I guess in nature sharp edges are not very common

I think this is due to the force vectors of pressure and tension of the fascia. 

Good question. Not the incisional herniae only, but all of them at all have had a roundish orifice. Anyone can see intuitively that that defect would take the shape to receive as less pressure from the sac as possible, and circle is the very shape that needed for this. On the other hand, the abdominal wall is the complex of several layers with different biomechanical properties, and no one knows how it works for sure in both normal condition and herniation.

It is Dr.Koshev from Saratov who is working on the hernia biomechanics, if I remember correctly. I shall be seeking for his papers on this matter.

Good luck!

Thanks very much for that input, Dr. Borodach

It depends on the forces acting on the edges of the defect. In a midline defect, the recti on each side are applying almost equal force in either side, the defect would be more vertical. Lateral abdominal wall defects are oriented along the line of the muscle fibers thru which the defect has occured. However when you see a defect during laparoscopy, since one has distended the abdomen with gas and the distension is always spherical as the gas exerts equal outward pressure on the abdominal parieties from within, all defects in the parieties, wherever they are located, will appear circular.

The Laplace equation maybe can explain part of the question

Hi Jani, How are you? Thanks for your input - makes perfect sense.

According to Stoppa analysis, incisional hernia must be considered as muscular desinsertion. The abdominal wall  live as digastric muscle : lateral abdominal wall muscles fibers  are orientated face to face. So I would not say that the hole is always round, it is approximatively round according to the result of strengh on the hedges. This explains you why all suturing techniques are a mistake : recurrence rate will always be high. For all digestive surgeons know that Under tension suture will leak.

If "all the suturing techniques are a mistake" , what kind of technique for the abdominal closure would you suggest?

It is an intereting question and good observation.We see the defects after insufflation when the defect is streched by the gas.Because of the the pressure exerted even if the defect is oval it becomes round.Secondly when we analyse the way we suture only that much of tissue comes in to the loop which subsequently gets ischemic.This almost corresponds to the size and shape.

I think so that it is because of retraction of surrounding tissues.

Sorry but I'm a little bit confused. Are we talking about the shape of an incisional hernia or we are talking about the right technique to close a laparotomy?

To Andrey Borodach : most of the littérature was written in french before 1995, explaining the difficulty for you to know. R. Stoppa published also papers in US littérature, perhaps more easy to read for you. The important point to understand is that the aim is not to close a hole by suturing, but to interpose a mesh (solid in front of the hole) but with large adhesion arround the weak point to allow the organism to stick this prosthesis and transmit strenghts on a large surface.

Dr.Verhaeghe,

1) I can read papers in French - and I'd love to - if they are only available for me. Unfortunately, I did not read works by prof.Stoppa written in his native language, and, by the way, I would be highly appreciate if you upload some here (not for commercial use, of course).

2) Sorry for not being precise enough in my previous post. What namely I meant by it is as follows: Do you suggest using the mesh not only for incisional hernia, but do that for usual laparotomies as well?

Sincerely,

Andrey

1. If have your e mail, I can send you R Stoppa publications in french for I know he always have done it. I am his pupil and he gave me archives with this aim.

2. I would not dare to say : use inert prosthesis for incisional hernia prevention. Infectious risk would be higher than benefit you get. Actualy there are prospective works done with biological prosthesis and prevention of incisional hernia ( on stoma for exemple) : actualy no EBM answer for this use. So it's so costy that I think wait and see.

Thank you so much!

My e-mail is as follows:

[email protected]

or

[email protected]

As for the biological prosthesis using for the urgent cases, there have been a lot of more or less fruitful discussions at the Researchgate (would you see the links below).

https://www.researchgate.net/post/Is_there_any_data_on_a_correlation_between_visual_Cruse_criteria_and_the_bacterial_count_of_hernial_sac_fluide_for_incarcerated_strangulated_hernia/1

https://www.researchgate.net/post/Do_you_perform_mesh_based_reconstruction_of_abdominal_wall_hernias_with_incarcerated_bowel/1

To take the question one step further, does the shape matter? I would say no, the critical point here is to repair the defect (whatever the shape) in a tension-free way, with an adequate margin of mesh covering all sides of the hernia orifice. Recurrences are often due to incorrect size of mesh or incorrect placement, too close to the defect.

I agree with dr Dimitrios,ultimate result as we all know depends on not the shape of the defect but the adequate coverage of the defect by the mesh.

Thank you all for your scientific inputs - but my question was very specific: why the circular shape of hernial defects, not about techniques to repair them !! I also know the shape of the defect has no bearing on repair technique, I was just curious about the consistency of the shape in all patients. Thanks anyway

I think it is due to stretching forces around the defect and pushing force of the abdominal pressure. But if the defect close a bone its shape can be changed to ovoid such as subcostal hernias.

Some are circular, and some are oval. None is rectangular, quadrangular, or even traiangular.

Incisional hernia defects are circular or almost circular because the abdominal content is  like a fluid so the pressures are equally distributed all over the abdominal wall.

Dr.Tsalis,

It is both a good idea and paradoxical, really physical a point of view: "...because the abdominal content is like a fluid..." . That I have never read or heard before.

Any hernial sac is a solid of revolution from the point of view of geometry. What is the force that make this solid to take its essential shape?

It is the result of the sum of two vectors, the intraabdominal pressure and the resistence of the abdominal defect's edge (see the picture below). As to the resistence, it is more or less clear. However, which medium does serve as the conductor of the intraabdominal force? This question is difficult to answer, but Dr.Tsalis could seemingly find the way to make the right answer.

Loops of the small intestine do not contain any gas under normal conditions, and may be considered as a liquid to some extent. Moreover, this liquid is seemingly not viscous because the mesothelial cells produce the surfactant, a lubricant with the surface tension value of app.25 mN/m (thrice as less comparing to water, see the link below) .

https://en.wikipedia.org/wiki/Pulmonary_surfactant

Defects are most often ellipsoid in shape. Many authors describe the size as a square area. I have proposed an ellipsoidal area size description (which respects the circular defects). However, the quadratic and ellipsoidal area expressions are of course highly correlated in statistical analysis. In my datasets 42% of primary hernias were circular defects and 58% elliptical. In incisional hernia 24% were circular and 76% with elliptical shape.