Spinal rod with multiple segments having eccentric center

Abstract

A spinal rod with a plurality of sections having an eccentric center for use in a spinal fixation device is disclosed. The spinal rod may include a first longitudinal portion and a second longitudinal portion, the first longitudinal portion and the second longitudinal portion adjoining together by a transition portion. The first longitudinal portion may extend along a first longitudinal axis extending longitudinally through a center of the first longitudinal portion, and the second longitudinal portion may extend along a second longitudinal axis extending longitudinally through a center of the second longitudinal portion. The transition portion may be configured to transition from the first cross-section to the second cross-section such that the first longitudinal axis is offset relative to the second longitudinal axis. In at least some embodiments, a first outer surface of the first longitudinal portion may extend along a plane co-extending with a second outer surface of the second longitudinal portion.

Description

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 18 / 163,969, filed on February 3, 2023, which is incorporated herein by reference in its entirety. Technical Field

[0002] The present disclosure relates generally to medical devices for treating musculoskeletal conditions and, more particularly, to a spinal rod that provides stability while reducing stress on spinal components. Background Art

[0003] Spinal disorders (such as degenerative disc disease, herniated discs, osteoporosis, spondylolisthesis, stenosis, scoliosis and other curvature abnormalities, kyphosis, tumors, and fractures) can be caused by factors including trauma, disease, and degenerative conditions caused by injury and aging. Spinal disorders often result in symptoms including pain, nerve damage, and partial or complete loss of mobility.

[0004] Non-surgical treatments (such as medication, rehabilitation and exercise) may be effective, however, they may not alleviate the symptoms associated with these conditions. Surgical treatments for these spinal conditions include discectomy, laminectomy, fusion and implantable prostheses. As part of these surgical treatments, connecting elements (such as vertebral rods) are often used to provide stability to the treated area. During surgical treatment, one or more rods may be attached to the outside of two or more vertebral members.

[0005] When healing occurs, the longitudinal rod transfers stress from the damaged or defective area to restore correct alignment and generally support the vertebral member. In some applications, the longitudinal rod can be attached to the vertebral member via pedicle screws and / or tulip head connectors, without using implants or spinal fusion. When the longitudinal rod spans the cervical and thoracic vertebrae (e.g., the cervicothoracic junction at the C7 and T1 vertebrae), at least one problem that may occur in the related art may occur. Due to the different screw sizes for the cervical and thoracic vertebrae and the anatomical differences at the transition zone (i.e., the junction between the thoracic and cervical vertebrae), even after bending the longitudinal rod, it is usually impossible to optimally fix the pedicle screws to the longitudinal rod in the junction zone because the current longitudinal rod may be difficult to adjust to fully comply with the natural dorsal height difference between the vertebrae in the zone. This may lead to the situation of being referred to as "missed segments" in the art. In conventional applications, a special-shaped rod with a concentric center is used. Although such a special-shaped rod can provide an appropriate structure that is consistent with the natural spinal shape in other zones of the spine, a special-shaped rod with a concentric center may require the surgeon to skip placing screws at the cervicothoracic junction.

[0006] In another application, the surgeon can adopt two independent longitudinal rods, and these two independent longitudinal rods align at thoracic vertebra and cervical vertebra separately, and this thoracic vertebra and this cervical vertebra are engaged by connector at thoracic vertebra and cervical vertebra transition.This has introduced other problem (lack of flexibility such as whole longitudinal rod), and may not be able to connect longitudinal rod to the pedicle screw at cervical thoracic junction.Although existing spinal rod has attempted to provide effective spinal stabilization, still need a kind of longitudinal rod, this longitudinal rod provides stable support by allowing it to be connected to the pedicle screw at thoracic vertebra and cervical vertebra transition, keeps the flexibility of longitudinal rod in whole spine simultaneously.Therefore, need to provide a kind of solution, in this solution, longitudinal rod can effectively and more easily fix multiple vertebral segments and cross over wherein thoracic vertebra to become the transition zone of cervical vertebra and do not skip vertebral segments. Summary of the Invention

[0007] The technology disclosed herein generally relates to spinal rods having multiple sections (i.e., cross-sections) with eccentric centers. In various embodiments, these spinal rods can be broadly understood as multi-diameter rods having multiple sections with eccentric centers. The disclosed embodiments can be configured for use in spinal surgery, which allows surgeons to securely couple rods to corresponding vertebrae at the cervicothoracic junction of the human spine. Similarly, the disclosed embodiments can also be used in spinal surgery involving vertebrae spanning the lumbar-thoracic junction of the human spine.

[0008] In one aspect, the present disclosure provides a spinal rod for use in spinal surgery. In various embodiments, the spinal rod may include a first longitudinal portion extending along a first longitudinal axis and having a first cross-section and a first end portion, and the first longitudinal axis may extend longitudinally through the center of the first longitudinal portion. The example spinal rod may include a second longitudinal portion extending along a second longitudinal axis, having a second cross-section and a second end portion opposite the first end portion, and the second longitudinal axis may extend longitudinally through the center of the second longitudinal portion. The example spinal rod may include a transition portion adjacent to the first longitudinal portion and the second longitudinal portion, the transition portion being configured to transition from the first cross-section to the second cross-section such that the first longitudinal axis is offset relative to the second longitudinal axis. In at least some embodiments, a first outer surface of the first longitudinal portion extends from the first end portion and toward the second end portion along a plane that is coextensive with a second outer surface of the second longitudinal portion extending from the second end portion and toward the first end portion.

[0009] In another aspect, the present disclosure provides a method for treating multiple vertebral regions in a patient. In various embodiments, the method may include providing a spinal rod and then attaching the spinal rod to a first plurality of bone anchors (e.g., pedicle screws and / or lateral mass screws in the thoracic region of the spine) and a second plurality of bone anchors (e.g., pedicle screws or lateral mass screws in the cervical region of the spine). The exemplary method may include aligning the transition portion of the spinal rod over the cervicothoracic junction such that the first longitudinal portion spans and supports the thoracic region of the spine, and the second longitudinal portion spans and supports the cervical region of the spine.

