Abstract:
An acetabular reamer has a rotatable drive shaft extending along a first longitudinal central axis. A second housing surrounds at least a portion of the drive shaft, the first housing having a gripping arm. A drive motor in a first housing is coupled to a first end of the rotatable drive shaft for rotating the drive shaft. A reamer head is rotatably coupled to a second end of the rotatable drive shaft, the reamer head rotatable about a second axis extending at an acute angle with respect to the rotatable drive shaft first longitudinal. A releasable connector couples the first and second housing and prevent relative rotation between the first housing and the second housing.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention is directed to implantation of artificial joint components and in particular to acetabular joint components. More particularly, it relates to an instrument for reaming the acetabular socket which allows the connection of and removal of acetabular reamer cutting heads and the application of force to the reamer head mounted on an angled reamer housing. While the instrument is described in connection with an acetabular reamer, it should be noted that the reamer disclosed can be used with other joints. In the case of a reamer, there is typically a drive shaft located within the instrument housing for rotating the reamer cutting head. 
         [0002]    Total hip replacement or arthroplasty operations have been performed to repair the acetabulum and the region surrounding it and to replace the hip components such as the natural femoral head and acetabular socket which have degenerated. 
         [0003]    With regard to the acetabulum, many instruments have been designed to locate either the acetabular cup or provide reamers for repairing the acetabulum to receive such a prosthetic cup. Such instruments are shown in U.S. Pat. Nos. 4,305,394, 4,632,111, 5,037,424, 5,061,270, 5,320,625, and 6,395,005. 
         [0004]    In addition, there have been various designs for the acetabular reamers themselves, including the reamer and holder shown in U.S. Pat. No. 5,658,290. A similar reamer is shown in U.S. Publication No. 2005/0124981 along with a holder for thesame. While these patents show holders for mounting the reamer via a drive shaft to a power source, it has been found that an improved force application system that reduces torque applied to the reamer head and handle from the motor driving the drive shaft for the reamer head is desirable. 
         [0005]    In general, such instruments include a shank or handle portion which has a hollow housing which houses a rotatable drive system. The handle housing leading end includes a quick disconnect for coupling, for example, an acetabular cutting reamer having a hemispherical cutting surface and a coupling system on the acetabular reamer preferably having four rods, bars, or other coupling elements extending from a central hub area preferably located adjacent the equator of the hemispherical cutting surface. Of course the hub could be eliminated with the bars extending continuously across the reamer and the rods or bars could be recessed within the reamer cavity. 
         [0006]    Generally orthopedic reaming, including acetabular reaming, utilizes a series of reamers which increase in size in one or two millimeter steps. These reamers are used in series to enlarge an opening for the receipt of a prosthetic implantation. Incremental reamers are required because excessive heat is generated if the surgeon tries to remove too much tissue or bone with a single reamer. In addition, surgeons may wish to remove the reamer either in the wound or outside thereof to verify the size, bone condition, and implant orientation. Because of this the surgeon must be able to connect and disconnect the reaming tool from the holder preferably in a simple, easy step, and replace a first reamer with a second reamer positively and quickly. 
         [0007]    Currently, acetabular reamers such as shown in U.S. Patent Publication No. 2004/0172036 and U.S. Pat. Nos. 8,282,639 and 8,348,959 show reamer handles having a connector at the end opposite the reaming head which connector is adapted to connect to a drive motor. The drive motor may be an electric motor or a pneumatic motor. It can be seen with the above reamers that one must hold the drive motor and the handle drive system or housing of the acetabular reamer to prevent relative rotation therebetween. This requires the surgeon use both hands to prevent relative rotation between the motor and housing when reaming the acetabulum. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    It has been found to advantageous to provide a drive connection which allows the surgeon to actuate the motor via a trigger-type switch, while allowing the surgeon to have one hand free during the acetabular reaming operation for applying a force along the axis of rotation of the reamer cutting head. This can be accomplished by rigidly fixing the drive motor, for example, housed in a first cylindrical or pistol-type gripping housing to a second housing which houses the drive shaft for the acetabular reamer. The first housing also includes a trigger or switch for actuating an output connector in the motor. The rigid connection preferably is releasable and has inter-engaging structures which prevent the relative rotation between the first housing which houses the drive motor and trigger switch with the second housing including the drive shaft for the reamer head. This is especially advantageous if the reamer housing is an angled reamer housing, in which the axis of the reamer head which is used to prepare the acetabulaum is at an angle with the axis of the drive shaft and the motor output axis. 
