STAINLESS-STEEL SUTURES
Dr. W. Marvin Mackie, DVM
Owner/Director, Animal Birth Control
Los Angeles, CA

For a very long time, I championed the use of stainless steel as the suture of choice for spay ovariohysterectomy in the dog and cat and for the male dog neuter.  The male cat can be castrated with a  variety of instruments and hand ties that do not require a ligature per se. Although I have not come across any studies on using stainless steel, my years of personal experience have convinced me that it is the best option for routine spay/neuter surgery. 
Suture choices for various procedures tend to evolve and are passed on by tenured surgeons based on their own preference and experience..  Dr. Scott Anderson, Director of Animal Surgical and Emergency Center in West Los Angeles, has been detailing surgical procedures in the monthly Pulse publication for local veterinarians.  His presentation of an OVH in the early 1990s specifically recommended stainless steel for the procedure  and he reaffirmed his position on the subject when I saw him in person in the late 1990s.

The advantages of stainless steel:

·  It has the greatest strength for its equivalent size of any other suture.
·  You can, and should, use a smaller size than you are currently using with any other material, i.e. 5 - 0 and 4 - 0.  Note:  Bulk stainless steel is often listed in the Fr. Gauge, thus 5 - 0 = 34 ga., 4 - 0 = 32 ga. and 3 - 0 = 30 ga.

·  Ties are absolutely secure with only a 2-throw square knot.  Nothing more is ever needed.  It reality, with a soft tissue intra abdominal ligature, i.e. small pedicle or stump, you can do a single throw and kink it back and cut it free.  You have performed a version of a lig-a-clip.  With all other suture material, you need three to four throws. I’ve even seen surgeons make small pig-tails to feel comfortable.

·  When buried, the sutures hold for life.  They are handy in hernia repair; they obviate the need to freshen the edges.  Stainless steel simply does it’s job and after healing is complete, it lies there not bothering anything and not creating any problem for the patient.

·  Stainless steel’s stiffness (memory) can be used to an advantage.  When you let go, the tag end will remain up and exposed where you released it, unlike many of the other materials that wander off or just lie down flat on the patient or hide in the blood!

· The most profound advantage is that it is shockingly inexpensive. The convenient way to order and practice getting comfortable is to purchase B/Braun’s “Steelex” prepared cassettes, 50 meters to a cassette regardless of the size purchased.  Their price is approximately $20 per cassette; about 3.6¢ per ft. (30 cm). Or you can make your own cassettes.  Miltex manufactures stainless steel sutures in quantities by weight of 1 oz or 4 oz  on wooden spools. The 4 oz. spool of 32 ga. (4 – 0)  is approximately 5,760 feet (440 meters) and the 4oz. spool of 34 ga. (5 – 0) is 10,320 feet (789 meters). At $22.00 per spool, both cost much less than a penny a foot!   These products are available from your favorite supplier.

· It has an indefinite shelf life; even if used only infrequently, it will never go out of date.

The disadvantages:

·  In that there is a learning curve, the material is not immediately surgeon friendly. You need to learn how to work with it instead of against it.  You must learn its character and learn to let it flow with your hands similar to the way professional dancers flow and complement one another. The wire won’t adapt to you. You can’t change the fact that if there is a kink formed, you can’t unkink it; it will snag if you try to pull it through the tissue. It has a soft memory of the spool from which it was just pulled, so don’t pull more than seven to eight inches at a time from the spool. We are used to 27" ± from normal pre-packs; however, if you pull 9" to 10", you are inviting trouble and over 10" you are doomed. You just can’t control it at that length. Patience and practice are key.  Ideally, you would be coached by someone who has experience with it.

