Abstract:
A locking plate intended to be implanted at a bone site and a method for producing and implanting this device. At least one expandable bushing is engaged with a through-hole in the plate. The bushing includes an exterior surface with at least one recess and a passageway including a threaded interior surface. The expandable bushing is initially in a first configuration that permits poly-axial rotation of the bushing within the through-hole. An elongated anchoring member is provided with a distal portion and a proximal portion including a head portion with threads complementary to the threads on the interior surface of the expandable bushing. The proximal portion expands the bushing to form a friction lock between the bushing and the plate in a selected polyaxial position in a second configuration. At least one discrete blocking member is fixedly engaged with the body portion of the plate and extends into the through-hole to engage with the recess on the expandable bushing. The blocking member inhibiting rotation of the expandable bushing relative to the through-hole.

Description:
[0001]     This application claims priority to French application no. 0610141, titled DISPOSITIF PROTHETIQUE OU D&#39;OSTEOSYNTHESE A OLIVE FENDUE, filed on Nov. 20, 2006.  
       FIELD OF THE INVENTION  
       [0002]     The present invention is directed to an improved bone plate with an expandable bushing, in which the rotation of the bushing about its main axis is blocked before expansion, and to a method of making and implanting such a device.  
       BACKGROUND OF THE INVENTION  
       [0003]     Bone plates allow fractures of the anatomical neck of the humerus or of the end of the humerus situated nearer the elbow and also fractures of the upper end of the tibia, or even other epiphyseal lesions of long bones to be minimised.  
         [0004]     WO-A-2003/007832 discloses a plate that is fixed to the bone by screws which each comprise, on the one hand, a threaded rod for anchoring to the bone, inserted through a through-hole in the plate, and, on the other hand, a threaded head for immobilising the screw relative to the plate, screwed into the wall of the hole, which is threaded in a complementary manner. In practice, the anchoring direction of the screws is not always aligned with the axis of revolution of the threaded wall of the hole in the plate and, as a result, it is necessary to interpose, between the head of the screw and the wall of the hole, a bushing for accommodating the misalignment between the axis of the screw and the axis of the hole. The exterior of the bushing is shaped in such a way that, as long as the head of the screw is not screwed into the bushing, the bushing is movable against a smooth wall of the hole like a ball joint, whereas, when the head of the screw is progressively screwed into the bushing, the bushing deforms so as to push firmly against the wall of the hole until it rigidly connects the screw and the plate by wedging. In practice, in order to be deformable, the bushing is split completely apart in such a way that the edges of the corresponding slot are spaced from one another when the head of the screw is screwed. An example of this is given in DE-U-200 22 673.  
         [0005]     In use, such bushings are difficult to handle: when the head is screwed into the bushing, it is difficult for the internal thread of the bushing to engage with the thread of the screw head since the bushing tends to turn round on itself in the hole in the plate due to the fact that the connection between the bushing and the wall of the hole is still movable. A surgeon thus has difficulties in effectively screwing the head of the screw into the bushing and this complicates surgical procedures and increases intervention time.  
         [0006]     To overcome this drawback, it is proposed that, when the head of the screw is not yet engaged in the bushing, the rotation of the bushing about the axis of its orifice be blocked relative to the hole in the prosthetic or osteosynthesis body, using an enlargement projecting from the outer face of the bushing which is received in a hollow groove in the wall of the hole. This enlargement abuts into one or the other of the ends of the groove when the bushing tends to rotate about the axis of its orifice, which rotationally immobilises the bushing about the axis, without preventing it from tilting within the hole in order to accommodate any possible misalignment between the axis of the hole and the anchoring direction of the screw selected by the surgeon. An example of this type of expandable bushing with a local enlargement on its outer face is shown in FIG. 15 to 20 of document US-A-2005/0154392.  
         [0007]     In practice, forming a rotation-blocking enlargement of this type causes difficulties in production since the presence of the enlargement must not adversely affect the geometric features of the rest of the outer face of the bushing, for example its spherical shape, without which the bushing tends to become wedged in the hole in undesirable positions. In order to obtain an acceptable level of reliability, production costs are therefore high.  
