Abstract:
A surgical table extension has a radiolucent inner support member removably attachable to an end of a surgical table and extending outward therefrom in cantilever fashion. A radiolucent outer support member is mounted to the inner support member, and the outer support member is adjustable with respect to the inner support member to change the length of the table extension.

Description:
This application is a continuation-in-part of U.S. application Ser. No. 09/543,878, filed Apr. 6, 2000 now U.S. Pat. No. 6,584,630. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to neurosurgical apparatus generally, and more particularly, to an improved apparatus for supporting an upper torso and head of a patient. 
     BACKGROUND OF THE INVENTION 
     With current medical practices, it is common for a patient to undergo a diagnostic scanning procedure, which is normally performed in a separate suite containing the scanning machine and dedicated to scanning procedures. The scanning machine may be a CT, MRI, or other scanning device. Thereafter, the scan data is utilized in a surgical planning process, which conventionally takes place at a location, for example, an office or an operating room. In some surgical procedures, the scanning data is utilized with a system for post processing the scan data acquired during imaging. Further, the imaging system may be located in a surgical suite, and the surgical planning performed before and during a surgical procedure utilizing the imaging system and scan data. 
     During the scanning procedure, the patient must maintain a perfectly still and motionless posture, and while most often, the patient simply lies on a scanning support table, in some situations, the patient may be supported in the desired scanning position with pads, straps or other supports. Further, the support on which the patient rests is normally radiolucent, that is, transparent to the scanning device, so that the support does not compromise the utility of the scanned image. Further, the patient support used for scanning normally translates with respect to the imaging device. Translation of the patient support permits the patient to be moved into the scanning field or zone of the scanning machine. 
     After the scanning process is completed, often the patient is then moved to an operating room which requires either that the patient walk, or be carried, for example, by transferring the patient from the scanning table to an operating table. Alternatively, as illustrated in U.S. Pat. No. 5,475,884, the patient may be supported on a portable support plate, which is easily moved between the scanning table and the operating table. The scan data is often used in a post processing imaging system for surgical planning purposes both prior to and during surgery. If during or after a surgical process, it is desired to scan a patient again, the patient must be moved from the operating room to the scanning suite, transferred to and from the operating table to the scanning table, and after scanning, transferred back to the operating table and returned to the operating room. The above process is cumbersome, time consuming and potentially risky for the patient. 
     Some newer scanning machines are substantially reduced in size. One such machine is shown in FIGS. 2 and 3 of U.S. Pat. No. 5,499,415, which show an annular-shaped scanner mounted on a wheel-supported frame, to enable the scanner to be used at multiple sites. Consequently, such scanning machines do not require their own suite or room, but instead, they may be used within the operating suite itself. Thus, in an operating room, the patient may be scanned; the surgical planning performed; an operative procedure executed; and the patient scanned again to determine the current status of the operative procedure. Based on the new scanned images obtained from the one or more “intraoperative” scans, the operative procedure can be continued and the above process repeated as necessary. 
     A limitation of the current state-of-the-art is that the posture of the patient during the scanning process is often different from the patient&#39;s posture during surgery. If a patient is positioned in one posture on a scanning table during the scanning process, and then is moved to an operating table, that motion of the patient may cause the position of the target to change with respect to the body surface. During surgery, this problem is compounded by tissue shifts attendant to the opening of body cavities, removal of body fluid or tissues and tissue retractions. Thus, while such motion may be small, any motion of the target will reduce or compromise the utility of the preoperative scan data. 
     The solution to these problems is to scan the patient in the operating room during surgery while the patient is maintained in the surgical posture, and further, to make successive intraoperative scans, as necessary, while still holding the patient in the same surgical posture. 
     While current scanning tables are radiolucent and provide a translation to move the patient into the scanning machine, such scanning tables do not have the accessories required to attach, support and stabilize surgical instrumentation and to properly support the patient&#39;s body in the desired surgical posture. Further, as presently known, scanning tables cannot be used as operating tables, and generally, operating tables are inappropriate for use as scanning tables. 
