Product Manual

apposition of the wound edges. The force required to advance the knot is called
knot rundown force. Once meticulous approximation of the wound edges is
achieved, the surgeon prefers to add one more throw to the two-throw knot so
that it does not fail by slippage.
The magnitude of the knot rundown force is influenced considerably by the
configuration of two-throw knots. 24 Knot rundown of the surgeon’s knot
square (2=1) generates sufficient forces to break the knot. In contrast, knot
rundown of square (1=1), granny (1x1) and slip (S=S, SxS) knots occurs by
slippage. For comparable sutures, the mean knot rundown force for square knots
is the greatest, followed by that for the granny (1x1) knots, and then the slip
(S=S, SxS) knots.
Failure of the knotted suture loop may be the result of either knot slippage or
breakage, suture cutting through tissues, and mechanical crushing of the suture
by surgical instruments. Initially, the knotted suture fails by slippage, which
results in untying of the knot. All knots slip to some degree regardless of the
type of suture material. When slippage is encountered, the cut ends (“ears”) of
the knot must provide the additional material to compensate for the enlarged
suture loop. When the amount of knot slippage exceeds the length of the cut
“ears,” the throws of the knot become untied. In general, surgeons recommend
that the length of the knot ”ears” be 3mm to accommodate for any knot slippage.
3 Dermal sutures are, however, an exception to this rule. Because the “ears” of
dermal suture knots may protrude through the divided skin edges, surgeons
prefer to cut their dermal suture “ears” as they exit from the knot. It must be
emphasized that knot security is achieved in a knot with “ears”with one more
throw than in a comparable knot whose “ear” length is 3mm.
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