Patent Application
20100114165
This disclosure relates generally to spinal stabilization systems, and more particularly to spinal implants for dynamically stabilizing human spines. Even more particularly, this disclosure relates to embodiments of a pivoting collar and a posterior dynamic stabilization system utilizing the same.
The human spine consists of segments known as vertebrae separated by intervertebral disks 28 and held together by various ligaments. There are 24 movable vertebrae—7 cervical, 12 thoracic, and 5 lumbar. Each of the movable vertebrae has a somewhat cylindrical bony body (often referred to as the centrum), a number of winglike projections, and a bony arch. The bodies of the vertebrae form the supporting column of the skeleton. The arches of the vertebrae are positioned so that the spaces they enclose form a curvilinear passage which is often referred to as the vertebral canal. The vertebral canal houses and protects the spinal cord (which includes bundles of sensory and motor nerves for sensing conditions in or affecting the body and commanding movements of various muscles). Within the vertebral canal, spinal fluid can circulate to cushion the spinal cord and carry immunological cells to it, thereby protecting the sensory and motors nerves therein from mechanical damage and disease. Ligaments and muscles are attached to various projections of the vertebrae such as the superior-inferior, transverse, and spinal processes. Other projections, such as vertebral facets, join adjacent vertebrae to each other, in conjunction with various attached muscles, tendons, etc. while still allowing the vertebrae to move relative to each other.
Spines may be subject to abnormal curvature, injury, infections, tumor formation, arthritic disorders, punctures of the intervertebral disks, slippage of the intervertebral disks from between the vertebrae, or combinations thereof. Injury or illness, such as spinal stenosis and prolapsed disks may result in intervertebral disks having a reduced disk height, which may lead to pain, loss of functionality, reduced range of motion, disfigurement, and the like. Scoliosis is one relatively common disease which affects the spinal column. It involves moderate to severe lateral curvature of the spine and, if not treated, may lead to serious deformities later in life. Such deformities can cause discomfort and pain to the person affected by the deformity. In some cases, various deformities can interfere with normal bodily functions. For instance, some spinal deformities can cause the affected person's rib cage to interfere with movements of the respiratory diaphragm, thereby making respiration difficult. Additionally, some spinal deformities noticeably alter the posture, gate, appearance, etc. of the affected person, thereby causing both discomfort and embarrassment to those so affected. One treatment involves surgically implanting devices to correct such deformities, to prevent further degradation, and to mitigate symptoms associated with the conditions which may be affecting the spine.
Modern spine surgery often involves spinal stabilization through the use of spinal implants or stabilization systems to correct or treat various spine disorders and/or to support the spine. Spinal implants may help, for example, to stabilize the spine, correct deformities of the spine, facilitate fusion of vertebrae, or treat spinal fractures and other spinal injuries. Spinal implants can alleviate much of the discomfort, pain, physiological difficulties, embarrassment, etc. that may be associated with spinal deformities, diseases, injury, etc.
Spinal stabilization systems typically include corrective spinal instrumentation that is attached to selected vertebra of the spine by bone anchors, screws, hooks, clamps, and other implants hereinafter referred to as “bone anchors.” Some corrective spinal instrumentation includes spinal stabilization rods, spinal stabilization plates that are generally parallel to the patient's back, or combinations thereof. In some situations, corrective spinal instrumentation may also include superior-inferior connecting rods that extend between bone anchors (or other attachment instrumentation) attached to various vertebrae along the affected portion of the spine and, in some situations, adjacent vertebrae or adjacent boney structures (for instance, the occipital bone of the cranium or the coccyx). Spinal stabilization systems can be used to correct problems in the cervical, thoracic, and lumbar portions of the spine, and are often installed posterior to the spine on opposite sides of the spinous process and adjacent to the superior-inferior process. Some implants can be implanted anterior to the spine and some implants can be implanted at other locations as selected by surgical personnel such as at posterior locations on the vertebra.
Often, spinal stabilization may include rigid support for the affected regions of the spine. Such systems can limit movement in the affected regions in virtually all directions. Such spinal stabilizations are often referred to as “static” stabilization systems and can be used in conjunction with techniques intended to promote fusion of adjacent vertebrae in which the boney tissue of the vertebrae grow together, merge, and assist with immobilizing one or more intervertebral joints. More recently, so called “dynamic” spinal stabilization systems have been introduced wherein the implants allow at least some movement (e.g., flexion or extension) of the affected regions of the spine in at least some directions.
Dynamic stabilization systems therefore allow the patient greater freedom of motion at the treated intervertebral joint(s) and, in some cases, improved quality of life over that offered by static stabilization systems.
