Radiolucent fixation systems

Abstract

A radiolucent fixation system is provided for orthopedic and translational applications, comprising implantable thermoplastic plates, rods, and fasteners for stabilizing fractures or bone defects while enabling clear diagnostic imaging. The fasteners include a rigid central component and deformable malleable grip segments that are selectively welded or staked using an energy-producing handheld device. In some embodiments, blind-end rivet mechanisms are used to secure fixation where access to the distal cortex is limited. The radiolucent materials reduce imaging artifacts, enable repeated longitudinal studies in preclinical research, and avoid complications associated with metal implants such as stress shielding and imaging interference. Methods for device implantation, imaging, and fabrication using additive and subtractive manufacturing are also described.

Description

RADIOLUCENT FIXATION SYSTEMSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 667,895, filed on July 5, 2024, and titled “Radiolucent Fixation Systems,” the entirety of which is hereby incorporated by reference.FIELD

[0002] The present disclosure relates to orthopedic applications and joining methods suitable for use in human and animal tissues, specifically radiolucent fixation systems (RFS).BACKGROUND

[0003] Radiolucency is a property of material that provides a measure (partial or whole) of the permeability of radiant energy, such as x-rays.

[0004] Osteosynthesis is a surgical procedure that mechanically stabilizes the ends of fractured bones or bone defects, for example by using mechanical devices such as metal plates, pins, rods, wires, screws, or other fasteners. The field of osteosynthesis was pioneered in 1800's when the first internal fixation procedure was performed by reducing an olecranon fracture with two transcutaneous screws. Later that century, the first internal plate osteosynthesis fixation procedure was performed using a removable steel plate and nickel-plated screws. Since then, osteosynthesis fixation with metal plates and screws has remained the gold-standard treatment option for most fractures and bone defects where the use of osteosynthesis devices is a selected treatment option.

[0005] While the use of metal in osteosynthesis devices offers rigidity and mechanical strength, metal is radiopaque (and as such limits x-ray penetration (permeability)). This radiopacity impairs the precision and sharpness of structures that can be identified when radiation-based diagnostic imaging is used by introducing a radiation beam source reflection and filtering (which are several known artifacts (i.e., something seen on an image that is not present in reality but appears due to a quirk of the modality itself, such as x-ray scatter or beam hardening)). Furthermore, the radiopacity confounds the acquisition of radiodensity metrics from an image of bone fractures or defect sites where radiopaque elements are present.

[0006] There are clinical and non-clinical applications where these impediments produce significant challenges and thus a need remains for improved systems, methods and devices.

[0007] In clinical patients whose bones require hardware fixation due to sustained fractures or large segmental defects, it is important to track bone healing and regeneration over time. Evenwithout the interference of metal components, which generate radiation reflection and refraction artifacts when exposed to radiation sources, the detailed visualization needed to allow for accurate assessment / evaluation to the extent and quality of any bone regeneration can be difficult to achieve. The small incremental changes in the dimensions and properties of healing bone over time can be difficult to detect and as such, can often be described as subtle. Nonetheless, adequate imaging of a fracture or defect site is needed to allow surgeons to visualize the condition and position of healing bone and implant components which are the object of attention and to allow evaluating the healing condition of the bone for the removal of metal devices in the imaged fracture or defect site. If metal devices are removed (taken off) too early, there is the potential for re-fracturing of the partially healed bone. If they are removed (taken off) too late, the unwanted risk of bone stress shielding effects (a biomechanical phenomenon causing adaptive changes in bone strength and stiffness around metallic implants, which potentially lead to weakened bone, implant loosening, and increased risk of new fractures secondary to bone weakening) comes into play. Stress shielding occurs when the bone growth and structure naturally adapts and weakens as the bone's growth, density, and material properties adapt to it being a body component carrying lower stresses as it relies on the long-term strength of the adjacent prosthetic plate, rather than the strength of the nascent bone. In such cases, the bone adj acent and near to nascent and remodeling bone can become osteopenic as it is not required to carry or transmit forces (and the related stresses and strains related thereto) of normal activities as it relies substantially on metal hardware.

[0008] Another example for clinical application involves human or veterinary patients with primary bone cancer or cancer that has metastasized to bone. In these patients, tumor resection is frequently required, followed by stabilization and reconstruction of the bone defect site created by the resection with osteosynthesis hardware. Often, the cancer itself has caused pathologic bone fractures, which are also stabilized with osteosynthesis hardware. In such cases, radiotherapy and long-term monitoring of the treated site are routinely performed. Metal hardware impedes the delivery of radiotherapy and limits the value of non-invasive imaging of the tumor resection site, and adjacent sites, as the images derived from radio waves-based imaging sources do not provide a visual image from which diagnostic and treatment conclusions can be made, thereby limiting the detail and accuracy of oncologic treatment, monitoring, and enhancing the unwanted potential for tumor recurrence.

[0009] For non-clinical applications, translational or preclinical research refers to investigation conducted for the purposes of transforming basic science discoveries into products that directly benefit human beings. In translational research bone regeneration studies, fractures, segmental defects, and non-unions (defective healing: nonunion describes the failure of a fractured bone to heal and mend after an extended period of time) observed clinically are replicated utilizingcritical sized defect (CSD) animal models. The CSD is a surgically created uniform gap (defect) in bone that is stabilized with the use of an osteosynthesis device. The gap is of a size that will not normally heal without therapeutic intervention. Novel therapeutics are then implanted into the gap of the CSD site and tested for their efficacy in facilitating, enhancing, or accelerating bone repair and regeneration. In these studies, the CSD site is referred to as the region of interest (ROI).

[0010] Traditionally, preclinical osteosynthesis devices utilized in these models also include metal hardware for two reasons: 1-to withstand the formidable static and dynamic load bearing forces existing over time, and 2-to replicate the clinical scenario. Bone regeneration is regularly monitored in these studies with x-rays, high resolution Micro-Computed Tomography (pCT), or similar imaging modalities. To mitigate the consequential radio imaging artifacts produced by metal interference, animals are sacrificed at the desired time-point of interest for clinical research significance, and the metal hardware is removed prior to ex-vivo imaging. This ensures that newly forming regenerate bone can be clearly visualized within the ROI without metal scatter interference.

[0011] In cases where the metal fixation device cannot be removed due to lack of bone bridging, an alternative to removing the metal screws and other hardware involves attempting to perfectly position the resected bone perpendicular to the axis of the x-ray source, so that the x-rays path to enter the ROI defect site is unimpeded. While this method is widely utilized, it is not ideal, and the effects of the nearby metal creating radio imaging artifacts and beam hardening must be taken into consideration as they can negatively influence the interpretation of the bone densities within a sample ROI. Developing improved devices and systems that resolve some or all of the issues set forth above is desired.

[0012] Longitudinal experiments are routinely performed to monitor bone regeneration and healing over time in translational preclinical research studies. In vivo imaging of subjects with metal hardware is generally avoided due to the impediments in visualization of regenerating bone within the ROI elicited by a combination of metal artifact and physiologic motions of the patient caused by breathing, for example. In these instances, even slight positional changes of the patient within the scanner can lead to wide variabilities in the perceived radiodensity of a forming regenerate within a ROI and therefore does not provide a visual image from which accurate quantitative data can be derived to guide definitive scientific, diagnostic and / or therapeutic conclusions. Traditionally, this type of experimental design requires that separate groups of animals undergo identical experimental steps for each time point in the study.

[0013] Such previously known and available components and techniques are not effective in treating injury and treatment sites in portions of long bone sections, where a hollow medullary cavity predominates the bone architecture. While a vertebral pedicle offers clinically acceptablepurchase and stability to a penetrating fastener used in an osteosynthesis system where the core / shaft / body of the fastener is in continuous contact with the adjacent bone, no such continuous contact is available in long bone sections having hollow medullary cavities. Therefore, existing techniques alone, like some that are described above, are not effective for treatment of defects and / or injuries to long bone sections where use of osteosynthesis systems is considered a treatment option. Accordingly, a need remains for improved systems, methods, and devices to overcome the challenges set forth hereinabove.SUMMARY

[0014] In one aspect, a method for eliminating diagnostic imaging artifacts caused by metal implants for clear visualization of healing or regenerating bone within a patient is disclosed. This can be achieved by using surgically placed osteosynthesis devices comprised of radiolucent thermoplastic materials for the purposes of stabilizing fractures or bone defects. The method includes attaching one or more radiolucent thermoplastic osteosynthesis devices to a bone in a patient for the purposes of stabilizing fractures or bone defects; fabricating radiolucent thermoplastic fixation devices; and imaging and observing clear images without imaging artifacts over time within the same patient without removing metal hardware or relying on patient positioning strategies to limit imaging artifacts caused by metal interference.

[0015] In another aspect, a method is provided for attaching radiolucent thermoplastic osteosynthesis devices to bone in a patient for the purposes of stabilizing fractures or bone defects. The method includes surgically opening a patient and dissecting tissues to reveal an injured bone site where this step is applied to at least one of items a and b below in addition to at least one bone recited in c, d, e, and f, below: a. where the patient is either human, veterinary, or a research animal; b. where the injured bone site is a fracture, non-union, or bone defect; c. where the bone is cortical; d. where the bone is cancellous; e. where the bone is a mixture of cortical and cancellous; and f. where the bone is a cylindrical tube consisting of an outer cortical shell and a central medullary cavity as with the central region (diaphysis) of a long bone.

