Orthopedic clamping hook assembly

An occipital clamping hook assembly includes a hook for engaging a first side of an occipital bone and a compressor movable relative to the hook for applying a compressive force to the occipital bone from a second side of the occipital bone. The occipital clamping assembly further includes a rod-receiving portion coupled to the hook for coupling a rod to the occipital bone engaged by the hook.

FIELD OF THE INVENTION

The present invention relates to spinal fixation devices used in orthopedic surgery. More particularly, the present invention relates to an orthopedic hook assembly for coupling a spinal rod to a bone, such as the occipital bone.

BACKGROUND OF THE INVENTION

Spinal fixation systems may be used in orthopedic surgery to align, stabilize and/or fix a desired relationship between adjacent vertebral bodies and/or the occipital bone in the skull. Such systems typically include a spinal fixation element, such as a relatively rigid fixation rod or plate, that is coupled to a bone by attaching the element to various anchoring devices, such as hooks, bolts, wires or screws. The fixation element can extend between two bone regions to effect stabilization, positioning, reduction or fixation of the bones. The spinal fixation element can have a predetermined contour that has been designed according to the properties of the target implantation site and, once installed, the spinal fixation element holds the bones in a desired spatial relationship, either until desired healing or spinal fusion has occurred, or for some longer period of time.

Occipital hooks and hook techniques in the prior art rely on positioning bone screws drilled through the skull bone as a method of fixation. However, the bone screws inserted through the occipital bone can damage the fragile occipital bone and/or fail to provide adequate bone purchase. The failure to provide adequate bone purchase, which may be due to poor bone quality as a result of damage, osteoporosis or other conditions, may cause the screw to slip relative to the bone. In addition, prior art occipital hooks do not accommodate for variations in the thickness of the occipital bone.

SUMMARY OF THE INVENTION

The present invention provides an orthopedic clamping hook assembly for creating a rigid attachment into a bone, such as the occipital bone, of varying thicknesses and allowing attachment of a rod, such as a cervical rod, to the anchored orthopedic clamping hook assembly. The orthopedic clamping hook assembly allows for rigid fixation to the occiput or other location without use of bone anchoring screws, which may not be feasible in thin bone areas. The orthopedic clamping hook assembly includes a body forming a hook at one end for engaging bone and a rod-receiving portion at a second end for receiving a spinal fixation element, such as a rod, to be connected to the bone. The orthopedic clamping hook assembly further includes a compressor for fixing the hook to the bone and applying a compressive force to a bone disposed between the compressor and the hook to thereby retain the hook assembly in a selected position. The compressor may be axially movable relative to the body of the orthopedic clamping hook assembly to fix the hook assembly relative to the bone.

According to a first aspect of the invention, an orthopedic clamping hook assembly is provided, which comprises a body having a longitudinal axis, a rod-receiving portion disposed at a first end of the body, a hook for engaging a first side of a bone, which is disposed at a second end of the body, and a compressor coupled to the body for engaging a second side of the bone. The compressor applies a compressive force to the bone disposed between the hook and the compressor.

According to another aspect of the invention, a method of inserting an occipital clamping hook assembly in a body is provided. The method comprises the steps of inserting a hook through a hole in an occipital bone and into engagement with a first side of the occipital bone and moving a compressor coupled to the hook towards a second side of the occipital bone to apply a compressive force to the bone.

According to still another aspect of the invention, an occipital fixation system is provided, which comprises an occipital fixation plate including a body for stabilizing a spine of a patient and having at least one hole extending therethrough and an occipital clamping hook assembly. The occipital clamping hook assembly has a hook inserted through a first hole of the plate configured to engage a first side of an occipital bone. The occipital clamping hook assembly apples a compressive force to the plate and occipital bone.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides an improved orthopedic clamping hook assembly in a spinal fixation system. The invention will be described relative to use in the occipital region of a patient. One skilled in the art will recognize that the invention is not limited to use in the occipital bone, other bones, or in spinal surgery, and that the instrument and methods described herein can be adapted for use with any suitable surgical device to be moved into a selected position in a variety of medical procedures. The present invention will be described below relative to certain exemplary embodiments to provide an overall understanding of the principles of the structure, function, manufacture, and use of the instruments disclosed herein. Those skilled in the art will appreciate that the present invention may be implemented in a number of different applications and embodiments and is not specifically limited in its application to the particular embodiments depicted herein.

