Introduction

At one point up to 300,000 surgical procedures were performed annually in the United States for pelvic organ prolapse. It has most recently been estimated that women have a 20% estimated lifetime risk of surgery for stress urinary incontinence (SUI) or pelvic organ prolapse (POP)[1]. This had previously been estimated at 11.1% based on a small 1995 study in the Northwest region of the United States. A large percentage (6%–29%) of these women will require additional surgeries for recurrence. The evolution of midurethral slings and vaginal prolapse kits in the early 2000s may have contributed to this rise in surgical management, as more gynecologists could offer these procedures.

History and Development of Pelvic Mesh Implants

The first modern sling procedure evolved from a 1907 procedure by Giordano involving the use of gracilis muscle flaps. A permutation followed in 1917 by Goebell, Frankenheim, and Stoeckel using the pyramidalis muscle and rectus fascia. Over the 1930s and 1940s musculofascial slings began to fall out of favor and pure fascial slings became preferred. Procedures such as the Marshall–Marchetti–Kranz procedure and the Burch colposuspension soon followed [2]. Both were invasive, requiring an abdominal approach, and researchers began looking for less invasive alternatives. In 1986 it was discovered that pressure applied unilaterally to the mid-urethra could control urinary leakage during cough. A separate, and at the time unrelated, discovery revealed that implanted Teflon caused a collagenous tissue reaction. Experiments first began in dogs in 1987, where Mersilene tape was implanted retropubically in 13 large breed dogs with the goal of synthetically recreating the pubourethral ligament by placing and then removing the tape after 6 weeks. The goal was that fibrosis would reinforce the pubourethral ligament, leading to continence. Human testing began in 1988 on a total of 30 women. Results were very reassuring, with 100% cure of stress and mixed incontinence but unfortunately 50% had recurrence upon removal [3]. In 1990, Ulf Ulmsten of Sweden and Peter Petros of the United States collaborated and determined that a permanently implanted option was required. They theorized that stress incontinence resulted from a weakened pubococcygeus muscle that was unable to lift the urethra against the pubourethral ligament and compress it during times of increased intraabdominal pressure. The midurethral sling served to recreate this ligament and restore normal urethral coaptation [4]. Mersilene tape was eventually found to have a high rate of erosion and fistula formation therefore other materials were investigated and polypropylene was found to be a more ideal substance. Amid type 1 mesh (a macroporous mesh with pores >75 μm) was found to be ideal, as it facilitated infiltration of the mesh by macrophages, fibroblasts, and blood vessels. The promotion of tissue ingrowth resulted in improved support with decreased risk of infection.

In 2001 initial five-year data from Sweden, Finland, and France showed an 85% cure rate. Finland published a nationwide analysis in 2002 with data from 38 hospitals. This included 1,455 tension-free vaginal tape (TVT) procedures performed from 1997 to 1999. Rates of operative complications included bladder injury 3.8%; active bleeding (>200 mL) 1.9%; and injury to major nerve, artery, or urethra 0.07%. Postoperative complication rates included retropubic hematoma 1.9%, minor voiding difficulty 7.6%, urinary retention 2.3%, urinary tract infection 4.1%, and defect in vaginal healing 0.7% [5]. When evaluating these rates, it is important to understand the training required in Finland before surgeons were allowed to place these devices. Providers desiring to perform these procedures had to go through training at the University Hospital of Helinski beginning with theoretical training regarding a focus on the mid-urethra rather than bladder neck. They then had to attend and observe two to eight procedures, assist with two to four, and perform two or three under supervision. They obtained a certificate of completion at the conclusion of the training. Only certified surgeons could obtain TVT kits for clinical use. A follow-up program also called for registration of any intra- or postoperative complications. Given the extent of this training the early reported complication rates were low and not representative.

Development of Midurethral Sling Systems

In 1996, Boston Scientific released the ProteGen Sling. This sling was approved by the FDA on a 510(k) process. A 510(k) is a premarket submission for medical devices in which the device must demonstrate that it is substantially equivalent (i.e., at least as safe and effective) as a legally marketed device. This process allows for fast-track approval without a more rigorous premarket approval process or clinical testing. The approval of the ProteGen sling was based on the Ethicon Mersilene mesh created in the 1950s for repair of hernias. Multiple other companies followed suit: Ethicon’s TVT sling (1997–98), Influence Inc’s IN-SLING (1997) and TriAngle (1998), and the Mentor Suspend Sling (1998). The Ethicon Gynecare division began an aggressive marketing campaign and within years revolutionized the treatment of stress incontinence. Burch colposuspension quickly became a historic procedure. In the early 2000s companies marketed various retropubic slings such as American Medical Systems (AMS) SPARC and Boston Scientific’s Advantage and Lynx systems. Unfortunately, at this point the story regarding mesh takes a downward turn. Complications began to appear relating both to the mesh itself as well as incorrect use. In January 1999 Boston Scientific submitted a voluntary recall of ProteGen to the FDA due to a higher than expected rate of vaginal erosion and dehiscence. It stated the device did not appear to function as anticipated. Despite this many other companies had already achieved approval through the 510(k) process and had products on the market. Multiple different modifications and techniques were touted to be safer and easier. AMS developed SPARC (Suprapubic Arc system), which was inserted in a top-down approach. The theoretical benefit was that the most control occurred during initial insertion through the retropubic space when the device passed close to pelvic viscera and vasculature. Second-generation slings utilized the transobturator approach. This approach was touted as a safer option, as it did not traverse the retropubic space and risk of bladder and vascular injury was significantly decreased. In 2001, French surgeon Emanual Delorm introduced an outside-in technique through the transobturator membrane. The Belgian surgeon Jane De Leval followed with a description of an inside-out technique in 2003. Companies soon produced various transobturator slings such as Ethicon TVT-O, AMS Monarc, Boston Scientific ObTryx, and Coloplast Aris. While the transobturator approach had decreased rates of pelvic hematoma, bladder injury, and voiding dysfunction, it had its own unique complications such as groin pain and obturator neurovascular injury. Third-generation slings were aimed at becoming even less invasive. A single-incision approach called TVT-Secure was developed by Ethicon and approved by the FDA in 2006. Single-incision slings were placed through a vaginal incision with fixation to the pubic ramus typically through the obturator internus muscle. This generation of slings had a lower complication rate with quicker recovery but was not immune to issues such as erosion, urinary retention, and pain. As was typical, AMS MiniArc, Boston Scientific Solyx, and Bard Adjust soon followed. In 2003, Daher described a new prepubic approach where vaginal placement exits anterior to the pubic bone. This avoided deep vascular and visceral structures but uniquely placed the clitoral neurovascular supply at risk. Boston Scientific released the Prefyx PPS based on this technique. The various slings, manufactures, and approaches are listed in Table 18.1.

