Abstract:
A radiolucent surgical table extension assembly for use in combination with a scanning machine having an enclosed scanning zone. A radiolucent support member has a proximal end adapted to be removably attached to one end of a table in a cantilever fashion. The radiolucent support member has a rigidity sufficient to support an upper torso and head of a patient. The table and the radiolucent support member are movable relative to the scanning machine to locate the radiolucent support member and the head of the patient within the scanning zone. A radiolucent mounting structure is connected to the radiolucent support member, and a radiolucent head support is attached to the radiolucent mounting structure for supporting the head of the patient. The radiolucent head support has an opening extending therethrough. The opening receives a locking clamp for attaching the radiolucent head support to the radiolucent mounting structure. In one embodiment, the head support is a radiolucent skull clamp having two frame members wherein each of the members has first legs extending adjacent each other. The first legs have openings extending therethrough, and the openings receive a locking clamp for attaching the radiolucent skull clamp to the radiolucent mounting structure.

Description:
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 “interoperative” 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 interoperative 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, while surgical, or operating, tables contain numerous accessories and couplings to which surgical instrumentation may be attached and supported, most operating tables are not compatible with scanning instrumentation. Thus, as presently known, scanning tables cannot be used as operating tables, and generally, operating tables are inappropriate for use as scanning tables. 
     It is an object of this invention to overcome the above-described limitations in the prior art, by facilitating the function of supporting a patient in a desired position in a manner which readily accommodates successive surgical and scanning procedures as well as interoperative scans. Further the invention fulfills a need to improve and simplify surgical tooling used to support a patient during such procedures. 
     SUMMARY OF THE INVENTION 
     The present invention provides an improved radiolucent surgical table extension assembly for mounting a skull clamp to the table extension. The improved radiolucent surgical table extension assembly of the present invention has fewer parts, is simpler to use, is more flexible and is generally less expensive and more reliable than known devices. The improved radiolucent surgical table extension assembly of the present invention is especially useful for mounting a head support, for example, a radiolucent skull clamp, to the surgical table extension and permits neurological surgical procedures to be performed more efficiently and with less stress. 
     In accordance with the principles of the present invention and the described embodiments, the invention is a radiolucent surgical table extension assembly for use in combination with a scanning machine having an enclosed scanning zone. The invention includes a radiolucent support member having a proximal end adapted to be removably attached to one end of a table in cantilever fashion. The radiolucent support member has a rigidity sufficient to support an upper torso and head of a patient. The table and the radiolucent support member are movable relative to the scanning machine to locate the radiolucent support member and the head of the patient within the scanning zone. A radiolucent mounting structure is connected to the radiolucent support member, and a radiolucent head support is attached to the radiolucent mounting structure for supporting the head of the patient. The radiolucent head support has an opening extending therethrough. The opening receives a locking clamp for attaching the radiolucent head support to the radiolucent mounting structure. 
     In one aspect of this embodiment, the mounting structure permits the head support to be moved through linear and rotary motions with respect to the support member. In another aspect of this embodiment, the head support is a radiolucent skull clamp having two frame members, wherein each of the members has first legs extending adjacent each other. The first legs have openings extending therethrough for receiving the locking clamp to attach the radiolucent skull clamp to the radiolucent mounting structure. 
     In another embodiment of the invention, the skull clamp includes a first frame member having an angular positioning mechanism mounted at one end of the first frame member with a pin holding member rotatably mounted to the angular positioning mechanism. A first arm forming an opposite end of the first frame member, the first arm has an opening extending therethrough. A second frame member has a pin holder on one end thereof and a first arm forming an opposite end of the second frame member. The first arm has an opening extending therethrough, and the first arms of the first and second frame members are positioned with respect to each other so that the first and second frame members form a generally C-shaped skull clamp. A clamp extends through the openings in the first arms of the first and second frame members and is adapted to removably connect the skull clamp to a supporting structure. 
     In one aspect of this second embodiment, the clamp is a knob attached to a threaded shaft; the opening in the first arm of the first frame member is a clearance hole for receiving the shaft; and the opening in the first arm of the second frame member is a clearance slot for receiving the shaft. 
     In a further embodiment, the present invention includes a method of mounting a radiolucent skull clamp having a connector to a support having a mating connector. The method first holds the connector of the radiolucent skull clamp against the connector of the support in a desired orientation. A clamp shaft is then inserted through clearance holes in both the first and second frame members of the skull clamp, and the clamp shaft is then secured to the support, thereby mounting the skull clamp to the support. 
     The improved radiolucent surgical table extension assembly of the present invention utilizes a radiolucent skull clamp with clearance openings extending through the base of the adjacent lower arms of the clamp with the movable lower arm having a clearance slot, thereby permitting the movable lower arm to move through its full range of motion without interfering with a clamp shaft extending through the clearance openings and mounting the skull clamp to the table extension. 
