Abstract:
Surgical procedures, kits and implants for alleviating human incontinence, and particularly providing improved methods and apparatus to secure a urethral sling to pubic bone in a sub-urethral location to support the urethra and alleviate incontinence are disclosed. Bone anchors, e.g., bone screws, are driven into pubic bones with exposed bone anchor heads and necks configured to receive and support a urethral sling applied to the bone anchors with and without retainers applied against the urethral sling to retain portions of the urethral sling between the bone anchor heads and the pubic bones.

Description:
RELATED APPLICATIONS 
     This application claims priority to International Application having Serial No. PCT/US2006/023872 filed Jun. 20, 2006, which claims priority to U.S. Provisional Application Ser. No. 60/692,662 filed Jun. 21, 2005, the entire contents of both are incorporated herein by reference. 
    
    
     The present invention pertains to surgical procedures, kits, and implants to alleviate human incontinence, and particularly to improved methods and apparatus to secure a urethral sling to pubic bone in a sub-urethral location to support the urethra and alleviate incontinence. 
     BACKGROUND 
     Incontinence is a condition characterized by involuntary loss of urine, beyond the individual&#39;s control, that results in the loss or diminution of the ability to maintain the urethral sphincter closed as the bladder fills with urine. Male or female stress urinary incontinence (SUI) occurs when the patient is physically or emotionally stressed. 
     One cause for this condition is damage to the urethral sphincter or loss of support of the urethral sphincter, such as can occur in males after prostatectomy or following radiation treatment, or that can occur due to pelvic accidents and aging related deterioration of muscle and connective tissue supporting the urethra. Other causes of male incontinence include bladder instability, over-flowing incontinence and fistulas. 
     The female&#39;s natural support system for the urethra is a hammock-like supportive layer composed of endopelvic fascia, the anterior vaginal wall, and the arcus tendineus (a distal attachment to the pubic bone). Weakening and elongation of the pubourethral ligaments and the arcus tendineus fascia pelvis, weakening of the endopelvic fascia and pubourethral prolapse of the anterior vaginal wall, and their complex interaction with intraabdominal forces are all suspected to play a role in the loss of pelvic support for the urethra and subsequent hypermobility to an unnaturally low non-anatomic position, leading to urinary incontinence. 
     Females can also exhibit cystocele, a condition due to laxity of the pelvic floor wherein the bladder extrudes out and downwards causing SUI. The severity of this bladder collapse is rated between Grades one through four. In Grade four cystocele, the bladder extrudes out of the vaginal opening. The treatment of choice for this condition includes the reduction or dosing of the pelvic floor opening from which the bladder descends using sutures. As noted below, other procedures involving implantation of a urethral sling are also gaining acceptance. 
     In general, continence is considered to be a function of urethral support and coaptation. For coaptation to successfully prevent or cure incontinence, the urethra must be supported and stabilized in its normal anatomic position. 
     The present application is directed to the treatment of SUI and chronic urinary incontinence due to inability of the urethral sphincter to dose or remain closed as bladder fluid pressure builds. Currently, incontinence treatments of choice involve implantation of a Kaufman Prosthesis, an artificial sphincter (such as the AMS-800 Urinary Control System available from American Medical Systems, Inc.), or a urethral sling procedure in which a urethral sling is inserted beneath the urethra and advanced in the retro pubic space. Peripheral portions of the elongated urethral sling are affixed to bone or body tissue, and a central portion of the elongated urethral sling extends under the urethral or bladder neck to provide a platform that compresses the urethral sphincter, limits urethral distention, and pelvic drop, and thereby improves coaptation. 
     Male and female urethral sling procedures are disclosed in commonly assigned U.S. Pat. Nos. 6,652,450 and 6,382,214, for example, and further female urethral sling procedures are described in commonly assigned U.S. Pat. No. 6,641,524, for example, and publications and patents cited therein. The implantation of certain urethral slings involves the use of delivery systems configured for and techniques that involve transvaginal, transobturator, suprapubic and pre-pubic exposures or pathways. 
     The above-referenced &#39;214 patent describes apparatus and methods for treatment of male incontinence and female cystocele repair in which a urethral sling material is positioned between the descending pubic rami of the pubic bone. In such an operation a “hammock-like” urethral sling material is sutured below the urethra in males, or below the posterior bladder wall in the case of cystocele in females. The urethral sling material may comprise synthetic material or cadaveric or autologous fascia and may or may not be absorbable over time. 
     In the male case, the urethral sling applies passive compression against the bulbar urethra. The compression, either by itself or in conjunction with urethral mobility, prevents urine leak during strain. If additional passive pressure is required on the urethra after surgery is completed, collagen or other bulky material can be injected with a tiny needle through the perineum, causing more pressure created by the bulky material on one side (the lower or caudal side) by the urethral sling, and on the other (the upper or superior) side compressing the urethra. An example of a urethral sling sutured to and extending between four bone screws fixed to the descending pubic rami is depicted in  FIG. 12  of the above-referenced &#39;214 patent. 
     One minimally invasive surgical procedure that incorporates the teachings of the above-referenced &#39;214 patent to alleviate mild to moderate male SUI is performed employing the InVance™ Male Urethral Sling System for implanting the InteMesh™ Synthetic Surgical Mesh (both available from American Medical Systems, Inc.) in a manner generally described in the above-referenced &#39;214 patent and depicted in  FIGS. 1-3 . The InteMesh™ Synthetic Surgical Mesh is about 4 cm×7 cm and knitted from a supple polyester material coated with silicone, the knitted mesh having a pore size that allows for tissue ingrowth during chronic implantation. The InVance™ Male Urethral sling System includes four to six, typically, titanium bone screws and a disposable, battery powered, inserter or driver. Each bone screw has a distal self-tapping spiral thread and a length of No. 1 Prolene suture extending proximally from the bone screw. 
     In the implantation procedure, the patient is first placed in the lithotomy position and draped, and the surgical field is prepared. A 16 French Foley catheter, for example, is inserted into the urethra, the catheter balloon is inflated t to assist the surgeon in identifying the urethra during dissection, and the scrotum is elevated. A vertical incision is made over the midline in the perineum, and the skin and subcutaneous tissues are dissected free. The bulbocavernous muscle is then exposed, and dissection is carried out posteriorly to the area of the transverse perineum to completely free the bulbar urethra. Lateral dissection is used to expose the corpora cavernosum and the descending pubic rami. 
     The six titanium bone screws or anchors are then screwed, one at a time, into the inner portion of the descending pubic rami of the pubic bone using the battery-powered driver. The bone screws are screwed fully into the pubic bone so that the No. 1 Prolene sutures extend outward from each bone. The location of each bone screw and the order of bone screw insertion can be selected by the surgeon. In one approach, the first pair of bone screws is inserted just below the symphysis, the second pair is inserted just proximal to the level of the ischial tuberosity, and the third pair is inserted intermediate the first and second pair. 
     The InteMesh™ Synthetic Surgical Mesh is then applied against the array of bone screws bridging the lower surface of the bulbar urethra between the descending pubic rami to determine where the sutures will be passed through the mesh pores and tied off. The sutures extending from one of the descending pubic rami may be first passed though selected mesh pores and tied off employing several surgeon&#39;s suture knots. Tension is then applied to the other side or end of the urethral sling as it is drawn against the other pubic ramus to determine where the bone screw sutures should be passed through the mesh pores and tied off. 
     The determination of the appropriate tension may be accomplished using a cough test or Retrograde Perfusion Pressure (RPP) test. To perform a RPP test, the Foley catheter balloon is then deflated, and the Foley catheter is withdrawn and connected to a sterile saline perfusion line. A zero pressure state is obtained by lowering the bag to the level of the symphysis. The tip of the catheter is repositioned at the penoscrotal angle, and the urethral resistance to start of flow or leakage is recorded (by distance of the bag above the level of the symphysis). In patients under anesthesia suffering from sphincter incontinence, the urethral resistance is very low. Tension is then applied to the untied side of the urethral sling by advancing the end of the urethral sling along the sutures toward the bone screws so that the urethral sling bears against the bulbar urethra. The mesh urethral sling compresses the bulbar urethra as it is adjusted in tension to increase urethral resistance to withstand a pressure selected between 30 and 60 cm of water. The sutures are then tied to maintain the selected tension. 
     The Foley catheter is then advanced to the bladder (which should advance without difficulties), and the wound is irrigated with Bethadine solution and closed in layers. Subsequently, the Foley catheter is removed after 2 hours, and the patient can be discharged home on oral antibiotics and pain medication after completing a successful voiding trial. 
     The above-referenced &#39;214 and &#39;524 patents also disclose procedures for repairing a cystocele using retropubic and lateral pubic bone anchors. The surgery disclosed in the &#39;214 patent is indicated for patients with grade four cystocele and urethral hypermobility. The procedure repairs the central defect, the lateral defect, approximates the cardinal ligaments to the midline, and creates a urethral sling of the urethra. 
     After preparation and draping, a Foley catheter is inserted in the bladder. Once the catheter is in place, a “goal post” incision is made. The vertical bars of the goal post extend laterally from the distal urethra to the horizontal bar that is made just proximal to the bladder neck. The vertical bars reach the vaginal cuff. 
     After creation of the goal post incision, the vaginal wall is dissected free to expose the perivesical fascia laterally and the cardinal ligaments posteriorly. A figure eight 2-0 absorbable suture is applied to approximate the cardinal ligament to the midline without tying it. If an enterocele sac is encountered, it should be repaired at this stage. 
     The retropubic space is then entered over the periurethral fascia at the level of the vertical bars of the incision, and the urethropelvic ligaments are exposed. Two fascial anchors (the upper pair) are inserted into the tissue of the suprapubic area. Each of these anchors comprises a bone screw having a distal self-tapping screw thread of the type described above with a No. 1 Prolene suture attached to the proximal end of the bone screw. 
     In an alternative embodiment, at this stage of the procedure, the retropubic space is not open and two bone anchors or screws of the type described above are applied to the inner surfaces of the symphisis using a right angle drill. 
