SMB Atraumatic Channel Needle are manufactured from superior quality
martensitic grade stainless steel, conforming to AISI 420, equivalent to EN
56D or Werkstoffnummer 1.4031. Needles are hardened and tempered to a
controlled hardness of VPN 525-625, which ensures adequate stiffness to
withstand the pressure encountered in the suturing procedure while
eliminating brittleness.
The composition of this grade of stainless steel is as follows:
| C |
0.32-0.40% |
| Si |
1.00%max. |
| Mn |
1.00%max. |
| p |
0.04%max. |
| S |
0.03%max. |
| Ni |
0.60%max. |
| Cr |
12.5-14.0% |
The Atraumatic needles are polished to minimize micro-asperities on the
surface by a series of mechanical polishing operations followed by
electro-polishing. This reduces tissue drag during the suturing operation to
a minimum
All Atraumatic needle points are machine-honed on special purpose machines
to ensure the highest standards of sharpness of the point. The point
profile, both in the case of taper point needles and cutting edge needles,
is specially designed to be a
convex profile, which minimizes tissue penetration force while
preserving the strength of the needle point. This type of point profile is
also resistant to 'feathering'.
In the case of cutting edge needles, the widest part of the point is just
before the shank of the needle, thereby minimizing tissue drag once the
point has penetrated. This type of point configuration is also referred to
as a 'cobra head' point.
In channel-type atraumatic needles, the channels are cold forged to close
tolerances to ensure that final dimensions of the channel correspond to the
suture diameter. Furthermore, the needles manufactured are uniformly
heat-treated. Most manufacturers anneal the channel end to avoid cracking
during crimping. The metallurgy of needles permits a hardened channel to be
crimped satisfactorily without any problems; this results in uniform
metallurgy of the needle and thereby improved corrosion resistance as well
as resistance to bending.
A strict Quality Control protocol is followed at each stage of manufacture.
The test done include point sharpness testing, which is carried out on a
specially designed digital sharpness comparator, which measures the force
(in grammes) required for penetrating of the needle point through a special
polyurethane diaphragm. The polyurethane material is selected as it closely
mimics the characteristics of human skin.
The stiffness of the needles is also measured with a special digital
tester, which enables the Force Vs Displacement of the needle to be plotted
and which also determines whether the needle has regained it's original
shape without any permanent set having taken place.
Random samples of atraumatic needles' are drawn and test-attached with a
suture after which they are subjected to pull-out strength testing in a
digital tensilometer to ensure that USP standards are met.