     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 portion of a known surgical table including a radiolucent table extension assembly. 
     FIG. 2 is a first perspective view of a radiolucent skull clamp in accordance with the principles of the present invention. 
     FIG. 3 is a front elevation view of the radiolucent skull clamp of FIG.  2 . 
     FIG. 4 is a cross-section view taken along the line  4 — 4  of FIG.  3 . 
     FIG. 5 is a cross-section view taken along the line  5 — 5  of FIG.  4 . 
    
    
     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, Massachusetts 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 support plate  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 length of the support plate  28  is sized 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 support plate  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, normally 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 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 may be determined by visual inspection; and thereafter, a scan made to determine exactly whether, and to what extent, the table extension 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 increment, a scan is taken. Thereafter, the 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 has 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 and simplify the mounting of tooling, clamps and other devices to the radiolucent table extension. An improved system for mounting a radiolucent head clamp to the radiolucent table extension  28  is illustrated in FIG. 2. A first, or inboard, end  230  of the table extension  28  connects to the surgical table  22  (FIG.  1 ). Normally, 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  43  (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 . The extension  28  comes in two different lengths. Depending on the length of the extension  28  and the type of table  22 , the manner of mounting the extension  28  may vary. 
     A second, or outboard, end  236  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 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 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 a 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. Referring to FIG. 4, the radiolucent bracket  278  includes an internal dovetail  284  sized to receive a complementary shaped dovetail member  285  from a radiolucent sliding member  286 . The radiolucent sliding member  286  is lockable to the radiolucent bracket  278  via a clamp comprised of an adjustment knob  288  and threaded shaft  289 . The end of the shaft  289  pushes and clamps the dovetail member  285  against the dovetail member  284 . 
     The sliding member  286  is comprised of first and second radiolucent connector members  287 ,  290  that together form a generally U-shaped bracket or clevis. The sliding member  286  further includes a radiolucent pivoting member  294  having a tongue  296  extending within the clevis between the connecting members  287 ,  290 . A clamp having a radiolucent locking knob  298  also includes a shaft  299  that extends through a clearance hole  300  within the connecting member  287 , through a clearance hole  302  of the tongue  296  and into a threaded hole  304  of the connecting member  290 . An annular surface  306  on the upper side of the tongue  296  and an opposing lower surface  308  (FIG. 4) of the connector  290  are serrated or toothed to prevent relative angular motion between the pivoting member  294  and the sliding member  286  when the knob  298  is tightened. The pivoting member  294  has a known annular toothed or starburst connector  312  with a centrally located threaded hole  314 . A mating starburst connector  314  extends from a frame member  326  of the skull clamp  280 . 
     Referring to FIG. 2, the radiolucent surgical skull clamp  280  includes a C-shaped frame comprised of frame members  324 ,  326  which are movable to “telescope” toward and away from one another. The frame members  324 ,  326  of the clamp  322  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, Penn. 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. 
     Referring to FIG. 3, the first arm  330  of the frame member  326  is generally U-shaped to receive the first arm  328  of the frame member  324 . The first arm  330  has two sides  340 ,  342 , which extend past the first arm  328 . A bottom plate  344  normally made from the PES and composite material is mounted between the sides  340 ,  342  of the first arm  330  such that there is clearance between the bottom plate  344  and a rack  346  on the bottom of the first arm  328 . The bottom plate  344  is held in place between the sides  340 ,  342  of the first arm  330  by fasteners (not shown) which are normally made of nylon. The bottom plate  32  slidably receives a retractable rack member  348  which is connected to a release pin  350 . The retractable rack member  348  and release pin  350  are normally made from the “DELRIN” acetal polymer material. The retractable rack member  348  has teeth that are sized to engage teeth of the rack  346  on the first arm  328  of frame member  324 . A compression spring  352  is mounted over the release pin  350  and extends between the releasable rack member  348  and the bottom plate  344 . The compression spring  352  applies a force against the retractable rack  348  which holds its teeth in engagement with the teeth of the rack  346  on the first arm  328 , thereby preventing the frame members  324 ,  326  from moving in a direction away from each other. However, the configuration of the racks  346 ,  348  permits frame members  324 ,  326  to be slid toward each other to size or position the clamp  322  generally with respect to a patient&#39;s head  354 , shown in phantom in FIG.  1 . To release the clamp, the release pin  350  is pulled downward, thereby compressing the spring  352  and moving the rack  348  out of engagement with the rack  346  of the first arm  328 . With the racks  346 ,  348  disengaged, the frame members  324 ,  326  may be separated, thereby releasing the clamp from the patient&#39;s head  354 . Other details of the construction of the radiolucent skull clamp  280  are found in U.S. Pat. No. 5,537,704 assigned to the assignee of the present invention and hereby incorporated herein in its entirety. 
