Slipping the knot: a comparison of knots used in adjustable suture strabismus surgery

PURPOSE

To evaluate the frictional force created by different knots used in adjustable suture strabismus surgery.

METHODS

To allow the simulation of strabismus surgery suture tying methods a model using 6-0 polyglactin 910 suture was created. Three different knots were evaluated: (1) the sliding noose knot with a double wrap of suture, (2) the cinch knot with a single throw on both sides of the pole suture, (2) and a single-throw square knot. (Bow-tie knots were not included.) A digital force meter was used to measure the force (gram-force [gf]) required to overcome the static friction created by the knot. Each simulation was repeated with new suture material 5 times and the force required after subsequent repositioning was also recorded.

RESULTS

The force to overcome static friction of the sliding noose knot was 240 gf [95% CI, 187-284 gf]; of the cinch knot, 150 gf [95% CI, 123-167 gf]; and of the square knot, 110 gf [95% CI, 95-121 gf]. Subsequent movement of each knot along the same suture required progressively less force, with the sliding noose maintaining the most static friction.

CONCLUSIONS

The sliding noose knot generates the most frictional force and also maintains the most friction after subsequent repositioning. Important consideration should be given to multiple repositioning movements, because the force required for each subsequent repositioning decreases.

Eye muscles surgery

In the past year, experimental studies have analyzed instrument-induced measurement errors during strabismus surgery, investigated intraoperative variables pertinent to adjustable sutures, and investigated ways to prevent and create adhesions in animal models. Newer surgical techniques include coincident resection and recession of a rectus muscle, recession and resection without placement of scleral sutures, and modification of graded anterior transposition of the inferior obliques. Ocular motility problems related to thyroid ophthalmopathy, or lost muscles, as well as those occurring after surgery for retinal detachment remain a challenge. Patients may avoid the risks associated with the use of topical corticosteroids after strabismus surgery by using nonsteroidal anti-inflammatory drugs in their place. Recent contributions to the literature on these issues are reviewed here.