Hernia (2003) 7: 57–60 DOI 10.1007/s10029-002-0107-8

E D I T ORI AL

R. Stoppa

About biomaterials and how they work in groin hernia repairs

Received: 24 June 2002 / Accepted: 4 November 2002 / Published online: 3 April 2003 Ó Springer-Verlag 2003

This paper focuses on the intimate mechanical action of nonabsorbable mesh prostheses against reherniation by a variety of modes, which likely depend on the size of the prosthesis. Thus, important elementary properties, like strength, rigidity, thickness, and porosity — which are satisfactorily tested in currently used fabrics — will be shortly considered. Since the middle of the 20th century, surgeons have been provided with acceptable prosthetic material in abdominal wall surgery. Experimental studies and clinical use of modern unabsorbable meshes have demonstrated an almost similar biological tolerance, fitting Cumberland and Scales’ criteria [1, 2, 3]. All of them are resistant to sepsis when antibiotics are instituted and the septic collection is drained. Macroporous meshes are quickly incorporated into the scar granuloma and the scar sclerosis. Experimental studies suggest that synthetic mesh materials induce a guided fibrotic tissue response useful to providing a firm definitive scar. Several events explain the current—even if debatable—popularity of the use of prosthetic materials in groin hernia repair. Historically, this indirectly started with the anatomic contributions from the first half of the 20th century. Harrison (1922) [4], Anson (1938) [5], McVay (1971) [6], and Condon (1964) [7], underlined the unfavorable variations of the regional muscles, which increase the risk of herniation through the transversalis fascia with the enlargement of the weak area of the groin. Fruchaud (1956) [8] described the myopectineal hole as a large gap in the deep myofascial layer of the groin that led to his conception of a natural weakness of the normal groin architecture and a unification of groin hernias. Thus the idea of an extended repair of the groin deep floor was conceived, for which the performance of

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prostheses able to replace or reinforce the transversalis fascia are convenient. Another promotional event has been the critic of pure tissue repair, dealing with the generally harmful effects of tension on a suture line, which are not regularly avoided by relaxing incisions. This has been developed, since Halsted (1903) [9], by Usher (1959) [10] and Lichtenstein (1989) [11], among others, and led logically to choosing tension-free and even sutureless procedures using prosthetic materials for groin hernia cure. In addition to the mechanical explanation of hernia, the role of biometabolic factors was discovered in the 1960s [12, 13, 14, 15, 16]. Further, if it is not yet a question of a genetic therapy of hernias, the surgeon is logically influenced to use a mesh for mending the metabolic defect of inguinal hernias. The posterior approach has also favored the use of mesh in hernia cure. In open classical surgery, the preperitoneal route—of Cheatle [17] and Henry [18], popularized by L.M. Nyhus—creates, at the same time, a fitting place for a mesh. Laparoscopic hernia repairs, which appeared in the early 1990s, have rapidly turned out to be exclusively prosthetic repairs by adjusting the open procedures to minimally invasive posterior routes. Lastly, the collaboration between imaginative surgeons and industry creators has produced a new look in fabrics, such as: preshaped prostheses with an anatomic memory—for lack of any cleverness—aiming for an easy placement with automatic stability; also composite meshes, mixing different elementary components, are currently being tested. Today, the tendency to systematically use prosthetic material in hernia cures is worth thinking over critically [19, 20, 21, 22]. Even if it is admitted and assessed that macroporous mesh is well incorporated into the scar tissue, the uncertain healing in the contact with plugs should be underlined. The center part of a cylindrical plug is never penetrated by the connective tissue and is similar to a ‘‘forgotten’’ surgical foreign body; a flat plug is subject to shrinkage, which does not exactly fit its obturator function. When using mesh pieces, other