[0010] In another aspect, the present disclosure provides a system comprising a spinal rod for use in spinal surgery. In various embodiments, the system may include: a first plurality of bone anchors (e.g., pedicle screws or lateral mass screws) configured for attachment to the cervical vertebrae; and a second plurality of bone anchors (e.g., pedicle screws) configured for attachment to the thoracic vertebrae. This exemplary spinal surgical system may include a first longitudinal portion of the spinal rod extending along a first longitudinal axis and having a first cross-section and a first end portion. In some embodiments, the first longitudinal axis may extend longitudinally through the center of the first longitudinal portion. In at least some embodiments, the spinal surgical system may include a second longitudinal portion extending along a second longitudinal axis and having a second cross-section and a second end portion. In various embodiments, the second longitudinal axis may extend longitudinally through the center of the second longitudinal portion. In at least some embodiments, the surgical system may include a transition portion adjoining the first longitudinal portion and the second longitudinal portion, the transition portion being configured to transition from the first cross-section to the second cross-section such that the first longitudinal axis is offset relative to the second longitudinal axis. In some embodiments, the first outer surface of the first longitudinal portion extending from the first end portion and toward the second end portion can extend along a plane coextensive with the second outer surface of the second longitudinal portion. In various embodiments, the second outer surface of the second longitudinal portion can extend from the second end portion and toward the first end portion. In at least some embodiments, the first longitudinal portion can be configured to be connected to the first plurality of pedicle screws, and the second longitudinal portion can be configured to be connected to the second plurality of pedicle screws or lateral mass screws such that each vertebra adjacent to the transition portion is connected to the spinal rod.

[0011] The details of one or more aspects of the present disclosure are set forth in the following drawings and the description. Other features, objects, and advantages of the technology described in this disclosure will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 A perspective view of a first embodiment of a spinal rod having an eccentric center is depicted.

[0013] Figure 2A Depicts Figure 1 A side view of the spinal rod is shown.

[0014] Figure 2B Depicts passing through Figure 1 A cross-sectional side view of the length of the spinal rod is shown.

[0015] Figure 3 Depicts Figure 1 A perspective view of a first end portion of a spinal rod is shown.

[0016] Figure 4 Depicts Figure 1 A perspective view of the second end portion of the spinal rod is shown.

[0017] Figure 5A Depicts Figure 1 A first perspective view of various planes of the spinal rod is shown.

[0018] Figure 5B Depicts Figure 1 A second perspective view of various planes of the spinal rod is shown.

[0019] Figure 6 Depicted is a perspective view of a second embodiment of a spinal rod according to the principles of the present disclosure.

[0020] Figure 7A Depicts Figure 6 A side view of the spinal rod is shown.

[0021] Figure 7B Depicts passing through Figure 6 A cross-sectional side view of the length of the spinal rod is shown.

[0022] Figure 8 Depicts Figure 6 A perspective end view of a first end portion of a spinal rod is shown.

[0023] Figure 9 Depicts Figure 6 A perspective end view of a second end portion of a spinal rod is shown.

[0024] Figure 10 Depicts Figure 6 A perspective view of the transition portion of the spinal rod is shown.

[0025] Figure 11 Depicts mounted spinal rods connected to the cervical and thoracic spine via multiple stabilizing pedicle screw assemblies of varying sizes.

[0026] Figure 12 Depicts Figure 11 An enlarged view of the cervicothoracic junction is shown.

[0027] Figure 13 Reference diagram depicting the various anatomical planes of the human body.

[0028] Figure 14 Reference diagram depicting the human spine. DETAILED DESCRIPTION

[0029] Embodiments of the present disclosure relate generally to, for example, spinal stabilization systems, and more particularly to surgical instruments for use with spinal stabilization systems. Embodiments of devices and methods are described below with reference to the accompanying drawings.

[0030] The following discussion omits or only briefly describes certain components, functionality, and functions associated with medical implants, installation tools, and related surgical techniques, which are apparent to those of ordinary skill in the art. It should be noted that various embodiments are described in detail with reference to the accompanying drawings, wherein similar reference numerals represent similar parts and components in several views, where possible. Reference to various embodiments does not limit the scope of the appended claims, as these embodiments are examples of the inventive concepts described herein. Additionally, any examples set forth in this specification are intended to be non-restrictive and only set forth some embodiments of the many possible embodiments applicable to the appended claims. In addition, unless the context or other statements clearly indicate otherwise, the specific features described herein may be used in combination with the features of the other descriptions in each of the various possible combinations and arrangements.

[0031] As used herein, terms such as "parallel," "transverse," "longitudinal," "axial," and the like are intended to encompass identical meanings while also including variations that may occur, for example, due to manufacturing processes. The term "substantially" may be used herein to emphasize this meaning, particularly when the embodiments being described have the same or nearly the same functionality or characteristics, unless the context or other statements clearly indicate otherwise. The term "about" may also be used herein to emphasize this meaning, and if values ​​and / or ranges of values ​​are provided in the specification or claims with the modifier "about," the meaning of "about" encompasses + / - ten percent (10%) of those provided values, unless the context clearly indicates otherwise.

[0032] Furthermore, as used in this specification and including the appended claims, "treating" a disease or condition refers to performing a procedure that may include administering one or more drugs to a patient (normal or abnormal human, or other mammal) in an attempt to alleviate the signs or symptoms of the disease or condition. Relief may occur before or after the signs or symptoms of the disease or condition appear. Thus, treatment includes preventing a disease or adverse condition (e.g., preventing the disease from occurring in a patient who may be susceptible to the disease but has not yet been diagnosed with the disease). In addition, treatment does not require complete relief of signs or symptoms, does not require a cure, and specifically includes procedures that have only a minimal effect on the patient. Treatment may include inhibiting the disease, such as stopping its progression, or alleviating the disease, such as causing it to regress. For example, treatment may include reducing acute or chronic inflammation; alleviating and relieving pain and promoting the regrowth of new ligaments, bone, and other tissues; serving as an adjunct to surgery; and / or any repair procedure. Furthermore, as used in the specification and the appended claims, the term "tissue" includes soft tissue, ligaments, tendons, cartilage, and / or bone, unless otherwise specifically indicated.

