WO2011057178A1 - System and method for stabilizing and fixating lumbar vertebrae - Google Patents

Abstract

The subject invention provides minimally invasive systems and methods for stabilizing adjacent vertebrae to be fused. A system of the invention is configured to easily and accurately position a rod atop pedicle screws inserted within a patient's vertebrae. One embodiment of the system comprises: at least one pedicle screw (10) with a variable angle or multi -axial screw head; at least one screw extension (300) having a means (314) for connecting with the screw; a support rod (400) having at one end a ball -shaped head (402); and at least one socket clamp (200) receivable on the anchor screw via the screw extension, where the socket clamp is of a unitary, inseparable structure that includes a screw engaging portion and a hemispherical recess to receive the ball -shaped head of the support rod. The socket clamp comprises an upper and lower branch that together define the hemispherical recess (218, 220). The upper and lower branches are linked by a connecting area, where the connecting area comprises two passages (206, 210) through which the screw extension and connecting means pass.

Description

DESCRIPTION

SYSTEM AND METHOD FOR STABILIZING AND FIXATING LUMBAR VERTEBRAE CROSS-REFERENCE TO A RELATED APPLICATION

This application claims the benefit of U.S. provisional applications Serial No. 61/258,692, filed November 6, 2009 and Serial No. 61/327,195, filed April 23, 2010, both of which are incorporated herein by reference in their entirety. BACKGROUND OF THE INVENTION

Over the past few decades, numerous systems and methods have been created for stabilizing and fixating lumbar vertebrae. These systems generally include a rod for supporting the spine and for properly positioning components of the spine. Often, bolts, screws, and/or hooks are anchored to the vertebrae for connection to the supporting rod. These vertebral anchors must frequently be placed at various angles due to the anatomical structure of the patient, the physiological problem being treated, and the preference of the physician.

Most of these lumbar vertebrae stabilization and fixation systems require an "open" procedure involving an extensive incision of the skin, extensive detachment or "takedown" of the paravertebral muscles, and exposure of the bony elements. This involves a significant, complex surgical intervention, with massive dissection of the paravertebral musculature. As a consequence, the classic lumbar fusion procedure is associated with significant morbidity, including blood loss, increased anesthesia time with its attendant complications, and increased risk of infection. Additionally, quite often the patient experiences significant postoperative pain requiring longer hospital stay which adds substantial cost to the current systems.

To address these problems, more and more spinal surgeries are performed using less invasive or minimally invasive techniques to reduce the trauma of posterior spinal surgery by reducing the size of incision and degree of muscle stripping necessary to access the vertebrae. When applying less invasive and/or minimally invasive techniques, it is difficult to provide secure connections between the spinal support rod and corresponding vertebral anchors at all the various angles that are required. Often, with such procedures, the incision is enlarged to enable proper positioning of the rod in relation to the screw. Otherwise, the misorientation of the supporting rod in relation to the anchor/screw can occur, particularly where several complex or intricate parts need to be manipulated for proper implantation.

One procedure developed to overcome the drawbacks of the classic lumbar vertebrae fixation/stabilization procedure includes the use of unique endoscopic equipment. The cost of such equipment can be prohibitively high which limits the use of this procedure to a few medical facilities. Still another undesirable consequence of the endoscopic procedure is its complexity, requiring considerable experience of a medical staff capable of using this equipment to properly place the screws as well as a staff of highly trained technicians.

U.S. Patent No. 6,443,953 discloses a system that is configured to interlock the pedicles of the vertebral bodies to be fused; it includes inserting multiple screws into pedicles and bridging the screw heads of the screws by a connecting rod. As illustrated in FIG. 1, implementation of such a procedure requires that a superior positioned incision be made in the paravertebral tissues of the lower thoracic area located below the lowest of the screws 22. Connecting rod 14 is then passed parallel to the spine, as indicated by an arrow A, through holes 18 in the screw heads 12 and is secured into position by initially topping the screw heads 12 with caps 20 and, further, by placing nuts 16 in the caps 20. Displacement of the rod 14 through soft tissues, otherwise uninvolved by the procedure, introduces potential injury to these soft tissues. Furthermore, this procedure requires the precise alignment of the screws and, particularly, each of the holes 18 of the adjacent screw heads 12 with the connecting rod 14 as well as with one another. Hence, the procedure is associated with additional requirements imposed upon a surgeon, an increase in overall surgery time and, as a consequence, increased health risks for the patient.

U.S. Patent No. 5,545,166 discloses a spinal fixation system that includes a plurality of anchor screws, clamp assemblies, pivot blocks, clamp blocks, spindles, swing bolts, and rods that are implanted along a patient's spine to fix two or more adjacent vertebrae relative to one another. To implant this system, an "open" procedure is necessary to expose vertebrae to be treated and to provide sufficient room to manipulate and implant the various complicated parts described above. During the procedure, it may be desirable to adjust the vertebrae relative to one another. In that instance, each of the various parts require further manipulation (for example, screws must be loosened and the rod, clamp blocks, and/or pivot blocks must be adjusted, such as by moving the spindles to adjust the height of the pivot blocks and/or clamp assemblies on the anchor screws, by pivoting the swing bolt anchor screws, and/or pivoting the clamp blocks relative to the pivot blocks). Because so many parts are necessary to secure and appropriately position the system, there is a greater possibility for error during installment, a greater degree of difficulty in performing the procedure thus potentially increasing the risk of poor outcome in the patient.

U.S. Patent Nos. 7,306,603; 7,497,869; 7,547,318; and 7,588,588 describe systems in which hollow rod guidance tubes having slits through which the rods are placed over pedicle screws are provided. Vertically aligned rods are placed within and slid down the tubes atop the pedicle screws. The rods are then positioned over pedicle screws by passing through the slits to lay perpendicular to the screw heads. For example, U.S. Patent No. 7,306,603 describes pedicle screws with screw heads configured to receive a vertically aligned rod having at one end a pin inserted therethrough. The screw heads include slots for receiving the rod pin. In use, the rod is positioned over the screw heads using hollow "dilators" with slits therein to allow the rod to penetrate therethrough and interlink the screws. This and the other related systems in the patents listed above have several drawbacks. First, to ensure the rods are positioned over the screws, the dilator slits must be perfectly aligned with the slots atop the screw heads before the rods are to be deposited into the dilators for implant. Alignment of the slits with the screw head slots is particularly difficult in a minimally invasive procedure where the incision size is relatively small. Further, because there might be difficulty in having the rod exit the dilator slit, an additional rod guiding tool is necessary to ensure proper placement of the rod. Once the rod is placed within the screw head, there is little degree for rod adjustment since the walls for securing the rod over the screw head encompass the entire circumference of the screw head.

U.S. Patent No. 5,938,663 discloses a spinal instrument to adjustably connect rods comprising a nut that clamps to a receiving and locking assembly. The device has a ball joint positioned in a clamp. The ball joint includes a passage through which a rod is inserted, where it provides for angularly connecting the rod to the screw. This system either requires an "open" procedure (large incision) to snap the ball joint into the clamp receptacle or a separate incision is necessary to transversely move the rod through tissue and muscle and spear it through the small passage in the ball joint. This procedure is difficult to perform; moreover, the use of an additional access site for the rod can undesirably lengthen the surgical procedure. Further, although the "compressible ring" forms a ball joint, the shape of the receiving and locking assembly prohibits a full range of motion for the rod. Thus, the device is still characterized by a limited range of motion, which is not advantageous for surgical procedures involving complex anatomical situations.

U.S. Patent Nos. 7,3 14,467 and 7,578,833 both are directed to spinal fixation systems with clamp assemblies that consist of two separable portions, where a first portion must be placed onto the an upper portion of the screw head prior to placement of a rod. Following placement of the rod onto the first portion of the clamp, the second portion is fitted over the rod and the upper portion of the screw to "clamp" the rod in place. A nut or other fastener is used to secure the clamp assembly to the screw and the rod and lock the components in place. As such, the methods for positioning a rod using these systems require: first the lower portion of the clamp be placed over the swing bolt, second the placement of the rod onto the lower portion of the clamp, and only following placement of the rod is the upper portion of the clamp placed over the swing bolt and lower portion of the clamp. This system is not particularly effective with minimally invasive or less invasive procedures, where little room is afforded (due to a small incision) for maneuvering the rod and clamp portions over the screws. Further, there is greater likelihood for error in installing the rod because the rod may slip out from the bottom portion of the clamp prior to securing the top portion of the clamp over the screw head. Alternatively, the rod may not be properly placed within the bottom portion of the clamp and when locked into such position, the system harms the patient. Further, because the top clamp must be secured over both the screw head and the rod and bottom clamp, there is a great deal of manual manipulation and precision required of the surgeon.

