Patent Application
20120226325
The present application relates to systems and devices implanted in surgery in a patient, and more particularly but not exclusively relates to systems, devices and techniques for retaining fastener elements of bone anchors to prevent undesired movement of the fastener elements relative to one another post-implantation in the patient.
The human spine serves many functions. The vertebral members of the spinal column protect the spinal cord. The spinal column also supports other portions of the human body. Vertebral implants are often used in the surgical treatment of spinal disorders such as degenerative disc disease, disc herniations, curvature abnormalities, and trauma. Many different types of treatments are used. In some cases, stabilization of one or more vertebral levels of the spinal column involves securing one or more bone anchors to bony structure of the spinal column. The one or more bone anchors can be subjected to various forces or conditions post-implantation that could result in one or more components of the bone anchor to be displaced from their initially implanted configuration. As a result, the effectiveness of the stabilization forces provided by the bone anchor may be reduced or compromised. Thus, there remains a need for further improvements in the devices employed in spinal stabilization techniques.
In one embodiment of the present application, a bone anchor includes a distal bone engaging portion, a proximal portion extending from the distal bone engaging portion that includes a thread profile, and a mating element that threadingly engages the thread profile of the proximal portion. A retention feature between the mating element and the proximal portion deforms to engage at least one of the mating element and the proximal portion of the bone anchor to resist the mating element from unthreading from the proximal portion of the bone anchor. In one particular embodiment, deformation of the retention element is caused when the mating element is threadingly engaged to the proximal portion, and the retention element increases the force or torque required to thread and unthread the mating element relative to the proximal portion of the bone anchor.
Another embodiment of the present application comprises a unique bone anchor for performing spinal stabilization in a patient. An additional embodiment of the present application comprises a unique bone anchor with a retention feature that prevents or resists displacement of the mating element relative to the bone anchor. In still another embodiment, a method for promoting spinal stabilization includes deforming a retention element between a mating element that is secured to a bone anchor and a portion of the bone anchor to which the mating element is secured to prevent or resist displacement of the mating element relative to the bone anchor.
Other embodiments include unique methods, systems, devices, kits, assemblies, equipment, and/or apparatus for use in connection with anchors for bony structures. However, in other embodiments, different forms and applications are also envisioned.
Further embodiments, forms, features, aspects, benefits, objects and advantages of the present application will become apparent from the detailed description and figures provided herewith.
For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any such alterations and further modifications in the illustrated devices and described methods, and any such further applications of the principles of the invention as illustrated herein are contemplated as would normally occur to one skilled in the art to which the invention relates.
The present application describes a bone anchor assembly with a retention element to resist or prevent movement of two or more components of the bone anchor assembly relative to one another. In one embodiment, the bone anchor assembly includes a distal bone engaging portion, a proximal portion extending from the distal bone engaging portion that includes a thread profile, and a mating element that threadingly engages the thread profile of the proximal portion. A retention feature deformably engages at least one of the mating element and the proximal portion to resist the mating element from unthreading from the proximal portion of the bone anchor.
In one embodiment, the retention feature includes at least one deformable element that is carried by one of the mating element and the proximal portion of the bone anchor, and protrudes therefrom so it contacts the thread profile of the other of the mating element and proximal portion as the mating element is engaged to the proximal portion. The deformable element increases resistance to threading and unthreading of the mating element and proximal portion relative to one another so that after the mating element is secured in the desired position with a driving instrument, the deformable element resists unthreading of the two components relative to one another post-implantation.
In one specific embodiment, the retention feature is a cylindrical pin that is elongated in directions paralleling a longitudinal axis along which the mating element and proximal portion are threadingly moved relative to one another. In a further variation of this embodiment, the pin is elongated in a direction transverse to the longitudinal axis. The pin can include a cross-section that is circular, square, rectangular, D-shaped, oval, non-circular, polygonal, or irregular. In other embodiments, the pin is not elongated but includes a spherical or cubical shape in shape.
The retention feature can also include one element or more than one element. If multiple elements are employed, the elements are discrete and spaced from one another. The discrete elements can be spaced regularly around longitudinal axis, irregularly around the longitudinal axis, along the longitudinal axis, and combinations thereof. In a further embodiment, the retention feature extends substantially around the entire thread profile of the mating element and proximal portion when engaged to one another. The retention feature can be secured to the bone anchor assembly by a press fit, an adhesive, a snap fit, a fastener, or allowed to simply reside in the receptacle without a substantial securing arrangement with the portion of the bone anchor assembly in which it resides.
Referring generally to
In still other embodiments, the bone anchor 12 is threaded along all or a substantial portion of its length. Bone anchor 12 may also include a distal bone engaging portion that is non-threaded, spiked, or hook-shaped, for example, or include any suitable configuration to engage bony structure. In addition, the bone anchor 12 may include a solid shaft 18, or a shaft 18 that includes a passageway that extends between and opens at the proximal end 14 and the distal end 16. The passageway can generally be sized and configured to allow placement of the bone anchor over a guidewire. Additionally or alternatively, the passageway may communicate with fenestration openings (not shown) that may be used to deliver material such as, for example, bone cement from the passageway and into areas of bone adjacent the bone anchor 12.