     After application of the first set of anchors, a second pair of bone anchors or screws of the type described above are applied to the inner surface of the descending pubic rami of the symphysis. 
     Once the four bone screws are in place, the bladder prolapse is reduced using a moist sponge over a right angle retractor. Alternatively, a Dexon mesh is applied and left in place. The lower pair of Prolene sutures is then used to incorporate the perivesical fascia and the cardinal ligaments area. Interrupted 2-0 absorbable sutures are used to approximate the perivesical fascia to the midline over the Dexon mesh. 
     A variation on this procedure is set forth in commonly assigned, U.S. Patent Application Publication No 2002/0183762 to provide urethral support and coaptation employing the InFast™ Ultra Transvaginal Urethral sling System for implanting a urethral sling selected from among the InteXen™ Porcine Dermal Matrix or the InteDerm™ Allograft Dermal Matrix or the InteLata™ Allograft Fascia Lata (all available from American Medical Systems, Inc.). The selected urethral sling is intended to be cut to size and in a T-shape to fit between the bone screws and to be attached thereto as described above. The InFast™ Ultra Female Urethral sling System includes four, typically, titanium bone screws and a disposable, battery powered, inserter that positively engages the bone screw to drive it into bone. In this system, a length of No. 1 Prolene suture is passed through a metal ring extending proximally from the bone screw, and the ends of the suture are joined to needles adapted to be passed through the urethral sling. A distal end of a drive shaft of the battery-powered inserter engages the bone screws, and the drive shaft is shaped to enable orientation of the screw threads toward the posterior aspect of the pubic bone. Other types of bone anchors that include a penetrating tip, a shaft, and a suture threaded through the shaft and that are adapted to be inserted into bone are disclosed in commonly assigned U.S. Pat. Nos. 6,635,058 and 6,746,455. 
     The tensioning of the selected urethral sling is accomplished in this procedure as the suture needles are passed through the urethral sling, and the urethral sling is pressed against the bone surface. The suture needles are severed, and the suture ends are tied together. The tied suture knot is slid upward and posteriorly (behind the bone) to ensure juxtaposition of the sling end to the bone surface. 
     The above-described bone screws are intended to be driven into the bone until completely embedded with the suture extending out of the self-tapped bore in the bone. 
     Thus, in the above-described procedures, the urethral sling in maintained in place, and sling tension is adjusted and applied through the tied sutures. The procedure of initially tensioning and tying the sutures takes an undue amount of the surgical time, up to 15-25 minutes as observed in some instances employing the InVance™ Male Urethral Sling System for implanting the InteMesh™ Synthetic Surgical Mesh. Moreover, it is sometimes difficult to achieve the tension in the urethral sling that is sufficient to constrict the urethral sphincter to provide urethral resistance to leakage at the selected water bag height, e.g. at 60 cm. 
     If the resulting sling tension is not adequate, it may be necessary to untie the tied sutures to readjust tension including possibly repositioning the bone screw in the pubic bone or the sutures extending through the urethral sling. Tying, untying and retying the suture knots consumes further time. Thus, it would be desirable to simplify the process of and to reduce the amount of time that it takes to detach, adjust tension, and reattach the urethral mesh to the sutures extending from bone screws. 
     Moreover, the sutures may have been trimmed at the knot following an earlier tying. Applying tension through and retying the trimmed sutures may be difficult to accomplish. Therefore, it would be desirable to simplify the process of tensioning and retying the sutures in a manner that is not compromised by trimming the suture length. 
     In addition, redundant knots are often tied to increase reliability of the suture knot, and the size of the knots so formed can irritate adjacent enervated tissue, causing discomfort to the patient. Consequently, it would be desirable to minimize the physical size of suture fixation of the urethral sling to the bone anchors or screws. 
     Various types of bone anchors that include a penetrating tip, a shaft, and a head and are adapted to be inserted into bone are disclosed in commonly assigned U.S. Pat. Nos. 6,328,744, 6,387,041, 6,544,273, 6,730,110, and 6,843,796. In certain embodiments disclosed in the &#39;041 patent, for example, the head extends at an angle to the shaft axis, and may comprise laterally extending arms or may comprise a circular plate, a sphere or a half-sphere. In use, the tip is advanced through the sling so that the sling bears against the shaft and is maintained there by the head. 
     SUMMARY 
     The preferred embodiments of the present invention incorporate a number of inventive features that address the above-described problems that may be combined as illustrated by the preferred embodiments or advantageously separately employed. 
     The kits, tools, and/or components of the preferred embodiments of the present invention may be employed to affix a sling to a bone or bones, in particular, a urethral sling to pubic bones. The urethral sling may be of any type having opposed sling sides and extending between a first sling end adapted to be coupled to a first pubic bone and a second sling end adapted to be coupled to a second pubic bone to fix the urethral sling in a sub-urethral location to support the urethra and alleviate incontinence. The urethral sling may be formed of material having sling openings extending through it at least in portions adjacent the first and second sling ends. In the case that the urethral sling is formed of a mesh having mesh pores for tissue ingrowth, mesh pores may be selected to function as sling openings. Alternatively, the urethral sling may be formed of a material capable of being perforated in the surgical procedure to form sling openings extending through it at least in portions adjacent the first and second sling ends. 
     The kits, tools and/or components of the preferred embodiments of the present invention include bone anchors with exposed bone anchor heads and necks configured to receive and support a urethral sling applied to the bone anchors with retainers applied against the urethral sling to retain portions of the urethral sling between the bone anchor heads and the pubic bones. 
     In one aspect of the present invention, the bone anchor is formed with an anchor shaft or body having an anchor body axis extending from a proximal anchor head through an anchor neck to a distal anchor tip. The parts of the anchor body have length dimensions aligned with the anchor body axis and lateral dimensions lateral to the anchor body axis. Thus, the anchor body may have a neck dimension and a head dimension lateral to the anchor body axis. The neck and head dimensions may be a diameter or cross-section area when the head and neck are substantially circular extending laterally through 360° rotation about the anchor body axis. The neck and head dimensions may be a length or thickness in a direction lateral to the anchor body axis when the head and neck are not substantially circular and do not extend laterally through 360° rotation about the anchor body axis. The terms “lateral” and “laterally” may reference dimensions or directions or vectors that are substantially transverse to the bone anchor axis or that are not transverse to the bone anchor axis. 
     In a further aspect of the invention, the bone anchor is reduced in a neck dimension or cross-section from a head dimension or cross-section of the proximal anchor head lateral to the bone anchor axis. The anchor head dimension is selected to fit through the sling opening as the urethral sling is pressed against the bone anchor head. The urethral sling is tensioned as it is applied in the same manner into engagement with the remaining anchor heads, and the urethral sling is thereby engaged and tensioned against the anchor necks between the pubic bones and the anchor heads. The urethral sling may be quickly manually detached and reattached to change sling tension as tension testing dictates. 
     In another aspect of the invention, a kit is provided comprising at least one bone anchor having an anchor head and at least one sling retainer that engages with the anchor head or anchor neck to bear against the urethral sling to inhibit detachment of the urethral sling from the bone anchor. 
     In certain embodiments, the retainer has a retainer body that is shaped having a laterally extending slot extending to or providing a retainer bore that is sized and shaped to engage the anchor neck. In use, the sling retainer is applied to the anchor neck inserted in bone by laterally advancing the retainer body with the anchor neck positioned in the slot toward the bone anchor axis until the anchor neck is seated in the anchor bore. 
     In other embodiments, the anchor body is resilient and has a retainer bore extending through it having a bore cross-section area less than the anchor head cross-section area. Each anchor head is extended through the sling mesh or a hole prepared in a sling fabric or tissue. Sling tension testing may proceed and repositioning may occur. The resilient annular sling retainer is fitted against the urethral sling by expansion of the retainer bore to snap the sling retainer over the proximal anchor head and entrap it within the anchor neck. 
     In yet another aspect of the present invention, a suture is attached to and extends proximally from the proximal anchor head. The suture extending proximally from the proximal anchor head is adapted to be threaded through a sling opening before the anchor head is extended through the sling opening. Sling tension testing may proceed and repositioning may occur until satisfactory sling tension is achieved. The suture functions as a retainer guide so that a resilient, annular sling retainer may be moved distally over the suture and fitted, by expansion of the retainer bore, to snap over the proximal anchor head and against the urethral sling entrapped by the anchor neck. The suture may be tied off and trimmed after adequate tension is achieved and with fewer knots to reduce suturing time and the final exposed suture bulk. 
     In preferred embodiments of this aspect of the invention, sling retainer dispensing tools are provided that facilitate application of the sling retainers over the sutures and/or anchor heads and/or against the anchor necks to press and entrap the urethral sling material against the bone. 
     Further embodiments of bone anchors employ anchor heads configured to accept particular sling retainers to bear against the urethral sling to retain it in place. 
     Advantageously, procedures for attaching the urethral sling to bone anchors or anchors are simplified to shorten the surgical time, the tensioning and fixation are made more reliable, and the resulting suture knots are reduced in size or eliminated. 
     Bone anchors usable in the practice of the present invention may comprise bone screws having spiral thread bone fixation mechanisms adapted to be screwed into bone or tapered, pointed, bone tack bone fixation mechanisms adapted to be advanced into bone, as disclosed for example in the above-referenced, commonly assigned &#39;058, &#39;273 and &#39;041 patents, or any other form of bone fixation mechanism. 
