Materials for Reconstructive Gynecologic Surgery
Mary Pat Fitzgerald and Linda Brubaker
Table Of Contents
Mary Pat Fitzgerald, MD
Linda Brubaker, MD
ENDOGENOUS TISSUES FOR RECONSTRUCTIVE SURGERY|
DONOR BIOMATERIALS (ALLOGRAFTS AND XENOGRAFTS)
SYNTHETIC GRAFT MATERIALS
Reconstructive gynecologic surgeons face daily decisions regarding surgical materials. There is no currently available ideal reconstructive surgical material. Such a material would be biocompatible, appropriately strong and durable, cost-efficient, and easy to use. This chapter provides a broad overview of the properties and clinical performance of currently available reconstructive materials in gynecologic surgery. The properties of individual sutures are not reviewed here.
|ENDOGENOUS TISSUES FOR RECONSTRUCTIVE SURGERY|
As illustrated in Table 1,1,2,3,4,5,6,7,8 all honest clinical series reporting repair of pelvic organ prolapse show (1) some outright failures and (2) deterioration of initially good outcomes over time. Such clinical observations have encouraged surgeons to enhance their outcomes by supplementing their repairs with exogenous materials.
The logical reconstructive materials to consider are the patient’s own tissues. For many years, gynecologic surgeons have relied on a variety of endogenous materials, including uterosacral ligaments, pelvic fascia, skin, muscle, and locally available connective tissue. These tissues may be used in their current location (e.g., uterosacral ligament suspension of vaginal apex) or moved to a new location for an alternative use (rectus fascia for suburethral sling). These materials are biocompatible and easy to use. The scientific evidence for their long-term durability varies. There are no randomized clinical trials comparing endogenous sources with other materials for reconstructive gynecologic surgery.
The uterosacral ligaments are probably the most used endogenous material for vaginal suspension. Every hysterectomy and many posthysterectomy vaginal support techniques rely on these native tissues. Several authors have studied the histologic components of this tissue, which is found to be composed of elastic, collagen, and smooth muscle fibers with scattered blood vessels.9 The term uterosacral ligament is a misnomer because these are not “ligaments” in any traditional sense given their composition of irregular connective tissue and abundant smooth muscle with its attendant autonomic nerve supply. Observant surgeons recognize how fleeting their form is when they are cut at the time of surgery. Their ligamentous appearance is secondary only to the anatomic tension of their environment. Surgeons selectively acknowledge the innervation of the uterosacral ligaments. Most commonly, these structures are transected and sewn without thought to the neural consequences. Certain surgical procedures use the opposite approach. During procedures to ablate midline pelvic pain, the uterosacral ligaments are transected or destroyed without regard to long-term vaginal support.
Vaginal fascia has been discussed in gynecologic operating rooms for more than 100 years, typically during anterior colporrhaphy. The histologic components of this material have been studied by Weber and Walters,10 who examined full-thickness sections of the bladder and vagina from autopsy specimens. Histologic examination confirmed that there is no vaginal “fascia”; rather the tissue between the vaginal mucosa and the bladder muscularis consists only of vaginal lamina propria and vaginal muscularis (Fig. 1). This layer is plicated during traditional anterior colporrhaphy. The histologic components of this tissue may help explain the relatively low anatomic success rates of anterior colporrhaphy. A layer that contains bladder adventitia and muscularis does not have the optimal biomechanical properties for long-term, durable anterior vaginal wall support. At the very least, this material is different from traditional fascia (rectus or fascia lata) and should not be considered to have similar biomechanical properties.
Repair of the posterior vaginal wall is a commonly performed gynecologic procedure. The most common material for this repair is the native rectovaginal fascia. There are no large case series that report the sufficiency of this tissue for its intended purpose. Experts commonly discuss the untoward side effects of posterior vaginal surgery without focus on anatomic recurrence of poor support. The exact histologic nature of the rectovaginal fascia has been the subject of some debate. One study found that the rectovaginal fascia consisted mainly of collagenous fibers11 and did not contain muscle cells (Fig. 2). In contrast, Milley and Nichols12 mentioned the presence of smooth muscle cells within the fascia. It may be that those muscle fibers originate from the external longitudinal muscle layer of the rectum.13 All authors agree that nerves of the hypogastric plexus run in the ventrolateral junction of the fascia with rectum. Surgical techniques that rely on this layer for posterior wall support conceivably could disable the delicate neuromusclar function of the rectovaginal axis. Techniques that document good efficacy with less dissection or plication5,6,14 may be preferable to traditional full-length colporrhaphy techniques.15,16
The vaginal wall is also known to be a pliable, readily available surgical tissue. This tissue has been used for patch slings and vaginal repairs. It is unsuitable for these purposes because it does not have the biomechanical properties to resist stretching.17 This fact is easily appreciated by anyone who has witnessed vaginal birth during which the vaginal skin widely dilates to accommodate the emerging fetus. Similarly, skin throughout the body has phenomenal properties of stretch, which makes it unsuitable for long-term support.
