SURGICAL TOOL FOR BONE MANIPULATION
FIELD OF THE INVENTION
This invention relates to medical devices used in surgical procedures. More specifically, the invention relates to medical devices used in bone surgeries, especially as applied to techniques for reduction of Spondylolisthesis, manipulations of spinal vertebral bodies, or manipulations of bone.
BACKGROUND OF THE INVENTION: The clinical indication known as Spondylolisthesis results from subluxation or slippage of a vertebral body anterior, or forward, to its normal anatomical position. For example, the fifth lumbar (L5) vertebral body, or vertebra, can slide forward in relation to the first sacral (SI) vertebra, commonly termed an L5-S1 slippage, causing nerve impingement and instability. Spondylolisthesis is quantified by four levels of severity: grade 1, 25% forward slippage; grade 2, 50% forward slippage; grade 3, 75% forward slippage; and grade 4, 100 % forward slippage of the vertebral body.
It is generally advocated that surgery should be indicated for the patients with greater than 50% slip at initial detection. Numerous surgical procedures have been proposed for this treatment. The most common surgical procedure for the treatment of the Spondylolysis and Spondylolisthesis in adults has been bilateral or posterolateral fusion. Conventional treatment consists of L5-S1 posterior lateral fusion for L5-S1 Spondylolisthesis and L4-S1 fusion for an
L4-L5 slip. In situ fusion has also been advocated for patients with less than 50% slippage.
A large number of spinal fixation devices and techniques have been used. Typically, these involve implantation of an implant, e.g., a screw or pin, into the vertebral bodies in order to fuse them in alignment. These implants can also serve as an anchor for an instrument used to place a force in the posterior direction in order to correct the anterior slippage of the vertebra.
One problem encountered in aligning the slipped vertebral bodies is for the surgeon to be able to create enough posteriorly directed force intraoperatively to correct the condition while having sufficient tactile feedback to prevent any neurologic injuries. In the past, various devices have been used to provide the force in a posterior direction. For example threaded devices have been used which move the vertebral body posteriorly by turning a threaded screw. However, such devices were complicated in their application, as well as limited in their maneuverability or capability to manipulate the bone. For example, the previous devices suffered from a problem of providing an appropriate fulcrum or pivot point to provide a counter-force to the vertebral body being pulled back. In the case of an L5-S1 vertebral subluxation, screws were needed to be put in a superior vertebra, e.g. , L-4, as well as in an inferior vertebra, e.g. , SI, so that the device could be bridged over the vertebral body such that it could be pulled back by posterior force.
BRIEF SUMMARY OF THE INVENTION
It is an object of the invention to provide a device for reducing Spondylolisthesis. It is another object of the invention to provide a device for intraoperative manipulation of a bone in relation to its anatomical position such that the device can efficiently and effectively engage an implant on a bone to be manipulated and simultaneously engage a second part of the body on which force can be applied equal and opposite to that being applied to manipulate the bone. Thus, the subject invention advantageously permits correction of the position of the bone by engaging only a single other contact spot on the body. The subject invention does not require engaging body contact points superior and inferior to the bone being manipulated as in previously used devices, such as the threaded device described above. It is yet another object of the invention to provide a device for aligning a subluxated vertebral body, for example, a fifth lumbar (L5) vertebra subluxated in relation to a first sacral (SI) vertebra, i.e. , an L5-S1 subluxation.
It is a further object of the invention to provide a device for aligning or rejoining a fractured long bone. These and other objects of the invention are achieved by the subject device which comprises a pair of elongate members, or handles, forming upper portions at one end and a pair of lower portions having distal ends. The handles are adjoined at a pivot joint or fulcrum whereby one handle is leveraged against the other for moving the position of the upper portions relative to lower portions. Thus, each of the handles can be arced, or substantially curvilinear in its longitudinal axis to provide a fulcrum point wherein the handles are adjoined , and the upper ends of the handles extend outwardly away from the fulcrum point and the other handle. This configuration of the handles provides for inverse movement of one end relative to the other, i.e., moving the handles at the upper portion toward each other causes the lower portions to move away from each other. The handles can have a spring means to bias the upper portions apart and the lower portions together. In addition, the device can include a mechanism to lock the handles in a particular position.
Advantageously, the distal ends of the lower portion are provided with universally rotatable joints or mounts which can engage, at a wide variety of angles , an implant placed in the bone. This allows the device to engage an implant positioned at an angle different from the angle of force, while applying the force as needed in an appropriate direction to manipulate the bone to its desired position.
