Perineal Surgery: A Novel Use for the Keller Funnel

Questions

1. What are the effects of radiation therapy on local tissue and structures seen in anterior perineal resection requiring vertical rectus abdominis myocutaneous flap coverage?

2. What are the indications and benefits of the Keller Funnel?

3. What are important factors that affect vertical rectus abdominis myocutaneous flap viability in anterior perineal resection?

4. Why was the Keller Funnel indicated compared with other techniques in the setting of a narrow pelvic inlet?

Case Description

A 51-year-old male with rectal squamous cell carcinoma post chemoradiation therapy presented for a scheduled anterior perineal resection (APR) with subsequent vertical rectus abdominis myocutaneous (VRAM) flap for perineal closure (Figures 13). On inspection, the irradiated pelvic inlet was found to be narrowed, stiff, and densely fibrosed with a 6.5 × 9.0–cm perineal defect. The size of the VRAM flap required to adequately cover the perineal defect would entail a challenging tunneling process, risking significant flap trauma. To avoid compromising the flap size and supply of arterial perforators, the Keller Funnel (Keller Medica, Stuart, Fl)—a flexible funnel-shaped polymer with a lubricated hydrophilic inner surface used for breast implant insertion—was used to facilitate transposition of a large VRAM flap through a narrow and stiffened pelvic inlet (Figure 49). Subsequent perineal coverage was successfully achieved without the need to modify flap surface area or bulk (Figure 10 and Figure 11). At 2 weeks postoperatively, the VRAM flap displayed good viability with appropriate wound healing and no signs of arterial or venous compromise (Figure 12). The patient did not experience postoperative complications and is happy with his results.

FIGURE 1.

Dissected right rectus abdominis flap with identified arterial perforators.

FIGURE 2.

6.0 × 9.5–cm perineal defect.

FIGURE 3.

Looped end of VRAM flap.

FIGURE 4.

Keller Funnel.

FIGURE 5.

Keller Funnel advanced into the pelvic inlet.

FIGURE 6.

Looped end traveling within Keller Funnel.

FIGURE 7.

Removal of the Keller Funnel.

FIGURE 8.

Completed removal of the Keller Funnel.

FIGURE 9.

Securing VRAM flap to the perineal defect.

FIGURE 10.

Completed closure of the perineal defect.

FIGURE 11.

Closed abdominal incision with placement of end colostomy.

FIGURE 12.

2-week postoperative results.

Q1. What are the effects of radiation therapy on local tissue and structures seen in anterior perineal resection requiring vertical rectus abdominis myocutaneous flap coverage?

In addition to surgical resection, the use of neoadjuvant chemoradiation therapy has been shown to decrease local recurrence and improve overall survival in anal and rectal cancer; yet, its effect on wound healing can be detrimental to the integrity of the created dead space.¹ Radiation therapy is designed to induce free radical damage to the targeted surrounding soft tissue, which triggers inflammatory cascades, vascular damage, thrombosis, and cell death, often leading to a densely fibrosed and stiff perineal canal with poor vascularity.²

Over the past decade, outcomes in perineal reconstruction with vertical rectus abdominis myocutaneous (VRAM) flap following neoadjuvant chemoradiation have been associated with increased rates of wound healing complications—namely, flap dehiscence, partial flap necrosis, and perineal abscess formation—when compared with nonirradiated tissue. The existing literature reports an overall wound complication rate of 66% in anterior perineal resection (APR) following radiation, with 16 to 30% requiring additional surgical intervention.^3,5

While the importance of decreasing the rate of cancer recurrence remains paramount to overall survival, there is a scarcity of literature on surgical technique to minimize the potential damage to the delicate flap vasculature during tunneling of VRAM flaps.

Q2. What are the indications and benefits of the Keller Funnel?

The Keller Funnel (Keller Medica) is a mechanical breast implantation assistance device composed of a flexible funnel-shaped polymer with a lubricated hydrophilic coating on the inner surface designed for easier insertion, decreased contamination, and smaller incisions compared with traditional manual implant insertion techniques.⁶ It can be customized by the surgeon to accommodate a range of implant sizes, which are loaded directly into the funnel from their packaging and advanced into the surgical pocket without touching the surgeon's gloves or the patient's skin.

This no-contact approach has been shown to result in a 27-fold decrease in skin contact for breast implants compared with manual insertion by reducing the risk of contamination from contact with breast parenchyma.⁷ A retrospective analysis of 380 cases8 found that the use of a funnel resulted in an infection rate of 0.26%, compared with 0.52% found in a comparative analysis of 1628 mammoplasties with manual implant insertion.⁹ The decreased infection risk may be partially attributable to the reduction in time needed to insert the implant through the skin incision—approximately 6 seconds—compared with 16 seconds with manual insertion.¹⁰

Q3. What are important factors that affect VRAM flap viability in APR?

Fundamental to any flap procedure is the creation of a tension-free closure of the surrounding skin and soft tissue. When using the VRAM flap, the shape and size of the abdominal skin paddle must be carefully designed to best match the prospective perineal defect, considering both the skin area and intrapelvic dead space filling requirements.

To maximize arterial perfusion of the overlying subcutaneous fat and skin, the skin paddle should have a minimum horizontal width of 5 to 6 cm. Narrow skin paddles may contain an insufficient amount of randomly dispersed abdominal perforators, which branch off the inferior epigastric artery.¹¹ Alternatively, the use of doppler technology can assist in identifying perforators, allowing for skin marking and visualization of the arterial distribution.

In situations where a greater arch of rotation is required to cover the perineal defect, the caudal rectus abdominis insertion can be detached from the pubic bone. However, care must be given to avoid cutting the pyramidal segment of the rectus abdominis insertion to prevent unsupported traction to the vascular pedicle while tunneling the flap through the pelvis.^4,12

Q4. Why was the Keller Funnel indicated compared with other techniques in the setting of a narrow pelvic inlet?

Pelvic transposition of VRAM flaps can be difficult among patients with a narrow pelvic inlet. Due to the delicate nature of the flap microvasculature, manual insertion of a bulky flap may subject the flap to unnecessary shearing forces and prolong tunneling times, theoretically compromising the pedicled stalk vasculature and risk avulsion of the arterial perforators. Furthermore, flap tissue edema develops with prolonged tunneling times, worsening venous return. Modifications to reduce paddle bulk and size, such a split VRAM flap (split along the branches of the inferior epigastric vessels), can be attempted. The split rectus myocutaneous flap is a narrower, less bulky body of tissue with successful outcomes reported in the literature; however, a reduced flap size may compromise arterial supply and reduce the amount of flap filling the pelvic dead space.^13,14

The Keller Funnel allows for a nearly contact-free technique for large breast implants to be safely and quickly inserted into small incisions and is proven to reduce infection rates and operative times.⁶ Applying these principles to narrowed pelvic inlets, the use of the Keller Funnel may allow for easier flap transposition, reduced tunneling times, and reduced overall flap wound healing complications. To our knowledge, this is the first reported use of the Keller Funnel for tunneling a VRAM flap after APR.