     Further, after a patient has been placed on an operating table, the patient&#39;s head is then mounted in a stabilization device, for example, a skull clamp. It is essential that the surgeon be able to position the patient very accurately. Minor changes in patient position have major consequences for optimal access and visualization during surgery. Different positions and orientations of the patient&#39;s head relative to the skull clamp often requires that patient&#39;s whole body be moved. Therefore, there is a need to be able to adjust the position and orientation of the patient&#39;s head with respect to the patient stabilization device without having to move the patient&#39;s body. 
     Consequently, there is a need to overcome the above-described problems and support a patient in a desired position in a manner which readily accommodates successive surgical and scanning procedures as well as intraoperative scans. 
     SUMMARY OF INVENTION 
     The present invention provides a variable length surgical table extension that is more flexible than known devices. The variable length surgical table extension of the present invention allows a patient stabilization device to be moved in many degrees of freedom including along a length of the table extension. Thus, a surgeon can easily and accurately position and orient a patient&#39;s head in the stabilization device independent of the patient&#39;s body position; and hence, minor adjustments of the patient&#39;s head with respect to the stabilization device can be made without having to move the patient&#39;s whole body. The variable length surgical table extension of the present invention is especially advantageous for use in neurosurgery and spinal surgery as well as intraoperative scanning procedures. 
     In accordance with the principles of the present invention and the described embodiments, a surgical table extension has a radiolucent inner support member removably attached to a longitudinal end of a surgical table and extending outward from the longitudinal end in cantilever fashion. A radiolucent outer support member is mounted to the inner support member, and the outer support member is adjustable with respect to the inner support member to change a length of the table extension. The surgical table and the table extension are movable relative to the scanning machine to locate the table extension within a scanning zone of a scanning machine. 
     In one aspect of the invention, a radiolucent patient stabilization device, such as a radiolucent skull clamp or a radiolucent horseshoe headrest, is supported by the outer support member. 
     Various additional advantages, objects and features of the invention will become more readily apparent to those of ordinary skill in the art upon consideration of the following detailed description of the presently described embodiments taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a perspective view of a known scanning system and surgical table including a variable length radiolucent table extension in accordance with the principles of the present invention. 
     FIG. 2 is a perspective view of one embodiment having a radiolucent skull clamp mounted on the variable length radiolucent table extension of FIG.  1 . 
     FIG. 3 is a top view of the variable length radiolucent table extension of FIG.  1 . 
     FIG. 4 is a side view of the variable length radiolucent table extension of FIG. 1 showing the locking apparatus disassembled. 
     FIG. 5 is a perspective view of another embodiment having a radiolucent horseshoe headrest mounted on the variable length radiolucent table extension of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, a portable CT scanning system  20  is located in an operating suite with an operating table  22 . The CT scanning system may be either a mobile system such as that commercially available from Analogic of Peabody, Mass. or a stationary scanning system such as that commercially available from General Electric Medical Systems of Milwaukee, Wis. The operating table  22  may be one of many commercially available tables, for example, an operating table commercially available from Amsco of Erie, Pa., MDT Diagnostic Co. of N. Charleston, N.C., or other suppliers. The operating table has a lateral rail  23  extending along each side of the table to which retractors, clamps and other devices may be attached in a stable manner. A stereotactic image processing system  24 , for example, the MAYFIELD-ACCISS image processing system, commercially available from Ohio Medical Instrument Company, Inc. of Cincinnati, Ohio is operatively connected to the scanner  20  and responsive to scan data provided by the CT system  20  to provide selected images on a display screen of the scan data along selected planes. Use of an imaging system  24  of this type is described in U.S. Pat. No. 5,695,501, which is expressly incorporated by reference herein, in its entirety. To facilitate the use of the operating table  22  with the CT system  20 , one end of the operating table is used to support a radiolucent support member or table extension  28 . 
