Abstract:
Surgical clamping instruments include a distal portion having distal tips configured to be driven to provide clamping force to multiple tissue pieces; a proximal portion including a compression actuator configured for operation by a user to drive the distal tips to apply compression force to the tissue pieces, and a shear actuator configured for operation by the user to drive the distal tips to apply shear force to the tissue pieces; and an intermediate portion interconnecting the proximal and distal portions. A method of joining tissues pieces together includes applying first and second force applicators to first and second surfaces of first and second tissue pieces, wherein the first and second surfaces oppose third and fourth surfaces of the first and second tissue pieces to be joined, respectively; applying compressive force, via the first and second force applicators, to drive the first and second pieces together; and applying shear force, via said first and second force applicators, to accurately align the third and fourth surfaces, so that the third and fourth surfaces are contacted to one another in a desired fit pattern.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates broadly to clamping instruments used in orthopedic surgery and methods of using the same during such surgery. 
       BACKGROUND OF THE INVENTION 
       [0002]    A reduction clamp or tenaculum is a simple hardware tool used by orthopedic surgeons to hold pieces of bone together during surgery. This tool has essentially the same design as an ordinary clamp used by a carpenter and sold in a hardware store. The main difference is that clamps used for bone usually have sharp points and close with precision. Like ordinary clamps, there is a locking mechanism so that compression can be maintained between the points of the clamp. 
         [0003]    U.S. Pat. No. 4,475,544 to Reis discloses a forceps-type bone clamp having distal pointed ends that are turned inwardly toward one another. A ratcheting mechanism is provided near the proximal end of the clamp, between scissors-type handles, so that a clamping force can be maintained. This type of design allows for the creation of a compressive force that is always directed between the points of the clamp. The ease of use of this instrument depends entirely on the orientation of the two surfaces being compressed. If the clamp can be positioned perpendicular to the surfaces, then pure compression will occur. If, on the other hand, the clamp is not perpendicular to the plane of desired compression, then the clamp will cause shear as well as compression. This can be problematic, because it is generally intended to clamp the broken pieces back together by driving them in a straight line of compression toward one another. The shearing force can drive the bone pieces out of alignment, so that when the bone pieces make contact as a result of the combined shear and compression forces, the bones are out of alignment relative to the positions that the orthopedic surgeon intended to join them in. Proper alignment of the bones is extremely important in order to minimize occurrences of nonunion, among other issues. 
         [0004]    In order to correct for the misalignment caused by the shear forces, a second (and maybe even a third or more) clamp(s) are required to provided a compression force to drive the misaligned bone pieces toward the intended positions where they are properly aligned. This becomes critical during fracture surgery. It is often difficult to fit one clamp into the operative field, let alone two. Multiple clamps protruding from the surgical wound make access difficult for the drills and screwdrivers that must be inserted in order to repair the fracture. 
         [0005]    Thus, there is a need for clamping instruments and methods that can produce a force vector that is not limited to the line connecting the points on the bone pieces to be clamped, i.e., that is not limited to providing compressive force along a single line, such as what the clamps of the prior art are limited to. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention provides clamping instruments including: a distal portion having distal tips configured to be driven to provide clamping force to multiple tissue pieces; a proximal portion including a compression actuator configured for operation by a user to drive the distal tips to apply compression force to the tissue pieces, and a shear actuator configured for operation by the user to drive the distal tips to apply shear force to the tissue pieces; and an intermediate portion interconnecting the proximal and distal portions. 
         [0007]    In at least one embodiment, a relative position locking mechanism is configured to temporarily maintain the distal tips in constant relative positions to apply a constant amount of compression. 
         [0008]    In at least one embodiment, a relative position locking mechanism configured to temporarily maintain the distal tips in constant relative positions to apply a constant amount of shear. 
         [0009]    In at least one embodiment, the instrument comprises a bone clamp. 
         [0010]    In at least one embodiment, the tissue pieces are fractured pieces of a bone. 
         [0011]    In at least one embodiment, the distal portion comprises a pair of elongate shafts, each provided with one of the distal tips at a distal end thereof. 