[0016] The process further includes exposing the areas around the injured bone site where a radiolucent thermoplastic plate is to be placed and temporarily clamping said plate to bone, where the plate has predrilled holes configured to accept radiolucent thermoplastic fasteners. The process continues to the step of inserting a radiolucent thermoplastic rod through the medullary cavity ofan injured bone in cases where additional support is needed due to high physiologic loads. This is accomplished by creating a hole through the outer surface of the bone where the cylindrical body of the created hole aligns with the medullary cavity, and placement of a rod through that hole for internal stabilization of the bone. Pilot holes can be predrilled through the bone and / or rod using the radiolucent thermoplastic plate holes as a guide. The predrilled pilot holes can be trapped traversing the bone and / or rod with customized cutting or molding taps designed with the matching geometry of the intended radiolucent thermoplastic fastener mating threads when present. The process continues by placing the radiolucent thermoplastic fastener into the predrilled pilot hole and securing it to the bone and / or rod: a. where the radiolucent thermoplastic fastener is a screw type requiring a customized driving device to accommodate the superior malleable grip segment; and / or b. where the radiolucent thermoplastic fastener is a blind-end rivet type requiring a specialized riveting instrument for insertion.

[0017] The process can further include the step of deforming the outer malleable grip segments of the radiolucent thermoplastic fasteners to increase contact surface area, create a locking mechanism, and increase the compression forces existing between the plate and the fastener superiorly and the fastener and the bone inferiorly. The deformation can be elicited with the clamping of the specialized riveting instrument in the case of blind-end rivet type radiolucent thermoplastic fasteners. The deformation can be elicited with a heat generating handheld device used after the fastener is secured mechanically through the bone in its final unheated position. The heat generating device can be an ultrasonic welder, soldering iron, bovie device, fluid heated probe, air heated probe or the like. The energy supplying the heat generating device can be ultrasound, microwave, laser, electromagnetic, radiofrequency, plasma energy, or the like.

[0018] In an example, the heat generating device can be an ultrasonic welder, soldering iron, bovie device, fluid heated probe, air heated probe or the like. The energy supplying the heat generating device can be ultrasound, microwave, laser, electromagnetic, radiofrequency, plasma energy, or the like.

[0019] In a further aspect, a method of composition for radiolucent thermoplastic fixation devices is provided. The method includes additively manufacturing each component of the radiolucent fixation device (for example, the plate, rod and fastener) through 3D printing and / or injection molding, for example when the components are all the same material. In another example, each component of the radiolucent fixation device is subtractively manufactured through CNC milling, for example when the components are all the same material. In another example, each component of the radiolucent fixation device is additively manufactured separately through 3D printing and / or injection molding, for example when the components are different materials withdifferent thermal properties (for example the outer malleable grip segments vs. the central component of the screw type fastener). The method can further include assembling the materials so that they are bound to each other via heat staking, overmolding, two-shot injection molding, or combinations thereof, to achieve the final pre installation geometry.

[0020] The present disclosure provides for a method for imaging and observing clear images without imaging artifacts over time within the same patient. This is done without removing metal hardware or relying on patient positioning strategies to limit imaging artifacts caused by metal interference including positioning a patient within an x-ray imager, Computed Tomography (CT) scanner, Micro-Computed Tomography (pCT) scanner, MRI scanner, and / or other radio wave imager. The patient can be a human clinical patient, a veterinary clinical patient, or a research anima. The patient may have a fracture or bone defect stabilized by a radiolucent thermoplastic osteosynthesis device of the present disclosure. The method includes, taking and observing the diagnostic image and or a series of longitudinal diagnostic images over the course of healing of a bone fracture or bone defect stabilized with a radiolucent thermoplastic osteosynthesis device of the present disclosure.

[0021] In yet another aspect, an implantable radiolucent thermoplastic system is provided for stabilizing fractures or bone defects. The system includes: radiolucent thermoplastic material fasteners, radiolucent thermoplastic material plates and rods, specialized instrumentation such as customized taps and drivers engineered for careful insertion of thermoplastic fasteners in osteosynthesis applications, heat generating handheld devices, and specialized attachment arrangements and configurations for the heat generating handheld devices that enable thermoplastic welding and staking within biological tissue, (such that they might significantly increase the strength of the finally assembled osteosynthesis system).

[0022] The present disclosure provides for an implantable radiolucent thermoplastic fastener (screw type). The fastener may include: a central component segment including a screw head combined with a shaft / core / body region, and lateral segments termed superior and inferior malleable grip segments residing adjacent to (on either side of) the central component segment. The central component can be bonded to (integrated with) the lateral malleable grip segments. The fastener(s) are configured for placement through a hole within a bone plate adjacent to bone, and through a predrilled hole through the bone where the lateral malleable grip segment deformations act to provide stability between the plate and the bone superiorly, and between the fastener and the bone inferiorly. An inferior malleable grip segment can be provided with a diameter engineered to be smaller than the outer diameter of the central component shaft / core / body region so as to avoid contact with bone upon insertion through a predrilled pilot hole, thereby eliminating the possibility of shearing the inferior malleable grip segment off of the fastener shaft / core / body segment uponfastener insertion into bone. Lateral malleable grip segments can be provided that are deformable upon contact with an energy producing handheld device where the amount and manner of energy transfer does not produce injury (cause tissue necrosis) to biological tissues such that the deformation results in a change in geometry from a long slender rod like structure to a wide dome shaped structure to increase the surface area of contact and compressional forces between the fastener ends and the materials it is traversing.

[0023] In an example, lateral malleable grip segments are provided that include a recess geometry on their outer surfaces that matches the drive geometry within the tip of the energy producing handheld device. The drive recess can be placed at a distance from the neck region of the fastener so as to eliminate the possibility of drive entry (thereby weakening the fastener) into the neck and / or core / shaft / body regions of the fastener upon deformation of the lateral malleable grip segments. A central component can be provided that is rigid, inflexible, and not deformable by the amount of energy required to safely deform the lateral malleable grip segments. It can include a core / shaft / body with a screw thread pattern, it can be smooth without threads, or it can be formed with a customized patterned geometry. The central component segment can be made from a material that is an inert, biologically compatible, and radiolucent material or combinations of such materials, such as PEEK, PC, PA, or PE, or a combination thereof. In another example, the central component segment is formed of a material mixed with strengthening reinforcing agents such as carbon fiber, glass fiber, hydroxyapatite or beta-tricalcium phosphate for example. In yet a further example, the central component segment is a resorbable, biologically compatible, and radiolucent material or combination of such materials, such as PLA, PDLLA, PLLA, PCL, or glycolide with optional reinforcing agents as listed above. In even a further example, the central component segment can be coated with or fabricated with therapeutics to aid in or accelerate fracture healing or bone regeneration within bone defects.

[0024] In another example, lateral malleable grip segments can be made from a material that is an inert, biologically compatible, and radiolucent material or combination of such materials, such as PEEK, PC, PA, or PE, or combinations thereof. The material can be mixed with strengthening reinforcing agents such as carbon fiber, glass fiber, hydroxyapatite or beta-tricalcium phosphate. The material can further be a resorbable, biologically compatible, and radiolucent material or combination of such materials, such as PLA, PDLLA, PLLA, PCL, or glycolide or mixed with strengthening reinforcing agents as listed above. In a further example, the segments can be coated with or fabricated with therapeutics to aid in or accelerate fracture healing or bone regeneration within bone defects.

[0025] The present disclosure provides for an implantable radiolucent thermoplastic fastener (blind-end rivet type) including: a first mandrel component having a long cylindrical shapehaving a superior shaft region and an inferior widened mandrel head region, a second outer rivet component having a superior rivet head, central rivet body, and inferior rivet tip that defines an opening through which the first mandrel component shaft penetrates. The fastener can be configured for placement through a hole within a bone plate adjacent to the bone, and through a predrilled hole through the bone where the fastener functions via a blind-end rivet mechanism. The mandrel shaft can be pulled through the rivet body with a specialized riveting instrument, causing the mandrel head to penetrate the inferior rivet tip so as to change the resulting diameter of the inferior rivet tip thereby increasing the surface area of contact and compressional forces existing between the fastener and the materials it is traversing.

[0026] A first mandrel component can be composed of malleable / flexible / deformable materials that are deformable upon contact with an energy producing handheld device where the amount and manner of energy transfer does not produce injury (cause tissue necrosis) to biological tissues. The deformation results in a change in geometry from an elongated slender structure to a widened dome shaped structure to increase the surface area of contact and compressional forces between the fastener ends and the materials it is traversing. In an example, a first mandrel component is provided having a superior shaft region having an embedded drive recess geometry that when exposed (by cutting the mandrel shaft through the drive recess) reveals an opening which matches the drive geometry within the tip of an energy producing handheld device. The recess can be placed at a distance from the portions of the fastener that penetrate the bone so as to eliminate the possibility of drive entry (thereby weakening the fastener) into the regions of the fastener that penetrate the bone upon deformation of the outer mandrel shaft segment.

[0027] In another example, the first mandrel component includes a widened mandrel head inferiorly having a drive recess geometry on its surface which matches the drive geometry of an energy producing handheld device. The drive recess is placed at a distance from the rivet body of the fastener so as to eliminate the possibility of drive entry (thereby weakening the fastener) into the regions of the fastener that penetrate the bone upon deformation of the inferior mandrel head segment.

[0028] In yet a further example, the second outer rivet component can be rigid, inflexible, and not deformable by the amount of energy required to safely deform the first mandrel component shaft and head segments. The second outer rivet component can include a shaft / core / body with a screw thread pattern, smooth without threads, or a customized patterned geometry.