     These and other advantages and features of the present invention will be more readily understood from the following detailed description of the preferred embodiments thereof, when considered in conjunction with the drawings, in which like reference numerals indicate identical structures throughout the several views, and wherein: 
     This summary of the invention has been presented here simply to point out some of the ways that the invention overcomes difficulties presented in the prior art and to distinguish the invention from the prior art and is not intended to operate in any manner as a limitation on the interpretation of claims that are presented initially in the patent application and that are ultimately granted. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of the fixation of bone anchors, e.g., bone screws, to descending pubic rami with sutures extending from the bone screws in accordance with the prior art; 
         FIG. 2  is a schematic illustration of the fixation of a urethral sling to the bone screws with the sutures extending from the bone screws in accordance with the prior art; 
         FIG. 3  is an enlarged plan view of a prior art urethral sling formed of a mesh and adapted to be attached to the descending pubic rami as shown in  FIG. 2 ; 
         FIG. 4A  is an end view of one embodiment of a bone screw adapted to engage and retain the mesh of the urethral sling of  FIGS. 2 and 3  without sutures; 
         FIG. 4B  is a side view of the bone screw of  FIG. 4A ; 
         FIG. 4C  is a plan view in partial section of the bone screw of  FIGS. 4A and 4B  engaging and retaining the mesh of the urethral sling of  FIGS. 2 and 3  to pubic bone; 
         FIG. 4D  is a plan view in partial section of the bone screw of  FIGS. 4A and 4B  engaging and retaining the mesh of the urethral sling of  FIGS. 2 and 3  to pubic bone and under tension; 
         FIG. 4E  is an enlarged partial side view of the mesh engaging head and neck of the bone screw of  FIG. 4A ; 
         FIG. 5A  is a perspective view of the components of a further embodiment of a bone screw adapted to engage and retain the mesh of the urethral sling of  FIGS. 2 and 3  without sutures; 
         FIG. 5B  is a plan view in partial section of the bone screw of  FIG. 5A  engaging and retaining the mesh of the urethral sling of  FIGS. 2 and 3  to pubic bone; 
         FIG. 6A  is a side view of a further embodiment of a bone screw adapted to engage and retain the mesh of the urethral sling of  FIGS. 2 and 3  without sutures; 
         FIG. 6B  is a top view of a first embodiment of a sling retainer employed with the bone screw of  FIG. 6A  to enhance surface area contact with and retention of the mesh of the urethral sling of  FIGS. 2 and 3  (for example); 
         FIG. 6C  is a plan view in partial section of the bone screw of  FIG. 6A  engaging the mesh of the urethral sling of  FIGS. 2 and 3  and the sling retainer of  FIG. 6B  positioned to be fitted over the bone screw head to bear against the mesh of the urethral sling of  FIGS. 2 and 3  to enhance retention of the mesh to the pubic bone; 
         FIG. 6D  is a plan view in partial section of the bone screw of  FIG. 6A  engaging the mesh of the urethral sling of  FIGS. 2 and 3  and the sling retainer of  FIG. 6B  fitted over the bone screw head to bear against the mesh of the urethral sling of  FIGS. 2 and 3  to enhance retention of the mesh to the pubic bone; 
         FIG. 6E  is a top view of a second embodiment of a sling retainer employed with the bone screw of  FIG. 6A  to enhance surface area contact with and retention of the mesh of the urethral sling; 
         FIG. 6F  is a plan view in partial section of the bone screw of  FIG. 6A  engaging the mesh of the urethral sling of  FIGS. 2 and 3  and the sling retainer of  FIG. 6E  positioned to be fitted over the bone screw head to bear against the mesh of the urethral sling of  FIGS. 2 and 3  to enhance retention of the mesh to the pubic bone; 
         FIG. 6G  is a plan view in partial section of the bone screw of  FIG. 6A  engaging the mesh of the urethral sling of  FIGS. 2 and 3  and the sling retainer of  FIG. 6E  fitted over the bone screw head to bear against the mesh of the urethral sling of  FIGS. 2 and 3  to enhance retention of the mesh to the pubic bone; 
         FIG. 7A  is a plan view in partial section of the bone screw of  FIG. 6A  engaging and retaining the mesh of the urethral sling of  FIGS. 2 and 3  to pubic bone and a sling retainer dispensing tool poised to fit a sling retainer of  FIG. 6C  or  6 F over the bone screw head to bear against the mesh of the urethral sling of  FIGS. 2 and 3  to enhance retention of the mesh to the pubic bone; 
         FIG. 7B  is a plan view in partial section of the bone screw of  FIG. 6A  engaging and retaining the mesh of the urethral sling of  FIGS. 2 and 3  to pubic bone and a sling retainer dispensing tool positioned to fit a sling retainer of  FIG. 6C  or  6 F over the bone screw head to bear against the mesh of the urethral sling of  FIGS. 2 and 3  to enhance retention of the mesh to the pubic bone; 
         FIG. 8A  is a side view of a bone screw of  FIG. 6A  modified to have a suture extending from the bone screw head; 
         FIG. 8B  is an enlarged partial side view of the mesh engaging head and neck of the bone screw of  FIG. 8A ; 
         FIG. 8C  is a plan view in partial section of the bone screw of  FIG. 8A  engaging the mesh of the urethral sling of  FIGS. 2 and 3  and the sling retainer of  FIG. 6C  fitted over the suture and then over the bone screw head to bear against the mesh of the urethral sling of  FIGS. 2 and 3  to enhance retention of the mesh to the pubic bone; 
         FIG. 9A  is a perspective exploded view of a powered screwdriver having a screwdriver tip for engaging and rotating the head of a bone screw of  FIG. 8A  or  FIG. 6B  and adapted to support a sling retainer to be applied over the bone screw head to bear against mesh of the urethral sling of  FIGS. 2 and 3  to enhance retention of the mesh to pubic bone; 
         FIG. 9B  is a perspective view of the powered screwdriver of  FIG. 9A  supporting a sling retainer in position proximate the screwdriver tip 
         FIG. 9C  is a plan view in partial cross-section of the disposable tool of  FIGS. 9A and 9B  supporting a sling retainer and positioned over the suture of the bone screw of  FIG. 8A  to couple the screwdriver tip to the bone screw head and apply the sling retainer over the bone screw head to bear against the mesh of the urethral sling of  FIGS. 2 and 3  to enhance retention of the mesh to the pubic bone; 
         FIG. 10A  is a perspective view of a further embodiment of a disposable tool coupled to a sling retainer adapted to be employed in applying the sling retainer over the suture and then over the bone screw head of the bone screw of  FIG. 8A  or over the bone screw head of the bone screw of  FIG. 6B  to bear against the mesh of the urethral sling of  FIGS. 2 and 3  to enhance retention of the mesh to the pubic bone; 
         FIG. 10B  is a plan view in partial cross-section of the disposable tool of  FIG. 10A  coupled to a sling retainer and positioned to apply the sling retainer over the suture and then over the bone screw head of the bone screw of  FIG. 8A  or over the bone screw head of the bone screw of  FIG. 6B  to bear against the mesh of the urethral sling of  FIGS. 2 and 3  to enhance retention of the mesh to the pubic bone; 
         FIG. 11A  is a side view of a further embodiment of a disposable tool coupled to a sling retainer adapted to be employed in applying the sling retainer over the suture and then over the bone screw head of a further embodiment of a bone screw to bear against the mesh of the urethral sling of  FIGS. 2 and 3  to enhance retention of the mesh to the pubic bone; 
         FIG. 11B  is a plan view in partial cross-section of the disposable tool of  FIG. 11A  coupled to a sling retainer and positioned to apply the sling retainer over the suture and then over the bone screw head of the further embodiment of a bone screw to bear against the mesh of the urethral sling of  FIGS. 2 and 3  to enhance retention of the mesh to the pubic bone; 
         FIG. 12A  is a perspective view of a further embodiment of a bone screw formed with a bone screw head adapted to pass through a mesh pore of the urethral sling of  FIGS. 2 and 3 ; 
         FIG. 12B  is a plan view in partial section of the bone screw of  FIG. 12A  engaging and retaining the mesh of the urethral sling of  FIGS. 2 and 3  to pubic bone through the use of a flexible H-shaped sling retainer fixed to the bone screw head; 
         FIG. 12C  is an end view of the bone screw of  FIG. 12A  engaging and retaining the mesh of the urethral sling of  FIGS. 2 and 3  to pubic bone through the use of the flexible H-shaped sling retainer inserted through a transverse bore of the bone screw head; 
         FIG. 12D  is a plan view in partial section of the bone screw of  FIG. 12A  engaging and retaining the mesh of the urethral sling of  FIGS. 2 and 3  to pubic bone through the use of a spring clip, sling retainer; 
         FIG. 12E  is an end view of the bone screw of  FIG. 12A  engaging and retaining the mesh of the urethral sling of  FIGS. 2 and 3  to pubic bone through the use of the spring clip, sling retainer inserted through a transverse bore of the bone screw head; 
         FIG. 13A  is a perspective view of a further embodiment of a bone screw formed with a bone screw head adapted to be passed through a mesh port to engage and retain the mesh of the urethral sling of  FIGS. 2 and 3  with or without a sling retainer interposed between the bone screw head and the urethral sling; 
         FIG. 13B  is a plan view in partial section of the bone screw of  FIG. 13A  engaging and retaining the mesh of the urethral sling of  FIGS. 2 and 3  to pubic bone through the application of at least one laterally extending tine, prong or hook of the bone screw head bearing against the urethral sling; 
         FIG. 14A  is a perspective view of a further embodiment of a bone screw formed with a bone screw head adapted to engage and retain the mesh of the urethral sling of  FIGS. 2 and 3  with or without a sling retainer interposed between the bone screw head and the urethral sling; 
         FIG. 14B  is a plan view in partial section of the bone screw of  FIG. 14A  engaging and retaining the mesh of the urethral sling of  FIGS. 2 and 3  to pubic bone through the use of bilaterally extending tines, prongs or hooks of the bone screw head bearing against the urethral sling; 
         FIG. 15A  is a perspective view of a further embodiment of a bone screw formed with a bone screw head with a spiral extension adapted to engage and retain the mesh of the urethral sling of  FIGS. 2 and 3  without a sling retainer interposed between the bone screw head and the urethral sling; and 
         FIG. 15B  is a plan view in partial section of the bone screw of  FIG. 14A  engaging and retaining the mesh of the urethral sling of  FIGS. 2 and 3  to pubic bone through the use of the spiral extension of the bone screw head bearing against the urethral sling. 
     
    
    
     It will be understood that the drawing figures are not necessarily to scale. 