A non-threaded portion 22 extends between the distal threaded portion 20 and the proximal mounting portion 25, although embodiments where the distal threaded portion 20 extends to the proximal mounting portion 25 are also contemplated. The proximal mounting portion 25 includes external threading 24 extending radially outwardly from non-threaded portion 22 and an internal driving print 26 which may be non-circular such as, for example, hexagonal or rectangular shaped, to provide non-rotational engagement between the proximal mounting portion 25 and a driving instrument (not shown) to engage the bone anchor 12 and rotate it into bone or bony tissue. Examples of non-circular configurations for the driving print 26 include but are not limited to slotted, Phillips, hexagonal, Torx, spline drive, and double hex configurations.
Proximal mounting portion 25 is illustrated in
The mating element 30, as also shown in
The engaging member 44 extends between a proximal end 46 and a distal end 47, with a plurality of engaging members in the form of spikes 48 extending from the distal end 47. In other forms, the distal end 47 can be provided with teeth, knurling, grooves or other types of engaging features in addition to or in lieu of the spikes 48. The engaging member 44 also includes a passage 50 that extends between and opens at the proximal end 46 and the distal end 47. The passage 50 includes an arcuately rounded internal portion 52 extending distally from the proximal end 46 such that the engaging member 44 includes a partially spherical internal configuration. The passage 50 also defines an inner opening dimension at distal portion 54 that is generally greater than the outer dimension of the non-threaded portion 22 of the bone anchor 12 such that the engaging member 44 can be moved along the bone anchor 12 and pivoted relative to the bone anchor 12.
When the bone anchor assembly 10 is assembled, the engaging member 44 may be positioned along the shaft 18 of the bone anchor 12 distally of the mounting portion 25, and the arcuately rounded portion 40 of the mating element 30 may be positioned in the arcuately rounded portion 52 of the engaging member 44. In this arrangement, the interaction between the arcuately rounded portions 40, 52 and the ability for the engaging member 44 to pivot relative to the bone anchor 12 facilitates multi-axial positioning of the engaging member 44 in a plurality of planes that extend transversely to the plane of the mating element 30 when engaged with the external thread profile 24 of the mounting portion 25. Similarly, this adjustability facilitates use of the bone anchor assembly 10 in connection with bones that are oriented at an angle relative to the mounting portion 25 of bone anchor 12. Moreover, while not previously discussed, it should be appreciated that bone anchor assembly 10 can be implanted across adjacent bones or bone pieces and used to draw the adjacent bones or bone pieces toward one another. More particularly, once the distal threaded portion 20 of the bone anchor 12 is engaged with a first one of the bones or bone pieces, the mating element 30 can be rotated and distally advanced relative to the bone anchor 12 in order to bring the engaging member 44 into contact with a second one of the bones or bony pieces. As the mating element 30 is further rotated in this manner, the bones or bony pieces are drawn together and any gap positioned therebetween may be reduced or eliminated. However, it should be understood that the bone anchors described herein have application in any suitable spinal stabilization or other bone anchoring procedure.
While not previously discussed, it should be appreciated that the bone screw 12, the mating element 30, and the engaging member 44 may be formed from any suitable biocompatible material, including but not limited to titanium, titanium alloy, stainless steel, metallic alloys, polyaryletherketone (PAEK), polyetheretherketone (PEEK), carbon-reinforced PEEK, polyetherketoneketone (PEKK), polysulfone, polyetherimide, polyimide, ultra-high molecular weight polyethylene (UHMWPE), and plastics, just to name a few possibilities. It is further contemplated that retention element 50 is made from a material that deforms more readily than the material comprising at least the threads of mating element 30 and mounting portion 25. In particular, in the illustrated embodiment retention element 50 deforms as a result of contact with thread profile 24 of mounting portion 25 when mating element 30 is advanced sufficiently along mounting portion 25 to locate retention element 50 along thread profile 24.
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In still other embodiments, it is contemplated that other arrangements are provided for securing the retention element to the mating element. For example, in
In
In another example, in
Additionally, the instruments, devices, systems, techniques and methods described herein may also be used in surgical procedures involving animals, or in demonstrations for training, education, marketing, sales and/or advertising purposes. Furthermore, the instruments, devices, systems, techniques and methods described herein may also be used on or in connection with a non-living subject such as a cadaver, training aid or model, or in connection with testing of surgical systems, surgical procedures, orthopedic devices and/or apparatus.
Any theory, mechanism of operation, proof, or finding stated herein is meant to further enhance understanding of the present application and is not intended to make the present application in any way dependent upon such theory, mechanism of operation, proof, or finding. It should be understood that while the use of the word preferable, preferably or preferred in the description above indicates that the feature so described may be more desirable, it nonetheless may not be necessary and embodiments lacking the same may be contemplated as within the scope of the application, that scope being defined by the claims that follow. In reading the claims it is intended that when words/phrases such as “a”, “an”, “at least one”, and/or “at least a portion” are used, there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. Further, when the language “at least a portion” and/or “a portion” is used, the item may include a portion and/or the entire item unless specifically stated to the contrary.
While the application has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the selected embodiments have been shown and described and that all changes, modifications and equivalents that come within the spirit of the application as defined herein or by any of the following claims are desired to be protected.