         [0009]    It has been found to be especially advantageous to allow the surgeon to use the free hand to apply pressure along the angled axis of the reamer cutting head. This can be accomplished by using a modular handle engagable at different locations along the second housing which houses the drive system extending along a drive axes of the motor output and power transmission shaft located within a straight portion of the acetabular reamer second housing. It has been found especially advantageous to utilize several locations along the reamer housing for a modular attachment of a handle to the shaft to accommodate for various anatomic differences. The several different locations all allow the surgeon to apply pressure via the handle mounted on the second housing parallel to or coaxially with the axis of rotation of the reamer cutting head during preparation of the acetabulum. 
         [0010]    These and other aspects of the invention may be accomplished by an acetabular reamer a first housing including a drive motor and a second housing having a rotatable drive shaft extending along a first longitudinal central axis, the drive shaft having first and second ends. The second housing surrounds at least a portion of the drive shaft, the second housing having a gripping portion. The drive motor having an output shaft located in the first housing operatively coupled to the first end of the rotatable drive shaft for rotating the shaft located within the second housing. A reamer head rotatably is coupled to the second end of the rotatable drive shaft, the reamer head rotatable about a second axis extending in a first direction at an acute angle with respect to the rotatable drive shaft first longitudinal central axis. A first releasable connector operatively couples the first end of the rotatable drive shaft and the drive motor. A second releasable connector prevents relative rotation between the first housing and the second housing. A third releasable connector couples the second portion of the drive shaft and the reamer head. 
         [0011]    The second housing preferably encloses the entire rotatable drive shaft. The drive motor is connected to the drive shaft and is non-rotatably mounted in the first housing. The gripping portion of the second housing enclosing the drive system includes a mounting connector for coupling an arm extending therefrom at the acute angle in a second direction generally opposite the first direction. 
         [0012]    The arm is modular and may be releasably coupled and uncoupled from the second housing. The second housing has at least two and preferably three axially spaced connector locations for receiving the modular arm. A second connector location is spaced axially along the second housing at a greater distance from the reamer head than the first location. The acute angle between the drive system axis and the arm axis is about 45°. 
         [0013]    The second housing having the drive shaft has a first axially extending portion with a first longitudinal axis and a second axially extending portion with a second longitudinal axis, the first and second longitudinal axis intersecting at the acute angle. The first and second axially extending portions of the drive shaft are releasable preferably connected by a universal joint coupling the rotatable drive shaft extending along the first longitudinal axis to the reamer head drive shaft extending along the second longitudinal axis. The drive motor may be either electric or pneumatic. The acute angle is about 45° between the drive shaft first portion connected to the motor and the axis of rotation of the reamer cutting head as well as between the modular arm and the axis of the drive shaft first portion. This allows the surgeon to transmit force in the direction of the reamer head axis of the rotation by applying pressure to the arm. 
         [0014]    Various aspects of the invention are also provided by an acetabular reamer having a first housing containing a drive motor system having an output shaft therein extending out of the first housing along a first axis. A reamer portion has a second housing having a reamer drive shaft therein. The second housing having a first end housing a first end of the reamer drive shaft for connection to the drive motor system. The reamer drive shaft has a second end operatively coupled to an acetabular reamer cutting head. The first and second housings have interlocking portions for coupling the drive motor system to the reamer cutting head drive shaft and for preventing relative rotation between the first and second housings. The reamer drive shaft and the output shaft interlocking portions capable of transferring power from the motor output shaft to the reamer drive shaft. 
         [0015]    The first housing preferably encloses the entire rotatable drive shaft. The drive motor system comprises a drive motor connected to the drive shaft, the drive motor being mounted in the first housing. The first end of the reamer drive shaft extends in a first direction forming an acute angle with respect to the second end of the reamer drive shaft coupled to the acetabular reamer cutting head. 