·  It will cut tissue, but this need not be a concern. It is excellent in cinching down on ovarian and uterine pedicles in cats and smaller and/or immature dogs. The focus must be on the ligation in the estrous uterine stump. The fact that the uterus is often quite turgid is not a help. After you circlage the organ, you need enough pressure to squeeze tight enough and crimp or kink back to set the knot tension in order to prevent uterine artery bleeding. Place your Rochester-Carmalt, then encircle, place the first throw of your square knot, “flash” the Carmalt. Let the uterine body retract just enough to cinch in the just compressed zone left by the now moved Carmalt. When you are cinched to the tension, “set” the tension by crimping the wire enough that it won’t loosen as you finish your square knot. Then, simply cut free exactly on top of the knot. It won’t come undone.

• The wire is harder on the cutting edges of the Olsen Hegar needle holders.  With care and by not always cutting in the “sweet spot”, i.e. center one-third, the cutting edges will dull out at the same time as the tungsten carbide needle holding jaws are worn down.  When my needle holders begin cutting the suture poorly and/or the carbide jaw grips are not holding the needle secure, I send them to Spectrum (800-444-5644) for the refurbishing needed.  Spectrum refurbishes their own brand at no charge for the life of the instrument or charge only $18.50 for other brands.

• You have to thread a needle to use it.  If you are using any other material not packaged with a swaged on needle, this will be easier once you get the hang of it.

Frequently asked questions:

Q: Does the stainless steel cut through all the tissue to cause a loss of the tissue being tied off?

A: Rarely. It could happen but your judgment will alert you until your experience guides you.

Q: What sizes do you use?

A:

Q: What skin closure do you use?

A: 100% stainless steel sub dermal (sub-Q).  Do not use as an intra dermal.  The   number of stitches depends on the length of your cut.  Try to limit your sub dermal bites to 1 ½ cm.  This is often the most difficult to perform and get to look correctly, and it is the part that shows!  Patience and practice; remove and replace. Adding the occasional external, surgical adhesive may help augment and improve appearance.  It may take a few hundred closures to become proficient.

Q: How do you prepare the stainless steel in your cassette?

A: The “Steelex” comes prepared and ready to use in a standard fashion.  If you want to use  the Miltex spools and prepare your own then you need a ½ pint (8 oz) wide mouth canning jar and lid (Kerr-order number 70610-00 500 for a box of nine, Mason or Ball), a metal punch set or drill with bit set to make a hole in the lid and a rubber stopper (harvest from any used vial).  Insert the stopper into the lid, place the stainless steel in the jar and you have your cassette.  Continue to assemble thusly:

1.     Place a 20-ga needle through the rubber stopper from top down inside.

2.     Carefully hold the spool of steel so that as you cut the end that is stapled to the   wooden spool so that it does not spring to unwrap itself when you free it.

3.    Thread the wire end up through the 20-ga needle in the stopper.  Leave the needle in the stopper.

4.     Place spool in jar and replace lid to normal position.  Do not tighten!  Otherwise, during autoclaving, you will seal the lid as in the canning process and if you need to remove the spool later to rethread, you will have trouble removing the lid. 

5.     Date the autoclave indicator tape and place it on the glass part of the jar.

6.     Leaving the needle in the stopper with the wire out through it, autoclave as usual.  The changing pressure inside the jar is equalized naturally through the 20 ga. needle

7.     After the jar has cooled, remove the needle.  The rubber stopper holds the wire until you need it.  The contents are always sterile.

Q: Which suture needles are best suited for stainless steel work?

A: All the sizes I use are 3/8 curved reverse cutting.  Each surgical pack contains  one #14 and #12.  I use the #14 for the 5 – 0, 34 ga. and the #12 for the 4 – 0, 32 ga. In cold sterile solution, I keep a few #10s for use with the 3 – 0, 30 ga. for large dogs  and for the occasional very small finesse situation, a #16.  I’ve used Anchor needles throughout my career.  They cost about $1.00 per needle in packs of 6, but are very good and I autoclave and reuse them.  Be sure to detach the unused stainless steel piece from the needle.  It is much easier for the surgeon to do than for the tech and guarantees it won’t be missed.

HAPPY SNIPPING AND CLIPPING!