How many ounces it takes to pull
out the sutures immediately
performed by Nicanor Isse MD
How many ounces of resistance
it takes before the suture migrates
if the sutures are nor fastened
by Nicanor Isse MD
|Malar repositioning force needed|
|Conventional barbed sutures|
|New Silhouette Suture|
|Conventional barbed sutures|
|Sutures with knots only|
|New Silhouette sutures|
Barbed sutures are manufactured by cutting barbs (slices) into the polypropylene suture material.
One first has to understand the structure of the polymer polypropylene. Several scientific and engineering data will show the molecular structure of extruded polypropylene. If one cuts barbs (slices) into the extruded polypropylene it will weaken the integrity of the polypropylene considerable. The polypropylene consists of linear molecular strands. Picture yourself a bunch of liner strands forming a 2-0 dia (.012) suture. You would think that if you start with a 2-0 dia (.012) and slice it 50% deep to create a barb, the polypropylene strand would have the strength close to a 4-0 dia (.007) suture. If you slice it 35% deep it would have the strength close to a 3-0 dia (.009) suture. This is not true if you look at the test results below. This is the reason why conventional barbed sutures break.
After the barbs (slices) are formed they serve the purpose of anchoring on soft tissue. When the suture is placed inside the patients face, the sharp barb then anchors on the tissue. It should be understandable that some of these barbs fold back when stresses are applied when the suture is pulled in the opposite direction of the barbs. If too much force is used to pull the suture in the opposite direction the barbs then fold back or even strip back. Like peeling a banana if you will. It is easy to peel the banana in the same direction along the shaft then it is to pull the banana skin straight up. Just imagine having to pull the suture out in the opposite direction. Since the barbs will dig even deeper into the tissue when trying to pull them out all barbs always fold back or even break off.
When the conventional barbed sutures are successfully placed underneath the skin, the barbs which will have anchored on the tissue will form sort of a spring action. The further the barb opens up the more of a spring action it develops. Just try opening or closing the barb with your fingers after it is cut into the suture. It will spring back to its original shape.
This typically explains suture migration if the barbed suture breaks. The barbs all want to close and the suture always migrates in one direction.
When the very point of the barb anchors, only that part of the tissue is being displaced. When another barb is opposite the previous one (other side of the suture) then only that tissue is being displaced, causing a dimpling effect. How can we be sure that the barbs are facing in the proper rotational direction so one can lift tissue in a uniform way?
Last but not least is the color of the suture. When the suture breaks or barbs strip and break off, it is very hard to find the remnants in the patients face. When the color of the suture is clear, it makes it even harder then when the color is blue.
Pull test conducted to show breaking point strength in ounces using a certified tension gauge. (Extech 475040)
2-0 suture .012 dia (no barbs) 133, 145, 137, 137, 141, 135
3-0 suture .009 dia (no barbs) 76, 80, 77, 75, 75, 80
4-0 suture .007 dia (no barbs) 45, 43, 46, 48, 46, 40
2-0 suture (with barbs cut 35 % deep) 47, 45, 59, 59, 52, 50
2-0 suture (with barbs cut 50 % deep) 27, 30, 24, 25, 32, 30
3-0 suture (with knots only) 44, 38, 37, 41, 38, 40