[0033] Furthermore, as used herein, it will be understood that the term "sagittal plane" includes any segmental plane in an anatomical position that passes generally vertically through a person in a prone position and is approximately perpendicular to both the coronal plane and the horizontal (or axial or transverse) plane (typically dividing the person into left and right segments), and also includes any segmental plane in an anatomical position that passes generally vertically through a person in a prone position, is approximately perpendicular to the horizontal (or axial or transverse) plane, and is typically angularly oriented from the coronal plane at an orientation angle ranging from greater than zero degrees up to and including ninety degrees.

[0034] For ease of description, spatially relative terms such as "below," "lower," "upper," "side," and "front" are used to explain the positioning of one element relative to a second element. These terms are intended to encompass different orientations of the device in addition to those depicted in the figures. Furthermore, terms such as "first" and "second" are also used to describe various elements, regions, sections, and portions and are not intended to be limiting. Throughout the specification, similar terms refer to similar elements.

[0035] As used herein, the terms "having," "containing," "including," and "comprising" are open-ended terms that indicate the presence of stated elements or features, but do not exclude additional elements or features. The singular forms "a," "an," and "the" are intended to include the plural as well as the singular, unless the context clearly indicates otherwise.

[0036] Before discussing the details of the relevant disclosed embodiments, it is helpful to briefly discuss the relevant human anatomy. Figure 13As depicted, the human spine is composed of a stack of 33 curved vertebrae that are structurally divided into five regions: the cervical region (C1-C7), the thoracic region (T1-T12), the lumbar region (L1-L5), and the fused sacrum and coccyx regions. Towards the bottom of the spine, the vertebrae are larger because the spine supports the heavier loads of the body in this region. The cervical vertebrae that form the neck region are relatively small to increase the flexibility of the head and because these cervical vertebrae support smaller loads relative to the thoracic and lumbar regions. Directly below the cervical vertebrae are the thoracic vertebrae, which form the upper back. The thoracic vertebrae are larger than the cervical vertebrae and increase in size from top to bottom. Below the thoracic region are the lumbar vertebrae, which are even larger and support the weight of the entire upper body. Relative motion in the spine can also vary along the length of the spine because the cervical vertebrae have a greater range of motion than the lower lumbar vertebrae.

[0037] like Figure 11 and Figure 12 As shown, due to the natural curvature of the spine, there is a dorsal height difference between the cervical and thoracic vertebrae, which forms the cervicothoracic junction at the transition between the C7 and T1 vertebrae. The disclosed embodiments are designed and / or optimized to ensure that the cervicothoracic junction can be properly supported by the longitudinal rod spanning at least a portion of the cervical and thoracic vertebrae.

[0038] The following discussion includes a description of exemplary methods of using multi-diameter rods or longitudinal rods and / or spinal rods with eccentric centers, related components, and spinal rods according to the principles of the present disclosure. Alternative embodiments are also disclosed. Reference will now be made in detail to exemplary embodiments of the present disclosure, which are illustrated in the accompanying drawings.

[0039] Various spinal rod embodiments disclosed herein may include a first elongated member portion and a second elongated member portion having an eccentric center that can be contoured to more closely resemble the natural structure of the curvature of the spine, for example, by having a smaller diameter portion oriented higher along the spine toward the cervical vertebrae. As briefly mentioned above, the disclosed multi-diameter eccentric rod embodiments can reduce the height of the smaller diameter member relative to the larger diameter member, thereby allowing for efficient multi-level procedures without skipping vertebral segments at the cervicothoracic junction.

[0040] Figures 1 to 10Various embodiments of multi-diameter rods 100, 101 with eccentric centers according to the principles of the present disclosure are illustrated. Like reference numerals indicate similar parts throughout the drawings. It should be understood that the drawings are not drawn to scale. Furthermore, the relationships between objects in the drawings may not be to scale and may actually have inverse relationships with respect to size. The drawings are intended to aid understanding and clarity of the structure of each illustrated object, and therefore, some features may be exaggerated to illustrate specific features of a structure.

[0041] The components of the disclosed embodiments can be made of bio-acceptable materials suitable for medical applications, including metals, synthetic polymers, ceramics, and bone materials and / or composites thereof. For example, individually or collectively, the components can be made of materials such as stainless steel alloys, commercially pure titanium, titanium alloys, grade 5 titanium, superelastic titanium alloys, cobalt-chromium alloys, superelastic metal alloys (e.g., nickel-titanium alloys, superelastic-plastic metals such as GUM, etc.). ), ceramics and their composites such as calcium phosphate (e.g., SKELITE TM ), thermoplastics (such as polyaryletherketone (PAEK) including polyetheretherketone (PEEK), polyetherketoneketone (PEKK) and polyetherketone (PEK)), carbon-PEEK composites, PEEK-BaSO4 polymer rubber, polyethylene terephthalate (PET), fabrics, silicone, polyurethane, silicone-polyurethane copolymers, polymer rubber, polyolefin rubber, hydrogels, semi-rigid and rigid materials, elastomers, rubber, thermoplastic elastomers, thermosetting elastomers, elastomeric composites, rigid polymers including polyphenylene, polyamide, polyimide, polyetherimide, polyethylene, epoxy resin, and combinations thereof.

[0042] In various embodiments, the disclosed multi-diameter rods 100, 101 can be formed by a metal material (e.g., a titanium alloy). In some embodiments, the multi-diameter rods can be formed by two or more materials. In one embodiment, the slender rod portion can be made of carbon-reinforced PEEK, and the middle section can be made of PEEK. In another embodiment, the slender rod portion can be made of PEEK, and the middle section can be made of carbon-reinforced PEEK. It is envisioned that the longitudinal rod or device can be manufactured via various methods, including machining, casting, injection molding, insert molding, overmolding, compression molding, transfer molding, co-extrusion, pultrusion, dip coating, spray coating, powder coating, porous coating, additive manufacturing, and combinations thereof. However, those skilled in the art will recognize that, according to the present disclosure, such materials and manufacturing methods suitable for assembly and manufacture will be appropriate.