[0029] Implantable radiolucent thermoplastic plates and rods of the a system of the present disclosure may also include a radiolucent thermoplastic plate overlying a bone or rod lying within the medullary cavity of a bone configured to stabilize fractures and / or bone defects, and a radiolucent thermoplastic plate overlying a bone or rod lying within the medullary cavity of a bonehaving one or more pre-drilled holes intended to receive fasteners for securing plates or rods to bone. The plate can further include a countersunk or counterbored geometry on its receiving surface (where the screw head will sit) that is slightly wider than the screw head to accommodate ingression of deformed welded material so as to provide for a locking mechanism between the deformed welded material, the head of the screw, and the plate.

[0030] Specialized instrumentation of a system of the present disclosure may also include customized cutting and or molding taps designed to cut female threads in predrilled pilot holes in bone where the threads match the male thread geometry of the radiolucent thermoplastic fastener. A customized driver engineered to engage radiolucent thermoplastic fasteners having a superior malleable grip segment, can be provided where the driver has an opening that fits the geometry of the fastener head and a second opening above that allows for passage of the superior malleable grip segment so that as force is applied from the driver to the fastener head to tighten the screw, no force is applied to the superior malleable grip segment. This may eliminate the possibility of shearing the superior malleable grip segment off of the head of the screw upon fastener insertion. The driver may include an opening having a vice clamp mechanism that engages the fastener head and a second opening above that.

[0031] In another example, a customized hand clamp style riveting instrument is provided to deploy the blind end rivet type radiolucent thermoplastic fastener riveting mechanism by engaging the mandrel shaft as force is produced in a clamping motion. The force can be transmitted to the mandrel shaft to pull the mandrel shaft segment through the rivet body, engaging the mandrel head with the distal rivet body tip, and causing a dome like deformation so as to increase the surface area of contact and compressional forces between the fastener ends and the materials it is traversing. A customized hand clamp style riveting instrument can be provided with a cutting tip that aligns with an embedded drive recess within a blind end rivet type radiolucent thermoplastic fastener upon clamping, which when cut and exposed forms the drive recess receptacle for the drive tip of a heat generating handheld device.

[0032] Heat generating handheld devices of the present disclosure may also include: a handheld device that transforms other energy sources into heat, where the energy source can be ultrasound, microwave, laser, electromagnetic, radiofrequency, plasma energy, or the like, and converts the energy into heat that is concentrated at the tip of the handheld device. The handheld device can be configured to transform other energy sources into heat, which can then be used to deform, stake, and or weld thermoplastic materials in a manner that avoids thermal injury within biological tissues. The handheld device can include an ultrasonic welder, a bovie device, a soldering iron, a fluid heated probe, an air heated probe.

[0033] Specialized attachment arrangements and configurations for the heat generating handheld devices may also include an attachment configured to have a tip with a receptacle geometry that dictates the resultant shape of heated thermoplastics upon deformation. The attachment can be configured to have a tip with a male geometry contact drive point that matches the recess geometry of radiolucent thermoplastic fasteners where the male geometry contact drive point is positioned in a receptacle geometry in a manner that avoids penetration of that contact drive point into the neck or core / shaft / body (any portions of the fastener penetrating bone) components of radiolucent thermoplastic fasteners so as to avoid weakening the fastener upon insertion. The tip can include the receptacle geometry and the male geometry contact drive point positioned perpendicularly to a long axis of the attachment so as to facilitate engagement and heating of thermoplastic segments where there is limited visualization and access. The handheld device can be designed in a clamp configuration where the tips of the clamp (having receptacle geometries and male geometry contact drive points) are both positioned perpendicularly to the long axis of the handpiece so as to facilitate simultaneous clamping, heating, and deformation of malleable grip segments or mandrel head segments on radiolucent thermoplastic fasteners.

[0034] Other technical features may be readily apparent to one skilled in the art from the following figures, descriptions, and claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0035] To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the figure number in which that element is first introduced.

[0036] FIG. 1A illustrates an oblique schematic view of a long bone with a central defect (gap) to which a radiolucent fixation osteosynthesis device is provided having a radiolucent plate (bar) through which a series of fasteners are shown penetrating through it and into and through the lateral adjacent segments of the long bone.

[0037] FIG. IB illustrates the long bone of FIG. 1A with an intramedullary rod engaged with the radiolucent plate.

[0038] FIG. 2 illustrates a schematic diagnostic ex vivo image, such as x-ray or Micro- Computed Tomography (pCT) of end segments of a long bone with a central defect, where the metal fasteners have been removed to demonstrate a normal perception of radiodensity without metal artifact, which, will be referred to as a “Base Example” throughout the various examples.

[0039] FIG. 3 illustrates the schematic diagnostic image of the base Example of FIG. 2 with a Region of Interest (ROI) shown as an area inside a box, and a developing segment of regeneratebone circled in a top right area of the ROI to visually define a normal radiodensity perception of the regenerating bone within the ROI.

[0040] FIG. 4 illustrates a schematic example of a front and cross-sectional view of a long bone with a central defect fixed with a radiolucent osteosynthesis device having a radiolucent plate and fasteners where the defect site between bone end sections (referred to as the ROI) is identified within a tubular member.

[0041] FIG. 5 illustrates schematic diagnostic images of the Base Example of FIG. 2 (shown here as A, next to an image of the exact same bone imaged with metal screws inserted (positioned in the bone) shown as B.

[0042] FIG. 6 illustrates the schematic diagnostic images of the Base Example of FIG. 2 (shown here as A), next to an image of the exact same bone imaged with a radiolucent osteosynthesis device (shown as B).

[0043] FIG. 7 illustrates schematic diagnostic sample images of the Base Example bone of FIG. 2 produced (with metal screws in vivo) by three independent X-ray technicians and each technician independently following the same bone positioning and alignment procedural instructions, prior to imaging.

[0044] FIG. 8 illustrates schematic diagnostic in vivo longitudinal pCT series of images of a femur with a defect fixed with an RFS device; the images show the progression of healing of a femur having a central defect treated with bone morphogenic protein which successfully led to regenerate formation and bone bridging over time.

[0045] FIG. 9 illustrates schematized depictions of three different methods of fastener insertion in a long bone traversing a medullary cavity, with (A) showing an undesired “poor” uni- cortical penetration; (B) an undesired “poor” unpredictable penetration; and (C) a desirable bi- cortical penetration.

[0046] FIG. 10 is a schematic plan view of an example radiolucent thermoplastic screwtype fastener configured for use in fixing bone segments.

[0047] FIG. 11 is an oblique view of a wireframe drawing showing a configuration of a fastener driver having an internal cavity configured to engage with and drive the fastener of FIG.10 during implantation.

[0048] FIG. 12 A shows CAD 3D renderings of an initial step of the fastener driver of FIG.11 in performing fastener insertion, such as during surgery.

[0049] FIG. 12B is a progression CAD rendering from the insertion of FIG. 12A in a partially inserted configuration.

[0050] FIG. 12C is a further progression from FIG. 12B of the CAD rendering from the insertion of FIG. 12A in an inserted configuration.

[0051] FIG. 12D is a magnified view of the insertion from FIG. 12A.

[0052] FIG. 12E is the insertion view of 12D in a fully inserted configuration.

[0053] FIG. 13 is an exploded view of the radiolucent thermoplastic screw-type fastener ofFIG. 10 interposed between two concave receptacle tips used to clamp malleable grip segments of the fastener and deform them into a dome like shape (not shown).

[0054] FIG. 14 illustrates an oblique view of a clamping handpiece which attaches to an energy producing device, where the tips of the clamping handpiece house concave tips of FIG. 13.

[0055] FIG. 15A illustrates progressive steps of an example fastener securing method where malleable grip segments are engaged (a), clamped (b), and released (c) by a clamping handpiece to execute steps in a deformation process utilizing an energy clamping handpiece as described in FIG. 14 operating on fasteners of FIG. 10.

[0056] FIG. 15B illustrates a magnified view of the operative fastener securing method of FIG. 15A that are engaged (a), clamped (b), and released (c).

[0057] FIG. 15C illustrates an example intramedullary rod configured as a stabilizing core member utilized in long bone repair of the type provided in FIG. 1 A - FIG. IB.

[0058] FIG. 16 illustrates images of differences in resultant weld geometry of an end of the fastener of FIG. 10 after weld completion where (A) shows an irregular geometry and (B) shows a preferred dome shaped geometry.

[0059] FIG. 17 is a schematic example of a poorly placed drive recess where the drive recess extends through a neck of the fastener which can weaken the fastener and lead to fastener failure.

[0060] FIG. 18 illustrates an example of an angled concave tip attachment tool having a concave dome shaped molding receptacle.

[0061] FIG. 19 illustrates a schematic side view of a radiolucent thermoplastic blind-end rivet-type fastener for use in fixing bone segments where access to an inferior malleable grip segment extending beyond the distal cortex is not possible.

[0062] FIG. 20 illustrates a hand clamp-style riveting instrument.

[0063] FIG. 21 illustrates schematic cross-sectional views of three progressive steps demonstrating: (A) initial positioning, (B) deforming of an inferior end of a radiolucent thermoplastic blind-end rivet type fastener in a hole (or opening) of the bone reinforcing plate and the underlying bone using the riveting instrument of FIG. 20, and (C) separating and removing the riveting instrument from the fastener.

[0064] FIG. 22A illustrates a cross-sectional view of securing a superior portion of the rivet by applying heat energy using a heating and forming tool.

[0065] FIG. 22B illustrates the rivet of FIG. 22A after application leaving a top of the rivet in a substantially dome (rounded top) expanded shape.