FIGS. 1A-7illustrate an orthopedic clamping hook assembly, illustrated as an occipital clamping hook assembly10, according to a first illustrative embodiment of the invention. The occipital clamping hook assembly10may be used to create a rigid attachment into an occipital bone80of varying thickness and/or different occipital bones of different thicknesses subsequent fixation of a spinal rod90to the occipital bone80, as shown inFIGS. 1A and 1B. One skilled in the art will recognize that the assembly10may be used to couple any fixation device to any type of bone, in any location within the body, and is not limited to use with the occipital bone. The illustrative occipital clamping hook assembly10applies a compressive force to secure the assembly to the bone80, without requiring use of bone screws.

The occipital clamping hook assembly10shown inFIGS. 1A-7includes a body11forming a hook20at a first end for engaging bone and a rod-receiving portion30at a second end for receiving a rod or other spinal fixation element to be fixed to the bone. As shown inFIGS. 1A and 1B, the hook portion20of the assembly10is inserted through a hole81in the occipital bone80, or at the edge of a deformity, and engages the bone on an inside surface. The hole81may be formed by an instrument, such as a drill or burr, or may comprise an edge of a deformity formed in the skull. Alternatively, the hole81may be formed as a result of tumor removal, after which the occipital clamping hook assembly10is implanted. In the illustrative embodiment, the hook20and the rod-receiving portion30are integrally formed with the body11, though one skilled in the art will recognize that the hook20and rod-receiving portion may be coupled to the body through any suitable means known in the art.

The occipital clamping hook assembly10further includes a compressor40coupled to the body11for applying a compressive force to the occipital bone80and securing the assembly10relative to the bone80. The compressor40is separated from the hook20by a variable separation distance D to form a region for holding the bone80therebetween. The compressor is axially movable relative to the body11to sandwich and compress the bone80between the compressor40and the hook20, as shown inFIG. 1B. The variable separation distance D between the hook20and the compressor40allows for accommodation of bones having varying thicknesses and strengths, as well as variation in the amount of compressive force applied by the compressor40to secure the assembly10to the bone80.

Prior to insertion, the compressor40is preferably positioned so as to be separated from the hook20to facilitate insertion of the hook into the bone, as shown inFIG. 1A. Then, after the hook is inserted into the bone, the compressor40may be moved into an engaged position to secure the assembly10relative to the bone80, as shown inFIG. 1B. In the illustrative embodiment, the compressor40moves over threads110towards the bone80and hook20to sandwich and compress the bone80between the compressor40and the hook20, though one skilled in the art will recognize that any suitable means for securing the occipital clamping hook assembly10to the bone80may be used in accordance with the teachings of the invention.

As shown inFIGS. 8A-8C, the illustrative occipital clamping hook assembly10may be implemented in a spinal fixation system100including an occipital fixation plate102to fix the occipital fixation plate102relative to the occipital bone, as well as to connect spinal rods to the plate102and occipital bone. The occipital fixation plate102comprises a substantially flat body for stabilizing the spine including openings112,114for receiving the occipital clamping assemblies10for securing the plate102to the occipital bone. The openings112,114align with openings, such as the opening81inFIGS. 1A and 1B, in the occipital bone80. The hook20of the assembly10is inserted through the aligned openings in the plate and occipital bone, and engages the occipital bone on an inner surface of the bone opposite the plate102, such that the body11and rod-receiving portion30extends through the corresponding opening112or114of the plate102. The compressor40of the clamping hook assembly10then advances towards the hook20to compress the plate102and occipital bone between the compressor40and the hook20, thereby securing the hook assembly10and the occipital fixation plate102to the occipital bone.

