Abstract:
Described are surgical tools, including tool drivers and implantation instruments, that provide improved visual and positional access to human acetabulum. Some embodiments include a conduit with multiple bends to circumvent soft tissue surrounding the acetabulum. The conduits may employ a number of interlocking, rotational links to transfer torque from a drive end of the tool to a bit end. In one embodiment the bit end supports an attachment actuator that securely engages a conventional acetabular cup for insertion and placement. The attachment actuator can release the cup without moving the body of the tool, which prevents accidental dislodging of a properly placed acetabular cup.

Description:
BACKGROUND  
       [0001]      FIG. 1  (prior art) depicts an acetabular reamer cup  100 , a type of surgical bit used to cut precisely sized hemispherical cavities in the human acetabulum, a cavity at the base of the hipbone into which fits the ball-shaped head of the femur. Acetabular reamer cups are generally mounted on a tool driver via a pair of cross members  105 . The tool driver is in turn mounted in the chuck or collet of a low-speed, high torque portable drill or flexible powered shaft. An embodiment of reamer cup  100  is detailed in U.S. Pat. No. 6,428,543, which is incorporated herein by reference.  
         [0002]      FIG. 2  (prior art) is a cross section of a joint-replacement cup  200 , in this example an acetabular cup, for implanting into a hemispherical cavity formed using reamer cup  100 . Acetabular cup  200  becomes part of an artificial hip joint. A threaded hole  205  firmly secures the concave inner surface  210  of cup  200  against an implantation instrument (not shown) used to insert and position cup  200  into the associated cavity.  
         [0003]     Soft tissue surrounds the acetabulum, and interferes with tool drivers and implantation instruments. This problem is exacerbated in larger patients, who disproportionately require hip-replacement surgery. There is therefore a need for tool drivers and implantation instruments that provide improved access to the acetabulum.  
         [0004]     For detailed discussions of hip replacement, including tool drivers and implantation instruments, see U.S. Pat. Nos. 5,320,625; 6,428,543; and 5,817,096; which are incorporated herein by reference.  
       SUMMARY  
       [0005]     The present invention is directed to surgical tools, including tool drivers and implantation instruments, that provide improved visual and positional access during joint-replacement surgery. Tool drivers and implantation instruments in some embodiments include multiple bends to circumvent soft tissue surrounding the acetabulum. The tool and drive ends may extend along parallel axes so tool operators enjoy a correct sense of reamer or cup placement.  
         [0006]     Tool drivers with one or more bends provide improved access, but the bends complicate the task of transmitting high torque from the drive end to the tool end. Some embodiments address this problem using a drive mechanism made up of a number of interlocking, rotational links.  
         [0007]     A hip-replacement tool in accordance with another embodiment supports an attachment actuator that securely engages a conventional acetabular cup for insertion and placement. The attachment actuator supports an attach state and a release state. In the attach state, threaded jaws in the attachment actuator expand into a hole in the acetabular cup. In the release state, the threaded jaws contract to disengage the cup without rotating with respect to the cup. Users can control the states of the attachment actuator without moving the body of the tool, so tool operators can detach the tool from the implanted cup without accidentally dislodging or misaligning the cup.  
         [0008]     This summary does not limit the invention, which is instead defined by the claims. 
     
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0009]      FIG. 1  (prior art) depicts an acetabular reamer cup  100 , a type of surgical bit used to cut precisely sized hemispherical cavities in the human acetabulum.  
         [0010]      FIG. 2  (prior art) is a cross section of an acetabular cup  200  for implanting into the hemispherical cavities formed using reamer cup  100 .  
         [0011]      FIG. 3  is a side view of a hip-replacement tool  300  in accordance with one embodiment.  
         [0012]      FIG. 4  depicts an embodiment of tool  300  of  FIG. 3  in cross section, with like-numbered elements being the same as those of  FIG. 3 .  
         [0013]      FIG. 5  depicts a portion of conduit  305  in cross section, detailing a number of interlocking rotational links  405 .  
         [0014]      FIG. 6A  depicts link  405  from a perspective facing male end  510 .  