[0066] FIG. 23 is a flow chart of a process of positioning a radiolucent osteosynthesis device to bone segments, securing them and repeatedly imaging them as time passes and bone heals, and being able to observe clear images.DETAILED DESCRIPTION

[0067] The present disclosure provides for radiolucent fixation systems including osteosynthesis plates, rods, and fasteners, instruments and devices for implantation, and thermoplastic joining methods for safely (i.e., avoidance of unintended injury to biological tissues leading to tissue necrosis) connecting radiolucent plates, rods and fasteners to bone in clinical and non-clinical indications.

[0068] While at some rough comparison level, using the devices and systems of the present disclosure allows for different bones (similarly sized) in different experimental subjects to be imaged and deemed to be "identical," a more refined detailed analytical examination or focus will find differences between (such so called identical) subjects (including within bone structures), which are in fact different, and which, as such, can introduce an unaccounted-for variability in the study results. In addition, the monitoring of one subject (and its bone structure) over time would provide repeated measures experimental study designs, since the "same" rather than different subject's healing progress is being measured and such a study configuration yields significant time and cost savings.

[0069] The following models / equations demonstrate the economic relationships between traditional longitudinal methods and a RFS longitudinal method utilizing radiolucent fixation systems:• S: study costs (personnel, animals, animal care, surgeries, and surgical supplies)• t: the number of longitudinal time points• $TS: total costs for a traditional study o $TS = S • t• $TS(RFS): Total study cost with radiolucent fixation systems o $TS(RFS) / 1

[0070] Similarly, the comparison can be used to describe the number of animals saved with the radiolucent fixation system method:• n: number of animals• nTS: number of animals in a traditional study o nTS = n • t o Total number of animals with radiolucent fixation systems = nTS / t

[0071] On the basis of the clinical and non-clinical applications that exist, additional systems and methods for radiolucent osteosynthesis are needed.

[0072] Developing radiolucent fixation devices that do not incorporate metal hardware is therefore highly desirable as it would facilitate the imaging of the same animal at multiple timepoints, thereby eliminating the unnecessary sacrifice of “identical” groups of animals at each desired time point.

[0073] Advanced composite flow molding techniques have enabled the production of radiolucent thermoplastics having strength characteristics (and properties) rivaling those available when using soft metals. For example, carbon fiber reinforced PEEK injection flow molding methods now permit the embedding of carbon fibers aligned along intended tensile stress carrying axes into portions of PEEK injection flow molded components in a continuous and organized process, as opposed to introducing such fibers in a random disorganized manner or milling the reinforced material after fiber insertion as such cutting processes shorten the embedded fibers and weaken the material. This carbon fiber reinforced PEEK injection flow molding process improves upon previous methods by giving improvements in material tensile properties along certain component section axes and by improving the ability to achieve reliable repeatability of such improved tensile strength properties in uniformly manufactured parts. Components used in spinal stabilization surgery have incorporated the use of radiolucent thermoplastic carbon fiber reinforced PEEK injection flow molding components to create pedicle fastener systems that restore spinal integrity and improve radiolucency for clinicians imaging and treatment of patients with advanced stage tumors. In using these components, the thermoplastic pedicle screw penetrates and is effectively engaged mechanically with the vertebral pedicle, which is a short, thick bridging bone segment comprised of cortical and cancellous bone.

[0074] Known and available components and techniques are not effective in treating injury and treatment sites in portions of long bone sections, where a hollow medullary cavity predominates the bone architecture. While a vertebral pedicle offers clinically acceptable purchase and stability to a penetrating fastener used in an osteosynthesis system where the core / shaft / body of the fastener is in continuous contact with the adjacent bone, no such continuous contact is available in long bone sections having hollow medullary cavities. Therefore, the prior existing techniques / methods alone are not effective for treatment of defects and / or injuries to long bone sections where use of osteosynthesis systems is considered a treatment option.

[0075] Described herein are radiolucent fixation systems (RFS) for orthopedic applications and thermoplastic joining methods suitable for use in human and animal tissues. In particular, the present disclosure is directed to radiolucent fixation systems comprising osteosynthesis plates, rods, and fasteners, instruments and devices for implantation, and thermoplastic joining methods for safely (referring to the avoidance of unintended injury to biological tissues leading to tissue necrosis) connecting radiolucent plates and fasteners to bone in clinical and non-clinical indications.

[0076] The reconstruction of bone segments after they have been fractured or when defects in their structure have been detected frequently requires the use of osteosynthesis systems that can accommodate the static and dynamic forces imparted by bone loads at the fracture or defect site over time. In the past metal fasteners have commonly been utilized to secure a plate and / or a rod to bone. Radiolucent thermoplastic fasteners offer many advantages when compared to metal counterparts, such as avoiding generation of imaging artifacts, allowing the unimpeded passage of radiotherapy to a target tumor site, and avoiding creation of stress-shielding effects in the bone.

[0077] A difficult challenge in attaching a thermoplastic fastener implant to a long bone near its mid-shaft relates to how to traverse the anatomy of the bone mid-shaft (diaphysis), when the bone geometry includes a hollow medullary cavity (while the term "hollow" implies an absence of material in fact the "hollow space" is filled with yellow marrow) interposed between two dense cortices of bone. In one such use, a fastener passes through an opening in an external plate and enters and passes through proximal and distal openings in the perimeter cortex section of the long bone to achieve purchase (a firm grip or grasp, footing, etc., on something) with the proximal and distal cortex to establish a substantially stable engagement with the bone segment having both cortices.

[0078] In current fastener and plate structure orthopedic systems the pressure between mating components is applied only through the contact area established by the component's contact area, where portions of the outer surface of the male threads in the fastener are engaged with mating portions of the inner surface of the female threads cut into the bone and the bone plate hole into which the fastener is positioned. Current commercially available metal orthopedic bi-cortical (passing through two cortices) systems use self-tapping screws, where the diameter of the head of the screw is larger than the diameter of the hole penetrating the external plate through which the fastener extends. Such an arrangement allows the force on the contact surface area between the fastener head and plate receiving hole fastener head receiving surface to create and maintain pressure (force) between the two components. This fastener head engagement arrangement reduces the localized peak pressure experienced in the fastener material as the load transmitted between components is distributed over a larger contact area (the portion of the fastener head engaging the bone plate fastener head receiving surface) and material volume and thereby increases the overall strength (maximum load that can be carried effectively through the connection) of the plated bone. To improve strength of the connection, the top end of the fastener receiving holes within the plate can be countersunk or counter bored (this provides an increased complimentarily configured mating contact area between the fastener and bone through which the forces (axial and shear) to be applied can be transmitted as compared to configurations without such extra contact area available). In other configurations, the head of the screw fastener and its mating receiving hole within the plateare threaded and tapped respectively, creating an engagement (force transmission) mechanism between male and female threads that can lock the fastener in a particular position (relative location with respect to one another) with respect to the plate such that there is an increased surface area between touching components and bulk material volume available for load carrying. Such configurations provide improved connection and mechanical strength when compared to similar configurations which do not have such area and volume enhancements to reduce the contact pressure (stress and associated strain) in connection components.

[0079] Thermoplastic radiolucent fastener structures have mechanical material property ratings that are less than similarly configured metal structures constructed using titanium or stainless-steel, and therefore alternative methods and configurations (methods and configurations other than those used with titanium or stainless-steel fasteners) are required to achieve successful fixation in a long bone treatment, such that the mechanical joint strength of the component system and its assembly expected to be achieved is greater than the expected required load to be experienced in the osteosynthesis system used.

[0080] Certain techniques have enabled the use of thermoplastic radiolucent osteosynthesis devices in non-load bearing craniomaxillofacial applications and in spinal stabilization surgeries where thermoplastic fasteners are secured to the spinal pedicle. In each of these examples (e.g. craniomaxillofacial bone and spinal pedicle) the bone being treated has little or no hollow medullary cavity, and the entire shaft of the fastener is continuously supported by, and attains purchase in (and to), the surrounding cortical and / or cancellous bone as it engages and traverses the bone structure.

[0081] Ultrasonic welding techniques have been adapted in non-load bearing craniomaxillofacial applications, to improve the strength of a completed assembly by safely introducing vibratory energy from a handheld ultrasonic device to a head of a fastener (KLS Martin-Sonic Weld), as compared to similar thermoplastic devices which rely only on mechanical engagement between the system pieces to maintain their positions relative to other system components and to the bone being treated. The vibratory energy produces heat friction, which subsequently causes deformation of the fastener head and fastener core / shaft / body regions. As the fastener head deforms, it bonds to the plate, and as the fastener core / shaft / body deforms it fills and takes on the geometry of the surrounding underlying internal bone crevices. This technique is effective over short distances (<10mm) where the majority or entirety of the fastener core / shaft / body is in contact with cortical or cancellous bone.

[0082] Such techniques are impractical for fasteners traversing longer distances and / or circumstances where the fastener must traverse a hollow medullary cavity to ensure purchase at the distal cortex, such as in long bone applications. In long bone applications where the fastener musttraverse the medullary cavity, the fastener itself must have enough rigidity, as there are no guiding forces existing within the medullary cavity to guide the fastener across the void, to traverse the medullary cavity and find purchase at the distal cortex. In cases where the fastener penetrates the proximal cortex, but does not reach the distal cortex, the fastener would be too weakly connected to the bone to effectively support the dynamic forces imparted to the bone repair site by normal physiologic loads. In cases where the fastener penetrates the proximal cortex and is deformed to a misaligned position prior to penetrating the distal cortex, the fastener would similarly be too weak to support the dynamic forces imparted by normal physiologic loads (See FIG. 9). This is the case for an example when attempting to utilize commercial craniomaxillofacial systems (KLS Martin- Sonic Weld) where the head of the fastener is heated and dynamic deformation of the entire fastener occurs while being inserted into bone, in long bone applications. This is largely due to a uniform fastener material composition where uniform mechanical (e.g., dimensional) and thermal deformation characteristics of the fastener material prevent the fastener from reaching the distal cortex before the deformation process occurs.