The compressor40in the occipital clamping hook assembly10of the invention may have any suitable size, shape and configuration suitable for applying a compressive force to an object sandwiched between the compressor40and a corresponding hook20.FIGS. 9A-9Cillustrate in detail an embodiment of the compressor40of the illustrative hook assembly10shownFIGS. 1-8C. In the embodiment shown inFIGS. 1-9C, the compressor40comprises a substantially disc-shaped flange having a central opening420configured to receive and encircle the body11. The body11of the illustrative hook assembly10, illustrated inFIGS. 10A-10F, preferably has a substantially cylindrical shape matching the central opening420, which has an inner diameter Dithat is slightly larger than the outer diameter Doof the body11to accommodate the body11in the central opening420. The compressor40includes a bottom surface430for contacting bone80or a plate102, and applying a compressive force to the bone sandwiched between the compressor40and the hook20.

The compressor40may be movably coupled to the body11through any suitable means known in the art. For example, mating threads may be used to facilitate relative, controlled movement of the compressor40relative to the body11. In the embodiment ofFIGS. 1-9C, the body11includes a set of threads110formed on an outer surface thereof. The illustrative compressor40includes a set of threads410formed on an inner surface of the central opening420configured to mate with the set of threads110on the body11. The threads in the sets110and410extend substantially perpendicular to the longitudinal axis A-A of the body11, so that rotation of the compressor40about the longitudinal axis A-A translates into axial movement of the compressor40relative to the body11and the hook20.

The compressor40preferably has a ridge422surrounding the central opening420and a thinner projection424extending from and around the central opening420. The ridge422increases the axial thickness of the compressor around the central opening420to accommodate more threads, facilitating the movable connection of the compressor40to the body11. According to one embodiment, the compressor40further includes peripheral openings426a-426dabout the perimeter of the projection424for receiving a tool for rotating the compressor40about the longitudinal axis A-A of the body11to move the compressor40into engagement with the bone.

The bottom surface430of the flanged compressor40may be configured to engage or otherwise interface with bone80or a fixation plate102. For example, the bottom surface430may be contoured or shaped to match one or more bone features. The bottom surface430may include teeth or other textured surface for engaging the occipital bone or a spinal fixation plate. Alternatively, or in addition to engagement means, the bottom surface may be cushioned or include another element for absorbing forces on the compressor40.

A washer (not shown) may also be used between the compressor40and the hook20to take up tolerance during clamping of the assembly10to the occipital bone, or another bone engaged by the assembly, using the compressor40.

The compressor40may also have a lock42for locking the compressor40in an engaged position with the bone. The lock42may be deployed manually when the compressor40clamps the bone, or automatically when a predetermined threshold force is reached. The lock42may comprise any suitable device known in the art for locking the compressor in a selected position relative to the body11. For example, the lock42may be formed by forming a hole in the compressor configured to receive a pin, which may be inserted through the hole and into the engaged bone to prevent further rotation of the compressor40, as illustrated in FIG.1B1. Another embodiment of the lock42may comprise a nut tightened on top of the compressor40after the compressor reaches a suitable position to prevent further rotation of the compressor, or any other suitable means for preventing derotation of the compressor after engagement, as illustrated in FIG.1B2.

One skilled in the art will recognize that the compressor40may have any suitable size, shaped and configuration for clamping the occipital clamping hook assembly10to an occipital bone, and is not limited to the embodiment shown inFIGS. 1-9C.

FIGS. 10A-10Fillustrate the body11of the illustrative occipital clamping hook assembly10ofFIGS. 1-8C. In the illustrative embodiment, the rod-receiving portion30of the body includes a substantially U-shaped slot32for receiving a spinal rod or other spinal fixation element. The slot32extends along an axis B-B and includes internal threads320for receiving a capping element or other suitable device for locking a rod in the slot32. One skilled in the art will recognize that the rod-receiving portion30may have any suitable configuration for receiving a rod or other spinal fixation element to be coupled to the occipital bone using the occipital clamping hook assembly of the present invention.