         [0016]    The first housing may include a gripping portion formed adjacent the first end of the reamer drive shaft and includes a modular gripping handle having an arm extending from the second housing at the acute angle in a second direction opposite the first direction. This allows the surgeon to apply force along the reamer cutting head axis. The gripping arm is modular and may be releasably coupled to the second housing. The second housing has at least two, and preferably three axially spaced locations for receiving the modular arm. The second location is spaced axially along the second housing at a greater distance from the acetabular reamer cutting head than the first location. The acute angle is about 45°. 
         [0017]    The reamer drive shaft has a first axially extending portion with a first longitudinal axis and a second axially extending portion with a second longitudinal axis, the first and second longitudinal axis intersecting at an acute angle of preferably about 45°. A connector including a universal joint may couple the reamer drive shaft first axially extending portion to the second axially extending portion which drives the reamer cutting head at an angle of about 45° to the drive system axis in the first portion of the second housing. The motor output shaft is preferably coaxial with the longitudinal axis in the first axially extending portion of the drive shaft. The drive motor may be either electric or pneumatic. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is an isometric view of a reamer drive portion including an angled drive shaft for powering the cutting head of an acetabular reamer; 
           [0019]      FIG. 1A  shows a releasable connector element for use with the reamer drive portion of  FIG. 1 ; 
           [0020]      FIG. 2  is a top view of acetabular reamer drive housing of  FIG. 1 ; 
           [0021]      FIG. 3  is an elevation view of the drive housing of  FIG. 1 ; 
           [0022]      FIG. 3A  is a partial cross-sectional view of  FIG. 3  along lines  3 A- 3 A showing the connector of  FIG. 1A  on the drive portion of  FIG. 1 ; 
           [0023]      FIG. 4  is an isometric view of a sleeve connector sleeve which may be fixed to an input drive end of the drive portion of  FIGS. 1-3 ; 
           [0024]      FIG. 5  is an elevation view of the sleeve of  FIG. 4 ; 
           [0025]      FIG. 6  is an elevation view of the sleeve of  FIG. 4  rotated 90° with respect to the elevation view shown in  FIG. 5 ; 
           [0026]      FIG. 7  is an isometric view of a drive motor housing including an actuator switch which housing is adapted to connect to the wide end of the sleeve of  FIG. 4 ; 
           [0027]      FIG. 8  is an elevation view of the drive motor housing of  FIG. 8 ; 
           [0028]      FIG. 9  is an elevation view of the drive motor housing of  FIG. 7  rotated 90° from the view of  FIG. 8 ; 
           [0029]      FIG. 10  is an end view of the drive motor housing of  FIG. 9 , when viewed from the right-hand side; 
           [0030]      FIG. 11  is an assembly view of the drive housing of  FIGS. 1-3 , the sleeve of  FIGS. 4-6 , and the drive motor housing of  FIGS. 7-10  including a modular handle arm mounted on the drive shaft housing; 
           [0031]      FIG. 11A  is an isometric view of the modular arm for connection to the connector element of the reamer housing of  FIG. 11 ; 
           [0032]      FIG. 12  is an isometric view of the drive system housing of  FIGS. 1-3  including a t-shaped positioning handle mounted thereon; 
           [0033]      FIG. 13  is an elevation view of the drive system housing of  FIGS. 1-3  including an alternate handle arm mounted thereon for applying a force along the axe of the angled reamer head drive system. 
           [0034]      FIG. 13A  is an isometric view of  FIG. 13 ; 
           [0035]      FIG. 14  shows the drive system housing as shown in  FIG. 13  with the handle arm adapted to apply pressure or force in the direction of the head axis releasably mounted at a location closer to the reamer cutting head drive element; 
           [0036]      FIG. 14A  is an isometric view in a rotated position of the drive system housing, handle and arm of  FIG. 14 ; 
           [0037]      FIG. 15  is an elevation view of the drive system housing, handle and arm, with the handle located in a position further from the reamer cutting head drive element; 
           [0038]      FIG. 15A  is an isometric view of the drive system housing and handle rotated from that shown in  FIG. 15 ; 
           [0039]      FIG. 16  is an elevation view of the drive system housing and handle arm with the handle, arm located in an intermediate position on the drive system housing; and 
           [0040]      FIG. 16A  is an isometric view of the handle, arm and drive system housing shown in  FIG. 16 . 
