Tuesday, October 2, 2012

Synthetic material for a PVS


The classification by Amid (1997) used for synthetic materials in hernia surgery may be practically applied to urology as well (Table 1).

Table 1.
Amid Classification for Synthetic Materials
TYPE   
                                            DESCRIPTION                                        
      BRANDS  العلامات التجارية
I  
                                   Pores >75 μm; macroporous          
Atrium, Trelex, Marlex, Prolene
II   
                                Pores <10 μm; microporous         
PTFE: GORE-TEX, Surgical Membrane, Dualmesh
III   
Macroporous with multifilamentous or microporous components
PTFE: Teflon, braided Dacron mesh
(Mersilene), braided polypropylene
mesh (Surgipro), perforated PTFE
patch (MicroMesh)
IV
Submicronic pore size
Silastic, Cellcard (polypropylene
sheeting)
Adapted from Amid PK. Classification of biomaterials and their related complications in abdominal wall hernia surgery. Hernia 1997;1:1521.



The most frequently used materials are grouped into four types.
Type I are totally macroporous prostheses (Atrium, Trelex, Marlex, Prolene) containing pores larger than 75 μm, which is the pore size for admission of macrophages, fibroblasts, blood vessels, and collagen fibers (White et al, 1981; Bobyn et al, 1982; White, 1988).

Type II includes totally microporous prostheses (polytetrafluoroethylene [PTFE]: GORE-TEX, Surgical Membrane, and Dualmesh) containing pores less than 10 μm in at least one of their dimensions.

Type III includes a macroporous prosthesis with multifilamentous or microporous components (PTFE: Teflon; braided
Dacron mesh: Mersilene; braided polypropylene mesh: Surgipro; and perforate PTFE patch: MycroMesh).

Lastly, type IV includes biomaterials with submicronic pore size (Silastic, Cellgard (polypropylene sheeting). Type IV is not appropriate for hernia surgery unless used in combination with type I (Amid, 1992).


The most commonly utilized synthetic material for a PVS is polypropylene mesh (Table 2). It is composed of loosely woven strands of synthetic material, with a pore size greater than 80 μm, permitting passage of  macrophages that may allow better host tissue ingrowth compared with the smoother, more tightly woven counterparts (Kobashi et al, 2005). This represents type I among the Amid classification. In fact, Amid (1997) concluded that the risk of infection and seroma formation was avoided by utilization of type I prostheses.

Historically, sling techniques have changed to limit the associated morbid complications. Synthetic material is no longer utilized in a PVS graft to pull the bladder neck into a high retropubic position owing to high erosion ratesInstead, newer approaches position a sling at the midurethra (Niknejad et al, 2002).

Table 2.
Synthetic Sling Materials
TRADE NAME
COMPOSITION
DETAILS
Mersilene

Polyethylene terephthalatae

Multifilament fibers Very porous, becomes firmly embedded in native tissues
Teflon

Polytetrafluoroethylene (PTFE)
Multifilament
GORE-TEX
Expanded PTFE
Very flexible
Silastic

Silicone plus woven polyethylene terephthalate

Minimal tissue reaction, which facilitates
removal or revision if necessary
ProteGen

Synthetic mesh impregnated with
collagen matrix

Removed from market secondary to high rate of vaginal extrusion
Marlex, Prolene


Polypropylene

Monofilament with
open-weave pattern
Adapted from Niknejad K, Plzak LS, Staskin DR, Loughlin KR. Autologous and synthetic urethral slings for female incontinence. Urol Clin North Am 2002; 29:597611.


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