         [0008]     Another solution which blocks the bushing in rotation is proposed by US-A-2005/085913, which discusses, without illustrating, a member or a projecting enlargement located inside the hole for receiving the bushing and provided for extending into the slot of the bushing. US-A-2005/085913, however, does not provide any corresponding details regarding production thereof and thus does not provide an actual practical and cost-effective solution.  
       BRIEF SUMMARY OF THE INVENTION  
       [0009]     The present invention is directed to an improved bone plate with an expandable bushing, in which the rotation of the bushing about its main axis is blocked before expansion, which is simple to produce, effective, and inexpensive.  
         [0010]     The locking plate includes a plate with a body portion and at least one through-hole. At least one expandable bushing is engaged with the body portion. The bushing includes an exterior surface with at least one recess and a passageway including a threaded interior surface. The expandable bushing is initially in a first configuration that permits poly-axial rotation of the bushing within the through-hole. An elongated anchoring member is provided with a distal portion and a proximal portion including a head portion with threads complementary to the threads on the interior surface of the expandable bushing. The proximal portion expands the bushing to form a friction lock between the bushing and the plate in a selected polyaxial position in a second configuration. At least one discrete blocking member is fixedly engaged with the body portion of the plate and extends into the through-hole to engage with the recess on the expandable bushing. The blocking member inhibiting rotation of the expandable bushing relative to the through-hole.  
         [0011]     In one embodiment, the recess is a slot extending completely through a wall of the expandable bushing. Radial expansion of the expandable bushing from the first configuration to the second configuration is typically plastic and/or elastic deformation of the expandable bushing. The exterior surface of the expandable bushing and walls of the through-hole are preferably substantially spherical in a complementary manner, except where the blocking member engages with the recess.  
         [0012]     The distal portion of the anchoring member can be smooth, or include threads adapted to engage with the bone. The threads on the head portion of the anchoring member and the threads on the interior surface of the bushing can be tapered or cylindrical. In one embodiment, the head portion includes an unthreaded tapered surface that expands the expandable bushing to the second configuration.  
         [0013]     The blocking member is preferably a discrete component fixedly engaged with a recess in the body portion of the plate, such as for example a cylinder that engages with a hole in the body portion of the plate. A single blocking member can extend into a plurality of through-holes to simultaneously engage with the recesses of a plurality of expandable bushings. In some embodiments, the recess in the body portion of the plate includes a central axis that is parallel to, or at an angle with respect to, a central axis of the through-hole.  
         [0014]     The present invention is also directed to a method of engaging a locking plate with a bone. The method includes positioning the locking plate against a bone. An expandable bushing is located in at least one through-hole in a body portion of the locking plate. An elongated anchoring member is inserted through a passageway in the expandable bushing. The bushing is poly-axially rotated within the through-hole to a desired angle. The distal portion of the anchoring member is inserted into the bone. At least one blocking member is engaged with the body portion of the plate so that the blocking member extends into the through-hole to engage with a recess on the expandable bushing and block rotation of the expandable bushing relative to the through-hole. Threads on a head portion of the anchoring member are engaged with a threaded interior surface of the passageway on the bushing to expand the bushing from a first configuration that permits poly-axial rotation of the bushing within the through-hole to a second configuration that comprises a friction lock between the bushing and the plate.  
         [0015]     The bushing can be expanded plastically or elastically. In one embodiment, threads on a distal portion of the anchoring member engage with the bone. In another embodiment, tapered threads on one or more of the head portion and the threads on the interior surface of the bushing radially expand the bushing from the first configuration to the second configuration. In another embodiment, a tapered surface on a proximal portion of the head portion radially expands the bushing from the first configuration to the second configuration.  