     DETAILED DESCRIPTION 
     In the following detailed description, references are made to illustrative embodiments of methods and apparatus for carrying out the invention. It is understood that other embodiments can be utilized without departing from the scope of the invention. Preferred methods and apparatus are described for affixing urethral slings to pubic bones, particularly the descending pubic rami. 
     It will be understood that the term “urethral sling” encompasses any type of sling, tape, hammock or the like that supports and or/applies compression to the urethra. One exemplary form of urethral sling is illustrated in the figures and described below in use of the kits, tools, and/or components of the preferred embodiments of the present invention that is formed of a mesh having mesh pores that facilitate tissue ingrowth. As noted above, the urethral sling may be formed of any biocompatible flexible sheet material known in the art with or without pores or sling openings through the sheet material. 
     Furthermore, while the bone anchor embodiments are illustrated and described having an anchor body bearing a bone fixation mechanism comprising a spiral thread adapted to be screwed into bone, it will be understood that the principles of the present invention are applicable to other forms of bone anchors. 
     Referring to  FIGS. 1 and 2 , the male anatomy in the pelvic region  10  is depicted schematically to illustrate how a urethral sling  30  is affixed to the right and left descending pubic rami  24  and  26  to extend across and support the male urethra  12  in the manner described above, for example, in the procedure employing the InVance™ Male Urethral Sling System for implanting the InteMesh™ Synthetic Surgical Mesh urethral sling. 
     An embodiment of the urethral sling  30 , which can correspond to the InteMesh™ Synthetic Surgical Mesh urethral sling, is depicted in greater detail in  FIG. 3 . In a preferred embodiment, the urethral sling  30  is knitted into a mesh from a supple polyester yarn to have a plurality of sling openings comprising mesh pores  40  bounded by yarn strands and may be coated with medical grade silicone rubber. The knitted mesh pores  40  have a pore size that allows for tissue ingrowth therethrough during chronic implantation. The urethral sling  30  extends end-to-end between first and second sling ends  32  and  34  and side-to-side between first and second sling sides  36  and  38 . 
     Returning to  FIGS. 1 and 2 , as noted above, the surgical field is prepared after the patient, placed in the dorsal lithotomy position and draped. The scrotum  14  and penis  16  are elevated, a vertical incision is made over the midline in the perineum of the skin and subcutaneous tissues (not shown) are dissected to the side to expose the bulbocavernous muscle  20 . Lateral dissection is used to expose the corpora cavernosum  22  and the surfaces of the descending pubic rami  24  and  26 . 
     As shown in  FIG. 1 , the illustrated fixation of the surgical urethral sling  30  is effected employing six titanium bone screws  64 ,  66 ,  68 ,  70 ,  72 ,  74  sequentially driven by a disposable, battery powered, inserter or driver (not shown). Each bone screw  64 ,  66 ,  68 ,  70 ,  72 ,  74  has a distal self-tapping spiral thread adapted to be screwed into bone when the screw tip is applied to the bone surface and the driver is powered. A pair of No. 1 Prolene sutures  84 ,  86 ,  88 ,  90 ,  92 ,  94  extend proximally from each bone screw  64 ,  66 ,  68 ,  70 ,  72 ,  74 , respectively. One such bone screw  64  with the pair of bone screw sutures  84  extending from the screw head is depicted in the expanded view of  FIG. 5 . Typically, the pair of bone screw sutures is crimped at one end into a bore of the bone screw and extends about 30 cm to bone screw suture free ends. The bone screw suture free ends can be joined as by use of ultrasonic welding to ease in handling and use of a bone screw fixation tool. The surgeon may choose to pass the joined suture free ends through a selected mesh pore, tie a knot or knots, and then trim the sutures. Or, the surgeon may first trim the sutures, separately pass the severed suture free ends through a common or separate mesh pores, tie a knot or series of knots, and again trim the suture free ends. 
     The bone screws  64 ,  66 ,  68 ,  70 ,  72 ,  74  are screwed fully into the bone so that the No. 1 Prolene sutures  84 ,  86 ,  88 ,  90 ,  92 ,  94 , respectively, extend outward of the descending pubic rami  24  and  26  as shown in  FIG. 1 . The surgeon can select the location of each bone screw  64 ,  66 ,  68 ,  70 ,  72 ,  74  and the order of insertion. In one approach depicted in  FIG. 1 , a first pair of bone screws  64 ,  70  is inserted just below the symphysis, the second pair  66 ,  72  is inserted proximal to the level of the ischial tuberosity, and the third pair  68 ,  76  is inserted intermediate the first and second pair. 
     The urethral sling  30  is then applied against the array of bone screws  64 ,  66 ,  68 ,  70 ,  72 ,  74  bridging the lower surface of the bulbar urethra  20  between the descending pubic rami  24  and  26  to determine where each suture of the respective suture pairs  84 ,  86 ,  88 ,  90 ,  92 ,  94  will be passed through mesh pores. 
     The free ends of each suture of each suture pair  84 ,  86 ,  88 ,  90 ,  92 ,  94  are sequentially grasped, passed through separate mesh pores and drawn tight and tied together against the mesh of the urethral sling  30 . 
     The sutures of the suture pairs  84 ,  86 ,  88  extending from the descending pubic ramus  24  may be first passed though selected mesh pores adjacent the first sling end  32 . The first sling free end  32  is then pressed against the descending pubic ramus  24 . The free ends of each suture of each suture pair  84 ,  86 ,  88  are sequentially grasped, drawn tight and tied together at least two times forming several surgeon&#39;s suture knots against the mesh of the urethral sling  30  firmly holding the sling first end against the descending pubic ramus  24 . 
     Tension is then applied to the second sling end  34  of the urethral sling  30  as it is drawn against the second pubic ramus  26  to determine where the sutures of the bone screw suture pairs  90 ,  92 ,  94  should be passed through mesh pores and tied off in the manner described above. Testing for urethral resistance to leakage may be conducted employing the techniques and instruments described above as the sutures of bone suture pairs  90 ,  92 ,  94  are drawn tight against the fabric of urethral sling  30  and tied off. The sutures of bone suture pairs  90 ,  92 ,  94  may be retracted from the initially selected pores  40  and reinserted in other pores  40  in the process of optimizing the tension. In this way, the urethral sling  30  is eventually sutured to all of the bone anchors or screws  64 ,  66 ,  68 ,  70 ,  72 ,  74  inserted into the descending pubic rami  24  and  26  to extend laterally across and support the bulbar urethra  20 . An intermediate portion of the urethral sling  30  extends between the bone screws  64 ,  66 ,  68  and the bone screws  70 ,  72 , and  74 . 
     The knots made with the suture pairs  84 ,  86 ,  88 ,  90 ,  92 , and  94  are relatively bulky and can cause irritation of tissues. In accordance with the present invention, the procedure for securing the urethral sling  30  to the descending pubic rami and tensioning the urethral sling  30  is simplified, the fastening elements are less bulky than the prevailing use of suture knots, and suture knots are eliminated in some embodiments. 
     The present invention may be practiced employing a variety of bone anchors having an anchor body comprising an anchor shaft or body having an axis and extending from a bone penetrating tip through a bone fixation mechanism to an anchor head. The anchor shaft is joined to the anchor head by an anchor neck having a neck dimension lateral to the shaft axis less than an anchor head dimension extending lateral to the shaft axis. The illustrated form of bone anchor is a self-tapping bone screw having a spiral thread bone fixation mechanism that can be manually screwed into bone with a screwdriver or screwed into bone with a motor driven, battery powered screwdriver of the type described above. In each embodiment, the bone screw head or body is configured to mate with a screwdriver tip to be rotated and screwed into a pubic bone, typically the descending pubic ramus. 
     The urethral sling is adapted to be applied against the anchor head to insert the anchor head through the sling opening and apply the sling against the anchor neck. For convenience, the following embodiments are described in the context of attaching the urethral sling  30  of the type depicted in  FIGS. 2 and 3  formed of a mesh with sling openings comprising mesh pores  40  as described above to the descending pubic rami  24 ,  26  generally in at least certain of the locations of the bone screws  64 ,  66 ,  68 ,  70 ,  72 ,  74  or in additional locations. However, the described embodiments and techniques and their equivalents may be employed to advantageously attach any suitable urethral sling not having mesh pores but having other pre-formed sling openings extending through it or that can be perforated to make sling openings during surgery to the descending pubic rami  24 ,  26  or other pubic bone. 
     In one embodiment of the present invention depicted in  FIGS. 4A-4E , a bone screw  50  is screwed into the bone of the right and left descending pubic rami  24  and  26 , in substitution for each of the combined bone screw and suture pair depicted in  FIGS. 1 and 2  and described above. For example, six bone screws  50  are screwed into the bone of the right and left descending pubic rami  24  and  26  where bone screws  64 ,  66 ,  68 ,  70 ,  72 , and  74  are depicted in  FIGS. 1 and 2 . The urethral sling  30  is then attached directly to each bone screw  50 . 
     In the depicted embodiment, the bone screw  50  is formed with a generally conical shaft or screw body  52  having a longitudinal shaft axis and extending between a proximal screw head  54  to a distal screw tip, and a spiral thread  56  extends along the generally conical screw body  52  to a distal screw tip. The screw head  54  has an external driver configuration to mate with a manual or powered screwdriver (not shown) that is employed to rotate and screw the bone screw  50  into bone. For example, the external driver configuration may be fluted or scalloped to have indentations or splines or have flats similar to a hex head that engage with female screw driving head shaped in a hexagonal shape or a Torx shape or the like. It will also be understood that the screw body  52  and the spiral screw thread  56  may take any known form employed in bone screws adapted to be screwed into bone. 
