Needles 05 Parts

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Needles 05 Parts

This subsection has text and images from an interactive multimedia training program on basic surgical skills 
called PrimeSkills in Surgery.
You can use this subsection on its own or follow the whole program (further details at the end of this 
subsection).


101834100-EXAMPLES-OF-NEEDL.jpg


Curve

Cross Section

Material

Size

Point

Swage

Example


Curve


Unlike a domestic needle, most surgical needles are curved. A few are straight.

101721000-3-needles---curve.jpg


The curve allows the needle to pass down into the tissues and to come out again along a curved track.


A straight needle just becomes embedded in normal tissues, unless they can be held up. e.g. skin edges.


A 3/8 curve is the most common shape.


A 1/2 or 5/8 curve needle will be useful in a small space.


A 1/4 curve or a straight needle is adequate if there is no shortage of space. e.g. skin edges.


Compound shapes include a J needle for the confined space of a femoral hernia repair for example, and a ski


shape which some surgeons prefer to a straight needle.



Cross Section


The domestic needle has a round Section.


This is ideal for a straight needle held in the hand where a cutting cross section would damage the cloth.


The simplest surgical needles are basically round bodied so that they pass through the tissues without cutting.


The tissues are separated by the needle.


They then grip the suture to provide a leak free stitch.


Cutting needles, as the name suggests, cut through tough tissues.


They usually have a triangular cross Section.

22010.JPG


The apex of the triangle is on the inside of the curve and forms a very sharp ridge in the front part of the


needle.


This ridge cuts through tough tissue on the inside of the needle track much better than a round bodied needle.


The difference is most noticeable when stitching skin.


Some needles have the sharp ridge on the outside of the curve(reverse cutting).


This makes the needle stronger than a normal cutting needle.


The suture will pull on the inner uncut side of the track with perhaps better healing.


In addition, surgical needles have a flattened middle section.


This is where the jaws of the needle holder grip firmly without allowing swivelling or rotation.



Material


Needles are made from steel alloys, selected to hold a very sharp point for once only use.


They are designed to bend, as in this photograph, rather than to break, when over stressed.

101723000-NEEDLE-MATERIAL.jpg


The strength of the needle is designed to match the use to which it is put.


There are no simple ways of demonstrating the strength apart from testing the needles to destruction.


You will be doing this on the work bench in a few minutes on the needle Skid pan


It is much better to bend and break a few needles on the work bench than during an operation.


Size


The size is measured in millimetres in length when the needle is straightened.


The needle should be long enough to:


Pass through the tissue.


Show enough length at the far side of the wound to be grasped by the needle holder or dissecting forcep.


This is even after it has slipped back into the tissue a millimetre or two (pop back).



Point.

101725000-NEEDLE-POINTS.jpg


The point of a needle is usually sharp.


Exceptions are blunt needles for stitching liver, and special needles to prevent needle stick injuries from


high risk patients such as HIV and Hepatitis B positive patients.


The non-cutting needle has a tapered point to force the tissues apart.


Cutting needles have some form of trocar point to make the cut.


This may be incorporated into the triangular section of the body of the needle.



Swage


In a domestic needle, the thread passes through the eye of the needle.

101710000-Hand-held-needle.jpg.


In contrast, a surgical needle has the suture embedded in its blunt end.

101726000-SWAGE.jpg


The junction is called a swage.


This reduces the trauma to the tissues, because the suture passes through without being looped.


The friction of the passage of the needle and suture is reduced, giving more control to the surgeon and less


damage to the tissues.


The swage, however, may be the weakest part of the needle/suture complex.


It will give way without warning if the pull on the needle exceeds the strength of the swage.


The surgeon needs to know how strongly the suture needs to be pulled to draw the tissues together or to make a knot.


Also he needs to know how strong the swage is.


If the required suture pull is higher than the strength of the swage, the surgeon must take steps to protect the


swage.


The exercises will help to the surgeon on these points.



Example


A W9890 needle:

101727000-W9890.jpg


This is a 30mm 3/8 curved lance pointed needle with a flat part running to within 8mm of the point.


The whole needle is 30mm long.


With the needle holder two thirds of the way back from the needle, the needle will bend at a pressure of 300g.


With the needle held at its centre, the needle will bend at a pressure of 1200g.


The usual pressure to get through skin is 300g so that the needle will start bending if held in the usual recommended position two


thirds of the way back from the point.


Beginners should hold the needle further forward.


The suture will lose its zigzags with a pull of 1500g.


The swaging will only stand a pull of 1200g.


Therefore the swage needs to be protected when pulling the suture to remove zig-zags.


Next subsection, click on Needles 06 How needles work
Last subsection, click on  Needles 04 Introduction 
Surgical Education and Training page, click on Surgical Education and Training
Whole program on WikiSurgery, click on PrimeSkills in Surgery
Whole program on CD-ROM, click on Michael Edwards