This can be done using the subject device in conjunction with implants, preferably an adjustable implant, in a cantilever fashion. Specifically, as in the case of aligning a subluxated L5, the device would engage an implant on L5 and an implant on L4, and the device acts as a fulcrum pulling backwards the L5 vertebral body. A force would be pushed anteriorly on L-4 and then by lever action, a posterior force is placed on L-5, pulling back the slipped vertebral body toward its normal anatomical position. Advantageously, by use of this method , the anterior and posterior forces equal each other out, so that a net force is not placed on other parts of the body, thereby decreasing the risk of injury.
A further advantage is that the subject device can be handled easily by the surgeon such that appropriate and adequate force can be applied to position the bone, while providing tactile feedback to the surgeon so that such force or movement is not so excessive to cause other injury. This is especially useful in surgeries of the vertebrae where overmanipulation of the bone can cause injury to the spine.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a plan view of one face of an embodiment of the subject invention. FIG. 2 is a plan view of the subject invention showing a face opposite that to shown in Figure 1. FIG. 3 shows an embodiment of the subject device having an extendible shaft operative end.
FIG. 4 shows a plan view of one face of a second embodiment of the subject invention . FIG. 5 shows a plan view of one face of a third embodiment of the subject invention. FIG. 6 shows a partial view of an attachment device. FIG. 7 shows a partial view, partially in section, of an integrated attachment device.
DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 1, the manipulation tool 1 comprises two substantially elongate handles 2 joined at a pivot joint 3. The elongate handles extend upward from the pivot joint 3 to form upper portions 4a and 4b and extend downward to form lower portions 5a and 5b. The upper portions 4a and 4b are preferably shaped to conform to the hand to facilitate manipulation of the device, although this limitation is not necessarily. Also, the upper portions 4a and 4b are preferably splayed at a greater distance than the lower portions 5a and 5b. The handles 2a and 2b can be substantially mirror images of one another but are not identical. The pivot joint 3 can be located anywhere along the length of the handles 2a and 2b.
Varying the position of the pivot joint along the handles 2a and 2b varies the relationship of the force exerted on the upper portions 4a and 4b versus the force exerted by the lower portions 5a and 5b. As the pivot joint moves upward the ratio of the force exerted on the upper portions 4a and 4b to that of the force exerted by the lower portions 5a and 5b decreases.
Any type of pivot joint that connects the handles 2a and 2b is acceptable. However, a substantially semi-circular protrusion 6 is preferably located along the length of one handle, shown as 2b in FIGS. 1 and 2, and which interengages with a substantially semi-circular protrusion (not shown) formed on the opposite handle, shown in FIGS. 1 and 2 as 2a. Preferably, the protrusion 6 has a slot formed therein, parallel to the longitudinal axis of the handle, for mating with the protrusion of the other handle. The protrusions are preferably adjoined by a fastener, e.g., a screw 7, which holds together the handles 2a and 2b.
The handles 2a and 2b of the tool are preferably acted upon such that the upper portions 4a and 4b are biased away from each other. This biasing can be achieved by a handle spring 8 which can be affixed to the upper portions 4a and 4b of the manipulation tool 1. Many other spring or biasing mechanisms can be used to maintain the separation of the upper portions 4a and 4b, and this invention is not limited as to a particular type. Also, the invention is not limited as to the location of the biasing. For example, the biasing of the upper portions 4a and 4b away from each other could be accomplished with a spring (not shown) pushing against the lower portions 5a and 5b. In addition, the invention is not limited to biasing of the upper portions 4a and 4b away from each other, but instead, the biasing of the upper portions 4a and 4b can be toward each other.
A locking device 9 is preferably provided for maintaining a particular position of the handles 2a and 2b relative to one another. Locking devices 9 for maintaining a particular position are commonly used in the tool field, and all are acceptable with this device. One such locking device 9 is a bolt and thread assembly (not shown) that extends between the handles
2a and 2b. The presently preferred locking device 9 is shown in FIGS. 1 and 2 and is a ratchet type latching mechanism 9 wherein the ratchet is provided with teeth 22 which engage the upper portion 4b at its tip 24. The ratchet latching mechanism 9 can also be provided with a ratchet spring 10 to bias the ratchet device 9 against the tip 24 of the upper portion 4b. The locking device 9 shown in FIGS. 1 and 2 prevents motion of the upper portion 4a in the direction away from the other upper portion 4b. However, the invention is not limited in this regard. The locking device 9 can limit the motion of the upper portion 4a relative to the other upper portion 4b in either direction or both directions simultaneously .