Development of Mesh for Prolapse Repair

As previously mentioned, multiple studies have shown that women have a 30%–50% risk of pelvic organ prolapse and 20% will undergo surgery for pelvic organ prolapse (POP) or stress urinary incontinence (SUI). Based on the initial approval of mesh for midurethral slings, the FDA approved mesh specifically indicated for POP as well. Use of an abdominal hernia mesh had been used by gynecologists for POP repair but required surgeons to cut the mesh to the desired shape and size. Companies began designing and manufacturing products specific to POP based on the increase in this clinical practice. The FDA approved more than 60 different mesh products for POP under the 510(k) process. These mesh products were also made from Amid type 1 polypropylene mesh [6]. The first mesh kits were released in the United States in 2004. These kits were much larger, with more attachment points than the midurethral slings. The first kits released were the AMS Apogee and Perigee systems followed by the Ethicon Anterior/Posterior Prolift and the C. R. Bard Anterior/Posterior Avaulta. Table 18.2 summarizes the indications and attachment sites for these various mesh kits, as it is now very difficult to find this information following device withdrawal from the market. Mesh kits were likely produced, in part, to market to the masses, including lower volume surgeons. The marketing campaigns were aggressive. It has been suggested that surgeons were not provided appropriate training by the manufacturers. Company representatives could frequently be found in the operating room walking surgeons through the procedure.

From 2005 to 2007 there were increasing medical device reports (MDRs) of adverse events related to gynecological mesh products. These reports are maintained in the MAUDE (Manufacturer and User Facility Device Experience) Database, which houses MDRs submitted to the FDA [7]. The increasing frequency led to a review by the FDA and the release of a Public Health Notification informing providers and patients of increased complication rates.

Future Design

Ongoing research has aimed to produce alternative materials that may be better suited for use within the pelvic floor. The University of Sheffield in England recently published evidence supporting use of an estrogen-releasing polyurethane mesh that is more flexible and stimulates cells to produce tissue regeneration [8]. Studies have only been performed in ex vivo models to date. Other companies are evaluating titanium-coated polypropylene mesh as a biocompatible option with less inflammatory response and shrinkage [9]. Boston Scientific elected to modify their current mesh products with blue dye to make visibility during placement, and potential removal, easier.

Legal Status of Mesh

Over time it became clear that mesh complications were not rare and eventually lawsuits against physicians and manufacturers began to be filed [10]. Huge volumes of cases threatened to overwhelm the judicial system if tried individually. In January 2012, several different multidistrict litigations (MDLs) were established in Charleston, West Virginia, to consolidate and manage the vast numbers of similar federal claims. Given the large number of cases, bellwether trials were completed. These are test cases representative of the cases as a whole and are meant to ascertain liability and value for settlement purposes. Bellwether trials are commonly used in MDLs to ascertain what the likely outcomes will be and may lead plaintiff attorneys to pursue or abandon remaining suits based on the outcome. Some of the notable outcomes include:

1. 
   

   1. Scott v. C. R. Bard (July 2012): $5.5 million to plaintiff

   
   
2. 
   

   2. Gross v. Ethicon/J&J (February 2013): $11.11 million to plaintiff

   
   
3. 
   

   3. Lewis v. Ethicon/J&J (February 2014): $0

   
   
4. 
   

   4. Boston Scientific

   
   
   
   
   1. 
      

      a. Pinnacle (July 2014) in favor of defendant

      
      
   2. 
      

      b. Obtryx (August 2014) in favor of defendant in first two cases; however, a third case, Salazar v. Boston Scientific, resulted in $73.5 million to plaintiff

   
   

As of October 2015, more than 104,749 complaints had been filed through the federal court system.

In February 2017 Judge Joseph Goodwin, the judge overseeing all 104,000+ mesh cases, announced orders to expedite proceedings. Subsequently between August and November 2017 an additional 800 cases were added to the various MDLs. Table 18.3 provides a breakdown of the total complaints per company as of November 2017.

Table 18.3 Cases in transvaginal mesh MDLs as of November 2017

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Related

Related posts:

1. Chapter 2 – Neurobiological Basis of Pelvic Pain
2. Chapter 10 – Pelvic Pain Arising from Pelvic Congestion Syndrome
3. Chapter 11 – Irritable Bowel Syndrome
4. Chapter 16 – Other Peripheral Pelvic Neuralgias

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