         [0016]     The blocking member is preferably a discrete component fixedly engaged with a recess in the body portion of the plate. For example, a cylindrical blocking member is inserted into a cylindrical hole on the body portion of the bone plate. A single blocking member can optionally extend into a plurality of through-holes to simultaneously engage with the recesses of a plurality of expandable bushings. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0017]     A better understanding of the invention will be facilitated by reading the following description, given by way of example only with reference to the drawings, in which:  
         [0018]      FIG. 1  is a perspective view of the upper end of a humerus including a locking bone in accordance with an embodiment of the present invention.  
         [0019]      FIG. 2  is a partial cross-section along the plane II in  FIG. 1  showing in an exploded manner the humeral plate as well as the blocking members, a bushing, and an anchoring member of the device.  
         [0020]      FIG. 3  is a view directed along the arrow III in  FIG. 2  showing one of the blocking members, the bushing and a portion of the plate of the device.  
         [0021]      FIG. 4  is a perspective view of an alternate locking plate in accordance with an embodiment of the present invention.  
         [0022]      FIG. 5  is a partial cross-section along the plane V of  FIG. 4  showing in an exploded manner the components of  FIG. 4  as well as a bushing and an anchoring member of the device.  
         [0023]      FIG. 6  is cross-sectional view of an alternate bushing and anchoring member in according with an embodiment of the present invention.  
         [0024]      FIG. 7  is a top view of an alternate bushing and a portion of the plate of the device in accordance with an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0025]     In  FIG. 1 , the upper end portion of a humerus is schematically shown, the diaphysis and the epiphysis of which are referenced with the numerals  2  and  3  respectively. For the sake of convenience the following description will refer to the humerus in its anatomical position for a patient standing erect, in such a way that the terms “upper” and “high” designate an upwards direction in FIGS.  1  to  3 , while the terms “lower” and “low” designate the opposite direction.  
         [0026]     On the humerus  1  is fitted a humeral plate  10  comprising a main elongate body  11  extending in the longitudinal direction of the humerus, both at the diaphysis  2  thereof and at the epiphysis  3  thereof. The body  11  thus includes a diaphyseal portion  12  and an epiphyseal portion  13  located at the diaphysis and the epiphysis respectively of the humerus.  
         [0027]     A plurality of holes  14  pass through the thickness of the portion  12  and open onto the humeral diaphysis  2 , including a threaded hole  14   1  and a hole  14   2  with an oblong cross-section. The holes  14  are not described in further detail, it being noted that their number and/or their geometry do not limit the invention in any way.  
         [0028]     In the illustrated embodiment, four holes  15  pass through the thickness of the epiphyseal portion  13  and open onto the humeral epiphysis  3  and are identical to one another. The two lowest holes  15 , seen in cross-section in  FIG. 2 , are disposed one behind the other in the longitudinal direction of the body  11 , while the two remaining holes are disposed symmetrically on both sides of the centre plane of the body, which corresponds to the plane of cross-section II.  
         [0029]     The exemplary humeral plate  10  also comprises two lateral projections  16  which extend on both sides of the epiphyseal portion  13  each in opposite directions, transverse to the longitudinal direction of the body. In cross-section, namely in a cross-sectional plane substantially perpendicular to the plane II, the arms  16  and the portion  13  are generally C-shaped and are sized to embrace the epiphysis  3  in order to improve the stability of the plate  10  on the humerus  1 .  
         [0030]     In order to fix the plate  10  to the humerus  1 , a plurality of structures for anchoring to the bone may be used by each being inserted into the holes  14  of the diaphyseal portion  12 , into the holes  16   a  provided at the free end of each lateral projection  16 , and into the holes  15  of the epiphyseal portion  13 . Only the anchoring structure associated with the holes  15  will be described in detail in the following, it being understood that the configuration of the plate  10  and the number and location of the holes  14 ,  15 ,  16   a  do not limit the invention.  