         [0015]      FIG. 6B  depicts a link  405  from a perspective facing female end  515 .  
         [0016]      FIG. 7  depicts a link  700  in accordance with another embodiment.  
         [0017]      FIG. 8  depicts a link  800  in accordance with another embodiment.  
         [0018]      FIG. 9  depicts a hip-replacement tool  900  in accordance with an embodiment used for implanting and positioning an acetabular cup, such as cup  200  of  FIG. 2 .  
         [0019]      FIG. 10  depicts bit end  910  of tool  900  in more detail for ease of illustration.  
         [0020]      FIG. 11  depicts end  910  of tool  900  with cup attachment  920  removed from conduit  905  to better illustrate actuator  1000 .  
         [0021]      FIG. 12  is a cross-section of cup attachment  920  in accordance with one embodiment.  
         [0022]      FIG. 13  depicts an embodiment of tool  900  of  FIG. 9  in cross section.  
     
    
     DETAILED DESCRIPTION  
       [0023]      FIG. 3  is a side view of a surgical tool  300  in accordance with one embodiment. Tool  300 , a hip-replacement tool in this example, includes a conduit  305  extending between a bit end  310  and a drive end  315 . Bit end  310  supports a head  320  that rotates with respect to conduit  305  on a first axis  325 . Drive end  315  includes a handle  322 . A shaft end  330  adapted to mate with a drill collet extends from drive end  315 , and rotates on a second axis  335 . In one embodiment, a flexible shaft extends through conduit  305  from shaft end  330  to head  320 , so rotating shaft end  330  similarly rotates head  320 . Head  320  mates with an acetabular reamer cup similar to cup  100  of  FIG. 1 , and is, in this embodiment, of a type described in U.S. Pat. Nos. 6,540,739 and 6,506,000, both of which are incorporated herein by reference.  
         [0024]     Conduit  305  includes a pair of bends  340  and  345 , so a portion of conduit  305  extends along a third axis  350  at an angle  355  with respect to first rotational axis  325  and an angle  360  with respect to second rotational axis  335 . Angles  355  and  360  are equal in the depicted embodiment, though this need not be the case. The double bend of tool  300  avoids soft tissue for improved visibility and positional accuracy, but still provides a straight-line approach to tool placement. In embodiments in which rotational axes  325  and  335  are parallel, the operator enjoys a correct sense of the position of bit end  310  even when blood and tissue obstruct direct viewing.  
         [0025]     The inclusion of bends  340  and  345  facilitates ease of access, but renders difficult the task of transmitting high torque through conduit  305 . Some embodiments employ a flexible shaft to convey torque from shaft end  330  to head  320 , but such embodiments sometimes suffer gripping and vibration when actuating an acetabular reamer cup against hard or uneven bone surfaces.  
         [0026]      FIG. 4  depicts an embodiment of tool  300  of FIG.  3  in cross section, with like-numbered elements being the same as those of  FIG. 3 . (In general, this document uses a numbering convention in which the leading digit or digits identifies the figure in which the element was introduced.) Rotating head  320  connects to shaft end  330  via a drive shaft  400  and a number of interlocking rotational links  405 . Bushings  410  are disposed between adjacent links  405 . The embodiment of  FIG. 4  has been found to transfer torque more evenly than flexible shafts.  
         [0027]      FIG. 5  depicts a portion of conduit  305  in cross section, detailing a number of interlocking rotational links  405 . Each link  405  is symmetrical about a respective link access  505 , and includes a male end  510  and a female end  515 . Male end  510  has a radius of curvature  520  that allows each link  405  to pivot in a plane parallel to link axes  505  within female end  515  in an adjacent link  405 . The exterior surface of each link  405  includes a radius of curvature  525  that allows the female end of each link  405  to pivot in a plane parallel to link axes  505  and freely against the interior wall  530  of conduit  305 .  