The locking device 9 can also be provided with an adjustment device to change the orientation of the handles 2a and 2b relative to one another. Adjustment devices are common in the tool field and typically work in conjunction with a particular type of locking device 9. However, this invention is not limited as to the type of adjustment device and with which locking device 9 the adjustment device is used. The presently preferred adjustment device is included with the ratchet type latching mechanism 9. The multiple teeth 22 in the ratchet allow different orientations of the handles 2a and 2b relative to one another. By squeezing the upper portions 4a and 4b towards each other, the orientation of the handles 2a and 2b relative to one another changes, and when the squeeze stops, the locking device 9 still maintains the changed orientation of the handles 2a and 2b relative to one another.
In the preferred embodiment of the prototype, the construction includes a fulcrum 20 that provides inverse movement on each of the handles 2a and 2b on the opposite side of the fulcrum 20, for example, if the upper portions 4a and 4b come together, the lower portions 5a and 5b separate. Therefore, as the user squeezes, a separation action occurs at the lower portion 5a and 5b. However, the invention is not so limited. In an alternative construction (not shown), a criss-cross joint like a pair of pliers is used where squeezing on one portion closes the other portion. In addition, variations or modifications of the device, based on surgeon preferences or on different indications, can be made to allow these two elongated handles 2a and 2b to be connected at any angle, at any point along the handles, passively (fixed) or actively (rotatable about the pivot point). Similarly, the device can be made linearly active by having a moveable fulcrum point or by having the handles 2a and 2b slide in and out at a particular point. The fulcrum mechanism can also have an axial variability, for example, by having a moveable fulcrum or, alternatively, by having handles to which the attachment devices are connected that would move relative to the main body of the fulcrum member. At the distal ends 26a and 26b of the lower portions 5a and 5b is located universally rotatable joints 11 which are connected to attachment devices 12 for engaging implants placed in bone. The joints 11 are preferably positioned relative to the attachment devices such that a line passing through the joints 11 is parallel to a line passing through the attachment devices 12. By positioning the joints 11 relative to the attachment devices 12 in such a manner, when the manipulation tool 1 is rotated slightly about one of the joints 11, the initial direction movement of the attachment device 12 attached to the other joint 11, will be nearly perpendicular to the two lines. This initial direction aids directing upwardly the attachment device 12 in a nearly linear motion when the lower portions 5a and 5b are concurrently spread apart. The joint 11 preferably enables the attachment device 12 to connect with an implant with at least one degree of freedom rotation between the implant relative to the handles 2a or 2b. Joints capable of providing such freedom of rotation are common in the tool field, and all are acceptable. However, the presently preferred joint 11 is an universal joint. The universal joint 11 can alternatively, although not necessarily preferably, be constructed with other multi-directional connecting members, such as ball and socket connectors and flexible hose or rod arrangements. What is important according to the invention is that the attachment devices 12 are arranged relative to the lower portions 5a and 5b so as to approach and secure the implants in any of a wide range of directions.
FIG. 7 shows another example of an attachment device 12 in combination with a joint 11 that enables the attachment device 12 to connect to an implant and enables the implant at least one degree of freedom rotation relative to the handles 2a or 2b. The presently preferred integrated attachment device 12 includes a cup 40 that is formed to fit over a protrusion 42 on the implant 44. However, the invention is not limited to using a cup 40. Attachment devices 12 capable of integrating the joint 11 are well known in the art, and all are acceptable.
The integrated attachment device 12 is advantageously used on an implant 44 that is attached to an article that is being pushed against. As force is directed downward from the handle 2 to the implant 44, the cup 40 is forced against protrusion 42 so to prevent the cup 40 and the implant 44 from disengaging; yet, the cup 40 is still capable of being rotated about the protrusion 42. Thus, the cup 40 acts as both an attachment device 12 that connects the implant 44 to the attachment device 12 and as a joint 11 that allows the implant at least one degree of freedom rotation relative to the handle 2.
The attachment devices 12 can be provided with different fittings for engaging varying sizes of corresponding implants. In one embodiment of the invention, the engagement mounts are removable so that different sizes can be employed with a single device 1. Preferably, the angular position of each attachment devices 12 can be locked in any particular position as desired, and the angular positions can be adjusted before or during the procedure in which the tool is being used. The attachment devices 12 can also selectively engage the implant such that the attachment devices 12 can either be detached from the implant or be incapable of movement relative to the implant.