The hook20of the illustrative occipital clamping hook assembly ofFIGS. 1-10Fextends from the first, bottom end of the body11and may have any suitable size, shape and configuration for engaging bone, in particular the occipital bone. The illustrative hook20comprises a tapering protrusion that has a curved connecting portion21where the rod extends from the body11and a straight end portion22where the hook20engages the bone. The width W of the end portion22may remain substantially constant or may be tapered. The end portion22preferably includes a flat inner surface24that lies flat against the bone when the hook assembly is in an engaged position, as shown inFIG. 1B. Alternatively, the inner surface24may be contoured or textured to facilitate engagement with the bone. The tip22aof the end portion22may be curved, as shown inFIGS. 10a-10f, or may have another suitable configuration. The end portion22may extend from the curved connecting portion21(aligned with the axis A-A) by any selected amount suitable for engaging bone. In the embodiment ofFIGS. 1-10f, the end portion22has a length such that the tip22aaligns with the edge of the compressor flange when the assembly10is assembled, as shown inFIGS. 1A-7. However, one skilled in the art will recognize that the hooking end portion22may have any suitable size, shape, length and configuration.

In the illustrative embodiment, the curved connecting portion21of the hook20extends from a first side L of the body11(i.e., a half extending of a first side of a plane extending through the longitudinal axis) and creates a space202between a second side R of the body on an opposite side of the plane extending through the longitudinal axis and the end22of the hook20, as shown inFIG. 10D. The curved connecting portion21has a curved inner wall210that curves about 180 degrees and intersects the inner wall24of the end portion. The side walls212,214of the connecting portion21may be substantially flat and the outer surface216may also be curved. One skilled in the art will recognize that the hook20may have any suitable configuration suitable for engaging an occipital bone.

According to one embodiment, the hook20may be selectively movable relative to the body11and then locked in a particular configuration relative to the body and/or the bone.

While the illustrative occipital clamping hook assembly10ofFIGS. 1-10Fincludes a single hook20, the assembly may alternatively include multiple hooks disposed at the first end of the body11and configured to engage bone.

The external threads110for coupling the compressor40to the body11preferably extend from upper portion of the body around bottom of the slot32to the connecting portion21of the hook20. However, the threads, or other suitable engagement means, may alternatively have any suitable size, length, location and configuration.

FIGS. 11A-11Dillustrate another embodiment of an orthopedic clamping hook assembly, illustrated as an occipital clamping hook assembly10′, according to the present invention. Components of the occipital clamping hook assembly10′ corresponding to the components of the occipital clamping hook assembly10ofFIGS. 1-10Fare represented by the same number, differentiated by a prime. The occipital clamping hook assembly10′ ofFIGS. 11A-11Dincludes an internal compressor40′ for applying a compressive force to retain a bone between the hook20′ and compressor40′. Referring toFIGS. 12A-12F, the body11′ of the occipital clamping hook assembly10′ includes an axially extending internal passageway111below the rod-receiving portion30for receiving the compressor40′. The compressor40′, shown inFIG. 13comprises a substantially cylindrical-shaped solid object having an outer diameter D3that is slightly less than an inner diameter D4of the axially extending internal passageway111. The axially extending internal passageway111includes a set of internal threads112located on an interior surface thereof. The compressor40′ includes a set of external threads402on an outer surface thereof configured to mate with the internal threads112, such that rotation of the compressor40′ about the axis A-A advances or retracts the compressor40′ along the passageway. The bottom of the axially extending internal passageway111opens to a region202′ between the hook20′ and the compressor40′, which protrudes from the opening by a selected distance to apply a force to a bone inserted in the region202′.

The compressor40′ includes a substantially hexagonal opening on the top surface thereof for receiving a driver for rotating the compressor.

In the embodiment shown inFIGS. 11A-11D, the hook20′ extends from a first side wall on a first side L of the body11′ to an end portion that aligns with an opposite wall on an opposite side R the body and forms the space202′ between the body11′ and the hook for receiving bone. However, one skilled in the art will recognize that the hook20′ can have any suitable length suitable for engaging bone. In the illustrative embodiment, the body11′ has a slanted bottom surface119through which protrudes the compressor40′. The slanted surface119facilitates insertion of the hook20′ below the bone prior to engagement by the compressor40′.