         [0012]    In at least one embodiment, the distal tips are directed inwardly toward one another. 
         [0013]    In at least one embodiment, the intermediate portion comprises first and second supports, a first of the distal tips being connected to the first support and a second of the distal tips being connected to the second support, the shear actuator being operable to drive a relative tilting action between the first and second supports to generate the shear force in the distal tips. 
         [0014]    In at least one embodiment, the intermediate portion comprises first and second supports, a first of the distal tips being connected to the first support and a second of the distal tips being connected to the second support, the compression actuator being operable to drive a relative rotation action between the first and second supports to generate the compression force in the distal tips by driving the distal tips toward one another. 
         [0015]    In at least one embodiment, the intermediate portion comprises first and second supports, the first and second supports being connected via a joint that permits relative rotation between the first and second supports and relative tilting between the first and second supports. 
         [0016]    In at least one embodiment, the joint comprises a swivel bearing. 
         [0017]    In at least one embodiment, the intermediate portion comprises a shear driver pivotally fixed to the intermediate portion and configured to provide a driving force against one of the first and second supports, when driven by the shear actuator, to tilt one of the first and second supports relative to the other of the first and second supports. 
         [0018]    A method of joining tissues pieces together is provided, including the steps of: applying first and second force applicators to first and second surfaces of first and second tissue pieces, wherein the first and second surfaces oppose third and fourth surfaces of the first and second tissue pieces to be joined, respectively; applying compressive force, via the first and second force applicators, to drive the first and second pieces together; and applying shear force, via the first and second force applicators, to accurately align the third and fourth surfaces, so that the third and fourth surfaces are contacted to one another in a desired fit pattern. 
         [0019]    The first and second force applicators can be provided as distal tips of a single clamping instrument according to the present invention. 
         [0020]    In at least one embodiment, the tissue pieces are bone pieces, and the first and second force applicators are portions of a single bone clamping instrument. 
         [0021]    In at least one embodiment, the application of compressive force is performed first, followed by fine tuning of alignment of the pieces by the application of shear forces. 
         [0022]    In at least one embodiment, the compressive force and the shear force are applied simultaneously. 
         [0023]    In at least one embodiment, the application of compressive force and the application of shear force are alternatively and iteratively adjusted to accurately align the tissue pieces and clamp them together to contact the third and fourth surfaces together in accurate alignment. 
         [0024]    A method of accurately clamping fractured bone pieces together with a single bone clamp is provided, including the steps of: applying first and second distal tips of the bone clamp to first and second surfaces of first and second bone pieces, wherein the first and second surfaces oppose third and fourth fracture surfaces of the first and second bone pieces to be joined, respectively; applying compressive force, via the first and second distal tips, to drive the first and second pieces together; and applying shear force, via the first and second distal tips, to accurately align the third and fourth fracture surfaces, so that the third and fourth fracture surfaces are contacted to one another in a desired fit pattern. 
         [0025]    The application of compressive force and the application of shear force can be independently controlled via a compression actuator and a shear actuator, respectively, provided in a proximal portion of the bone clamp. 
         [0026]    These and other features of the invention will become apparent to those persons skilled in the art upon reading the details of the instruments and methods as more fully described below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]      FIG. 1  illustrates a prior art forceps-type bone clamp. 
           [0028]      FIG. 2A  schematically illustrates a situation in which the distal tips of a clamp are capable of being positioned to apply pure compressive force perpendicular to surfaces of two pieces of bone to be rejoined during surgery. 
           [0029]      FIG. 2B  schematically illustrates a situation in which the distal tips of the clamp of  FIG. 1  are not capable of being positioned to apply compressive force perpendicular to surfaces of two pieces of bone to be rejoined during surgery. 
           [0030]      FIG. 2C  illustrates movements of the bone pieces  1 ,  2  into misalignment, as a result of application of force in a manner as described with regard to  FIG. 2B . 
           [0031]      FIG. 2D  illustrates compressive forces applied by a first clamp at one location, and compressive forces applied by a second clamp at a second location, to counter the shear forces resulting from the compressive forces applied at the first location. 
