Abstract:
A head support bas unit enables enhanced capability for positioning the head of a patient at the end of a medical table, by incorporating into the handle assembly thereof an additional degree of freedom, namely rotatability along the longitudinal axis of the handle. More specifically, a pair of axially opposed, spring-biased ratchets are housed within the handle, to permit or prevent axial rotation of one end of the handle relative to the other. This enhanced flexibility an maneuverability is achieved without any added complexity, and without requiring any additional space. These advantages are further magnified if an additional like handle assembly is connected to the first handle assemble, with a link interconnected therebetween, because composite angles and off-axis positioning of the patient can be readily accommodated.

Description:
FIELD OF THE INVENTION  
       [0001]    This invention relates to a base unit for connecting a head holding device to a medical table, and more particularly, to a base unit which optimizes flexibility, maneuverability, and certainty locating and fixing the head holding device in a desired position relative to the medical table. 
       BACKGROUND OF THE INVENTION  
       [0002]    The assignee of the present application owns U.S. Pat. No. 5,564,663, entitled “Transitional Pivot Joint For Head Support Base Unit,” which is expressly incorporated herein by reference, in its entirety (the “&#39;663 patent”). The &#39;663 patent shows a base unit which connects to a medical table. The base unit includes a crossbar and a handle assembly. A transition member connects to the handle assembly, and a swivel adaptor connects to the transition member. Typically, a head holding device, such as a skull clamp or a horseshoe headrest, connects to the swivel adaptor to hold the head of a patient in a desired position relative to the table. Assignee&#39;s U.S. Pat. No. 4,169,478, shows a commonly used, well known three-pin skull clamp, and U.S. Pat. No. 5,317,771, shows a well-known horseshoe headrest. 
         [0003]    In practical terms, the base unit serves as the intervening hardware that holds the patient&#39;s head relative to the medical table. That is, the base unit represents the structural component that connects directly to the medical table, and which in turn supports one or more additional structural components, the last one of which securely holds the head holding device. Usually, the head and upper torso of the patient are cantilevered so as to extend horizontally off the end of the medical table, with the head of the patient fixedly held in place by the head holding device. When the intervening structure of the head holding system includes a base unit, a transition member, and a swivel adaptor, as disclosed in the above-mentioned &#39;663 patent, each of these components is selectively movable relative to each adjacently located component. This enables the neurosurgeon, or the operating room nurse or attendant, to position the patient&#39;s head in a desired position relative to the medical table, and then to rigidly clamp these various components together in a desired orientation, to achieve rigid support of the patient&#39;s head in the desired position. 
         [0004]    More specifically, the base unit has two spaced support rods that connect to the medical table, which in turn support two spaced brackets which hold a horizontal crossbar. A handle assembly of the base unit is oriented transverse to the crossbar, and includes at a first end thereof a first clamp with a first bore that is sized to surround the crossbar. The internal dimension of the first bore is such that the handle assembly may be rotated about the axis of the crossbar, but may also be locked in a fixed position relative to the crossbar when the first clamp is tightened so as to reduce the internal dimension of the bore. The first clamp also enables the handle assembly to be moved horizontally along the crossbar, between the opposing brackets. 
         [0005]    The handle assembly of the base unit includes an internal extension bar which extends along an elongated body of the handle assembly, but is fixed adjacent to the first clamp. A lever is pivotally connected to the elongated body, and is also operatively connected to the opposite end of the extension bar. The lever moves relative to the elongated body between: 1) an open unlocked position, in which the bore of the first clamp is enlarged relative to the crossbar and thereby rotatable with respect thereto; and 2) a closed, or locked position in which the internal dimension of the first clamp is reduced to lock the clamp to the crossbar. Thus, movement of the lever between the open and the closed positions enables the handle assembly to be rotatable or fixed, respectively, relative to the crossbar via the first clamp. 
         [0006]    The handle assembly also includes a second clamp at a second end thereof, which defines a second bore spaced from and oriented parallel to the first bore. As with the first bore, the second bore has an internal dimension which varies, depending upon the position of the lever relative to the elongated body. The second bore of the handle assembly is sized to removably hold a shaft mounted transversely at one end of the transition member. 
