Sutures and Synthetic Material in Reconstructive Pelvic Surgery

Sutures and Synthetic Material in Reconstructive Pelvic Surgery
Rubin Raju
Olivia O. Cardenas-Trowers
Emanuel C. Trabuco
Introduction
Pelvic organ prolapse affects approximately 25% of women in the United States with a 13% lifetime risk of undergoing surgery for pelvic organ prolapse.1 Trauma to the pelvic floor associated with childbirth, chronic straining, or as a result of inherent or acquired connective tissue disorders are the main risk factors for developing this condition. When patient fails conservative therapy, native tissue repair using suture or mesh-based abdominal repairs are the main procedures available to address prolapse. Understanding suture and mesh properties is fundamentally important for pelvic surgeons to optimize functional outcomes while minimizing morbidity with the repair.
In this chapter, we review how suture and mesh biology, and the inciting host response they trigger, are key determinants of outcome and types and frequency of encountered complications.
SUTURES IN PELVIC RECONSTRUCTIVE SURGERY
Suture is an indispensable material used in female pelvic medicine and reconstructive surgery (FPMRS). The most common sutures used in FPMRS are synthetic and classified as either absorbable or nonabsorbable. Table 51.1 lists common sutures used in FPMRS. Suture selection is important as suture properties (e.g., absorption rate, filament composition, etc.) may influence surgical outcomes.
Suture Biology
The primary goal of suture material is to approximate tissues until wound healing takes place. Wound healing is usually divided into three phases: initial lag phase, fibroblastic phase, and maturation phase. In the initial lag phase (the first 5 days), sutures provide the main structural integrity for the wound. When tissue is disrupted or injured, there is an immediate response of vasospasm and clot formation at the site. At the time of the initial incident, peaking at 24 hours, and continuing for approximately 4 days, granulocytes are active at the wound site. Epithelial cell growth begins 6 hours after injury and peaks by 24 hours. During this time and continuing up to 30 days postinjury, there is continuous macrophage activity. During the fibroblastic phase (days 5 to 15), local fibroblast growth leads to collagen deposition that leads to rapid increase in wound strength; fibroblast activity and collagen formation continue at a high level for several months. Neovascularization begins 3 days after injury with new vessel formation peaking at 7 days and scar revascularization completing by 30 days. It is during the maturation phase (day 14 and beyond) that connective tissue remodeling leads to formation of a mature, type I collagen-rich scar. Wound tensile strength increases throughout this process; from 3% to 7% at the end of the second week to 50% by 4 weeks. At best, a wound will heal to achieve approximately 80% of its preinjury strength once healing is completed.2
Sutures are divided into absorbable and nonabsorbable.3 Absorbable sutures made from animal sources (e.g., purified bovine intestinal serosa, sheep submucosa) are degraded via proteolysis (broken down by the body’s enzymatic systems), whereas synthetic sutures undergo hydrolysis (broken down by fluid penetration). Proteolysis causes more inflammation than hydrolysis which can lead to more scarring; hence, chromic catgut suture (which degrades by proteolysis) is not typically used to close epithelial tissue. Delayed absorbable sutures (polydioxanone [PDS II, Maxon]) take longer to be absorbed compared to other sutures in this category (Table 51.2). Nonabsorbable sutures resist enzymatic action and remain in the body permanently. The exception to this rule is silk, which resorbed within 2 years.3
The filamentous property of suture is also important to consider. Monofilament suture is composed of one filament and has a smaller surface area than multifilament suture. The weave, or spaces between fibers, in the multifilament sutures enable bacteria (<1 micrometer) to avoid immune cell (>20 micrometers) clearance. Although associated with increased infection risk, multifilament suture are easier to handle. In particular, multifilament suture has less memory than monofilament suture and therefore is more pliable requiring less knots to secure it. Monofilament suture, conversely, passes through tissue easier than multifilament and typically with less of an inflammatory reaction.
Suture Selection
The choice of suture should be based on the volume of tissue needed to be secured, the tensile strength of the tissue being reapproximated, and the potential for bacterial contamination. The smallest suture that can adequately accomplish tissue approximation should be selected.3 If more healing time (e.g., fascia) is required, a suture with a delayed absorption profile (e.g., polydioxanone) should be used.4 Multifilament sutures (e.g., Vicryl or braided silk) have a greater potential for infection compared to monofilament sutures (e.g., Monocryl or Prolene) and should not be used in areas prone to infection, e.g., skin.4 Although there are antibiotic-infused sutures available in the market, there is no evidence that use of these sutures decreases the risk of infection from FPMRS procedures. Silk suture is made from natural material, it is easy to handle and tie secure knots. Silk and nonabsorbable sutures should not be used in the bladder.3 Polypropylene (Prolene) cause less tissue reactive than silk and nylon and hence is ideal for repair of infected or contaminated tissues.3 Coated suture may decrease the friction of the suture when reapproximating tissue. The barbed or “knot-less” sutures have been shown to decrease operative time and is available as an absorbable or nonabsorbable configurations.
