Introduction

In most microsurgical centers, the free radial forearm flap represents the most common technique for penile reconstruction or transgender phalloplasty [1,2,3,4,5,6,7,8,9,10]. Previously, two different surgical techniques have been described: the first designed by Chang [11], published in 1984, and the second designed by Gottlieb and Levine [12], published in 1993. For both the techniques, the creation of a phallus required the harvesting of a large flap. Defect coverage of the donor site is most likely done by the use of split-thickness skin grafts [4, 13] or full-thickness skin grafts [4, 13,14,15]. Plastic surgeons know about the nuisance of wound healing disorders consisting in exposed tendons, reoperations, and extended duration of hospital stay [7, 16]. In the literature, the proposed solutions for optimizing the donor site after free radial forearm flap harvest include the use of endogenous tissue such as pedicled or free flaps that are either associated with great surgical effort [8] or simply too small to cover the entire donor site [4, 5, 9, 13, 17]. The solution proposed by several researchers are the use of dermal templates, such as Integra® or MatriDerm® [7, 17,18,19]. Initially, the dermal templates secure wound healing of the grafted skin on the bradytrophic tissue was employed in burn surgery, which minimizes the complications [20]. The dermal templates replace the dermis, where the application of an epidermal layer is needed and can be performed in a single-stage or two-stage procedure [7]. In our institution until 1993, the phalloplasty was done by adopting the design of Gottlieb and Levine [14]. There was an average donor site of 11 cm in width and 12 cm in length. The donor site reaches distally up to 2 to 3 cm from the palmar flexion crease (Fig. 1). Thus making the techniques applicable for minimizing the donor site like embedding of the exposed tendon into the adjacent muscle belly is impossible. At our institution, we used to perform the donor site defect coverage by full-thickness skin graft from the groin area. There are various reasons why the donor site defect coverage is done by full-thickness skin graft instead of split-thickness skin graft. The scar in the groin area is well hidden, and there is a request from patients to hide the donor site on the radial forearm by tattoo, which we considered safe after 1 year of surgery. In the split-thickness skin graft, the ink tends to smear and the artwork gets blurred. Due to the issues described above, we decided to switch to MatriDerm® and split-thickness skin graft from the thigh. Eventually, our institution compared the operative outcome on 21 patients with donor site coverage by a full-thickness skin graft from the groin area and the same number of consecutive patients with donor site defect coverage by single layered MatriDerm® dermal substitute plus split-thickness skin grafts from the thigh.

Fig. 1
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Donor site after harvesting the free radial forearm flap

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Patients and Methods

At our institution, a case series analysis of all patients having received defect coverage after harvesting the free radial forearm flap for the creation of a phallus by single-layered MatriDerm® and split-thickness skin grafts from the thigh (group A) between May 2016 and February 2018 was conducted. These 21 patients were compared to the same number of directly preceding patients receiving the defect coverage by full-thickness skin graft from the groin area (group B). All patients included in the study received a phalloplasty using Gottlieb and Levine’s technique [12, 14]. All patients were operated in an interdisciplinary two-team approach consisting of plastic surgeons and urologists. The short-term outcome of the donor site was analyzed with a special focus on wound healing disorders, reoperation rate, and duration of hospitalization (Fig. 2). The complications were classified by the Clavien–Dindo classification [21]. Ethics approval for the study was obtained from the ethical committee of the Hessian Medical Association. The methods of the study adhered to the CARE guidelines.

Fig. 2
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Wound healing disorder in the groin area after harvesting full-thickness skin graft for defect coverage

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Statistical analysis was performed using the software SPSS (version 23.0) and R (version 3.3.2). Fisher’s exact test (χ2) test was used to detect the association between variables. The significance of the differences was tested with t test. A p value lower 0.05 was defined as statistically significant. A p value between 0.05 and 0.1 was defined to indicate a tendency towards a higher risk for complications.