As shown in FIG. 6, the attachment devices 12 can also be in the shape of an implant such that the attachment device 12 and implant are integrated. The presently preferred implant is a bone implant that inserted into a bone; however, the integrated attachment device 12 is not limited to bone implants. Any type of implant that can attach to an article is acceptable.
The integrated attachment device 12 can also be selectively detachable from the handles 2. This detachment can either be between the attachment device 12 and the joint 11 or between the joint 11 and the handle 2. Thus, the attachment device 12 can be first attached to the article to be manipulated and then the handle 2 can then be attached subsequently to the attachment device 12 or vice-versa.
The joint 11 on each of the lower portions allows the forces to be directed onto the implants at nearly any desirable direction. For example in an L-5 subluxation, the force can be pushed directly down, or at a similar angle, into the implant on L4 or SI to p rovide a very safe platform on which to place such force. The manipulation tool 1 allows the force to be exerted either directly upward or downward because of the combination of the motion possible with the joints 11 and the pivot joint 3. For example, to raise L5, the manipulation tool 1 is pivoted about the joint 11 adjacent the implant on SI. At the same time, the lower portions 4a and 4b are spread apart which also increases the distance between the attachment devices 12. These motions can be combined such that the attachment device 12 connected to L5 moves in linear fashion. Thus, the force can pull posteriorly on L5 in a direction, a spondial reduction, that is compatible with the screw's purchase or hold on the vertebral body. It would be understood that other vertebral positions, or other bones, can undergo similar manipulations. Thus, this procedure using the subject invention can be done with any two vertebral bodies, whether or not adjacent. For example, the procedure can be carried out from the sacrum to any intralumbar levels, thoracic, even cervical levels. Similarly, the manipulation tool can allow linear translation, distraction, in the superior/inferior directions. This is often desired for disc degeneration resulting in the vertebral bodies becoming too close to each other, another factor in nerve impingement. Also, for long bone applications in trauma, for example such as a broken leg, two pins could be put in a femur, and the tool could be used to translate the two bones together in a linear direction.
As shown in Figure 3, the length of extendable handles 29 can be varied according to surgeon preferences or clinical indications. The extendable handle 29 can be lengthened (shown in phantom) as a telescopic extension or other similar extension mechanism which is known in the art. Preferably, the extension mechanism can be reversibly locked into a desired position, e.g. , by a twist and lock mechanism such as is used in other devices having extendable handles.
Other known devices do not have the versatility to be held in any direction, especially the anterior/posterior directions because they require washers or a certain set distance where they have to interconnect. Using less versatile devices, when the screws are placed in a set position not necessarily optimal for applying a force for manipulation of the bone, the surgeon may pull back the vertebral body and discover that further manipulation may cause neurological damage. However, that limited position may not be where the screw's holding spot coincides, thus making it unlikely to provide an appropriate surgical treatment. FIG. 4 is illustrative of another embodiment of the manipulation tool 28. A handle 30 is provided with at least two joints 32 for connecting attachment devices 34 to the handle 30. Although two joints 32 and two attachment devices 34 are shown in FIG. 5, the invention is not limited in this regard. Three or more joints and respective attachment devices are possible. Two attachment devices are advantageously used to provide greater flexibility with regards to the positioning of the attachment devices 34 relative to the implants. Three or more attachment devices 34 can be used to provide a more stable base upon which to manipulate the bone; however, three or more attachment devices 34 provide less flexibility as to the motion available during the manipulation of the bone.
The handle 30 can optionally be divided into at least two portions 36 splaying away from each other. Three or more portions 36 are advantageously provided when three or more attachment devices 34 are also provided. Dividing the handle 30 into two or more portions 36 advantageously raises the handle 30 out of the wound.
The handle 30 can optionally include an arm 38 extending away from the handle 30. The arm 38 advantageously allows the user to apply additional torque to the manipulation tool 28. Also, the arm 38 allows the user to grasp the manipulation tool 28 at a location away from the wound.
Still another embodiment of a manipulation tool 40 is shown in FIG. 5. The manipulation tool 40 includes at least two portions 42 with respective joints 44 for connecting respective attachment devices 34 to the portions 42. A pivot joint 46 is also provided to allow the angular relationship between the portions 42 to vary. 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.
The invention can take other specific forms without departing from the spirit or essential attributes thereof for an indication of the scope of the invention.