           [0032]      FIG. 3  schematically illustrates application of forces by an instrument according to the present invention to accurately compress the surfaces together in a situation where the fracture is oriented like that described with regard to  FIGS. 2B-2D . 
           [0033]      FIG. 4A  illustrates a plan view of an embodiment of an instrument according to the present invention. 
           [0034]      FIG. 4B  illustrates a perspective view of the instrument of  FIG. 4A , showing the opposite side of the instrument. 
           [0035]      FIG. 5  is an exploded view of the instrument shown in  FIG. 4B . 
           [0036]      FIG. 6  is a partial, enlarged side view of the instrument of  FIG. 5  showing the assembled components of the intermediate portion. 
           [0037]      FIG. 7A  is a partial view of an alternative embodiment according to the present invention. 
           [0038]      FIG. 7B  is an enlarged partial view of  FIG. 7A . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0039]    Before the present instruments and methods are described, it is to be understood that this invention is not limited to particular embodiments described, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of the present invention will be limited only by the appended claims. 
         [0040]    Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limits of that range is also specifically disclosed. Each smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in that stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range, and each range where either, neither or both limits are included in the smaller ranges is also encompassed within the invention, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the invention. 
         [0041]    Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are now described. All publications mentioned herein are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the publications are cited. 
         [0042]    It must be noted that as used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a handle” includes a plurality of such handles and reference to “the arm” includes reference to one or more arms and equivalents thereof known to those skilled in the art, and so forth. 
         [0043]    The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present invention is not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided may be different from the actual publication dates which may need to be independently confirmed. 
         [0044]      FIG. 1  illustrates a prior art forceps-type bone clamp  1000  having distal pointed ends  1002  that are turned inwardly toward one another. A ratcheting mechanism  1004  is provided near the proximal end of the clamp, between scissors-type handles  1006 , so that a clamping force can be maintained. This type of design allows for the creation of a compressive force that is always directed between the points  1002  of the clamp  1000  along a single line. The ease of use of this instrument depends entirely on the orientation of the two surfaces being compressed. If the clamp can be positioned perpendicular to the surfaces, then pure compression will occur. If, on the other hand, the clamp is not perpendicular to the plane of desired compression, then the clamp will cause shear as well as compression. This can be problematic, because it is generally intended to clamp the broken pieces back together by driving them in a straight line of compression toward one another. The shearing force can drive the bone pieces out of alignment, so that when the bone pieces make contact as a result of the combined shear and compression forces, the bones are out of alignment relative to the positions that the orthopedic surgeon intended to join them in. Proper alignment of the bones is extremely important in order to minimize occurrences of nonunion, among other issues. 
         [0045]      FIG. 2A  schematically illustrates a situation in which the distal tips  1002  of clamp  1000  are capable of being positioned to apply compressive force perpendicular to surfaces  1   s ,  2   s  of two pieces of bone  1 , 2  to be rejoined during surgery. This situation is ideal for the application of clamping forces by clamp  1000  as forces can be applied along a straight line that is perpendicular to the surfaces  1   s ,  2   s  as shown. Accordingly, surfaces  1   s ,  2   s  can be clamped together without misalignment, as the surfaces are driven together along the direction of the line shown in dashed lines in  FIG. 2A . Unfortunately, this situation is not very common, as the situation much more often presents with the fracture surfaces  1   s ,  2   s  of the bones being oriented such that the tips  1002  can not be aligned perpendicular to the surfaces. 