U.S. Patent No. 7,858,299 discloses a connector assembly for coupling a rod to a pedicle screw. The connector assembly consists of: a passage through which a proximal portion of a screw is inserted; a clamping member through which a rod is inserted; and an engaging member for engaging the clamping member to fix the position of the rod within the clamp. With this system, several parts are manipulated by the surgeon within the body to secure the rod in alignment with the screws. For example, either an invasive open procedure is necessary to properly transversely insert the rod through the passage in the clamping member or a great deal of manipulation is necessary to position the connector assembly over the proximal portion of the screw. Because the proximal portion of the screw is permanently implanted in the patient, it must maintain a relatively low profile. This low profile forces the surgeon to "fish around" in the patient with the connector assembly to properly insert the proximal portion through the connector assembly. Finally, because the engaging member pushes the lower portion of the connector assembly toward the proximal portion of the screw (thus securing the connector assembly to the screw), this also causes the opening between the arms of the clamping member to widen and increase the likelihood that the rod might fall out of the assembly.

Many of the systems described above require insertion of the rod into a clamping assembly. Insertion of the rod normally requires a large incision through the skin and detachment of the paravertebral muscles to access the vertebral members. This type of procedure usually results in a longer surgical procedure with greater amounts of blood loss and increased anesthesia time. These procedures may also have a higher risk of infection, require a longer postoperative recovery time, and result in addition pain and discomfort to the patient.

Yet another problem associated with the systems discussed above is the continued difficulty in manipulating the rod into an acceptable position over the pedicle screws, particularly should the rod disconnect from any part of the clamping system. Often, with the above systems, repeated use of fluoroscopic imaging is necessary to insure that the rod is fully seated and in a correct position in relation to the pedicle screws. High exposure to radiation from fluoroscopic procedures has been associated with serious skin injuries. Moreover, continued repeated use of fluoroscopy can lead to lens injuries and cataracts, and possibly cancer.

It is, therefore, desirable to provide an instrumentation system and a method for using the same that minimize the disturbance of soft tissue, reduce the overall time of surgery, optimize the guidance of the connecting rod toward screws, and simplify the placement of the rod and the screws so that little or no fluoroscopy is necessary to perform minimally invasive lumbar vertebrae stabilization and/or fixation procedures. The present invention minimizes, and in some aspects eliminates, the above-mentioned failures, and other problems, by utilizing the methods and structural features described herein. BRIEF SUMMARY OF TFIE INVENTION

The subject invention provides unique systems and methods for stabilizing and/or fixating lumbar vertebrae, wherein the systems have a low profile, are easily assembled, relatively inexpensive to make, and simple in operation. Further, the systems and methods described herein would increase the ease of installation and adjustment of relatively few components while decreasing the total time required for surgical implantation and fixation. The subject invention also provides systems and methods useful in correcting spinal deformity, spondylolisthesis, or fractures/disclocations. Finally, the systems and methods described herein are particularly applicable to minimally invasive surgical techniques.

One embodiment of the lumbar vertebrae stabilization/fixation system of the invention comprises: at least one multi-axial pedicle screw; at least one screw extension having at. one end means for detachably connecting with the screw; a support rod having at one end a ball-shaped rod head; and a socket clamp receivable on the screw via the screw extension, where the socket clamp is a unitary, inseparable structure that includes both a screw engaging portion and a socket having a hemispherical recess to receive the support rod ball-shaped head. The socket clamp preferably comprises two branches, an upper and low^rer branch, that together define the hemispherical recess within which the rod ball-shaped head is disposed. The upper and lower branches are inseparably linked by a connecting area, wherein the connecting area defines a screw receiving portion comprising a passage for receiving the extension and the clamp engaging segment of the screw. The passage for receiving the screw extension and clamp engaging segment is transversely oriented to the two branches. The socket of the socket clamp, when enclosed about a ball-shaped head of a rod, enables the rod to obtain motion around an indefinite number of axes, which have one common center. For example, the socket clamp may enable the rod with about 120° spherical motion in relation to the pedicle screw until locked into a position by the user.

In a related embodiment, additional pedicle screws, screw extensions, and rod clamps are provided, where the rod clamp is a unitary, inseparable structure receivable on the screw and includes a screw engaging portion and a rod engaging portion. The rod clamp is of a unitary, inseparable structure. The rod clamp includes a rod engaging portion preferably comprising two branches, an upper and lower branch, that define a rod passage. The upper and lower branches are inseparably linked by a connecting area, wherein the connecting area defines a screw receiving portion comprising a passage for receiving the screw extension and the clamp engaging segment. The passage for receiving the screw extension and clamp engaging segment is transversely oriented to the two branches. In certain embodiments, a screw system is provided with a locking mechanism for the multi-axial screw head that is useful in correcting spinal deformity, spondylolisthesis, or fractures/disclocations. The screw system enables the clinician to forcefully contour abnormal anatomy into therapeutically correct positions.

In another embodiment, the other end of the rod includes a means for preventing it from slipping out of the rod engaging portion of a rod clamp. Examples of slippage preventing means include a male portion for receiving a female cap that is of greater diameter than the rod passage of the rod clamp, a lip that forms around the peripheral edge of the end of the rod, and the like.

With all of the systems described herein, a locking mechanism, such as a nut, is provided for securing and locking the position of the clamp(s) on the screw(s).

In a method of use, at least one screw is screwed into a bone body (such as lumbar vertebra) using a screw drive. In certain embodiments, the extension includes a driver for fitted insertion into the drive of the screw head, wherein the extension can be used to turn and drive the screw into bone. The extension is removably attached to the screw. At least one clamp of the invention is fastened on the supporting rod. For example, the socket of a socket clamp is affixed over a ball-shaped head of a rod, and where needed, additional clamps (either socket or rod) are affixed to the rod. The entire clamp/rod assembly is then secured to the screw(s) by having the screw receiving portion of the clamp(s) engage the extension(s) attached to the screw(s). The clamp/rod assembly slides down over the extension(s) to the head of the screw(s). The clamp/rod assembly is then positioned as desired by the clinician over the screw(s).

Once the assembly is positioned as desired atop the screw(s), locking mechanism(s) is slid down the extension(s) and used to secure the entire clamp/rod assembly to the screw(s). Following securing the locking mechanism(s) to the assembly and screw, the extension(s) is removed. In this manner, unlike previous methods in which the rod must be inserted transversely through or placed on top of clamps secm-ed to the pedicle screw, the rod is passed in a side-loading fashion, lateral to the screw and screw extension, where because of the clamp/rod assembly and multi-axial screw head, the rod is already desirably positioned without undue clinician manipulation. Further, the positioning and attachment of the clamp assembly to the screws are accomplished in a simple and fail-safe manner with the use of the screw extensions. The subject invention is particularly advantageous with less invasive and/or minimally invasive procedures because it is easy to assemble and operate, in part due to the unitary, inseparable clamp structures. Unlike other clamps described in the patents discussed above where either the pedicle screw or the rod must be secured via two or more elements of the clamp, the subject clamps easily engage both the pedicle screw (and extension) and the rod without undue clinician manipulation. More importantly, where smooth placement of rods is often the Achilles heel of current minimally invasive spinal vertebrae stabilization procedures, the subject invention provides a fail-safe system for rod placement. By passing the clamp/rod assembly onto the screw heads via extensions, the rod is inserted into the body in a side-loading fashion, lateral to the screw. In this manner, the entire rod/clamp system can be passed down blindly through a small skin incision with a high degree of reliability. This is far desirable over the systems of the prior art in which a large incision through soft tissue (skin, fascia, and muscle) is necessary to insert a rod directly into the head of one or more pedicle screws or to insert a rod transversely through clamps already secured to pedicle screws. Further, it is far more advantageous than the prior art systems for minimally invasive procedures in which a rod is dropped through a channel and expected to properly fall into place. Unlike those systems in which a certain amount of luck is necessary, the present system provides a fail-safe system and method for properly positioning the rod. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a side view of an inst rumentation system of known prior art.

