Patent ID: 12251141

DETAILED DESCRIPTION OF THE DISCLOSURE

The present disclosure features a vertebral body manipulation device that is simpler, smaller, and provides more degrees of freedom (DoF) of movement than currently available instrumentation. The vertebral body manipulation device of the present disclosure is based, at least in part, on the discovery that incorporating both a threaded connection joint and a smooth connection joint into a scissor mechanism having an X configuration may provide a module having one DoF of maneuverability in and of itself. Moreover, the vertebral body manipulation device of the present disclosure may provide five or six DoF of maneuverability relative to the heads of the vertebral anchors to which it is attached when used in pairs of two or more devices. Advantageously, the present device provides two pin connection joints within the scissor mechanism having an X configuration that may be connected directly to quick-lock mechanisms configured to mate with a screw extension and/or vertebral anchor, which provides a more compact design that also has the benefit of keeping the heads of the vertebral anchors (e.g., pedicle screws) aligned and thereby facilitates placement of a rod. The heads of the screws are oriented towards one another and at the same level which guarantees the placement of a straight rod over the heads, without the need to profile or adjust it. Additionally, the threaded connection joint reduces internal friction of the mechanism, thereby enhancing the force-feedback of the device and providing the surgeon with a better representation of the forces exerted by the device on the vertebral bodies.

Abnormal curvature of the spine is referred to as spinal deformity, one of the oldest and most common diseases [Heary R F, Madhavan K:Neurosurgery. September 2008; Vol. 63(3 Suppl) pp. 5-15]. The causes of spinal deformity are numerous and may include congenital, degenerative, neoplastic, infectious, traumatic, iatrogenic and idiopathic etiologies [Watters W C, et al.,Spine J. July 2009; Vol. 9(7) pp. 609-614]. Spondylolisthesis is a form of spinal deformity commonly associated with degenerative spondylosis. The deformity usually occurs in the lumbar and sacral regions of the spine and may affect sagittal balance [Barrey C, et al.,European Spine Journal. September 2007; Vol. 16(9) pp. 1459-1467, El-Rich M A C, et al.Stud Health Technol Inform.2006; Vol. 123 pp. 341-344, Labelle H, et al.,Spine(Phila Pa 1976). Mar. 15, 2005; Vol. 30(6 Suppl) pp. S27-34, and Barrey C, et al.,Eur Spine J. September 2007; Vol. 16(9) pp. 1459-1467]. Spondylolisthesis is the anterior subluxation of one vertebral body on another, usually L5 on S1, or L4 on L5. Spinal deformity, including scoliosis, occurs frequently and may be as high as 68% in elderly populations [Ailon T, et al.,Neurosurgery. October 2015; Vol. 77 Suppl 4 pp. S75-91]. Spondylolisthesis occurs in about 5.8% of men and 9.1% of women, with many cases being asymptomatic [Ettinger B, et al.,J Bone Miner Res. April 1992; Vol. 7(4) pp. 449-456 and Schwab F, et al.,Spine(Phila Pa 1976). May 1, 2005; Vol. 30(9) pp. 1082-1085]. Spondylolisthesis can cause neurological deficit from neural compression.

Surgical treatment for spondylolisthesis usually involves laminectomy to decompress the neural elements, maneuvers to re-align sagittal and/or coronal balance, and arthrodesis to hold the new alignment [Hresko M T, et al.,Spine(Phila Pa 1976). Sep. 15, 2007; Vol. 32(20) pp. 2208-2213 and Kepler C K, et al.,Orthop Surg. February 2012; Vol. 4(1) pp. 15-20]. To accomplish the realignment, a reduction with pedicle screws followed by interbody fusion with posterolateral fusion is commonly performed. The fixation is commonly done with implanted pedicle screws and titanium rods attached to the screws. The reduction is achieved with superior-inferior (SI) and anterior-posterior (AP) actions to create distraction-compression and subluxation-slippage translation of the vertebral bodies, respectively. Multiple studies have compared treatment approaches [Slone R M, et al.,Radiographics. May 1993; Vol. 13(3) pp. 521-543, and Weinstein et al.,N Engl J Med. May 31, 2007; Vol. 356(22) pp. 2257-2270], and clinical guidelines for spondylolisthesis have been developed by the North American Spine Society (NASS) [Watters W C, et al.,Spine J. July 2009; Vol. 9(7) pp. 609-614], offering guidance to clinicians when encountering this pathology.