         [0046]      FIG. 2B  schematically illustrates a situation in which the distal tips  1002  of clamp  1000  are not capable of being positioned to apply compressive force against surfaces  3   s ,  4   s  to apply forces perpendicular to surfaces  1   s ,  2   s  of two pieces of bone  1 , 2  to be rejoined during surgery. Accordingly, when distal tips  1002  are contacted to the surfaces  3   s ,  4   s  of bone pieces  1 ,  2  as illustrated in  FIG. 2B , and compressive force is applied between the two tips  1002  along the direction of dashed line  1010 , the resultant force components from this action include a compression in the direction of line  1012 , as well as shear force in the direction of a line perpendicular to line  1012 .  FIG. 2C  illustrates the movements of the bone pieces  1 ,  2  into misalignment, as a result of application of force in a manner as described with regard to  FIG. 2B . Specifically, application of compression forces by the clamp tips  1002  along the line  1010 , as indicated by the arrows aligned with line  1010 , drives pieces  1 ,  2  in compression into contact with one another, but also drives pieces  1 , 2  in the directions of the shear force arrows  1014 . This results in the surfaces  1   s ,  2   s  becoming misaligned as they contact one another, such that the bone surfaces are not contacted back together in the same relative orientations that they were in prior to the bone breaking, when the surfaces  1   s ,  2   s  were created. 
         [0047]    Since a goal of the surgery is to reconstruct the bone as close to possible as it was prior to the fracture, the result in  FIG. 2C  is unacceptable, and the bone pieces  1 ,  2  must be repositioned prior to be fixed together (e.g., such as by screws, pins, plates, or some other technique known in the art). In order to correct this situation, the shear forces need to be negated or neutralized, and this is typically done by applying one or more additional clamps at different orientations. For example,  FIG. 2D  illustrates compressive forces applied by a first clamp  1000  via clamp tips  1002  at arrows  1016 ,  1016  to apply force in the same manner as described above with regard to  FIGS. 2B-2C . Additionally, compressive forces are applied by a second clamp  1000  via tips  1002  in the locations indicated by arrows  1018  to counter the shear forces resulting from the compressive forces applied at arrows  1016 ,  1016 . Sometimes a third or more clamps  1000  are required to be applied to correct the forces so as to fit the bone pieces  1 ,  2  back together correctly under clamping. As noted above, this can be problematic because it is often difficult to fit one clamp into the operative field, making it much more difficult, or impossible to fit a second clamp or more. Additionally, the requirement to place multiple clamps takes more time, increasing the cost of the surgical procedure and potentially also increasing risks. Further, the presences of multiple clamps protruding from a surgical wound makes access by other instruments more difficult, e.g., drills, screwdrivers, etc. 
         [0048]    The present invention provides a single instrument that is capable of applying a compressive force between two points, like that described with regard to clamp  100  above, while it can additionally apply a shear force so as to negate the need for one or more additional clamps in a situation such as that described above with regard to  FIGS. 2B-2D . Instruments described herein are particularly useful in orthopedic surgery, for clamping bone to bone, or implants (such as metal or ceramic plates, or the like) to bone, although these instruments may be useful for clamping other tissues as well.  FIG. 3  schematically illustrates application of forces by an instrument according to the present invention to accurately compress the surfaces  1   s ,  2   s  together in a situation where the fracture is oriented like that described above with regard to  FIGS. 2B-2D . In this case, instrument  10  is arranged so that distal tips  12  contact the bone pieces  1  and  2  in the same locations as described above with regard to  FIG. 2B . Instrument  10  can be operated to apply compressive forces between the two tips  12  in a direction along the line  1010  in the same manner as clamp  1000 , which is adequate if the surfaces  1   s ,  2   s  are perpendicular to line  1010 , as noted above. However, in situations such as the one shown in  FIG. 3 , instrument  10  can be operated to additionally apply a shear force between tips  12 , so that the combined force vector compresses the bone surfaces  1   s ,  2   s  together in the intended relative positions, without shearing the pieces away from one another. Arrow  100  indicates the direction of the compressive force applied by the upper tip  12  relative to the second tip  12  and arrow  102  indicates the direction of the perpendicular force applied by the upper tip  12  relative to the second tip  12 . Arrow  104  indicates the combine force, i.e., resultant force vector  104 , which is perpendicular to the surfaces  1   s ,  2   s.    