Operative Technique

The phalloplasty procedure consists of a standardized procedure, as published previously [14]. The following description is about performing the defect coverage on the radial forearm. Preoperatively, Allen’s test was routinely performed in all patients to ensure adequate perfusion of the hand by the remaining ulnar artery. Elevation of the free radial forearm flap from the non-dominant forearm was performed as described previously by Gottlieb and Levine in 1993 [12, 14]. We adopted a careful dissection technique preserving the paratendon to provide a well-vascularized recipient bed for the skin graft or the dermal template to minimize the donor site morbidity. Defect coverage was either done by a full-thickness skin graft, harvested from the groin area, fatty gauze, following installation of the vacuum-assisted closure-therapy (VAC®) system; or by single-layered MatriDerm® plus split-thickness skin graft (0.2–0.3 mm thickness) from the thigh, fatty gauze, followed by the installation of a VAC® system. Installation of the VAC® system for graft fixation was performed identically in both groups. All patients were restrained from splint for 7 days after the operation. The VAC® system was removed from the bedside on the sixth postoperative day. Daily dressing was done for several days subsequently, until the skin graft showed not only adherence but stability as well. Once the skin graft was stable, the patients were instructed to perform scar massage and to apply a moisturizing ointment on a daily base. Patients were advised to wear a compression sleeve for 3 months postoperatively.

MatriDerm®

MatriDerm® (Skin and Health Care AG, Billerbeck, Germany) is a structurally intact matrix of bovine type I collagen with elastin which is used for dermal regeneration. The matrix serves as a support structure for the in growth of cells and vessels. Its elastin component improves the stability and elasticity of the regenerating tissue. As the healing process advances, fibroblast lays down the extracellular matrix, and the MatriDerm® resorbes it [20].

Results

A total of 42 patients undergoing phalloplasty by Gottlieb and Levine were included on accrual in the study. Thereof, 21 patients received donor site defect coverage by MatriDerm® and split-thickness skin graft (group A). The control group underwent full-thickness skin graft in the groin area (group B). Those 21 patients in group B preceded the patients from group A chronologically. In group A, the mean age of the patients was 33.4 years (range 18–51 years) with a mean BMI of 24.36 kg/m2 (range 19.1–32.04 kg/m2) and a mean duration of hospital stay of 20 days. Seven patients were active smokers at the time of surgery (33.3%). In group B, the mean age of the patients was 28.9 years (range 18–54 years) with a mean BMI of 25.8 kg/m2 (range 16.23–34.37 kg/m2) and a duration of hospital stay of 22 days. Eleven patients were active smokers at the time of surgery (52.4%). The patient groups did not differ statistically in terms of age (p=0.18) or proportion of smokers (p=0.49).

Complications were classified according to the Clavien–Dindo classification [21]. As defined by the authors, there is a graduation from zero to five [21]. Grade zero is assigned for the absence of complications. The definition of grade 1 is any deviation from the normal without any actions needed. Grade 2 is a complication that requires conservative medical therapy. A grade 3 complication requires surgical intervention. In our patient cohort, if there was no life-threating event, then it is defined as grade 4, and if the patient dies, it is grade 5 (Table 1). As Fig. 3 shows, group B is shown as an aesthetically unpleasant scar in the groin area, due to high tension on the scar.

Table 1 Patients’ complications after defect coverage of the donor site on the radial forearm in group A (MatriDerm® and split-thickness skin graft) and group B (full-thickness skin graft) based on the Clavien–Dindo classification
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Fig. 3
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Long-term result of a donor site morbidity after harvesting the free radial MatriDerm® and a split-thickness skin graft and b fullthickness skin graft from the groin area

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Fisher’s exact test revealed a statistically significant difference between groups A and B for complications on the forearm based on the Clavien–Dindo classification compared to non-complication (0) and any (1–5) (p = 0.008) and between the non-complication as well as complications that can be treated conservatively and complications that require surgery (0–2 vs. 3–5; p=0.002). Especially in patients with low BMI, harvesting such large free radial forearm flaps from the forearm, as well as large full-thickness grafts from the groin, (partial) primary closure is under tension, often leading to subsequent wound dehiscence leaving behind an unpleasant scar (Fig. 3).

