Abstract:
Bone anchor implantation devices and methods for their use are disclosed. The bone anchor implantation devices have an ergonometric and/or rotatable handle. The bone anchor implantation devices and methods find particular application for implanting a bone anchor for maintaining or improving urinary continence by suspending or stabilizing the bladder neck.

Description:
CROSS-REFERENCE TO OTHER PATENT APPLICATIONS  
       [0001]     This application is a continuation of U.S. patent application Ser. No. 10/147,533 filed on May 16, 2002, the entire content of which is hereby incorporated by reference herein in its entirety. 
     
    
     TECHNICAL FIELD  
       [0002]     The invention relates to devices for manually implanting a bone anchor into bone.  
       BACKGROUND OF THE INVENTION  
       [0003]     Female Stress Urinary Incontinence (FSUI) is a disorder that can interfere with daily activity and impair the quality of life of women. In approximately 8% of the women suffering from FSUI, incontinence is caused by intrinsic sphincter deficiency (ISD), a condition in which the valves of the urinary sphincter do not properly coapt. In approximately another 8% of FSUI sufferers, incontinence is caused by hypermobility, a condition in which the muscles around the bladder relax, causing the bladder neck and proximal urethra to rotate and descend in response to increases in intraabdominal pressure. Hypermobility may be the result of pregnancy or other conditions which weaken the muscles. Urinary incontinence may also be caused by a combination of ISD and hypermobility. Other causes of urinary incontinence include birth defects, disease, injury, aging, and urinary tract infection.  
         [0004]     Numerous approaches for treating urinary incontinence are available. For example, several procedures for stabilizing and/or slightly compressing the bladder neck or urethra to prevent the leakage of urine have been developed. The stabilizing or compressive force may be applied directly by sutures passing through the soft tissue surrounding the urethra or, alternatively, may be applied by means of a sling suspended by sutures. In some procedures bone anchors are inserted into the pubic bone or symphysis pubis in order to anchor the sutures to the bone. The suture or sling is anchored to the bone by one or more bone anchors and the support provided improves the incontinence condition.  
         [0005]     The instruments used to insert bone anchors are designed to be inserted transvaginally and to position the bone anchor so that a retrograde or pulling force is applied for insertion of the anchor into the bone. However, the optimal configuration or position of the handle of such an instrument for insertion of the device into the vagina is not necessarily the optimal handle position for providing a retrograde force for implanting the bone anchors into the bone. For example, the fixed handle position of conventional bone anchor devices is particularly awkward when treating obese patients  
       SUMMARY OF THE INVENTION  
       [0006]     The present invention relates to devices and methods for inserting anchors, such as bone anchors, into a bone or tissue.  
         [0007]     In one aspect, a device is provided for manually implanting a bone anchor into a bone; the device includes a handle, a shaft, and a bone anchor-mount. The handle has a proximal end and a distal end. The shaft has a first end and a second end, and may be straight with a bend at its second end, or may instead be hook-shaped. The first end of the shaft is connected to the distal end of the handle. The bone anchor-mount is connected to the second end of the shaft and oriented toward the handle so that a bone anchor received within the mount may be implanted into a bone by applying a retrograde force using the handle. The handle may have at least one finger indentation at its distal end, thereby providing an ergonomic grip. For example, the handle may contain two, three, four or more finger indentations at its distal end. The handle may also be shaped to fit into a user&#39;s palm.  
         [0008]     In another aspect, the invention provides a bone anchor implantation device with a handle that can be rotated relative to the longitudinal axis of the shaft during a bone anchor implantation procedure, to facilitate the insertion of the device into a body cavity and/or implantation of a bone anchor. For example, the device can be inserted into the vagina of a patient with the handle in one position, following which the handle can be rotated about the longitudinal axis of the device&#39;s shaft and locked into a second position, wherein the second position facilitates the application of a retrograde force or pulling action required for anchoring the bone anchor into a bone.  
         [0009]     In a particular embodiment, the handle may be both rotatable and ergonomic.  
         [0010]     In one version of the device, the handle may be rotatable between two angular positions and may contain a stop assembly for locking the handle in a first or a second angular position. For example, a representative stop assembly has an outer cylinder, an inner cylinder and a spring. The outer cylinder is fixed to the handle and aligned with the shaft, and includes a circumferential slit having a pair of diametrically opposed detents, for example. The inner cylinder is rotatably disposed within the outer cylinder and is also fixed to the first end of the shaft. The inner cylinder includes a drive pin extending horizontally through the inner and outer cylinders. The drive pin has a pair of ends, one or both of which are received within the outer cylinder&#39;s circumferential slit and seatable within the detent(s). The seating of the drive pin within the detent(s) prevents rotation of the outer cylinder with respect to the inner cylinder. The spring is disposed within the outer cylinder and urges the inner cylinder in a direction toward the bone anchor-mount. Compression of the spring releases the drive-pin ends from the detents, permitting rotation of the handle.  