Figure 2A is a side view of a multi-axial screw, rod clamp, and screw extension assembly in accordance with the subject invention.

Figure 2B is a side view of a multi-axial screw, socket clamp, and screw extension assembly in accordance with the subject invention.

Figure 3A is a side view of one embodiment of a multi-axial screw in accordance with the subject invention.

Figure 3B is a side view of another embodiment of a multi-axial screw in accordance with the subject invention.

Figure 3C is a side view of another embodiment of a screw assembly with a skirt- locking nut. Figure 3D is a side view of another embodiment of a screw assembly with a clamp receiving segment having a break-off portion, wherein the exterior of the clamp receiving segment and a top portion of the skirt is continuously threaded.

Figure 4 is a side view of one embodiment o a rod assembly in accordance with the subject invention.

Figure 5A is a side view of the disassembled parts of a rod clamp in accordance with the subject invention.

Figures 5B-5C are side views of the assembled parts of a rod clamp in accordance with the subject invention.

Figure 5D is a top view of an assembled rod clamp in accordance with the subject invention.

Figure 5E is a perspective view of an assembled rod clamp in accordance with the subject invention.

Figure 6A is a side view of the disassembled parts of a socket clamp in accordance with the subject invention.

Figures 6B-6C are side views of the assembled parts of a socket clamp in accordance with the subject invention.

Figure 6D is a top view of an assembled socket clamp in accordance with the subject invention.

Figure 6E is a perspective view of an assembled socket clamp in accordance with the subject invention.

Figure 7A is a side view of an embodiment of a rod clamp in accordance with the subject invention.

Figure 7B is a side view of the embodiment of Figure 7 A after being secured with a locking mechanism in accordance with the subject invention.

Figure 8A is a side view of an embodiment of a socket clamp in accordance with the subject invention.

Figure 8B is a side view of the embodiment of Figure 8A after being secured with a locking mechanism in accordance with the subject invention.

Figure 9 A is a side view of an embodiment of a rod clamp in accordance with the subject invention. Figure 9B is a side view of the embodiment of Figure 9A after being secured with a locking mechanism in accordance with the subject invention.

Figure 10Λ is a side view of an embodiment of a socket clamp in accordance with the subject invention.

Figure 1 OB is a side view of the embodiment of Figure 1 OA after being secured with a locking mechanism in accordance with the subject invention.

Figure 11 is a side view of a screw extension in accordance with the subject invention.

Figures 12 A and 12B are side views of an alternate screw extension in accordance with the subject invention.

Figures 13A and 13B are perspective views of screw and clamp assemblies in accordance with the subject invention.

DETAILED DESCRIPTION OF THE INVENTION The systems described herein are made of biocompatible material for surgical implantation such as stainless steel or titanium-based alloy. Other biocompatible materials that can be used to produce the systems of the invention are well-known to the skilled artisan.

Referring first to FIG. 2 A and FIG. 2B of the drawings, there is shown an embodiment of the lumbar fixation/stabilization system (hereinafter referred to as "the system") of the invention comprising: a multi-axial screw 10, a rod clamp 100, a socket clamp 200, and a screw extension 300 according to the present invention. The rod clamp 100 and socket clamp 200 connect a rod 400 (seen best in FIG. 4) to multi-axial screws 10. The multi-axial screw 10 is used for retaining and aligning the clamps 100, 200 and rod 400 in bone bodies, such as spinal vertebrae, in a desired spatial relationship.

In one embodiment of the invention shown in FIG. 3A, the system comprises a screw assembly having a multi-axial screw 10, indicated generally at 10, and a cap 20. The screw 10 has a stem 12 with a plurality of threads 14 and a hemispherical head 16 with a drive 18 that allows the screw 10 to be turned, or driven, into a bone body. About the hemispherical head 16 is a cap 20. Cap 20 has a skirt 22 and a clamp receiving segment 24 with a threaded segment 26. The clamp receiving segment 24 and the threaded segment 26 include the drive 18 that allows a driver to engage and turn, or drive, the screw into a bone body. The skirt 22 has an interior cavity that is hemispherical in cavity 28 to complimentarily match in size and shape with the hemispherical head 16 of the screw 10. The hemispherical head 16 is retained in the interior hemispherical cavity 28 such that the hemispherical head 16 can fully rotate within the hemispherical cavity 28 yet is unable to be released from its position within the hemispherical cavity 28. In certain embodiments, the hemispherical head 16 is permanently retained in the interior hemispherical cavity 28 while having the ability to fully rotate within the hemispherical cavity 28 as described herein. The exterior surface of the skirt 22 is tapered so that only a portion of the top of the skirt is fitted into the receiving passage 110, 210.

When a system locking mechanism 500 (seen best in FIGS. 7B, 8B, 9B, and 10B) is screwed onto threaded segment 26, the top of the tapered skirt 22 is drawn into the receiving passage 110, 210 of a clamp 100, 200. As the skirt 22 is drawn into the receiving passage 110, 210 of a clamp 100, 200, the tapered portion of the skirt is compressed and secures and locks the position of the hemispherical head 16 in the cap 20, preventing further movement of the hemispherical head 16 within the hemispherical cavity 28 within the cap 20.

In another embodiment of the invention shown in FIG. 3B, the system comprises a multi-axial screw 10, indicated generally at 10. The screw 10 has a stem 12 with a plurality of threads 14 and a hemispherical head 16 with a drive 18 that allows the screw 10 to be turned, or driven, into a bone body. About the hemispherical head 16 is a cap 20. Cap 20 has a skirt 22 and a clamp receiving segment 24 with a threaded segment 26. The clamp receiving segment 24 and the threaded segment 26 include the drive 18 that allows a driver to engage and turn, or drive, the screw into a bone body. The skirt 22 has an interior cavity that is hemispherical in shape 28 to closely match in size and shape with the hemispherical head 16 of the screw 10. The hemispherical head 16 is retained in the interior hemispherical cavity 28 such that the hemispherical head 16 can fully rotate within the hemispherical cavity 28 yet is unable to be released from its position within the hemispherical cavity 28. In certain embodiments, the hemispherical head 16 is permanently retained in the interior hemispherical cavity 28 while having the ability to fully rotate within the hemispherical cavity 28 as described herein.

The skirt 22 includes a plurality of hairpin slots 30. In one embodiment of the invention, the arms of the hairpin slot are between about 1-2 mm apart and the diameter of the head of the hairpin is between about 2-3 mm. In a preferred embodiment, the arms of the hairpin slot are 1.5 mm apart and the head of the hairpin has a diameter of 2.5 mm. When a locking mechanism 500 (seen best in FIGS. 7B, 8B, 9B, and 10B) is screwed onto threaded segment 26 over a clamp 100, 200, the top of the tapered skirt 22 is drawn into the receiving passage 110, 210. As the skirt 22 is drawn into the receiving passage 110, 210, the size of the hairpin slots 30 is reduced, namely the arms of the hairpin compress closer together; thus, the skirt 22 is compressed. The compression of skirt 22 secures and locks the position of the hemispherical head 16 in the cap 20, preventing further movement of the hemispherical head 1 within the hemispherical cavity 28 within the cap 20.

According to the subject invention, the drive 18 extends through the cap 20. The drive 18 extends through the threaded segment 26, the clamp receiving segment 24, the skirt 22. The hemispherical head 16 also includes a corresponding drive 18. This is so that a driver can engage both the cap 20 and the screw 10 via the hemispherical head 16, to screw the entire screw assembly into bone.

in another embodiment of the invention shown in FIG. 3C, the system comprises a screw assembly useful in correcting spinal deformity, spondylolisthesis, or fractures/disclocations. The screw assembly has a multi-axial screw 10, indicated generally at 10, and a cap 20. The screw 10 has a stem 12 with a plurality of threads 14 and a hemispherical head 16 with a drive 18 that allows the screw 10 to be turned, or driven, into a bone body. About the hemispherical head 16 is a cap 20. Cap 20 has a skirt 22 and a clamp receiving segment 24 with a threaded segment 26. The clamp receiving segment 24 and the threaded segment 26 include the drive 18 that allows a driver to engage and turn, or drive, the screw into a bone body.