Autologous rectus fascia seems to be an ideal material for fascial reinforcement. This tissue is used commonly for suburethral sling and occasionally is used for sacrocolpopexy. Rectus fascia is biocompatible, strong, and appropriately pliable. Also it is readily available, although the amount harvested is directly related to the risk of incisional hernia. Despite its widespread use in suburethral slings and sacrocolpopexy, the rate of failure of this material is not well known. The surgeon would want this material to remodel to gain strength and appropriate vascularity. FitzGerald and coworkers18 reported on the histologic appearance of rectus fascia used for suburethral slings and found that after implantation there was fibroblast proliferation, neovascularization, and remodeling of the fascia graft. Some linear orientation of connective tissue and fibroblasts occurred, probably along the lines of force on the graft (Fig. 3). A randomized trial comparing materials in this area is needed.
Another source of endogenous fascia is fascia lata, typically harvested through a lateral incision in the thigh. This material is strong, durable, and readily available. One report of long-term problems after fascia lata harvest suggests caution, especially with increasing age. Walters and associates19 found that among 55 patients 2 years after fascia lata harvest, 25 (46%) had subjective complaints, including discomfort, weakness, lateral thigh bulge, or unacceptable incisional cosmesis. The histologic fate of fascia lata after implantation has not been reported.
There are additional, more experimental native tissues being considered for surgical use. Bioengineering and cell culture techniques have used novel techniques to harvest material from the patient, expand and enhance the tissue, and replace it in a clinically useful manner. Such tissue techniques include culture of muscle cells,20 ear chondroblasts,21 and entire bladder wall.22 Although these are not currently ready for routine clinical use, this area of investigation is expanding rapidly.
|DONOR BIOMATERIALS (ALLOGRAFTS AND XENOGRAFTS)|
Clinical failures have tempted surgeons to consider adjunctive or alternative materials. The source of biologic materials is typically cadavers or animals. Although the use of cadaver tissue sources per se is not new, harvesting and processing fascia for gynecologic reconstruction is a more recent development. These human cadaver materials have an increased likelihood of biocompatibility, although there is some concern about immunogenicity and disease transmission.
Cadaver fascia is supplied commercially, typically in association with a tissue bank. Commercial processing of the native fascia varies significantly, and the steps involved are often confidential. The goals of processing include sterilization (bacterial and viral) and removal of immunogenic cellular components. Clinical case series are inconclusive regarding the use of cadaver fascia for gynecologic reconstruction. This material saves time and morbidity of harvesting. FitzGerald and associates23 reported concerns, however, about excess failure rates compared with historical rectus fascia controls in an early case series. With continued follow-up, a failure rate of 81% was reported for donor fascia sacrocolpopexies and of 52% for donor fascia suburethral slings.24 A volley of case series has reported successes and failures, suggesting that specific steps in the processing and preparation of the tissue may be an important factor. One case series mentioned fascia allograft erosion as a relatively frequent complication of suburethral sling and sacrocolpopexy procedures using this material.25 Table 2 is a summary of current case series and highlights the preparation methods and method of reporting success rates.24,26,27,28,29,30,31,32,33,34 In favorable reports, there is a paucity of objective outcome data.
The use of human dura mater allografts is limited to historical interest because of concerns about transmission of slow-virus neurologic diseases. These concerns have limited the use of this material, although there has never been a report of viral disease transmission from fascia transplantation in gynecologic surgery.
Several suppliers now market processed human cadaver skin as a material for reconstructive surgery. Cadaver skin may be processed to preserve the acellular dermal matrix with the intent of enhancing repopulation by endogenous host cells. These materials are approved by the Food and Drug Administration for dermal replacement but have not been tested or proved for reconstructive gynecologic surgery. Cadaver skin seems to be a viable technology and is likely to be a worthwhile source of tissue, although its exact role has yet to be established. Pessimists expect this line of investigation to produce tissue with biomechanical properties similar to skin, which would not be sufficient for prolapse repair. Marketing materials promise the tissue is “quickly revascularized and repopulated with cell populations of the patient’s own tissues.” Optimists believe that cellular ingrowth would result in enhanced strength suitable for reconstructive efforts. Case series are being reported before testing of efficacy in randomized clinical trials (Table 3).35,36,37,38,39,40 Nonhuman sources for dermal tissue also have been investigated. Processed porcine skin has been implanted without the benefit of randomized clinical trials. Case reports and patient series offer only anecdotal outcome data (see Table 3).35,36,37,38,39,40 Given the porcine source, religious prohibitions limit the use of this material in some patients.
