Surgeon's Corner: Friction Knots & the Aberdeen Knot

Reliable vascular pedicle ligation is a required skill of any veterinarian performing surgery. Ineffective vascular ligation can be a life-threatening surgical error, leading to severe blood loss, repeated exploratory surgery, and death.

Hemorrhage is the most common cause of death after ovariohysterectomy. Significant hemorrhage is a notable risk when ligating thick ovarian pedicles with high fat content; and the initial throw of the ligature is of critical importance. If the initial square throw is not tight or does not retain its initial tension, the ligated tissue and vessels will bleed despite successive tight square throws. This can occur due to elastic recoil of the tissue, or from uneven tension applied to the suture strands during subsequent throws. Friction knots are recommended to maintain extrinsic tension on the ligated tissues between the first and subsequent throws.

The video above demonstrates the proper technique to form the following 3 friction knots, along with the alternative Aberdeen knot used in subcutaneous and intradermal closures.

The surgeon’s knot is a simple, commonly used friction knot that is usually adequate for thinner vascular pedicles and when smaller suture material, such as 3-0 or 4-0, is preferred. However, this knot has been outperformed by other friction knots in several studies and is often inadequate for large, bulky pedicles.^1,2,3

The strangle knot and Miller’s knot are both friction knots that require 2 initial passes around the vascular pedicle. The difference in formation is demonstrated in the video. These knots are secure, are easy to perform, and provide resistance to luminal pressures up to 2 to 3 times that of normal arterial blood pressure in dogs.

The Aberdeen knot is an alternative knot used when ending a continuous suture line, most often for subcutaneous and intradermal closure. When used in subcutaneous closure, this knot allows the surgeon to continue directly to an intradermal closure without cutting the subcutaneous suture line. In addition, a 2-throw, 1-pass Aberdeen (as shown in the video) was found to be as strong as and less bulky than a traditional 4-throw square knot,⁴ which reduces foreign material in the closure and makes burying the knot easier.