The skirt 22 has an interior cavity that is hemispherical in cavity 28 to complimentarily match in size and shape with the hemispherical head 16 of the screw 10. The hemispherical head 16 is retained in the interior hemispherical cavity 28 such that the hemispherical head 16 can fully rotate within the hemispherical cavity 28 yet is unable to be released from its position within the hemispherical cavity 28. In certain embodiments, the hemispherical head 16 is permanently retained in the interior hemispherical cavity 28 while having the ability to fully rotate within tire hemispherical cavity 28 as described herein. The exterior surface of the skirt 22 is tapered so that only a portion of the top of the skirt is fitted into the receiving passage 110, 210. In certain embodiments, the exterior surface of skirt 22 includes a threaded segment 46. With such embodiments, a multi-axial head locking mechanism 50 is provided wherein the locking mechanism includes a threaded portion that corresponds to the threaded segment 46. When the multi-axial screw head locking mechanism 50 is screwed onto threaded segment 46, the top of the skirt 22 is compressed over the top of the hemispherical head 16, which secures and locks the position of the hemispherical head 1 in the cap 20, preventing further movement of the hemispherical head 16 within the hemispherical cavity 28 within the cap 20. According to the subject invention, a multi-axial screw⁷ head locking mechanism 50 can be used to secure and lock the position of the hemispherical head 16 in the cap 20 prior to application of a clamp 100, 200 over the clamp receiving segment 24. This provides the ability to lock the hemispherical head 16 into a monoaxial position for use in spinal deformity correction, particularly lateral deformities.

In yet another embodiment, illustrated in FIG. 3D, the system comprises a modified screw assembly also useful in correcting spinal deformity, spondylolisthesis, or fractures/disclocations. The screw assembly has a multi-axial screw 10, indicated generally at 10, and a cap 20. The screw 0 has a stem 12 with a plurality of threads 4 and a hemispherical head 16 with a drive 18 that allows the screw 10 to be turned, or driven, into a bone body. About the hemispherical head 16 is a cap 20. Cap 20 has a skirt 22 and a clamp receiving segment 24 with a break-off portion 48 designed to shear off at a predetermined torque. Preferably, break-off portion 48 includes a hollow passage that would not engage with a driver that corresponds with the drive 18. The clamp receiving segment 24 includes the drive 18 that allows a driver to engage and turn, or drive, the screw into a bone body.

The skirt 22 has an interior cavity that is hemispherical in cavity 28 to complimentarily match in size and shape with the hemispherical head 16 of the screw 10. The hemispherical head 16 is retained in the interior hemispherical cavity 28 such that the hemispherical head 16 can fully rotate within the hemispherical cavity 28 yet is unable to be released from its position within the hemispherical cavity 28. In certain embodiments, the hemispherical head 16 is permanently retained in the interior hemispherical cavity 28 while having the ability to fully rotate within the hemispherical cavity 28 as described herein. The exterior surface of the skirt 22 is tapered so that only a portion of the top of the skirt is fitted into the receiving passage 110, 210. As illustrated in FIG. 3D, the exterior surface of skirt 22 and clamp receiving segment 24 have a continuously threaded section 52. With such embodiments, a multi-axial head locking mechanism 50 is provided wherein the locking mechanism includes a threaded portion that corresponds to the threaded section 52. When the multi-axial screw head locking mechanism 50 is screwed onto and down the threaded section 52 over the top of skirt 22, the top of the skirt 22 is compressed over the top of the hemispherical head 16, which secures and locks the position of the hemispherical head 16 in the cap 20, preventing further movement of the hemispherical head 16 within the hemispherical cavity 28 within the cap 20. According to the subject invention, a multi-axial screw head locking mechanism 50 can be used to secure and lock the position of the hemispherical head 16 in the cap 20 to lock the hemispherical head 16 into a monoaxial position for use in spinal deformity correction, particularly lateral deformities. Following locking of the hemispherical head 16 into a monoaxial position with the locking mechanism 50, the break-off portion 48 is sheared off at a predetermined torque and removed.

Mechanisms known to the skilled artisan in shearing off portions via application of torque can be applied to this embodiment. In one embodiment, the screw extension 300 (such as those illustrated in FIG. 2A and 2B) is inserted into the drive 18 and a counter torque wrench may be coupled to or applied to the break-off portion 48. When the break-off portion 48 is sheared with the counter torque wrench, enough force is applied to the screw extension 300 to inhibit movement of the clamp receiving segment 24 relative to the screw assembly. In certain embodiments, the break-off portion 48 is sheared off and removed prior to placement of clamp 100, 200 over the clamp receiving segment 24. In alternate embodiments, the break-off portion 48 is sheared off and removed following placement of clamp 100, 200 over the clamp receiving segment 24.

In a method of use, the screw extension 300 illustrated in FIG. 2 A and 2B or FIG. 11 is used with the modified screw assembly illustrated in FIG. 3D. The driver 302 is inserted into the drive 18 and a clamp 100, 200 is slid down over the extension 300 onto the continuously threaded section 52. When the clamp 100, 200 is reluctant to traverse down onto the clamp receiving segment 24, engaging a multi-axial head locking mechanism 50 with the continuously threaded section 52 ultimately forces the reluctant clamp 100, 200 onto the clamp receiving segment 24. Enabling a multi-axial head locking mechanism 50 to assist clamp positioning on the clamp receiving segment 24 provides the clinician with an embodiment: to correct spinal deformity, spondylolisthesis, or fractures/disclocations. In such cases, force will normally be required to contour the abnormal anatomy using the systems of the invention.

In one embodiment, illustrated in FIG. 2A. FIG. 2B. and FI . 2C, the screw extension 300 includes a driver 302 that is inserted into the drive 18. In a related embodiment, the driver 302 is of a corresponding shape to that of the drive 18 so as to engage the drive 18 when the extension 300 is turned to drive the screw assembly into the bone. In another related embodiment, the screw extension 300 includes a spring bias 304 that enables the user to easily disengage the driver 302 from the hemispherical head 16 without dislodging the driver 302 from the cap 20. The pressure bias 304 biases the screw engaging driver 302 in a direction apart from the hemispherical screw head drive while ensuring the screw driver engaging portion 302 maintains contact with the clamp receiving segment 24 and the threaded segment 26 when there is no pressure placed on the driver/extension 300 into the drive 18 of the screw 10. In one embodiment, the pressure bias 304 is a spring. This embodiment enables the clinician, following screwing the screw assembly into bone, to place the clamp/rod assembly over the screw 10 and to position not only the rod/clamp assembly but also the angle of the screw head 16, 22 as desired before securing the entire system with the locking mechanism 500.

The drive 18 is a slot in the shape of any of a wide variety of known drive designs employed with screws. Examples of drives that can form the drive 18 of the invention include, but are not limited to, threaded for receiving a corresponding threaded driver (as illustrated in FIG. 2C); slot shaped (single slot and is driven by a flat-bladed driver); cross- head, cross-point, or cruciform shaped (cross-shaped slot such as a Phillips cross-head, JIS, french recess or BNAE NFL22-070, and the like); torx (star-shaped hexalobuiar drive with six rounded points such as T, I S. TX); hexagonal shaped (hexagonal shaped slot and is driven by a hex wrench or alien key or hex key); Robertson shaped (square shaped slot); tri- wing shaped (triangular slot); torq-set or offset cruciform shaped; spanner shaped (two round holes opposite each other); and clutch type shaped (bow tie slot or butterfly slot). In one embodiment, the drive 18 is threaded (male) and the driver 302 has corresponding threads (female) for engaging the drive 18. Preferably, the drive 18 is one that fits a hexagonal cross- section shaped driver or start cross-section shaped driver. FIGS. 2A and 2B illustrate a screw extension 300 that includes a driver 302 that is of a corresponding shape to that of a cross-head drive 18.

