What do astronauts do...

Comments 2 ; Posted 12 years ago

By Engelbert Hanzal

What do astronauts do to keep their chess pieces in place when enjoying the King's game aboard their space-ships and stations in zero-gravity?

They use the ingenious invention of Swiss engineer George de Mestral called Velcro, who on coming home from a walk one day in the early 1940ies became curious enough about the mechanism that had attached some burdock seeds so efficiently to his dog's fur that he studied them under a microscope. The secret lay in a tiny hook and loop mechanism. Each attachment alone was very weak but an abundance of those weak links summed up the strength of the total mechanism to become very strong indeed. A modern Nylon Velcro-strip of approximately 5sqcm reportedly can support a 75kg person hanging from the ceiling (but please don't try this at home!).

The need for midline abdominal incisions has declined with the surge in laparoscopic techniques but still remain indispensible in advanced ovarian cancer and other complex surgery in gynaecology. While providing excellent access to the pelvis and the abdomen its biggest disadvantage is significant immediate and long-term morbidity. Even after many years incisional hernias can crop up in up to 20% of cases - yes, that's every fifth patient!

You may argue that this will be dependent on the right surgical technique for wound closure, but I challenge you on that. A systematic review from 2010 found that continuous suturing using slowly absorbable sutures gives better results than an interrupted suturing technique with rapidly absorbable material (1). Most surgeons today are applying this technique incorporating all abdominal (except the subcutaneous and skin) layers in a mass-closure or "far-far-near-near" (modified Smead-Jones) fashion to achieve a suture length (SL) to wound length (WL) ratio of at least 4 (ie. the suture must be 4 times longer than the incision, otherwise the risk of herniation is threefold). Often this is performed with an 0 or 1 sized polydioxanone (PDS) loop on a 30 mm to 60 mm semicircular needle to facilitate "big bytes" (ie. at least 1cm lateral to the incision line on each side).

However, there is an alternative way of producing a SL/WL ratio of 4: taking lots of smaller bytes approximately 5mm (but not more than 8mm) apart from the midline at closer intervals (6mm). After some bench and animal studies the new short-stitch technique has been tested clinically in a single-centre randomized trial involving 750 patients with a need to close their abdominal midline incisions (2). The investigators used a 2-0 polydioxanone (PDS) on a 20mm half-circle taper point needle to involve the fascial layer only in the experimental group (small bites) and randomly allocated a second group to the long-stitch standard mass closure described above (big bites). The short-stitch group had a significantly lower incisional hernia rate at 12-month follow-up (5.6% vs. 18.0%) and a reduced risk of surgical site infections (5.2% vs. 10.2%) compared to the big-bites group.

When I first used the short stitch technique it felt intuitively weaker than mass-closure. I used a thin 2-0 suture, a small needle, little bytes - and sure enough once a stitch pulled out. However, the neighbouring sutures balanced this out easily, it looked almost like nothing had happened. It was at this point that I was reminded of the Velcro principle and its power to hold things tightly together by adding up many small adhesive forces.

A group from the Netherlands launched a multicentre trial in 2011 to further test the hypothesis that the short-stitch is superior to the long-stitch in closing abdominal incisions and called it fittingly the STITCH trial (3). The study has completed recruiting and we wait for the results to be presented soon.

Will you change your technique to small bites?

(1) http://www.ncbi.nlm.nih.gov/pubmed/20395846?dopt=Abstract

(2) http://www.ncbi.nlm.nih.gov/pubmed/19917943

(3) http://www.ncbi.nlm.nih.gov/pubmed/21871072