Potential Complications of Permanent Suture
Suture erosion, diskitis, osteomyelitis, sinus tract formation, and abscesses are rare but potential complications of permanent suture use in FPMRS.5,6,7 To minimize the risk of diskitis and osteomyelitis during sacrocolpopexy, suture placement should not penetrate deeper than 1.9 mm into the anterior longitudinal ligament of the sacrum (the median thickness of this ligament)8 and should avoid the disk space at the promontory. To decrease the risk of sinus tract formation and infection, permanent braided sutures (e.g., Gore-Tex or Teflon) should not penetrate the vaginal epithelium.
Sacrocolpopexy
Optimal suture selection has been most extensively studied in sacrocolpopexy. A sacrocolpopexy involves suspending the vagina to the sacrum, typically with mesh secured with suture. Minimally invasive sacrocolpopexy, which is sacrocolpopexy performed laparoscopically or with robotic assistance, has been shown to result in improved outcomes such as decreased blood loss, infection, and pain and faster recovery time compared to abdominal sacrocolpopexy.9,10 As a result, studies have primarily evaluated different suture materials in the outcomes of minimally invasive sacrocolpopexy.11 A multicenter randomized trial comparing the use of nonabsorbable suture (Gore-Tex) with delayed-absorbable monofilament suture (polydioxanone) for vaginal attachment of the Y-shaped lightweight mesh found no differences in mesh or permanent suture exposure rates (5.1% vs. 7.0%, respectively; risk ratio 0.73, 95% confidence interval [CI] 0.24 to 2.22).12 A limitation of the study was that it did not standardize vaginal cuff closure, which was performed with various absorbable sutures. Most patients (9/12, 75%) with mesh or suture exposure were asymptomatic.12 Retrospective studies have similarly found that absorbable suture appears to yield equivalent anatomical outcomes with lower risk of suture erosion compared to permanent suture for vaginal attachment of mesh during sacrocolpopexy.13,14 However, the use of nonabsorbable, braided suture for vaginal mesh attachment to the vagina was found to be an independent and significant risk factor for mesh or suture exposure (odds ratio, 4.52; 95% CI 1.53 to 15.37)15 and should be avoided.
The data on the use of bidirectional, barbed, self-anchoring, delayed absorbable suture for vaginal attachment of sacrocolpopexy mesh, is controversial with some studies showing no differences in anatomical recurrences and others finding increased recurrence for mesh attachment with interrupted delayed absorbable suture.16 Further study in this topic is warranted as self-anchoring suture use is associated with significantly faster mesh attachment compared to interrupted suture use (29 minutes vs. 42 minutes, respectively, P < .001).16 Noncomparative studies evaluating self-anchoring suture use in sacrocolpopexy have found this approach to be safe and effective.17,18,19
Mesh attachment to the anterior longitudinal ligament has traditionally used nonabsorbable suture. The necessity of this practice has been questioned by a retrospective cohort study of robotic sacrocolpopexy using absorbable suture (polyglactin 910) for sacral attachment. At a median follow-up of 33 months 10 patients (7.6%) had prolapse recurrence, however, only 2 had apical failure (only 1 of which appeared to have mesh detached from the sacrum). This finding suggests that nonabsorbable suture may be utilized for sacral attachment.14
Hysterectomy
Hysterectomy is often performed concurrently with vaginal and abdominal prolapse repair procedures. Absorbable suture is most often used to close the vaginal cuff. However, the delayed absorbable barbed suture has gained popularity in minimally invasive hysterectomy. A 2015 systematic review20 and a 2019 randomized controlled trial21 comparing conventional suture to barbed suture for vaginal cuff closure during minimally invasive hysterectomy found that both suture materials are equally efficacious and safe for vaginal cuff closure with shorter operative times for the barbed suture.
Vaginal Apical Suspension
As an alternative to sacrocolpopexy, the apex of the vagina can be suspended to uterosacral ligaments or to the sacrospinous ligament. There is no difference in anatomical success between uterosacral ligament suspension performed with absorbable and nonabsorbable sutures; however, use of nonabsorbable suture increases the risk of suture exposure.22,23,24 In fact, the use of braided nonabsorbable suture in sacrospinous ligament fixation resulted in suture-related complications in 36% (23/64) of patients, with 70% (16/23) requiring suture removal.25 Even though there is presently no comparative data available to guide suture selection for sacrospinous apical suspension, the use of nonabsorbable braided suture should be avoided for both commonly used of apical suture repairs.