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critics related the potential morbidity due to foreignbody effects. Of course, sepsis is no longer a scarecrow against the use of synthetic mesh, and this would have been assessed since Usher’s demonstrations (1959) [10]. Indeed, the rare migration into a hollow viscus can be avoided by an exclusively extraperitoneal placing of the mesh. More frequently observed sequelae are postoperative pains, mostly after plugs or overlay placement, and laparoscopic stapling of mesh prostheses. Abdominal wall compliance troubles are an unavoidable counterpart of large incisional hernias mending with large mesh prostheses. The carcinogenic risk (sarcoma) that appeared in some clinical cases 5–20 years after the use of vascular prostheses has never been documented after abdominal wall repair with mesh; generally, experimental studies report the responsibility of animal species and foreign-body morphology (films are much more inducive agents than powders or nets) rather than the chemical constitution of the material. Nevertheless, the hernia surgeon must be attentive to those critics, for the information of patients, at least, and for the respect of security precautions, an essential virtue in therapeutical matters. Generally speaking, research should be carried out to lessen the foreign-body effects of prostheses—for example, by reducing their mass —and to improve their barrier effect. Meanwhile, the personal role of the surgeon should be to limit the use of prosthetic material to the cure of hernias with high risk for recurrence. Also, choosing an individually proper one among the current diverse fabrics is recommended; Amid’s classification of biomaterials following technological bases can help to answer this requirement [23]. Last, but not least, attention should be given to the praiseworthy attempt to reduce the size of the prosthesis while preserving its efficiency, a challenge to be taken up by the light of a reflection on biomaterials’ ‘‘directions for use’’ in hernia cure. Pe´lissier et al.’s (2001, 2002) [24, 25] publications have recently pointed out that ‘‘the size of the mesh currently used for surgical repair of groin hernias differs significantly from one technique to another.’’ This is evident when comparing the 40–50 cm2 of Trabucco patch [26] to the 200 cm2 of a laparoscopic patch, and mostly to the more than 400 cm2 of Stoppa bilateral prosthesis [27, 28]. Now mesh procedures using patches of different sizes are credited with comparable low recurrence rates in clinical reports and comparative studies [29, 30]. Yet perioperative morbidity and sequelae have a potentially higher frequency after use of large pieces of mesh than when using small ones. Pe´lissier et al., consequently, propose using a small patch, only covering the supraligamentar compartment of Fruchaud’s myopectineal hole, in most of Nyhus types IIIa and IIIb inguinal hernias, and large preperitoneal prostheses only in selected cases at high risk for recurrence. Now curious hernia surgeons—as interested as every one of them should be—may be inquisitive about the mode of action of prostheses, so strangely equally efficient in spite of the diversity of their shape, size, and site

of placement. Although having in common being tension-free procedures, repairs using mesh should be considered methods working in very different ways fitting the polymorphism of hernias and the principle of individualization of their cure. For individual choice of an adequate method, it seems important to evoke how the mechanical barrier effect of the implant is modulated by the size and shape of the prosthetic material. Let me briefly describe how the diverse methods of prosthetic repair work. Owing to their tridimensional shapes, plugs should be separated from flat pieces of mesh, which are bidimensional artificial layers. Plugs are stoppers acting by their mass; they have with the transversalis fascia a circular contact restricted to the thickness of that layer, while pieces of mesh have a larger contact by interposition between two layers of the groin wall. I mentioned some doubts on the late postoperative future of plugs. About repairs with meshes by pieces, one can consider that there are three current methods of using them. In chronological order of appearance, they use very different sizes of meshes with much different modes of action. 1. Buttressing or replacing the transversalis fascia in the retrofascial space using 100–200 cm2 pieces of mesh—overcovering the weak area of the groin, assuming a wide face-to-face adhesion with both the contiguous wall layers by the healing process—is the first method. Pioneered by Acquaviva (Nylon, 1944) [31], Usher (Polypropylene, 1959) [10], and Rives (Polyester, 1967) [32], it is still used by anterior or posterior routes, for mending types III (A & B or IV hernias in Nyhus classification [19] (Fig. 1). 2. Making the parietal peritoneum unextensible by a wide wrapping of the visceral sac into a bilateral piece of mesh of very large size (>400 cm2) has been used by R. Stoppa since 1965, through a preperitoneal approach (Fig. 2). In that special method, Pascal’s hydrostatic principle uses the intra-abdominal pressure to push the mesh against the abdominal wall. Thus, no closure of the hernia hole and no fixation of the prosthesis are necessary. Presented as the most extensive use of mesh and an almost absolute weapon

Fig. 1 Schematic representation of a horizontal cross section of the abdominal wall at the level of the groin regions, after placement of a large mesh sublay. The hatched area shows the extent of the fibrotic tissue. eo External oblique muscle, io internal oblique muscle, t transversus muscle, R rectus muscle, P prosthesis, F transversalis fascia

