**2. The use of materials in pelvic surgery**

correlates with patients' symptoms [1]. Prolapse of the anterior vaginal wall (or a cystocele) is the most common type of POP followed by a uterine or vault prolapse and rectal prolapse [2],

Some degree of POP is seen in up to 30–76% of women who have their routine gynaecological examinations [3]. Most of these will be early stage/mild prolapses and cause no symptoms [4]. Although only 3–6% of these cases will have any symptoms, the lifetime risk of a women in the general population undergoing a POP surgery has been reported to be 20% (excluding hysterectomy cases) [3]. As the population ages the prevalence of POP is estimated to increase

Reconstructive surgery to improve positioning of the pelvic organs or to restore the supporting structures is often necessary in symptomatic cases and the use of a graft material is often needed to reinforce weakened tissues. The most commonly used material is a surgical mesh made of polypropylene (PPL) which has long been used successfully to treat hernias. Although mesh augmented POP repair procedures have higher anatomical success rates compared to no-mesh, the functional and quality of life outcomes are not as good [6] and severe complications with life changing consequences can occur in up to 10–30% of cases [7]. Complications associated with the use of vaginal mesh are now reported widely in the media together with many litigations against physicians and manufacturers leading to the withdrawal of several mesh products from the USA market [8]. In the UK there are now 800 compensation claims made against the NHS in relation to vaginal mesh related complications [9]. In 2008 and 2011 the Food and Drug Administration (FDA) of United States of America released two public health warnings related to mesh complications [10] which was followed by statements from Medicines and Healthcare products Regulatory Agency (MHRA) in United Kingdom [11] and the European Commission [12]. Consequently transvaginal meshes were re-classified from being class II (a moderate risk device) to class III (a high risk device) making pre-market approval necessary before new devices could be marketed [13]. As a consequence the relative number of mesh augmented transvaginal POP repair procedures decreased sharply from 27 to 2%, among all other types of POP surgeries [14]. The number of mesh sling surgeries for treatment of stress urinary incontinence has also decreased [15].

Factors affecting occurrence of mesh related complications can broadly be classified as factors related to the material itself and factors related to the application of the material [16]. Material properties involve the composition of the polymer used, total bulk of the material used and its biocompatibility, mechanical properties and ultrastructure such as pore size and knit pattern. Factors related to the application of the material are the surgical technique used, the route of implantation [transvaginal vs. transabdominal], surgeon's experience and patient related fac-

In this chapter we will first explore the evolvement of the surgical mesh as a material used in abdominal hernia repair together with the modifications made to the surgical technique of implantation to improve patient outcomes. We then move on to define the mechanical and biological properties of the female pelvic floor to determine the design requirements of the ideal pelvic floor repair material. Finally we will look at the current approaches to develop novel materials using mainly biomaterials and tissue engineering techniques with reference

although they coexist in most patients presenting with symptomatic POP.

substantially by 46% between 2010 and 2050 [5].

36 Pelvic Floor Disorders

tors [obesity, smoking status, etc.].

to some of the work from our own group.

In pelvic organ prolapse surgeries, prosthetic materials are either needed to reinforce the surgical repair site in anterior and posterior vaginal wall defect repairs or to suspend the prolapsed uterus or vaginal vault in sacrocolpopexy operations [17]. Surgeries performed for stress urinary incontinence use this material under the urethra as a sling.

The ideal prosthetic material is desired to provide a durable structural support without causing significant complications such as pain, compromise in vaginal capacity or sexual functions. A wide variety of synthetic and biological materials have been used over the years as prosthetics however the perfect material is still to be developed.

Biological materials are mostly in the form of biological grafts from the patient's own tissues from abdomen (rectus fascia) or thigh (fascia lata). These autologous fascia have long been used as a sling in the treatment of stress urinary incontinence [18]. The obvious limitation of using an autologous fascia is increased perioperative morbidity, donor site morbidity and lack of availability of enough material in some patients who require repeated procedures or have large areas of fascia defect. Using natural fascia from allogeneic (e.g. cadaveric) or xenogeneic (e.g. bovine dermis) sources has also been used over the years but these carry a small risk of prion and Human Immunodeficiency Virus transmission. Also the decellularization, sterilization and other processing methods are known to adversely influence the biomechanical properties of the fascia [19]. The clinical efficacy of biological implants are still controversial with some studies showing high anatomical and functional failure rates [20, 21] whereas others report results comparable to mesh repairs in less severe cases of POP [22].

A basic understanding of the material properties of the available grafts and the physiological requirements of the site of implantation is required to select the best material for a specific application.