         [0031]     As shown in more detail in  FIGS. 2 and 3 , each through-hole  15  comprises, in sequence, on the one hand, on the side of the body  11  to be turned towards the humerus  1 , a cylindrical portion  17  with a circular base and having a longitudinal axis X-X and, on the other hand, on the opposite side, a spherical portion  18  with its centre at a point O on the axis X-X. The spherical portion  18  substantially corresponds, along axis X-X, to the median zone of the geometrical sphere to which the portion  18  belongs, in such a way that the point O is located inside portion  18 .  
         [0032]     The axes X-X of each hole  15  are not necessarily parallel to one another, as shown by the two holes seen in cross-section in  FIG. 2 . Each hole  15  is adapted to receive both a generally tubular bushing  20  with a longitudinal axis Y-Y, and an anchoring member  30  for anchoring to the bone with a longitudinal axis Z-Z.  
         [0033]     The portion of the bushing  20  closes to the humerus  1  comprises an annular portion  21  with a circular base with an axis Y-Y and, at the opposite side, a ring-shaped portion  22  with a substantially spherical outer face  22 A with its centre at a point C on the axis Y-Y. The annular portion  21  and the substantially spherical outer face  22 A preferably do not contain any protrusions or other structures. Consequently, the bushing  20  can be manufactured using conventional machining operations.  
         [0034]     The outer diameter of the annular portion  21  is strictly less than the inner diameter of the portion  17  of the hole  15 , whereas the outer diameter of the portion  22  is substantially equal to the inner diameter of the portion  18  of the hole. In this way, when the bushing  20  is received in the hole  15 , a not-insignificant radial clearance j is present between the portions  21  and  17 , whereas the spherical face  22 A of the portion  22  and the spherical wall  18 A of the portion  18  are juxtaposed in a complementary manner, the points  0  and C thus substantially coinciding.  
         [0035]     At its interior, the bushing  20  delimits a through-orifice  24  centred on the axis Y-Y and threaded over a portion of its length along the axis. In the illustrated embodiment, the bushing includes slot  25  on a portion of its periphery, which extends over the entire bushing in the direction of the axis Y-Y and which passes completely through the tubular wall of the bushing in such a way that the slot radially connects the outer face of the bushing and the inner orifice  24  thereof. The slot  25  thus imparts a shape in the general form of a C to the bushing when viewed in cross-section, as well as when viewed along the axis Y-Y, as shown in  FIG. 3 .  
         [0036]     Along its length, the anchoring member  30  comprises, on the one hand, a distal threaded rod  31  to be screwed into the thickness of the bone of the humeral epiphysis  3  and, on the other hand, a proximal threaded head  32  to be screwed into the inner orifice  24  of the bushing  20 . The screw head is adapted to allow the anchoring member  30  to be rotationally driven about its axis Z-Z, both to screw the rod  31  into the humeral bone and to screw its head  32  into the orifice  24  of the bushing. For this purpose, the head  32  has, for example, on the proximal side thereof, a cavity (not shown in the figures) with a hexagonal or similar profile, which allows the anchoring member  30  to be rotationally-driven by using an appropriate tool.  
         [0037]     In one embodiment, the outer threaded face  32 A of the head  32  is in the form of truncated-cone-shaped casing with an axis Z-Z converging towards the axis as it approaches the rod  31 . The wall  24 A of the threaded orifice  24  of the bushing  20  is also optionally in the form of truncated-cone-shaped casing with an axis Y-Y, converging towards the axis as it approaches the distal side of the bushing. The truncated-cone shapes of the outer face  32 A and the wall  24 A are substantially complementary, the angles at the apexes α 32  and α 24  of these two truncated-cone shapes being substantially equal. In another embodiment, only one of the threaded face  32 A or the wall  24 A comprise a truncated cone and the other comprises a cylindrical configuration without a taper.  