         [0011]     In this example, the handle is rotatable between first and second angular positions separated by about 180°, but the detents may be located to provide any desired angular displacement between stops as dictated by the application. The handle may be placed in the first angular position for insertion of the device into a cavity and rotated to the second angular position for implanting the bone anchor. The handle may also have additional angular stop positions.  
         [0012]     The bone anchor-mount may comprise an outer cylinder, an inner cylinder, and a tapered bone anchor receptacle for releasably engaging a bone anchor. In one representative bone anchor-mount, the outer cylinder has a distal end and a proximal end. An annular shoulder is located at the proximal end of the outer cylinder. The inner cylinder is rigidly connected to the outer cylinder and extends proximally therefrom. The bone anchor receptacle is rigidly connected to the inner cylinder and extends proximally therefrom. The device may further comprise a protective sheath connected to the bone anchor-mount for isolating the bone anchor from contact with tissue prior to implantation of the bone anchor into a bone. The protective sheath may be axially movable relative to the bone anchor such that the bone anchor is exposed from the sheath as the bone anchor is pulled or pressed into a bone. In a preferred embodiment, the protective sheath is composed of a flexible material such as, for example, silicone or rubber.  
         [0013]     In another aspect, the present invention provides a method for inserting a bone anchor releasably engaged to a bone anchor implantation device into a bone. The bone anchor implantation device is inserted, a bone anchor implantation site is located on the bone, and a retrograde force is applied to the bone anchor to implant the bone anchor into the bone. The handle may contain one or more finger indentations and may be in a first position for insertion of the device into a body cavity and rotated to a second position for implanting the bone anchor. The locating and implanting steps may be accomplished transvaginally. For procedures relating to FSUI, the bone anchor may be implanted in the posterior pubic bone or implanted lateral to the symphysis pubis and cephalad to the inferior edge of the pubic bone. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     In the drawings, like reference characters generally refer to the same parts throughout the different views. Also, the drawings are not necessarily to scale, emphasis being placed upon illustrating the principles of the invention.  
         [0015]      FIG. 1  is a perspective view of a bone anchor implantation device having an ergonomic handle and a shaft.  
         [0016]      FIG. 2  is a perspective view of a bone anchor implantation device having an ergonomic handle and a bent shaft.  
         [0017]      FIG. 3A  is a side view of a bone anchor implantation device having an ergonomic handle and a hooked shaft.  
         [0018]      FIG. 3B  is a perspective view of a bone anchor implantation device having an ergonomic handle and a bent shaft.  
         [0019]      FIG. 3C  is a perspective view of the handle of the device in  FIG. 3B .  
         [0020]      FIG. 3D  is a top view of the handle of the device in  FIG. 3B .  
         [0021]      FIG. 3E  is a side view of the handle of the device in  FIG. 3B .  
         [0022]      FIG. 3F  is a rear view of the handle of the device in  FIG. 3B .  
         [0023]      FIG. 3G  is a front view of the handle of the device in  FIG. 3B .  
         [0024]      FIG. 3H  is a bottom view of the handle of the device in  FIG. 3B .  
         [0025]      FIG. 4  is an exploded view of the components of a rotatable bone anchor implantation device having an ergonomic handle.  
         [0026]      FIG. 5  is a perspective view of a rotatable bone anchor implantation device with the handle in a first angular position.  
         [0027]      FIG. 6  is a perspective view of a rotatable bone anchor implantation device with the handle in a second angular position.  
         [0028]      FIG. 7  is an exploded view of the components of a rotatable bone anchor implantation device having an ergonomic handle.  
         [0029]      FIG. 8  is a side view of a rotatable bone anchor implantation device with the handle in a first angular position.  
         [0030]      FIG. 9  is a side view of a rotatable bone anchor implantation device with the handle in a second angular position.  
         [0031]      FIG. 10  is a perspective view of the bone anchor-mount.  
         [0032]      FIG. 11  is a cross-sectional view of the bone anchor-mount of  FIG. 10 .  
