Tie hard 2- an in-vitro comparison of first throw tension holding in twisted v straight-first throws; using Polyglycolic acid (Dexon S), Polyglactin 910 (Coated Vicryl).

OBJECTIVE

To compare the first throw tension holding properties of twisted versus straight first throws in two commonly used Oculoplastic braided absorbable sutures.

DESIGN

An in-vitro experimental model.

METHODS

Variable loads were applied to the first double throw of a surgical knot - either in straight-line configuration or twisting the knot using both 6/0 Polyglycolic acid (Dexon S) and 6/0 Polyglactin 910 (Coated Vicryl). Each suture was tested to the point of knot slipping and the critical tension recorded. Two variations of the experiment were undertaken: Experiment 1 - two metal loops were brought together by the test suture, experiment 2 - two strips of tissue (Permacol - cross-linked porcine dermal collagen) were brought together by the test suture.

RESULTS

Experiment 1 straight: Polyglycolic acid 12.2g (11-13.5), Polyglactin-910 2.5 g (2.5- no range). Experiment 1 twisted: Polyglycolic acid 13.33 g (10-15), Polyglactin 910 3 g (2-5). Experiment 2 straight: Polyglycolic acid 33g (30-35), Polyglactin 910 25g (25 - no range). Experiment 2 twisted: Polyglycolic acid 35 (30-40), Polyglactin 910 25g (20-30).

CONCLUSIONS

Twisting the suture adds only a modest increase in first throw knot security. Polyglycolic acid (Dexon S) braided absorbable suture has significantly better first throw knot security when compared with Polyglactin-910 (coated Vicryl). This is an important property when suturing tissues under tension as it minimises slippage before the locking throw is tied.