[0083] Extrapolation of previous techniques used in bone sections composed of nearly exclusively cortical and cancellous bone material for use in treatment of sections of long bone, require significantly improving the load transmitting capabilities of thermoplastic osteosynthesis systems. One approach is to increase the thermoplastic footprint of the fasteners used for engagement by either increasing the core / shaft / body fastener diameter or by increasing the number of fasteners that would be needed when compared to traditional metal osteosynthesis methods. However, increasing the fastener core diameter or number of fasteners comes at the price of weakening the surrounding stabilizing bone architecture. A more efficient approach would be to maximize the load carrying characteristics of the fastener segments outside of the penetrating regions of bone by welding, heat staking, and / or molding methods for example, such that the load experienced by the fastener core / shaft / body regions are more evenly distributed to the top and bottom portions of the fastener that come into contact with the support plate and bone itself.

[0084] The present disclosure provides for implementation methods and apparatuses that use radiolucent fixation systems for long bone fracture and / or defect fixation and treatment. In these examples, the medullary cavity is traversed with a thermoplastic fastener system which ensures a normal physiological load bearing purchase between the fastener system and the bone material at the distal cortex of the fastener hole, while not significantly increasing the fastener core diameter, or number of fasteners needed when compared to conventional metal osteosynthesis fasteners intended for identical purposes.

[0085] The present disclosure provides for a Radiolucent Fixation System (RFS)) including fabrication and use of radiolucent thermoplastic fasteners (screw type and blind-end rivet type),their methods of insertion, and methods for strengthening the fastener, plate, and bone post treatment assembly in an osteosynthesis system. This may include, but are not limited to, the use of riveting, welding, molding, and heat staking processes that are safe for use adjacent to, in contact with, and within biological tissues. In addition, these processes may be achieved or reinforced with radiolucent adhesives such as Polymethylmethacrylate or cyanoacrylate, or radiolucent ultraviolet curing adhesives. Devices that are used and facilitate creation and use of such embodiments include, but are not limited to: 1 -Radiolucent thermoplastic plates and rods; 2-Radiolucent thermoplastic material fasteners; 3 -Heat generating handheld devices and specialized attachment arrangements and configurations that enable thermoplastic welding and staking within biological tissues, (such that they might significantly increase the strength of the finally assembled osteosynthesis system); 4-Specialized instrumentation such as special taps and drivers engineered for careful insertion of thermoplastic fasteners in osteosynthesis applications.

[0086] Referring to the FIGS., improved systems, devices, and methods for overcoming the shortfalls described hereinabove are provided. FIG. 1A-1B illustrate a schematic of a long bone 100 with a central defect 102 shown as a gap to which a radiolucent fixation osteosynthesis device 104 is shown having a radiolucent plate 106 (bar) through which a series of fasteners 108 are shown penetrating through it and into and through the lateral adjacent segments of the long bone. In FIG. IB, an intramedullary rod 110 is provided having holes for passage of the fasteners 108.

[0087] FIG. 2 shows a diagnostic ex vivo image 200, such as x-ray or Micro-Computed Tomography (pCT) of end segments 202 of a long bone 100 with a central defect 102 between them, where metal fasteners in an osteosynthesis system holding the bone segments 202 in the imaged orientation relative to one another, have been removed so that the image illustrates a baseline perception of bone radiodensity without metal artifacts in the image. This will be referred to as a “Base Example” throughout the various examples.

[0088] FIG. 3 shows a diagnostic image of the Base Example of FIG. 2 with the ROI 300 in a shaded rounded corner rectangle, and a developing segment 302 of regenerate bone circled in the ROI 300 to visually identify the normal radiodensity perception of the regenerating bone within the ROI 300.

[0089] FIG. 4 shows a schematic example of segments 402 of a long bone 400 with a central defect fixed with a radiolucent osteosynthesis device 406 having a radiolucent plate 408 and fasteners 410 where the central defect 404 forms a ROI 412 is highlighted in a light shading. This demonstrates how the rotation (R) of a femur to an alignment directly perpendicular to a plane of x-ray entry would limit metal scatter artifact to this perpendicular plane and enable visualization of the ROI 412. To illustrate this, a cross section of the ROI 412 is shown after rotation with electron electric bolts 414 illustrating a direction of passage of x-rays through an optimallypositioned ROI 412. While this method is known, it mostly reduces scatter and does not eliminate beam hardening effects (darkening of bone adjacent to metal screws), which can affect a viewers' perception of radiodensity.

[0090] FIG. 5 shows example diagnostic images A and B of the Base Example next to an image of the exact same bone imaged with metal screws inserted (positioned in the bone). The metal screws are shown defining an axis of each screw being generally aligned parallel to one another. The metal screws are positioned (configured) to be perpendicular to a central axis of the x-ray beam source within a pCT scanner as described to generate the images shown. These images demonstrate the differences and the limited visibility of an ROI, the effects of x-ray scatter, and beam hardening introduced by using metal screws.

[0091] FIG. 6 shows image A for an example diagnostic image of the Base Example. Image A is next to an image B of the exact same bone imaged with a radiolucent osteosynthesis device (rather than metal screws). The differences between images A and B demonstrate the clear difference in the clarity of visibility of the ROI as previously observable radio wave artifacts (shown in FIG. 5) are absent due to the elimination of metal in the subject image B.

[0092] FIG. 7 shows diagnostic sample images A, B, C of the Base Example bone of FIG. 2 produced (with metal screws in vivo) by three hypothetical independent X-ray technicians 702, 704, and 706, each independently following the same bone positioning and alignment procedural instructions. The differences between images A, B, and C illustrate different scatter and beam hardening effects showing how despite procedural conformity in instructions, actual minor differences in bone sample positioning within the scanner, by different hypothetical X-ray technicians can alter the details of the image. This occurs despite the fact that the subject bone is the same and thereby misidentify (and incorrectly classify) the density of a forming bone regenerate. The images show different bone densities on the different images generated by different hypothetical X-ray technicians, when in fact there is no actual difference of the subject bone. Note the differences are identified in the portion of the image indicated by the vertical ellipses.

[0093] FIG. 8 shows a diagnostic in vivo longitudinal pCT imaging series A, B, and C of segments 804 of a femur 802 with a defect there between fixed with an RFS device of the present disclosure. The images show the progression of healing of a femur having a central defect treated with bone morphogenic protein which successfully led to regenerate formation and bone bridging over time. The images A, B, and C show repeated longitudinal imaging at selected time intervals without the significant visualization limitations imposed by metal artifacts shown for the images of FIG. 7.

[0094] FIG. 9 show cross sectional schematic depictions (A, B, and C) of three different methods of fasteners insertion in a 902 traversing a medullary cavity 904 where (A) shows aunicortical bone section penetration that has failed to reach a distal cortex 906, (B) shows an unicortical bone section penetration (whose direction of travel and positioning has become unpredictable inside the medullary cavity 904) where a tip 908 of the fastener has changed its direction of motion inside the medullary cavity 904 randomly, thus its tip has failed to reach the distal cortex 906, and (C) shows an image of a desired scenario where the fastener achieves bicortical penetration.

[0095] FIG. 10 is a schematic plan view of an example of a radiolucent thermoplastic screw type fastener 1000 for use in fixing bone segments. Fastener segments include: a superior malleable grip segment 1020, an inferior malleable grip segment 1030, and a central component 1010. The central component 1010 having a central component head 1012, a central component core / shaft / body 1014, a core / shaft / body neck 1016, and defines a diameter 1017. The superior malleable grip segment 1020 extends from a head side 1013 of the central component head 1012, and includes a centrally located superior drive recess 1022 in its superior end. An inferior malleable grip segment 1030 extends from the central component core / shaft / body 1014 and defines a tip end 1015. The inferior malleable grip segment 1030 includes a centrally located inferior drive recess 1032 in its inferior end.

[0096] FIG. 11 is an oblique view of wireframe 3-D drawing showing a configuration of a fastener driver 1100 defining an internal cavity 1102 having a lower internal diametral surface geometry 1104 whose dimensions and configuration are such that it can be complementarily mated to an outside diametral surface geometry 1006 of the central component head 1012 of the fastener 1000 shown in FIG. 10. Fastener driver 1100 has an extended (upper) portion of its internal cavity having diametral dimensions slightly larger than the diametral dimensions of the complementarily sized and shaped superior malleable grip segment 1020 to complementarily surround but not contact the outside diametral geometry of the superior malleable grip segment 1020. This provides that there is no contact between the superior malleable grip segment 1020 and the extended portion of the internal cavity when the fastener driver 1100 is engaged on the superior end of the fastener 1000, so that no rotating force exerted on the fastener driver can be transferred to the superior malleable grip segment 1020 and to avoid transferring a shearing force from the fastener driver 1100 to the superior malleable grip segment 1020 during fastener insertion and fixation.