         [0049]      FIG. 4A  illustrates a plan view of an embodiment of an instrument  10  according to the present invention, and  FIG. 4B  illustrates a perspective view showing the opposite side of the instrument  10  of  FIG. 4A . Instrument  10  includes first and second elongated shafts  14  at a distal portion thereof configured to be rotated or pivoted toward or away from one another. Distal tips  12  are directly inwardly toward one another, so that when instrument  10  is operated solely in compression, tips  12  can be driven toward one another along a force line that interconnects the aligned tips  12  (e.g., line  1010  in  FIG. 3 ) Force arrows  106  illustrate the direction of application of the compressive forces described. 
         [0050]    Compression actuators  16  are included in a proximal portion of instrument  10  and are configured to be manually operated by a user (e.g., surgeon or other medical personnel) to apply compression via tips  12 . In the example of  FIG. 4A , compression actuators  16  each include an elongated shaft  16   s  and a loop  16   p  that facilitates ease of operation, by allowing the user to insert a finger or thumb through each loop  16   p . However, it is noted that the present invention is not limited to shaft and loop type compression actuators  16 , as compression actuators may take other forms. For example, instead of loops  16   p , curved handles, such as concave shaped handles may be provided. Further alternatively, convex shaped handles  116  may be provided to replace the shafts  16  and loops  16   p  of the device  10  shown in  FIG. 4A , as illustrated in the partial view of an alternative device embodiment  10  shown in  FIG. 7A . Further alternatively, shafts  16   s  can be interconnected by a threaded, spring-loaded rod, such that threading a nut down on the rod drives shafts  16   s  closer together, while back-threading allows the spring to drive the shafts  16   s  further apart. Many other configurations may be substituted to perform the compression driving function, as would be readily apparent to one of ordinary skill in the mechanical arts. 
         [0051]    A relative position locking mechanism  18  is provided on compression actuators  16  to lock compression actuators in their current positions relative to one another until such time as the user decides to alter the relative positions. In the example shown in  FIGS. 4A and 4B , relative positioning locking mechanism  18  comprises a ratcheting mechanism in which a curved, toothed, ratchet arm  18   a  extends transversely away from the shaft  16   s  that it is connected to, towards and beyond the other shaft  16   s . The other shaft includes a ratchet catch  18   c  mounted thereon, in a location to interact with the teeth on ratchet arm  18   a  to form a temporary lock therewith. The ratchet arm  18   a  and catch  18   c  engage with one another to lock the positions of arms  16   s  relative to one another, which is useful to maintain a constant amount of compression between tips  12  during use of instrument  10 . This locking mechanism can be released by separating the teeth of ratchet arm  18   a  from catch  18   c , by moving the ratchet arm  18   a  and/or the catch  18   c  perpendicularly to the direction that they move relative to one another during increasing or decreasing the distance between arms  16   s . Relative position locking mechanism  18  is not limited to the ratchet mechanism described above and shown in  FIGS. 4A-4B , as other types of relative position locking mechanisms may be substituted. For example, in the case where shafts  16   s  are interconnected by a threaded, spring-loaded rod, the nut and threaded rod also function as a relative position locking mechanism.  FIG. 7B  is an enlarged partial view of  FIG. 7A  that illustrates an alternative ratchet and locking arrangement  118   a ,  118   c . Many other configurations may be substituted to perform the relative position locking function, as would be readily apparent to one of ordinary skill in the mechanical arts. 
         [0052]    Shear actuator  20  is included in a proximal portion of instrument  10  and is configured to be manually operated by a user (e.g., surgeon or other medical personnel) to apply shear via tips  12 . In the example of  FIGS. 4A-4B , shear actuator  20  includes an elongated shaft  20   s  and a loop  20   p  that facilitates ease of operation, by allowing the user to insert a finger or thumb through loop  20   p  to facilitate non-slip operation. However, it is noted that the present invention is not limited to shaft and loop type shear actuator  20 , as shear actuator  20  may take other forms. For example, instead of loop  20   p , a curved handle or other handle shaped to facilitate manipulation by a user may be provided. Further alternatively, shafts  20   s  can be interconnected to adjacent shaft  16   s  by a threaded, spring-loaded rod, such that threading a nut down on the rod drives shaft  20   s  toward shaft  16   s , while back-threading allows the spring to drive the shafts  20   s  away from shaft  16   s . Many other configurations may be substituted to perform the shear actuation or driving function, as would be readily apparent to one of ordinary skill in the mechanical arts. 
         [0053]    A relative position locking mechanism  28  is provided to lock a relative position of shear actuator  20  relative to the adjacent compression actuator shaft  16   s , until such time as the user decides to alter the relative position of the shear actuator  20   s . In the example shown in  FIGS. 4A and 4B , relative positioning locking mechanism  28  comprises a ratcheting mechanism in which a curved, toothed, ratchet arm  28   a  extends transversely away from the shaft  20   s  that it is connected to, towards and beyond the adjacent shaft  16   s . The adjacent shaft  16   s  includes a ratchet catch  28   c  mounted thereon, in a location to interact with the teeth on ratchet arm  28   a  to form a temporary lock therewith. The ratchet arm  28   a  and catch  28   c  engage with one another to lock the position of arm  20   a  relative to the adjacent arm  16   s , which is useful to maintain a constant amount of shear between tips  12  during use of instrument  10 . This locking mechanism can be released by separating the teeth of ratchet arm  28   a  from catch  28   c , by moving the ratchet arm  28   a  and/or the catch  28   c  perpendicularly to the direction that they move relative to one another during increasing or decreasing the distance between arm  20   s  and adjacent arm  16   s . Relative position locking mechanism  28  is not limited to the ratchet mechanism described above and shown in  FIGS. 4A-4B , as other types of relative position locking mechanisms may be substituted. For example, in the case where shaft  20   s  and adjacent shaft  16   s  are interconnected by a threaded, spring-loaded rod, the nut and threaded rod also function as a relative position locking mechanism. Many other configurations may be substituted to perform the relative position locking function, as would be readily apparent to one of ordinary skill in the mechanical arts. 
         [0054]      FIG. 5  is an exploded view of instrument  10  in the orientation shown in  FIG. 4B , and is provided to better illustrate the shear mechanism in the intermediate portion  30  of instrument  10  as well as the connections of the shafts to the intermediate portion. Intermediate portion  30  includes first and second support members  32  and  34 , respectively, interconnected to one another to allow rotation of each support member  32 , 34  about transverse axis  36  and relative to each other, to effect compression, for example, as well as tilting of the support members  32 , 34  relative to one another to effect shear, for example. A first of the pair of shafts  16   s  and a first of the pair of shafts  14  are rigidly connected to first support member  32  to oppose one another so that movement of the first shaft  16   s  in one direction rotates support member  32  to drive the first shaft  14  in the opposite direction. Likewise, the second of the pair of shafts  16   s  and the second of the pair of shafts  14  are rigidly connected to second support member  34  to oppose one another so that movement of the first shaft  16   s  in one direction rotates support member  32  to drive the first shaft  14  in the opposite direction. 
         [0055]    A swivel bearing  36  interconnects first and second support members  32 ,  34  to allow relative rotational movements as well as relative tilting movements between the support members  32 ,  34 . A securing mechanism, such as a pin, rivet, or nut and bolt, or the like are provided through support members  32 , 34  and swivel bearing  36  to secure the components together. Clearance is provided for the holes in support members  32 , 34  and swivel bearing  36 , so that they have larger inside diameters than the outside diameter of the securing mechanism that passes therethrough, to permit relative motion of support members  32 , 34  about swivel bearing  36 , including both rotational and tilting movements. 
