so, the relative displacement between the anterior component 102 and the posterior component 106 in the bone is changed, thereby adjusting the compressive force due to the effect of the bone screw 100 across the fracture site. In other examples, to adjust the compressive force in a similar manner, a screw-in component that engages only with the rear component 106 (e.g., the driver connector 132) may be used, as described above.

[0072] In some cases, after adjusting the compressive force, the surgeon may measure the compressive force due to the effect of the bone screw 100 again. If the measured compressive force is not the compressive force desired by the surgeon, the surgeon may then adjust the compressive force again via a screw-in component that engages only with the anterior component 102 or only with the posterior component 106. As described above, in some embodiments, the surgeon may use the same tool or screw-in component to adjust or measure the compressive force. Once the surgeon is satisfied with the compressive force due to the effect of the bone screw 100 across the fracture site, the bone screw 100 is set and the fracture site is able to heal.

[0073] The examples and embodiments disclosed herein should be construed as illustrative only and not in any way limit the scope of this disclosure. It will be apparent to those skilled in the art that modifications can be made to the details of the above examples without departing from the basic principles described. In other words, various modifications and improvements to the examples specifically disclosed above are within the scope of the appended claims. For example, any suitable combination of features of the various examples described is contemplated.

Claims

1. an anterior component including a first externally threaded region and a second externally threaded region; a posterior component including a third externally threaded region; an elastic part disposed between the periphery of a portion of the front part and the interior of the rear part; A bone screw comprising: a first end of the resilient component is attached to one of the anterior and posterior components for rotation as a pair with the anterior or posterior component, the resilient component being free to rotate about the other of the anterior and posterior components, the other of the anterior and posterior components being configured to prevent axial movement of the second end of the resilient component relative to the other of the anterior and posterior components.

2. 2. The bone screw of claim 1, wherein said first end of said resilient component is attached to said posterior component, said anterior component including a ridge in contact with said second end of said resilient component, said ridge preventing axial movement of said second end relative to said anterior component.

3. The bone screw of claim 1 , wherein said first external thread region and said second external thread region have a non-constant pitch.

4. 10. The bone screw of claim 1, wherein said anterior component further comprises an outer smooth region, said outer smooth region being the portion of said anterior component around which said resilient component is disposed.

5. The bone screw of claim 1 , wherein said resilient element is a spring.

6. The bone screw of claim 1 , wherein said third externally threaded region extends the entire length of said posterior component body portion.

7. 10. The bone screw of claim 1, wherein the bone screw is configured such that the anterior and posterior components rotate independently of each other.

8. 10. The bone screw of claim 1, wherein the bone screw is configured such that when the posterior component rotates, the resilient component rotates, but when the anterior component rotates, the resilient component does not rotate.

9. 10. The bone screw of claim 1, wherein said anterior component includes a first driver mechanism and said posterior component includes a second driver mechanism, said first driver mechanism being different from said second driver mechanism.

10. 10. The bone screw of claim 1, wherein the bone screw is configured to apply compression across a fracture when inserted into bone across the fracture.

11. 10. The bone screw of claim 1, wherein the bone screw is configured to compress the resilient component when the bone screw is installed in a bone by advancing the anterior component into the bone while holding the posterior component in a constant position.

12. 1. A system for compressing a fracture, comprising: a forward component including a first externally threaded region, a second externally threaded region, and a first driver mechanism; a rear component including a third externally threaded region and a second driver mechanism; an elastic element disposed between the periphery of a portion of the front component and the interior of the rear component, wherein a first end of the elastic element is attached to one of the front component and the rear component so as to rotate as a pair with the front component or the rear component, the elastic element being free to rotate around the other of the front component and the rear component, and the other of the front component or the rear component being configured to prevent axial movement of a second end of the elastic element relative to the other of the front component or the rear component; a bone screw comprising: a first threaded component configured to engage the first driver mechanism of the front component and to further engage the second driver mechanism of the rear component; a second threaded component configured to engage only the first driver mechanism of the anterior component or to engage only the second driver mechanism of the posterior component.

13. 13. The system of claim 12, further comprising a measurement tool configured to measure displacement caused between the anterior and posterior components of the bone screw.

14. the measurement tool: a shaft including a window; a rod disposed within the shaft and configured to be slidable within the shaft; Equipped with The system of claim 13 , wherein the rod includes an indicator, the indicator being visible through the window in the shaft.

15. The system of claim 14 , wherein a front end of the shaft of the measurement tool is configured to receive the first driver mechanism of the front piece.

16. 16. The system of claim 15, wherein the measurement tool is configured such that the first driver mechanism slides the rod within the shaft by positioning the front end of the shaft around the first driver mechanism while the rod is in an initial position.

17. The system of claim 13 , wherein the measurement tool is integral with one or both of the first threaded part and the second threaded part.

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