Resultados. Histológicamente, los implantes del grupo I se integraron totalmente dentro de una masa de tejido cicatrizal denso y desorganizado. En el grupo II se observó en la zona de prótesis resuturada el reestablecimiento de tejido neoformado, también denso y desorganizado, similar al que se observó en el grupo I. Los valores de resistencia a la tracción a los 3 meses postimplante de polipropileno (grupo I) (media, 34,98 N) fueron similares a los observados a los 90 días posrealización de las relaparotomías en los implantes del grupo II (media, 34,74 N) (test de la U de Mann-Whitney p < 0,001). La rotura de las tiras no se produjo en las zonas resuturadas ni en las interfases de anclaje de la prótesis a la pared, sino que se produjo en el mismo tejido receptor, en zonas próximas a las mordazas del tensiómetro.
Conclusiones. La realización de relaparotomías a través de prótesis de polipropileno previamente implantadas e integradas en la pared abdominal no conlleva una merma de la resistencia biomecánica de éstas tras el establecimiento de tejido cicatrizal entre los márgenes de la zona resuturada, siendo este último proceso similar al que se observa tras el implante inicial del polipropileno
Material and methods. Defects measuring 7 * 5 cm, involving the full thickness of the abdominal wall, were made in 12 male New Zealand rabbits weighing between 1,800 and 2,000 g, and subsequently repaired with PL prostheses (Marlex®) of the same size. Two study groups were established: group I (control group; n = 6) consisting of recipients of PL implants that were sacrificed 90 days later; and group II (experimental group; n = 6) in which, 90 days after PL implantation, the animals underwent repeat longitudinal midline laparotomy cutting through the prosthesis, which was subsequently repaired by means of a running suture using 4/0 PL. These animals were sacrificed 90 days after the second operation. Samples were taken of the prostheses, the newly formed tissue in resutured areas and the interfaces anchoring the prostheses to abdominal wall for study under light and scanning electron microscopes. In addition, 2-cm wide strips including both the resutured prosthesis and the tissues attaching them to abdominal wall were subjected to a biomechanical trial using an Instron tensile tester. The values obtained were evaluated by the Mann-Whitney U test.
Results. The histological study of group I implants showed them to be totally integrated into a mass of dense, disorganized scar tissue. In group II, newly formed tissue, which was dense and disorganized as in group I, was observed in the area of the resutured prosthesis. The resistance to tensile testing 3 months after the implantation of PL in group I (X = 34.98 N) was similar to that observed 90 days after repeated laparotomy in the group II implants (X = 34.74 N) (Mann-Whitney U test: p < 0.001). The strips did not tear at the level of the resuture or the interface, but at the level of the recipient tissue near the clamps of the tensile tester.
Conclusions.. Repeat laparotomy performed in previously implanted prostheses made of PL that are integrated into abdominal wall does not reduce the biomechanical resistance of the implants once scar tissue has developed between the resutured borders, a process which is similar to that observed after the initial implantation of PL.