A single-center study was conducted on 17 of 32 patients who received a pedicled TRAM flap for delayed breast reconstruction from January 2016 to December 2020. All participants were recruited as patients 12 months or more after TRAM surgery. All measurements were performed in July 2021, and the follow-up period was determined relative to that month. Information was gathered from medical records about age, body mass index (BMI), underlying disease, smoking, alcohol intake, chemotherapy, radiotherapy, hormonal therapy, and other surgery than breast reconstruction, patients who underwent radiotherapy after breast reconstruction, patients who had bilateral breast cancer or skin diseases, and patients who had not completed wound healing were excluded from the study.

In the patient group, the skin tone of the lower abdominal area harvested during the TRAM flap could not be measured. To supplement this shortcoming, 20 healthy women in their 40s and 60s were recruited and their skin tone and hydration were measured on the breast and abdomen.

Measurements were made on the contralateral breast, donor site (abdomen), and recipient site (TRAM flap) of each patient using a skin pigmentation analyzer (SPA99; Courage+Khazaka Electronics, Köln, Germany) and skin diagnostic device (SD202; Courage+ Khazaka Electronics). Melanin levels and redness values composing skin tone were measured using a SPA99 (Fig. 1). The measurement scale ranges from 0 to 99. The closer a score is to 0, the brighter the skin is, and the closer the score is to 99, the darker the skin is.

Skin hydration was measured because it can affect melanin levels and redness values [5]. Therefore, when measuring skin tone using SPA99 for each participant, hydration was also measured using SD202 to minimize skin tone mismeasurements due to excessive skin hydration (Fig. 1).

Skin vascularity depends on the environment or the patient’s condition and impacts the skin tone. Therefore, external variables were controlled by conducting the study under constant conditions to the extent possible. The room temperature was kept constant at 26°C using an air-conditioner. All patients rested for at least 15 minutes before the measurements, and the axillary temperature was checked. The measurements were consistently made with the patient in the supine position. The same person measured all the patients to minimize error due to the operator-dependence of the method.

In patients with breast cancer, the contralateral breast skin unaffected by treatment was measured. Since the skin tone may not be the same across the entire breast, measurements were performed at four locations 6 cm apart from the nipple-areolar complex (Fig. 2). The average values of four sites were set as the skin tone data.

When measuring the donor site, hyperpigmentation and dyspigmentation can be observed in the periphery of the scar due to contracture. To minimize the resulting error, the measurements were made as follows. Distances of 3, 6, and 9 cm were marked from the point where the vertical midline and the lower abdominal scar met on both sides. Measurements were performed at a point 4 cm vertically from the markings, and the average melanin level and redness value measured there were recorded as the skin tone data for the lower abdomen (Fig. 2). In addition, the abdomen was divided into two portions—the upper (measurement points 10-15) and lower (measurement points 16-21)—and the average value of skin tone was recorded for each part.

The center of the TRAM flap skin was set at the midpoint of the long axis of the flap. Measurements were taken at five locations, including the central point and four points that were 4 cm apart from the central point (Fig. 2). The average melanin level and redness value at these five points were recorded as the skin tone data.

The breast measurements were made at the same points as in the post-TRAM patients (Fig. 3). The average values of melanin and redness measured at eight sites were used as the skin tone data.

Abdominal skin tones were measured at eight sites (Fig. 3). Points 1 and 2 were classified as the upper abdomen, points 3, 4, 5, and 6 as the flap, and points 7 and 8 as the lower abdomen. Furthermore, points 3 and 4 were subdivided into the upper flap and points 5 and 6 as the lower flap.

The measurement standard was set based on a conventional TRAM flap design. The TRAM flap was designed on a healthy woman’s abdomen. Then, two points 4 cm upward and 3 cm horizontally apart from the midpoint of the upper flap margin were defined as points 1 and 2. Likewise, two points located 4 cm downward and 3 cm horizontally on both sides from the midpoint of the lower flap margin were defined as points 7 and 8. This was done to measure the upper and lower parts, consistent with the abdomen measurement criteria in the patient group. The points where the short axis of the flap is divided into three parts and a 3-cm distance from the 1/3 and 2/3 points horizontally to both sides were defined as points 3, 4, 5, and 6 (Fig. 3), respectively.

For most variables in this study, mean values were compared using the Mann-Whitney test and Wilcoxon signed-rank test because the sample size was small. The Bonferroni correction was used to reduce the errors arising from multiple comparisons. Statistical analyses were performed using SPSS version 25.0 (IBM Corp., Armonk, NY, USA).