         [0033]      FIG. 12A  is a perspective view of a bone anchor-mount protective sheath.  
         [0034]      FIG. 12B  is a perspective view of a protective sheath detached from a bone anchor mount.  
         [0035]      FIG. 12C  is a perspective view of a protective sheath attached to a bone anchor mount in an extended position.  
         [0036]      FIG. 12D  is a perspective view of a protective sheath attached to a bone anchor mount in a compressed position, showing a protruding bone anchor.  
         [0037]      FIG. 12E  is a perspective view of a protective sheath.  
         [0038]      FIG. 13  is a schematic view showing the bone anchor implantation device inserted into the vagina with the proximal end of the second telescoping cylinder contacting the pubic bone.  
         [0039]      FIG. 14  is a schematic view showing an embodiment of the bone anchor implantation device illustrated in  FIG. 13  wherein the handle has been rotated after insertion into the vagina, and showing the implantation of a bone anchor into the pubic bone and the compression of the spring.  
         [0040]      FIG. 15  is a cross sectional view of the bone anchor-mount and protective sheath when the protective sheath is contacting the pubic bone.  
         [0041]      FIG. 16  is a cross sectional view of the bone anchor-mount and the protective sheath when the bone anchor is being implanted into the pubic bone. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0042]     The present invention relates to a device for implanting a bone anchor into bone. It also relates to methods for improving or maintaining a patient&#39;s urinary continence in which bone anchors are inserted transvaginally into the posterior portion of the pubic bone or symphysis pubis.  
         [0043]     A bone anchor implantation device in accordance with the invention may have an ergonomic handle which has at least one finger indentation in the distal end of the handle. The handle may have one, two, three or four or more finger indentations. In one version of this embodiment, the shaft may be attached to the handle between finger indentations.  
         [0044]     A bone anchor implantation device in accordance with the invention may have a handle that can be rotated relative to the shaft of the device, facilitating bone anchor implantation by allowing a physician the flexibility of rotating the handle of the device during the procedure in order to optimize the angle of the bone anchor-mount and shaft relative to the physician&#39;s hand and the patient&#39;s body. For example, the design of the device allows it to be inserted into the vagina of a patient and to position the bone anchor on a bone and for the handle to be rotated about the longitudinal axis of the shaft of the device prior to providing the retrograde force required to implant the bone anchor into a bone. The form of the handle is not critical to its rotation, e.g., the handle does not need indentations for rotation.  
         [0045]     The bone anchor-mount generally points toward the handle, such that the user can drive the bone anchor into the bone by simply pulling back on the handle and using the patient&#39;s body weight to provide an opposing force. Preferably, the longitudinal axis of the bone anchor-mount may be aligned with the longitudinal axis of the handle. A protective sheath may be attached to the bone anchor-mount such that the bone anchor is releasably engaged to the bone anchor-mount but enclosed within the protective sheath and isolated from tissue contact during placement of the device and prior to implantation.  
         [0046]     Referring to the two embodiment illustrated in  FIGS. 1 and 2 , the device  110  has a handle  112 , a cylinder  114 , a shaft  116 ,  117  and a bone anchor-mount  118 ,  119 . The cylinder  114  is connected to, or forms a part of, the handle  112 . The inner end  120  of the shaft  116 ,  117  is connected to the distal end  122  of the cylinder  114 . The bone anchor-mount  118 ,  119  maybe connected to the outer end  124  of the shaft  116 ,  117 .  
         [0047]     The handle  112  may be made of a variety of materials, such as plastic or metal. The shaft  116 ,  117  may be made of a variety of materials, such as stainless steel, one or more engineering plastics, fiber-bearing components, or other rigid materials. Preferably, the shaft  116 ,  117  is made of stainless steel.  
         [0048]     The shaft  116  may be straight as illustrated, for example, in  FIG. 1 . Alternatively, the shaft  117  may be bent, as illustrated, for example, in  FIG. 2  or may be arched or hooked, as illustrated, for example, in  FIG. 3A .  
         [0049]     The handle  112  may have at least one finger indentation  126  at its distal end  128 . The physician&#39;s fingers may be seated in these indentations  126  during operation of the device. The finger indentations  126  are provided and positioned such that a physician has an improved grip for exerting a retrograde force for implanting a bone anchor. In the version illustrated in  FIGS. 1 and 2 , the handle  112  has four finger indentations  126  on its distal end  128 .  
