SYNTHETIC MESH AND XENOGENIC GRAFTS
JIM W. ROSS, MD, PhD
The recurrence of ventral abdominal or inguinal hernias has been reported to be 16% to 25% with “classical” hernia repairs, demonstrating that weakened in situ tissue used in these repairs has a poor long-term outcome. Today, these same hernia repairs have recurrences of less than 1% to 4% . This dramatic improvement in successful long-term outcome is due to extensive use of tissue replacement and improvements in tissue substitution engineering. The most common tissue replacement sources include synthetic and biological materials. The use of synthetic mesh and xenogenic grafts in pelvic floor reconstructive surgery is extensive and will be reviewed here.
Synthetic Mesh. Synthetic mesh can be either a mono- or polyfilament weave (polyethylene, polypropylene, polytetrafluoroethylene). These materials have high-tensile strength, are long lasting, inert, nontoxic, and lack antigenicity. They can be engineered for mechanical mismatching to surrounding tissue, such that a stiff woven polypropylene mesh can promote intensive tissue ingrowth and develop intense scarification. This engineering design can be advantageous when high load-bearing is necessary. Polypropylene has been used extensively in general surgical repair of inguinal and abdominal wall hernias . In gynecologic laparoscopy, it has been used for mesh-staple colposuspension [3,4] and for sacrocolpopexy .
A 5-year long-term success rate of 91% in 51 patients has been reported for laparoscopic sacrocolpopexies , which is comparable to that in studies utilizing an open abdominal approach [7-10]. Polypropylene mesh (Prolene, Ethicon, Inc., Sommerville, NJ) was used in this laparoscopic study . Erosion has been reported with most synthetic materials, and 2 patients (4%) had vaginal erosion of the mesh, which is comparable to that in other reports (3% to 7%). One patient responded to trimming of the mesh and nightly estrogen vaginal cream. The second patient required trimming of the mesh and advancement of vaginal mucosa over the erosion site. The stiffness of polypropylene mesh plays a role in erosion, especially when attached to postmenopausal thinned out atrophic vaginal mucosa. We routinely amputate the proximal vaginal hernia sac down to the level of the ischial spines in severe prolapse. At this level, the endopelvic fascia (EPF) is more substantial for mesh attachment. Mesh stiffness can lead to increased rejection, fistula formation, encapsulated scar, erosion, pain, and nonfunctional end organs. One patient (work in progress) treated with a sacral colpoperniopexy had perineal and vaginal mesh erosion, which required removal of the mesh from the vaginal apex to the perineal body. Polypropylene with a softer weave is now available and should decrease erosion potential.
The newer multifilament polyesters now available are soft and their macroporosity results in less intense scarring and encapsulation. Polyesters have the same tensile strength as polypropylene and are much easier to work with laparoscopically because of their increased pliability. These polyesters appear to cut down on possible erosion and sinus tract formation, which are serious complications of sacral colpoperineopexies utilizing polypropylene . Colpoperineopexy is the procedure of choice for descending perineum syndrome, frequently present with severe apical vault prolapse. In this repair, mesh is sutured to the perineal body, the posterior vaginal wall, and to the sacral promontory, effectively replacing the rectal vaginal septum and uterosacral ligaments. Attachment to the entire length of the posterior vaginal wall requires repair material that is soft, pliable, strong, and does not cause encapsulation. Intense scarification could lead to a nonfunctional vagina. We have a study in progress testing wide-weave polyesters with good early outcomes.
Xenogenic Grafts. The most common biological sources for tissue grafting are syngeneic, allogeneic, or xenogeneic in origin. Most recently, porcine dermis and small intestine submucosa (SIS) have been used extensively in pelvic floor reconstruction, especially posterior vaginal wall repair. Most studies utilize site-specific repairs, in conjunction with porcine dermal grafts, for a posterior vaginal wall defect [12,13]. We have an ongoing study of 57 women followed for greater than 6 months with Stage 2 or greater posterior vaginal wall defects (Pelvic Organ Prolapse Quantification System—POP-Q) . Porcine dermis (n=33) or SIS (n=24) xenogeneic grafts were used for all repairs. These grafts were fixed to the uterosacral ligaments proximally, the rectovaginal septum arcus attachments laterally, and to the perineal body distally (Figures 1 and 2). No site-specific repairs utilize the patient’s own tissue. When an enterocele was present, the vaginal apex was opened via laparoscopy and the xenogeneic graft attached to the pubocervical fascia anteriorly and the uterosacral ligaments posterior-laterally. This technique results in a total replacement of the posterior EPF, reestablishment of the pericervical ring, and is not dependent on compromised in situ collagen tissue. The range of follow-up has been 6 to 33 months (mean, 17 months) with pelvic grading at 3 and 6 months and yearly. The average point A(p) was 0.25 and -.7 pre- and postoperatively (POP-Q). Surgical definition of cure was point A(p) -2.0 or less. At 1 year, 54 of 57 patients (95%) met the criteria for cure. Point A(p) in the 3 patients not meeting these criteria for cure was -1.0 in 2 and 0 in 1. All 3 patients were asymptomatic.
