Chapter 5.23: The Vertical Mattress Tip Stitch

Modified corner stitch

This technique, also described as the modified corner stitch, is designed to bring three ends of tissue together, and is used in the context of a flap, where it permits the tip of tissue to be inset. This can be conceptualized as a vertical mattress variation of the tip stitch, permitting circumferential tissue advancement while concomitantly encouraging wound eversion and mitigating the risk that the tip is set deeper than the surrounding wound edges. Since it is used only when attempting to approximate three segments of skin, this is a niche technique.

Suture choice is dependent in large part on location, though as always the smallest gauge suture material appropriate for the anatomic location should be utilized. On the face, where this technique may be used for flap repairs, a 6-0 suture is appropriate. On the trunk, extremities and scalp, a 3-0 or 4-0 suture material may be used. Monofilament nonabsorbable suture material is generally appropriate when utilizing this technique.

1. The flap is brought into place using buried sutures, allowing the tip to rest with only minimal tension in its desired position.

2. The needle is inserted through the epidermis at 90 degrees starting at the far right edge of the distal nonflap section of skin, with a trajectory running toward the tip. This entry point through the epidermis should be approximately 3 mm set-back from the epidermal edge, depending on the thickness of the dermis and the anticipated degree of tension across the tip. The needle, and therefore the suture, should exit in the mid-dermis on the same portion of nonflap skin. Bite size is dependent on needle size.

3. The needle is then grasped with the surgical pickups and simultaneously released by the hand holding the needle driver. As the needle is freed from the tissue with the pickups, the needle is grasped again by the needle driver in an appropriate position to place a suture through the dermis on the flap tip to the left of the previously placed suture.

4. A small amount of suture material is pulled through and the needle is inserted into the dermis in the flap tip, at the same depth as it exited from the nonflap edge, and the needle is passed through the dermis on the flap tip at a uniform depth following a trajectory tracing an imaginary circle around the point where all three segments of skin will meet. The needle is then grasped with surgical forceps and released from the needle driver.

5. Attention is then shifted to the proximal nonflap edge of skin, where the needle is inserted in the mid-dermis of the incised edge, with the needle exiting through the epidermis in a mirror image of step (2).

6. The needle is reinserted through the epidermis just medial to the exit point, exiting through the dermis at the incised wound edge of the nonflap skin.

7. The needle is then reinserted in the dermis on the flap in a mirror-image of the technique utilized in step (4), running at the same depth of the dermis but distal to the suture material placed in step (4) relative to the flap tip.

8. The needle is then inserted through the dermis at the incised wound edge on the initial edge of nonflap skin, exiting medial and superior to the original entry point.

9. The suture material is then tied utilizing an instrument tie (Figures 5-23A, 5-23B, 5-23C, 5-23D, 5-23E, 5-23F, 5-23G, 5-23H).

This technique was developed to solve a problem encountered with standard tip stitch techniques—the tendency of the flap tip to sit deep relative to the surrounding skin. Some of this problem may be due to lack of attention to the importance of uniform depth when taking bites through the dermis on all sides, though more likely it is related to the relative upward pull on the nontip sections of skin by the transepidermal sutures in the standard tip stitch.

The vertical mattress variation of the tip stitch therefore allows better wound eversion and less of a tendency toward a depressed tip than the standard approach.

The tip stitch is very useful when bringing the tip of a flap into place. Importantly, this technique is designed to gently approximate the tissues so that the flap is properly inset in the surrounding skin. While it bears a technical resemblance to the buried purse-string approach, it is important to appreciate that the tip stitch is not designed to work under significant tension, as tension across the suture may lead to necrosis of the delicate and lightly vascularized tip of the flap.

This is particularly important here, since the vertical mattress tip stitch places two loops of suture material through the tip, increasing the risk of necrosis and tissue strangulation.

Placing set-back dermal sutures, imbrication sutures, or suspension sutures prior to placement of the tip stitch will ensure that the tip itself is not under tension when it is approximated with the surrounding skin.

Yet another variation of this technique entails burying the bite through the second nonflap wound edge so that the only percutaneous sutures are in the first nonflap edge of skin. In this case, steps (5) and (6) are replaced by taking a bite through the dermis alone before beginning the return course of the suture. This approach may slightly lessen the chance of infection and residual dimpling since the suture material on that edge does not traverse the epidermis. This half-buried approach is similar to the Allgöwer variation of the vertical mattress suture.

Flap tip necrosis is the greatest risk with this technique, since two loops of suture material traverse the dermis containing the tip’s vascular supply. This risk may be mitigated by tying the suture together relatively loosely so that the tip is not overly constricted when the knot is tied. Additionally, if the bites of dermis are sufficiently set-back from the wound edge, a small bite comprising less than half of the dermis in the tip could be taken. This would allow blood supply to the tip even in the context of a relatively tight loop running through the distal flap.

Since this technique entails the placement of two loops of suture through the flap tip, it may be associated with a higher rate of necrosis than other variations of the tip stitch. Therefore, unless the better wound-edge approximation of the vertical mattress placement is needed, it may be preferable to adopt other variations of the tip stitch that do not require the additional loop of suture through the tip.

Finally, while flap tip necrosis is a risk, studies have suggested that the tip stitch provides less vascular constriction than other options, such as placing two vertically oriented sutures at the edges of the tip or a suture directly through the tip itself. Vascular compromise and ensuing necrosis of the flap tip is always a risk, even if no sutures are placed through the tip itself, and therefore the tip stitch approach likely provides a reasonable balance between tissue approximation and adequate vascular supply.