         [0050]     The bone anchor-mount  118 ,  119  is able to releasably engage a bone anchor. In one embodiment of the invention, the bone anchor-mount  118 ,  119  is fixed perpendicular to the outer end  124  of the shaft  116 ,  117 . The outer end  124  may be bent or otherwise angled so that the bone anchor-mount  118 ,  119  is substantially parallel to the shaft  116 ,  117 . For example,  FIG. 1  illustrates an embodiment of the invention in which the outer end  124  is bent at an angle of about 90° relative to the longitudinal axis of the shaft  116  and the bone anchor-mount  118  is parallel to the shaft  116 . Alternatively, the outer end  124  may be angled more or less than about 90° relative to the longitudinal axis of the shaft  116 ,  117 . The bone anchor-mount  118 ,  119  may be fixed to the shaft  116 ,  117  at an angle greater or less than 90°.  
         [0051]     The bone anchor-mount  118 ,  119  may be oriented toward the handle  112  so that a bone anchor received within the bone anchor-mount  118 ,  119  may be implanted into a bone by applying a retrograde force (e.g., a pulling force) using the handle  112 .  
         [0052]     Referring to the device  210  of  FIG. 3A , a handle  212  having a different configuration is attached to the inner end  214  of the shaft  216 . The handle is also designed to ergonomically fit the fingers of a physician&#39;s hand. As illustrated, the handle contains three finger indentations  220  at its distal end  222 . Alternatively, the handle  212  may contain two, four or more finger indentations  220  at its distal end  222 . In addition, the proximal end  218  of the handle  212  is shaped to fit a physician&#39;s palm.  FIGS. 3B-3H  illustrate various views of a preferred embodiment of the invention in which the handle  212  has three lower finger indentations  220  and one upper finger indentation  220 .  
         [0053]     Referring to  FIG. 3A , the shaft  216  comprises an inner end  214  and an outer end  224 , a straight proximal section  226 , a first generally curved section  228  distal to the straight proximal section  226 , a second generally curved section  230  distal to the first curved section  228 , a third generally curved section  232  distal to the second curved section  230 , and a fourth generally curved section  234  distal to the third curved section  232 . The straight proximal section  226  of the shaft  216  may be from about 3 inches to about 6 inches in length, depending on the application. For FSUI procedures, the straight proximal section  226  is preferably from about 4 inches to about 5 inches in length and more preferably about 4.5 inches in length. One of skill in the art will appreciate that the shaft  216  could also comprise a series of straight segments angled relative to one another to form a hook.  
         [0054]     The inner end  214  of the shaft  216  may be connected to the distal end  222  of the handle  212  in between finger indentations  220 . Alternatively, the straight proximal section  226  may pass through a lumen (not shown) extending through the distal end  222  of the handle  212 . The inner end  214  may have a threaded bore which may be adapted to receive a screw  236  which secures the shaft  216  to the handle  212 . If desired, a washer (not shown) may be placed between the distal end  222  of the handle  212  and the screw  236 . Those skilled in the art will appreciate that a variety of other means for securing the shaft  216  to the handle  212  may be employed. For example, a plastic handle may be formed over the shaft such that the shaft is integral with the handle. It should be stressed that the benefits of an ergonomic handle  112 , as illustrated in  FIG. 1 , and an ergonomic handle  212 , as illustrated in  FIG. 3 , may be utilized in devices that do not permit rotation.  
         [0055]     With continued reference to  FIG. 3A , the handle  212  defines an axis at the proximal end of the anchor implantation device  210 , and then moving distally from the handle  212  the shaft  216  first curves away from the axis of the handle and then back toward the axis of the handle  212 . The outer end  224  of the shaft  216  is preferably located in the vicinity of the axis of the handle  212 . In some preferred embodiments, the shaft  216  at the outer end  224  is generally perpendicular to the axis of the handle or can actually curve back toward the handle  212 . For FSUI applications, the distance from the distal end  222  of the handle  212  to the tip of the bone anchor-mount  238  measured along the longitudinal axis of the handle  212  is preferably about 3 and ⅜ inches; the distance from the distal end of the handle  212  to the base of the bone anchor-mount  240  is about 4 inches; and the distance of a line perpendicular to the longitudinal axis of the handle  212  extending from the bottom of the third curved section  232  is about 2 inches.  
         [0056]     A bone anchor-mount  240  may be attached to the outer end  224  of the shaft  216 . The bone anchor-mount  240  may be oriented at an angle from about 60° to about 120° relative to the outer end  224  of the shaft  216 . For FSUI applications, the bone anchor-mount  240  is preferably oriented at an angle from about 80° to about 100°. relative to the outer end  224  of the shaft  216 , and more preferably at an angle of approximately 90°.  