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Fig. 2 Schematic representation, from a bird’s eye view, of a wide wrapping of the visceral sac into a very large piece of mesh. P Bilateral mesh prosthesis. (adapted from [37] with permission)

against recurrence, it is indicated in complex, multirecurrent, bilateral hernias. 3. With the publications of Lichtenstein (1989) [11], Gilbert (1988) [33], and Trabucco (1998) [26], a third method has appeared, using small pieces of mesh of around 50 cm2 of surface dimension—just nearly enough for covering the supraligamentar (inguinal) compartment of Fruchaud’s myopectineal hole [8]. I think this ‘‘mini mesh method’’ works differently for opposing reherniation. While the two methods first mentioned are mechanical remedies against the groin weakness, this third one has no buttressing action, and it can hardly be called a patching—in the usual sense given by real menders to that process. Small pieces of mesh seem to act by inducing around them a just sufficient amount of sclerosis able to lock the mechanism of appearance of a peritoneal diverticulum and to impeach any growth of inguinal hernia sac (Fig. 3). That mechanism is specific for inguinal hernias in which the size of the sac increases by the sliding of the parietal peritoneum at the level of its moving neck through the parietal hernia hole. The scar sclerosis of the transversalis fascia in contact with the mesh locks the sliding function of that bilaminar layer, whatever the positioning, either pre- or retrofascial, of the prosthesis. Incidentally, one should be reminded of the much different growth mechanism of an umbilical hernia, which is an episodic tearing of its sac because its peritoneal neck has a fixed position. The functional mode of action of small protheses appears similar to that working in procedures like plugs or even high ligation of the hernial sac. Besides their apparently evident role of filling the hernial gap, plugs indeed gain their fixation into the inguinal wall by the means of scar sclerosis; otherwise, we should have no

Fig. 3 Schematic representation of a sagittal cross section of the inguinal wall after placement of a small-sized overlay. The scar fibrosis is pictured as a hatched area only present at the posterior aspect of the prosthesis (P) to better illustrate how it locks the sliding function of the transversalis fascia (F) at the arrows level. eo External oblique muscle, io=internal oblique muscle, t transversus muscle

real confidence in the dubious efficiency of stitches for their definitive stability. About high ligation of hernial sac—formerly proposed by Russel (1906) [34]—one must remember the striking remark of Keith (1924) [35], suggesting that if complete excision of the sac alone could cure an inguinal hernia, it is the most probable result of the incidental tightening of the fascial supports of the internal inguinal ring, inducing a limited scar sclerosis area, which is often efficient against reherniation in youngsters. Yet there is a noticeable difference between a simple tissue repair and a small prosthesis repair: the latter keeps up a guided fibrotic response able to provide a firmer scar, than does the former, whose solidity relies only on the stitches’ anchorage. Comparing the above-mentioned methods’ actions, from the angle of a definitive firm repair requirement, leads to the following remarks: the larger the size of the mesh, the greater the stability of the prosthesis; the wider covering of the weak area, the lesser the risk of reherniation. Large protheses have a direct mechanical role, proportional to their size. They are evident barriers, whose effect rises at a maximum with Stoppa’s reinforcement of the visceral sac. They oppose both Moschowicz’ mechanisms due to the ‘‘pushing’’ and the ‘‘pulling’’ forces of herniation. In contrast, in my opinion, smaller meshes have a rather neatly indirect role, which consists of inducing a host-tissue response limited to their reduced size; their physical presence is relayed by

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a biological process: a fibrotic locking of the peritoneum sliding at the level of the hernial hole. Therefore, reservations can be made owing to the following points. Variations of the groin weak area size, depending on regional muscles, variable insertions, and the anatomic modifications created by the presence of large or recurrent hernias, call for the use of diverse sizes of prostheses. Moreover, nowadays evidence has accumulated on metabolic factors contributing to herniation and reherniation through systemic [Wagh, (1971), Read (1970), Peacock, (1978), Cannon (1981)] [12, 14, 15, 16] or regional [Pans (1999)] [13] histochemical abnormalities of aponeuroses and fascias in patients with hernia, particularly direct and bilateral ones. Thus 10 years after the repair, the limited fibrotic anchorage of a small prosthesis on a fascia impaired by metabolic diseases may be subject to dehiscence. Of course, good surgical strategy includes comparing other most important requirements for quality assessment and cost-effectiveness in hernia surgery. As mentioned previously, I shall not discuss their influence on the choice made by the surgeon among the diverse above examined methods. Basically, I agree with Nyhus’ ancient and repeated exhortation [20] to individualize hernia repair, and I think this principle should be applied to the group of hernias needing a mesh repair. Again, given the popularity and the effectiveness of procedures using mesh pieces of very different sizes, the purpose of this note was to examine the respective support of their mending action and to propose my reflection on the diverse ways biomaterials act against reherniation through host-tissue response of very diverse mechanical effects, depending on the mesh morphology. Rene´ Leriche, a famous French surgeon (1949), said: ‘‘La nature ignore nos intentions.’’ (Nature is not aware of our intentions.) [36]. Perhaps this is a reason why the ubiquitous and daily hernia surgery is anything but a routine one.

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