Abstract:
A tightenable joint for use in a surgical retractor system includes a monolithic, unitary joint body which has a top leg and a bottom leg. The top leg provides a top compression surface and the bottom leg provides a bottom compression surface operating on a ball. A handled cam is used between proximal ends of the top leg and the bottom leg. When the handle is thrown to tighten the joint, the proximal ends of the top leg and the bottom leg are driven apart by the cam, and a hinge or fulcrum portion on the joint body flexes between top and bottom leg portion such that the top compression surface and bottom compression surface tighten on the ball. The ball has flats that enable the ball to be positioned into the socket, and then an extension is fixed to the ball to prevent removal of the ball from the socket. The cam is defined with an eccentric surface relative to its pivot pin, which is received in an arcuate recess of a bearing plate. When the handle is thrown, the bearing plate slides relative to the joint body under the cam.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    None. 
       BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to the field of surgical tools, and particularly to the design and manufacture of surgical retractor systems. Surgical retractor systems have long been used during surgery to bias and hold tissue in a desired position. In many retractor systems, clamps and joints are used which have a loosened position in which the post, shaft, retractor blade and/or other portions of the assembly can be easily moved, and a tightened position in which the connection is held rigid. 
         [0003]    Numerous such surgical retractor clamps and joints exist in the prior art. Many surgical retractor clamps operate on bar stock of other components of the surgical retractor systems. In some surgical retractor systems the bar stock is generally cylindrical, and the cylindrical bar stock can be positioned at incrementally different positions relative to the clamp by rotating the bar stock about its longitudinal axis (or vice versa). In other surgical retractor systems including systems known as “Bookwalter/Codman” systems, the bar stock is rectangular in cross-section or otherwise has longitudinally extending flatted sides. The flatted sides of the bar stock generally prevent any rotational movement or slippage of the bar stock about its longitudinal axis relative to the clamp, but also eliminated the possibility of fine adjustment of the circumferential position of the flats. 
         [0004]    Ball-and-socket joints are well known in a wide variety of fields including the surgical retractor field. Ball-and-socket joints include a generally spherical ball having a ball shaft extending off one side. The ball is placed in a socket that while loosened holds the center of the ball in a set position but permits pivoting, commonly allowing simultaneous pivoting adjustment in pitch, in yaw and in roll. Many ball-and-socket joints can then be tightened to prevent any movement of the ball and ball shaft relative to the socket. If desired, a track or interference structure can be added to ball-and-socket joint to limit or restrict motion in one or more of pitch, yaw and roll, i.e., so the ball is not free to pivot in all directions even while the joint is loosened. However, because ball-and-socket joints generally provide three degrees of freedom (pitch, yaw and roll), they are particularly beneficial when used with flatted bar stock to provide the circumferential adjustment which is otherwise restricted by the flats. 
         [0005]    In some ball-and-socket joints, the dimensions of the socket are essentially fixed, and the tightening action involves pushing or pulling the ball against one side of the socket. As one example, the socket may be formed with a conical profile, perhaps with a flexible bushing between the ball and the conical socket. By advancing the ball relative to the conical socket, the frictional force between the socket and the ball increases, tightening the ball-and-socket joint. In some designs, the force advancing the ball relative to the conical socket is provided by a cable axially threaded through a hole in the ball and in the conical socket. 
         [0006]    In other ball-and-socket joints, the dimensions of the socket change. For instance, the socket may be made up of two different components which are hinged or otherwise moveable relative to each other, with a tightening mechanism that closes the hinged socket portions around the ball. For instance, U.S. Pat. No. 6,602,190, owned by the assignee of the present invention, discloses a multi-position spherical retractor holder which uses a retaining member tightened against the Bookwalter/Codman frame. In other designs, the socket is formed by a hoop around the ball, and tightening of the hoop and increasing hoop stress makes the hoop smaller and increases friction between the hoop and the ball. For instance, U.S. Pat. Nos. 5,899,627 and 6,264,396, owned by the assignee of the present invention, discloses a ball socket clamping device using a hoop stress to tighten around two balls, one on each end of a cylindrical hoop. 