         [0057]     In another version of the invention, illustrated for example in  FIGS. 4-6 , the handle of the bone anchor delivery device may be rotatable about the longitudinal axis of the shaft. The device  310  has a stop assembly  312  operable within the cylinder  314 , which is located at the base of the handle  316 . The stop assembly  312  retains the handle  316  in any of two or more angular positions.  
         [0058]     Referring to  FIG. 4 , the stop assembly  312  includes a cylinder  314 , a spring  318 , a cylindrical plug  320 , and a drive pin  322 . The cylinder  314  has a proximal end  324 , a distal end  326 , a lumen  328 , a proximal shoulder  330 , a distal shoulder  332 , a circumferential slit  334  and one or more detents  336  within the slit  334 . The plug  320  has a proximal end  338 , a distal end  340 , a drive pin aperture  344  for receiving the drive pin  322 , a proximal face  346 , and a distal face  348 . The plug  320  may have a lumen  342 . The distal end  340  of the plug  320  is fixed to the near end  350  of the shaft  352 . The drive pin  322  is received within the drive pin aperture  344  but not fully, so that it protrudes beyond the radial extent of the plug  320 . Alternatively, the aperture  344  may extend fully through the plug  320 , and the drive pin  322  may have a length greater than the diameter of the plug  320 , so that each end of the drive pin  322  protrudes beyond the radial extent of the plug  320 . Alternatively, the plug  320  may contain more than one aperture and receive more than one drive pin  322 .  
         [0059]     The plug  320  is spring loaded into the cylinder  314 , and the drive pin  322  is introduced into the drive pin aperture  344  so that it engages with (i.e., is movable within) the circumferential slit  334  in cylinder  314 . The distal face  348  of the plug  320  is retained behind the distal shoulder  332  of the cylinder  314 , thereby preventing plug  320  from exiting the cylinder  314 , notwithstanding the force applied by spring  318 . The spring  318  is disposed between the proximal face  346  of the plug  320  and the proximal shoulder  330  of the cylinder  314 . The spring  318  urges the plug  320  in a direction toward the bone anchor-mount  354 .  
         [0060]     The spring  318  may have a resistance of from about 5 to about 35 pounds. Preferably, the spring  318  has a resistance from about 15 to about 25 pounds, and more preferably, about 20 pounds. Those skilled in the art will appreciate that the anchor implantation device may also be adapted to include a force indicating spring in the handle.  
         [0061]     The handle  316  may be rotatable between first and second angular positions, which are dictated by the placement of detents  336  in the cylinder  314 . When the drive pin  322  is seated within the detent  336 , no rotation is possible, and the spring  318  retains the seating of the drive pin  322  until the handle  316  is driven forward, compressing the spring  318 . When the spring  318  is compressed, the drive pin  322  is released from the detent  336  and is free to travel within the circumferential slit  334 , thereby allowing the handle  316  to be rotated about the plug  320 . The handle  316  may be rotated until the spring  318  locks or seats the drive pin  322  into one or more detents  336 , thereby preventing further rotation of the handle  316  with respect to the shaft  352 . In one version of the device, two detents  336  are diametrically opposed along the circumferential slit  334  of the cylinder  314 .  
         [0062]     The drive pin  322  may engage one detent in the cylinder  314  if only one end of the drive pin  322  extends beyond the plug  320 . Alternatively, the drive pin  322  may engage two detents  336  in the cylinder  314  if both ends of the drive pin  322  extend beyond the plug  320  and through the circumferential slit  334 . There may be more detents  336  along the circumferential slit  334 , so that the handle  316  may be rotated among more than two angular positions. There may also be more than one drive pin  322 ; for example, a cross-shaped drive pin may be used to simultaneously be seated in four detents  336 .  
         [0063]     As illustrated in  FIG. 5 , the drive pin  322  is seatable within detent(s)  336  and the handle  316  is in a first angular position.  FIG. 6  illustrates the device shown in  FIG. 5  after rotation of the handle  316  to a second angular configuration, with the drive pin  322  seated within a second detent (or detents)  337 . The first and second angular positions may be, for example, about 180° apart. Of course, depending on the envisioned application, the first and second angular positions may be more or less than about 180° apart.  