The clamp receiving segment 24 is preferably cylindrical in shape with a circular cross section. However, other embodiments contemplated herein include a clamp receiving segment 24 having a square or rectangular cross section, a triangular cross section, a pentagram cross-section; a hexagonal cross section; and any other cross section shape that would enable a clamp 100, 200 of the invention to be securely received atop a screw 10. Preferably, the height of the clamp receiving segment 24 is of the same or slightly shorter than the length of the receiving passage 110, 210 of the clamp 100, 200 so that when a locking mechanism 500 is screwed over the threaded segment 26, the clamp 100, 200 is securely fastened atop the screw 10, the rod 400 within the clamp is securely locked into position, and the clamp 100, 200 compresses the cap 20 to lock the desired angle position of the hemispherical screw head 16 within the cap 20.

FIG. 4 shows a rod assembly for use with a clamp 100, 200 of the invention. The rod assembly comprises a rod, indicated generally as 400, a ball-shaped rod head 402, and a slippage preventing means 404. The ball-shaped rod head 402 is of a shape and size to fit loosely within the semispherical recess 202 of a socket clamp 200 when the two branches 204a, 204b (seen best in FIG. 6A) are not compressed together. The ball-shaped rod head 402 can have a diameter between 4-12 mm, more preferably between about 6-7 mm. However, when the two branches 204a, 204b are forced together, such as when a locking mechanism 500 is secured over the clamp 200 onto a threaded segment 26 of the screw cap 20, the ball -shaped rod head 402 is locked into position and cannot move within the semispherical recess 202.

The rod 400 has a connecting member 406 of sufficient diameter to resist the stresses and loads of the spine. According to the subject invention, the connecting member 406 can have a diameter between about 3-10 mm, more preferably between about 4-8 mm, and even more preferably between about 5-6 mm. The connecting member 406 can be straight or curved to match the deformation or anatomy of the spine. In certain embodiments, the connecting member 406 is straight but can be forcibly curved by the clinician to attain some degree of curvature matching the deformation or anatomy of the spine. The connecting member 406 can have a smooth surface or a rough surface. The connecting member 406 can have a circular cross section; however, other embodiments contemplated herein include a connecting member 406 having an oval cross section, a square or rectangular cross section (such as with plates), a triangular cross section, a pentagram cross-section; a hexagonal cross section; and any other cross section shape that would enable the rod 400 of the invention to be securely received within a clamp 100.

The connecting member 406 preferably has a diameter sized to fit loosely within the rod passage 102 of a rod clamp 1 0 when the two branches 104a, 104b (seen best in FIG. 5A) are not compressed together. However, when the two branches 104a, 104b are forced together, such as when a locking mechanism 500 is secured over the clamp 100 onto a threaded segment 26 of the screw cap 20, the rod connecting member 406 is locked into position in relation with the screw 10 and cannot move within the rod passage 102.

FIG. 5A shows the disassembled parts of a rod clamp 100 in accordance with the subject invention. The rod clamp 100 comprises two branches 104a, 104b that are inseparably linked. The upper branch 104a has a channel 106 with lower branch 104b engaging ledge 108. The lower branch 104b has an engaging body 124 that includes opposing ledge 112. According to the subject invention, the two branches 104a, 104b are inseparably linked (best illustrated in FIGS. 5B, 5C, 5D, and 5E) via assembly of engaging body 124 within channel 106 as shown in FIGS. 5B, 5C, 5D, and 5E. Due to the inability of ledge 108 to disengage from opposing ledge 112, rod clamp 100 comprises parts that are inseparably linked to form a unitary structure. Further, because the ledge 108 cannot disengage from opposing ledge 112, lower branch 104b can be moved toward or away from upper branch 104a. When the two branches 104a. 104b are forced together, such as when a locking mechanism 500 is secured over the clamp 100 onto a threaded segment 26 of the screw cap 20, the two branches 104a, 104b come into contact to clampingly engage or friction-lock rod connecting member 406 to screw 10, wherein the rod cannot move within the rod passage 102 formed by the branches 104a, 104b.

As shown in FIGS. 5A-5C, the lower branch 104b also includes a receiving passage 110 that extends entirely through branch 104b, between upper surface 114 and lower surface 116. The receiving passage 110 preferably has a cross-section similar to the cross section of extension 300, threaded segment 26, and clamp receiving segment 24. For example, the cross-section may be generally circular, but optionally may be noncircular (e.g. , having a geometric shape similar in cross section to extension 300, threaded segment 26, and clamp receiving segment 24 including noncircular with one or more flattened walls, oval, square, triangular, and the like). Thus, the receiving passage 110 may accommodate receiving therethrough an extension 300, a threaded segment 26, and a clamp receiving segment 24.

In addition, the upper and lower branches 104a, 104 b have generally hemi-cylindrical grooves 118, 120 therein that cooperate with one another when the rod clamp 100 is assembled to define a rod passage 102 as shown in FIGS. 5B, .5C and 5D. The rod passage 102 generally extends along an axis substantially perpendicular to the axis 122 along which the receiving passage 110 extends. Λ rod 400 may generally be received within the rod passage 102. The rod passage 102 has a cross-section similar to a connecting member 406 of a rod 400. For example, the cross-section may be generally circular, but optionally may be noncircular (e.g. , circular with one or more flattened walls, oval, square, triangular, and the like). In a further alternative, one or both grooves 118, 120 may include teeth or other serrations for enhancing engagement with the connecting member 406 received in the rod passage 102. Exemplary serrations are shown in U.S. Patent Nos. 4,653,481 and 5,545, 164; the disclosures of which are expressly incorporated herein by reference.

FIG. 6A shows the disassembled parts of a socket clamp 200 in accordance with the subject invention. The socket clamp 200 comprises two branches 204a, 204b that are inseparably linked. The upper branch 204a has a channel 206 with lower branch 204b engaging ledge 208. The lower branch 204b has an engaging body 224 that includes opposing ledge 212. According to the subject invention, the two branches 204a, 204b are inseparably linked (best illustrated in FIGS. 613. 6C. 6D, and 6E) via assembly of engaging body 224 within channel 206 as shown in FIGS. 6B, 6C, 61). and 6E. Due to the inability of ledge 208 to disengage from opposing ledge 212, socket clamp 200 comprises parts that are inseparably linked to form a unitary structure. Further, because the ledge 208 cannot disengage from opposing ledge 212, lower branch 204b can be moved toward or away from upper branch 204a. When the two branches 204a, 204b are forced together, such as when a locking mechanism 500 is secured over the clamp 200 onto a threaded segment 26 of the screw cap 20, the two branches 204a, 204b come into contact to clampingly engage or friction-lock ball-shaped rod head 402 to screw 10, wherein the rod head 402 cannot move within the semispherical recess 202 formed by the branches 204a, 204b.

As shown in FIGS. 6A-6C, the lower branch 204b also includes a receiving passage

210 that extends entirely through the branch 204b. between upper surface 214 and lower surface 216. The receiving passage 210 preferably has a cross-section similar to the cross section of extension 300, threaded segment 26, and clamp receiving segment 24. For example, the cross-section may be generally circular, but optionally may be noncircular (e.g. , having a geometric shape similar in cross section to extension 300, threaded segment 26. and clamp receiving segment 24 including noncircular with one or more flattened walls, oval, square, triangular, and the like). Thus, the receiving passage 210 may accommodate receiving therethrough an extension 300, a threaded segment 26, and a clamp receiving segment 24.

In addition, the upper and lower branches 204a, 204b have generally semispherical grooves or cups 218, 220 therein that cooperate with one another to form a semispherical recess or depression 202 within which a ball-shaped rod head 402 fits when the socket clamp 200 is assembled as shown in FIGS. 6B, 6C and 6D. The hemispherical recess 202 generally resides within the assembled socket clamp 200 and includes an opening 222 through which the rod 400 traverses. The semispherical recess 202 enables the rod 400 to obtain motion around an indefinite number of axes, which have one common center, within the ball-shaped rod head 402. For example, the socket clamp 200 may enable the rod 400 to maneuver with about 120° spherical motion in relation to the pedicle screw 10 until locked into a position by the user. In a further alternative, one or both grooves 218, 220 may include teeth or other serrations for enhancing engagement with the ball-shaped rod head 402 received within the semispherical recess 202.

In one embodiment, as best illustrated in FIGS. 2A and 2B, clamps 100, 200 have tapered arms 104a. b and 204a. b, respectively, to ensure a smaller footprint within the patient following installment.