         [0007]    Thus, when the lever is in the open position relative to the handle assembly, the handle assembly is rotatable about the first axis, i.e. around the crossbar, and the transition member is also rotatable about a second spaced axis which is parallel with the first. Once rotated to the desired position, these components can be locked in place by closing the lever. The opposite end of the transition member typically includes a combination threaded/star burst connection to enable a first end of a conventional swivel adaptor to connect to the transition member. An opposite end of the swivel adaptor includes another combination threaded/star burst connection, for rigid securement thereto of the desired head holding device. These threaded star burst connections at the opposite ends of the swivel adaptor provide additional maneuverability for this head holding support system. 
         [0008]    This combination of selectively movable components, including the intervening clamps and connectors, provides stable and secure fixation of a patient relative to the medical table, with a high degree of reliability and consistency, as is needed for brain surgery. In fact, the head holding devices shown in these U.S. patents are recognized by neurosurgeons around the world as representing the gold standard in terms of achieving a high degree of head fixation and stability with respect to holding the head of a patient during brain surgery. Although others have tried to mimic these head holding devices and these systems, for one reason or another they have not been as successful as assignee, or its predecessor, in consistently achieving the desired degree of patient fixation relative to a medical table. 
         [0009]    Despite its long track record of success for these head holding products, assignee seeks to continue to improve upon the performance of such cranial stabilization devices, in an effort to continue to meet the needs of neurosurgeons around the world. But with respect to enhanced maneuverability, this goal is more easily wished for than actually achieved. That is because each additional component requires additional structure for permitting selective movement relative to the adjacently located components, and also the necessary structure for locking the component in the selected position. So adding an additional degree of maneuverability generally requires another connector, and also occupies additional space. Also, in the operating room it can also be important for the operation of these components to be readily understood and user-friendly, so a completely different structure could lack the degree of familiarity of the well-known components currently used. 
         [0010]    Also, in some instances, the time and convenience of maneuvering these head holding components into the correct position can be critical. Because of the multiple connection points of the various intervening components, it is possible that inexperienced operating room personnel may initially connect the components in an incorrect manner, such that the components need to be disconnected and then properly connected in order to securely hold the patient in the desired position. Also, some of these intermediate pieces come in different sizes. For instance, the transition member typically comes in two standard lengths, three inches and six inches. Such size variations can create questions among operating room personnel as to the most preferred, or most appropriate, components to use for holding a patient in a particular situation. 
         [0011]    It is one object of the invention to enhance the flexibility and versatility of a head holding structure used to maneuver and support a patient in a desired position at the end of a medical table. 
         [0012]    It is another object of the invention to simplify the decisions, the procedures, and/or the components needed by neurosurgeons or operating room attendants for correctly locating a patient&#39;s head in a desired position relative to the end of the medical table, and then firmly securing the patient&#39;s head in that desired position. 
         [0013]    It is still another object of the invention to accomplish these objectives with structure that is reasonably familiar to neurosurgeons and operating room personnel, and which does not occupy an excessive amount of three dimensional space. 
       SUMMARY OF THE INVENTION  
       [0014]    The present invention achieves the above-stated objects by incorporating an internal clutch mechanism into the elongated body of the handle assembly, to enable an outboard second section of the handle assembly to rotate axially relative to an inboard first section. 
         [0015]    With rotatability along the longitudinal axis, the axis of a second clamp, located opposite the crossbar and a first clamp, may be selectively rotated to an orientation that is non-parallel with the connecting tube, and then locked in place at that selected orientation. In addition to this axial rotatability, this handle assembly still permits the conventional translational movement along the crossbar, rotational movement about the crossbar, and rotational movement at the second clamp. But with this additional degree of freedom, and hence this additional maneuverability, this base unit greatly enhances flexibility and maneuverability in locating and fixing a patient in a desired position relative to a medical table, without adding any additional knobs or securement devices, and without taking up more space. 
         [0016]    To do this, this inventive base unit uses a lever which operatively connects to one end of an extension bar with the extension bar extending along and inside the body of a handle assembly. The extension bar is fixed at one end of the body, adjacent the crossbar. Movement of the lever relative to the body causes the extension bar to simultaneously open or close a pair of spaced clamps that are located at opposite ends of the body. But at the same time, the movement of the lever and the extension bar also causes a pair of internal spring-biased, axially opposed ratchets to either engage or disengage along the longitudinal axis of the body. When the ratchets are disengaged, one end of the body is axially rotatable relative to the opposite end. When the ratchets are engaged, the two ends of the body are axially fixed relative to each other. Thus, these spring-biased axially opposed ratchets serve as an internal clutch mechanism. Preferably, the lever and this internal clutch mechanism generally occupy the same volume as existing base units. 