According to another embodiment of the invention, the rod-receiving portion of an orthopedic clamping hook assembly, such as an occipital clamping hook assembly, and/or a hook portion of an orthopedic clamping hook assembly, such as an occipital clamping hook assembly, may be movable relative to the body of the assembly. For example,FIGS. 14A-14Fillustrate an embodiment of an occipital clamping hook assembly10″ including a rod-receiving portion30″ that is movable relative to a body portion11″ to allow for angulation of one portion of the assembly relative to another portion of the assembly and bone coupled to the assembly. The assembly10″ may allow for the rod-receiving portion30″ to pivot in all directions about a 360° arc relative to the body11″ or in one or more selective directions. The use of a movable rod-receiving portion facilitates insertion and connection of a spinal rod that extends at in a non-parallel direction relative to the bone and/or the opening in the bone.

The body11″ of the movable occipital clamping hook assembly10″ includes a drive shaft113and a cylindrical base portion115having a central opening116for receiving the drive shaft113. The drive shaft113includes a joint portion117for movably mounting the rod-receiving portion30″ through means known in the art. An example of means for movably mounting a rod-receiving portion or other suitable head portion to a shaft is described in detail in Application Publication Number US 2004/0186473 entitled “Spinal Fixation Devices of Improved Strength and Rigidity”, U.S. Patent Application Publication Number US 2004/0181224 entitled “Anchoring Element for Use in Spine or Bone Surgery, Methods for Use and Production Thereof” and U.S. Patent Application Publication Number US 2003/0100896, entitled “Element With a Shank and a Holding Element Connected to It for Connecting to a Rod”, the contents of which are herein incorporated by reference.

The base portion115includes threads110″ formed on an outer surface thereof for mating with threads410on a corresponding compressor40″ to allow the compressor40″ to move relative to the hook portion20″ to secure and compress a bone therebetween.

In the occipital clamping hook assembly10″ shown inFIGS. 14A-14F, the hook portion20″ is also movable relative to the body11″. The illustrative hook portion20″ comprises two protrusions20a,20bmovably coupled to a bottom surface115aof the base portion115, though one skilled in the art will recognize that a movable hook portion may comprise one or several hooks. In an unengaged position, shown inFIG. 14E, the protrusions20a,20bare pulled in under the bottom surface115a. In an engaged position, as shown inFIGS. 14A,14D and14F, the protrusions20a,20bshift position and extend from the bottom surface115ato form hooks for engaging the bone. According to one embodiment, a rotation of the drive shaft about the axis A-A serves to move the protrusions20a,20bfrom an unengaged position to an engaged position, though one skilled in the art will recognize that any suitable means for operating the movable hooks may be used.

The occipital clamping hook assembly10″ shown inFIGS. 14A-14Ffurther includes grooves420formed on a bottom surface of the compressor40″ forming teeth for engaging bone, as described above.

An orthopedic clamping hook assembly according to the illustrative embodiments of the invention provides significant advantages over prior systems and methods for coupling a fixation device to a bone, such as an occipital bone. For example, prior systems generally require use of bone screws, which can damage fragile bone. The orthopedic clamping hook assembly of the illustrative embodiments may utilize a variable compressive force to fix the assembly and associated spinal fixation device to a bone. The orthopedic clamping hook assembly of the illustrative embodiments may be flexible to accommodate bones of varying thickness. In addition, an orthopedic clamping hook assembly of an embodiment of the invention may enable relative movement of components to accommodate other fixation devices and/or contours in the bone structure.

The present invention has been described relative to an illustrative embodiment and application in the occipital bone. Since certain changes may be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense. For example, one skilled in the art will recognize that the assembly of the illustrative embodiment of the invention is not limited to use with spinal rods and can be used with any suitable implant for any suitable orthopedic system. In addition, the assembly is not limited to use in the occipital region of a patient and may be used in any suitable location of a patient where it is desirable to anchor an implant to a particular location of the patient's body.