         [0038]     In addition, the outer diameter of the distal end of the head  32  is substantially equal to the inner diameter of the proximal end of the orifice  24  in such a way that, as the head  32  is screwed into the bushing  20 , the inner diameter of the orifice  24  increases until the inner diameter of the proximal end of the orifice is substantially equal to the outer diameter of the proximal end of the head  32  when the head is completely screwed into the bushing. Increasing the inner diameter of the orifice  24  is enabled by the fact that the bushing  20  is split. When the head  32  is screwed into the orifice  24 , the edges of the slot  25  move away from one another, and thus allow the bushing to pass from a first configuration, shown in dashed lines in  FIG. 3  and corresponding to a rest state of the bushing  20  in the hole  15 , to a second configuration in which it is radially deformed towards the exterior in relation to the axis Y-Y, shown in a solid line in  FIG. 3 . The bushing  20  may be constructed of a material that permits plastic or elastic deformation.  
         [0039]      FIG. 7  illustrates an alternate bushing  120  located in a hole  15  of the epiphyseal portion  13 . Rather than slot  25  illustrated in  FIG. 3 , the bushing  120  includes a recess  122  that engages with blocking member  40 . In the illustrated embodiment, slit  124  is provided to permit the bushing  120  to expand radially when engaged with an anchoring member. In an alternate embodiment, the slit  124  is located adjacent to the recess  122 . In another alternate embodiment, the bushing  120  is constructed from a deformable or expandable material, such as for example, a biocompatible polymer that plastically deforms when engaged with an anchor member  30 , without the need for the slit  124  or the slot  25 .  
         [0040]     In order to block the bushing  20  from rotating about the axis Y-Y in the hole  15  when it is in its first configuration, a member  40  is inserted fixedly into the body  11  of the plate  10 . In the illustrated embodiment, the member is in the form of a cylinder with a circular base and having a central longitudinal axis U-U, formed in particular from a metal similar to that of the body of the plate  11 . The blocking member  40  is joined to the plate  10  by being received and immobilised, in particular by welding, in a complementary recess  19  formed, for example by machining, in the body of the plate  11 , at a peripheral portion of the hole  15 . In practice, the recess  19  is smaller than the hole  15  in that the diameter thereof is smaller than that of the hole. The blocking member  40  may be other shapes, such as for example with a narrowing configuration that tapers in the direction of the centre of the hole  15  that they occupy in part, so as not to obstruct the partial closure of the slot during introduction of the bushing into the hole, while being adjusted closest to the edge of this slot once the bushing is received in this hole.  
         [0041]     The central longitudinal axis of the recess  19  may be parallel to or, as for example shown in the figures, slightly inclined so as to converge towards the humerus, preferably at an angle of about 15° or less with respect to the axis X-X of the hole, opens radially into the hole  15 . In other words, the hole  15  and the recess  19  are not respectively closed over all of their periphery, but respective portions of the peripheries are provided so as to communicate with one another, in particular in the plane of  FIG. 2 . The recess  19  is thus in the form of a portion of a cylinder. In this way, when the member  40  is received in the recess  19 , as illustrated for the hole  15  shown in the lower portion of  FIG. 2 , and as illustrated in  FIG. 3 , the member occupies all of the internal volume of the recess, while a peripheral portion  40 A of the member occupies a portion of the interior of the corresponding hole  15 . The portion  40 A is provided to extend, in a direction peripheral to the axis Y-Y, between the edges of the slot  25  when the bushing is received in the hole  15 , as shown in  FIG. 3 .  
         [0042]     Producing and implanting the plate  10 , the bushing  20 , the anchoring member  30  and the member  40 , will now be discussed in more detail.  
         [0043]     It is proposed that the four members  40 , each associated with the four holes  15 , are initially joined to the plate  10  by welding each of the members in the corresponding recess  19  previously formed in the body of the plate  11 , as shown by the arrow F 1  in  FIG. 2 . The bushings  20  are then received in their associated hole  15 , each of the slots  25  thereof being positioned in an angled manner such that the peripheral portion  40 A of each member  40  is received between the edges of the slot, as shown by arrow F 2 .  
