VICRYLO (Polyglactin 9I o): a new synthetic absorbable suture in ophthalmic surgery

The main function of a suture is to hold the wound edges in apposition until healing is sufficiently advanced for the wound to be self-supporting. In practice, as an absorbable material is losing tensile strength, the wound is gaining strength and at a particular time, which varies according to the tissue involved, equilibrium will be reached. Ophthalmic surgery presents the ideal situation where sutures implanted during operative procedures can be readily observed with regard to their tissue reactivity, biological acceptability, and loss of tensile strength. Characteristics ofknotting, tissue drag, and knot strength can also be assessed. A clinical trial of VICRYL® Synthetic Absorbable Sutures made by Ethicon was set up in three clinical centres: 27 cataract extractions and thirty squint operations were done to determine the safety and efficacy of this material. VICRYL®, or Polyglactin 9IO, is a synthetic absorbable suture which has been synthesized by the co-polymerization of a mixture of purified lactide and glycolide which are cyclic intermediates derived from lactic and glycolic acids. Glycolide and lactide are converted into a polymer in the form of uniform chips which are dyed violet. These chips are melted, and the polymer extruded to form fine filaments. These filaments are strengthened by stretching to allow molecular alignment. The resulting filaments are braided and the braid undergoes a further stretching process to increase further the tensile strength of the resulting suture. Being violet in colour, the suture is easily seen in the wound. The suture material is attached to an eyeless needle, placed dry into a foil package and sterilized by ethylene oxide. The braided VICRYL® is smaller in diameter than the corresponding size of catgut, although its "knot pull strength" is higher (Table I). Knot pull strength is recorded in pounds and is the tension at which a knotted piece of suture material breaks. This strength is always lower than the straight pull value with no knot in the material. In a comparison of VICRYLO, polyglycolic acid, and MERSILENE® it can be shown that VICRYL0 has a higher knot pull strength than any of the other materials mentioned (Table II). Extensive animal work had been performed by Ethicon with VICRYL® to show its safety and efficacy in vivo before release for clinical trial. This work included toxicity and carcinogenic studies, in-use animal work, and metabolic studies using radioactive labelled suture