[0043] refer to Figure 15 , a multi-diameter rod 100 with an eccentric center is configured for attachment to vertebrae during surgical treatment of spinal conditions, examples of which are discussed herein. In various embodiments, the multi-diameter rod 100 can include a first longitudinal member portion 105 having a first end portion 106, a second longitudinal member portion 110 having a second end portion 111 opposite the first end portion 106, and a transition portion 115 disposed therebetween. The transition portion 115 can join the first longitudinal member portion 105 to the second longitudinal member portion 110. In various embodiments, the first longitudinal member portion 105, the transition portion 115, and the second longitudinal member portion 110 can be integrally formed as a single, unitary component or unitary part, for example, by a subtractive manufacturing process or a casting and molding process, or by welding the parts together. A first longitudinal axis A1 is defined between the first end portion 106 and the transition portion 115, and a second longitudinal axis A2 is defined between the second end portion 111 and the transition portion 115. In the illustrated embodiment, the longitudinal axis A1 extends lengthwise through the center of the first longitudinal member portion 105 , and the longitudinal axis A2 extends lengthwise through the center of the second longitudinal member portion 110 .

[0044] The length dimensions of the first longitudinal member portion and the second longitudinal member portion of the multi-diameter rod can be optimized based on the intended surgical application and / or the practitioner's preferences. It should be understood that the practitioner can cut the multi-diameter rod into appropriate lengths based on the patient's needs. In various embodiments, the length of the first longitudinal member portion 105 along axis A1 can be between about 270 mm and about 360 mm. In various embodiments, the length of the second longitudinal member portion 110 along axis A2 can be between about 150 mm and about 240 mm. In various embodiments, the length ratio between the first longitudinal member portion 105 and the second longitudinal member portion 110 can be between about 1.125 and about 2.4. In some embodiments, the first longitudinal member portion 105 can be bent to more naturally follow the curvature of the human thoracic spine, while the second longitudinal member portion 110 can be bent to more naturally follow the curvature of the human cervical spine.

[0045] The first end portion 106 may have a generally circular, oval, and / or elliptical geometry. In some embodiments, the shape may be generally cylindrical while also having flat side surfaces, such as, for example, an elongated shape similar to a pentagonal and / or hexagonal cross-section. In these embodiments, the diameter, major diameter, and / or minor diameter may be understood as approximations based on, for example, an imaginary circular and / or oval-like shape that is surrounded and contacted by portions of the perimeter of the elongated shape's cross-section. Many shapes are contemplated and disclosed herein (e.g., oval shapes, elliptical shapes, D-shaped shapes, and / or rectangular shapes) that may include a major diameter and a minor diameter, depending on the particular shape. As Figure 3 As illustrated, the first end portion 106 can include a circular shape, an oval shape, and / or a cylindrical shape that generally represents and / or corresponds to the cross-sectional shape of the first longitudinal member portion 105. For example, the shape of the first end portion 106 can correspond 1:1 with the cross-section of the first longitudinal member portion 105. During use and / or installation, the first end portion can include a first major diameter 102 that is parallel to the sagittal plane of the patient's body when viewed in a cross-sectional view (see FIG. Figure 14 As illustrated, the first end portion 106 further includes a first minor diameter 104 that extends transversely to the major diameter 102 and parallel to the transverse plane of the patient's body.

[0046] In various embodiments, the major diameter 102 of the oval-shaped first end portion 106 can comprise any desired size, depending on the intended surgical application. In various embodiments, the major diameter 102 of the first end portion 106 can be between about 4.75 mm and about 6.35 mm. In various embodiments, the ratio between the major diameter 102 and the minor diameter 104 can be between about 1 and about 1.3.

[0047] The second end portion 111 can have a generally circular, oval, and / or cylindrical geometry. In some embodiments, the shape can be generally cylindrical while also having flat side surfaces, such as, for example, an elongated shape similar to a pentagonal and / or hexagonal cross-section. Many shapes are contemplated and disclosed herein (e.g., an oval shape, an elliptical shape, and / or a rectangular shape) that can include a second major diameter and a second minor diameter, depending on the particular shape. Figure 4As illustrated, the second end portion 111 can include a circular shape, an oval shape, and / or a cylindrical shape that generally represents the cross-sectional shape of the second longitudinal member portion 110. During use and / or installation, when viewed in a cross-sectional view, the second end portion can have a second major diameter 112 that is parallel to the sagittal plane of the patient's body. The second end portion 111 can also include a second minor diameter 114 that extends transversely to the major diameter 112 and parallel to the transverse plane of the patient's body.

[0048] In various embodiments, the major diameter 112 of the oval-shaped second end portion 111 can comprise any desired size, depending on the intended surgical application. In various embodiments, the major diameter 112 of the second end portion 112 can be between about 3 mm and about 4 mm. In various embodiments, the ratio between the major diameter 112 and the minor diameter 114 can be between about 1 and about 1.33.

[0049] like Figure 5A and Figure 5B As shown, the longitudinal axes A1 and A2 of the first longitudinal member portion 105 and the second longitudinal member portion 110 are eccentric, that is, they are not aligned and / or they are in a non-coaxial orientation relative to each other. Additionally, in various embodiments, there may be an offset surface plane P1 and a coextensive surface plane P2, at which offset surface plane P1 there is a height difference (e.g., gap distance 103) between the two members, and at which coextensive surface plane P2 there is no height change (no relative gap distance) along the outer surfaces of the first longitudinal member portion 105 and the second longitudinal member portion 110. In an exemplary embodiment, gap distance 103 can be attributed to the slope and length of transition portion 115. The size range of gap space 103 in a plane parallel to the face of first end portion 106 can be about 0.75 mm to about 3.35 mm. In an exemplary embodiment, surface plane P2 can be understood as a plane extending along the outermost surface of the first longitudinal member 105 and the outermost surface of the second longitudinal member 110 and / or intersecting with the outermost surface of the first longitudinal member and the outermost surface of the second longitudinal member. For example, plane P2 may be the only plane that can be drawn along the length of longitudinal rod 100 that contacts both the outermost surface of first longitudinal member portion 105 and the outermost surface of second longitudinal member portion 110 .