     In preferred embodiments, the bone screw  50  is formed having a screw neck  58  having a screw neck length NL intermediate the screw head  54  and the screw body  52 . Preferably, the proximal screw head  54  is shaped to fit through a mesh pore  40  to engage the urethral sling  30  against the screw neck  58  to hold it in place extending between the right and left descending pubic rami  24  and  26 . The screw neck  58  and the screw head  54  are dimensioned laterally to the longitudinal axis of the screw shaft or body  52  to enable passage of the sling over the screw head  54 , by pressing the sling against the sling to force the screw head  54  through a mesh pore that is stretched in the process. For example, the screw neck  58  has a neck diameter ND less than the head diameter HD of the proximal screw head  54  and the diameter of the proximal end of the screw body  52  where it joins the screw neck  58 . The diameters of the proximal end of the screw body  52  and the maximum diameter of the screw head  54  are selected to exceed the dimensions of the mesh pore  40  and may or may not be the same. The distal surface of the bone screw head  54  may be shaped to catch on the strands forming the mesh of the urethral sling  30 . 
     In use, a plurality, e.g., six, of the bone screws  50  are screwed into the descending pubic rami  24  and  36 , and the urethral sling  30  is applied against the screw head  54  of each bone screw  50  in a selected order. Each screw head  54  extends or pops through a selected mesh pore  40  as the urethral sling  30  is pressed against the screw head  54 . The somewhat elastic strands of the mesh of the urethral sling  30  allow the size of the mesh pore  40  to be expanded as the screw head passes through the selected mesh pore  40 . The size of the mesh pore  40  is restored when the strands are disposed between the screw head  54  and the screw body  52 . The elastic strands bounding the selected mesh pore  40  bear against the reduced diameter screw neck  58 . The urethral sling  30  is tensioned as it is applied in the same manner into engagement with each remaining screw head  54 . The urethral sling  30  is thereby entrapped, engaged, and tensioned between each screw neck  58  of each bone screw  50  screwed into the descending pubic rami  24 ,  26  or other pubic bones. The urethral sling  30  may be readily detached and reattached to change sling tension as tension testing dictates. 
     The bone screws  50  may be screwed into the descending pubic rami  24 ,  26  such that the bone screw axes are perpendicular to the plane of the urethral sling  30  extending between the descending pubic rami  24  and  26  as shown in  FIG. 4C . Alternatively, some or all of the bone screws  50  may be screwed into the descending pubic rami  24 ,  26  such that the bone screw axes are not perpendicular to the plane of the urethral sling  30  extending between the descending pubic rami  24  and  26  as shown in  FIG. 4C . 
     In the embodiment of bone screw  50  depicted in  FIGS. 4A-4E , the bone screw head  54  is integral with the bone screw  50 . It will be understood that the bone screw head may be separate from and attachable to the bone screw body or neck. One embodiment of such a bone screw  100  comprising a bone screw shaft or body  110  and a separate screw head  120  is depicted in  FIGS. 5A and 5B . 
     The bone screw body  110  is generally conical and extends from a proximal bone screw neck  112  through an external driver configuration or element  118  and a spiral screw thread  116  to a distal bone penetrating tip. The distal screw tip and the spiral screw thread  116  may take any known form employed in bone screws. 
     The external driver element  118  on a proximal portion or shoulder of the screw body  110  is shaped to mate with the screwdriver tip of a manual or powered screwdriver (not shown) that is employed to rotate and screw the bone screw body  110  into the bone. For example, the external driver configuration may be fluted or scalloped to have indentations or splines or flats similar to a hex wrench. A female screwdriver tip shaped in a complementary hexagonal shape or a Torx shape or the like can be applied over the bone screw head  110  to engage the external driver configuration. 
     The proximal bone screw neck  112  incorporates a proximal socket  114  that extends axially from the proximal end of the screw body  110  within the bone screw neck  112  and the external driver element  118 . The socket  114  may be threaded or shaped with one or more catch. 
     The separate screw head  120  is formed in a tack-like shape, for example, comprising a proximal tack head  124 , a distal prong  122  (for example), and a shaft  126  extending between the proximal tack head  124  and the distal prong  122 . The distal prong  122  and shaft  126  are shaped and dimensioned to fit into the proximal socket  114 . The distal prong  122  may engage a catch within the proximal socket  114  to resist withdrawal of the shaft  126  from the proximal socket  114 . Alternatively, the shaft  126  may be threaded along its length to be screwed into mating threads formed in the proximal socket  114  to resist withdrawal of the shaft  126  from the proximal socket  114 . The diameter of tack head  124  is selected to exceed and the diameter of the screw neck  112  and is selected to match or be smaller than the size of the mesh pore  40  of the urethral sling  30 . 
     In use, a plurality, e.g., six, of the bone screw bodies  110  are screwed into the descending pubic rami  24  and  36  so that the proximal sockets  114  are accessible. A screw head  120  and the urethral sling  30  are grasped so that the distal retainer prong  122  and shaft  126  can be inserted through a selected mesh pore  40  of the urethral sling  30  and then inserted into a proximal socket  114 . The steps are repeated with each screw head  120  until all screw heads  120  are affixed to bone screw bodies  110  to form bone screws  100 . For example, the urethral mesh  30  may be first affixed along an end thereof to bone screws  100  screwed into one of the descending pubic rami  24 ,  26  and then the other end of the urethral mesh  30  may be affixed along the other end thereof to bone screws  100  screwed into the other of the descending pubic rami  24 ,  26 . In the process, tension may be applied to the urethral mesh  30  to stretch it between the bone screws  100 . 
     The elastic strands bounding the selected mesh pore  40  bear against the reduced diameter, screw neck  112 . The urethral sling  30  is thereby entrapped, engaged, and tensioned between each screw body  110  of each bone screw  100  screwed into the descending pubic rami  24 ,  26  or other pubic bones. The urethral sling  30  may be readily detached and reattached to change sling tension as tension testing dictates. 
     In accordance with a further aspect of the invention, at least one sling retainer is provided in a kit with each bone anchor, the sling retainer having a retainer dimension exceeding a head dimension of an integral or separate anchor head and a neck engaging retainer bore. The sling retainer is adapted to be interposed between the sling and the anchor head to retain the sling against the anchor neck and to inhibit passage of the sling over the anchor head. One such sling retainer for use with a bone screw shaped generally in the manner of the bone screw  50  of  FIGS. 4A-4E  or the bone screw  100  of  FIGS. 5A-5B  to enhance the retention characteristics is depicted in  FIGS. 6A-6D . The bone screw  150  of  FIGS. 6A-6D  is generally configured like the bone screw  50  of  FIGS. 4A-4E  having a generally conical shaft or screw body  152  extending between a proximal screw head  154  to a distal screw tip, and a spiral screw thread  156  extends along the generally conical screw body  152  to a distal screw tip. The screw head  154  has an external driver configuration similar to that of screw head  54  to mate with a manual or powered screwdriver (not shown) that is employed to rotate and screw the bone screw  150  into bone. The bone screw  150  is modified to have a somewhat elongated NL of screw neck  158  than screw neck  58  of bone screw  50  to accommodate the thickness of a separate retainer  150  depicted in  FIGS. 6B-6D  or retainer  164  depicted in  FIGS. 6E-6G  or other retainers described herein. 
     Substantially the same steps are followed to screw each bone screw  150  into the right and left descending pubic rami  24  and  26  and to fit the urethral sling  30  to each bone screw neck  158  as are described above for screwing each bone screw  50  or  100  into the right and left descending pubic rami  24  and  26  and fitting the urethral sling  30  thereto. The tension of the urethral sling  30  may be tested, and the urethral sling  30  may be detached and reattached until acceptable tension is achieved. One of the sling retainer  160  or  164  is then fitted about the screw neck  158  and against the urethral sling  30  to enhance retention during chronic implantation. 
     The sling retainer  160  is preferably annular in shape, like a washer, having a central retainer port or bore  162 . The retainer dimension or diameter of the retainer  160  exceeds the head diameter HD ( FIG. 4E ) of the screw head  154 . The bore diameter of the retainer bore  162  is selected to be smaller than the head diameter HD and substantially equal or exceed the neck diameter ND. The retainer  160  is formed of an elastic, bio-compatible material that can be stretched sufficiently to expand the diameter of the retainer bore  162  to the head diameter HD so that the retainer  160  can be fitted over the screw head  154  as shown in  FIG. 6C . The retainer  160  is thereby entrapped between the screw head  154  and the urethral sling  30  as shown in  FIG. 6D . The retainer diameter of the retainer  160  and surface area of contact of the retainer  160  to the mesh strands of the urethral sling  30  enhances retention of the urethral sling  30 . 
     The sling retainer  164  is also preferably annular in shape, like a washer, having a central aperture  166 , but further having a slot  168  extending from the retainer circumference to the central aperture  166 . The outer diameter of the retainer  164  also exceeds the head diameter HD ( FIG. 4E ) of the screw head  154 . The diameter of the central aperture  166  is selected to be smaller than the head diameter HD and substantially equal or exceed the neck diameter ND. The slot end joining the central aperture  166  is narrower than the neck diameter ND. The retainer  164  is formed of an elastic, bio-compatible material that can also be stretched sufficiently to expand the slot  168  at the central aperture  166  to the neck diameter ND so that the retainer  164  can be fitted over the neck  158  as shown in  FIG. 6F . The retainer  160  is thereby entrapped between the screw head  154  and the urethral sling  30  as shown in  FIG. 6G . The diameter of the retainer  160  and surface area of contact of the retainer  160  to the mesh strands of the urethral sling  30  enhances retention of the urethral sling  30 . 
     In a still further aspect of the present invention, a kit may be provided including sets of the resilient annular retainers  160  and/or  164  that the surgeon may selectively employ as described above. It will be appreciated that the fixation of the resilient annular retainer  160  over the screw head  154  or a slotted annular retainer  164  over the screw neck  158  may be facilitated through the use of a dispenser rather than attempting to simply manually placing and pressing the retainer  160  or  164  onto the screw neck  158 . In one embodiment, the dispenser stores the required number of retainers  160  or  164 , aligns a retainer  160  or  164  with the bone screw  150 , and facilitates transfer of the retainer  160  or  164  from the dispenser onto the screw neck  158 . 