[0097] FIG. 12 shows a series of CAD 3-D renderings A, B, C, D, and E showing the progressive steps in use of the fastener driver 1100 in a method performing fastener 1000 insertion and fixation: (A) shows an initial positioning of a radiolucent fastener 1000 into a hole (or opening) of a bone reinforcing plate 1102 and an underlying bone 1104, (B) shows an application and use of a fastener driver 1100, as shown in FIG. 11 to drive the central component head 1012 of the fastener 1000 to the limit of its travel, with the head 1012 in a position adjacent to and in contactwith the bone reinforcing plate 1102, and (C) the separation of the fastener driver 1100 from the installed fastener 1000, showing the final position of the fastener 1000 penetrating through a distal cortex of the adjacent bone segment, with the fastener 1000 fully tightened to the bone reinforcing plate 1102 and bone segment. Note that the smaller diameter of a superior malleable grip segment 1020 is in relation to the diametral dimension of the central component head 1012 of the fastener 1000, and the smaller diameter of the inferior malleable grip segment 1030 is in relation to the diameter 1017 of the central component core / shaft / body 1014 of the fastener 1000. Images D and E are close-up views of the right end of the bone reinforcing plate 1102. In image D the bone reinforcing plate 1102 is positioned on the segment of the bone to be treated. The fastener 1012 is shown positioned in a third bone-plate-opening, such that the bone segment below and facing the bone plate opening has been drilled and tapped with female threads that complementarily receive the threads 1028 of the fastener 1000. The fastener driver 1100 is shown about to engage a top of the fastener 1000. Note that in this example, each opening in bone reinforcing plate 1102 includes a countersunk hole 1110 portion, a shoulder 1114 at the bottom of the countersunk hole 1110 and a through hole 1112 having a diameter smaller that the diameter of the countersunk hole 1110. Image E shows the fastener 1000 fully inserted and fixed (threaded into the bone) with the bottom of a hexagonal central component head 1012 pressing against the shoulder 1114 in the hole 1110 causing the plate 1102 to press against and hold the bone stationary. The threads and the tip end 11016 of the fastener 1000 have passed through the bone 1104 and can be seen below the bone segment.

[0098] FIG. 13 is an example exploded cross sectional view of a radiolucent thermoplastic screw type fastener 1000 interposed between two metal concave receptacle tips 1310, 1320 used to clamp superior and inferior malleable grip segments 1020, 1030 and deform them in situ into a dome like shape (not shown). Concave (clamping) tips (see FIG. 14) form part of an energy producing clamping handpiece that transfers heat energy to the concave receptacle tips 1310, 1320. An example sectional exploded concave receptacle and fastener drive recess cross section shown, illustrates a (mushroom shaped) concave internal geometry of the two metal concave receptacle tips 1310, 1320. Each has a tip drive 1312 (a sharp pointed conical or pyramid shaped alignment having a narrowed insertion tip 1314 at its end and a mushroom top insertion depth limiting component 1316 fixed to the center of the inner roof surface of each of the two metal concave receptacle tips). Matching drive tip receiving recess cavities (1022, 1032) are provided on the end outer surface of the superior and inferior malleable grip segments 1020, 1030.

[0099] FIG. 14 shows an oblique view of an example clamping handpiece 1400 mechanism configured to attach to an energy producing device, where the tips of the clamping handpiece house concave receptacle tips 1310, 1320. The clamping handpiece 1400 connects to an energy generatingpower source (not shown) to convert and deliver the energy in the form of an increase in temperature (as thermal energy is transmitted (heat) flows) through the concave tips.

[0100] FIG. 15A shows overall and close up views of the progressive steps (a), (b), and (c) in a fastener securing method where the malleable grip segments are engaged, clamped, and released by the clamping handpiece 1400 to execute steps in a deformation process utilizing the idealized energy clamping handpiece 1400 described in FIG. 14 and the fasteners 1000 of FIG. 10, where (a) shows the pre-deformation positioning, (b) demonstrates the clamping deformation process, and (c) illustrates the post-fastener end deformation finished configuration. The energy generating clamping handpiece tool is used to secure the bone reinforcing plate to the long bone with the screw style radiolucent thermoplastic fasteners which have deformed to heat formed (rivet head type) rounded configurations. FIG. 15B illustrates magnified views (a), (b), and (c) corresponding to FIG. 15 A.

[0101] FIG. 15C shows a treatment configuration similar to the shown in FIG. 1 with an intramedullary rod 1500 in the medullary cavity of bone segments 1512, 1514. The intramedullary rod 1500 defines lateral holes 1502a, 1502b, 1502c, and 1502d there through positioned at matching hole locations are 1025a, 1025b, 1025c, and 1025d in the bone support plate 1024. The intramedullary rod 1500 is made of a radiolucent material and is sized and specified to provide support to the bone repair site and is used when the medullary cavities of the bone segments are accessible and the use of a bone plate, e.g., 1024, may not be sufficient to stabilize the bone segments to carry required static and dynamic bone loads that are likely to be experienced in the bone being treated while healing and afterwards. The holes 1502a, b, c, d, in the rod 1500 may be threaded or have a smooth bore, which can be specified by the medical treatment supervisors and support staff.

[0102] FIG. 16 show images A and B illustrating differences in resultant weld geometry (fastener head thermal deformation) patterns where (A) shows an irregular geometry and (B) shows an ideal dome shaped geometry, after having been welded (deformed) using the clamping handpiece 1400 shown in FIG. 14 acting on the fasteners shown in FIGS. 15 A, 15B, and 15C. Note the outer edges of the deformed weld head bonds are shown with the surrounding bone plate material in a localized heat affected zone to bond the two parts together.

[0103] FIG. 17 shows an example fastener 1700 having a head 1720 and a core body 1740. In this example, a poorly placed drive recess 1710 is shown where the drive recess extends through the neck 1730 of the fastener 1700. This can weaken the fastener and lead to fastener failure. The fastener head 1720 has been flattened and the end 1798 of the drive recess 1710 extends through the head and neck of the fastener, thereby weakening it.

[0104] FIG. 18 is an oblique view of an embodiment of an angled concave tip attachment 1800 with a concave dome shaped molding receptacle 1810 having a central tip 1812. This angled geometry facilitates access to the inferior malleable grip segment extending beyond the distal cortex in situations where access to the inferior malleable grip segment is limited.

[0105] FIG. 19 shows a plan view of an example radiolucent thermoplastic blind-end rivet type fastener 1900 for use in fixing bone segments where access to the inferior malleable grip segment 1932 extending beyond the distal cortex is not possible. In this example, fastener 1900 defines a mandrel 1910 extending from a distal mandrel head 1914 to a proximal mandrel shaft 1912. A rivet body 1932 positioned therebetween. The rivet 1930 includes a body 1932 extending from a rivet head 1934 and the mandrel shaft 1932 includes malleable segment recess 920.

[0106] FIG. 20 shows a schematic of a hand clamp style riveting instrument having a handle, a cutting edge, and an opening for mandrel shaft.

[0107] FIG. 21 shows a series of example schematic views A, B, and C progressively demonstrating: (A) the initial positioning of a radiolucent thermoplastic blind-end rivet type fastener in a hole (or opening) of the bone reinforcing plate and the underlying bone, with the horizontal arrows denote the direction of clamping force that elicits a vertical and upward motion of the mandrel (vertical black arrows); (B) shows the deformation of the rivet body tip as the enlarged mandrel head is pushed through it, and the cutting of the mandrel shaft at a point that traverses the malleable grip segment drive recess; and (C) shows removal of the hand clamp style riveting instrument, leaving behind the radiolucent thermoplastic blind end rivet type fastener with the newly exposed drive recess in the superior malleable grip segment for engagement of an energy producing handheld device tip with matching drive geometry.

[0108] FIG. 22 shows a series of sectional views A and B progressively demonstrating: (A) the energy producing concave tip with tip drive in position to engage the matching drive recess in the superior malleable grip segment of the blind end rivet type radiolucent thermoplastic fastener; and (B) the resulting dome shaped geometry of the deformed superior malleable grip segment after energy transfer and welding has occurred. Note that the fastener recess remains within the deformed dome head and remains at a distance from the fastener neck to avoid weakening the shaft of the fastener.

[0109] FIG. 23 shows the steps in a method according to the present disclosure illustrating the progressive steps of positioning a radiolucent osteosynthesis device to bone segments, securing them and repeatedly imaging them as the time passes and the bone heals, and being able to observe clear images. The example process includes the steps of: step 2310- (i) positioning one or more radiolucent thermoplastic osteosynthesis devices of the present disclosure in a position to be attached to bone segments in a patient such that when secured the osteosynthesis devices stabilizethe bone segments across fractures or bone defects between the segments; step 2320- (ii) securing the radiolucent thermoplastic osteosynthesis devices to the bone segments; and step 2330- (iii) imaging and observing clear images of the bone segments and the radiolucent thermoplastic osteosynthesis devices over time within the same patient. The process can include repeated periodic imaging and observing clear images over a healing time period of the bone without removing metal hardware or relying on patient positioning strategies to limit imaging artifacts caused by metal interference.

[0110] Existing commercially available thermoplastic devices fail to fully address the intricacies that accompany load bearing applications existing in long bones where the medullary cavity must be traversed. While the RFS embodiments presented herein are designed to address these limitations, it should be noted that the reinforcements disclosed to facilitate long bone fixation will also improve upon current state-of-the-art thermoplastic fixation methods regardless of bone compositions (cortical, cancellous, cortico-cancellous) or locations (axial or appendicular skeleton).

