Free flap harvest from the infraumbilical region for head and neck reconstruction purposes: a retrospective cohort study

The abdominal wall has showed many advantages as a donor site in head and neck reconstruction given its constant pattern of dominant perforators. Currently, standard design of the skin component of composite soft-tissue flaps recommended for head and neck reconstruction encompasses the lower and upper periumbilical region thus increasing the overall vascularization of the flap. We report on the safety of the harvest of abdominal soft-tissue free flaps from the infraumbilical region. A retrospective charts review was performed. Consecutive subjects who underwent microsurgical reconstruction of composite defects of the Head & Neck with infraumbilical free flaps between January 2008-January 2020 were enrolled. After surgery, patients were followed up at three-month intervals to evaluate the incidence of complications and the long-term outcome at the donor site. 25 patients underwent reconstruction with free flaps harvested from the lower abdomen. A total of 35 abdominal flaps (20 VRAM, 15 DIEAP) were performed; ten patients underwent bilateral flap harvest and abdominoplasty was performed to achieve direct closure. Marginal abdominal skin necrosis occurred in 3 patients postoperatively. Abdominal bulge occurred in one case; neither hernia nor abdominal wall weakness were not encountered at a median follow-up of 12 months (IQR 6; 27). The results of the study confirm that the infraumbilical region is a safe donor area of free flaps for head and neck reconstruction that preserves abdominal wall firmness and improves ultimate functional and aesthetic outcomes at the donor site.


INTRODUCTION
The abdominal wall has become an increasingly popular donor site for head and neckreconstruction. Several studies demonstrated the feasibility of different perforator flaps from the abdominal region as a suitable donor site to well fit defects with varied sizes and shapes in head and neck reconstruction. [1][2] [3] Usually, the skin component of Transverse/Vertical Rectus Abdominis myocutaneous flap (TRAM/VRAM) and Deep Inferior Epigastric Artery Perforator (DIEAP) flap used for reconstructive purpose in the cervico-facial area, is selectively designed covering the periumbilical area of the lower and upper abdomen to include the dominant perforators, hence harvesting highly vascularized flaps. [4] Initially, it was a common belief that multiple perforators provided better vascularization of the flap. Various studies instead proved that flap survival is mainly determined by the distance between the main perforators and the midline. The latter statement is particularly true when considering viability of zone 4. [5] Therefore, the flap is now routinely pedicled by only one or two medial row perforators that emerge from the medial branch of the deep inferior epigastic artery in the paraumbilical area, where the skin component is safely designed. [4] [6] Different skin paddle designs extending over the entire abdominal wall (vertically, horizontally or obliquely oriented) have been successfully described to increase the amount of viable tissue harvested based on periumbilical perforators. [7] [8] However, in case of large defects requiring bilateral flaps, the harvest of a paraumbilical skin paddle is generally associated with poor aesthetic outcomes. These result from worse abdominal contour and a less concealable scar when compared to the harvest of a flap in the inferior aspect of the abdomen. [7] We report on the safety of the harvest of abdominal soft-tissue free flaps from the infraumbilical region.

Study design and setting
A multicenter retrospective cohort study on consecutive patients who underwent reconstruction of composite defects of the Head and Neck region with infraumbilical abdominal free flaps was performed at the Units of Maxillofacial Surgery of Verona and Padua (Italy). All subjects signed informed consent to be enrolled in the present study. The institutional ethical committee approved the study.

Patients
Consecutive subjects who underwent primary or delayed reconstruction of major head and neck soft tissue defects with abdominal perforator free flaps from the infraumbilical area were eligible for the study. Patients were excluded in presence of previous history of surgical violation of the anterior abdominal wall for other disorders.

Data collection and variables
The clinical charts of the patients treated at our Units between January 2008 and January 2020 were reviewed. Relevant clinical data were extracted and entered into an electronic spreadsheet form. The following data were collected from the clinical charts: age, sex, reason for surgery (diagnosis), date of surgery, type of flap harvest, side of the flap harvest, size of the skin flap component, type of abdominal wall closure; cervico-facial defect type and size were also recorded.

Surgery
All cases treated at the recruiting centers had been routinely discussed at the institutional multidisciplinary head and neck oncology board that included the oncologist, radiotherapist, the radiologist and the head and neck surgeons. Thereafter, For bilateral harvest of flaps, the abdominal skin paddles were designed covering both sides of the inferior aspect of the anterior abdominal wall, with the patient in the supine position and the knees slightly flexed. [9] Typically, the lower incision is transversely placed at the suprapubic crease and above the inguinal ligament up to the anterior superior iliac spines (ASIS). The upper incision is placed above the umbilicus and gently curves laterally to reach When a VRAM flap was planned, a full width harvest of the RA muscle and anterior rectus sheet above the arcuate line was performed. Careful dissection of the deep inferior epigastric pedicle down to its origin from the iliac vessels provided a pedicle 8 to 10 cm long. Strengthening of the abdominal wall was achieved with the use of a synthetic non-absorbable mesh (2/0 nylon suture) to repair the muscle defect (Fig. 3A).
When a DIEAP flap was planned, the rectus sheet was opened at the selected perforator that was traced through the muscle, splitting the RA muscle fibers and preserving the intercostal nerves. The superficial inferior epigastric vein (SIEV) was always included as an outlet for venous congestion. A tension-free coaptation of the rectus sheet was achieved with a running large caliber non-absorbable suture (Fig. 3B).

