Terminology

Hi,

I am investigating the ways in which knots in suture material fail. (I am a
surgeon.) I am familiar with breakage at the knot and failure by slippage
of the knot when under load. But is there a term used to describe the
situation in which a knot fails by "unravelling" or coming undone when it is
unloaded, especially if shaken about ? Interestingly the surgical
scientific surgical literature has fairly detailed data on failure by knot
slippage and breakage under load but I have never seen any reference to
"unravelling" of unloaded knots nor any standard way to measure the
propensity for this to occur.

I would be grateful for any advice or pointers on this.

Doug Turner

Hi Doug,

Be aware that unloaded shaking failure can be markedly affected by
environment. Water can make slack knots fall apart faster than they
might when moved in a mostly dry environment.

Further, when you notice knots shaking loose in patients, does the
knot actually fall apart or is it just unacceptably loose? I'm sure
the tissue gives way over time with repeated flexures and could
contribute to eventual looseness. I guess it'd depend on the force on
the suture, the skin, and the suture diameter.

On last thing, I know bio-compatible adhesives exist that are used for
closing some wounds. Perhaps if no other practical solution can be
found for the insecurity of certain suture material, a drop of
adhesive might help.

Cheers,
roo

"Doug" wrote in message ...
Hi,

I am investigating the ways in which knots in suture material fail. (I am a
surgeon.) I am familiar with breakage at the knot and failure by slippage
of the knot when under load. But is there a term used to describe the
situation in which a knot fails by "unravelling" or coming undone when it is
unloaded, especially if shaken about ? Interestingly the surgical
scientific surgical literature has fairly detailed data on failure by knot
slippage and breakage under load but I have never seen any reference to
"unravelling" of unloaded knots nor any standard way to measure the
propensity for this to occur.

I would be grateful for any advice or pointers on this.

Doug Turner

(roo) wrote in
m:

...Water can make slack knots fall apart faster than they
might when moved in a mostly dry environment.

Hi roo,

Thanks for your comments. The formal testing that manufacturers do on
suture material is sometimes done "dry" and sometimes wet, usually using
a salt solution, sometimes serum(a blood component).


Further, when you notice knots shaking loose in patients, does the
knot actually fall apart or is it just unacceptably loose?

Some times they fall apart completely :-( (The patients have this
expression also!)

On last thing, I know bio-compatible adhesives exist that are used for
closing some wounds. Perhaps if no other practical solution can be
found for the insecurity of certain suture material, a drop of
adhesive might help.

Yes, but not in common use as the suture is usually tied in a wet
environment ie covered in blood. There is some experimenting with heat
welding of the knots but not in general use to my knowledge. Metal
staples can be used for some things but in general tying knots by hand
is still the most common way of joining thins up again.

I'm still comming to grips with the fact that there appears to be so
little science in the "comming undone" aspect of knots. My professional
life is based on tying secure knots and I go to courses to learn how to
tie them the hard way (like inside a black box using pushers and
graspers inserted through 1/4 inch pipes using camera/TV screen to see
what you are doing). I'm frustrated that the whole subject of how or
why certain materials have a propensity to come undone seems entirely
neglected.

Doug Turner