     In use, referring to FIG. 1, the scanning system  20  and operating table  22  are brought into a surgical suite. The scanning system  20  has a toroid shape scanning element  110  with a central opening  112  defining an enclosed or encircled scanning zone with which the portion of the patient to be scanned is axially aligned. The scanning element  110  further has the capability of rotating or tilting within its base  114  with respect to a diametric horizontal axis. The distal end of the radiolucent table extension  28  is narrowed so that it can extend into the opening  112  without interference. If necessary, the head section (not shown) of the table  22  is removed therefrom, and the radiolucent table extension  28  is mounted to the table by inserting the support bars  44  into mating bores on the end surface  47  of the table  22 . The patient  27  is then positioned on the table in a posture suitable for a surgical procedure. The radiolucent table extension  28  is adjustable such that the patient&#39;s upper torso and head are accessible for scanning and surgical procedures. The portion of the patient&#39;s anatomy on which the surgical procedure is to be performed may be stabilized by various clamps and restraining devices. Further, the radiolucent table extension  28  or the scanning element  110  may be tilted so that the desired posture and/or scanning plane is achieved. 
     When the desired surgical posture is achieved, often the patient will have already been scanned; and the surgical planning and procedure can be performed. Thereafter, a portion of the radiolucent table extension  28  is then moved into the opening  112 , for a follow-up scan. The extent to which the table extension  28  is moved into the opening  112  depends on what portion of the head or upper torso is to be scanned. The initial alignment of the table extension  28  may be determined by visual inspection; and thereafter, a scan made to determine exactly whether, and to what extent, the table extension  28  may be out of alignment. Alternatively, the scanner may be equipped with LED&#39;s, or other sources of light, providing beams of light with which the table extension can be aligned. In another embodiment, the table  22  may have an alignment tab  124  which is moved into an alignment slot  124  on the scanner  110 . When the tab  124  is properly seated in the slot  126 , the table is properly aligned with the scanner  110 . The scanning process is executed by the scanning machine moving the scanning element  110  incrementally in an axial direction and with each incremental displacement, a scan is taken. Thereafter, the radiolucent table extension  28  and the patient are removed from within the scanning element  110 , either by moving the scanning machine  20  or the operating table  22 . The scan data is then used in association with the imaging system  24  to plan the surgical procedure. The surgical procedure is then performed, and thereafter, the patient may be moved back into the scanning machine  20 , and the scanning process repeated. The scanning and imaging system may be used to gauge the effectiveness of the surgical procedure; and if necessary, further procedures performed. The above process may be executed any number of times with the patient remaining in the desired position on the same patient support. 
     Thus, the above-described operating table and radiolucent table extension have a significant advantage of not only being able to support a patient during a scanning process, but also support the patient in the identical posture during a surgical procedure. The radiolucent table extension permits an operating table that is normally nonradiolucent and inappropriate for scanning purposes to be used with a scanning machine. Further, the table extension may be tilted to accommodate different desired surgical postures and is sized and shaped to readily fit within the opening of a scanning element, whether in a horizontal or tilted position. Further, not only does the table position permit successive scanning and operative procedures on the upper torso and head of a patient, but the radiolucent table extension  28  readily supports the patient in a prone or supine position. The above described system is illustrated in more detail in U.S. Pat. No. 6,003,174, is assigned to the assignee of the present invention and is hereby incorporated in its entirety by reference herein. 
     While the above described system has significant utility, there is a continuing effort to improve the flexibility and utility of the table extension  28 . Referring to FIG. 2, the radiolucent table extension  28  is variable in length and has a radiolucent inner support member  30  connectable to the operating table  22  and a radiolucent outer support member  32 . Attachable to an outboard or distal end  236  of the outer support member  32  is a radiolucent adaptor assembly  210  that supports a patient stabilization device  280 , for example, a skull clamp. The inner support member  30  has an internal cavity or opening  34  on its outer end  36  that extends longitudinally inside the inner support member  30 . The cavity  34  is located in a slightly enlarged portion  38  of the inner support member  30 . The outer support member  32  has an inner end  40  that is sized and shaped to slide inside the opening  34 . To facilitate movement of the outer support member inner end  40  in the cavity  34 , the inside of the cavity  34  is lined with a low friction material, for example, a TEFLON material. Thus, by sliding the outer support member  32  with respect to the inner support member  30  in a direction parallel to a length or longitudinal axis  361  of the table extension  28 , the length of the radiolucent table extension  28  can be easily changed. 