Study outcome
The main outcome of the study was the occurrence of donor site complications in short (within 1-month), medium (6-month) and long-term follow-up (up to latest follow-up). Complications were categorized as minor or major.
Abdominal bulging and hernia formation were defined as major complications, regardless of the need for reparative surgery. Physical examination and abdominal ultrasonography were performed to confirm diagnosis.
Complicated abdominal wound healing with surgical-site infection/skin dehiscence were classified as minor when successfully managed with medications or local flap transposition. Cases requiring major reparative surgical interventions or repeated additional surgical procedures to correct abdominal skin unfavorable outcome were considered as major complications.
Abdominal wall firmness was determined by the absence of muscle hypotony with complete resumption of daily activities.
The final appearance of the abdominal wall was inspected for the presence of overall symmetrical abdominal contour and stable infraumbilical scar healing without unfavorable skin remnants. A score system graded 1-3 was used to define poor, satisfactory and good results, respectively. Recipient site was also inspected for flap failure that was categorized as complete in presence of total flap necrosis, and partial in cases of incomplete skin loss (variable extent).

Statistical analysis
Continuous variables are reported as median (50 th percentile) and interquartile range (IQR, 25 th and 75 th percentiles).
Discrete variables are reported as the number and proportion of subjects with the characteristic of interest. Statistical analysis was performed using Stata 16.1 (Stata Corporation, College Station, TX, USA).

Patients
In the period between January 2008-January 2020, 25 consecutive patients underwent reconstruction of soft tissue defects of the cervico-facial region with free flaps harvested from the lower abdomen. The baseline features of study population are given in Table 1.
The patients were 11 men and 14 women with a median (IQR) age of 56 (47; 65) years.
The most frequent diagnosis was oral squamous cell carcinoma (n= 21, 84%), of these 6 patients had recurrent malignancies following surgery and radiation treatment at primary cancer diagnosis. Isolated tongue defects (total glossectomy) were treated in 8 cases, whereas the remaining 17 patients needed reconstruction of composite hard and soft tissue defects in the cervico-facial region.
A total of 35 abdominal infraumbilical free flaps were performed and 10 patients underwent bilateral flap harvest.
The average soft tissue defect size was 11x8 cm (maximum defect size 12x8 cm) after total glossectomy, and 18x9 cm

Postoperative donor site complications
Abdominal bulging occurred 1 year after surgery in one case following a two-sided flap harvest (combined VRAM/DIEAP flaps). The latter complication did not require surgical repair. (Fig. 6A-B).  This is, however, largely due to the fact that we enrolled mostly advanced-stage cancer-patients (primary or recurrent malignancy) who were recommended for adjuvant therapies and/or long-term supportive care (enteral feeding) after surgery.
The reconstruction of head and neck defects is often challenging for the functional implications of the three-dimensional composite framework of the cervico-facial area and usually required great amount of donor tissues.
Abdominal perforator flaps based on DIEA vascular territory have become an important donor source of large volume of vascularized tissues that can be tailored to the defective recipient site in the cervico-facial area. [1][3][10] [11] TRAM/VRAM flap is commonly used to reconstruct subtotal/total glossectomy defects providing highly versatile tissues supporting the restoration of bulky defects. [12][13] [14] Instead, DIEAP adipocutaneous flaps can be used to cover large cutaneous defects of the cheek and the neck. Third, the infraumbilical approach, in both transverse and vertical design (unilateral or bilateral), allows for a more concealable scar located in the inferior aspect of the abdomen.
Of importance, the pedicle length of the infraumbilical flaps was appropriate in all cases for the reconstructive purpose, including secondary reconstruction of large soft-tissue defects in vessel-depleted neck due to tumor extirpation and radiotherapy.
In our study, the rate of post-operative abdominal complications was in line with others studies reporting the donor site Qeios, CC-BY 4.0 · Article, November 15, 2020 Qeios ID: CGGYLF · https://doi.org/10.32388/CGGYLF 20/22 morbidity of standard periumbilical flap harvest (range 3.5-20%). [18][19] [20] In conclusion, our study supports the hypothesis that the infraumbilical area is a reliable donor region of free flaps for the reconstruction of composite defects of the head and neck, Harvest of multiple flaps (sequentially or simultaneously) from a single donor area does not preclude abdominal wall integrity.
Placing the abdominal flaps entirely in the lower abdomen does not impact the abdominal wall firmness and provides satisfactory functional and morphological results at the donor site.
• Funding This research did not receive any specific grant.