The instrumentation currently available for reduction takes the shape of pliers. This often requires multiple instruments (for example for distraction or compression) and steps to achieve the correction, making the procedure technically challenging and difficult to maintain, especially while changing from one instrument or maneuver to another. The pliers also require the rods to be placed between the pedicle screw heads before the correction. Unfortunately, this limits the ability to maneuver the vertebral bodies.

Moreover, these devices have been developed for the classic open surgery. The ability to correct deformities and perform the operations with minimally invasive percutaneous techniques [Chrastil J, Patel A A: J Am Acad Orthop Surg. May 2012; Vol. 20(5) pp. 283-291, Kasliwal M K, et al., J Neurosurg Spine. August 2012; Vol. 17(2) pp. 128-133, Ogilvie J W: Spine (Phila Pa 1976). Mar. 15, 2005; Vol. 30(6 Suppl) pp. S97-101, Quraishi N A, et al., European Spine Journal. Dec. 19, 2012., Sansur C A, et al. J Neurosurg Spine. November 2010; Vol. 13(5) pp. 589-593, Smith J S, et al., Spine (Phila Pa 1976). Nov. 1, 2012; Vol. 37(23) pp. 1975-1982, Smith J S, et al., Spine (Phila Pa 1976). May 20, 2011; Vol. 36(12) pp. 958-964. Chen L, et al, Chin Med J (Engl). January 2003; Vol. 116(1) pp. 99-103, Kasliwal M K, et al. Neurosurgery. July 2012; Vol. 71(1) pp. 109-116, Tian N F, Xu H Z: IInt Orthop. August 2009; Vol. 33(4) pp. 895-903, Fu T S, et al., Int Orthop. August 2008; Vol. 32(4) pp. 517-521, Schlenk R P, et al., Neurosurg Focus. Jan. 15, 2003; Vol. 14(1) pp. e2] has improved and was made possible by intraoperative fluoroscopic and computed tomography (CT) image guidance [Tian N F, Xu H Z:IInt Orthop. August 2009; Vol. 33(4) pp. 895-903 and Fu T S, et al.,Int Orthop. August 2008; Vol. 32(4) pp. 517-521]. However, instruments to correct the deformity using minimally invasive procedures are limited and plier-type instruments are normally unsuitable for these procedures.

In general, forces required to correct spinal deformity are largely unknown [Schlenk R P, et al.,Neurosurg Focus. Jan. 15, 2003; Vol. 14(1) pp. e2]. It is therefore likely that these are highly variable between different surgical techniques and among surgeons. Correction forces are exerted on the screws and respectively on the vertebral bodies during the operation, and excessive loads may lead to bone fracture. Moreover, these forces may be falsely perceived by the surgeon, due to limitations of the instruments used. Current deformity correction devices lack this capability. The vertebral body manipulation device described herein presents several advantages over currently available instrumentation.

Referring now to the various figures of the drawing wherein like reference characters refer to like parts, there are shown inFIG.1AandFIG.1Billustrative views of a vertebral body manipulation device100of the present disclosure.

FIG.1Ashows an exemplary vertebral body manipulation device100according to the disclosure, which includes a module110having two base units120, which may be interconnected by a scissor mechanism174having an X configuration (e.g., a scissor X mechanism). Base unit120may include a quick-lock mechanism150configured to allow base unit120to attach to a screw extension104, which may in turn be configured to attach to a pedicle screw102. Quick-lock mechanism150also includes button112which engages the quick-lock mechanism150, described in detail below.

Scissor X mechanism174may include four revolute joints122and a central joint124. Two of the four revolute joints122may be mounted to a base unit120, one of the revolute joints122may be mounted to threaded coupling133, and one of the revolute joints122may be mounted to slidable coupling121. Threaded coupling133may be configured to mate with threaded pole106, while slidable coupling121may be configured to mate with and slidably engage smooth pole108. Threaded pole106includes a nut assembly140, described further below, which includes a nut132and a threaded surface144. In general terms, the combination of threaded pole106with a base unit120may be considered as a first support member, while the combination of smooth pole108with a base member120may be considered as a second support member.