     After the table extension  28  is adjusted to a desired length, a locking screw  42  is tightened to secure the inner support member  30  with the outer support member  32 . Referring to FIGS. 3 and 4, a slot  46  is disposed through the outer support member  32  such that a longitudinal centerline of the slot  46  is generally collinear with the longitudinal centerline  361 . The slot  46  has an internal peripheral flange  48  that is contiguous with a lower side  50  of the outer support member  32 . A threaded insert  52  is disposed in the slot  46  and rests on the peripheral flange  48 . The insert  52  has opposed flat sides  54  that are adjacent sides of the slot  46  and prevent the threaded insert  52  from rotating. The threaded insert  52  further has an upward extending cylindrical stub  56  that is sized to fit in a hole  58  located in an upper wall  60  of the cavity  34 . The locking screw  42  extends through a clearance hole  62  in a bottom wall  64  of the cavity  34  and is threaded into the threaded insert  52 . 
     Thus, in adjusting the length of the table extension  28 , the outer support member  32  and slot  46  are moved with respect to the stationary inner support section  30  and threaded insert  52 . When the desired length is achieved, the locking screw  42  is tightened causing the threaded insert  52  in the inner support member  30  to clamp against the flange  48  on the outer support member  32 , thereby locking the movable outer support member  32  with the fixed inner support member  30 . 
     An improved system for mounting a radiolucent head clamp to the radiolucent table extension  28  is also illustrated in FIG. 2. A first, or inboard, end  230  of the inner support member  30  of the table extension  28  connects to the surgical table  22  (FIG.  1 ). This connection at the first end  230  occurs via a pair of spaced base mounts  232 . Each of the base mounts  232  engages an inboard corner of the radiolucent table extension  28  and is shaped to receive an outwardly extending post or bar  44  (FIG. 1) extending from the surgical table  22 . A threaded knob  234  tightens upon the inserted post on both sides of the surgical table  22  to securely mount the extension  28 . Depending on the type of table  22 , the manner of mounting the extension  28  may vary. 
     The second, or outboard, end  236  of the outer support member  32  of the radiolucent table extension  28  includes a pair of spaced radiolucent collars  238  aligned along a first connection axis  240 . The first axis  240  is oriented horizontally and perpendicular to the longitudinal direction of the radiolucent table extension  28 . The first connection axis  240  provides for hinged, or pivotal, movement of the radiolucent adaptor assembly  210 , and everything else, including a skull clamp  280 , connected thereto, relative to the radiolucent table extension  28 . 
     To provide this hinged movement about the first connection axis  240 , the radiolucent adaptor assembly  210  comprises a pair of spaced radiolucent adaptor subassemblies  250 , each of the adaptor subassemblies  250  is associated with one of the spaced collars  238  of the table extension  28 . Each subassembly  250  includes identically shaped, radiolucent interior and exterior pieces  252 ,  254 , respectively, which are tightenable in a horizontal direction via a threaded knob  256 . The knob  256  includes a threaded shaft (not shown) which extends through a central clearance bore (not shown) in the exterior piece  254  and engages a central threaded bore (not shown) in the interior piece  252 . If desired, the arrangement of the respective interior and exterior pieces  252 ,  254  can be reversed, so long as the pieces  252 ,  254  are tightenable together upon the respective collars  238 . 
     Along first axis  240 , each of the interior and exterior pieces  252 ,  254 , respectively, has a pair of parallel locator pins (not shown). The locator pins are sized to extend through clearance bores in the collars  238  along the connection axis  240 , with a slip fit, so as to be rotatable relative to the collars  238 . Together, the opposing locator pins of the respective interior and exterior pieces  252 ,  254  are held by the collars  238  along the first connection axis  240 , so that upon tightening of each of the threaded knobs  256 , the inwardly directed surfaces of the interior and exterior pieces  252 ,  254  engage the outwardly directed surfaces of the respective collars  238 . Normally, the annular end surfaces  255  of the collars  238  are toothed or have a known starburst connector, and the inwardly directed opposed surfaces of respective interior and exterior pieces  252 ,  254  likewise have correspondingly shaped serrations. A starburst connector as referred to herein is normally a circular structure in which the connector portion is an annular ring of adjacent, radially extending serrations or teeth. 