         [0007]    Surgical retractor systems must be robust and strong, as even a possibility of failure during use is not tolerated. Surgical retractor assemblies should be readily reusable, including sterilizable, for use in multiple surgeries. Surgical retractor systems should maintain a relatively low cost, including utilizing as few and simple parts as possible during the manufacturing process. Surgical retractor systems should be easy to use, including as few assembled parts as necessary to minimize assembly time and the possibility of one part being misplaced during use prior to assembly, while still permitting adequate flexibility for the surgeon to perform the desired retraction. The handle or other tightening control should be readily accessible for use, but unobtrusive during the surgical operation. Improvements in surgical retractor systems can be made in keeping with these goals. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    The present invention is a tightenable joint for use in a surgical retractor system. In one aspect, a monolithic, unitary joint body provides both a top compression surface and a bottom compression surface operating on a ball. A hinge or fulcrum portion on the joint body flexes between top and bottom leg portions, and a tightening mechanism operates to spread proximal ends of the legs so the top compression surface and bottom compression surface tighten on the ball. In another aspect, the ball has flats that enable the ball to be positioned into the socket, and then an extension is fixed to the ball to prevent removal of the ball from the socket. In another aspect, the tightening mechanism for the joint includes a cam received in arcuate recesses of a bearing plate, and the bearing plate slides relative to the joint structure during the throw of the handle. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a perspective view of a surgical retractor clamp utilizing a ball-and-socket joint in accordance with a preferred embodiment of the present invention, shown in a loosened position, with the shaft guide subassembly positioned upright. 
           [0010]      FIG. 2  is an exploded perspective view of the component parts in the surgical retractor clamp of  FIG. 1 . 
           [0011]      FIG. 3  is a side view of the joint body of the surgical retractor clamp of  FIGS. 1 and 2 . 
           [0012]      FIG. 4  is a top view of the joint body of the surgical retractor clamp of  FIGS. 1 and 2 . 
           [0013]      FIG. 5  is a front view of the joint body of the surgical retractor clamp of  FIGS. 1 and 2 . 
       
    
    
       [0014]    While the above-identified drawing figures set one or more forth preferred embodiments, other embodiments of the present invention are also contemplated, some of which are noted in the discussion. In all cases, this disclosure presents the illustrated embodiments of the present invention by way of representation and not limitation. Numerous other minor modifications and embodiments can be devised by those skilled in the art which fall within the scope and spirit of the principles of this invention. 
       DETAILED DESCRIPTION 
       [0015]    A surgical retractor clamp  10  representing a preferred embodiment of the present invention includes five primary components: a joint body  12  which provides a socket  14 , a shaft guide subassembly  16  which includes a ball  18 , a jaw  20 , a sliding bearing plate  22  and an actuating handle  24 . The handle  24  is pivotably connected to the joint body  12  by a handle pivot pin  26 . The jaw  20  is pivotably connected to the joint body  12  with a jaw pin  28 . A compression spring  30  is housed between the jaw  20  and the joint body  12 . After the ball  18  has been positioned in the socket  14 , a locking pin  32  is fixed to the ball  18  to prevent removal of the ball  18  from the socket  14 . 
         [0016]    The preferred surgical retractor clamp  10  is designed for use in ways similar to the multi-position spherical retractor holder of U.S. Pat. No. 6,602,190, owned by the assignee of the present invention and incorporated by reference. That is, the preferred surgical retractor clamp  10  is designed for holding components of existing Bookwalter/Codman type systems, such as those components shown in the various patents of John R. Bookwalter et al. including U.S. Pat. Nos. 4,254,763, 4,421,108, 4,424,724, 4,467,791, 5,375,481, 5,520,608, 6,241,659, 6,530,882 and 6,808,493, all incorporated by reference, as originally made and marketed by Codman &amp; Shurtleff, Inc. of Randolph, Mass. Additional examples include those shown in U.S. Pat. Nos. 1,919,120, 1,963,173, 4,434,791, and 5,520,610, all incorporated by reference. In general terms, the Bookwalter/Codman components include retractor blades (not shown) having square/notched retractor blade shafts which extend rearwardly from the surgical arena from the top center of downwardly extending blades. The retractor blades are mounted on an oval or horseshoe shaped frame (not shown) of stock which is rectangular in cross-section, often having crescent-shaped notches around the outside of the frame. 
         [0017]    Being designed to hold and tension existing Bookwalter/Codman blade shafts, the preferred shaft guide subassembly  16  operates as known in the art with a spring loaded pawl  34  mounted on a shaft guide receptacle  36  with a pivot pin  38 . The shaft guide receptacle  36  includes a square or nearly square passageway  40  therethrough roughly matching the cross-section of existing Bookwalter/Codman blade shafts. Under a light spring force, the pawl  34  clicks into the notches of the Bookwalter/Codman blade shaft. The pawl  34  includes a thumb button  42  which can be pressed to remove the pawl  34  from the notches of the Bookwalter/Codman blade shaft, allowing the Bookwalter/Codman blade shaft to be freely slid forward or rearward in the passageway  40 . While the preferred the shaft guide subassembly  16  is designed for clamping Bookwalter/Codman blade shafts, it could be readily modified into any type of clamping or surgical retractor component and still use the ball-and-socket joint of the present invention. 