FIG.1Bdepicts vertebral body manipulation device100attached to vertebral bodies116. Wrench114may be placed on the threaded pole106of the vertebral body manipulation device100and configured to manipulate threaded coupling133of scissor X mechanism174up or down threaded pole106(hidden from view under wrench114) to operate the device. In some embodiments, wrench114may be a torque wrench. Anterior-Posterior (AP), Superior-Inferior (SI), and Left-Right (LR) axes are labeled. Smooth pole108may be configured to engage to scissor X mechanism174via any of a variety of slidable coupling configurations. Threaded pole106may be configured to engage with base unit120, which also includes button112.

In embodiments, vertebral body manipulation device100provides a method of manipulating at least one vertebral body, that includes the steps of placing a first vertebral anchor in a first vertebral body; placing a second vertebral anchor in a second vertebral body; attaching a vertebral manipulation device to a head portion of the first vertebral anchor and a head portion of the second vertebral anchor; and maintaining, while manipulating at least one vertebral body, the head portion of the first vertebral anchor at the same relative orientation and level as the head portion of the second vertebral anchor.

In embodiments, screw extension104and pedicle screw102may be any of a variety of commercially available screw extensions and pedicle screws. Alternatively, a screw extension104could be specifically designed to manipulate pedicle screw102in conjunction with the vertebral body manipulation device100.

As the vertebral body manipulation device and functionalities thereof are intended for use with a body, the materials shall be any of a number of bio-compatible materials presently known or hereinafter developed. Such materials also shall be suitable for the forces and loads that can occur during usage of the instrument. In addition, while particular shapes or geometries are described herein, it is within the scope of the present disclosure for other shapes or geometries to be used as long as the described translational and rotational functional aspects can be carried out using such shapes or geometries.

The modules110for such a vertebral body manipulation device100are configured and arranged as needed for correcting the deformity. As described in further detail herein, each module has three DoF with uncoupled orthogonal translations, and may provide five or six DoF when used in combinations of two or more modules110.

Vertebral body manipulation device is unique in that it may be used in combination with almost any of a number of currently available vertebral anchors (e.g., spinal pedicle screw instrumentation). It also is usable with both “open” surgical procedures and percutaneous pedicle screw techniques. It allows for continuous adjustment and allows for manipulation of the vertebral segment to occur with an intuitive uncoupled motion.

As depicted inFIG.2, a plurality of vertebral body manipulation devices100may be used. In particular embodiments, two vertebral body manipulation devices100are typically used to manipulate vertebral bodies116, one on each side (left and right) of the spine. When used in combinations of two or more modules110, the vertebral body manipulation device100of the present disclosure may provide five or six DoF of maneuverability when used.

FIG.3depicts a kinematic diagram illustrating the orthogonal translations capable according to the vertebral body manipulation device instrument of the present disclosure. As described herein, operation of the vertebral body manipulation device100provides 3 degrees of freedom (DoF) of relative maneuverability between the heads of the screws102to which it is attached, as shown inFIG.2. The DoF are in the Anterior-Posterior (AP), Superior-Inferior (SI), and Left-Right (LR) directions of the Left-Posterior-Superior (LPS) patient coordinate system, represented inFIG.1BandFIG.3. The DoF provided by one device are:SI maneuverability for either distraction or compression is achieved by spinning the nut (si).AP maneuverability in either direction is performed by rocking the entire device in a quasi-sagittal plane as shown by the (ap) arrow.LR maneuverability in either direction is performed by rotating the device in a quasi-coronal plane as shown by the (lr) arrow.
A novel aspect of the kinematics of vertebral body manipulation device100described herein, relative to prior art instruments (e.g., X-Press), is that the vertebral body manipulation device100maintains the heads the pedicle screws102parallel and at the same level. Unlike all other prior art devices, this ensures that a straight bar may be connected between the heads and eliminates the need to bend the bar prior to locking it in the pedicle screws102(not shown inFIG.3), which is often the case with prior art tools.