         [0017]    Because this handle assembly is preferably sized and shaped similar to existing base units, this invention provides these advantages in a manner that is readily understood by neurosurgeons and operating room personnel. Stated another way, this invention supplies these advantages in a user-friendly way, by modifying existing conventional components. 
         [0018]    For all of these reasons, the base unit of the present invention can be substituted for the prior conventional base unit to achieve numerous and immediate advantages. Also, at least one additional like handle assembly can be operatively connected to the first handle assembly, preferably with a link interconnected therebetween. This additional like handle assembly provides additional maneuverability for the interconnected head holding system, because it provides rotatability along the additional longitudinal axis of the additional handle assembly, in addition to providing the conventional degrees of freedom via the spaced clamps located at opposite ends thereof. This structure significantly enhances the flexibility of positioning a head support device that is operatively secured to the outer end of the additional handle assembly. In fact, the use of two or more such handle assemblies causes the interconnected components to have an almost snake-like ability to accommodate any desired patient position. 
         [0019]    With this added flexibility and maneuverability, the need for stocking differently sized transitional members is eliminated. One modified size will suffice to accommodate any desired patient position. Also, the need for the conventional swivel adaptor is eliminated completely, along with its two knobs which typically require manual tightening and loosening. In contrast, the modified transition member includes only one knob. Instead, for each of the handle assemblies the lever opens to provide the benefit of additional degrees of freedom relative to the crossbar, and then closes to lock in the selected position for the patient. 
         [0020]    According to one aspect of the invention, handle assembly includes structure for affirmatively holding the lever in the closed position. According to the preferred embodiment of the invention, with axial rotatability about the handle body, this can be achieved via a trigger-like latch pivotally mounted to the lever. Another structural option for supplying this feature would be a wire catch. In fact, the present invention contemplates the possibility of applying this inventive principle, namely an affirmative lock mechanism, to existing conventional base units. That could be done in a number of different ways, but perhaps most conveniently with a wire catch mounted to the end of the lever, and adapted to engage the existing body of the conventional handle assembly. 
         [0021]    These and other features of the invention will be more readily understood in view of the following detailed description, and the drawings. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0022]      FIG. 1  is perspective view which shows a first preferred embodiment of the invention, with a first handle assembly supporting a transitional member in a desired position relative to a connecting tube, and the lever of first handle assembly in an open, unlocked position. 
           [0023]      FIG. 2A  is a perspective view which shows a variation of the first preferred embodiment of the invention that is shown in  FIG. 1 , with an additional handle assembly connected to the first handle assembly via an intervening link, and a modified transition member connected to the additional handle assembly. 
           [0024]      FIG. 2B  is a perspective view which shows another variation of the invention shown in  FIGS. 1 and 2A . More specifically,  FIG. 2B  shows a medical table and also a skull clamp held by the additional handle assembly, via the intervening modified transition member. 
           [0025]      FIG. 2C  shows the same construction of the invention as shown in  FIG. 2A , but with the first handle assembly, the additional handle assembly, the intervening link, and the modified transition member arranged in a different orientation. 
           [0026]      FIG. 2D  is a side view of the same variation of the invention as shown in  FIGS. 2A and 2C . 
           [0027]      FIGS. 2E and 2F  are longitudinal views showing two orientations of the present invention, connected to a table, with the brackets directed upwardly, as shown in  FIG. 2E , or downwardly, as shown in  FIG. 2F . 
           [0028]      FIG. 3A  is a longitudinal cross sectional view of the first handle assembly in accordance with a first preferred embodiment of the invention, with the lever in an open, unlocked position. 
           [0029]      FIG. 3B  is a longitudinal cross sectional view of the first handle assembly, similar to  FIG. 3A , but with the lever in a closed, locked position. 
           [0030]      FIG. 4  is a disassembled perspective view of the first handle assembly, in accordance with the first preferred embodiment of the invention. 
           [0031]      FIG. 5  is a longitudinal cross sectional view taken along line  5 - 5  of  FIG. 2D , showing the link which interconnects the first and second handle assemblies, in accordance with the embodiment of the invention shown in  FIGS. 2A ,  2 B,  2 C and  2 D. 