     Thus, upon sufficient tightening of threaded knobs  256 , the respective interior and exterior pieces  252 ,  254  will move together horizontally until their respective engagement surfaces contact and engage opposing surfaces of the respective collars  238 . This engagement force holds the radiolucent adaptor subassemblies  250  in a fixed position relative to the radiolucent table extension  28 . Upon loosening the threaded knobs  256 , the subassemblies  250  may be hingedly moved relative to a first connection axis  240  to a different position, whereupon the threaded knobs  256  can again be tightened to form a rigid connection. 
     The radiolucent adaptor assembly  210  of the present invention includes a radiolucent mounting structure  277  which releasably holds and supports the patient stabilization device or head support  280 , for example, a radiolucent skull clamp. The radiolucent mounting structure  277  includes a radiolucent bracket  278 , a radiolucent sliding member  286  and a radiolucent pivoting member  294 . The mounting structure  277  permits the skull clamp  280  to be moved through linear and rotary motions with respect to support member  28 . The radiolucent bracket  278  includes a pair of spaced collars  282  which are adapted to be connected to the spaced adaptor subassemblies  250  along the second connection axis  270 . This likewise enables the skull clamp  280  to be oriented in a desired position relative to the table extension  28 , via hinged movement about first connection axis  240 , hinged movement about second connection axis  270 , or both. The radiolucent bracket  278  receives a radiolucent sliding member  286 . The radiolucent sliding member  286  is lockable to the radiolucent bracket  278  via a clamp comprised of a threaded screw  288 . 
     The pivoting member  294  has a known annular toothed or starburst connector, and a mating starburst connector extends from a frame member  326  of the skull clamp  280 . The radiolucent skull clamp  280  is attached to the pivoting member  294  of the sliding member  286  by means of a clamp comprised of a threaded screw  360 . The radiolucent surgical skull clamp  280  includes a C-shaped frame  322  comprised of frame members  324 ,  326  which are movable to “telescope” toward and away from one another. The frame members  324 ,  326  are normally made of a radiolucent polyethersulfone (PES) and carbon composite material with the carbon component being about 30 percent of the composite by weight. Such a composite material is available from ICI Advanced Materials of Exton, Pa. under the commercial name “THERMOCOMP” JC-1006, and is also available from LNP Engineering Plastics of Thorndale, Pa. under the commercial name “STAT-KON” JC-1006. Alternatively, other radiolucent materials may be used. 
     Frame members  324 ,  326  have parallel first arms  328 ,  330 , respectively, which are juxtaposed to each other in a sliding relationship with the first arm  330  of the frame member  326  cradling or surrounding the first arm  328  of the frame member  324 . Extending from one end of the arm  328 , the frame member  324  has an intermediate arm  332  extending diagonally away from the frame member  326  and an upper arm  334  extending angularly back toward the frame member  326 . The upper arm  334  has, at its outer or distal end, a pin holder, for example, a threaded bore that receives a skull pin  335 . Similarly, extending from the first arm  330 , the frame member  326  has an intermediate arm  336  extending away from the frame member  324  and an upper arm  338  extending back toward the frame member  324 . The upper arm  338  has an angular positioning mechanism  337  mounted at its outer or distal end. The angular positioning mechanism releasably locks a pin holding clevis  339  that supports skull pins  341 . The clevis  339  and skull pins  341  are positioned by operating knobs  343 ,  345  in a known manner. 
     In use, referring to FIG. 2, the bracket  278  and sliding member  286  are first assembled onto the collars  238 . Next, the skull clamp  280  is mounted onto the sliding member  286  using the knob  360  to tighten the skull clamp to a locked position. The precise location of the skull clamp  280  is adjusted in a plane generally perpendicular to the frame members  324 ,  326  using the adjustments described above. The height and angle of the skull clamp  280  is further precisely adjusted using the knobs  256 . Further, after the patient is initially placed on the operating table  22  and table extension  28 , it is necessary to locate the patient&#39;s head in the skull clamp  280 . Next the skull clamp  280  and patient&#39;s head must be located at a desired position and orientation. Those processes are greatly aided by the capability of adjusting the length of the table extension  28 . After loosening the locking screw  42 , the position of the patient&#39;s head with respect to the skull clamp  280  and/or the adaptor assembly  210  is easily changed by translating the outer support member  32  toward or away from the inner support member  30 . After the patient&#39;s head and the skull clamp  280  have been properly positioned and oriented, the locking screw  42  is tightened to secure the outer support member  32  to the inner support member  30 . Thus, the variable length table extension gives the surgeon significantly more flexibility in being able to position and orient the patient&#39;s head and/or skull clamp  280  without having to move and reposition the patient&#39;s whole body on the operating table  22  and table extension  28 . 