In one embodiment, a system for dynamically stabilizing a portion of a spine is provided. The system can include a spinal stabilization rod and a collar which can be attached to one of the vertebrae of the spine. The collar can define a bore, an internal surface of the bore, and a contact point on the internal surface. The bore can be shaped and dimensioned to accept the spinal stabilization rod and to allow the spinal stabilization rod to pivot about the contact point. In some embodiments, the spinal stabilization rod can be flexible so that it can bend about the contact point.
Regarding the bore, various embodiments include internal surfaces of differing shapes including, in some embodiments, generally semi-spherical internal surfaces. The internal surface can be further shaped and configured to limit the range through which the spinal stabilization rod pivots. For instance, the internal surface can limit the spinal stabilization rod to a range of about six degrees in any direction. In some embodiments, the range through which the spinal stabilization rod can pivot can differ for differing directions. In some embodiments, at least a portion of the bore can have an oval cross sectional shape.
In some embodiments, the system can include a second collar. Some second collars can define a slot for accepting the spinal stabilization rod. The slot of the second collar can have a diameter which is larger than the smallest diameter of the bore. Regarding the spinal stabilization rod, it can have two portions one of which has a diameter corresponding to that of the slot of the second collar. The other portion of the spinal stabilization rod can have a diameter corresponding to the smallest diameter of the bore. In some embodiments, the spinal stabilization rod can include a transition portion between the first and the second portions.
One embodiment provides a collar for dynamically stabilizing a portion of a spine in conjunction with a spinal stabilization rod. The collar can include a body which defines a bore, an internal surface of the bore, and a contact point on the internal surface. The bore can be shaped and dimensioned to accept the spinal stabilization rod and to allow the spinal stabilization rod to pivot about the contact point. In some embodiments, the spinal stabilization rod can be flexible so that it can bend about the contact point.
Regarding the bore, various embodiments include internal surfaces of differing shapes including, in some embodiments, generally semi-spherical internal surfaces. The internal surface can be further shaped and configured to limit the range through which the spinal stabilization rod pivots. For instance, the internal surface can limit the spinal stabilization rod to a range of about six degrees in any direction. In some embodiments, the range through which the spinal stabilization rod can pivot can differ for differing directions. In some embodiments, at least a portion of the bore can have an oval cross sectional shape.
Embodiments provide spinal stabilization systems which can statically stabilize two or more vertebrae while dynamically stabilizing one or more other vertebrae.
In some embodiments, spinal stabilization systems can allow rotation of certain vertebrae about one or more axes thereby allowing patients to flex/extend, rotate, or bend (or combinations thereof) various portions of their back. Thus, spinal stabilization systems of various embodiments can allow patients to bend or arch their backs, twist their torsos, bend side-to-side, and combinations thereof. Furthermore, embodiments provide dynamic stabilization systems which require no closure member or other components besides a spinal stabilization collar and rod.
These, and other, aspects will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. The following description, while indicating various embodiments and numerous specific details thereof, is given by way of illustration and not of limitation. Many substitutions, modifications, additions, or rearrangements may be made within the scope of the disclosure, and the disclosure includes all such substitutions, modifications, additions, or rearrangements.
A more complete understanding of the disclosure and the advantages thereof may be acquired by referring to the following description, taken in conjunction with the accompanying drawings in which like reference numbers generally indicate like features.
The disclosure and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments detailed in the following description. Descriptions of well known starting materials, manufacturing techniques, components and equipment are omitted so as not to unnecessarily obscure the disclosure in detail. Skilled artisans should understand, however, that the detailed description and the specific examples, while disclosing preferred embodiments of the disclosure, are given by way of illustration only and not by way of limitation. Various substitutions, modifications, and additions within the scope of the underlying inventive concept(s) will become apparent to those skilled in the art after reading this disclosure. Skilled artisans can also appreciate that the drawings disclosed herein are not necessarily drawn to scale.
As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, process, article, or apparatus that comprises a list of elements is not necessarily limited only those elements but may include other elements not expressly listed or inherent to such process, process, article, or apparatus. Further, unless expressly stated to the contrary, “or” refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).
Additionally, any examples or illustrations given herein are not to be regarded in any way as restrictions on, limits to, or express definitions of, any term or terms with which they are utilized. Instead, these examples or illustrations are to be regarded as being described with respect to one particular embodiment and as illustrative only. Those of ordinary skill in the art will appreciate that any term or terms with which these examples or illustrations are utilized will encompass other embodiments which may or may not be given therewith or elsewhere in the specification and all such embodiments are intended to be included within the scope of that term or terms. Language designating such nonlimiting examples and illustrations includes, but is not limited to: “for example”, “for instance”, “e.g.”, “in one embodiment”.