Referring to FIGS. 7A and 7B, an alternate embodiment of a rod clamp 600 is illustrated. Rather than inseparably linking two independent branches together (see, for example, FIG. 5B), rod clamp 600 is of a single, unitary structure, wherein upper branch 604a and lower branch 604b are united at connecting section 602. The rod clamp 600, by virtue of having two connected branches 604a, 604b along the connecting section 602 is provided with a straight through slot 606. The straight through slot 606 between branches 604a and 604b is equidistant along its entire length.

As shown in FIG. 7 A. the upper branch 604a and lower branch 604b include a receiving passage 608 that extends entirely through both branches 104a, 104b, between upper surface 618 and lower surface 620. The receiving passage 608 preferably has a cross-section similar to the cross section of extension 300, threaded segment 26, and clamp receiving segment 24. For example, the cross-section may be generally circular, but optionally may be noncircular (e.g. , having a geometric shape similar in cross section to extension 300, threaded segment 26, and clamp receiving segment 24 including noncircular with one or more flattened walls, oval, square, triangular, and the like). Thus, the receiving passage 608 may accommodate receiving therethrough an extension 300, a threaded segment 26, and a clamp receiving segment 24.

In addition, the upper and lower branches 604a. 604b have generally hemi-cylindrical grooves 612. 614 therein that cooperate with one another to form a rod passage 610 for receiving a rod 400. The rod passage 610 generally extends along an axis substantially perpendicular to the axis 616 along which the receiving passage 608 extends. The rod passage 610 has a cross-section similar to a connecting member 406 of a rod 400. For example, the cross-section may be generally circular, but optionally may be noncircular (e.g. , circular with one or more flattened walls, oval, square, triangular, and the like). In certain embodiments, one or both grooves 612. 614 may include teeth or other serrations for enhancing engagement and locking of the connecting member 406 in the rod passage 610. Exemplary serrations are shown in U.S. Patent Nos. 4,653,481 and 5,545, 164; the disclosures of which are expressly incorporated herein by reference.

As illustrated in FIG. 7B. when screwing a nut 500 or other locking mechanism onto the threaded segment 26, upper branch 604a and lower branch 604b of the clamp 600 are pressed together which, in turn, compresses the slot 606 as well as rod passage 610 about a connecting member 406 of a rod 400. This assures excellent quality and secure locking of the position of the rod 400 over the screw 10.

Referring to FIGS. 8A and 813, an alternate embodiment of a socket clamp 700 is illustrated. Rather than inseparably linking two independent branches together (see, for example, FIG. 6B), socket clamp 700 is of a single, unitary structure, wherein upper branch 704a and lower branch 704b are united at connecting section 702. The socket clamp 700, by virtue of having two connected branches 704a, 704b along the connecting section 702 is provided with a straight through slot 706. The straight through slot 706 between branches 604a and 604b is equidistant along its entire length.

As shown in FIG. 8A. the upper branch 704a and lower branch 704b include a receiving passage 608 that extends entirely through both branches 704a, 704b. between upper surface 718 and lower surface 720. The receiving passage 708 preferably has a cross-section similar to the cross section of extension 300, threaded segment 26, and clamp receiving segment 24. For example, the cross-section may be generally circular, but optionally may be noncircular (e.g. , having a geometric shape similar in. cross section to extension 300, threaded segment 26, and clamp receiving segment 24 including noncircular with one or more flattened walls, oval, square, triangular, and the like). Thus, the receiving passage 708 may accommodate receiving therethrough an extension 300, a threaded segment 26, and a clamp receiving segment 24.

In addition, the upper and lower branches 704a, 704b have generally semispherical grooves or cups 712, 714 therein that cooperate with one another to form a hemispherical recess or depression 710 within which a ball-shaped rod head 402 fits. The hemispherical recess 710 generally resides within the socket clamp 700 and includes an opening 722 through which the rod 400 traverses. The hemispherical recess 710 enables the rod 400 to obtain motion around an indefinite number of axes, which have one common center, within the ball-shaped rod head 710. For example, the socket clamp 700 may enable the rod 400 to maneuver with about 1 20° spherical motion in relation to the pedicle screw 10 until locked into a position by the user. In a further alternative, one or both grooves 712, 714 may include teeth or other serrations for enhancing engagement with the ball-shaped rod head 402 received within the hemispherical recess 710.

As shown in FIG. 8B, when screwing a nut 500 or other locking mechanism onto the threaded segment 26. upper branch 704a and lower branch 704b of the clamp 700 are pressed together which, in turn, compresses the slot 706 as well as rod passage 710 about a connecting member 406 of a rod 400. This assures locking of excellent quality.

Referring to FIGS. 9 A and 9B, an alternate embodiment of a rod clamp 800 is illustrated. Rather than inseparably linking two independent branches together (see, for example, FIG. 5B), rod clamp 800 is of a single, unitary structure, wherein upper branch 804a and lower branch 804b are united at connecting section 802. The rod clamp 800, by virtue of having two connected branches 804a, 804b along the connecting section 802, is provided with a through slot 806. The slot 806 has a greater distance between upper branch 804a and lower branch 804b at the rod passage 810 than that distance between the branches 804a, 804b at the receiving passage 808. As shown in FIG. 9A, the upper branch 804a and lower branch 804b include a receiving passage 808 that extends entirely through both branches 104a, 1 4b, between upper surface 818 and lower surface 820. The receiving passage 808 preferably has a cross-section similar to the cross section of extension 300, threaded segment 26, and clamp receiving segment 24. For example, the cross-section may be generally circular, but optionally may be noncircular (e.g., having a geometric shape similar in cross section to extension 300, threaded segment 26, and clamp receiving segment 24 including noncircular with one or more flattened walls, oval, square, triangular, and the like). Thus, the receiving passage 808 may accommodate receiving therethrough an extension 300, a threaded segment 26, and a clamp receiving segment 24.

In addition, the upper and lower branches 804a, 804b have generally hemi-cylindrical grooves 812, 814 therein that cooperate with one another to form a rod passage 810 for receiving a rod 400. The rod passage 810 generally extends along an axis substantially perpendicular to the axis 816 along which the receiving passage 808 extends. The rod passage 810 has a cross-section similar to a connecting member 406 of a rod 400. For example, the cross-section may be generally circular, but optionally may be noncircular (e.g., circular with one or more flattened walls, oval, square, triangular, and the like). In certain embodiments, one or both grooves 812, 814 may include teeth or other serrations for enhancing engagement and locking of the connecting member 406 in the rod passage 810. Exemplary serrations are shown in U.S. Patent Nos. 4,653,481 and 5,545, 164; the disclosures of which are expressly incorporated herein by reference.

As shown in FIG. 9B, when screwing a nut 500 or other locking mechanism onto the threaded segment 26, upper branch 804a and lower branch 804b of the clamp 800 are pressed together which, in turn, compresses the slot 806 as well as rod passage 810 about a connecting member 406 of a rod 400. This assures locking of excellent quality.

Referring to FIGS. 10A and 10B, an alternate embodiment of a socket clamp 900 is illustrated. Rather than inseparably linking two independent branches together (see, for example, FIG. 6B), socket clamp 900 is of a unitary structure, wherein upper branch 904a and lower branch 904b are united at connecting section 902. The socket clamp 900, by virtue of having two connected branches 904a, 904b along the connecting section 902 is provided with a straight through slot 906. The straight through slot 906 between branches 904a and 904b has a greater distance between upper branch 904a and lower branch 904b at the hemispherical depression 910 than the distance between the branches 904a, 904b at receiving passage 908.

As shown in FIG. 10A, the upper branch 904a and lower branch 904b include a receiving passage 908 that extends entirely through both branches 904a, 904b. between upper surface 918 and lower surface 920. The receiving passage 908 preferably has a cross-section similar to the cross section of extension 300, threaded segment 26, and clamp receiving segment 24. For example, the cross-section may be generally circular, but optionally may be noncircular (e.g., having a geometric shape similar in cross section to extension 300, threaded segment 26, and clamp receiving segment 24 including noncircular with one or more flattened walls, oval, square, triangular, and the like). Thus, the receiving passage 908 may accommodate receiving therethrough an extension 300, a threaded segment 26, and a clamp receiving segment 24.