         [0064]     In a version of the invention as illustrated to  FIGS. 7-9 , a rotatable handle  416  may have a different configuration, in that it may be attached to the inner end  414  of the shaft  452 . The handle may be designed to ergonomically fit the fingers of a physician&#39;s hand, as in the non-rotatable device of  FIG. 3 . The device  410  is rotatable in a similar fashion as that described for the device illustrated in  FIGS. 4-6 .  
         [0065]     Referring to  FIG. 7 , the handle  416  may be rotatable between first and second angular positions, which are dictated by the placement of detents  436  in the cylinder  414 . When the drive pin  422  is seated within the detent  436 , no rotation is possible, and the spring  418  retains the seating of the drive pin  422  until the handle  416  is driven forward, compressing the spring  418 . When the spring  418  is compressed, the drive pin  422  is released from the detent  436  and is free to travel within the circumferential slit  434 , thereby allowing the handle  416  to be rotated about the plug  420 . The handle  416  may be rotated until the spring  418  locks or seats the drive pin  422  into one or more detents  436 , thereby preventing further rotation of the handle  416  with respect to the shaft  452 . In one version of the device, two detents  436 ,  437  are diametrically opposed on along the circumferential slit  434  of the cylinder  414 .  
         [0066]     The drive pin  422  may engage one detent in the cylinder  414  if only one end of the drive pin  422  extends beyond the plug  420 . Alternatively, the drive pin  422  may engage two detents  436 ,  437  in the cylinder  414  if both ends of the drive pin  422  extend beyond the plug  420  and through the circumferential slit  434 . There may be more detents  436 ,  437  along the circumferential slit  434 , so that the handle  416  may be rotated among more than two angular positions. There may also be more than one drive pin  422 ; for example, a cross-shaped drive pin may be used to simultaneously be seated in four detents  436 .  
         [0067]     As illustrated in  FIG. 8 , the drive pin  422  is seatable within detent(s)  436 ,  437  and the handle  416  is in a first angular position.  FIG. 9  illustrates the device shown in  FIG. 8  after rotation of the handle  416  to a second angular configuration, with the drive pin  422  seated within a second detent(s)  437 . The first and second angular positions may be, for example, about 180° apart. Of course, depending on the envisioned application, the first and second angular positions may be more or less than about 180° apart.  
         [0068]     Referring to  FIGS. 10 and 11 , the bone anchor-mount  510  may comprise an outer cylinder  512 , an inner cylinder  514 , and a tapered bone anchor receptacle  516  for releasably engaging a bone anchor  518 . The bone anchor used may be the bone anchor disclosed in the U.S. Pat. No. 5,527,342, the entire disclosure of which is incorporated herein by reference.  
         [0069]     The bone anchor-mount  510  and the bone anchor receptacle  516  are oriented so that the bone anchor  518  may be pointed in the general direction of the handle  512 . In a particular embodiment, the axis of the bone anchor  518  may be generally aligned with the axis of the handle, with the bone anchor  518  pointed toward the handle.  
         [0070]     The bone anchor-mount  510  may be fabricated from the same materials as the shaft  516  and may be attached to the shaft  516  by a variety of methods known to those skilled in the art, such as brazing. The distal end  520  of the outer cylinder  512  has a pair of holes  522  therein sized to accommodate a suture  524 . The outer cylinder  512  may have a diameter from about 0.18 inches to about 0.6 inches. Preferably, the outer cylinder  512  has a diameter from about 0.25 inches to about 0.5 inches. More preferably, the outer cylinder  512  has a diameter of about 0.375 inches.  
         [0071]     As best shown in  FIG. 11 , the outer cylinder  512  has a cavity  526  formed therein, creating a cup in the proximal region of the outer cylinder  512 . The proximal end  528  of the outer cylinder  512  has an annular shoulder  530  thereon. The inner cylinder  514  may be connected to the outer cylinder  512  and extends into the cavity  526 . The inner cylinder  514  may be connected to the outer cylinder  512  in a variety of ways known to those skilled in the art. For example, the inner cylinder  514  may be fused to the outer cylinder  512 . Inner cylinder  514  may have grooves  532  therein adapted to accommodate a suture  524 .  
         [0072]     A tapered bone anchor receptacle  516  extends from the proximal end  534  of the inner cylinder  514 . The tapered bone anchor receptacle  516  may extend from the proximal end  534  of the inner cylinder  514  by a distance of from about 0.3 inches to about 0.7 inches. Preferably, the tapered bone anchor receptacle  516  extends from the proximal end  534  of the inner cylinder  514  by a distance of from about 0.4 inches to about 0.6 inches. More preferably, the tapered bone anchor receptacle  516  extends from the proximal end  534  of the inner cylinder  514  by a distance of about 0.5 inches.  
