Biomedical subjects
Publications and source records attributed to F Dieval.
Performed since the 1950s, vascular grafting has opened modern era of vascular surgery. Autologous venous grafts are of first choice for revascularisation of small arteries. Synthetic grafts are mainly modelled using microporous polytetrafluoroethylene or terephtalate polyethylene. These prosthesis are mainly used for revascularization of medium and large size arteries.
OBJECTIVES: To investigate mechanisms of textile failure in explanted human aortic endoprostheses. MATERIALS AND METHODS: Endoprostheses (n31) underwent optical and scanning electron microscopy, filament dynamometry, and saturation index measurement. RESULTS: The macroscopic lesions observed in the Stentor and Vanguard devices were holes at the extremities of the stents and slipping of the warp yarns at the level of sutures or of the longitudinal seams. The macroscopic lesions observed in AneurX endoprostheses were holes, slipping of the warp yarns and ruptures of the ligatures. The macroscopic lesions observed in the two Talent endoprostheses were sections of fibers at the level of the suture holes and few areas lesions of wear, with sometimes holes at the contact of the stent extremities. Stentor, Vanguard and AneurX all demonstrated low saturation indexes of the fabric (44-59%) with an important anisotropy. Whereas the Talent endograft demonstrated a high index of saturation (124-131%) with a low anisotropy. We did not demonstrate significant polymer degradation in any of the endoprostheses. CONCLUSIONS: It is essential to take into account the saturation index to optimally choose a woven textile for the construction of an endoprosthesis since this property of the textile may contribute to explain the macroscopic lesions observed. We did not observe significant polymer degradation by filament dynamometry but further studies are needed to confirm these data.
OBJECTIVES: Previous explant retrieval studies have shown ruptures occurring on the remeshing line and the guide line of two types of warp-knitted grafts. The aim of our study was to characterize the mechanisms these ruptures. MATERIALS AND METHODS: We performed an in vitro study of the mechanical and chemical characteristics of virgin prostheses. We studied 2 virgin polyester warp-knitted grafts models: the Cooley Double Velour and the Microvel Double Velour constructed by Meadox (USA), using the following techniques: characterization and de-knitting of the textile structure, circumferential tensile strength, filament dynamometry, critical dissolution time of the filaments and scanning electron microscopy. RESULTS: Both prostheses were constructed in the same way but the texturized yarns of the Cooley graft included twice as many filaments (54) than the Microvel (27). There was more adsorbed tension in the Cooley structure than in the Microvel. The circumferential tensile strength test demonstrated that the Cooley graft always ruptured on the remeshing line and the Microvel graft always ruptured at the interface between the remeshing line and the standard line. Filament dynamometry demonstrated a heterogeneous behavior of the filaments inside the yarns, mainly at the remeshing line of the Cooley graft (27.1 cN/tex +/- 11.5% versus 26.1 cN/tex +/- 2.2% for the guide line and 28 cN/tex +/- 6.7% for the standard knit). Critical dissolution time of the filaments was significantly lower for the Microvel grafts (2.5 sec versus 17.2 sec for the Cooley). CONCLUSIONS: Rupture of knitted polyester prostheses are probably an underestimated phenomenon. They may occur at specific areas of the graft. Further studies are required to determine whether all grafts of this type are at risk.
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AIM: The purpose of the study was the characterization of a type of rupture occurring on warp-knitted polyester vascular prostheses. MATERIALS AND METHODS: We studied 20 cases of warp-knitted polyester vascular prostheses that were explanted from humans that showed a longitudinal rupture as a part of a collaborative retrieval program. All the prostheses were immediately fixed in a 10% formaldehyde solution after their explantation in the operating room. The clinical data of these cases were recorded. The explants were photographed, washed to eliminate the surrounding tissues, and photographed again. The ruptures were characterized with macroscopic examination, optical stereomicroscopy, and scanning electron microscopy. RESULTS: The mean duration of implantation of the prostheses was 16.0 +/- 3.3 years (range, 9-20.7 years). The prostheses were Cooley Double Velour (n = 15) and Microvel Double Velour (n = 5). There were 16 aortobifemoral bypass grafts, 1 aorto-biiliac, 1 aorto-aortic, 1 iliofemoral, and 1 axillobifemoral. The longitudinal ruptures occurred on two specific parts of the prostheses: the guide line (6 cases) and the remeshing line (11 cases). In three cases both lines were affected. Scanning electron microscopy showed major degradation of the trilobar filaments of the velour and gradual ruptures of the flat filaments of the remeshing and guide lines. CONCLUSIONS: In this study, we have identified a specific mechanism of late (9-20 years) longitudinal rupture of knitted polyester prostheses consisting of degradation of the polyester filaments along the remeshing and guide lines that run the length of the graft.