         [0044]     In practice, fitting each bushing  20  requires that the externally spherical portion  22  is gently radially compressed towards the interior by bringing the edges of its slot  25  slightly closer together until the maximum outer diameter of the bushing is less than the proximal diameter of the hole  15 . The whole of the bushing may then be axially inserted into the hole, the portion of the member  40 A being received in the slot  25 . If necessary, the slot  25  may be partially closed again until the edges thereof contact the lateral wall of the portion of the member  40 A. The cylindrical shape of the lateral wall has been found to be practical as it does not obstruct the partial closure of the slot  25  and it can even guide the insertion of the bushing into the hole by sliding contact of the edges of the slot thereof along the lateral wall.  
         [0045]     The surgeon then fits the plate  10  along the humerus  1 , the portion  13  of the body  11  and the lateral projections  16  embracing the epiphysis  3  thereof, as shown in  FIG. 1 .  
         [0046]     The anchoring member  30  is thus axially inserted into each hole  15  by rotationally driving the anchoring member about its axis Z-Z in such a way that the rod  31  thereof penetrates into the bone matter of the epiphysis  3  in order to be securely anchored therein. The anchoring member  30  is inserted and screwed in while the bushing  20  is received in the hole  15 , the anchoring member  30  passing through the orifice  24  thereof. In this configuration, the spherical face  22 A of the bushing slides freely against the spherical wall  18 A of the hole  15  in order to adjust for misalignment between the axes X-X and Z-Z if the surgeon inserts the anchoring member  30  in an inclined longitudinal direction relative to the axis of the hole, in particular as a function of the state of the bone matter at his disposal. The movable connection between the bushing and the wall of the hole  15  is similar to that of a ball joint with, however, its freedom of movement restricted by the presence of the member  40 .  
         [0047]     The member  40 A prevents the bushing  20  from turning on itself so that the passageway  24  is inaccessible. In other words, in order to accommodate any potential misalignment of the axes X-X and Z-Z, the bushing  20  is able to pivot inside the hole  15  about an axis which is substantially perpendicular to the axis X-X and passing through the point O, by sliding contact of the face  22 A against the wall  18 A, as shown by the arrow  26  in  FIG. 2 . The pivot range is limited by the annular portion  21  being brought into abutment against the wall  17 A of the portion of the hole  17 . The maximum pivot range of the bushing is directly related to the aforementioned clearance j and is in the range of about 20°.  
         [0048]     When the head  32  is axially directly adjacent to the bushing  20  and when the surgeon continues to rotationally drive the anchoring member  30  about its axis Z-Z, the thread of the outer face  32 A of the head  32  engages simply and easily in the thread of the orifice  24 , causing the bushing to pass from its first to its second configuration. Initially engaging the thread of the anchoring member head in the internal thread of the bushing is facilitated by the fact that the rotation of the bushing  20  about its axis Y-Y is immobilised by the member  40 .  
         [0049]     As the head  32  is screwed into the threaded orifice  24 , the outer face  22 A of the bushing  20  is pressed against the wall  18 A of the hole  15  until the bushing is wedged inside the hole, thus rigidly connecting the bushing, and therefore the anchoring member  30 , to the plate  10 .  
         [0050]      FIGS. 4 and 5  show a variation of the osteosynthesis device in FIGS.  1  to  3  is shown, the components common to the two embodiments have the same reference numerals. The variant in  FIGS. 4 and 5  is distinguished from the device in FIGS.  1  to  3  basically through the shape of at least one of the members  40 ′ for rotationally blocking the bushings  20  in the holes  15 . More precisely, rather than associating one of the cylindrical members  40  of the device in FIGS.  1  to  3  with each hole  15 , the same member  40 ′ allows rotational locking of two bushings  20  received in two adjacent holes  15 , for example in the two lowest holes  15  of the humeral plate  10 , as shown in  FIGS. 4 and 5 . Of course, a member of the same type as the member  40 ′ described hereinafter may be used, in a non-illustrated variant, to block the bushings  20  received in the two holes  15  located in the upper portion of the body of the plate  11  on both sides of the centre plane of the body.  