           [0032]      FIG. 6  is a perspective view of another variation of the invention, namely a wire catch for affirmatively securing the lever in the locked position. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0033]      FIG. 1  shows a head support system  10  constructed in accordance with a first preferred embodiment of the invention, for holding the head of a patient (not shown) in a desired position relative to a medical table (not shown). The system  10  includes a base unit  12  and a conventional transition member  14 .  FIG. 1  shows that the primary advantages of the present invention can be achieved with relatively few components, and also by using some of the existing conventional cranial stabilization components, such as a conventional transition member  14 . 
         [0034]    The base unit  12  of the present invention includes a pair of spaced support rods,  16  and  17 . A corresponding set of brackets  18  and  19 , respectively, hold the support rods  16  and  17  in parallel. A crossbar  20 , also sometimes referred to as a connecting tube, spans the horizontal distance between the brackets  18  and  19 , and the brackets  18  and  19  hold the connecting tube  20  in a fixed position so that there is no relative rotation therebetween. In this application, the words connecting tube and crossbar are used interchangeably, and the word tube does not necessarily mean that the structure is hollow. At one end of the connecting tube  20 , and in this case the end where bracket  19  connects thereto, a hex key wrench  21  is threadably held by the bracket  19  and removable therefrom to allow the adjusting of bracket  18  via button head screw  22 . This screw  22  is located on the bracket  18  at the other end of the connecting tube  20 , and it may be loosened to permit translational movement of bracket  18  along the connecting tube  20 , thereby to vary the spacing between support rods  16  and  17  to accommodate some variation in the differently spaced mounting structures used by medical tables. 
         [0035]    In accordance with the invention, the base unit  12  includes a handle assembly  25  which has a first clamp  26  located at a first end thereof, which circumscribes the connecting tube  20 . The handle assembly also includes an elongated body  27  and a second clamp  28  located at a second end thereof. A lever  29  hingedly connects to the elongated body  27 . The lever  29  pivotally moves between an open, unlocked position, as shown in  FIG. 1 , and a closed, locked position. 
         [0036]    At the first end of the elongated body  27 , the first clamp  26  includes an internal bore  33  which is aligned along a first axis  34 . The first axis  34  is also the axis of the connecting tube  20 . The second end of the handle assembly  25  includes a second bore  35  which defines a second axis  36 .  FIG. 1  shows a transversely oriented shaft  37  located at one end of the transition member  14 , which extends into the bore  35  and along second axis  36 . Adjacent the first clamp  26  at the first end, the handle assembly  25  includes a reinforcing sleeve  32 . 
         [0037]    As with conventional base units, the base unit  12  of the present invention is movable laterally along the connecting tube  20 , as shown by directional arrows  38 , when the lever  29  is unlocked. Moreover, directional arrows  39  show the rotational capability of the handle assembly  25  relative to first axis  34 , when the lever  29  is unlocked. Directional arrows  40  show the rotational capability about the second axis  36 . In contrast, when the lever  29  is moved to a locked position, preferably adjacent to the body  27 , the movements depicted by directional arrows  38  and  39  are prevented. Also, the closing of lever  29  relative to elongated body  27  causes the second clamp  28  to securely engage the shaft  37  of the transition member  14 , thereby to rigidly hold the transition member  14  in a desired position relative to the handle assembly  25 . These three capabilities, namely lateral movement along the connecting tube  20 , rotational movement about the connecting tube  20  (also the first axis  34 ), and rotational movement about the second axis  36 , are conventional with base units that are commercially available. And the degrees of freedom and maneuverability provided by such conventional base units has enabled neurosurgeons to rigidly hold a patient&#39;s head in a desired position relative to a medical table. 
         [0038]    But the base unit  12  of the present invention improves upon these prior capabilities by also enabling axial rotatability of the second clamp  28  about a handle axis  30  which extends along the elongated body  27 . This additional degree of freedom, i.e., rotatability about axis  30 , as shown by directional arrows  41 , enhances the ability of a neurosurgeon or an operating room attendant to securely hold a patient in a desired position relative to a medical table, wherein the position may be angled or offset relative to the longitudinal axis of the table. More specifically, when lever  29  is in an open or unlocked position relative to elongated body  27 , the second axis  36  may be reoriented at an angle which is no longer parallel with first axis  34 . Previously, with conventional base units these spaced axes always remained in parallel orientation. 