         [0018]    The ball  18  of the preferred embodiment is generally spherical. With a spherical ball  18 , the ball  18  is received in the socket  14  with degrees of freedom in pitch, in roll and in yaw. The shaft guide subassembly  16  can pivot in any direction with the center of the ball  18  at the center of the socket  14 , until the ball shaft contacts the edge of the socket  14 . 
         [0019]    The socket  14  which receives the ball  18  is provided in the monolithic joint body  12 , which singly provides both a top compression surface  44  and a bottom compression surface  46  around a hinge or fulcrum location  48 . Throughout this specification, the terms “top”, “bottom” and similar directional terms are applied based upon the orientation of the clamp  10  shown in the figures; though most commonly used in this orientation, the clamp  10  can be used in any orientation, including being flipped over so the top compression surface  44  is lower in elevation than the bottom compression surface  46 . Both the top compression surface  44  and the bottom compression surface  46  are defined with spherical profiles that generally match the radius of the ball  18 . In particular, in the loosened state, the top compression surface  44  and the bottom compression surface  46  should define a generally spherical recess which is slightly larger than the outer diameter of the ball  18 . The top compression surface  44  and the bottom compression surface  46  should wrap around the ball  18  at least enough to circumscribe 180° of the ball  18 , so tightening of the joint  10  can involve equal and opposite forces between the top compression surface  44  and the bottom compression surface  46  on opposing faces of the ball  18 . Separate from the torque forces to be withstood by the clamp  10 , the wrap of the top compression surface  44  and bottom compression surface  46  around the ball  18  needs to be sufficient to withstand the pull forces to which the clamp  10  will be subjected. The distal ends of the top compression surface  44  and the bottom compression surface  46  thus act as capture extensions to retain the ball  18  in the socket  14 . Because the clamp  10  is primarily intended to be used in-line with the pull force (i.e., the pull force during retraction use of the clamp  10  is oriented to pull the ball  18  out of the socket  14 ), a significant amount of wrapping by the capture extensions is necessary, such as between about 190° and 270°. In the preferred embodiment, the top and bottom compression surfaces  44 ,  46  provide a wrap angle α of about 220° to prevent the ball  18  from pulling out of the joint body  12 . Other designs, having a wrap angle α less than 190°, could allow the ball  14  to snap in and out of the socket  18  when the joint  10  is loosened. 
         [0020]    With this large amount of wrap angle α and using a monolithic joint body  12 , there needs to be a way of inserting the ball  18  into the socket  14  during assembly of the joint  10 . The preferred method of assembly involves two flats  50  which are located on opposing side surfaces of the ball  18 . With the 220° wrap angle α, the assembly opening  52  is about 94% of the diameter of the ball  18 . Thus, the flats  50  should be slightly less than this 94% of the diameter of the ball  18 . With the flats  50  aligned relative to the wrap angle α, the ball  18  can be inserted into the socket  14 . Once fully inserted into the socket  14 , the ball  18  can be roll rotated to present the flats  50  on the sides of the socket  14 . 
         [0021]    The right and left sides of the socket  14  must also wrap to some extent around the ball  18  so the ball  18  does not translate to the right or left relative to the socket  14 , such as between about 190° and 270° in the side-to-side direction. The amount of the side-to-side wrap depends upon the likely sideways pull out forces of the ball  18  from the socket  14 , which is weighed against the range of motion of the joint  10  which is lost if the socket  14  is designed to wrap further around the ball  18 . In the preferred embodiment, the top and bottom compression surfaces  44 ,  46  each provide a spherical contact. The top compression surface  44  wraps about 70° around the ball  18  in the side-to-side direction, and the bottom compression surface  46  wraps about 66° around the ball  18  in the side-to-side direction. Thus, the wrap from the right edge of the top compression surface  44  around the ball  18  to the right edge of the bottom compression surface  46  is about 248° against pull out to the right, and the wrap from the left edge of the top compression surface  44  around the ball  18  to the left edge of the bottom compression surface  46  is about 248° against pull out to the left. Depending upon the range or motion desired for the joint  10 , either the amount of top side-to-side wrap or the amount of bottom side-to-side wrap could be adjusted, including providing the vast majority of side-to-side wrap on only one of the top compression surface  44  or bottom compression surface  46 . 
         [0022]    In the most preferred embodiment, the top compression surface  44  is provided by a top right compression area  44   r  and a top left compression area  44   l , and the bottom compression surface  46  is provided by a bottom right compression area  46   r  and a bottom left compression area  46   l . A central recess  54  splits the right compression areas  44   r ,  46   r  from the left compression areas  44   l ,  46   l . Each compression area  44   r ,  44   l ,  46   r ,  46   l  has a spherical profile for contact with the ball  18 . By providing four separated compression areas  44   r ,  44   l ,  46   r ,  46   l , tolerances on the ball  18  and tolerances on the joint body  12  are less critical; that is, the ball  18  more easily positions itself centered in the socket  14  without binding or toggling during tightening, even if the shape, size or position of the ball  18  does not perfectly match the shape, size or position of the socket  14 . 
         [0023]    After the ball  18  is inserted into the socket  14 , a ball lock pin  32  is fixed to the ball  18 . The ball lock pin  32  could be screw threaded or otherwise removably fixed to the ball  18 , or it can be permanently fixed to the ball  18 . The preferred ball lock pin  32  is longer than the distance between the flats  50  and extends all the way through the ball  18 , such that the addition of the lock pin  32  increases the effective radius of the ball  18  at the flats  50 , thereafter preventing the ball  18  from pulling through the assembly opening  52 . If desired, the ball lock pin  32  can be made as long as or shorter than the diameter of the ball  18 , such that the lock pin  32  does not impede the motion of the joint  10 . For instance, one embodiment (not shown) uses a lock pin hole which has its diameter the full size of the flats, i.e., the entirety of the flats is provided by the lock pin hole. A wide diameter lock pin fills the lock pin hole with ends sized and contoured to match the spherical profile of the ball  18 . Alternatively and as shown in the drawings, the ball lock pin  32  can be made longer than the diameter of the ball  18 , or otherwise attached to the ball  18  such that the ball lock pin  32  extends beyond the spherical profile and interferes with the socket  14 . With an interfering lock pin, the lock pin  32  prevents full roll rotation of the ball  18  and prevents any alignment of the flats  50  with the assembly opening  52 . With a non-interfering lock pin (not shown), the ball  18  can be fully roll rotated so the flats  50  line up with the assembly opening  52 , in which case the entirety the ball  18  may be able to pull slightly forward with the entirety of a pull-out force bourn by the lock pin. 
         [0024]    The socket  14  has side openings  56  sized to permit insertion of the ball lock pin  32  into the ball lock pin hole  58  while the ball  18  is in the socket  14 . In the preferred embodiment, the open sides  56  of the socket  14  progress back toward the fulcrum  48 . The open sides  56  permit a wider range of side-to-side (yaw) motion of the joint  10  before the interfering lock pin  32  contacts the edge of the socket  14 . As importantly, the fulcrum location and size control the amount and direction of deflection of the top compression surface  44  relative to the bottom compression surface  46  during tightening of the clamp  10 . 
         [0025]    The diameter of the ball  18  is selected based primarily upon the required torque and pull forces that the joint  10  has to withstand during use. The frictional torque imposed on the ball  18  by the top and bottom compression surfaces  44 ,  46  is a function of the compression force placed on the ball  18  by the top and bottom compression surfaces  44 ,  46  multiplied by the ball diameter, so a larger diameter ball  18  results in a joint  10  which can withstand more pitch, yaw and roll forces. On the other hand, a smaller joint is preferred to provide a smaller, less obtrusive profile to the entire clamp  10 , so the joint can be made as small as possible so long as it can provide sufficient clamping force. In the preferred embodiment, the ball  18  has an outer diameter of about ⅝ inches. In the preferred embodiment, the top compression surface  44  and the bottom compression surface  46  in the loosened configuration define an inner diameter slightly larger than the outer diameter of the ball  18 , such as about 0.01 inches greater in diameter. This 0.01 clearance provides essentially friction free rotational movement but defined position of ball  18  during loosened positioning of the joint  10 . The ball shaft  42  is as large as necessary to transmit the expected forces, but otherwise a smaller ball shaft leads to greater angles of motion for the joint  10 . With the ⅝ inch diameter ball  18 , a ¼ inch diameter ball shaft  42  is appropriate. The flats  50  of the preferred embodiment are about 0.54 inches apart, i.e., each flat shaves about 0.04 inches off the curvature of the spherical ball  18 . At this size, each flat is a circle of about 0.3 inches in diameter. The lock pin hole  58  and the ball lock pin  32  in the preferred embodiment are considerably smaller in diameter than the flats  50 , such as a diameter of about ⅛ inch. 