In addition, the upper and lower branches 904a, 904b have generally semispherical grooves or cups 912, 914 therein that cooperate with one another to form a hemispherical recess or depression 910 within which a ball-shaped rod head 402 fits. The hemispherical recess 910 generally resides within the socket clamp 900 and includes an opening 922 through which the rod 400 traverses. The hemispherical recess 910 enables the rod 400 to obtain motion around an indefinite number of axes, which have one common center, within the ball-shaped rod head 910. For example, the socket clamp 900 may enable the rod 400 to maneuver with 120° in relation to the pedicle screw 10 until locked into a position by the user. In a further alternative, one or both grooves 912, 914 may include teeth or other serrations for enhancing engagement with the ball-shaped rod head 402 received within the hemispherical recess 910.

As shown in FIG. 10B, when screwing a nut 500 or other lockin mechanism onto the threaded segment 26, upper branch 904a and lower branch 904b of the clamp 900 are pressed together which, in turn, compresses the slot 906 as well as rod passage 910 about a connecting member 406 of a rod 400. This assures locking of excellent quality.

FIG. 11 illustrates one embodiment of a screw extension 300 that includes an extension body 306, a driver 302 and a male threaded section 314. The extension body 306 has a cross section that has the same (as best illustrated in FIG. 11) or smaller diameter (as best illustrated in FIGS. 2 A and 2B) than the threaded segment 26. In certain embodiments, the diameter of the extension body 306 can change along the length of the extension body 306. In one related embodiment, the diameter of the extension body 306 can taper from being the same diameter down to a lesser diameter than that of the threaded segment 26 (as seen best in FIGS. 2 A and 2B). Such embodiments enable a locking mechanism 500 to easily slide over the extension body 306 to engage the threaded segment 26 as described herein. Further, such embodiments enable a multi-axial head locking mechanism 50 to be easily applied to the extension 300 as described herein in securing the multi-axial head locking mechanism 50 over the continuously threaded section 52 of a modified screw assembly useful in correcting spinal deformity, spondylolisthesis, or fractures/disclocations.

In an alternate embodiment, the diameter of the extension body 306 can taper in an opposite direction, where a smaller diameter is provided proximal the user and the diameter of the extension body widens along its length progressively toward the driver 302. such that the cross section of the extension body 306 is the same or smaller in diameter as that of the threaded segment 26 at its most distal point from the user. This embodiment enables a locking mechanism 500 to be easily applied to the extension 300 as described herein while ensuring more facile manipulation in securing the locking mechanism 500 in place over the system as the locking mechanism 500 comes into contact with the threaded segment 26. Further, this embodiment enables a multi-axial head locking mechanism 50 to be easily applied to the extension 300 as described herein in securing the multi-axial head locking mechanism 50 over the continuously threaded section 52 of a modified screw assembly useful in correcting spinal deformity, spondylolisthesis, or fractures/disclocations.

In one embodiment, the threaded segment 26 of the clamp receiving segment 24 includes an internal female threaded section 32 (as seen best in FIG. 13A) to receive a corresponding male threaded section 314 on an extension 300 (as seen best in FIG. 11). With this embodiment, the extension driver 302 is moveable and can be removed from the hemispherical head 16 and/or extension body 306 following seating of the screw 10 into bone and screwing of the male threaded section 314 into the female threaded section 32 within the threaded segment 26 of the clamp receiving segment 24. This embodiment provides the user with more secure connection between the extension 300 and the cap 20 and also the ability to manipulate the cap 20 following dislocation of the driver 302 from the drive 18 in the hemispherical head 16.

An alternative embodiment of the screw extension 300 is illustrated in FIGS. 12A and 12B. The screw extension 300 includes a moveable and/or removable driver 302 and a mechanism for applying torque 310 to the driver 302. The mechanism for applying torque 310 can be operatively and removeably connected to the driver 302 when the driver 302 is in a "down" position as seen best in FIG. 12A and/or when the driver 302 is in an "up" position as seen best in FIG. 12B.

When in the "down" position, the driver 302 preferably engages the screw drive 18 in the hemispherical head 16 following screwing the male threaded section 314 into the female threaded section 32 of the cap 20. This enables the user to use the screw extension 300 to drive a screw 10 into bone. The mechanism for applying torque 310 can be attached or secured to the top 312 of the moveable driver 302 to assist in providing torque to and rotating the driver 302 to seat the screw 10 into bone. In certain embodiments, the mechanism for applying torque 310 is in the form of a handle, a handle arm, a wrench arm, or the like. When the mechanism for applying torque 310 is attached and the moveable driver 302 is in the down potion, the extension 300 has the ability to drive a screw 10 into vertebra.

When the user wishes to disengage the driver 302 from the screw drive 18, the moveable driver 302 can be moved into the "up" position (see FIG. 12B) and, in certain embodiments, removed from the extension body 302 altogether, while the male threaded section 314 keeps the extension body 300 secured to the cap 20. This enables the user, following securing the screw 10 into bone, to continue to have the ability to maintain connection with and manipulate the angle of the cap 20 as desired. The mechanism for applying torque 310 can be used to assist in moving the moveable driver 302 to and from the up and the down positions. Following seating of a screw 10 into bone, the mechanism for applying torque 310 can be removed from the driver 302 so as to facilitate sliding of a rod/clamp system and locking mechanism over extension body 306 into place over screw(s) 10 in a failsafe and side-loading manner.

In one exemplary method of using the lumbar stabilization/fixation system of the present invention comprises initially prepping and draping the surgical site. One exemplary approach, and not meant to be limiting, uses a posterior lateral approach that may substantially comprise a Wiltse approach. In this aspect, a muscle-splitting finger dissection approach can be used to gain access to the desired anatomical location in the spine, which are generally adjacent the pedicles of the vertebra of interest. Once the pedicles are exposed, they can be conventionally prepped. Next, At least one multi-axial screw, preferably a plurality of multi-axial screws of the invention, can be driven into the exposed pedicles in predetermined locations along a patient's spinal column with a drive tool, preferably using a screw extension of the invention. In one aspect, it is contemplated that the insertion of the pedicle screws can be guided and/or monitored by fluoroscopy or other conventional imaging techniques. In another aspect, the entire system, screws 10, clamps 100, 200, and extensions 300, are cannulated to accommodate a guidewire so that the screws can be placed over a guidewire for insertion. It is further contemplated that a conventional awl can be used to form alignment bores in the bones prior to the insertion and driving of the pedicle screws thereinto the bone.

Following driving the screw(s) into the pedicle(s) using extension(s) of the invention, the screw drive engaging portion of the extension is released from the screw drive (such as via a return spring for biasing the screw engaging drive in a direction apart from the hemispherical screw head drive) so as to enable multi-axial movement of the screw head while maintaining connection with the extension via the clamp engaging segment of the screw. Thus, the proximal end portion of each extension extends posterior to the skin of the patient.

Next, a rod of the invention is mounted to at least one socket clamp, preferably a socket clamp and a rod clamp or any other combination of the two, to form a rod/clamp system. The rod clamp system is then mounted on the screw extension(s) and slid down the extcnsion(s) until the clamp(s) are operatively engaged with the clamp engaging segment(s) of the screw(s).

Locking mechanism(s), such as bolts, can then be slideably mounted onto the proximal end(s) of the of extension(s) and slid down the respective extension rods into contact with the threaded portions of the clamp engaging segment(s) of the pedicle screw(s). If desired, the rod and/or multi-axial screw head(s) can be manipulated to position the rod as desired for optimal therapeutic effect. Once the position of the rod and/or multi-axial screw head(s) are in desired position, the locking mechanism(s) are secured. Subsequently, the extcnsion(s) are removed from the pedicle screvv(s).

An illustration of an assembled screw 10 and clamp 200 in accordance with the invention is provided in FIG. 13A and FIG. 13B illustrates an assembled screw 10 and clamp 100. According to the subject invention, the angle of the head of the screw 16, the clamp 100, 200, and the rod 400 are locked into a desirable position by a single mechanism (via screwing the locking mechanism 500 onto threaded segment 26). This is particularly advantageous in that very little manipulation is needed by the clinician following insertion of a multi-axial screw of the invention into a bone. The user is assured failsafe positioning of the rod to the screws (without additional fluoroscopy needed) via sliding of a rod/clamp system over the extension(s) onto the screw(s). Once in place, positioning of the rod in relation to the screw(s) and bone(s) can be accomplished by maneuvering these parts with the extension(s) in place. Securing and locking of the pails in desirous positions is easily and quickly accomplished by merely sliding a locking mechanism over the extension(s) onto the threaded portion and engaging the locking mechanisms thereto.