The DoF of relative maneuverability between the vertebral bodies enabled by vertebral body manipulation devices100are presented inFIGS.4and5. As shown inFIG.4, two vertebral body manipulation devices100provide 5 DoF of maneuverability. For example, vertebral body manipulation devices100may provide +S translation and −S (I) translation, +P rotation and −P (A) rotation, +P translation and −P (A) translation, +S rotation and −S (I) rotation, and +L translation and −L (R) translation with respect to the LPS axes shown in the lower right section ofFIG.4. The mobility of the vertebral bodies116about these axes depends on multiple factors that include their current positioning and the properties of interconnecting tissues and disks. The controls of the devices are determined with fine adjustments in surgery, typically performed under X-Ray fluoroscopy guidance.

The positioning of the vertebral bodies in response the controls of the vertebral body manipulation devices100is also influenced by the state of the pedicle screws102. On most pedicle screws102the head of the screw is mounted with a spherical joint178. This spherical joint178may be locked or unlocked (poly-axial). Pedicle screw102head locking could be used to facilitate the maneuvers, for example the ±S Translations inFIG.4.

In the DoF analysis ofFIG.4, the only missing DoF is the rotation about the L axis. This could be provided if the pedicle screw102are unlocked, the vertebral body manipulation devices100are maintained in position, and additional maneuvers are exerted with traditional instruments, for example on the spinous process, as shown inFIG.5.

FIG.5depicts the 6threlative DoF of maneuverability between the vertebral bodies116may be achieved by holding the location of the unlocked pedicle screws102heads with the vertebral body manipulation device100and maneuvering the vertebral bodies116, for example between the spinous process.

Vertebral Body Manipulation Device

A perspective view of the vertebral body manipulation device100is shown inFIG.6A, and cross-sectional axes A-A and B-B, which are shown inFIGS.6C and6E, respectively, are noted.

As shown inFIG.6A, scissor X mechanism174of module110may include two pairs of bars118that are interconnected with one another via central joint124, thereby forming two X's, one on either side of the module110relative to axis A-A. The two X's are connected to module110via four revolute joints122. Two of the four revolute joints122may be mounted to a base unit120, one of the revolute joints122may be mounted to threaded coupling133, and one of the revolute joints122may be mounted to slidable coupling121. Threaded coupling133may be configured to mate with threaded pole106, while slidable coupling121may be configured to mate with smooth pole108via bushing128. Threaded pole106includes a nut assembly140, described inFIG.6Bbelow, which includes a nut cage134configured to interface with nut132.

In further embodiments, the threaded pole106and smooth pole108are hollow (e.g., pipe shaped) such that long instruments can be passed from the top to the bottom of the poles to access the heads of the pedicle screws102(not shown inFIG.6A). Moreover, the bars118of the revolute joints122of the scissor mechanism174are mounted onto either fixed couplings (e.g., the lower revolute joints122mounted to base units120) or the threaded coupling133or the slidable coupling121on threaded pole106and/or smooth pole108. In the design described herein, any length of bar118is contemplated, and one of skill in the art will appreciate that this will vary depending upon the particular application. In general, the connection heights of revolute joints according to the invention will be minimized so that the joints are centered on the threaded pole106and smooth pole108. Alternatively, these 4 revolute joints122may also be designed on opposite sides of the threaded pole106and smooth pole108(e.g., relative to axis A-A), if the threaded pole106and smooth pole108need to be brought into closer proximity. Placing the scissor X mechanism174on both sides is redundant, but may create a structure with improved stiffness.

Base units120may include button112, which is configured to active a double cam closure mechanism that includes latch126, and is further detailed below inFIG.6C.

As shown inFIG.6B, threaded pole106is threaded along its length and about the outside surface. In further embodiments, such a threaded pole106is a tubular shaped member. The threaded pole106comprises grooves142and a thread surface144. The threaded coupling133may be threaded onto the threaded rod pole106. In yet further embodiments, the thread surface144lends a mechanical advantage that allows the relative movement of the vertebral bodies116(see e.g.,FIGS.4and5).