The general characteristics of patients are shown in Table 1. All patients had previously received delayed breast reconstruction. The average age of the participants was 56.35 years, and their average BMI was 24.51 kg/m². The numbers of patients who smoked and consumed alcohol were one (5.9%) and two (11.8%), respectively. Of the 17 patients, five (29.4%) had undergone radiotherapy, 13(76.5%) had undergone chemotherapy, and seven (41.2%) had received hormone therapy. Most of the participants in the study were multiparous, and 94.1% of the patients were postmenopausal. In addition, 70.6% of the patients had previously undergone other surgical procedures causing an abdominal scar (cesarean section, open laparotomy, etc.) The average follow-up period of the participants was more than 30 months, and the minimum period was 14 months. The follow-up period was defined as the number of months after surgery at the time this study was conducted (July 2021).

As shown in Table 2, the mean age of healthy women participating in the study was 56.55 years, and their average BMI was 24.97 kg/m². Table 3 presents data on the mean values and ranges of melanin, erythema, and hydration of the flaps, breasts, and abdomen measured in the patient group. Table 4 also shows data for breast and abdomen measurements obtained in healthy women.

Comparison of melanin levels and redness values between the donor site, flap, and contralateral breast. As shown in Table 5, the melanin level in flaps was 22.56 ± 4.30, and redness was 36.08 ± 5.75. In contralateral breasts, the melanin level was 22.46 ± 4.06 and redness was 33.91 ± 4.56. At the donor site, the melanin level was 26.99± 4.67 and redness was 38.14 ± 5.16.

First, the difference in melanin levels between the flaps and contralateral breasts was non-significant. The redness values showed a slight difference in numerical terms, but it was not statistically significant (P = 0.102). In the comparative analysis between the flaps and donor site, the melanin level showed a difference in the average of 4.43, while the difference in the average redness value was 2.06; however, the difference was only significant for melanin levels(melanin: P < 0.001, redness: P = 0.076). A significant difference was observed in both melanin and redness between the contralateral breasts and donor site (melanin: P < 0.001, redness: P = 0.002).

The non-radiotherapy group tended to have lower melanin levels and higher redness values than the radiotherapy group, but this difference was not significant (Table 6). The average melanin level of the flap in the non-radiotherapy group was 21.92 ± 4.26, while that in the radiotherapy group was 24.12 ± 4.46. In contrast, the mean redness value of the flaps was 36.75 ± 6.63 in the non-radiotherapy group and 34.48 ± 2.55 in the radiotherapy group. Fig. 4 presents some cases of patients who did or did not receive radiotherapy.

In Table 7, the average melanin level of the flaps was 22.56 ± 4.30 and the redness value was 36.08 ± 5.75. The average melanin level of the upper portion was 25.19 ± 4.81 and the average redness value was 37.56 ± 3.89. The difference in the upper portion values was 2.63 for melanin and 1.48 for redness. Of these, only the difference in melanin levels was statistically significant (P = 0.002). When the upper and lower portion were compared, the lower portion had higher values, with differences of 3.59 for melanin and 1.16 for redness value between the two groups. Likewise, only the difference in melanin levels was statistically significant (P < 0.001).

Table 8 shows that the contralateral breasts and the upper portion of the donor site showed statistically significant differences in both melanin levels and redness values, as was also the case for differences between the contralateral breast and lower portion of the donor site.

Table 9 shows data comparing skin tone by abdominal area in healthy middle-aged women. The melanin levels showed statistically significant differences between all three segments of the abdomen (upper: 23.83 ± 4.63, flap: 29.00 ± 5.38, lower: 30.43 ± 4.43). The redness values showed statistically significant differences in all three groups, except for the difference between the flap sites and the lower abdomen (upper: 35.98 ± 1.47, flap: 40.29 ± 1.60, lower: 40.28 ± 2.67).

Table 10 shows the results of comparative analyses of differences between the breast and flap sites (upper and lower flap) groups in healthy women. Statistically significant differences were found in melanin levels (breast: 23.44 ± 3.21, upper flap: 26.65 ± 4.81, lower flap: 31.35 ± 6.00), and redness values (breast: 33.94 ± 2.53, upper flap: 38.83 ± 2.91, lower flap: 41.75 ± 2.37) between the three groups.