Differences in polypropylene shrinkage depending on mesh position in an experimental study.

BACKGROUND: Polypropylene (PP) mesh is one of the most frequent materials used in hernia repair. We have experimentally evaluated the shrinkage of PP mesh depending on the place of implantation. METHODS: In 15 New Zealand rabbits a muscular defect measuring 3 x 3 cm was created in both pararectal sides of the abdominal wall. The defect was repaired using a PP mesh measuring 5 x 3.5 cm that was placed in the right side in the sublay location and in the left side in the onlay location. Five animals were killed on the 30th, 60th, and 90th postoperative days. Macroscopic measurement and microscopic study of the prosthesis-host tissue interfaces were performed. RESULTS: One rabbit was killed because of severe infection in the onlay mesh. Another 2 infections were tolerated in the onlay mesh side. All the prostheses were integrated in the host tissue at death. In the macroscopic evaluation the mesh areas were reduced by 25.92% on the 30th day, by 28.67% on the 60th day, and by 29.02% on the 90th day. The mesh shrinkage was greater in the onlay group than in the sublay group at the 3 time intervals. More inflammatory leukocyte and mononuclear responses also were seen in the onlay group. CONCLUSIONS: These observations support the theory of PP mesh shrinkage as a consequence of the incorporation of the biomaterial to the scarring tissue. This shrinkage is significantly more intense if the meshes are placed in the onlay position.

[Surveillance of shrinkage of polypropylene mesh used in the repair of ventral hernias]. / Seguimiento de la contracción de las mallas de polipropileno empleadas en la reparación de eventraciones.

INTRODUCTION: Polypropylene (PP) mesh is one of the most frequently used materials in the surgical repair of ventral hernias. Despite the widely recognized ability of PP to integrate into the host tissue, these meshes may shrink during the healing process in the patient. OBJECTIVE: To quantify polypropylene mesh shrinkage. PATIENTS AND METHOD: A radiological follow-up study was performed in 23 consecutive patients who underwent surgery for midline ventral hernias with diameters of at least 5 cm. PP meshes were marked with titanium clips at the ends of their longest transverse and longitudinal axes. X-rays were performed on the first postoperative day and at 1, 3, 6 and 12 months. The distances between clips were measured and the area of the mesh was calculated. RESULTS: Seventeen women and six men underwent surgery. In nine patients the mesh was placed on the prefascial space (onlay) and in 14 in the subfascial space (sublay). There were four seromas in patients with mesh placed with the onlay technique. The reduction in the calculated area was 12% at 1 month, 24% at 3 months, 29% at 6 months and 34% at 12 months. CONCLUSIONS: PP mesh provided excellent clinical results. Radiological surveillance revealed substantial shrinkage, mainly in the first 3 months after implantation.