         [0026]    With this size of ball  18 , ball shaft  42  and socket profile, the ball  18 , ball shaft  42  and receptacle  36  can pivot upward and downward through a total pitch angle θ of about 92°. For the desired orientation of a blade shaft through the blade shaft receptacle  36  for desired retraction forces, the pitch angle is split into a maximum declining pitch angle θ d  of about 0° before the ball shaft  42  contacts the bottom compression surface  46  and a maximum inclining pitch angle θ i  of about 92° before the ball shaft  42   38  contacts the top compression surface  44 . The joint  10  can be designed with greater or lesser maximum declining pitch angle θ d  and maximum inclining pitch angle θ i  depending upon the amount of freedom required of the joint  10 . 
         [0027]    The relative size of the ball lock pin  32  as compared to the side openings  56  permits the ball  18 , ball shaft  42  and receptacle  36  to twist about the ball shaft axis  44  through a left twist (yaw) angle δ l  and through a right twist (yaw) angle δ r . The relative size of the ball lock pin  32  as compared to the side openings  56  also permits the ball  18 , ball shaft  42  and receptacle  36  to pivot forward and backward through maximum roll angles γ f  and γ b . With the preferred ⅛ inch diameter interfering ball lock pin  32 , the preferred joint body  12  uses side openings  56  of about 7/16 inches. The deep position of the fulcrum  48  permits maximum roll angles γ f  and γ b  both clockwise and counterclockwise of about 45° while at the upright position shown in  FIG. 1 . The side openings  56  allow maximum yaw angles δ l  and δ r  both to the right and the left of about 30° while at the upright position shown in  FIG. 1 . Modifications to the relative shapes and sizes of the lock pin  32  and/or ball shaft and side openings  56  can permit wide variations to these angles, as desired for the degree of joint flexibility needed in any particular application. 
         [0028]    Though the joint body  12  is formed as a unitary structure, the fulcrum or hinge area  48  provides an area of bending flexibility such that during tightening of the joint  10  the top portion  60  of the joint body  12  slightly rotates relative to the bottom portion  62  of the joint body  12  by bending at the fulcrum  48 . Thus, the joint body  12  in function operates in some ways similarly to the fulcrum clamps of U.S. Pat. Nos. 5,727,899, 7,297,107 and 7,320,666, owned by the assignee of the present invention and incorporated by reference. 
         [0029]    The top compression area  44  and the bottom compression area  46  are each only about half an inch from the fulcrum  48 , while the pivot pin  26  for the handle  24  is about 0.9 inches from the fulcrum  48 . The handle  24  operates a cam  64  positioned between the handle pivot pin  26  and the bearing plate  22 , such that the cam  64  pushes against longer lever arms to the fulcrum  48  than the lever arms of the top and bottom compression areas  44 ,  46 . The curvature of the cam  64  is eccentric relative to the pivot pin  26 ; in the preferred embodiment, the effective radius of the cam  64  changes about 0.06 inches over a throw of about 90°. Due to the relative length of lever arms about the fulcrum  48 , when the ball  18  is not in the socket  14 , the throw of the handle  24  results in the top compression area  44  moving about 0.03 inches closer to the bottom compression area  46 . With the ball  18  in the socket  14 , the first third of the handle throw is taken up in absorbing the 0.01 clearance between the ball  18  and the socket  14 , and the second two thirds of the handle throw is taken up as a very strong compression force on the ball  18 . 
         [0030]    The cam  64  does not bear against a flat surface, but rather bears against the curved surface  66  of the bearing plate  22 . The curvature of the bearing surface  66  almost exactly matches the curvature of the cam  64 , with the preferred embodiment having a 0.251 inch inner cylindrical radius of the bearing plate  22  bearing against a 0.250 inch outer cylindrical radius of the cam  64 . With a curved inner radius of the bearing plate  22 , the bearing force is spread across a considerably larger contact area than if the cam  64  bore against a planar surface. The preferred bearing plate  22  is formed of a lubricious polymer material such as PEEK, to minimize the friction between the bearing plate  22  and the cam  64 . Other than the bearing plate  22 , the other components of the joint  10 , including particularly the cam  64  of the handle  24  and the planar sliding surface  68  of the lower leg  62 , can be formed of surgical grade stainless steel. 