Both types of xenogeneic grafts were easy to use and suture in place. Porcine SIS implant sites were completely healed by 3 months and had a thinner pliable posterior wall, with the grafts being indiscernible. Porcine dermis healed more slowly and at 6 months, the posterior wall was still mildly indurated and thicker than the SIS implants. Differences in healing rate did not appear to be an important factor to patients. Neither early pliability nor increased thickness of the vaginal repair appeared to affect sexual function, as suggested by equal improvement in the sexual quality of life for patients with both grafts. Patients reported significant improvement in splinting, protrusion, evacuation, and dyspareunia in both groups. No grafts were rejected, and no significant complications occurred.
These xenogeneic grafts are being used just as successfully in anterior vaginal wall repair (Figures 3–5). They have been used in combination with both tension-free vaginal tape (TVT) and laparoscopic Burch colposuspension. In our clinic, we have found patients with severe paravaginal defects in which the arcus white line has been avulsed from the obturator internus muscle. Porcine SIS grafts have been used as a bridge to reapproximate the pubocervical fascia and arcus white line back to the lateral pelvic sidewall with excellent results.
We have used both types of xenogeneic grafts sutured to the distal end of polyester mesh strips (Parietex, Sofradim) for sacrocolpopexies. The end of the graft with porcine dermis or SIS is fixed distally to the perineal body or rectovaginal septum, and the polyester end is fixed to the promontory. The xenogeneic materials provide an excellent matrix for tissue ingrowth, and the polyester mesh has superior tensile strength. This “dual mesh” should decrease mesh erosion, because the polyester does not come in contact with the thinned out vaginal wall. The xenogeneic graft should result in a thicker, stronger vaginal wall with increased pliability. The ability to mix different materials for tissue replacement greatly increases our surgical options for reconstructive surgery.
Conclusion. Recurrent prolapse is a common complication in pelvic reconstructive surgery. Classical repairs are dependent on the use of weakened tissue with demonstrated abnormal collagen. This
issue has been compromised by pelvic floor muscle atrophy secondary to pelvic neuropathy. Currently, no treatment exists for pelvic neuromyopathy. The ability to use material that is stronger than in situ tissue or that has the potential to act as a scaffold for new tissue regeneration could be an alternative approach for pelvic reconstructive surgery. Synthetic mesh can be woven to have great tensile strength and be rapidly incorporated into surrounding tissue, making it ideal for areas of high stress. Biomaterials have multipotential for many types of repair. Xenogeneic grafts can be engineered for site-specific repairs that require both strength and function. Like all new technology, the use of these materials must be studied carefully before they are promoted for extensive use in patients. It is necessary to evaluate the long-term outcome of tissue replacement to determine which xenogeneic grafts and synthetic meshes will meet the unique requirements of pelvic floor reconstruction. The early studies for tissue replacement are encouraging.
Figure 1. Posterior vaginal wall dissection exposing rectovaginal septum and rectum.
Figure 2. Porcine dermal graft (inside the arrows) replacing the rectovaginal septum in posterior wall prolapse.
Figure 3. Anterior vaginal wall prolapse. Anchoring sutures have been placed through the arcus white from the ischial spines proximally to the pubic bone distally.
Figure 4. Porcine dermal graft (inside the arrows) replacing the rectovaginal septum in posterior wall prolapse.
Figure 5. Closure of the anterior vaginal wall defect.
Address reprint requests to: Jim W. Ross, MD, PhD, Director, Center for Female Continence, Clinical Professor, Dept Ob-Gyn, UCLA School of Medicine, 400 E Romie Ln, Salinas, CA 93901, USA. Tel: 831 757 3051, Fax: 831 757 3115, E-mail: firstname.lastname@example.org
Jim W. Ross, MD, PhD received his medical training at UCLA, where he also received his doctorate in Neuroendocrinology at the Brain Research Institute. He is the Director of the Center for Female Continence in Salinas, California and a Clinical Professor at UCLA. Dr Ross was a leader in the early development of laparoscopic pelvic reconstructive surgery, being the first to publish on laparoscopic repair of total pelvic prolapse. He has published on laparoscopic Burch colposuspension, paravaginal repair, and sacrocolpopexy. Dr Ross lectures in the United States and internationally and is on the editorial board of several laparoscopic organizations. His special interests include urinary and fecal incontinence, pelvic floor reconstructive surgery, and the neurophysiology of pelvic organ prolapse.
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