[0050] Overall reference Figures 6 to 10, discloses a second embodiment of a multi-diameter rod 101 having an eccentric center. Multi-diameter rod 101 may have the same, similar, and / or substantially the same features and functionality as described above with respect to rod 100. Therefore, repeated description will be omitted. In this embodiment, first end portion 106 and second end portion 111 may have a circular shape. In various embodiments, the shape of first end portion 106 may define and / or represent a cross-sectional view of first longitudinal member portion 105, and the shape of second end portion 111 may define and / or represent a cross-sectional view of second longitudinal member portion 110. In the disclosed embodiment, the cross-sectional dimension (thickness) of first longitudinal member portion 105 remains consistent throughout its length, and the cross-sectional dimension (thickness) of second longitudinal member portion 110 remains consistent throughout its length. In this manner, first member 105 may have a first, consistent cross-section, and second member 110 may have a second, consistent cross-section. Additionally, transition portion 115 may be understood as the region of longitudinal rod 101 where the first cross-section transitions to the second cross-section.

[0051] In various embodiments, the major diameter 112 of the second end portion 111 can have a number of sizes, depending on the intended surgical application. In some embodiments, the cross-sections of both the first end portion 106 and the second end portion 111 can include a circular shape, such as Figures 6 to 10 As depicted in the illustrated multi-diameter rod embodiment 101. In an exemplary embodiment, the cross-sections of the first end portion 106 and the second end portion 111 may be shaped similar to a perfect circle, for example, a uniform cross-sectional shape similar to a perfect circle. In some embodiments, the diameter and / or cross-sectional shape of the first end portion 106 may be approximately 4.75 mm to approximately 6.35 mm. In various embodiments, the diameter of the second end portion 111, which may be similar to a perfect circle (for example, a uniform cross-sectional shape similar to a perfect circle), may be approximately 3 mm to approximately 4 mm.

[0052] In various embodiments, it is desirable that the multi-diameter rods 100, 101 with eccentric centers exhibit variable major and minor diameters along the cross-section of the first longitudinal member portion 105 and the second longitudinal member portion 110, depending on the degree of curvature of the spine. In some embodiments, the first longitudinal member portion 105 can have a uniform cross-section throughout its entire length, as shown by the first end portion 106. In various embodiments, the second longitudinal member portion 110 can have a uniform cross-section throughout its entire length, as shown by the second end portion 111. Thus, the major diameter 112 and minor diameter 114 of the cross-section of the second longitudinal member portion 110 can be optimized based on the dorsal height difference of the spine.

[0053] While some embodiments may include increasing the major diameter 112 and the minor diameter 114, other embodiments may reduce the major diameter 112 and the minor diameter 114 to match (i) the contours of a particular patient's spine (e.g., differences between adult patients and pediatric patients) and / or (ii) the extent of spinal deformity / injury. In such embodiments, the oval-shaped cross-section of the second longitudinal member portion 110 may be used to provide more or less flexibility or to reduce excess material and weight.

[0054] In some embodiments, depending on the intended surgical application, multiple lengths can be envisioned at the transition portion 115 where the first longitudinal member portion 105 ends and the second longitudinal member portion 110 begins. In some embodiments, when the dorsal height difference is large, the transition portion 115 can be reduced to allow for a quick transition between the longitudinal member portions. In some embodiments, when the dorsal height difference is small, the transition portion 115 can be extended to provide a more gradual offset. In some embodiments, the length of the transition portion 115 can be between about 3 mm and about 5 mm, between about 5 mm and about 10 mm, or between about 10 mm and 20 mm. In some embodiments, the ratio of the length of the first longitudinal member portion 105 to the length of the transition portion 115 can be between about 54 and 120. In some embodiments, the ratio of the length of the second longitudinal member portion 110 to the length of the transition portion 115 can be between about 30 and about 80.

[0055] The multi-diameter rods 100, 101 described herein can be used with various bone anchors to secure the multi-diameter rods 100, 101 to the bony anatomy of a patient, for example, the pedicle portions of the vertebrae of the human spine. As used herein, the term "bone anchor" should broadly encompass any medically acceptable bone anchor that can be used in spinal surgery, such as, for example, a bone screw, a pedicle screw, a multi-axial screw (MAS), a lateral mass screw, etc. For example, the multi-diameter rods can be used in a multi-level procedure in which multiple pedicle screws or lateral mass screws are attached to each of the vertebrae C3 to T4, and the multi-diameter rods can be used as described herein. Figure 11 and Figure 12 For example, and in part due to the coextensive surface plane P2 provided by the eccentric centers of the multi-diameter rods 100, 101, the height difference of the second longitudinal member portion 110 relative to the first longitudinal member portion 105 at the transition portion 115 allows the screw to be stabilized to be secured to each vertebra of a multi-level protocol without skipping a level.

[0056] In some embodiments, it is envisioned that the multi-diameter rods 100, 101 can be used with pedicle screws having an osteoconductive surface treatment or coated with an osteoconductive material, such as hydroxyapatite and / or an osteoinductive agent, such as bone morphogenetic protein for enhancing bone fixation to promote movement of the treated spinal region. The multi-diameter rods 100, 101 with eccentric centers can be made of radiolucent materials (such as polymers). Radioactive markers can be included for identification under x-ray, fluoroscopy, CT or other imaging techniques. Metal or ceramic radioactive markers (such as tantalum beads, tantalum pins, titanium pins, titanium end caps and platinum wires) can be used, such as provided at the end portions of the longitudinal rods and / or along their lengths.

[0057] In various embodiments, the multi-diameter rods 100, 101 may include markings and / or colors that allow a surgeon to easily identify the oval-shaped first end and the elliptical or non-oval-shaped second end to facilitate implantation of the longitudinal rods in the body.