     Referring to FIG. 4, 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 knob  360  and threaded shaft  362 . The knob  360  has a threaded shaft  362  that extends through a clearance hole  364  in the side wall  340  at the first arm  330 . The shaft  362  then extends through a slot  366  extending through the first arm  328  of the first frame member  324 . The slot  366  is of a length that the shaft  362  does not interfere with the motion of the frame members  324 ,  326  over their full range of motion. The shaft  362  further extends through a clearance hole  368  of the second wall  342  of the first arm  330  of the frame member  326 . The threaded distal end  370  of the shaft  362  threadedly engages the threaded hole  314  of the pivoting member  294 , thereby locking the skull clamp to the sliding member  286 , connecting element  287  and radiolucent table extension  28 . While the holes  364 ,  368  are normally clearance holes, as will be appreciated, the shaft  362  may be threaded over its length; and one or both of the holes  364 ,  368  may be threaded holes. 
     In use, referring to FIGS. 2 and 4, 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 determined by starburst connectors  312 ,  314 . The precise location of the skull clamp  280  is adjusted in a plane generally perpendicular to the frame members  324 ,  326  using the adjustments associated with the knobs  288 ,  298 ,  360 . Loosening the knob  288  permits the skull clamp  280  and sliding member  286  to be moved linearly in a direction that is substantially horizontal and parallel to a plane passing through the frame members  324 ,  326 . When the skull clamp  280  is at the desired position, tightening the knob  288  locks the sliding member  286  to the bracket  278 . Loosening the knob  298  permits the skull clamp  280  to be pivoted about an axis of rotation  310  that is normally vertical and substantially parallel to the plane passing through the frame members  324 ,  326 . After the desired orientation about the axis  310  is found, the knob  298  is tightened to lock the skull clamp  280  at that orientation. Loosening the knob  360  permits the skull clamp  280  to be pivoted about an axis of rotation  361  that is normally horizontal and substantially perpendicular to the plane passing through the frame members  324 ,  326 . After the desired orientation about the axis  361  is found, the knob  360  is tightened to lock the skull clamp  280  at that orientation. The height and angle of the skull clamp  280  is further precisely adjusted using the knobs  256 . The knobs  256  on both sides of the table extension  28  are normally tightened or loosened in unison, to facilitate orienting the radiolucent support  264  relative to the table extension  28 . As with the connections along the first connection axis  240 , along the second connection axis  270 , each adaptor subassembly  250  includes opposing locator pins  271  which extend along the second axis  270  and into the collars  282 , to locate the interior and exterior pieces  252 ,  254  in a desired position relative to the second axis  270 . 
     The radiolucent adaptor assembly  210  provides two parallel axes of connection  240 ,  270  residing between the radiolucent table extension  28  and the patient stabilization device used to hold the head of the patient in a desired position. Thus, the present invention increases the versatility of patient positioning relative to a radiolucent table extension assembly for advantageous use in interoperative scanning procedures. This versatility is available for patient stabilization with either a skull clamp or a horseshoe headrest. In fact, this invention makes it easy for attendants to interchange the surgical set up, by removing one of these two different holding devices and connecting the other. Moreover, the present invention achieves these advantages in a manner which is user-friendly for the surgeon and operating room attendants, because the maneuverability of the patient stabilization device is achieved about two spaced parallel axes  240 ,  270  via adjustment of a pair of spaced adjustment knobs  256 . 
     The interior pieces  252 ,  254  and the locator collars  238 ,  282  along the first and second connector axes  240 ,  270  are made by Potts Composites of Floydada, Tex. out of carbon fiber composite and epoxy resin material. The knob  256  are made from aluminum or a radiolucent material. 
     Thus, the improved radiolucent surgical table extension assembly of the present invention simplifies the mounting of a radiolucent skull clamp to the table extension. The improved radiolucent surgical table extension assembly of the present invention has fewer parts, is simpler to use, is more flexible and is generally less expensive and more reliable than known devices. The improved radiolucent surgical table extension assembly of the present invention is especially useful for mounting a radiolucent skull clamp to the surgical table extension and permits neurological surgical procedures to be performed more efficiently and with less stress. 
     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 head support  280  is shown as a skull clamp. As will be appreciated, a horseshoe headrest, other types of headrests, a single piece skull clamp or other types of head supports may be connected to the mounting structure  277 . 
     Further, in the described embodiment, the various clamps are implemented with knobs and associated threaded shafts. As will be appreciated, other mechanical clamping devices or mechanisms may be used. Further, the described mounting structure  277  provides a serial linkage of a bracket  278 , a sliding member  286  and a pivoting member  294 . As will be appreciated, the arrangement of the sliding member  286  and pivoting member  294  may be reversed. Further, other relatively moving members may be used to obtain motion in other directions. While it is anticipated that the greatest utility of a skull clamp having openings  366 ,  364 ,  368  in the respective lower arms  328 ,  330  is one made from radiolucent materials. As will be appreciated, the structure described and claimed herein can also be applied to devices made of opaque materials. 
     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.