As depicted inFIG.6B, threaded coupling133includes nut assembly140, which further includes a nut132, a nut cage134configured to interface with grooves142of threaded pole106, bearing balls136positioned between threaded coupling133and nut cage134, thread surface144on an interior surface of nut cage134, bushing surface138, and a center of the nut146. A rotary joint182is implemented between the nut132and the nut-cage134with two rows of bearing balls136. While two bearing balls136are depicted, one of skill in the art will appreciated the number of bearing balls136within rotary joint182may be varied as desired.

Screw head locking can be achieved, for example, by locking nut132of the screw, or by using the quick-lock mechanism150(not shown) of the vertebral body manipulation device100.

Due to the vertebral body manipulation device100kinematics as shown inFIG.3, load in the SI direction generates lateral load between the pedicle screw102and the nut132. Typical screw connections are not well suited for lateral loads, because of the wedging effect of the screw flanks. Instead, a modified ACME type thread with the bushing-nut (B-Nut) design shown inFIG.6Bwas used. The ends of the nut132present cylindrical surfaces that are in a bushing surface138with the outer surface (major diameter) of the threaded pole120. The actual thread of the nut132is only located at the center of the nut146where a larger clearance exists. To do so, the thread of the nut132has to be recessed deeper than the bushings surfaces138, and therefore thread start grooves142are needed at the ends of the nut thread. The bushing surfaces138at the ends of the nut maintain clearance on the flanks of the thread surfaces144.

As such, the screw is sized as an ACME thread screw of major diameter D. The bushings surfaces138(not shown) of the nut132are sized to with a H7/h6 tolerance from D. The thread144on the nut132is sized so that clearance between the flank surfaces of thread exists even if the bushing128is loaded laterally. That is:
CMinT=CMaxBsin α  (Equation 1)
where CMinTis the minimum clearance on the thread flank, CMaxBis the maximum clearance of the bushing128, and α is the angle of the thread flank (29° for the ACME thread). The design enables the lateral loads on the thread by eliminating the high friction wedging effect with a built-in bushing on the screw outer diameter. The gain is in lieu of a minimum axial backlash of the nut132relative to the screw.
BMin=CMaxBsin 2α  (Equation 2)
The backlash is typically larger than that of a regular screw, where flank clearance may be used to control the backlash.

According to another aspect of the present disclosure there is featured an implant system embodying such a vertebral body manipulation device100described herein and a spinal implant as is known to those skilled in the art. In further embodiments, the spinal implant is operably coupled to the vertebral body manipulation device.

FIG.6Cshows a cross-sectional view of a module110of the vertebral body manipulation device according to an exemplary embodiment of the present disclosure along the A-A axis as noted inFIG.6A. Threaded pole106may be configured to couple with threaded coupling133via nut132and nut cage134, which interface on one surface directly with grooves142of threaded pole106while the opposite surface interfaces with the interior surface of threaded coupling133via rotary joint186.

The smooth pole108may be configured to couple with slidable coupling121via bushing128. Bars118and central joint124are shown for reference.

Quick-lock mechanism150may be configured to seat on or mate with screw extensions104to attach vertebral body manipulation device100with one or more vertebral anchors (not shown). Each screw extension104is fitted within receiving hole154of either threaded pole106or smooth pole108. A latch126secures the screw extension104in position within the receiving hole154by inserting into geometric feature125when in the actuated position, thereby locking screw extension104into place. The latch126is actuated by a double-cam mechanism, including surfaces of the latch126, the button112, spring148, and button-end part152.

FIG.6Dis a cross-sectional view of a quick-lock mechanism of the vertebral body manipulation device in a closed (left panel) and opened (right panel) position according to an exemplary embodiment of the present disclosure. As depicted inFIG.6D, when the button112is pressed (right panel), the top cam (button112to latch126) pulls the latch126away from the geometric feature125, which allows screw extension104to be inserted into and/or removed from receiving hole154. When button112is pressed, the cam is in the unactuated (e.g., open) configuration.

When the button112is released (left panel ofFIG.6D), the spring148pushes up the button-end part152, so that the bottom cam (button-end to latch,152to126) pushes the latch126back into geometric feature125, which locks screw extension104into place. After pushing the latch126, the button-end part152also locks the latch126in the closed positon, as shown in theFIG.6D, this ensuring a positive lock of the extension. When button112is released, the cam is in the actuated (e.g., closed) configuration.