[0058] In various embodiments, the first longitudinal member portion 105, the second longitudinal member portion 110, and the transition portion 115 may include an outer surface (not shown) that may include various surface treatments, such as texturing, shot peening, polishing, porosity, patterning, or corrugation. In other embodiments, the treated surface may also include a coating. The outer surface may be chemically treated or modified using various processes or materials, including oxidation, anodizing, plasma treatment, vapor deposition, electroplating, coating, or etching. It is contemplated that the spinal rod may comprise a heterogeneous composite material having a non-uniform carbon content.

[0059] To increase the estimated service life of the elongated member, the outer surface can be treated to maintain fatigue resistance. For example, the outer surface can be work-hardened by shot peening and then coated with an osseointegrative material, as described in more detail in U.S. Patent Publication No. US2008 / 0221681, which is incorporated herein by reference as if fully set forth herein.

[0060] In some embodiments, the outer layer of the first longitudinal member portion 105, the second longitudinal member portion 110, and the transition portion 115 may include (not shown) a roughened surface and a coating of an osseointegrative material disposed on the roughened surface. The surface texture on the outer layer of the elongated member can improve the adhesion of the coating to the surface of the elongated member. The coating not only increases the osseointegration of the elongated member implant, but also increases fatigue resistance.

[0061] In some embodiments, the osseointegrative coating can be osteoconductive or osteoinductive or both.The osseointegrative material in the coating can be heterogeneous in some cases and homogeneous in other cases.

[0062] For example, in addition to or instead of using HA (hydroxyapatite) as an osteoconductive coating, other exemplary osteoconductive coatings may include one or more of the following: biocompatible ceramics; calcium sulfate; calcium phosphate, such as HA, coralline hydroxyapatite, biphasic calcium phosphate, tricalcium phosphate, or fluorapatite; mineralized collagen; bioactive glass; porous metal; bone particles; and demineralized bone matrix (DBM).

[0063] The osteoinductive coating may comprise: other forms of bone morphogenetic proteins (BMPs), such as BMP-2, BMP-4, BMP-7, rhBMP-2, or rhBMP-7; demineralized bone matrix (DBM); transforming growth factor (TGF, e.g., TGF-β); osteoblasts; growth and differentiation factors (GDFs); insulin-like growth factor 1, platelet-derived growth factor, fibroblast growth factor, or any combination thereof.

[0064] In another example, the osteoinductive coating material may comprise an HMG-CoA reductase inhibitor, such as a member of the statin family, such as lovastatin, simvastatin, pravastatin, fluvastatin, atorvastatin, cerivastatin, mevastatin, a pharmaceutically acceptable salt, ester or lactone thereof, or any combination thereof. For lovastatin, the substance may be in the acid form or the lactone form, or a combination of both.

[0065] In yet another example, the osteoinductive material may comprise LIM mineralization protein (LMP), an osteoinductive peptide, a pharmaceutical agent (such as an antibiotic), an analgesic, an anti-inflammatory drug, a steroid, an osteogenic composition (such as a therapeutic agent or an anti-infective agent), or a combination of one or more of the foregoing.

[0066] In some embodiments, the osseointegration coating material may include a multifunctional polymeric material that inhibits adhesion and immune recognition between cells and tissues. These materials may include a tissue-binding component and a tissue-nonbinding component. Specific materials may include a PEG / PLL copolymer having a molecular weight greater than 300, and the PEG / PLL copolymer may have a structure including an AB copolymer, an ABA copolymer, and a brush copolymer.

[0067] Additionally, osseointegrative coatings may utilize grafted polyionic copolymers that are capable of attaching to biological and non-biological samples to control cell-surface interactions, cell-cell interactions, and tissue-surface interactions. Coatings may also include the use of polyionic, PEG-grafted copolymers.

[0068] In one embodiment, the osseointegration coating may include a grafted non-interactive material within a polymer, such as PEG (polyethylene glycol) or PEO (polyethylene oxide). Another example coating may be a combination polymer comprising a PEG-grafted poly(amino acid) having a polycationic backbone made of lysine, histidine, arginine, or ornithine in the D-, L-, or DL-configuration; or a PEG-grafted polymer having a cationic backbone of a polysaccharide such as chitosan, partially deacetylated chitosan, and an amine-containing derivative of a neutral polysaccharide; or a PEG-grafted non-peptide polyamine having a polycationic backbone such as poly(aminostyrene), poly(aminoacrylate), poly(N-methylaminoacrylate), poly(N-ethylaminoacrylate), poly(N,N-dimethylaminoacrylate), poly( N,N-diethylaminoacrylate), poly(amino methacrylate), poly(N-methylamino methacrylate), poly(N-ethylamino methacrylate), poly(N,N-dimethylamino methacrylate), poly(N,N-diethylamino methacrylate), poly(ethyleneimine), a polymer of a quaternary amine (such as poly(N,N,N-trimethylaminoacrylate chloride), poly(methacrylamidopropyltrimethylammonium chloride)); or the polymer is a PEG-grafted charged synthetic polymer with a polycationic backbone, such as polyethyleneimine, polyamino(meth)acrylate, polyaminostyrene, polyaminoethylene, poly(aminoethyl)ethylene, polyaminoethylstyrene, and N-alkyl derivatives thereof.

[0069] Other embodiments include one or more coatings of copolymers including PEG-grafted copolymers having an anionic backbone of poly(amino acids) grafted with poly(ethylene glycol), wherein the amino acids contain additional pendant carboxyl groups that impart a negative charge to the backbone at pH above 4 and particularly at neutral pH, such as polyaspartic acid or polyglutamic acid; or natural or non-natural polymers having pendant negatively charged groups, particularly carboxylate groups, including alginates, carrageenans, furcellaran, pectin, xanthan gum, hyaluronic acid, heparin, heparan sulfate, chondroitin sulfate, dermatan sulfate, dextran sulfate, poly(meth)acrylic acid, oxidized cellulose, carboxymethylcellulose and crosmarmelose, synthetic polymers and copolymers containing pendant carboxyl groups (such as those containing maleic acid or fumaric acid in the backbone).