     One such exemplary retainer dispenser  180  is depicted in  FIGS. 7A and 7B  for use in dispensing an annular retainer  160  onto the screw neck  178  of a further bone screw  170 . The retainer dispenser  180  comprises an elongated dispenser shaft  182  extending between a proximal dispenser shaft end  184  and a distal dispenser shaft end  188 . The dispenser  180  provides storage of the requisite number (six in this example) of retainers  160   1 - 160   6  along an enlarged diameter, proximal shaft portion of dispenser shaft  182 . The diameter of the proximal shaft portion of dispenser shaft  182  exceeds the diameter of the retainer bore  162  sufficiently that the retainers  160   1 - 160   6  are frictionally engaged and arrayed for use along the proximal shaft portion of dispenser shaft  182 . Generally speaking, the distal dispenser shaft end  188  is brought into contact with the bone screw head  174  and into axial alignment with the axis of the bone screw  170  to enable dispensing of an annular retainer  160   1 - 160   6  onto a bone screw neck  178 . 
     The dispenser shaft distal end  188  is shaped to mate with the bone screw head  174  such that the dispenser shaft axis can be substantially axially aligned with the bone screw axis. In this example, the bone screw head  174  is shaped with a female bore  175  that the dispenser shaft distal end  188  fits into as shown in  FIG. 7B . A distal shaft portion  186  is reduced in diameter so that the most distal of the retainers  160   1 - 160   6  along the enlarged diameter, proximal shaft portion of dispenser shaft  182  can be moved from its storage point distally over the dispenser shaft  182  and then over the bone screw head  174  and onto the screw neck  178  as shown in  FIG. 7B . 
     It will be understood that the dispenser shaft distal end  188  may alternatively be shaped to engage the external driver configuration of the bone screw head  154  of bone screw  150 , whereby the female bore  175  is not necessary. 
     It should also be noted that a bone screw suture or suture pair may optionally extend from the bone screw heads  54 ,  154 ,  174  to facilitate screwing it into the descending pubic rami  24 ,  26  employing conventionally available, battery powered, bone screwdrivers. The suture is convenient for use holding the screw head to the bone screwdriver while the bone screw is being screwed into the descending pubic ramus. It is also helpful to provide the bone sutures, as shown in  FIG. 1 , extended through the urethral sling  30  to position it with respect to the bone screws prior to application of a retainer. The sutures may be tied off and trimmed after adequate tension is achieved and with fewer knots to provide redundancy, reduce suturing time, and minimize the remaining suture knot bulk. At the discretion of the surgeon, the suture length may be trimmed away entirely or tied with a simple knot and trimmed to minimize the size of the knot. 
     Thus, a bone screw  190  substantially corresponding to bone screw  150  but including a proximally extending suture  200  (a single suture or suture pair) and adapted to be employed with or without a retainer  160  or  164 , is depicted in  FIGS. 8A-8C . The bone screw  190  is generally configured like the bone screw  150  of  FIGS. 6A-6G  having a generally conical shaft or screw body  192  extending between a proximal screw head  194  to a distal screw tip, and a spiral screw thread  196  extends along the generally conical screw body  192  to the distal screw tip. The screw head  194  has an external driver configuration similar to that of screw head  54  to mate with a manual or powered screwdriver (not shown) that is employed to rotate and screw the bone screw  190  into bone. 
     In the depicted embodiment, the suture  200  is intended to be extended proximally through a hollow shaft of the battery-powered screwdriver known in the art so that suture can be used to guide the driver head into engagement with the screw head  194  so that it can rotated and does not entangle the suture  200 . As shown in  FIG. 8B , the proximal end of the suture  200  is entrapped in a bore  202  of the bone screw head  194 . Fixation of a urethral sling  30  onto a plurality of the bone screws  190  is accomplished in any of the ways described above. It will be appreciated that bone screw  190  may be used to affix a urethral sling  30  without a retainer  160  of  164  in the manner of the bone screw  50  as described above or may be used with a retainer  160  or  164  in the manner described above. 
     For example, as shown in FIG. BC, the suture  200  extends proximally and the annular retainer  160  is advanced over the suture  200 , then over the screw head  194  and onto the screw neck  198 . The suture  200  extending proximally from the proximal screw head  190  is adapted to be threaded through a mesh pore  40  or hole made through the urethral sling  30  in any of the manners described above, and the suture  200  and screw head  194  are extended through the sling mesh pore  40  or prepared hole. Sling tension testing may proceed and repositioning may occur until satisfactory sling tension is achieved. The resilient annular retainer  160  is then moved distally over the suture  200  and fitted by expansion of the retainer bore  162  to snap over the proximal screw head  194  and against the urethral sling  30  entrapped by the screw neck  198 . 
     Again, it will be appreciated that a kit may be provided including sets of the resilient annular retainers  160  and/or  164  that the surgeon may selectively employ as described above. It will be appreciated that the fixation of the resilient annular retainer  160  over the screw head  194  or a slotted annular retainer  164  over the screw neck  198  may be facilitated through the use of a dispenser rather than attempting to simply manually placing and pressing the retainer  160  or  164  onto the screw neck  198 . 
     Advantageously, the kit may be incorporated into a conventional or non-conventional powered screwdriver of the type described in the above-referenced patents to screw the bone screw  190  of  FIG. 8A  or  150  of  FIG. 6B  into pubic bone. Thus, for example, a kit comprising a retainer dispenser, e.g., a powered screwdriver  300  and at least one retainer  160  may be provided as depicted in  FIGS. 9A-9C  and may be employed to screw the bone screw  190  of  FIG. 8A  or  150  of  FIG. 6B  into pubic bone of the descending pubic rami  24 ,  26  and to dispense and apply the retainer  160  against the mesh of the urethral sling  30  of  FIGS. 2 and 3  to enhance retention of the mesh to the pubic bone. 
     As shown in  FIGS. 9A and 9B , the screwdriver  300  comprises a drive motor and battery within proximal handle  302 , a rotatable drive shaft  304  coupled to the drive motor, an on/off switch  310  for selectively powering the drive motor, and a stationary sheath  308  extending over the drive shaft  304 . When assembled as shown in  FIG. 9B , the distal screwdriver tip  306  is exposed from the distal end of the stationary sheath  308 . The distal screwdriver tip  306  is shaped to mate with the external surface of the bone screw head  194  (or  154 ) as shown in  FIG. 9C  to rotate and screw the screw threads of the bone screw  190  into the ramus  24 ,  26  when the on/off button  310  is pushed “ON”. Optionally, a shaft lumen extends continuously and proximally through the distal screwdriver tip  306 , the drive shaft  304 , the drive motor in handle  302 , and through an opening in handle  302  to accommodate the suture  200  while the bone screw  190  is rotated and screwed into the ramus  24 ,  26 . 
     In this embodiment, a set of retainers, e.g., the retainers  160   1 - 160   6  of  FIG. 7A  can be retained and stored on the stationary sheath  308  and the set or a single retainer is represented by retainer  160  in  FIGS. 9A-9C . As shown in  FIG. 9C , the most distal retainer  160  shown in broken lines can be advanced distally from its storage position over the sheath  308  and the distal screwdriver tip  306  and dispensed into the screw neck and against the mesh of the urethral sling  30  to enhance retention of the mesh to the pubic bone of ramus  24 ,  26 . 
     A further retainer dispenser  210  is depicted in  FIGS. 10A and 10B  that incorporates a breakaway sling retainer  222  (similar to sling retainer  160 ) that is attached to the dispenser  210  until the sling retainer  222  is fitted onto the bone screw neck  198  and is dispensed by a twisting motion separating the retainer  222  from the dispenser  210 . The retainer dispenser  210  can be employed to fit sling retainer  222  over a bone screw head  194  of the bone screw  190  depicted in  FIGS. 10A and 10B . Alternatively, the retainer dispenser  210  can be employed to fit sling retainer  222  over a bone screw head  124 ,  154  or  174  of the bone screws  100 ,  150  or  170 . 
     The dispenser  210  comprises an elongated hollow dispenser shaft having a shaft axis and extending between a dispenser shaft proximal end  212  and a dispenser shaft distal end  214 . In this embodiment, an internal dispenser lumen  216  extends between the dispenser shaft proximal and distal ends  212  and  214  to accommodate the suture  200  extending from bone screw  190 . A pair of resilient suspension arms  218  and  220  extend outwardly and distally of the dispenser shaft distal end  214 . The sling retainer  222  is generally annular having a central retainer bore  224  and is affixed by weak breakaway zones  228  and  230  to the respective suspension arms  218  and  220 . The diameter of the retainer bore  224  is selected to be substantially equal to or slightly larger than neck diameter ND of the bone screw  190  and less than the diameter of the screw head  194 . The sling retainer  222  is suspended substantially transverse to the shaft axis, and the retainer bore  224  may optionally be aligned with the shaft axis. 
     In use, the suture  200  is extended through the retainer bore  224  and proximally through the dispenser lumen  216 . The dispenser  220  is manually grasped and advanced distally over the suture  200  until the retainer  222  abuts the screw head  194 . The dispenser  220  is manipulated to advance and dilate the retainer bore  224  over the screw head  194  and onto the screw neck  198 . Then, the dispenser shaft distal end  214  is manually bent and twisted to break the breakaway zones  228  and  230  and free the retainer  222 . The retainer  222  then bears against the mesh of the urethral sling  30  to enhance retention of the mesh to the pubic bone of descending pubic rami  24 ,  26 . 
     A still further embodiment of a bone anchor, particularly a modified bone screw  260 , is depicted in  FIGS. 11A and 11B  that may be used with or without a retainer dispenser, e.g. the retainer dispensers  210  and  300 , or with a further retainer dispenser  240  depicted in  FIGS. 11A and 11B . The retainer dispenser  240  depicted in  FIGS. 11A and 11B  also incorporates a breakaway retainer  252  that is retained by the dispenser  240  until it is fitted onto a bone screw neck and is dispensed by a twisting motion separating the sling retainer  252  from the dispenser  240 . The retainer dispenser  240  can be employed to fit sling retainer  252  over a bone screw head  264  of the bone screw  260  as depicted in  FIGS. 11A and 11B . Alternatively, the retainer dispenser  240  can be employed to fit sling retainer  252  over a bone screw head  124 ,  154 ,  174  or  194  of the bone screws  100 ,  150 ,  170  or  190 . 
