No Unraveling in the OR: Novel Knot Technique

A research team from Mayo Clinic has designed and tested a novel knotting technique that could decrease stress in the OR. The innovation, a two-strand-overhand locking (TSOL) knot, was designed and mechanically evaluated with use of different suture materials and knot configurations and in actual tendon repairs.

The researchers compared the knot holding strength of the TSOL knot with that of a 4-throw square knot with use of three different suture materials that are in common clinical use. With use of braided polyblend suture, the TSOL knot was also compared with five other surgical knot configurations. Finally, the strength of tendon repairs performed with use of the TSOL knot and a 4-throw square knot was studied.

Chunfeng Zhao, M.D. and his team told OTW, “Our team has been active in flexor tendon repair research for over 15 years, and we have explored many techniques to improve strength and healing. Knot unraveling using modern tendon repair techniques has been reported to be a relatively common occurrence; we have seen this in our own laboratory experiments. This is a critical complication that may occur in the repair of any tissue subjected to high-tension loading. Recognizing that both the tensile strength of the suture material and suture holding strength of tissue are typically higher than loads required to unravel commonly used knots, we saw a great opportunity to improve repair strength by overcoming this weak link in the chain.”

Dr. Zhao continued, “The impact of very strong suture materials is greatly limited by the strength of the knot used. When using a high-tensile-strength suture, 4-throw square knots unraveled at tensile loads as little as one-quarter of the intact suture tensile strength. The proposed two-strand overhand locking (TSOL) knot performed better, with failure loads nearly one-half of the intact suture tensile strength. A simple change to the repair technique provides opportunities to take greater advantage of a suture’s strength.”

Asked about the most important findings, Dr. Zhao noted, “Not only did we observe that the TSOL knot was significantly stronger (both statistically and practically speaking) than the other common surgical knots tested, it does not result in a significantly increased knot size. This is particularly important in flexor tendon repair, as the knot is buried between the two repaired tendon ends, and the presence of a large foreign body can negatively impact healing. The type of suture used does influence the mechanical advantage of this new knot over the 4-throw square knot. However, for all suture materials tested, the advantage of the TSOL knot was substantial. This knot is quick and simple to make with or without an assistant.”