[0070] In another embodiment, the osseointegration coating may include nanoparticles having a diameter of less than 500 nm. Nanoparticles are used to reduce protein "denaturation" and subsequent foreign body reactions. Nanoparticles may include metal particles, carbon particles, inorganic chemical particles, organic chemical particles, ceramic particles, graphite particles, polymer particles, protein particles, peptide particles, DNA particles, RNA particles, bacteria / virus particles, hydrogel particles, liquid particles or porous particles. Therefore, nanoparticles can be, for example, metals, carbon, graphite, polymers, proteins, peptides, DNA / RNA, microorganisms (bacteria and viruses) and polyelectrolytes. Polymers may include copolymers of water-soluble polymers (including but not limited to dextran, derivatives of polymethacrylamide, PEG, maleic acid, malic acid and maleic anhydride), and may include these polymers and suitable coupling agents (including 1-ethyl-3 (3-dimethylaminopropyl)-carbodiimide, also known as carbodiimide). Polymers may be degradable or non-degradable, or may be polyelectrolyte materials. As an example, the degradable polymer material includes poly-L-glycolic acid (PLGA), poly-DL-glycolic acid, poly-L-lactic acid (PLLA), PLLA-PLGA copolymer, poly(DL-lactide)-block-methoxypolyethylene glycol, polycaprolactone, poly(caprolactone)-block-methoxypolyethylene glycol (PCL-MePeg), poly(DL-lactide-co-caprolactone)-block-methoxypolyethylene glycol (PDLLACL-MePEG), certain polysaccharides (e.g., hyaluronic acid, polysaccharide, chitosan), proteins (e.g., fibrinogen, albumin, collagen, extracellular matrix), peptides (e.g., RGD, polyhistidine), nucleic acids (e.g., RNA, DNA, single-stranded or double-stranded), viruses, bacteria, cells and cell fragments, organic materials or carbon-containing materials. Non-degradable materials include natural or synthetic polymeric materials (e.g., polystyrene, polypropylene, polyethylene terephthalate, polyester polyurethane, polyvinyl chloride, silica, polydimethylsiloxane, acrylates, acrylamides, poly(vinylpyridine), polyacroleine, polyglutaraldehyde), some polysaccharides (e.g., hydroxypropyl cellulose, cellulose derivatives, dextran, glucose, sucrose, FICOLL, PERCOLL, arabinogalactan, starch) and hydrogels (e.g., polyethylene glycol, ethylene vinyl acetate, N-isopropylacrylamide, polyamines, polyethyleneimine, polyaluminum chloride).

[0071] Movement of components of the multi-diameter rod between one and multiple orientations is contemplated and may include a range of increasing and decreasing levels of resistance of the components of the multi-diameter rod.

[0072] In assembly, operation, and use, the multi-diameter rod is employed in conjunction with a surgical procedure for treating spinal disorders affecting a segment of a patient's spine, as discussed herein. The multi-diameter rod may also be employed in conjunction with other surgical procedures. Specifically, the multi-diameter rod is employed in conjunction with a surgical procedure for treating a condition or injury to an affected segment of the spine to provide stability for healing and therapeutic treatment while allowing a desired range of motion or load-sharing capability.

[0073] In use, in order to treat the affected section of the spine, the practitioner enters the surgical site including vertebra V in any appropriate manner (such as by cutting and retracting tissue). It is envisioned that the multi-diameter rod can be used for any existing surgical method or technology, including open surgery, micro-open surgery, minimally invasive surgery and percutaneous surgery, thereby entering vertebra V through a micro-incision or a sleeve providing a protected channel to the area. Once the surgical site is entered, the specific surgical procedure for treating spinal disorders is performed. The multi-diameter rod is then used to enhance surgical treatment. The multi-diameter rod can be delivered or implanted as a preassembled device, or can be assembled in situ. The multi-diameter rod can be modified, removed or replaced in whole or in part.

[0074] refer to Figure 11 and Figure 12 With reference to the installation shown, a method of installation will now be disclosed. In use, a surgeon may install a multi-diameter rod 100, 101 having an eccentric center in a patient requiring surgical treatment. For example, the surgeon may use any relevant embodiment of the principles of the disclosed multi-diameter rods 100, 101. The method may include the steps of installing a first plurality of bone anchors (e.g., pedicle screws 205), each of which includes a connector portion for securing a longitudinal rod (e.g., multi-diameter rods 100, 101) therein. The first plurality of pedicle screws 205 may be installed along a first plurality of corresponding vertebrae in the thoracic region of the spine along the first longitudinal member portion 105. The method may also include installing a second plurality of bone anchors (e.g., pedicle screws or lateral mass screws 210), each of which includes a connector portion for securing a longitudinal rod (e.g., multi-diameter rods 100, 101) therein. The second plurality of pedicle screws or lateral mass screws 210 may be installed along a second plurality of corresponding vertebrae in the cervical region of the spine along the second longitudinal member portion 110. As Figure 11 and Figure 12 As shown, the first plurality of pedicle screws 205 installed in the thoracic vertebrae are relatively larger than the second plurality of pedicle screws or lateral mass screws 210 installed in the cervical vertebrae. This procedure may take into account the relatively larger size of the vertebrae in the thoracic region compared to the vertebrae in the cervical region of the spine. Figure 12, which is best shown in an enlarged view of FIG, shows that the multi-diameter rods 100, 101 with eccentric centers can allow the surgeon to connect each vertebra without skipping a level. For example, each vertebra in the cervicothoracic transition region of the spine is connected to the multi-diameter rods 100, 101 with eccentric centers.

[0075] As used herein, the term "about" may be used to modify any quantitative representation that can be permitted to vary without resulting in a change in the basic function to which it is related. For example, the first end portion 106 having a first major diameter 102 as disclosed herein can be permitted to have varying diameters within the scope of the present invention without materially affecting the function of the spinal rod.