         [0051]     As shown in  FIGS. 4 and 5 , the member  40 ′ comprises a generally parallelepiped proximal portion  41 ′ and a generally cylindrical distal portion  42 ′ with a circular base, centred on an axis U′-U′ perpendicular to the longitudinal dimension of the portion  41 ′. In the layout of  FIG. 5 , the member  40 ′ is thus generally T-shaped.  
         [0052]     In order to receive and immobilise the member  40 ′, the plate body  11  delimits a recess  19 ′ which includes, on the proximal side of the plate body, an elongate portion  19 ′ 1  which extends lengthwise between the two holes  15  in the plane passing through the axes X-X of the holes, generally in a direction radial to the holes. The longitudinal ends of the portion of recess  19 ′ 1  open respectively into the two holes  15 .  
         [0053]     On the distal side of the plate body  11 , the recess  19 ′ includes a cylindrical portion  19 ′ 2  opening onto the portion of the recess  19 ′ 1  in such a way that the portions of the recess  19 ′ 1  and  19 ′ 2  are respectively complementary to the proximal portion  41 ′ and the distal portion  42 ′ of the member  40 ′.  
         [0054]     In order to insert the member  40 ′ into the recess  19 ′, the distal portion  42  is coaxially inserted into the portion of the recess  19 ′ 2  as indicated by the arrow F′ 1 , while the proximal portion  41 ′ is inserted in an adjusted manner into the portion of the recess  19 ′ 2 , thus preventing the member  40 ′ from turning about the axis U′-U′. The longitudinal ends  41 ′A of the proximal portion  41 ′ thus occupy a portion of each of the holes  15  in the same way as the peripheral portion  40 A of the member  40  occupies a portion of the hole  15  in the embodiment in FIGS.  1  to  3 . Advantageously the longitudinal ends  41 ′A are shaped as cylinder portions, the respective longitudinal axes of which are shown in the layout in  FIG. 5  so as to facilitate the fitting of the bushings  20  into the holes  15 .  
         [0055]     The manufacture and use of the variant in  FIGS. 4 and 5  are similar to those of the device envisaged in FIGS.  1  to  3 . Once the member  40 ′ has been placed and interlocked in the recess  19 ′, the bushings  20  are each introduced into one of the holes  15 , with the ends  41 ′A of the member  40 ′ received between the edges of the slot  25  of each bushing, as indicated by the arrow F 2 . The screws  30  are then introduced axially into each hole  15 , as described above with regard to the embodiment of FIGS.  1  to  3 .  
         [0056]      FIG. 6  illustrates an alternate anchoring structure  100  in the form of a pin or nail on which the distal portion  102  is not threaded. The surgeon will typically drill a hole in the bone to receive the unthreaded distal portion  102  of the anchoring structure  100 . Proximal portion  104  comprises a head  106  with threads  108  complementary to threads  110  on the bushing  112 . In the illustrated embodiment, the threads  108  and  110  are not tapered. Rather, sloped surface  114  on the head  106  engages with surface  116  on the bushing  112 . Once the surfaces  114  and  116  are engaged, further rotation of the anchoring member causes the bushing to expand radially relative to the axis Z-Z′.  
         [0057]     The present expandable bushing and anti-rotation member can be used with a variety of other orthopaedic implants, such as for example a base plate for a glenoid implant. Examples of such base plates are illustrated in U.S. Pat. Nos. 6,969,406, 6,761,746, 5,702,447 and U.S. Patent Publication No. 2005/0278032, which are hereby incorporated by reference.  
         [0058]     Patents and patent applications disclosed herein, including those cited in the Background of the Invention, are hereby incorporated by reference. Other embodiments of the invention are possible. Although the description above contains many specificities, these should not be construed as limiting the scope of the invention, but as merely providing illustrations of some of the presently preferred embodiments of this invention. Thus the scope of this invention should be determined by the appended claims and their legal equivalents. Therefore, it will be appreciated that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” All structural, chemical, and functional equivalents to the elements of the above-described preferred embodiment that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims.