Partial flap loss in transgender phalloplasty using the anterolateral thigh or forearm - a systematic literature review

A1 patient selection

The mean age of patients included in the systematic review was 34.6 years. Given the increasing accumulation of medical co-morbidities with age, this speaks to the fact that overall, this is a predominantly healthy patient population. Unfortunately, none of the articles mentioned the age of patients suffering from PFL. Smoking is a well-established risk factor for PFL and other associated wound healing issues at both the recipient and donor sites^[30]. We were surprised to find that some centers offer phalloplasty to active smokers. We strongly advise that patients have a negative cotinine test three months prior to phalloplasty surgery. Although typical recommendations are to stop smoking 4-6 weeks prior to an elective surgery from a physiologic standpoint, smoking cessation comes with marked psychological stress and as such, it is advisable to deal with this significant life stressor prior to adding the mental and physical stress of complex surgery. Diabetes should be well controlled, with a Hb1Ac within normal limits. While obesity itself is not known to be a risk factor for PFL, it can make the microvascular aspect of the surgery difficult or impossible. We recommend that ideally, patients have a BMI < 30, although we evaluate any patient with a BMI < 35 as fat distribution is a greater determining factor than BMI alone. In the studies that did report on BMI, none assessed whether increased BMI was a risk factor for PFL. It is important for future research to include all relevant co-morbidities and patient demographics. It would be impactful if this information was included both for the total number of patients as well as for the subgroups suffering complications. This would allow future meta-analyses to be performed in order to perform subgroup analysis and identify risk factors for PFL, as well as other complications. It is important to identify modifiable pre-operative risk factors. As previously stated, complication rates are extremely high following phalloplasty surgery. Although these surgeries are essential to this patient population, there is time in the pre-operative assessment period to introduce lifestyle modifications and optimize the medical management of co-morbidities to optimize patient condition, and in doing so, hopefully minimize complication rates. The first step in this process is to identify the risk factors that appear to correlate with specific complications.

A2 flap dimensions

The dimensions of the RFFF and ALT flap used for phalloplasty are significantly larger than those of a standard RFFF or ALT. This is especially true when performing a tube within tube (TWT) phalloplasty. The ideal TWT flap dimensions are at least 16 cm in width and 16 cm or more in length. These dimensions are far beyond most traditionally-described ALT and radial forearm flaps, pushing the limits of the perforators and their associated perfasomes to perfuse the flap via linking vessels. De Wolf et al.^[17] recognized this issue and utilized intraoperative indocyanine green angiography to identify RFFF that that would benefit from supercharging and did so by using the posterior interosseous artery. In these cases, the anastomosis is performed to the palmar branch of the radial artery distally or in an end-to-side fashion proximally. In their study of 29 patients, 15 had supercharging of the radial forearm flap as described above, resulting in no cases of PFL.

In cases utilizing the ALT flap, dimensions are often even wider than those of the radial forearm. This is because the ALT flap is significantly thicker with a greater proportion of adipose tissue when compared to the radial forearm. This additional bulk often requires a wider skin paddle in order to be able to tube the flap around the thicker adipose tissues. Care has to be taken to include as many perforators as possible in order to support this increased flap volume (see section C1 ALT - absence of or failure to include distal perforators). Intuitively, it makes sense that if an ALT or RFFF is only used for shaft-only and composite flaps, the PFL rate would be lower due to smaller dimensions. The current literature shows a trend in that direction except for the shaft only ALT, which had a markedly higher rate of PFL [Table 3]. However, this is based on a single study that may have been an outlier. Future studies should include flap dimensions to account for lengths that may vary between cohorts and the number of perforators included.

A3 technical errors

Obviously, any technical errors diminishing perfusion increase the risk for partial or total flap loss. For RFFF, a sub-fascial dissection between the flexor carpi radialis and past the superficial radial nerve can assist in protecting the radial artery and its associated perforators. During ALT harvest, care has to be taken to include all possible perforators, including those with a complex intramusuclar course due to the large dimension of the flap taken and its associated volume of tissue. The time spent meticulously dissecting out all viable perforators will be well-spent by decreasing the risk of areas of PFL as much as possible. Failure to convert to a free flap in case of a short pedicle or failure to create a wide enough tunnel are other technical aspects to consider.

B1 RFFFP - proximal perforator inclusion

In a traditional antegrade radial forearm flap, only the distal perforators are captured. In the RFFFP, it is important to also capture the proximal perforators^[7][Figure 4]. There is usually one distinct large perforator entering the flap that may exit the radial artery proximal to the proximal flap edge. If unaware of its location and importance, it is easily divided. In our practice, we have realized that this perforator may even take a brief intramuscular or intratendinous course and care should be taken to identify this perforator and dissect it out. Some authors advocate keeping a dermal bridge between the shaft and the proximal urethral extension to further improve blood supply to this watershed region. In the literature, the most commonly reported region of PFL was the distal radial border of the flap; this correlates with our own experience^[16]. The vascular territory supplied by perforators of the posterior interosseous artery correlates anatomically to the dorsal and radial aspect of the radial forearm flap. Therefore, the previously mentioned strategy of supercharging with use of the posterior interosseous artery may be an ideal strategy to avoid PFL in this location^[16].

B2 RFFFP - location

None of the review articles comment on the exact placement of the RFFFP design on the forearm in regards to the location of the radial artery. Most articles that discuss technique do, however, comment on the benefit of placing the urethra over the ulnar side of the forearm due to the sparse amount of hair follicles in this region. Although a valuable point regarding hair follicle density, this is not always the best strategy in regards to optimizing flap perfusion. In the case of a small forearm circumference, this may lead to placement of the flap that is relatively too radial with eccentric location of the radial artery. This can increase the risk of local areas of ischemia and flap loss. In our practice, in patients with a forearm circumference of less than 15.5 cm we place the flap further ulnar beyond the least hair-bearing area to allow the radial artery to be more centralized. We have no data to support this claim, but it makes logical sense to have the perforators closer to the edge that is most affected by PFL (dorsoradial) and hopefully capture enough linking vessels to allow for perfusion of the entire flap.

C1 ALT - absence of or failure to include distal perforators

When it comes to ALT phalloplasty, the tissue of the distal aspect of the thigh has two very important benefits compared to harvesting the ALT from the mid-thigh: (1) thinner and more pliable tissue; and (2) a longer vascular pedicle allowing for a comfortable transfer to the genital region. The obvious downside however, is that more distal placement of the flap design often does not allow capture of the proximal and often more sizeable perforators. Additionally, distal perforators are more often intramuscular and necessitate a more difficult intramuscular dissection. Pre-operative CT angiography (CTA) can assist decision-making by identifying the laterality that is most likely to have numerous perforators in the desired flap location and have the highest take off of the lateral femoral circumflex artery, allowing for greater pedicle length for flap transposition^[31]. In addition to CTA, we routinely perform hand-held Doppler exams in our clinic to document the location of audible perforators. Even in ideal circumstances, it is typical that the most sizeable perforators will often enter the proximal third of the flap. A strategy discussed at oral presentations by the Buncke clinic group (San Francisco) is to include a de-epithelized proximal dermal extension to capture perforators located proximally to the flap design.

C2 ALT - excessive intraoperative thinning

In most circumstances, the ALT is too bulky for TWT phalloplasty. Even in thin patients, the dimensions of the flap often get too bulky. In these cases, intraoperative thinning of the subscarpal fat layer is a useful strategy to allow for a more natural aesthetic result. We favor doing primary shaping rather than secondary liposuction or lipectomy. However, this is not without consequence. As the lateral femoral cutaneous nerve runs along this fascial plane, it jeopardizes innervation to the neophallus and, if done too excessively, can impede the subcutaneous connecting vascular plexus. In our experience, however, judicious thinning allows for decreased tension on the tissues when they are tubed and comes with improved overall flap vascularity by reducing the overall bulk and size of the flap.

C3 - Failure to delay the flap

Despite meticulous pre-operative medical and physiological optimization and surgical planning, the size of the flap may be just too big for the few available perforators on which the flap can be elevated. Therefore, it is our opinion that a low threshold should be held to delay a flap that appears congested or marginally perfused in the operating room. We have performed this successfully in two cases. Of course, we cannot know if the flaps would have been adequately perfused if transferred and shaped primarily as originally planned. However, especially with a TWT flap, it makes logical sense that a flap that is already mildly congested will not endure additional strain and insult. In these two cases, we took the patient back on postoperative days 5 and 7, respectively. They both did well and the flaps appeared less congested at the time of take back. There is little risk to flap delay and it may avoid disastrous complications for the patient. A phalloplasty is not like a standard flap in that the shaping is much more aggressive. The flap is being tubed, often twice on itself. Therefore, the vascular inflow and outflow must be robust. If relying only on random pattern perfusion through choke vessels outside of the perfasomes of the flap, the tubing of the flap will almost certainly lead to vascular issues. Therefore, delay should be considered if absolute confidence does not exist in regards to flap vascularity. The overall quality of a reconstruction should never be compromised in an effort to cut down on surgical stages; if necessary, delay.

Urethral loss

The management of urethral loss depends on the extent of involvement. Smaller segments can be managed by excision and re-anastomosis, or a two-stage urethroplasty using buccal mucosa grafts. Larger segments of urethral loss may necessitate additional tissue transfer, which adds to the donor site burden and potentially increases the overall complication profile. At our institution, we perform a staged approach to phalloplasty as developed by the St. Peter Andrology Institute. In this strategy, the urethra is marsupialized adjacent to the clitoral shaft at the first stage and as such, is amenable to visible inspection in the postoperative period [Figure 6]. At the second stage, the urethra is connected to the native urethra using vulvar tissue. To allow for this, the ipsilateral labia minorum is resected during the first surgery. If done in this fashion, any ischemia can be identified promptly and the urethra can be shortened and marsupialized at a higher level if necessary [Figure 7].

Figure 6. Appearance at the second stage of a Big Ben style two-stage phalloplasty. Note the marsupialized pars pendulans urethra^[33,34]

Figure 7. Example of partial flap loss of the proximal urethral extension in an anterolateral thigh flap phalloplasty. After stage two, the patient developed a fistula that was amenable to outpatient repair; voiding now and has received a semi-malleable implant. A: visible ischemic urethral flap; B: status post marsupialization at a more superior location^[35]

Shaft loss

The management strategy regarding the loss of shaft tissue also depends on the extent of involvement. Larger areas may require an additional free flap. In the case of full thickness tissue loss, we favor placement of Integra (Integra, Princeton NJ) followed by the application of a full thickness skin graft. Skin grafting alone may suffice in the setting of partial thickness tissue loss [Figure 5].