         [0028]     Referring to the interconnection of the two full links of  FIG. 5 , a dashed line  535  extends through the pivotal axis of male end  510  and a dashed line  540  extends through the pivotal axis of female end  515 . The intervening bushing  410  maintains the intersection of the two pivotal axes over a range of angles. In other words, the pivotal axes of the male and female ends remain substantially coaxial when the rotational axes  505  of adjacent links  405  are misaligned. This link arrangement prevents links  405  from binding against one another and against interior wall  530  when transmitting torque around bends in conduit  305 .  
         [0029]      FIG. 6A  depicts link  405  from a perspective facing male end  510 . In this embodiment, link  405  includes six exterior facets  600 , though other shapes might be used. FIG.  6 B depicts a link  405  from a perspective facing female end  515 . Female end  515  includes six interior facets  605  that mate with the exterior facets  600  of an adjacent link  405 .  
         [0030]     In one embodiment, conduit  305  is a  416  stainless-steel pipe with an inside diameter of about 0.410 inches and an outside diameter of about 0.625 inches. Each of bends  340  and  345  is about forty five degrees, with a bend radius of about 2.18 inches. In one embodiment, conduit  305  is formed by drilling out a  416  stainless-steel rod, forming bends  340  and  345 , forcing appropriately sized spheres through the resulting channel to restore the inside diameter within curves  340  and  345  using a hydraulic press, and hardening the resulting conduit. The hardened  416  stainless steel advantageously provides an excellent bearing surface for links  410 . Links  410  are, in one embodiment, machined from  440 -C stainless steel.  
         [0031]      FIG. 7  depicts a link  700  in accordance with another embodiment. Link  700  is similar to links  410  of  FIG. 4 , but includes a lubrication channel  705  in one or more of interior facets  710 . In one embodiment, lubrication channels  705  are formed by first pre-drilling the female end of line  700  to include round hole slightly larger in diameter then the short dimension of the hexagonal hole to be formed in the female end. The corners of the hexagon are then formed either by stamping the hole with a hexagonal dye and removing the resulting chips or using a conventional wobbling broach technique.  
         [0032]      FIG. 8  depicts a link  800  in accordance with another embodiment. Link  800  is similar to link  700  of  FIG. 7 , but includes  8  exterior facets  805  and eight interior facets (not shown).  
         [0033]      FIG. 9  depicts a surgical tool  900  in accordance with an embodiment used for implanting and positioning a cup, such as acetabular cup  200  of  FIG. 2 . Tool  900  includes a conduit  905  extending between a bit end  910  and a handle end  915 . Bit end  910  supports a cup attachment  920  through which protrudes a pair of jaws  925  adapted to extend into and engage with hole  205  of cup  200  ( FIG. 2 ). As detailed below, jaws  925  are parts of an attachment actuator that supports an attach state and a release state: the attach state secures tool  900  to acetabular cup  200  and the release state releases cup  200 . A user controls the states of the attachment actuator by grasping a knurled handle  930  and rotating a knob  935  on drive end  915 . Tool  900  can release cup  200  while holding conduit  905  and handle  930  still, which prevents accidental dislodging of a properly placed cup  200 . As in tool  300  of  FIG. 3 , the inclusion of two bends in tool  900  provides improved visual and surgical access, particularly for relatively large patients.  
         [0034]      FIG. 10  depicts bit end  910  of tool  900  in more detail for ease of illustration. An actuator  1000  extends between jaws  925 . Rotating knob  935  clockwise with respect to handle  930  extends actuator  1000  outward, spreading jaws  925 ; conversely, rotating knob  935  counter-clockwise withdraws actuator  1000 , allowing jaws  925  to close.  
         [0035]     Jaws  925  each include thread portions  1005  sized to engage the female threads of hole  205  in cup  200 . Cup  200  can thus be mounted on cup attachment  920  either rotationally (taking advantage of thread portions  1005 ) or by extending jaws  925  through hole  205  in the release state and turning knob  935  to spread jaws  925  to engage threaded portions  1005 . Tool  900  can then be used to position, implant, and adjust cup  200 .  