         [0039]      FIG. 2A  shows a head support system  110  which is slightly varied from the head support system  10  shown in  FIG. 1 . More specifically,  FIG. 2A  again shows the same spaced rods  16 ,  17 , brackets  18 ,  19 , connecting tube  20 , and first handle assembly  25 , including the first clamp  26  and the second clamp  28 .  FIG. 2A  shows lever  29  in a closed, or locked position, to inhibit rotation about axis  30 . Rotational arrows  39 ,  40 , and  41  depict the rotational degrees of freedom, i.e. the maneuverability, permitted by the present invention, including rotation about the longitudinal axis  30  of the elongated body  27 . Notably, it is not only the second clamp  28  of first handle assembly  25  which is rotatable about longitudinal axis  30  with respect to the first clamp  26  when lever  29  is in an unlocked position, but also all of the additional components that are connected to second clamp  28 . 
         [0040]      FIG. 2A  shows a latch  42  which pivotally connects to the lever  29 . The latch  42  holds or retains the lever  29  in the closed, locked position, relative to elongated body  27 . By pivoting the outer end of latch  42  in a trigger-like movement, the lever  29  may be moved to the unlocked position. This latching mechanism  42  provides an added degree of assurance to the neurosurgeon that the lever  29  will remain in the closed, locked position until someone in the operating room makes an affirmative decision to unlock the lever  29 . With the base unit  12  of this invention, particularly with the latch  42  as shown and described herein, the first handle assembly  25  could be constructed so that a reduced, or more moderate, amount of opening force is needed to move the lever  29  from the closed position. That could make the first handle assembly  25  more convenient in use. 
         [0041]      FIG. 2A  also shows an additional handle assembly  125  operatively connected to the first handle assembly  25 , via an interconnected link  45 . More specifically, the link  45  includes a pair of parallel, spaced members  46  which are held together by spaced connectors, which include a pair of adjustable knobs  47 . In  FIG. 2A , an innermost end of the link  45  connects to first handle assembly  25  at the second clamp  28 . An opposite or outermost end of the link  45  connects to an additional first clamp  126  located at the first end of the additional handle assembly  125 . Just as first clamp  26  is aligned along the first axis  34 , the additional first clamp  126  includes an additional bore  133  aligned along an additional first axis  134 . 
         [0042]    As with the first handle assembly  25 , the additional handle assembly  125  also includes an additional second clamp  128 , located at a second end thereof, and an additional elongated body  127  which extends along the additional handle assembly  125  and defines an additional longitudinal axis  130 . 
         [0043]    The additional handle assembly  125  includes an additional lever  129  and an additional latch,  142 , which essentially operate in the same manner as the lever  29  and the latch  42  previously described with respect to  FIG. 1 . That is, when the lever  129  moves to a closed position, which in  FIG. 2A  is shown adjacent the additional elongated body  127 , the additional second clamp  128  and the additional first clamp  126  are closed to their smaller dimension, tightened configuration, to prevent rotational movement about additional first axis  134  and additional second axis  136 . In this closed position, the additional second clamp  128  is also prevented from axially rotating about additional longitudinal axis  130 . 
         [0044]    Conversely, when the additional lever  129  is moved to an open position, the additional handle assembly  125  is axially rotatable about additional axis  130 , relative to additional first clamp  126 , as shown by reference arrows  141 . And there is also rotational capability about spaced first and second additional axes  134  and  136 , as shown by directional arrows  139  and  140 . 
         [0045]    In this way, the first handle assembly  25  and the additional handle assembly  125  are stacked, or cascaded in series, via the intervening link  45 . Importantly, the link  45  is in one sense a passive interconnection element, because it can remain secured to the second clamp  28  and the additional first clamp  126 , if desired. In other words, the spaced knobs  47  do not have to be manipulated every time this head support system  110  is used. When the link  45  remains fixed, the two like handle assemblies  25  and  125  provide seven degrees of freedom when both levers  29  and  129  are open. And by the simple closing motion of these levers  29 ,  129 , these seven degrees of freedom are prevented. 
         [0046]    At the outermost end of this head support structure  110 , the additional second clamp  128  holds a modified transition member  50 . This modified transition member  50  includes a body  137  and a transverse hub  140  which extends along the additional second axis  136  of the additional second clamp  128 . This modified transition member  50  includes a connecting surface which includes a starburst ratchet connection  51  and a threaded connector which is controllable via a knob  52 , in cooperation with the starburst connection  51 . Preferably, the knob  52  is operable to securely hold a head holding device in position relative to the modified transition member  50 . In that way, only levers  29  and  129  need to be opened in order to manipulate the head support system  110  into a desired position, and then closed in order to fix the modified transition member  50 , and the head holding device attached thereto, in that desired position. 
