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  • Flanged Polypropylene Sutures in Scleral Fixation: Biomechanical Testing

    By Lynda Seminara
    Selected by Richard K. Parrish II, MD
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    Journal Highlights

    American Journal of Ophthalmology, October 2021

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    Yuan et al. performed biomechanical analyses of the polypropylene belt loop technique for scleral fixation of IOLs, using common materials and variations of them, and they compared their findings with those of studies that include long-term clinical data. They determined that the current use of flanged 5-0 and 6-0 polypropylene for scleral fixation is secure and that flanged 7-0, but not 8-0, polypropylene is a viable smaller-gauge alternative for this technique.

    For this study, the flange disinsertion forces of polypropylene sutures using human cadaveric sclera and a tensile testing machine were compared with the breaking strengths of 9-0 and 10-0 polypropylene. The researchers also assessed modifications in suture gauge (5-0, 6-0, 7-0, or 8-0), amount of suture cauterized (0.5 or 1.0 mm), and sclerot­omy size (27, 30, 32, or 33 gauge). In addition, four patients who underwent belt-loop intrascleral fixation with a 6-0 polypropylene/30-gauge needle or a 7-0 polypropylene/32-gauge needle were evaluated.

    In general, the breaking force of each suture coincided with its cross-sectional area. Flange size decreased with smaller-gauge sutures, and smaller gauges had lower pull-through forces. The average forces to disinsert a flange created by melting 1.0 mm of 5-0, 6-0, 7-0, and 8-0 polypropylene sutures from human cadaveric sclera via 27-, 30-, 32-, and 33-gauge needle scleroto­mies were 3.0 ± 0.5 in newtons (N), 2.1 ± 0.3 N, 0.9 ± 0.2 N, and 0.4 ± 0.1 N, respectively. When only 0.5 mm of suture material was melted, flange disinsertion forces were 72% to 79% lower (p < .001) and did not exceed the breaking force of 9-0 or 10-0 polypro­pylene for any suture size tested. In comparison, the breaking strengths of 9-0 and 10-0 polypropylene were .91 ± .04 N and .52 ± .03 N, respectively. In the patients with belt-loop fixation, best-corrected visual acuity was 20/32 before surgery and 20/21 afterward. Six months postoperatively, there was no evidence of flange extrusion.

    The authors postulated that the flanged belt-loop technique is a bio­mechanically sound method of scleral fixation when using 1.0-mm flanges of 5-0 to 7-0 polypropylene and 30-and 32-gauge sclerotomies. However, they said, 8-0 polypropylene and 0.5-mm flanges of any suture gauge likely would compromise long-term stability.

    The original article can be found here.