         [0036]     Once cup  200  is properly placed, tool  900  can easily release cup  200  without disturbing the position of cup  200 . Rotating knob  935  counter-clockwise withdraws actuator  1000 , allowing jaws  935  to close and release cup  200 . The ability of tool  900  to maintain a secure hold on cup  200  is important, as positioning and implanting cup  200  can require considerable force, possibly even hammer blows on knob  935 . The ability of tool  900  to gently release cup  200  is also important, as cup  200 , once properly positioned, should not be disturbed. Conventional tools that rely upon a rotational connection to threads  205  sometimes cross thread, rendering removal difficult and posing a danger of cup displacement.  
         [0037]      FIG. 11  depicts end  910  of tool  900  with cup attachment  920  removed from conduit  905  to better illustrate actuator  1000 . Cup attachment  920  mates with threads  1100  on conduit  905 , and includes facets  1105  for accepting a suitable wrench.  
         [0038]     Actuator  1000  moves in and out of conduit  905  with rotation of knob  935 . Actuator  1000  mates with interior threads (not shown) within conduit  905 . In one embodiment, the threads on actuator  1000  and the corresponding threads  905  are so-called double threads. Instead of a single helical land, as in most conventional threads, double threads have two interlaced helical lands, rather like the stripes of a barber pole. Double threads advance a mating threaded component twice as far in one turn as a single thread.  
         [0039]      FIG. 12  is a cross-section of cup attachment  920  in accordance with one embodiment. Jaws  925  extend out through the face  1200  of cup attachment  920  and are held in place by a retaining ring  1202 , a washer  1205 , and a spring  1215  (spring  1215  is a Belleville washer in one embodiment). An O-ring  1220  urges jaws  925  against actuator  1000  ( FIG. 10 ) so that jaws  925  close as actuator  1000  is withdrawn. Spring  1215  forces jaws  925  out through face  1200  of cup attachment  920 . A gap  1210  between jaws  925  and washer  1205  prevents jaws  925  from taking the force of hammer blows by allowing jaws  925  to recede into cup attachment  920  until face  1200  engages the interior surface of cup  200 . Face  1200 , and not the more fragile jaws  925  and associated drive mechanism, thus absorbs the impact. A second O ring  1220  prevents blood and debris from entering cup attachment  920  between attachment  920  and conduit  905 . Though not shown here, attachment  920  includes female threads on an inside surface  1250  that mate with threads  1100  on the outside of conduit  905  ( FIG. 11 ).  
         [0040]      FIG. 13  depicts an embodiment of tool  900  of  FIG. 9  in cross section. Various drive mechanisms can be used to force jaws  925  apart or allow jaws  925  to close. In this embodiment, however, a number of links  405  and bushings  410  of the type described above in connection with  FIG. 4  transfer rotational motion of knob  935  to a threaded portion  1300  of actuator  1000 . An O-ring  1305  seals knob  935  against handle  930  while allowing for relative rotation. Knob  935  includes a shoulder  1310  that rests against conduit  905 . The force of blows applied to knob  935  is thus transmitted to cup attachment  920  via conduit  905 , and not via the more sensitive drive mechanism. A set screw  1315  secures handle  930  to conduit  905 , and an O-ring  1320  precludes blood and debris from collecting between handle  930  and conduit  905 .  
         [0041]     While the present invention has been described in connection with specific embodiments, variations of these embodiments will be obvious to those of ordinary skill in the art. For example: 
        a. Hip-replacement tool  900  of  FIG. 9  need not have split threads, as shown, but might also include a more traditional rotating thread actuated using the disclosed link system or some other flexible means for providing torque through the channel;     b. Conduits in accordance with some embodiments are flexible to allow the bends to be adjusted over a range of angles. A series of rotational links might be installed, for example, within flexible conduits of the type available from e.g. Lockwood Products, Inc., under the trademark LOC-LINE.     c. The medical tools described above in the context of hip replacement can be used to advantage in other surgical procedures.     d. Veterinary joint replacement surgery will benefit from the tools described herein.     e. The link systems described herein have broad application outside the medical field.     f. Some embodiments can be modified to include a motor to provide the driving force. 
 
 Therefore, the spirit and scope of the appended claims should not be limited to the foregoing description.