FIG.6Eis a cross-sectional view along axis B-B ofFIG.6Aof a nut assembly coupled to a threaded pole106of the vertebral body manipulation device100according to an exemplary embodiment of the present disclosure. Also visible inFIG.6Eis the design of the bearing balls136. For each bearing ball136, a channel162is made within the nut-cage134to allow the bearing balls136to be fed within their races, between the nut132and the nut-cage134, that form the races of the bearing. While two bearing balls136are visible inFIG.6E, one of skill in the art will appreciate that any number of bearing balls136appropriate for the size and configuration of the race may be used. The channels162are then closed with plugs158. In embodiments, design consideration may be given to reduce the internal friction of the mechanism under load by, for example, adding additional bearings. Revolute joints122may be built with joint bearings138to reduce friction. A joint may be made, for example, by two rows of bearing balls138that sandwich one of the bars118with a bearing-race screw156.

In further embodiments, the design of the vertebral body manipulation device100is optimized to reduce the change of its mechanical advantage due to the change in the relative angulation of the scissor X mechanism174.FIG.3shows the location of the4side revolute joints122on the side of the threaded pole106and smooth pole108, for the clarity of the schematic. However, in the design the length of the respective links is zero or negative (on the opposite side of the threaded pole106and smooth pole108). The location of the revolute joints122relative to the threaded pole106and smooth pole108may be optimized to reduce sharp angles of the scissor X mechanism bars174.

Pedicle Screw Lock

Pedicle screws102include ways to secure them to the connecting rods and lock their ball joint (from poly-axial to mono-axial in spine surgery terms). As shown in the cross section views ofFIGS.6C and6E, both threaded pole106and smooth pole108of the vertebral body manipulation device100are hollow. Their inner diameter is large enough to allow the passage of the nut132of the pedicle screw102and its long wrench114. If a rod is set in place over the screw head, the nut132can lock the head of the screw102. This is typically performed after achieving the correction of deformity, so that the correction is secured by the screw-rod implant system.

As the vertebral body manipulation device100of the present disclosure embodies a quick lock mechanism150for coupling the instrument to any of a number of currently vertebral anchors, such as those embodying a utilizing polyaxial screw, such a vertebral body manipulation device is easily adaptable to use such a vertebral anchor.

According to further aspects, the present disclosure also feature methods for stabilizing a spine using such an implant system and/or reduction instrument/device as described herein. Also featured are methods for treating spondylolithesis using surgical techniques and using the vertebral body manipulation device and/or implant system of the present disclosure. Such methods are usable with both “open” surgical procedures and percutaneous pedicle screw techniques. Such methods further include continuous adjustment and manipulation of the vertebral segment to occur with intuitive uncoupled motion.

Such methods include providing one or more modules comprising any of the above described vertebral body manipulation device100and localizing the one or more modules110to a spinal implant and securing the vertebral body manipulation device to the spinal implant. The vertebral body manipulation device100includes an alternative screw-head locking mechanism that enables locking prior to placing the rods. Two lock plunger assemblies170are shown inFIG.7, one placed in the primary device130, the other separately.

In embodiments, the plunger assembly170consists of a threaded cap166that spins over a plunger168. A plunger assembly170is placed through a threaded pole106or smooth pole108(e.g., via a smooth pole hole164) and threaded cap166threads into the head of the screw extension104. Tightening the thread pushes the plunger168down through the threaded pole106or smooth pole108and screw extension104, so that the end surface of the plunger172locks the pedicle screw102by forcing it against its head.

In further embodiments, such methods further include performing other surgical techniques related to the surgical treatment of the underlying condition. Such other surgical techniques include fusion of adjacent vertebrae, bone grafting, discotomy, decompression or laminectomy and spinal implants. Additionally such methods for treating further includes, wound care and minimizing onset of infection.

Although a preferred embodiment of the disclosure has been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims.

INCORPORATION BY REFERENCE

All patents, published patent applications, and other references disclosed herein are hereby expressly incorporated by reference in their entireties.

EQUIVALENTS

Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents of the specific embodiments of the disclosure described herein. Such equivalents are intended to be encompassed by the following claims.