     Referring to FIG. 5, in an alternative embodiment, the hinged adaptor assembly  210  of the present invention interconnects a horseshoe headrest  272  to the variable length radiolucent table extension  28 . The hinged adaptor assembly  210  permits the horseshoe headrest  272  to be tilted relative to the table extension  28  about either or both of the first and second connection axes  240 ,  270 . Preferably, the horseshoe headrest  272  includes an upstanding mount  274  oriented perpendicular the length or longitudinal axis  361  of the table extension  28 . This mount  274  may include a dovetail shape, or any other desired cross-sectional shape for that matter, which corresponds to a complementary shape formed in a headrest portion  272   a  or  272   b , so that the headrest portions  272   a  and  272   b  can be slidably located on the mount  274 . 
     If desired, each of the horseshoe headrest portions  272   a  and  272   b  may include a base  273   a  and  273   b  made of radiolucent material for supporting the cushion thereabove along its curved length. The base  273   a  and  273   b  may be made of the same material as the panel  266  and the mount  274 . With this construction, the headrest itself  272  comprises a pad or cushion secured to the base  273   a  and  273   b.    
     When the adaptor assembly  210  of the present invention is used in conjunction with the horseshoe headrest  272 , the U-shaped panel  266  combines with the arcuate end  242  to form an enclosed oval. An outermost end of the entire assembly is now defined by the outermost end of the U-shaped panel  266 . Thus, the headrest  272  resides inboard of the outermost end of panel  266 , and in effect, the adaptor assembly  210  provides a pair of intermediately located hinged axes  240  and  270  for locating the horseshoe headrest  272  in a desired position relative to the table extension  228  and the patient supported thereon. 
     The longitudinal location of the horseshoe headrest with respect to the table  22  can be adjusted to accommodate patients of different heights by loosening the locking screw  42  and moving the outer support member  32  with respect to the inner support member  30 . 
     It is essential that the surgeon be able to position the patient very accurately. Minor changes in patient position have major consequences for optimal access and visualization during surgery. In the past, properly positioning and orienting a patient&#39;s head in a skull clamp often required continuous repositioning of the patient&#39;s whole body on the operating table and table extension. However, the variable length surgical table extension allows a patient stabilization device to be moved in many degrees of freedom including along a length of the table extension. With the variable length table extension, a surgeon can easily and accurately position and orient the stabilization device with respect to the patient&#39;s head substantially independent of the patient&#39;s body position. Therefore, the surgeon can make minor adjustments of the patient&#39;s head with respect to the stabilization device without having to move the patient&#39;s whole body. The variable length surgical table extension provides substantially more flexibility in positioning a patient&#39;s head in a skull clamp and is especially advantageous for use in neurosurgery and spinal surgery as well as intraoperative scanning procedures. 
     While the present invention has been illustrated by a description of various described embodiments and while these embodiments have been described in considerable detail in order to describe the best mode of practicing the invention, it is not the intention of Applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications within the spirit and scope of the invention will readily appear to those skilled in the art. For example, in the described embodiment, the inner support member  30  has a cavity  34  that receives the inner end  40  of the outer support member  32 . As will be appreciated, in an alternative embodiment, the cavity  34  may be located in the outer support member  32 , and the outer end of the inner support member  30  sized to slide into the cavity. Further, one embodiment of a locking system is described herein, but as will be appreciated, there are many potential variations of the described system as well as completely different locking systems that may be used to secure the inner and outer support members together. 
     While one style of skull clamp  280  and headrest  272  are shown and described, in alternative embodiments, other styles of patient stabilization devices may be used with the variable length radiolucent table  28 . 
     Therefore, the invention in its broadest aspects is not limited to the specific detail shown and described. Consequently, departures may be made from the details described herein without departing from the spirit and scope of the claims which follow.