         [0056]    A shear driver  38  (e.g., lever, or the like) is partially inserted through a slot  40  in first support member  32 . Shear driver  38  is also hingedly or pivotally connected to support member  32  at hinge or pivot point  42  via a hinge or pivot joint. Shaft  20   s  is hingedly or pivotally connected to an external surface of support member  32  at hinge or pivot point  44 . Upon actuation of shear actuator  20  by moving it in a direction toward the adjacent shaft  16   s , this causes the distal end portion of shaft  20   s  to drive against a portion of shear driver  38  that extends out of support member and is located on one side of joint  42 . This rotates shear driver, thereby driving the portion of shear driver on the other side of joint  42  against support member  34 , thereby tilting support member  34  relative to support member  32  and causing a shearing force to be delivered through distal tips  12  when they are engaged with surfaces, such as bone pieces, for example. In  FIG. 5 , the action just described causes the right side of support member to move downward (away) from the right side of support member  32 , thus effecting shear forces in the directions of arrows  108  in  FIG. 5 . Upon release of the relative position locking mechanism  28  and movement of arm  20   s  away from the adjacent arm  16   s , this allows support member to return in a direction toward the untilted configuration shown in  FIG. 5 . It is further noted that shear driver  38  could alternatively be activated by a cam mechanism or a cable assembly attached to arm  20 . Alternatively to use of lever as shear driver  38 , a wedge may be used to drive the two support members  32 ,  34  apart on one side. The wedge can be driven by a shaft or screw mechanism. 
         [0057]      FIG. 6  is a partial, enlarged side view of instrument  10  showing the assembled components of the intermediate portion. Application of force against shear driver  38  by the distal end portion of shaft  20   s  in the direction indicated by the arrow causes rotation of shear driver  38  in the direction shown by the rotational arrow, such that the internally contained portion of shear drive  38  drives against support member  34  causing it to tilt about swivel bearing  36  in the same rotational direction as the rotational direction of shear driver  38 . This cause a shearing action by driving the distal tip extending from the shaft  14  on the right side of  FIG. 6  downward relative to the distal tip extending from the shaft  14  on the left side of  FIG. 6 . 
         [0058]    When using instrument  10  to clamp together tissue pieces, such as fractured bone pieces, or other tissues to be clamped, distal tips  12  are contacted to the tissue pieces on surfaces opposite the surfaces of the tissue pieces to be joined. Distal tips  12  may be pointed or sharpened to facilitate engagement of the tips  12  with the tissue, and prevent slippage between the tips  12  and the tissue during clamping. Pointed or sharpened tips  12  can be particularly useful when the tissue pieces to be clamped are bone. 
         [0059]    Compression actuators  16  can next be operated by the user to begin driving the tissue pieces together, by the movement of tips  12  toward one another. This action can continue until a the fractured surfaces contact one another, at which time, shear actuator  20  can be operated by the user to fine tune the alignment of the pieces, should any misalignment have occurred due to shear forces generated during the application of compression force by compression actuator  16 . Once the tissue pieces have been accurately aligned by adjustment by the shear actuator  20 , the compression actuator  16  can be further actuated to apply additional compressive force to securely clamp the pieces together. After each actuation of the compressive actuators  16 , the relative positions of the actuators are locked by locking mechanism  18 . After each actuator of shear actuator  20 , the position of shear actuator  20  relative to the adjacent compression actuator shaft  16   s  is locked by locking mechanism  28 . 
         [0060]    Alternatively, compression actuators  16  and shear actuator  20  may be operated simultaneously, to adjust the tracking of the pieces as they are being joined together under compression, with shear adjustments being made as necessary according to feedback provided by visualization by the user of the relative positions of the pieces as they are being driven together. 
         [0061]    Further alternatively, compression and shear may be alternatively and iteratively adjusted to effect an accurate fitting together of the pieces. For example, as the pieces are brought closer together by application of compressive forces, the user may note that the pieces are becoming misaligned. At that time, the relative positions of the tips under compression are maintained by locking mechanism  18  and shear actuator  20  is actuated to apply shear force to correct the alignment of the pieces. The relative positions of the tips  12  under shear are maintained by locking mechanism  28  and then additional compressive force can be applied via actuators  16  to being the pieces closer together. If this causes another misalignment, then additional shear force can be applied, and this process can continue iteratively until the pieces have been brought into contact under accurate alignment and with sufficient clamping force. 
         [0062]    Preferably, the compression and shear forces are applied sequentially to maintain alignment of the pieces as they are driven together. 
         [0063]    While the present invention has been described with reference to the specific embodiments thereof, it should be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the true spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation, material, composition of matter, process, process step or steps, to the objective, spirit and scope of the present invention. All such modifications are intended to be within the scope of the claims appended hereto.