Vaginal Wall Repairs
The literature comparing suture material for vaginal wall repairs (i.e., colporrhaphy) is limited. There is no difference in anterior prolapse support between anterior colporrhaphy repaired with nonabsorbable or absorbable suture; with suture exposure being observed in 15% of the patients in the nonabsorbable suture arm.26 The literature is also inconsistent regarding the benefits of delayed absorbable suture for anterior colporrhaphy; with some studies showing improved anatomical results and others showing no difference compared to rapidly absorbable sutures.27,28 Note, however, that the use of delayed absorbable suture was associated with significantly higher rates of urinary urgency.27 There is no benefit for the use of delayed absorbable suture in the posterior compartment.27
SYNTHETIC MESH AND BIOLOGIC MATERIAL USED IN PELVIC RECONSTRUCTIVE SURGERY
Mesh is defined by the International Urogynecological Association/International Continence Society as “a (prosthetic) network fabric or structure; open spaces or interstices between strands of the net”29 that are used in prolapse repairs. Graft on the other hand refers to “any tissue or organ for transplantation.”29 In pelvic surgery, “graft” is a general term that refers to three types of materials: autografts (derived from patient), allograft (derived from cadaver), and xenografts (derived from nonhuman sources). Surgical repair of pelvic organ prolapse can involve placement of mesh or graft to reinforce the native connective tissue and restore prolapsed organs to their anatomical position. There has been controversy surrounding vaginal mesh use for pelvic organ prolapse repair, and recently on April 16, 2019, the U.S. Food and Drug Administration (FDA) ordered manufacturers of mesh for transvaginal repair of anterior compartment prolapse to stop selling their products.30 The FDA’s response stems from increased number of severe mesh-related complications reported to Manufacturer and User Facility Device Experience (MAUDE) and to FDA with no significant improvement in clinical outcomes. Yet, it is critical to understand that the FDA’s recommendation was explicitly directed toward vaginal mesh kits and do not apply to mesh use for midurethral slings and for abdominal prolapse repair. Because these remain commonly performed procedures, it is imperative that the pelvic surgeon understand mesh biology and how intrinsic material characteristic impacts healing and complications.
Mesh and Graft Biology
Materials used for pelvic reconstruction can be classified into (1) synthetic mesh, (2) biologics also known as grafts (autografts, allografts, xenografts), and (3) composite material. Table 51.3 is a summary of the advantages and disadvantages of these different kinds of mesh.31
Synthetic materials
Synthetic mesh used can be absorbable, nonabsorbable, or a combination of absorbable and nonabsorbable material.
Absorbable mesh
Absorbable mesh (polygalactin 910 [Vicryl], polyglycolic acid [Dexon]) will degrade over time (polygalactin 30 days; polyglycolic acid 90 days) through a process called hydrolysis and is replaced by a collagen-rich scar tissue that provides strength to the site of repair.32 They have a lower risk of infection, mesh exposure, or erosion.33,34 The resultant scar tissue, however, has less mechanical stability when compared to scar tissue containing nonabsorbable mesh.33,35 This theoretically can lead to an increased risk of recurrent pelvic organ prolapse.
Nonabsorbable mesh
Nonabsorbable mesh such as polypropylene (Prolene) and expanded polytetrafluoroethylene (ePTFE, Gore-Tex) remain indefinitely at the site of repair and are considered permanent implants. The persistence of nonabsorbable mesh allows for better tensile support33 and decreases the risk of pelvic organ prolapse recurrence. Polypropylene is the most widely used nonabsorbable material due to its relatively inert nature, easy of tailoring, and cheap cost.36 Nonabsorbable mesh were initially classified by Amid37 based on pore size and filament type (Table 51.4).Type I mesh (macroporous >75 micrometers), with large pore size, allows for collagen deposition and neovascularization throughout the mesh and results in incorporation of the material with the surrounding tissues.38,39 Moreover, the large pore size allows for immune cells (>20 micrometers) to phagocytize bacteria throughout the mesh field. Type 1 mesh is currently the preferred choice for pelvic reconstructive surgery as it is associated with fewer complications compared to type 2 and 3 meshes.40 Specifically, as discussed in detail in the following text, lightweight type 1 materials (pore sizes greater than 1 mm in diameter) are less stiff and more suitable for use in the vagina given vaginal requirements to accommodate change in volume with stooling and intimacy.41
Combination absorbable and nonabsorbable mesh
Combination of absorbable and nonabsorbable mesh material (e.g., polypropylene with polygalactin [Vypro] or with poliglecaprone [UltraPro]) attempts to further minimize the risk of mesh exposure. Theoretically, the absorbable component of the mesh provides temporary wound integrity and strength while lowering the permanent mesh load. As a result, these materials have functionally larger pore size (as the absorbable component eventually is resorbed), lower stiffness, less long-term inflammation; characteristics which may lead to improved outcome with lower complications.32

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May 1, 2023 | Posted by in GYNECOLOGY | Comments Off on Sutures and Synthetic Material in Reconstructive Pelvic Surgery

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