         [0047]      FIG. 2B  shows a conventional three pin skull clamp  58  connected to the modified transition member  50 , in essentially the same way that conventional skull clamps connect to conventional swivel adaptors.  FIG. 2B  also shows the rods  16  and  17  connected to a medical table  60 . With the head support system  210  as shown in  FIG. 2B , multiple degrees of freedom are achieved by opening the levers  29  and  129  of the first handle assembly  25  and the additional handle assembly  125 . For instance, with both levers  29  and  129  in the open position, all the structural components which are outboard of the first clamp  26  are translatable along the connecting tube  20 , rotatable with respect to the connecting tube  20 , and rotatable about axis  30 , as represented by directional arrows  41 . Additionally, all of the components outboard of second clamp  28  are rotatable with respect to second axis  36 . Everything outboard of additional first clamp  126  is rotatable with respect to additional first axis  134 , and also axially rotatable about axis  130 , as shown by directional arrows  141 . All components outboard of the additional second clamp  128  are also rotatable with respect to the additional second axis  136 . 
         [0048]    This head support system  210  has multi-directional capability for positioning the skull clamp  58  in a desired position relative to the medical table  60  by providing seven degrees of freedom relative to the medical table  60 . This head support system  210  can be maneuvered into virtually any desired position. And particularly because of the axial rotatability about axes  30  and  130 , as shown via reference numerals  41  and  141 , this head support system  210  achieves an almost snake-like movement to the desired position. 
         [0049]      FIG. 2C  shows the same structural components as previously shown in  FIG. 2A . Thus,  FIG. 2C  uses the same reference numerals for those some components. Nonetheless,  FIG. 2C  shows the capability for axially rotating the body  27  of the first clamp assembly  25  with respect to its longitudinal axis  30 , to reorient the second axis  36  of the second clamp  28  to an orientation that is no longer parallel with the first axis  34  of the first clamp  26 . Thus,  FIG. 2C  also shows that the lever  29  and the additional lever  129  do not need to be aligned when in use. 
         [0050]      FIG. 2D  shows a side view of the same structure shown in  FIGS. 2A and 2C . Therefore, identical reference numerals are again used in  FIG. 2D . 
         [0051]      FIGS. 2E and 2F  illustrate the ability to connect the rods  16  and  17  to the table so that the brackets  18  and  19  extend either upwardly, as shown on the left, or downwardly, as shown on the right. The body  27  rotates with respect to the cross bar  20  to accommodate this. These two different configurations produce a difference in vertical height of about 8 inches. 
         [0052]    With prior base units, it was theoretically possible to connect the brackets so as to extend either downwardly or upwardly. However, the lever position was axially fixed relative to the body. Thus, such an inversion of the brackets would place the lever on the inside of the body, between the table and the body of the base unit. In that location, the lever would be difficult to open and close. In contrast, with the present invention, regardless of whether the brackets  18  and  19  extend upwardly or downwardly, the body  27  can be axially rotated to place the lever  29  outboard, or outside of, the body  27 . 
         [0053]      FIG. 3A  shows the first handle assembly  25  with the lever  29  in an open position, and  FIG. 3B  shows the same view with the lever  29  in a closed position. In  FIG. 3A , the phantom lines within the first clamp  26  and within second clamp  28  show the reduced internal dimensions of the clamps when lever  29  is closed, as is known.  FIG. 3A  also shows an extension bar  62  which operatively connects to the lever  29 , via a linkage  64  and a pin  65 , at the second end of the body  27 . At the first end of the body  27 , the extension bar  62  has external threads which cooperate with internal threads of a T-shaped collar  68 , which also has an axial bore therethrough. This structure fixes a first end  70  of the extension bar  62  to the first end of the body  27 , preferably with a ring  72  mounted at the outer end. 
         [0054]      FIG. 3B  shows the extension bar  62  slightly angled relative to the first end of the handle assembly  25 , when the lever  29  is closed. A set screw threadably holds the extension bar  62  at the first end of the handle assembly  25 , adjacent first clamp  26 . 