       
    
    
     DETAILED DESCRIPTION 
       [0041]    Referring to  FIGS. 1-3 , there is shown an instrument generally denoted as  10 , which has a housing  28  which houses a drive system having a drive shaft  12  shown in phantom. Drive shaft  12  includes an input element  14  which may be a solid hex-shaped drive element and an output element  16  which is also preferably a hex-drive element. Input element  14  connects to a typical power tool. These drive elements are well known. Preferably drive shaft  12  includes a preferably straight first portion  18  and a second portion  20  connected by a U-joint  22 . U-joint  22  is required since in the preferred embodiment the axis of rotation of hex-drive input  14  and first portion  18  is along an axis  24  and the output element  16  and portion  20  extends along an axis  26 , which axes are at an angle to one another as shown in  FIG. 3 . The angular offset may be anywhere between 30 and 60° and preferably about 45°. 
         [0042]    Drive shaft  12  is preferably surrounded by a cylindrical metal housing  28  which has a straight first portion  28   a  surrounding the straight portion  18  of drive shaft  12  and a second portion  28   b  surrounding drive shaft portion  20  which shaft portion drives output element  16 . Referring to  FIG. 3 , it can be seen that output element  16  couples to and drives an acetabular reaming head  30  which can be of any standard design. Furthermore output element  16  can be of any design typically used to drive acetabular reamers. 
         [0043]    Again referring to  FIGS. 1-3 , there is shown a multiplicity of handle attachment points in the form of connectors  32 , which connectors are releasably mounted on housing  28   a . Connector  32  is shown in  FIG. 1A  and may be releasably mounted in preferably three recesses  34  spaced along shaft portion  28   a . Connector  32  may include a first pair of spring-loaded ball detents  35  mounted on opposite sides of square extension  38  for holding connector  32  in recesses  34  formed in housing  28  or housing portion  28   a  and may include a second pair of ball detents  36  on a boss  37  to releasably mount a modular handle as described below. The ball detents  35 ,  36  can be located on opposite sides of extension portion  38  to provide sufficient force to maintain the connector in recess  34 . 
         [0044]    Preferably, three recesses  34  are provided on one side of housing portion  28   a  and each recess  34  has a central axis  40  located in a plane containing both longitudinal axis  24  and longitudinal axis  26 . This allows any forces applied to central axis  40  of connector  32  to act along the plane containing axes  24  and  26 . A fourth connector  32   a  is mounted on a side of housing  28   a  opposite, preferably 180°, from the side with the three connectors  32 . Again the central axis  40  of the fourth connector  32   a  lies in the same plane as the first three connectors  32  and is preferably coaxial with the axis of the central connector  32 . 
         [0045]    Referring to  FIG. 3A  there is shown a cross-sectional view through a pair of connectors  32  coaxially mounted on opposite sides housing portion  28   a . Thus as shown in  FIGS. 1-3 , a modular handle can be connected to housing portion  28   a  at three coplanar locations on a first side whose central axes  40  all lie in a plane containing axes  24  and  26  to allow movement of instrument  10  in a direction of axis  26  when reaming an acetabulum. Connector  32   a  on the opposite side can be used to attach a handle adapted to allow the instrument  10  to be manipulated in an alternate direction. 
         [0046]    Referring to  FIGS. 4-6 , there is shown a coupling sleeve  41  which can be either fixedly or modularly attached to an end  42  of housing  28 . End  44  of sleeve  41  thus can be fixedly connected such as by welding or press-fitting onto end  42  of housing  28 . Alternatively there can be a bayonet type coupling (not shown) which would allow easy removal of sleeve  41 . Sleeve  41  includes a pair of slots or openings  46  extending through hollow cylindrical wall  48  which forms an enlarged end of sleeve  41 . Sleeve  41  has an open end  49  adapted to receive a drive motor housing as shown in  FIGS. 7-10 . 