[0111] During the course of development of embodiments described herein, obstacles in the engineering of a comprehensive radiolucent fixation system were overcome. Presented herein are inherent challenges and optimized solutions used to implement radiolucent fixation systems for bone fracture and / or bone defect applications:

[0112] 1 -Fabrication of screw style radiolucent thermoplastic fasteners

[0113] In one embodiment of a screw style radiolucent thermoplastic fastener, the screw head and core / shaft / body form a central component that lies between two adjacent malleable grip segments where the first component is of a different material than the material comprising the outer malleable grip segments. This form utilizing two different radiolucent thermoplastic materials with different mechanical and thermal properties has advantages that allow for the deformation of the outer grip segments upon contact with an energy producing handheld device where the amount and manner of energy transfer does not produce injury (e.g., cause tissue necrosis) to biological tissues such that the deformation results in a change in geometry from a long slender rod like structure of the outer malleable segments to a wide dome shaped geometry to increase the surface area of contact and compressional forces between the fastener ends and the materials it is traversing. While the outer malleable segments are deformable in this manner, the material comprising the central component is rigid, inflexible, and not deformable by the amount of energy required to safely deform the lateral malleable grip segments so as to provide the requisite stability needed in the penetrated regions of the bone. In these cases, fabrication of screw style thermoplastic fasteners with mixed materials is challenging due to the disparities in the thermal deformation properties (e.g. melting points, glass transition temperatures, flow characteristics, and deformationcharacteristics under pressure) of the differing fastener materials. When constructing the fastener, the malleable outer grip segment material can be comprised of radiolucent biocompatible materials whose thermal deformation properties are such that deformation of the material will occur upon contact with an energy producing handheld device where the amount and manner of energy transfer does not produce injury (cause tissue necrosis) to biological tissues. These materials can be inert such as polycarbonate (PC), polyamide (PA) or polyethylene (PE) for example, or resorbable such as polylactide (PLA) and its derivatives poly-DL-lactide (PDLLA), poly-L-lactide (PLLA), polycarprolactone (PCL), or glycolide for example. The central component material can be fabricated using more rigid, inflexible materials, when compared to the outer malleable grip segments, that are not deformable by the amount of energy required to safely deform the lateral malleable grip segments so as to provide the requisite stability needed in the penetrated regions of the bone. These materials can be inert, such as Polyetheretherketone (PEEK) and its related derivatives, or PEEK, PC, PA, or PE, for example mixed with strengthening reinforcing agents such as carbon fiber, glass fiber, hydroxyapatite or beta-tri calcium phosphate for example. These materials can also be resorbable, such as such as PLA, PDLLA, PLLA, PCL, or glycolide for example mixed with strengthening reinforcing agents such as carbon fiber, glass fiber, hydroxyapatite or beta-tri calcium phosphate for example.

[0114] These example mixed material fasteners can be fabricated by pre-fabricating the separate segments (such as the central component, the superior malleable grip segment and the inferior malleable grip segment) either by additive manufacturing methods such as 3D printing or injection molding, or subtractive manufacturing, such as CNC milling. Once each component is fabricated, the parts can be assembled via heat staking, or welding the different components together. Another method of composition includes two shot injection molding (overmolding) where the central component is injection molded first, then sequentially, the outer malleable grip segments are molded onto or overmolded onto the central component to achieve the final pre installation geometry of the fastener.

[0115] Note that the outer malleable grip segments and central component of the screw style thermoplastic fasteners do not have to be made from different materials. Some materials such as glass filled polyamides (gfPA) are very rigid yet have a deforming temperature that is low enough to be safely reached during surgery. In these cases, the distance between the heat generating handheld device tip as it engages the malleable grip segment (for example), and the core / shaft / body of the fastener is critical. If there is enough distance between the heat generating handheld device tip and the fastener core penetrating the bone, the generated heat will deform the outer malleable grip segment of the fastener, while the core / shaft / body remains shielded as the heat dissipates over distance. In this single material screw style radiolucent thermoplastic fastener embodiment, thefastener can be fabricated as a single unit since the first central component and the outer malleable grip segments are of the same material. This can be accomplished through additive manufacturing methods such as 3D printing or injection molding, or subtractive manufacturing, such as CNC milling.

[0116] The materials in the radiolucent thermoplastic fixation device and the weld geometries can be adjusted accordingly to the population that the device is intended to serve and its intended use within that population. For example, there are large disparities between the required load bearing characteristics existing within the long bones within a species, and furthermore, within the long bones between different species. This range of possibilities is directly related to the strength needed, and how that required strength relates to patient size and temporal length of device use. For example, a lighter pediatric patient requiring this device for a short time period will not need the same device strength as an obese adult where the device is expected to support physiologic loads for a long time period for a given load bearing fracture. A basic knowledge of each use situation and an ability to select appropriate materials for these purposes are required to construct an embodiment according to the present disclosure.

[0117] 2-Traversing the medullary cavity and ensuring penetration and / or purchase with thermoplastic fasteners

[0118] Traversing the medullary cavity and ensuring penetration and / or purchase with thermoplastic fasteners at the proximal and distal cortices can be accomplished by using a pilot hole, a specialized tap, and reliance on a fastener having a relatively rigid inflexible central component that will not shear or deform upon insertion. The rigid inflexible central component may consist of a stake (shaft) or a threaded screw, where the resistance encountered when using a mechanical driver in driving the stake or threaded screw through the pilot hole in the proximal and distal cortices can be recognized in a tactile fashion (in the process shown in FIG. 12 (A and D). For example, the friction encountered when driving a screw with a screwdriver through a dense material such as wood would elicit an increased sensation of resistance to the users’ hand when compared to a softer material such as cardboard. Likewise, when a radiolucent thermoplastic screw style fastener is driven through a pilot hole in the central region of a long bone, the resistance encountered in the cortical regions is much higher than those encountered as the screw traverses the medullary cavity, where there is little resistance. Therefore, the order of tactile resistance sensation would be high as the screw penetrates the proximal cortex, low as it traverses the medullary cavity, high again as the distal cortex is penetrated, and then low as the screw moves beyond the distal cortex. This mechanical tactile connection to the user’s hand is important to ensure purchase of the screw at the distal cortex. This tactile reassurance is not possible with other commercial systems where fasteners are comprised of pins for example that are ultrasonicallywelded at the same time they enter the bone, as the softening of the fastener material in the core / shaft / body region generally makes the trajectory of the pin tip more random and unreliable with respect to reaching the distal cortex (See FIG. 9).

[0119] 3 -Avoidance of injury to tissues surrounding the tip of the fastener beyond the distal cortex

[0120] The RFS fastener design of the present disclosure is configured to avoid the potential for injury secondary to exposure of sharp flutes designed for self-tapping conventional screws. Metal bicortical orthopaedic screws are commonly self-tapping. The fabrication of self-tapping screws involves the creation of flutes having sharp edges in the threads of the screw (tip and along its length as needed) that are parallel to the axis of the screw shaft. The flute’s sharp edges with several threads creates a configuration that functions as a sharp cutting guide for those threads, allowing the sharp edges to cut a pattern in the bone that the remaining unaltered (unfluted) threads in the shaft can then follow. When using a bicortical screw, successful fastening is achieved, by definition, when the tip of the screw penetrates the distal cortex, leaving the screw tip and its sharp end cutting flute edges, and sharp thread edges exposed. This is a known drawback of osteosynthesis, and generally care is taken to optimize the length of the screw to minimize the amount of the screw tip that protrudes beyond the distal cortex. During the initial period after wound closure, tissues adjacent to, or in contact with, the bare screw tip are injured or at risk for further damage or injury as a result of being cut and / or irritated by the sharp edges of the exposed screw tip. Often blood vessels, nerves, lymphatics, and connective tissues are found in near proximity or in direct contact with these known danger points. Radiolucent thermoplastic fasteners as currently constituted are not stiff or rigid enough (have material properties that make them acceptable) to be used as self-tapping screw structures in orthopedic surgery. As such, when using radiolucent thermoplastic fasteners in orthopedic surgery, a pilot hole is created at the intended treatment site and then a customized metal tap is used to create the threads in the bone for the thermoplastic threads of the fastener to follow. Since there are no thread cutting elements in the fastener or its tip, the fastener tip geometry itself does not need to be pointy, sharp, or have sharp cutting flutes. It can be curved or rounded to avoid damage between the screw tip and the adjacent tissues.

[0121] 4-Avoidance of shearing of the superior malleable grip segment

[0122] Avoiding shearing of the superior malleable grip segment upon mechanical insertion was accomplished by minimizing or eliminating contact between the driver and the malleable superior grip segment and maximizing contact between the dense, inflexible fastener head material and the driver (e.g., shown in FIG. 11). This was achieved by slightly reducing the diameter of the superior malleable grip segment in comparison to the rigid head diameter and giving the rigid heada non-circular geometry complementary to that of the handheld driver matching cavity so that rotational torque could be passed between the driver and the fastener head when the driver is rotated. In some embodiments, the handheld driver tip consists of a regular matching geometry to that of the rigid fastener head and has a hollow cavity above this contact point to allow for passage of the superior malleable grip segment. In other embodiments, the handheld driver tip is comprised of a vice or chuck with adjustable jaws which meet the widened rigid fastener head surface, while avoiding contact with the softer superior malleable grip segment.

[0123] 5 -Avoidance of shearing of the inferior malleable grip segment

[0124] Avoiding shearing of the inferior malleable grip segment upon mechanical insertion was accomplished by eliminating contact between the bone being penetrated and the inferior malleable grip segment. This was achieved by slightly reducing the diameter of the inferior malleable grip segment in comparison to the outer diameter of the central component core / shaft / body diameter so that the inferior malleable grip segment could be passed through the pilot hole within the bone being penetrated without contact, while the threads of the central component core / shaft / body attained purchase in the cortical regions (e.g., FIG. 12 (E)).