     The depicted bone screw  260  is formed with a generally conical shaft or screw body  262  extending between a proximal bone screw head  264  to a distal tip. A proximal portion of the screw body  262  has an external driver configuration to mate with the screwdriver tip of a manual or powered screwdriver (not shown) that is employed to rotate and screw the bone screw  260  into the bone. For example, the external driver configuration may be fluted or scalloped to have indentations or splines or have flats similar to a hex head that engage with female screwdriver tip shaped in a hexagonal shape or a Torx shape or the like. A spiral screw thread  266  extends along the generally conical screw body  262  between the distal screw tip and the external driver configuration. It will also be understood that the screw body  262  and the spiral screw thread  266  may take any known form employed in bone screws. 
     The modified bone screw  260  further has a generally conical shaped bone screw head  264  axially aligned with and coupled through a reduced diameter neck  268  with the screw body  262 . A suture  270  may or may not be coupled to the bone screw head  264 . The conical shaped bone screw head  264  is configured to allow advancement of a sling retainer over it and onto the screw neck  268  to engage with the mesh of the urethral sling  30  to enhance retention of the mesh to the pubic bone of descending pubic rami  24 ,  26 . 
     The dispenser  240  comprises an elongated hollow dispenser shaft having a shaft axis and extending between a dispenser shaft proximal end  242  and a dispenser shaft distal end  244 . In this embodiment, an internal dispenser lumen  246  extends between the dispenser shaft proximal and distal ends  242  and  244  to accommodate the suture  270  extending from bone screw  260  or the suture  200  extending from the bone screw  190 . A pair of resilient suspension arms  248  and  250  extend inwardly into the shaft lumen at the and distally of the shaft distal end  244 . The shaft lumen  246  extending proximally through the dispenser  260  accommodates the suture  200  extending from the bone screw head  268 . 
     The sling retainer  252  is suspended substantially transverse to the shaft axis, and the retainer bore  224  may optionally be aligned with the shaft axis. In this embodiment, the sling retainer  252  is generally annular having a central retainer bore  254  and is affixed to the dispenser shaft distal end  244  by relatively weak breakaway zones of the respective suspension arms  248  and  250 . In the depicted embodiment of retainer  252 , the central retainer bore  254  is defined by expandable annular flaps  255  that are bounded by radial slits. The diameter of the retainer bore  254  is selected, when the flaps  255  are in the depicted relaxed state, to be substantially equal to or slightly larger than neck diameter of the bone screw neck  268  and less than the diameter of the screw head  264 . The flaps  255  can deflect outward as the retainer  252  is pressed over the generally conical bone screw head  264  to thereby expand the diameter of the retainer bore  254  so that the bone screw head  264  can pass through the retainer bore  254 . 
     In use, the suture  270  is extended through the retainer bore  254  and proximally through the dispenser lumen  246 . The dispenser  240  is manually grasped and advanced distally over the suture  270  until the retainer  252  abuts the screw head  264 . The dispenser  240  is manipulated to advance and dilate the retainer bore  254  over the screw head  264  and onto the screw neck  268 . Then, the dispenser shaft distal end is manually bent and twisted to break the breakaway zones of the resilient suspension arms  248  and  250  and free the retainer  252 . The retainer  252  then bears against the mesh of the urethral sling  30  to enhance retention of the mesh to the pubic bone of descending pubic rami  24 ,  26 . 
     From the depiction of the retainer  252 , it will be understood that the retainer  160  of  FIGS. 6A-6C  may be configured to have slits extending away from the retainer bore  162  to form flaps that ease expansion of the retainer bore  162  upon application over the various embodiments of bone screw heads. 
     The above-described bone anchor embodiments illustrated in  FIGS. 4-11  have a bone screw head that extends laterally away from the bone screw neck generally through 360° rotation about the axis of the bone screw shaft or body. The anchor heads  54 ,  154 ,  174 , and  194  extend laterally from the anchor body axis to a plurality of head lobes providing a head dimension (HD) exceeding the anchor neck dimension (ND). The head lobes are spaced from one another through a 360° rotation about the axis of the anchor body providing sling engaging points and a driver engagement element adapted to be engaged to drive the bone fixation mechanism into bone. 
     The sling retainer bores are dimensioned to fit over the bone screw head to engage the bone screw neck or to be extended laterally around the bone screw neck to fit between the bone screw head and the urethral sling. It will be understood that the present invention may be practiced employing bone anchors having bone anchor heads that do not necessarily extend laterally away from the bone screw neck by a generally through 360° rotation about the axis of the bone screw shaft or body. Alternative configurations of the bone screw heads and the sling retainers are illustrated by the following embodiments. 
     A further embodiment of a bone screw  320  and a sling retainer  335  adapted to engage and retain the mesh of the urethral sling  30  of  FIGS. 2 and 3  is depicted in  FIGS. 12A-12E . The bone screw  320  is formed with a generally conical shaft or screw body  326  extending between a proximal bone screw head  330  to a distal tip. A spiral screw thread  326  extends along the generally conical screw body between the distal screw tip and the external driver configuration or element  322 . It will also be understood that the screw body and the spiral screw thread  326  may take any known form employed in bone screws. 
     A proximal portion or shoulder of the screw body has an external driver configuration or element  322  to mate with the screwdriver tip of a manual or powered screwdriver (not shown) that is employed to rotate and screw the bone screw  320  into the bone. For example, the external driver configuration or element  322  may be fluted or scalloped to have indentations or splines or flats similar to a hex wrench. A female screwdriver tip shaped in a complementary hexagonal shape or a Torx shape or the like can be applied over the bone screw head  330  to engage the external driver configuration. 
     The bone screw head  330  is generally ring-shaped and is coupled through a reduced diameter neck  328  with the screw body. The ring-shaped bone screw head  330  is configured with a laterally or transversely extending head bore  332  to receive a sling retainer, e.g., the H-shaped retainer  335  shown in  FIGS. 12B and 12C  or the C-shaped retainer  345  shown in  FIGS. 12D and 12E . 
     In use, the bone screw  320  is affixed to the distal screwdriver tip, via the external driver element  322  of the screw body, of a manual or battery powered screwdriver, and the spiral thread  326  is screwed into the pubic bone of a descending pubic ramus  24 ,  26  at a location as depicted in  FIG. 1 , for example, leaving the ring-shaped bone screw head  330  exposed. The urethral sling  30  is applied against the ring-shaped bone screw head  330  so that it extends through a mesh pore  40  as shown in  FIGS. 12C and 12E . It will be understood that the strands surrounding the mesh pore  40  may be stretched to accommodate passage of the ring-shaped bone screw head  330  through the mesh pore  40 . 
     The H-shaped retainer  335  depicted in  FIGS. 12B and 12C  is formed of a generally resilient, bio-compatible material that has an elongated retainer body  336  joined at one body end to arms  338  and  340  and at the other body end to arms  342  and  344 . At least the arms  342  and  344  or one of the arms  342  or  344  can be bent into generally parallel alignment with the retainer body  336  as shown in  FIG. 12B , for example, to be inserted through the transversely extending head bore  332 . The H-shape of retainer  335  is restored when the arms  342  and/or  344  are released so that the arms  338 ,  340 ,  342  and  344  to extend against the strands forming the mesh of the urethral sling  30 . The H-shaped retainer  335  thereby bears against the mesh of the urethral sling  30  to enhance retention of the mesh to the pubic bone of descending pubic rami  24 ,  26 . 
     The C-shaped retainer  345  depicted in  FIGS. 12D and 12E  is formed of a generally resilient, bio-compatible material that has a C-shaped retainer body  346  joined at a fixed body end to an arm fixed end of a resilient arm  347  that has an arm free end extending toward the body free end of retainer body  346 . The retainer body  346  and arm  347  bound a retainer bore  348 . The resilient arm  347  can be bent along its length into retainer bore  348  to separate the arm free end from the retainer body free end by a gap sufficient to pass the ring-shaped bone screw head  330  therethrough. The depicted shape of the retainer arm  347  is then restored coupling the C-shaped retainer  345  to the bone screw  320 . Thus, the C-shaped retainer  345  may be affixed to the bone screw  320  to extend through the bone screw head bore  332  as shown in  FIG. 12E  and entrap the urethral sling  30  between the ring-shaped bone screw head  330  and the exterior surface of the pubic bone. The C-shaped retainer  345  thereby bears against the mesh of the urethral sling  30  to enhance retention of the mesh to the pubic bone of descending pubic rami  24 ,  26 . 
     The H-shaped retainer  335  and the C-shaped retainer  345  that extend laterally to the axis of the bone screw  320  when affixed as shown in  FIGS. 12C and 12E  are dimensioned in length to exceed the dimension of the sling opening, e.g., the sling pore  40 , and to entrap and engage the urethral sling  30 . 
     It will be understood that any of the above-described sling retainers may be substituted for the H-shaped retainer  335  or the C-shaped retainer  345 . For example, sling retainer  164  depicted in  FIGS. 6E-6G  may be inserted laterally as depicted in  FIG. 6F  between the bone screw head  330  engage the neck  328  and to bear against the urethral sling  30  in the manner depicted in  FIG. 6G . Alternatively, a sling retainer  160  depicted in  FIGS. 6B-6D  may be inserted over the bone screw head  330  to engage the bone screw neck  328  and to bear against the urethral sling  30  in the manner depicted in  FIG. 6D . Or the sling retainer dispensers  180  ( FIGS. 7A-7B ),  210  ( FIGS. 10A-10B ),  240  ( FIGS. 11A-11B ) or  300  ( FIGS. 9A-9   c ) may be employed to apply a respective sling retainer  160   1 - 160   6 ,  222 ,  252 ,  160  in engagement about the bone screw neck  328 . 