         [0047]    Referring to  FIGS. 7-10  there is shown a housing generally denoted as  50  for housing a drive motor (not shown) which includes a female hex socket output shaft  52  sized to receive the hex input element  14  of the drive shaft  12 . If electric, the drive motor may be driven by a battery housed in housing  50  or may be connected via a power cord. Any actuator for the drive motor may be used such as a switch  54  shown in  FIGS. 7-10  which may either be an on/off switch or a switch allowing variable output speeds. Housing  50  includes a leading end  56  which includes a pair of spring detent elements  58  which are adapted to snap into openings  46  of sleeve  41 . Detents  58  may have beveled leading and trailing surfaces to aid in compression upon insertion or removal of drive system housing  50  into and out of end  49  sleeve  41 . 
         [0048]    Referring to  FIGS. 11 and 11A  there is shown an assembly of drive system  50 , sleeve  41  and drive housing  28 . Included on drive housing  28  is a handle  70  including a connector end  61  as shown in  FIG. 11A . End  61  of handle  70  is connected to mounting portion  32   a  fixed to housing  28 . End  61  may have a pair of through bores  63  for receiving the spring loaded detent pins  36  of mounting portion  32   a . Preferably handle  70  includes a grip portion  72  and a connector arm portion  74  having an axis  76  oriented at right angles to an axis  77  of grip portion  72  which allows the surgeon to apply a force generally parallel to axis  26  of portion  28   b . As shown in  FIG. 11A  end  61  is angled with respect to axis  76  so that connector arm portion  74  can be correctly aligned with axis  40 . As can been seen in  FIG. 11 , an axis  76  of arm portion  74  is generally parallel to axis  26 . Handle  70  can be placed on either of preferably three mounting locations  32  on the side of housing portion  28   a  opposite reamer head drive element  16 . In addition, as shown in  FIG. 12 , a generally T-shaped handle  80  can be attached to a coupling element  32   a  by a shaft  82  having a hollow cylindrical end. Handle  80  has the same coupling end design as shown in  FIG. 11A . Coupling element  32   a  for handle  80  is as shown in  FIGS. 1A and 3A . Grip portion  84  of handle  80  may be of any ergonomic design. 
         [0049]    Referring to  FIG. 13  there is shown an elevation view alternate handle  90  having a gripping portion  92  with an axis  94  coaxial or parallel to with axis  26  of drive element  16 . Handle  90  has a second angled portion  96  along an axis  98  connected to a shaft portion  100  extending along an axis  102 . Axis  94  forms an obtuse angle with axis  98  and with axis  102  with the lengths of handle portions  96  and  100  being selected to place the gripping portion outside the patient when the instrument  10  is being used to ream the acetabulum. 
         [0050]      FIG. 13A  is an isometric view of the elevation view of  FIG. 13  showing handle  90  mounted on the central connector element  32  including portions  96  and  100 .  FIGS. 14 ,  14 A,  15  and  15 A show a handle  70  connected respectively at the connecting element  32  which is closest to drive element  16 , or connected to the connecting element  32  furthest from drive element  16 . The selection of which of the preferably three connecting elements  32  on housing portion  28   a  depends on the anatomy of the patient whose acetabulum is being reamed. Obviously for a larger patient the connecting element  32  furthest from the drive element  16  would be utilized with handle  70 . Furthermore, while handle  70  is shown, handle  90  could also be used to connect to any of the connecting elements  32 . 
         [0051]      FIGS. 16 and 16A  are similar to  FIG. 11 , however, showing handle  70  connected to housing portion  28   a  via the central connecting element  32 . 
         [0052]    While drive system  50  is shown non-rotatably coupled to a housing  28  having a straight section  28 A, the concept of the drive system being non-rotatably coupled to the housing  28  could be applied to a reamer having a curved or angled housing  28 A. While connection or mounting elements  32 ,  32   a  are shown as modular, they could be permanently fixed to housing portion  28   a . Also while four connecting elements  32  are shown inserted into four recesses  34 , only one connecting element  32  or  32   a  is needed since it could be moved to any of the desired four recesses  34 . 
         [0053]    Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.