Implant materials are increasingly being used in an effort to reduce recurrence after prolapse repair with native tissues. Surgeons should be aware of the biology behind both the disease as well as the host response to various implants. We will discuss insights into the biology behind hernia and abdominal fascial defects. Those lessons from "herniology" will, wherever possible, be applied to pelvic organ prolapse (POP) problems. Then we will deal with available animal models, for both the underlying disease and surgical repair. Then we will go over the features of implants and describe how the host responds to implantation. Methodology of such experiments will be briefly explained for the clinician not involved in experimentation. As we discuss the different materials available on the market, we will summarize some results of recent experiments by our group.

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The biomechanical behaviour of the tested lightweights does not mimic that of native controls. Weight reduction does not prevent shrinkage.

Please cite this paper as: Ozog Y, Konstantinovic M, Werbrouck E, De Ridder D, Mazza E, Deprest J. Persistence of polypropylene mesh anisotropy after implantation: an experimental study. BJOG 2011; DOI: 10.1111/j.1471‐0528.2011.03018.x. Objective  To determine whether anisotropy persisted after incorporation into the host, using a standardised rabbit model for abdominal wall reconstruction. Design  Investigator‐initiated prospective‐controlled experimental study. Setting  Centre for Surgical Technologies, Medical Faculty KU‐Leuven. Sample  Fifteen New Zealand White rabbits. Methods  In each rabbit, four full thickness primarily repaired abdominal wall defects were covered by a 4 × 5‐cm Prolift+M implant (Johnson & Johnson, Norderstedt, Germany), either with the stiffest (n = 6 rabbits) or most elastic (n = 6) direction parallel to the body axis. Prolift+M contains 32 g/m2 polypropylene, reinforced with polyglecaprone fibres. Harvesting was performed after 30, 60 and 120 days (n = 2 each time‐point). The abdominal wall of three unoperated rabbits was used as negative control. Main outcome measures  Contraction, compliance and maximal strain and stress determined by uniaxial tensiometry. Results  Anisotropy properties persist at lower, more physiological displacements, but not at higher displacements. The stiffness of a mesh‐augmented repair in the lower strain range remains above that of native tissue. Eventual mesh contraction was limited to 4.3%. Conclusions  Anisotropic properties of Prolift+M persist in vivo and shrinkage is minimal. Compliance of mesh‐augmented repair remains less than that of native tissue. The functional consequences of this remain to be studied.

The addition of polyglecaprone fibers did not compromise the biomechanical properties nor did it prevent vaginal extrusion and contraction. The latter as well as some other limitations preclude the rabbit vagina to be a suitable model for biomechanical testing.

SIS augmentation of native tissue repair does not increase strength. Replacement of abdominal wall by SIS is equally strong when compared to the SIS-augmented group; however, materials preferably rupture at the site of the implant itself.

In experimental conditions, sufficient strength was obtained only after 3 months, and PP containing constructs appeared as the strongest though reconstruction with Pelvicol showed comparable outcomes. Lower values for strength of non-cross linked and porous collagen materials are questioning their efficacy for pelvic floor reconstruction.

Aim: To investigate the biomechanical properties of porous collagen matrices in a rat abdominal wall defect model. Study Design: 112 rats were implanted with non-cross-linked InteXèn LP, cross-linked Pelvicol, and two investigational acellular collagen matrices (ACMs) sterilized either with ethylene oxide (ACM ETO) or γ-irradiation (ACM GI). After 14, 30, 90 and 180 days, 7 animals per group were sacrificed to document adhesions, herniation, infection, stress resistance and histology. Results: The 2 sterilization methods did not cause measurable differences between ACMs. Pelvicol was more resistant than ACMs but showed degradation at 90 days without loss of strength. InteXèn LP became remodeled as a thin fibrous scar and was more resistant at all time points; however, some animals developed bulging. Conclusions: Non-cross-linked InteXèn LP became remodeled by 180 days with remarkable stress resistance. Despite cross-linking Pelvicol showed degradation. Comparable but investigational ACM explants were less resistant without morphologic differences to explain this.