         [0073]     The proximal end  540  of the tapered bone anchor receptacle  516  preferably has a width smaller than that of the proximal end  534  of the inner cylinder  514 . This configuration produces a shoulder  538  which may serve as a depth stop to ensure that the bone anchor  518  may be driven into the bone to the desired depth.  
         [0074]     The proximal end  540  of the tapered bone anchor receptacle  516  may be from about 0.08 inches to about 0.12 inches in width. Preferably, the proximal end  540  of the tapered bone anchor receptacle  516  is from about 0.09 inches to about 0.110 inches in width. More preferably, the proximal end  540  of the tapered bone anchor receptacle  516  is 0.1 inches in width.  
         [0075]     The distal end  536  of the tapered bone anchor receptacle  516  may be from about 0.110 inches to about 0.15 inches in width. Preferably, the distal end  536  of the tapered bone anchor receptacle  518  is from about 0.12 inches to about 0.14 inches in width. More preferably, the distal end  536  of the tapered bone anchor receptacle  516  is 0.13 inches in width. The distal end  536  of the tapered bone anchor receptacle  516  may have a variety of cross sectional shapes adapted to releasably engage the bone anchor  518 . For example, the distal end  536  of the tapered bone anchor receptacle  516  may be square, rectangular, pentagonal, triangular or hexagonal in cross section.  
         [0076]     The tapered bone anchor receptacle  516  may have a notch  542  therein in which the bone anchor  518  may be releasably seated. Alternatively, the outer cylinder, inner cylinder, and tapered bone anchor receptacle may be a single integral component.  
         [0077]     The bone anchor implantation device may have a protective sheath  544  connected to the bone anchor-mount  510  which protects the point of the bone anchor from tissue contact during placement of the device and also protects the bone anchor from contacting potentially infectious microorganisms. The protective sheath  544  comprises a first telescoping cylinder  546  and a second telescoping cylinder  548 . A spring  550  biases the first telescoping cylinder  546  and the second telescoping cylinder  548  to a position in which they extend from the outer cylinder  512  and cover the bone anchor  518 . The first and second telescoping cylinders  546 ,  548  may be made of a variety of materials such as stainless steel or plastic. Preferably, the first and second telescoping cylinders  546 ,  548  are made of stainless steel.  
         [0078]     The first telescoping cylinder  546  has a lumen  552  extending therethrough. The first telescoping  546  cylinder has a first shoulder  554  which engages shoulder  530  on the outer cylinder  512  and a second shoulder  556  which engages a first shoulder  558  on the second telescoping cylinder  548 . The second telescoping cylinder  548  has a first shoulder  558  which engages the second shoulder  556  on the first telescoping cylinder  546  as described above. A second shoulder  560  may be located at the proximal end of the second telescoping cylinder  548  and engages the spring  550 . The second telescoping cylinder  548  also has a lumen  562  extending there through which may be in fluid communication with the lumen  552  of the first telescoping cylinder  546  and the cavity  526  in the outer cylinder  512 .  
         [0079]     In the embodiments of the invention illustrated in  FIGS. 12A-12E , the outer end  570 ,  670  of the shaft  572 ,  672  and the bone anchor-mount  574 ,  674  are covered by a flexible hood  576 ,  676 . Referring to  FIG. 12A , the flexible hood  576  may be removable, and may have a hinge region  578 . In an alternative embodiment pictured in  FIG. 12B , the flexible hood  676  snaps on to the outer end  670  of the shaft  672 , e.g., facilitated by grooves  677  in the outer end  670  of the shaft  672  which receive edges defined by holes  680  in the hood  676 .  FIG. 12B  shows an unattached hood  676  and a shaft  672 .  FIG. 12C  shows the hood  676  attached to a shaft  672 , with the hood  676  in an extended position covering the bone-anchor mount  674 .  FIG. 12D  shows the hood configuration of  FIG. 12C  in its collapsed or compressed position, the flexible walls of the hood  676  bending outward allowing the bone anchor to protrude from the hood  676 . In this embodiment, when a bone anchor is installed, the hood  676  collapses and slides back on the bone anchor mount  674  as illustrated in  FIG. 12C . Another version of the hood of the invention is illustrated in  FIG. 12E . In this version, the hood comprises a chamber  682  shaped to fit the outer end  670  of the shaft  672 . In that embodiment, the hood  676  comprises a flared region  684  at the distal end of the hood  686 . The hood compresses in a manner analogous to that shown in  FIG. 12D  when the bone anchor is being placed. In a preferred embodiment, the material used to make the hoods is a soft or pliable material, such as soft rubber or silicone.  