         [0055]    In practical terms,  FIGS. 3A and 3B  show that the elongated body  27  of first handle assembly  25  essentially includes a first section  80  located adjacent the first clamp  26 , and a second section  81  located adjacent the second clamp  28 . The extension bar  62  resides within a hollow space  84  defined by the first  80  and second  81  sections. Within this hollow space  84 , the first and second sections  80 ,  81  carry an internal clutch mechanism, preferably two axially aligned ratchets  86 ,  87 . These ratchets  86 ,  87  are biased away from each other, via an axial spring  89 , when the lever  29  is in the open position. When the lever  29  is closed, the axial pulling force applied by extension bar  62  overcomes the bias of the spring  89 , to move the ratchets  86 ,  87  axially closer together to cause the axially opposed ratchet teeth thereof to intermesh, to thereby prevent relative rotation of the second section  81  and the first section  80  with respect to axis  30 . Thus, it is this internally located clutch mechanism, preferably a pair of axially spaced, spring-biased ratchets  86 ,  87 , which permits or prohibits rotation of the second section  81  relative to the first section  80  about axis  30 . 
         [0056]      FIGS. 3A and 3B  also show a sleeve  32  located adjacent first clamp  26 . This sleeve provides additional structural integrity to the first handle assembly  25 , adjacent to the first clamp  26 . Aside from this sleeve  32  and a slightly shorter longitudinal dimension, the additional handle assembly  125  is in all material respects the same as the first handle assembly  25 . In other words, the additional handle assembly  125  is like first handle assembly  25  in terms of functionality, i.e. axial rotatability, and the structure which supplies this functionality, although the relative shapes of these components may vary, as desired. 
         [0057]      FIG. 4  shows an exploded view of the components of the first handle assembly  25 .  FIG. 4 , in connection with  FIGS. 3A and 3B , also shows the structural details of the latch  42  which is held by a spring  75 , to enable it to be moved in trigger-like fashion toward lever  29  in order to release lever  29  from the locked position. This trigger-like mechanism includes a catch  76  which engages a complementarily shaped surface formed on one component  64   b  of the linkage  64 , the components of the linkage  64  are designated via reference numerals  64   a,    64   b,    64   c,  and  64   d,  and they generally correspond to structure used in conventional base units, as is known in this field. 
         [0058]      FIG. 5  shows a transverse cross sectional view along cross sectional line  5 - 5  of  FIG. 2D . More particularly,  FIG. 5  shows the internal structure of the link  45 , which interconnects the first handle assembly  25  with the additional handle assembly  125 . More specifically,  FIG. 5  shows a portion of the second clamp  28 , and a portion of the additional first clamp  126 , surrounding spaced hub-like portions of member  46   a.  A complementarily-shaped member  46   b  includes protruding sections which extend into recesses formed within the hubs of member  46   a.  The two opposing members  46   a  and  46   b  are held in place on the second clamp  28  and the first additional clamp  126  by tightening the knobs  47 , to achieve securement via the threads at the internal ends  58  thereof. This interconnects the link  45  to the first handle assembly  25  and the additional handle assembly  125 , while still permitting rotation about axis  36  and also axis  134 . 
         [0059]      FIG. 5  shows that the knobs  47  can be unscrewed to disconnect the members  46   a  and  46   b,  thereby to disconnect the first handle assembly  25  and the additional handle assembly  125 . 
         [0060]    The present invention also contemplates that the locking feature could be adapted to existing conventional based units. More specifically,  FIG. 6  shows a conventional handle assembly  325  with spaced first and second clamps  326  and  328 , an elongated body  327 , and a lever  329  which has been modified to be secured in the locked position. More specifically, a wire catch  342  is mounted to a free end of the lever  329 . The wire catch  342  secures to an existing bolt  322  located adjacent the first clamp  326 . The wire catch  342  is rotatable relative to the lever  329 , to enable affirmative locking of the lever  329 , or affirmative unlocking of the lever  329 . 
         [0061]    While the present application discloses and describes a particular structure for achieving axial rotatability of first and second sections of a handle assembly in a head support system, those skilled in the art will appreciate that the disclosed material represents the presently preferred embodiments of this invention. Those skilled in the art will readily appreciate that the various aspects and embodiments shown in the present application are susceptible to reasonable structural modification, without departing from the invention. Applicants understand that the claims appended hereto will be read and interpreted in light of this specification, but applicants do not intend for the specific structural details of the specification to be read into these claims. Thus, applicants intended that the following claims should be interpreted as broadly as reasonable possible, to encompass the full scope of this invention.