* Derived from selected abstracts.
Similarly, intestinal submucosa has been obtained from canine and porcine sources. Nonhuman experiments showed that the tissue “becomes completely incorporated at 4 weeks.”41 Although this finding superficially suggests biocompatability, it also may represent efficient biodegradation. It is likely that successful tissue grafts undergo some degradation, but it seems essential that remodeling and reconstruction occur before complete tissue loss. As with other materials, clinical efficacy has not been well documented apart from published abstracts (see Table 3).35,36,37,38,39,40
|SYNTHETIC GRAFT MATERIALS|
Native tissues have tremendous advantages and should be used whenever they are likely to accomplish the surgical reconstruction goals. As all surgeons are aware, however, the strength of native tissues can be insufficient. It is tempting to substitute stronger, more durable materials to enhance outcomes. One high-quality randomized trial compared inguinal hernia repair with synthetic mesh with careful repair of endogenous fascia using permanent sutures.42 There were high recurrence rates in both groups but an excess recurrence rate when sutures only were used without additional mesh (sutures 43% versus mesh 24%). This study also compared these materials for repeat hernia repair. The difference was more striking with a 58% recurrence for sutures only versus 20% with mesh. Even healthy endogenous materials may have insufficient biomechanical properties to compensate for abnormal physiology.
Reconstruction has long depended on synthetic materials, and a large variety of synthetic materials are available for use by gynecologic surgeons. The ideal surgical mesh would be chemically inert, biologically inactive, strong, flexible, convenient, and cheap—this ideal mesh currently does not exist. Available meshes differ as follows:
To date, there is no randomized trial showing the superiority of synthetic materials for any aspect of gynecologic reconstruction, and no particular material has proved superior to any other. There is no study (analogous to the hernia study) that shows which patient group benefits from the use of synthetic mesh. Surgeons must develop their own philosophy about synthetic materials based on their own clinical outcomes (efficacy and complications), costs, and preferred route of surgery.
During vaginal surgery, most surgeons are reluctant to place mesh for supportive repair of vaginal walls, citing many anecdotal reports of erosion and rejection secondary to potential contamination by vaginal organisms. Placement of synthetic sling materials through the bacteria-laden vagina has seen several rises and falls in popularity. Young and colleagues46 reported 5-year success with Mersilene slings. A persistent but acceptable materials problem rate is reported. Newer sling developments attempt to shield the synthetic sling from the bacterial contamination of the vagina. Reliable long-term data regarding the fate of this material for this indication are not yet available for this technique. Synthetic meshes are used widely for sacrocolpopexy, despite a persistent rate of foreign body erosion and rejection that occasionally requires reoperation.
Absorbable meshes are poorly suited for long-term reconstruction and are not discussed further in this chapter. The permanent meshes currently available in the United States are briefly considered in alphabetical order by chemical composition (Table 4).
Mesh preparation chemical polymers are manufactured into filaments that create the individual fibers (monofilament) or yarns (multifilament). These fibers or yarns ultimately are woven in to mesh material that is unique to each brand-name mesh. Polypropylene is used to created Prolene, Marlex, and Surgipro meshes. Prolene is also a monofilament mesh with macropores. In its typical mesh formation, it is stiff, although there is additional flexibility in its preparation for use as a transvaginal tape. This highlights the difference between the chemical composition of the fiber itself and the gross properties when those fibers have additional processing and gross physical arrangement. Marlex is stiff, macroporous mesh with irregular pore sizes. It is probably suited poorly for placement on flexible body surfaces, such as the vagina.
Polyethylene terephthalate is the material that is woven to compose Mersilene mesh. Typically this mesh is prepared in a hexagonal weave with the use of multifiber filaments. It is a macroporous mesh with directionality that can be shown easily by pulling the mesh by its width versus its length. This gross characteristic is important in determining proper orientation to limit mesh stretch after reconstructive surgery.