The average duration of hospital stay was 20 days in group A versus 22 days in group B (p=0.09). Statistical analysis showed no significant difference with respect to duration of hospital stay between groups A and B (p= 0.98). Power analysis revealed a needed sampling size of 51 patients per group to show a statistically significant difference. In both groups, we did not witness any neuroma of the superficial branch of the radial nerve.

Discussion

In most microsurgical centers, phalloplasty is most likely performed using the free radial forearm flap [1,2,3,4,5,6, 8,9,10, 14, 18, 22]. The donor site morbidity accompanied by a stigmatizing scar on the (non-dominant) forearm problem remains unsolved [4, 7,8,9, 14, 17]. The aim of this study was to investigate whether the use of the cost-intensive dermal layer reduced short-term complications and if reoperations would decrease or even become unnecessary and if the duration of hospital stay could be reduced. Our sample size allowed to clearly identify risk factors when performing donor site defect coverage of the radial forearm by full-thickness skin graft from the groin area. The use of a dermal template, such as MatriDerm®, allowed us to propose a solution for patients presenting to surgery with those identified risk factors.

The Clavien–Dindo classification allows a uniform description of complications if applied correctly, even a comparison between multiple centers. This study clearly showed that concerning short-term results, MatriDerm® had a significant impact on reducing wound healing disorders, accompanied by intensive dressing changes or even reoperations. From a physician’s point of view, any reoperation may represent a certain risk for the survival of the newly created phalloplasty, due to blood pressure alterations during anesthesia. In addition, reoperations present a high cost factor for the institution. Wound healing disorders as shown in Fig. 4 may be tedious for patients. In our center, we decided that the lower complication rate on the forearm by the use of MatriDerm® is worth the additional costs. The standard length of hospital stay after the creation of a phallus equaled 21 nights. In our patient collective, the average stay in group A was 20 days (range 16–36 days) and in group B was 22 days (range 15–49 days). The statistical outliers were due to wound healing disorders on the forearm.

Fig. 4
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Partial loss of full-thickness skin graft requiring surgical revision with defect coverage by split-thickness skin graft

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Considering that the major part of our patients undergoing phalloplasty are transgender men, we respect the distress the patients undergo before presenting for surgery, or even before being diagnosed correctly [23].Whenever possible unfavourable preoperative conditions such as smoking and low or high BMI are improved in an interdisciplinary team approach. We aim to achieve a result within acceptable margins and try not to deny access to sex reassignment surgery.

For a long time, we witnessed an aesthetically appealing result on the radial forearm in both groups (Fig. 5). However, to integrate our patients as soon as possible into social and professional life, we focus on short-term and midterm results. Especially in skinny patients, the tension on the donor site is high, and wound healing disorders occur more likely; the use MatriDerm® and split-thickness skin graft for donor site defect coverage shows excellent functional and aesthetic outcomes as described by others [18]. Even though the scar in the groin area, respectively on the thigh, is stigmatizing in our patients, we witnessed a certain acceptance, since the scar can be effectively hidden in swimming trunks and shorts.

Fig. 5
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Aesthetically unpleasant scar in groin area after harvesting the full-thickness skin graft for defect coverage of the forearm (group B)

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To our experience, some patients conceal the stigmatizing scar on the radial forearm by artfully designed tattoos. Unfortunately, there is a lack in literature about the possibilities and limitations of tattooing on skin grafts. To our knowledge, when using ink on split-thickness skin graft alone, the artwork will end up blurred since the ink tends to run away, and when tattooing on full-thickness skin graft or MatriDerm® and split-thickness skin graft, this problem does not occur.

Conclusion

The use of a dermal template such as MatriDerm® significantly reduced the complication rate at the forearm donor site in patients undergoing free radial forearm phalloplasty and may yield aesthetic outcomes compared to the use of full-thickness skin graft alone, or even better in some cases. However, the visible donor site at the thigh after split-thickness skin harvest has to be considered as well and in the end weighed against the donor site after full-thickness skin graft harvest in the groin. Especially in skinny patients, this second donor site may be a problem and be unsightly.