Synthetic mesh should be reserved for patients who have had multiple failures with traditional repairs and who are not sexually active. Sexual behavior is key to the decision-making process I undertake with my patients because synthetic mesh can cause a loss of elasticity in the vagina and consequent dyspareunia. When synthetic meshes are selected, the surgeon should use a minimal amount of material to cover as small an area as possible. It should not be used concomitantly in both the anterior and posterior compartments, as the risk of mesh contraction, rigidity, and vaginal shrinkage is too great.
Incisions in a mesh-augmented anterior or posterior repair should be 3-4 mm thick, passing through the full thickness of the vagina. Posterior compartment incisions should be kept as small in length as possible to reduce the risk of erosion/exposure and hematoma. In the anterior compartment, for similar reasons, surgeons are increasingly moving toward using small semilunar incisions.
In addition to the well-reported risks of erosion, exposure, and extrusion, synthetic meshes pose a problem from an infection point of view. Not uncommonly, synthetic grafts are found upon removal to be covered with biofilms – matrices produced by bacteria or fungi that colonize the material and house the organisms. Biofilm formation can lead to both acute, significant infection and long-term chronic infection; it also can result in metastatic infection if the biofilm breaks off, fragments, and is transported to other areas of the body.
Minimizing infection risk
Biofilms have been known and studied for some time, but there is growing appreciation for the role they play in infections that are chronic, recurrent, or hard to detect and treat. It has been shown, for instance, that patients with recurrent bacterial vaginosis have Gardnerella vaginalis–generated biofilms that house the bacteria and keep it from being adequately penetrated by white blood cells or antibiotics.
Ongoing research is looking for agents to break down biofilms so that antibiotics can reach the infectious organisms embedded within them. At the current time, we do not have any tools available, other than the benefit of understanding how biofilms form, work, and can be prevented. Biofilms can form on a variety of surfaces, synthetic or natural, but clearly, permanent synthetic meshes are more likely to house biofilms than are biologic meshes.
In any case, every patient undergoing POP repair – any surgery, for that matter – should be evaluated prior to the procedure to determine if she is at higher risk of infection. The patient’s vaginal microflora should be evaluated, and conditions such as bacterial vaginosis or aerobic vaginitis should be treated presurgically to reduce her risk of postoperative infection.
Infections rates for POP surgery are not published, to my knowledge, but there is reason to believe the rate is substantive (the infection rate associated with hysterectomy, depending on the population, is 5%-9%, and we do know that most postsurgical pelvic infections are derived from the vaginal microflora.
I also advocate checking the vaginal pH in the operating room before the vagina is prepped. In my surgeries, if the pH is 4.5 or lower, a standard regimen for antibiotic prophylaxis (1-2 g cefazolin) is administered. If the pH is greater than 4.5, then 500 mg metronidazole is added to this standard regimen. This covers pathogenic obligate anaerobes, whose growth is favored in an environment with a higher pH. Antibiotic prophylaxis should be administered one time only.
It is important to recognize as early as possible the patient who is developing an infection or has an infection. There are no definitive signs of developing or early infection. Therefore, any patient who develops postoperative fever (101°F or higher) and has a pulse rate of 100 or higher and an elevated WBC count should be evaluated (physical examination including a pelvic exam). It is important to rule out infection involving the respiratory system, urinary tract, and pelvis.
If there is no evidence of infection, further observation is acceptable. If there is strong suspicion of infection, further evaluation is warranted (ultrasound or CT scan) and broad-spectrum antibiotics should be administered. The patient should be evaluated daily to determine the response to treatment.
Contrary to popular belief, some infections (such as group A streptococcus, group B streptococcus, Escherichia coli) can set in early, within 24-48 hours after surgery.
My experience with biologics
Pelvic reconstructive surgeons became interested in biologic material because both animal studies and clinical experience in other surgical areas, such as hernia repair, have demonstrated a high degree of neovascularization and reepithelialization at the implantation area. When non–cross-linked biologic material is implanted onto or near fascia, new fascia is generated. When it is placed at the site of skin dissection, skin is regenerated. Over 3-6 months, the graft materials break down and are excreted from the body. The risks of complications and infection with non–cross-linked biologic meshes are low in comparison with the synthetic nonabsorbable meshes.