Expanded polytetrafluoroethylene polymers are used to form a Gore-Tex mesh. Because there is no weaving involved, this mesh has a smaller pore size than either Mersilene or Prolene. This small pore size may contribute to the fact that fibrocollagenous infiltration of Gore-Tex mesh does not occur after implantation, and minimal inflammatory response to the mesh occurs.47,48
There is a negative side to the use of synthetic meshes in the pelvis. Although mesh is believed to augment surgical success rates, complications related to rejection and erosions are significant. In the course of 40 years of synthetic use, erosions into the urinary tract, bowel (large and small), and vagina have been reported (Table 5).46,49,50,51,52,53,54 Symptoms of mesh erosion typically include a persistent vaginal discharge that may be blood-tinged at times. More commonly, mesh exposure is detected when the patient is asymptomatic. One case report details asymptomatic rectal erosion and ultimate graft passage without sequelae (Fig. 5). Early efforts at full extirpation are probably overzealous and should be avoided. Expert opinion suggests that in the absence of sinister symptoms, early mesh erosions can be managed conservatively with periodic observation. A few surgeons have reported techniques for management of mesh complications,51,55 including transvaginal revision, transvaginal removal, laparotomy, and laparoscopy with removal.
TVT, tension-free vaginal tape.
Graft complications can occur many years after placement. When a mature graft appears, expert opinion suggests that it is unlikely that trimming visible graft would result in a long-term solution. It is rarely necessary, however, to remove every remnant of graft from delicate areas, such as the presacral space, to resolve symptoms associated with erosion.
The patient may ask about her risk of prolapse recurrence when the graft is removed. The data are scant, although experts believe that the inflammatory reaction related to the graft rejection and erosion seems to take the place of the graft, and repeat reconstruction is rarely necessary.
Occasionally a patient forgets that she has had mesh placed during her surgery. When that mesh is detected with an imaging modality, exploratory surgery is often recommended. Typically there is an oncologic concern of malignancy in the pelvis, most commonly after sacrocolpopexy. The consultation of a reconstructive pelvic surgeon can save unnecessary laparotomy.
There are general principals guiding the use of synthetics in reconstructive gynecology. It is prudent to avoid synthetics when viable alternatives are available. If synthetics are deemed appropriate, it is wise to limit the amount of graft used and ensure that the materials of the surgery are balanced (i.e., permanent materials for mesh and suture rather than a materials mismatch, such as permanent mesh with a rapidly absorbable suture).
Isolated reports of medical concerns with gynecologic mesh placement have appeared in the rheumatologic literature. One case report suggested a possible link between exacerbations of rheumatologic conditions and the use of synthetic mesh.56
Metal tacks, staples, and other fixation devices are available, but these are rarely needed given the strength and durability of less troublesome materials. Such metallic items fare poorly in the dynamic ecosystem of the pelvis, where the tissues require some mobility and flexibility. Case reports abound of metal present in unauthorized pelvic viscera, including the vagina, bladder, and bowel (Fig. 6),57 and use of bone anchors to anchor suburethral slings has been associated with pubic osteomyelitis.58
Knowledge of available surgical materials in reconstructive gynecologic surgery is important for surgeons and patients. Wise choices facilitate and enhance reconstructive surgery. New materials or technology that has not been scrutinized in appropriate clinical trials risks excess failure rates. Such trials should be relevant to the specific clinical situation and not generalize results from animal studies or nongynecologic human studies, such as orthopedics or dental surgery. Surgeons play an important role in requiring appropriate clinical trials before bringing new surgical materials into the operating room. Finally, it is important that patients be informed about materials that are to be used in their reconstruction.
8. Shull BL, et al: Preoperative and postoperative analysis of site-specific pelvic support defects in 81 women treated with sacrospinous ligament suspension and pelvic reconstruction. Am J Obstet Gynecol 166:1764, 1992
25. Kammerer-Doak DN, Roger RG, Bellar B: Vaginal erosion of cadaveric fascia lata following abdominal sacrocolpopexy and suburethral sling urethropexy. Int Urogyn J Pelvic Floor Dysfunct 13:106, 2002
35. Dambros M, et al: Suprapubic pubovaginal sling using the porcine small intestine submucosa (SIS): A promising minimally invasive alternative for urinary stress incontinence. Int Urogyn J Pelvic Floor Dysfunct 12(suppl 3):S13, 2001
36. Arunkalaivanan AS, Barrington JW: Comparison of procine pubovaginal sling (Pelvicol) vs Tension free vaginal tape (TVT) in the surgical management of stress intoneincne. Int Urogyn J Pelvic Floor Dysfunct 12(suppl 3):S21, 2001
52. Barbalias GA, Liatsikos EN, Anthanasopoulos A: Gore-Tex sling urethral suspension in Type III female uriniary incontinence: Clinical results and urodynamic changes. Int Urogyn J Pelvic Floor Dysfunct 8:344, 1997