         [0080]     An alternative embodiment of the bone anchor implantation device  610  is shown in  FIG. 13 . As illustrated therein, the shaft  612  has a generally straight proximal section  615 , a first generally bent section  617 , a generally straight median section  618 , a second bent section  620 , a generally curved section  622 , and a distal generally straight section  624 . The first bent section  617  may bend at an angle of from about 35° to about 55° relative to the straight proximal section  615 . Preferably, the first bent section  617  bends at an angle of from about 40° to about 50° relative to the straight proximal section  615 . More preferably, the first bent section  617  bends at an angle of about 45° relative to the straight proximal section  615 .  
         [0081]     The second bent section  620  may bend at an angle of from about 125° to about 145° relative to the straight median section  618 . Preferably, the second bent section  620  bends at an angle of from about 130° to about 140° relative to the straight median section  618 . More preferably, the second bent section  620  bends at an angle of about 135° relative to the straight median section  618 .  
         [0082]     The curved section  622  may curve through an arc of from about 70° to about 110° with a radius from about 0.2 inches to about 0.6 inches. Preferably, the curved section curves  622  through an arc of from about 80° to about 100° with a radius from about 0.3 inches to about 0.5 inches. More preferably, the curved section  622  curves through an arc of about 90° with a radius of 0.4 inches.  
         [0083]     The bone anchor implantation device  610  may be inserted transvaginally as shown in  FIG. 13  with the patient in the lithotomy position and the surgeon located between the patient&#39;s legs. As used herein, the terms “transvaginally” or “transvaginal access” refer to access through the vaginal introitus or from within the vagina. An incision in the anterior vaginal wall may be made. The shaft  612  may be inserted through the incision and the protective sheath may be positioned such that the proximal end of the second telescoping cylinder  632  contacts the pubic bone  630 . At this time, the first and second telescoping cylinders  626 ,  632  are biased to a position in which they extend from the outer cylinder  634  to cover the bone anchor  629 . The bone anchor  629  may be inserted into the bone by applying a retrograde force to the bone anchor  629 . For example, the handle may be pulled in a retrograde direction (toward the user) to implant the anchor. As best illustrated in  FIGS. 15 and 16 , as the device is pulled in a retrograde motion, the first and second telescoping cylinders  626 ,  632  retract inside the cavity  636  of the outer cylinder and the bone anchor  629  may be driven into the pubic bone  630 . Because the patient&#39;s body weight provides an opposing force, the user need only apply a small amount of force, such as 10-20 pounds, in order to drive the bone anchor  629  into the bone  630 . The device  610  may then be pushed away from the implanted anchor to disengage the device from the anchor. The device may then be removed from the vagina, leaving the bone anchor  629  in the bone  630  with the suture extending therefrom. The bladder neck may then be compressed, suspended or stabilized using the suture(s) extending from the bone anchor(s) as described above.  
         [0084]     In another version of the method, the handle  616  may be rotated after insertion into the vagina and prior to providing the retrograde force for implanting the bone anchor.  FIG. 13  illustrates a bone anchor delivery device in a first position. By compressing the handle  616  and rotating the handle  616  relative to the shaft  612  as described previously herein, the handle  616  can be moved to a second position, e.g., as illustrated in  FIG. 14 . Once in the second position, a retrograde force can be applied to insert the bone anchor  629  into the bone  630 .  
         [0085]     The methods and devices of the present invention drive a bone anchor through, for example, the vaginal wall and into the posterior portion of the pubic bone or symphysis pubis. At least one bone anchor may be driven into the pubic bone on either side of the urethra. However, one of skill in the art will appreciate that a single bone anchor may also be used. At least one suture may be attached to the bone anchors which may extend through the vaginal wall and may then be attached to the endopelvic fascia, the vaginal wall, a sling, or other material to stabilize and/or slightly compress the urethra, thereby improving or maintaining the patient&#39;s urinary continence.  
         [0086]     Although this invention has been described in terms of certain preferred embodiments, other embodiments which will be apparent to those of ordinary skill in the art in view of the disclosure herein are also within the scope of this invention. Accordingly, the scope of the invention is intended to be defined only by reference to the appended claims.