         [0031]    With the inner surface  66  of the bearing plate  22  so closely matching the cam  64 , it must be understood that the eccentricity of the cam  64  causes the bearing plate  22  to translate relative to the joint body  12  during the throw of the handle  24 . The lowest point of the bearing plate curve  66  stays directly under the center of the cam curvature and therefore changes its horizontal offset relative to the handle pivot pin  26  as the handle  24  is thrown. 
         [0032]    The bottom surface of the bearing plate  22  is planar against a planar top surface  68  of the lower leg  62  of the joint body  12 . Thus, the translation of the bearing plate  22  during the handle throw is achieved by sliding of the bearing plate  22  across the planar top surface  68  of the lower leg  62 . The planar surfaces of the bearing plate  22  and the lower leg  62  spread the bearing force against a considerably larger contact area than if a cylindrical or curved cam  64  bore on a planar surface. With the preferred bearing plate  22  formed of a lubricious material, the horizontal sliding of the bearing plate  22  is achieved with minimal friction. 
         [0033]    With the bearing plate  22  sliding across a planar surface  68 , the bearing plate  22  is not affixed or attached to the lower leg  62 . Instead, the bearing plate  22  is captivated by the cam curvature riding in the inner curved surface  66  of the bearing plate  22 . The cam  64  is preferably formed with two separate lobes  70 , and the bearing plate  22  includes an extending portion  72  which projects between the two lobes  70  of the cam  64 . The extending portion  72  prevents the bearing plate  22  from translating sideways relative to the cam  64 , keeping the bearing plate  22  in place directly underneath the cam  64 . Thus, assembly of the handle  24  and bearing plate  22  into the joint body  12  is quickly and easily achieved merely by positioning the cam  64  of the handle  24  in place in the bearing plate  22 , sliding both the handle  24  and bearing plate  22  into position with the pivot pin hole  74  in the handle  24  aligning with the pivot pin hole  76  in the joint body  12 , and affixing the handle pivot pin  26  to hold the handle  24  to the joint body  12 . 
         [0034]    The tightening throw of the handle  24  is preferably relatively short, such as less than about 90°, and more preferably about 45°. To prevent over-tightening or over-loosening of the handle  24  with this short throw, the preferred handle  24  has a loosened stop  78  and a tightened stop  80 . The loosened stop  78  restricts a handle  24  from moving past the loosened position by contacting a loosened abutment section  82  of the upper leg  60 . The tightened stop  80  restricts the handle  24  from moving past the tightened position by contacting a tightened abutment section  84  of the upper leg  60 . Because the loosened stop  78  and the tightened stop  80  both make contact with the upper leg  60  at the end of a throw, a user can tactilely sense when the end of the throw is reached and will not over-torque the clamp  10  beyond the tightened and loosened positions. 
         [0035]    The way in which the joint  10  attaches to a support structure is not central to the present invention, and could be affixed in numerous different ways known in the art. Being designed to work with existing Bookwalter/Codman frames, the preferred jaw  20  operates as taught in U.S. patent application Ser. No. 12/037,820 filed Feb. 26, 2008, incorporated by reference, or otherwise known. In general terms, a lower clamping location  86  attaches about the rectangular cross-sectioned stock of a Bookwalter/Codman frame (not shown). The lower clamping location  86  is provided on the top side by the lower leg  62  of the joint body  12  and on the bottom side by the lower jaw  20 . On the opposite side of the opening  86 , the lower jaw  20  includes a lipped end  88  to clip around the Bookwalter/Codman type frame stock. The lower jaw  20  pivots relative to the joint body  12  about a jaw connection pin  28 . A compression spring  30  is housed between the lower jaw  20  and the joint body  12 . In the preferred embodiment, the compression spring  30  can be compressed to deflect the lipped end  88  beneath the bottom surface of the Bookwalter/Codman type frame stock with only a few pounds of force. 
         [0036]    While the preferred joint  10  does not use the tightening force of the handle  24  to tighten on such Bookwalter/Codman rectangular bar stock, modifications could easily be made such that the force of the cam  64  operates on the lower clamping location  86  as well as tightening on the ball  18 . Other clamp body styles may clamp about rods other than Bookwalter/Codman frame stock and other than Bookwalter/Codman blade shafts while fully utilizing the joint  10  of the present invention. 
         [0037]    Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.