In addition to ease of use, the subject system is safer than those of the prior art. In designs in which more than one mechanism is necessary to secure the rod, the clamp, and the screw into position, additional steps are imposed on the clinician along with additional possible missteps and destabilization of the system should any one of the mechanisms fail to be properly secured. By providing a single locking mechanism for securing and locking the system, the use of fluoroscopy is minimized while less time is needed to conduct the procedure. Further, this enables the user to perform minimally invasive procedures. Finally, the profile of the system in the patient is smaller than those in which more than one locking mechanism is needed.

in one technique, the underlying bone forms a portion of a vertebral body of the spinal column. The underlying bone can be a part of the anterior, oblique, antero-lateral, lateral or posterior vertebral elements, including the pedicle, spinous process, transverse processes, lamina or facet, for example. Applications in techniques along any portion or portions of the spinal column are contemplated, including the cervical, thoracic, lumbar and sacral regions. The connector assemblies, implants and elongate members can be positioned along the spinal column in invasive procedures where skin and tissue are dissected and retracted to expose the implant locations, or in minimally invasive procedures where one or more of the connector assemblies, elongate members and/or implants are guided through at least the tissue or access portals adjacent the column to the desired implantation location.

According to the subject invention, the disclosed systems and methods for stabilizing and/or fixating lumbar vertebrae can be used for any of the following conditions: degenerative disc disease; spondylolisthesis; deformities or curvatures of the spine including, but not limited to, scoliosis, kyphosis, lordosis, and Scheuermann's disease, trauma including but not limited to fracture or dislocation of vertebrae, cancer, stenosis, pseudoarthrosis, and failed previous fusion.

All patents, patent applications, provisional applications, and publications referred to or cited herein, supra or infra, are incorporated by reference in their entirety, including all figures and tables, to the extent they are not inconsistent with the explicit teachings of this specification.

It should be understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application.

Claims

CLAIMS I claim:

1. A lumbar system comprising: at least one screw assembly comprising a mult-axial pedicle screw; at least one screw extension having at one end a driver for detachably insertion into the screw; a support rod having at one end a ball-shaped rod head; and a socket clamp receivable on the screw via the screw extension; wherein the socket clamp is a unitary, inseparable structure that includes both a screw engaging portion and a socket having a hemispherical recess to receive the support rod ball-shaped head, and wherein the socket clamp comprises two branches, an upper and lower branch, that together define the hemispherical recess within which the rod ball shaped head is disposed.

2. The lumbar system of claim 1, wherein the upper and lower branches are inseparably linked by a connecting area, wherein the connecting area defines a screw receiving portion comprising a passage for receiving the extension and the clamp engaging segment of the screw.

3. The lumbar system of claim 2, wherein the passage for receiving the screw extension and clamp engaging segment is transversely oriented to the upper and lower branches.

4. The lumbar system of claim 1, wherein the socket clamp enables the rod to obtain about 120 degree spherical motion in relation to the pedicle screw.

5. The lumbar system of claim 1 further comprising multiple pedicle screws and multiple screw extensions.

6. The lumbar system of claim 1 further comprising a locking mechanism for the multi- axial pedicle screw.

7. The lumbar system of claim 6, wherein the locking mechanism is a nut.

8. The lumbar system of claim 1 further comprising a rod clamp.

9. The lumbar system of claim 7, wherein the rod further comprises a means for preventing the rod from slipping out of the rod engaging portion of the rod clamp.

10. The lumbar system of claim 1 , wherein the screw assembly comprises a cap and the pedicle screw comprises a stem with a plurality of threads and a hemispherical head with a drive, wherein the cap the is situated about the hemispherical head.

1 1. The lumbar system of claim 10, wherein the cap comprises a skirt that has an interior cavity that is hemispherical in shape to match the hemispherical head and has a plurality of hairpin slots.

12. A method for lumbar stabilization or fixation comprising: (a) inserting a lumbar system into at least one pedicle of a patient's spinal column, wherein the lumbar system comprises at least one screw assembly comprising a mult-axial pedicle screw comprising a hemispherical head and a cap having a skirt and a clamp receiving segment with a continuously threaded section; at least one screw extension having at one end a driver for detachably insertion into the screw; a support rod having at one end a ball-shaped rod head; and a socket clamp receivable on the screw via the screw extension; wherein the socket clamp is a unitary, inseparable structure that includes both a screw engaging portion and a socket having a hemispherical recess to receive the support rod ball-shaped head, and wherein the socket clamp comprises two branches, an upper and lower branch, that together define the hemispherical recess within which the rod ball shaped head is disposed; (b) inserting the screw extension into the screw assembly and driving the screw into the pedicle(s); (c) sliding a clamp down over the screw extension onto the continuously threaded section of the clamp receiving segment; (d) mounting at least one rod to at least one socket clamp to form a rod clamp assembly; (e) mounting the rod assembly onto the screw extension(s); (f) sliding the rod assembly down the extension(s) until the clamp(s) are operatively engaged with the clamp receiving segment(s); mounting and sliding down the extension(s) locking mechanism(s) over the clamp receiving segment(s) and positioning the rod assembly(ies) as desired; (g) securing the locking mechanism(s) over the clamp receiving segment(s); and (h) removing the extension(s) from the pedicle screw(s).

13. The method of claim 12, wherein the upper and lower branches of the socket clamp arc inseparably linked by a connecting area, wherein the connecting area defines a screw receiving portion comprising a passage for receiving the extension and the clamp engaging segment of the screw.

14. The method of claim 13, wherein the passage for receiving the screw extension and clamp engaging segment is transversely oriented to the upper and lower branches.

15. The method of claim 12, wherein the socket clamp enables the rod to obtain about 120 degree spherical motion in relation to the pedicle screw.

16. The method of claim 12, wherein the lumbar system further comprises multiple pedicle screws and multiple screw extensions.

17. The method of claim 12, wherein the locking mechanism is a nut.

18. The method of claim 12, wherein the the rod further comprises a means for preventing the rod from slipping out of the rod engaging portion of the rod clamp.

19. The method of claim 12, wherein the cap is situated about the hemispherical head.

20. The method of claim 19, wherein the skirt of the cap has a plurality of hairpin slots.

21. A method for correcting spinal deformity, spondylolisthesis, fractures, or dislocations comprising: (a) inserting a lumbar system into at least one pedicle of a patient's spinal column, wherein the lumbar system comprises at least one screw assembly comprising a mult-axial pedicle screw and a cap having a skirt and a clamp receiving segment with a continuously threaded section and a break-off portion designed to shear off at a predetermined torque; at least one screw extension having at one end a driver for detachablv insertion into the screw; a support rod having at one end a ball-shaped rod head; and a socket clamp receivable on the screw via the screw extension; wherein the socket clamp is a unitary, inseparable structure that includes both a screw engaging portion and a socket having a hemispherical recess to receive the support rod ball-shaped head, and wherein the socket clamp comprises two branches, an upper and lower branch, that together define the hemispherical recess within which the rod ball shaped head is disposed; (b) inserting the screw extension into the screw assembly and driving the screw into at least one pedicle; (c) sliding a clamp down over the screw extension onto the continuously threaded section of the clamp receiving segment; (d) if the clamp is reluctant to traverse down the clamp receiving segment in step (c), engaging a multi-axial head locking mechanism with the continuously threaded segment to force the reluctant clamp onto the clamp receiving segment to enable a multi-axial head locking mechanism to assist in clamp positioning on the clamp receiving segment; (e) mounting at least one rod to at least one socket clamp to form a rod clamp assembly; (f) mounting the rod assembly onto the screw extension(s); (g) sliding the rod assembly down the extension(s) until the clamp(s) are operatively engaged with the clamp receiving segment(s); mounting and sliding down the extension(s) locking mechanism(s) over the clamp receiving segment(s) and positioning the rod assembly(ies) as desired; (h) securing the locking mechanism(s) over the clamp receiving segment(s); and (i) removing the extension(s) from the pedicle screw(s).