     A still further embodiment of a bone screw  350  formed with a bone screw head  355  adapted to engage and retain the mesh of the urethral sling  30  of  FIGS. 2 and 3  with or without a sling retainer is depicted in  FIGS. 13A and 13B . The bone screw  350  is formed with a generally conical shaft or screw body extending between a proximal bone screw head  355  to a distal tip. A spiral screw thread  356  extends along the generally conical screw body between the distal screw tip and the external driver configuration. It will also be understood that the screw body and the spiral screw thread  356  may take any known form employed in bone screws. A proximal portion of the screw body has an external driver configuration or element  352  to mate with the screwdriver tip of a manual or powered screwdriver (not shown) that is employed to rotate and screw the bone screw  350  into the bone as described above with respect to  FIGS. 12A-12E . 
     The modified bone screw  350  further has a generally hook-shaped bone screw head  355  that may be formed of at least one hook comprising a hook shaft and one laterally extending tine, barb or hook, wherein the lateral extension is at an angle other than transverse or 90° to the anchor body axis. In this depicted embodiment, the bone screw head  355  comprises a first hook shaft  358  and hook  360  and a second hook shaft  362  and hook  364 . The hook shafts and hooks may be formed of a biocompatible metal or plastic material where the hook shaft distal ends are entrapped or otherwise fixed within or to the screw body  358 . The hook shafts  358  and  362  jointly function as a bone screw neck, and the hooks  360  and  364  function as the bone screw head  355 . It will be understood that the bone screw head  355  may comprise only one or more than two such hooks extending laterally from a single or plural hook shafts. 
     In use, the bone screw  350  is affixed to the distal screwdriver tip, via the external driver configuration or element  352  of the screw body, of a manual or battery powered screwdriver, and the spiral thread  356  is screwed into the pubic bone of a descending pubic ramus  24 ,  26  at a location as depicted in  FIG. 1 , for example, leaving the hook shafts and hooks exposed. The urethral sling  30  is applied against the hooks and hooks so that they extend through the same or separate mesh pores  40  as shown in  FIG. 13B . It will be understood that the strands surrounding the mesh pore  40  may be stretched to accommodate passage of the hooks  360  and  364  forming bone screw head  355  through the mesh pore  40 . 
     As illustrated, the strands of the mesh of the urethral sling  30  are caught beneath the laterally extending hooks  360 ,  364  and bear against the shafts  358  and  362 , particularly as tension is applied laterally to the strands. The bone screw head  355  thereby engages with the mesh of the urethral sling  30  to enhance retention of the mesh to the pubic bone of descending pubic rami  24 ,  26 . 
     It will be understood that a sling retainer, e.g., sling retainer  164  depicted in  FIGS. 6E-6G  may be inserted laterally as depicted in  FIG. 6F  between the laterally extending hooks  360 ,  364  to engage the shafts  358  and  362  and to bear against the urethral sling  30  in the manner depicted in  FIG. 6G . Alternatively, a sling retainer  160  depicted in  FIGS. 6B-6D  may be inserted over the laterally extending hooks  360 ,  364  to engage the shafts  358  and  362  and to bear against the urethral sling  30  in the manner depicted in  FIG. 6D . Or the sling retainer dispensers  180  ( FIGS. 7A-7B ),  210  ( FIGS. 10A-10B ),  240  ( FIGS. 11A-11B ) or  300  ( FIGS. 9A-9C ) may be employed to apply a respective sling retainer  160   1 - 160   6 ,  222 ,  252 ,  160  in engagement about the bone screw neck comprising the shafts  358  and  362 . 
     Yet another embodiment of a bone screw  370  formed with a bone screw head  375  adapted to engage and retain the mesh of the urethral sling  30  of  FIGS. 2 and 3  with or without the use of a sling retainer is depicted in  FIGS. 14A and 14B . The bone screw  370  is formed with a generally conical shaft or screw body extending between a proximal bone screw head  375  to a distal tip. A spiral screw thread  376  extends along the generally conical screw body between the distal screw tip and the external driver configuration. It will also be understood that the screw body and the spiral screw thread  376  may take any known form employed in bone screws. A proximal portion of the screw body has an external driver configuration or element  372  to mate with the screwdriver tip of a manual or powered screwdriver (not shown) that is employed to rotate and screw the bone screw  370  into the bone in the manner described above with respect to  FIGS. 12A-12E . 
     A bone screw neck  378  extends proximally and substantially axially from the bone screw body to a free end  380 . The modified bone screw  370  further has a generally T-shaped or arrow-shaped bone screw head  375  that is formed at the proximal, free end  380  of the bone screw neck  378 . Laterally and generally distally extending tines or barbs or hooks  382  and  384  extend from free end  380  to engage the strands of the mesh of the urethral sling  30 . The bone screw neck  378  and the hooks  382  and  384  may be formed integrally at free end  380  and of a biocompatible metal or plastic material where the distal end of the neck  378  is entrapped or otherwise fixed within or to the screw body. 
     In use, the bone screw  370  is affixed to the distal screwdriver tip, via the external driver configuration or element  372  of the screw body, of a manual or battery powered screwdriver, and the spiral thread  376  is screwed into the pubic bone of a descending pubic ramus  24 ,  26  at a location as depicted in  FIG. 1 , for example, leaving the neck  378  and hooks  382 ,  384  exposed. The urethral sling  30  is applied against the bone screw head  375  so that it extends through a mesh pore  40  so that the urethral sling  30  is disposed between the laterally extending hooks  382 ,  384  and the surface of the pubic bone as shown in  FIG. 14B . It will be understood that the strands surrounding the mesh pore  40  may be stretched to accommodate passage of the bone screw head  375  through the mesh pore  40 . 
     The strands of the mesh of the urethral sling  30  are then caught beneath the laterally extending hooks  382 ,  384  and bearing against the neck  378 , particularly as tension is applied laterally to the strands. The bone screw head  375  thereby engages with the mesh of the urethral sling  30  to enhance retention of the mesh to the pubic bone of descending pubic rami  24 ,  26 . 
     It will be understood that a sling retainer, e.g., sling retainer  164  depicted in  FIGS. 6E-6G  may be inserted laterally as depicted in  FIG. 6F  between the laterally extending hooks  382 ,  384  to engage the neck  378  and to bear against the urethral sling  30  in the manner depicted in  FIG. 6G . Alternatively, a sling retainer  160  depicted in  FIGS. 6B-6D  may be inserted over the laterally extending hooks  382 ,  384  to engage the bone screw neck  378  and to bear against the urethral sling  30  in the manner depicted in  FIG. 6D . Or the sling retainer dispensers  180  ( FIGS. 7A-7B ),  210  ( FIGS. 10A-10B ),  240  ( FIGS. 11A-11B ) or  300  ( FIGS. 9A-9   c ) may be employed to apply a respective sling retainer  160   1 - 160   6 ,  222 ,  252 ,  160  in engagement about the bone screw neck  378 . 
     Still another embodiment of a bone screw  390  formed with a bone screw spiral head  400  adapted to engage and retain the mesh of the urethral sling  30  of  FIGS. 2 and 3  with or without a sling retainer is depicted in  FIGS. 15A and 15B . The bone screw  390  is formed with a generally conical shaft or screw body  392  extending between a proximal bone screw head  375  to a distal tip. A spiral screw thread  396  extends along the generally conical screw body  392  between the distal screw tip and the external driver configuration. It will also be understood that the screw body  392  and the spiral screw thread  396  may take any known form employed in bone screws. A proximal portion of the screw body  392  has an external driver configuration to mate with the screwdriver tip of a manual or powered screwdriver (not shown) that is employed to rotate and screw the bone screw  390  into the bone in the manner described above with respect to  FIGS. 12A-12E . 
     A bone screw neck  398  extends proximally and substantially axially from the bone screw body  392 . The modified bone screw  390  further has a generally spiral-shaped bone screw head  400  that is formed at the proximal, free end of the bone screw neck  398 . A laterally and generally distally extending spiral  402  of at least one turn extends from the end of the bone screw neck  398  to a spiral free end. The spiral  400  functions as a spiral catch engaging the strands of the mesh of the urethral sling  30 . The bone screw neck  398  and the spiral  402  may be formed integrally and of a biocompatible metal or plastic material where the distal end of the neck  398  is entrapped or otherwise fixed within or to the screw body  392 . 
     In use, the bone screw  390  is affixed to the distal screwdriver tip, via the external driver configuration of the screw body  392 , of a manual or battery powered screwdriver, and the spiral thread  396  is screwed into the pubic bone of a descending pubic ramus  24 ,  26  at a location as depicted in  FIG. 1 , for example, leaving the neck  398  and spiral  402  exposed. The urethral sling  30  is applied against the bone screw head  400  so that the spiral  402  extends through a mesh pore  40  and the urethral sling  30  is disposed between the laterally extending turn(s) of the spiral  402  and the surface of the pubic bone as shown in  FIG. 15B . It will be understood that the strands surrounding the mesh pore  40  may be stretched to accommodate passage of the spiral  402  through the mesh pore  40 . 
     The strands of the mesh of the urethral sling  30  are then caught beneath the laterally extending spiral turn(s) of spiral  402  and bearing against the neck  398 , particularly as tension is applied laterally to the strands. The bone screw head  400  thereby engages with the mesh of the urethral sling  30  to enhance retention of the mesh to the pubic bone of descending pubic rami  24 ,  26 . 
     It will be understood that a sling retainer, e.g., sling retainer  164  depicted in  FIGS. 6E-6G  may be inserted laterally as depicted in  FIG. 6F  between the laterally extending turn(s) of the spiral  402  to engage the neck  398  and to bear against the urethral sling  30  in the manner depicted in  FIG. 6G . Alternatively, the free end of the spiral  402  may be inserted through the retainer bore  163  of the sling retainer  160  depicted in  FIGS. 6B-6D  so that the sling retainer  160  may be advanced over the laterally extending turn(s) of the spiral  402  to engage the neck  398  and to bear against the urethral sling  30  in the manner depicted in  FIG. 6D .