[0076] It should be understood that the various aspects disclosed herein may be combined in combinations different from those specifically presented in the description and drawings. For example, unless the context clearly indicates otherwise, features, functionality, and components from one embodiment may be combined with another embodiment, and vice versa. Similarly, unless the context clearly indicates otherwise, features, functionality, and components may be omitted. It should also be understood that, depending on the example, certain actions or events of any of the processes or methods described herein may be performed in a different order, may be added, merged, or omitted entirely (e.g., not all described actions or events may be required to perform these techniques).

[0077] Unless otherwise specifically defined herein, all terms should be given their broadest possible interpretation, including the meaning implicit from the specification and the meaning understood by those skilled in the art and / or the meaning as defined in dictionaries, treatises, etc. It must also be noted that, unless otherwise indicated, the singular forms "a", "an", and "the" used in the specification and the appended claims include plural referents, and the terms "comprising" and / or "including" when used in this specification specify the presence of stated features, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

Claims

1. A spinal rod having a plurality of segments with eccentric centers, the spinal rod comprising: a first longitudinal portion extending along a first longitudinal axis and having a first cross-section and a first end portion, the first longitudinal axis extending longitudinally through a center of the first longitudinal portion; a second longitudinal portion extending along a second longitudinal axis, having a second cross-section and a second end portion opposite the first end portion, the second longitudinal axis extending longitudinally through a center of the second longitudinal portion; and a transition portion adjoining the first longitudinal portion and the second longitudinal portion, the transition portion being configured to transition from the first cross-section to the second cross-section, wherein the first longitudinal axis is offset relative to the second longitudinal axis, and wherein a first outer surface of the first longitudinal portion extending from the first end portion and toward the second end portion extends along a plane that is coextensive with a second outer surface of the second longitudinal portion extending from the second end portion and toward the first end portion.

2. The spinal rod of claim 1, wherein the spinal rod is a unitary component.

3. The spinal rod of claim 1, wherein the first cross-section of the first longitudinal portion comprises an oval shape having a major diameter and a minor diameter.

4. The spinal rod of claim 3, wherein the second cross-section of the second longitudinal portion comprises an oval shape having a major diameter and a minor diameter.

5. The spinal rod of claim 1, wherein the first cross-section of the first longitudinal portion comprises a circular shape having a uniform diameter.

6. The spinal rod of claim 5, wherein the second cross-section of the second longitudinal portion comprises a circular shape having a uniform diameter.

7. The spinal rod of claim 1, wherein the transition portion extends in the longitudinal direction a distance in the range of about 3 mm to about 5 mm.

8. The spinal rod of claim 1, wherein the length of the first longitudinal portion is between about 270 mm and about 360 mm.

9. The spinal rod of claim 8, wherein the length of the second longitudinal portion is between about 150 mm and about 240 mm.

10. The spinal rod of claim 1 , wherein: The first longitudinal portion extends a first distance along the first longitudinal axis, and the second longitudinal portion extends a second distance along the second longitudinal axis, and A ratio of the first distance to the second distance is in a range of approximately 1.125 to 2.

4.

11. The spinal rod of claim 1 , wherein a major diameter of the first cross-section of the first longitudinal portion is between about 4.75 mm and about 6.35 mm.

12. The spinal rod of claim 11, wherein the major diameter of the second cross-section of the second longitudinal portion is between about 3 mm and about 4 mm.

13. The spinal rod of claim 11, wherein the minor diameter of the first cross-section of the first longitudinal portion is between about 4.75 mm and about 6.35 mm.

14. The spinal rod of claim 13, wherein the minor diameter of the second cross-section of the first longitudinal portion is between about 3 mm and about 4 mm.

15. The spinal rod of claim 1 , wherein: the first cross-section of the first longitudinal portion comprising a first major diameter and a first minor diameter; the second cross-section of the second longitudinal portion comprising a second major diameter and a second minor diameter; a ratio of the first major diameter to the first minor diameter in a range from about 1 to about 1.3; a ratio of the second major diameter to the second minor diameter in a range from 1 to about 1.33; a ratio of the first major diameter to the second major diameter in a range from about 1.18 to about 2.2; and A ratio of the first minor diameter to the second minor diameter is in a range of approximately 1.18 to 2.

2.

16. The spinal rod of claim 1, wherein at least one of the first longitudinal section and / or the second longitudinal section comprises an osteoconductive surface treatment, an osteoconductive coating, an osteoinductive coating, or a mixture thereof.

17. The spinal rod of claim 1, wherein the first longitudinal portion and the second longitudinal portion are separable components configured to abut one another.

18. A method for treating multiple vertebral regions in a patient, the method comprising: Providing a spinal rod according to claim 1; attaching the spinal rod to a first plurality of bone anchors in a thoracic region of the spine and a second plurality of bone anchors in a cervical region of the spine; as well as The transition portion of the spinal rod is aligned over the cervicothoracic junction such that the first longitudinal portion spans and supports the thoracic region of the spine and the second longitudinal portion spans and supports the cervical region of the spine.

19. A system comprising a spinal rod having a plurality of segments with eccentric centers, the system comprising: a first plurality of bone anchors configured for attachment to a cervical vertebra; a second plurality of bone anchors configured for attachment to a thoracic spine; a first longitudinal portion extending along a first longitudinal axis and having a first cross-section and a first end portion, the first longitudinal axis extending longitudinally through a center of the first longitudinal portion; a second longitudinal portion extending along a second longitudinal axis, having a second cross-section and a second end portion opposite the first end portion, the second longitudinal axis extending longitudinally through a center of the second longitudinal portion; and a transition portion adjoining the first longitudinal portion and the second longitudinal portion, the transition portion being configured to transition from the first cross-section to the second cross-section, wherein the first longitudinal axis is offset relative to the second longitudinal axis, wherein a first outer surface of the first longitudinal portion extending from the first end portion and toward the second end portion extends along a plane coextensive with a second outer surface of the second longitudinal portion extending from the second end portion and toward the first end portion, and Wherein the first longitudinal portion is configured to be connected to the first plurality of bone anchors and the second longitudinal portion is configured to be connected to the second plurality of bone anchors such that each vertebra adjacent the transition portion is connected to the spinal rod.

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