[0125] 6-Management of deformation of the superior and inferior malleable grip segments

[0126] Management of deformation of the superior and inferior malleable grip segments needed to enhance the overall construct strength is accomplished by deforming the superior and inferior malleable grip segments to enlarge their slender geometry (e.g. long rod shaped) to a defined broadened geometry (e.g. widened dome shaped) dictated by the shape of the molding receptacle of the handheld energy producing device, so as to increase the surface area for contact between the fastener and its mating surface (e.g., FIG. 13). In one embodiment, these molding receptacle tips are connected to the top and bottom of a jointed forceps device having a joint at a distance from the tips, and a handle to control clamping force (FIGS. 14, 15 A, 15B, and 15C). The heat source needed to accomplish this staking method needs to achieve the required heat and pressure required to successfully deform the malleable grip segments while remaining safe for use in biological tissues without posing thermal injury to the bone or surrounding tissues. This can be accomplished with a handheld device that transforms other energy sources (e.g., electrical) into heat, where the energy source can be ultrasound, microwave, laser, electromagnetic, radiofrequency, plasma energy, or the like, and converts said energy into heat that is concentrated at the tip of a handheld device. Likewise, the handheld device may consist of a variety of suitable types, including ultrasonic welders, soldering irons, bovie devices, fluid heated probes or air heated probes for example. As an example, ultrasonic welding methods are now commercially developed for clinical orthopedic utility. These devices convert ultrasonic acoustic waves into vibrational energy that subsequently generate localized heat. An ultrasonic welder consists of a handhelddevice, voltage driver, energy converter, horn and sonotrode tip which can serve as the molding receptacle that will dictate the final form of the material being heat staked.

[0127] While heat requiring riveting methods are commonly used in many other industries, they generally require the use of excessive force and / or excessive heat generation to accomplish the requisite material deformation, which poses several challenges to fastener end deformation implementation in biological tissues. In general, care must be taken to avoid excessive heating of the bone, and deformation of the rigid central component of the fastener. This was accomplished by exploiting the distance and / or heat conducting material properties existing between the rigid inflexible central component materials and the outer malleable grip segments. For example, the distance between the handheld tip as it engages the superior malleable segment, and the central component and its constituents (head, neck, shaft / body / core) of the fastener is important. If there is enough distance between the handheld device tip and the fastener neck / core / shaft / body penetrating the bone, for example, the generated heat will deform the malleable grip segment of the fastener successfully, while the neck / core / shaft / body remains shielded as the heat dissipates over distance. Likewise, if the deforming pressure and temperature of the malleable grip segment is much lower than the central construct deforming pressure and temperature, and the heat source meets the lower deforming pressure and temperature of the malleable grip segment, it will be successfully deformed without causing deformation of the fastener’s central component, and without causing injury to the surrounding bone or adjacent tissues.

[0128] 7-Receptacle tip geometry, malleable segment matching drive recess geometry, and managing the distance of the drive recess relative to the neck of the fastener

[0129] RFS fasteners can also have a recess with a matching geometry to the energy producing handheld device receptacle tip. In these embodiments, the drive recess can be found on the outer surfaces of the malleable grip segments 1020, 1030 (FIGS. 10 and 13). The function of this drive recess is to focus the incoming energy to a point on the head of the fastener. This contact point makes the delivery of heat more uniform and leads to more reliable control and better heat deformation patterns. When the recess is not present, the heat deforming mechanism takes longer to achieve, and the resulting weld geometry can be irregular, as the incoming energy is less concentrated and spread over a larger surface area (e.g., FIG. 16). Irregular deformation patterns have been found that can lead to device failures, and moreover, the rough geometric shapes resulting from unguided deformation patterns can lead to tissue irritations. During the design of the RFS radiolucent thermoplastic fasteners, it was observed that it was important to distance the drive recess, residing in the outer malleable grip segments, from the central component of the fastener, and to design the handheld device receptacle tip with a dome shaped concave recess that would stop the drive tip from entering the neck of the fastener during the heat deformation process,as this could weaken the central component and lead to fastener failure (FIG. 17). Moreover, there are known advantages to the use of dome style riveted fastener ends as are commonly seen in the design of Eiffel style hot rivets which use these dome geometries for the advantages of improving the mechanical strength of penetrating fasteners. This resultant smooth dome-like geometry functions to decrease any irritation that could result from material deformations due to unguided heat deformation patterns that could leave sharp edges.

[0130] 8-Riveting, welding and heat staking in cases of limited or constrained access to the distal end of the fastener

[0131] The mechanism of deforming the inferior malleable grip segment beyond the distal cortex can be dependent on access to that area, and how much dissection is required to reach the inferior malleable grip segment with the required instrumentation. If even limited physical access is possible in the space beyond the distal cortex, a receptacle tip mold can be positioned perpendicular to the long axis of the attachment connecting to the heat generating energy device (FIG. 18). This allows the molding surface to be exposed at a more acute angle (in comparison to a straight receptacle tip that is aligned parallel to the axis of the attachment shaft) to gain access and contact with the inferior malleable grip segment beyond the distal cortex.

[0132] Methods of fastener end deformation are desired that do not require physical and visual access to the inferior malleable grip segment beyond the distal cortex. In an example, this could be achieved mechanically by using a radiolucent thermoplastic blind end rivet type fastener 1900 (FIG. 19). This facilitates deformation (expansion) of the fastener tip as the mandrel head 1914 is mechanically pulled through the distal tip of the rivet body with a force generating specialized riveting instrument (See FIGS. 20 and 21). The material mismatch between the mandrel 1910 and the rivet body 1930 can also be exploited to weld the mandrel shaft to the surrounding rivet body 1930, and the mandrel head to the deformed rivet body beyond the distal cortex of the bone. In one embodiment, ultrasonic welding is used via the visible recess point on the top surface of the superior malleable segment. As the ultrasonic waves move through the shaft, the shaft is heated to a temperature that causes the shaft to become tacky and anneal to the surrounding rivet body material. As this temperature reaches the mandrel tip, the surrounding deformed rivet body is welded to the mandrel tip, and the adjacent bone (FIG. 22). In another embodiment, the mandrel tip is comprised of a shape memory polymer that deforms to a trained shape in response to heat.

[0133] The foregoing description of various forms of the present disclosure has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Numerous modifications or variations are possible in light of the above teachings. The forms discussed were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one ofordinary skill in the art to utilize the invention in various forms and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.

Claims

CLAIMSWhat is claimed is:

1. A radiolucent fixation system for stabilizing a bone defect, comprising:(a) a radiolucent thermoplastic plate configured to overlie a bone and having at least one hole for receiving a fastener;(b) a radiolucent thermoplastic fastener including:(i) a rigid central component having a head and a core;(ii) at least one malleable grip segment extending from the central component;(c) a heat-generating handheld device configured to apply energy to the malleable grip segment to deform the malleable grip segment and secure the fastener to the plate and bone; and(d) a specialized driver configured to engage the fastener without applying force to the malleable grip segment during insertion.2 The system of claim 1, wherein the plate comprises carbon fiber-reinforced material.3 The system of claim 1, wherein the fastener includes a superior and an inferior malleable grip segment.4 The system of claim 1, wherein the heat-generating handheld device is selected from the group consisting of: ultrasonic welder, soldering iron, fluid heated probe, and air heated probe.5 The system of claim 1, wherein the malleable grip segment includes a recess configured to engage a tip of the heat-generating handheld device.6 The system of claim 1, wherein the fastener comprises different thermoplastic materials for the central component and the malleable grip segments.7 The system of claim 1, further comprising an intramedullary rod configured to receive the fastener for additional bone stabilization.8 A method of stabilizing a bone defect, comprising:(a) positioning a radiolucent thermoplastic plate adjacent to a bone defect;(b) inserting a radiolucent thermoplastic fastener through a hole in the plate and into a predrilled hole in the bone;(c) applying energy from a heat-generating handheld device to deform a malleable grip segment of the fastener and secure the plate to the bone; and(d) imaging the stabilized bone using an imaging modality, wherein the radiolucent plate and fastener produce minimal imaging artifacts.

9. The method of claim 8, wherein the bone defect is a long bone diaphyseal defect.

10. The method of claim 8, further comprising inserting a radiolucent intramedullary rod into the medullary cavity of the bone before positioning the plate.

11. The method of claim 8, wherein the imaging modality is selected from the group consisting of selected from the group consisting of x-ray imager, Computed Tomography (CT) scanner, Micro-Computed Tomography (pCT) scanner, and MRI scanner radio wave imager.

12. The method of claim 8, wherein the fastener comprises a blind-end rivet mechanism.

13. A radiolucent thermoplastic fastener for orthopedic fixation, comprising:(a) a rigid central component including a head and a core with threads or a smooth shaft;(b) a superior malleable grip segment extending from the head; and(c) an inferior malleable grip segment extending from the core; wherein the malleable grip segments are configured to deform upon application of energy to increase contact area and compression forces between the fastener, plate, and bone.

14. The fastener of claim 13, wherein the central component is formed of carbon fiber- reinforced material.

15. The fastener of claim 13, wherein the malleable grip segments are formed of a thermoplastic selected from polycarbonate, polyamide, polyethylene, or combinations thereof.

16. The fastener of claim 13, wherein the superior malleable grip segment includes a recess geometry matching a drive tip of the heat-generating handheld device.

17. The fastener of claim 13, wherein the fastener is configured for bi-cortical fixation in a long bone.

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