It may be helpful at this juncture to briefly describe portions of vertebrae 22. Spinous processes and transverse processes allow tendons, muscles, etc. to attach to spine 20 for movement of spine 20 and various anatomical structures which are attached to spine 20 or affected thereby in various manners. These anatomical structures can include the patient's ribs, hips, shoulders, head, legs, etc. Spinous processes extend generally in a posterior and slightly inferior direction from vertebrae 22. Transverse processes also extend generally laterally from vertebrae 22 and allow muscles and tendons to attach to vertebra 22. Vertebral facets join adjacent vertebrae 22 to each other while allowing motion there between by being in sliding contact with corresponding vertebral facets of these adjacent vertebrae 22. During certain types of motion of spine 20 (such as flexing and extending) caused (or resisted) by various muscles, vertebrae 22 tend to rotate relative to each other about axes of rotation generally in the vertebral bodies (and more particularly proximal to points about one third of the anterior-posterior length of the vertebral bodies away from the posterior surface of these vertebral bodies). Since vertebral facets allow vertebrae 22 to articulate about these axes of rotation, no, or little, reactionary forces or moments are generated by healthy spines 20 themselves during ordinary movements.
Previously available approaches to dynamically stabilizing spine 20 include attaching stabilization rods to spine 20 in manners causing the rods to lie posterior to the spinous processes and therefore anatomically distant from intravertebral areas in which the vertebral axes of rotation lie. Since such previously available stabilization rods are distant from the vertebral axes of rotation they tend to generate reaction forces which resist movement of spine 20. Thus, as spine 20 extends or flexes, these previously available stabilization rods impede movement of spine 20. More particularly, the distances between vertebral axes of rotation can act as moment arms thereby generating moments and forces on spine 20. Therefore, spine 20 can cause reaction forces on the previously available spinal stabilization systems that can degrade the mechanical integrity and functioning of such spinal stabilization systems. Moreover, because such moments and forces (or their reactions) act on spine 20, spine 20 and patient 10 comfort and health can be adversely affected. As a result, the range of motion and patient comfort could be adversely affected with previously available spinal stabilization approaches. In addition, the moments and forces generated due to the anatomically significant distances between the vertebral axes of rotation and the previously available spinal stabilization systems can degrade the mechanical integrity of and functioning of such spinal stabilization systems.
However, as indicated by some patient 10 conditions, it may be desirable to dynamically stabilize some other particular vertebra 22′ with respect to other vertebrae 22. For instance, medical personnel may deem it desirable to allow vertebra 22′ to translate relative to other vertebrae 22 while also allowing selected amounts of rotation of vertebra 22′. For instance, surgical personnel may deem it desirable that vertebra 22′ be allowed to rotate relative to one or more axis 12, 14, or 16 (see
More specifically, medical personnel may select spinal stabilization rod 102 which includes rigid portion 108 and flexible portion 110. Rigid portion 108 can be of a material, shape, and dimension sufficient to withstand various loads (forces, moments, torques, etc.) expected to be applied to vertebrae 22. Flexible portion 110 can be of a material, shape, and dimensions to withstand selected loads on vertebra 22′ (and adjacent vertebrae 22) while allowing relatively unrestricted motion in response to (or to generate) other loads. Flexible portions 110 of spinal stabilization rods 102 can pivotably and slidably engage pivoting collars 106 as discussed herein.
With reference now to
Moreover,
Now with reference to
Among other features of various embodiments,
With regard to the engagement between spinal stabilization rod 102 and pivoting collar 106,
For instance, a comparison of
With reference now to
With reference now to
With reference now to
To attach embodiments of spinal stabilization system 100 to spine 20, surgical personnel can prepare patient 10 for surgery and open an incision generally near spine 20. In some embodiments, surgical personnel can use a posterior approach to spine 20 to attach spinal stabilization system 100 to spine 20. Surgical personnel can attach one or more clamping collars 104 to selected vertebrae 22. Surgical personnel can also attach one or more pivoting collars 106 to other selected vertebrae 22. Surgical personnel may then engage pivoting collar 106 with flexible portion 110 of spinal stabilization rod 102. More specifically, surgical personnel can insert flexible portion 110 through bore 117 of pivoting collar 106.
Surgical personnel can place rigid portion 108 of spinal stabilization rod 102 in, or near, clamping collar 104. If desired, surgical personnel can reduce spinal stabilization rod 102 into clamping collar 104. With spinal stabilization rod 102 seated in clamping collar 104, surgical personnel can advance closure member 115 (see
Thus, patients 10 treated with spinal stabilization system 100 (see
Although embodiments have been described in detail herein, it should be understood that the description is by way of example only and is not to be construed in a limiting sense. It is to be further understood, therefore, that numerous changes in the details of the embodiments and additional embodiments will be apparent, and may be made by, persons of ordinary skill in the art having reference to this description. It is contemplated that all such changes and additional embodiments are within scope of the claims below and their legal equivalents.
