In this variation on the traditional horizontal mattress suture, the suture end attached to the needle is passed underneath the loop on the contralateral side, such that the suture material traverses the wound after it is tied.
The suture crossing the wound can aid in apposition of the wound edges, while maintaining the traditional advantages of the horizontal mattress suture.
A potential disadvantage is that the now-locked suture can compress the tissues, leading to increased risk of strangulation and necrosis. Make sure not to tie it off too forcefully.