Repair of Asian nasal subunit defects using nasolabial perforator flaps: A retrospective study

The application of nasolabial perforator flap for nasal reconstruction has been reported previously with satisfactory outcomes, but the outcomes and risk factors of postoperative adverse events have been unclear to plastic surgeons.


| INTRODUC TI ON
The nose is an indispensable component located in the center of the face.According to the facial esthetic subunit principle, it can be divided into different subunits with different textures, and the similarity between the donor site and the defect should be considered in the reconstructions.However, esthetically repaired nasal defects caused by tumors, trauma, and other reasons can still be challenging for surgeons.Several types of flaps can be used to repair nasal defects, including forehead flaps, bilobed flaps, and nasolabial perforator flaps.
Compared to the traditional nasolabial flap, the nasolabial perforator flap has a wider arc rotation, leading to a wider repair range.The purpose of the study is to report the outcome of nasal defect reconstructions with nasolabial perforator flaps, especially the scores of esthetics and blood supply, and identify the risk factors associated with postoperative complications and re-operation.

| Study design
This retrospective study protocol had ethical approval from the institutional and/or national research committee and conforms to the Declaration of Helsinki and subsequent amendments.Consent was obtained from the participants responding to the follow-up surveys.
Medical records and digital images of 58 patients with 61 defects who received nasal reconstruction with nasolabial perforator flap from 2009 to 2021 were retrospectively reviewed.Figure 1 describes the inclusion and exclusion process of patients for this study.The study population consisted of 33 male patients (56.9%) and 25 female patients (43.1%) (mean age, 66.4 ± 2.0 years; range 18 to 86 years), with follow-up periods ranging from 6 to 60 months (median, 23 months).
The parameters of patients' demographics and comorbidities, defect-related information (including causes, subunits, and the size of defects), surgery-related data (including anesthetic mode, flap transfer methods, location of perforating vessels, and the size of flap), and postoperative information (included immediate postoperative scores of esthetic and blood supply, complications, and re-operations) were collected.

| Surgical procedure
All procedures were performed under general anesthesia or local anesthetic.The tumor or mass was resected by leaving a safe surgical margin under the facial esthetic subunit principle: using subunits as repair units when treating more than 50% of subunit defects and concealing the incision line by designing it at the edge of the subunit.The removed tissue is sent to intraoperative frozen section diagnosis.After the diagnosis of negative margin was returned, nasolabial perforator flaps were designed to depend on the location and size of the defects, with 2 mm more than the defect size.The skin and subcutaneous tissue were incised circumferentially along the design line of the flap, which was dissected from the anterior to the base of the flap in the Superficial Muscular Aponeurotic System.An ultrasonic Doppler blood flow detector was used to identify the perforator.Perforators were defined as the same as the Gent Consensus definition (Figure S1). 3 Then, the perforators were freed from the surrounding tissue with blunt dissection, and a part of the surrounding adipose tissue was retained, avoiding perforator injury and leading to poor survival of the flap.This flap was directly transferred or transposed through a subcutaneous tunnel to cover the defect.A thin drainage tube or strip was placed under the flap.The flap was immobilized without a relaxation suture for the blood supply.The donor site was subcutaneously dissociation on either side of the cut, hinging on the laxity of the skin, and closed in layers to conceal the scar in the nasolabial groove (Figures 2 and 3).
All flaps were closely observed with color after surgeries.
Vasodilators or releasing venous obstruction factors were applied for the blocked arterial supply or venous return.The hematoma under the flap should be removed in time, followed by re-hemostasis.

| Outcome assessment
The data of complications and re-operation were recorded.To assess the esthetics and blood supply of the nasolabial perforator flaps, immediate postoperative photos of each nasolabial perforator flap were collected within 1 hour after surgery.For cases that have undergone more than one reconstructive surgery, we chose the last surgery photo as the outcome.Three plastic surgeons F I G U R E 1 Inclusion and exclusion process of patients.
(different from the operating surgeons) evaluated these photos based on the rating guidance for objective grading. 4Evaluations were performed after all patients' photographs had been collected, and the evaluators were blinded to the surgical treatment.
A 5-point Likert scale was used to measure the extent of esthetics and blood supply: excellent, 5 points; very good, 4 points; good, 3 points; fair, 2 points; poor, 1 point.The total mean scores, equal to the sum of the mean esthetics and mean blood supply scores, were used to estimate the overall situation of the flaps and classify the patients into three groups: excellent, 8-10 points; good, 5-7 points; poor, 2-4 points.

| Statistical analyses
The normality of the data was evaluated using the Shapiro-Wilk test, while the Mann-Whitney U test was used for non-normal distributed variables.Intraclass correlation efficiency was used to assess the consistency of scores between the three evaluators.
Regarding the correlation between complications and risk factors, patient-, defect-, and surgery-related variables showing an association with postoperative complications (p-value <0.05) in the univariate analysis, were included in the multivariable models.For the analysis of the correlation between re-operation and risk factors, the variables showing an association with postoperative complications of a p-value <0.2 in the univariate analysis were included in the multivariable models.A binary logistic regression model was used to analyze the correlation between complications, re-operation, postoperative scores, and risk factors, respectively.This model was tested for bias and validated using the Hosmer-Lemeshow analysis (p = 0.204 for re-operation analysis (patients), p = 0.165 for re-operation analysis (defects), p = 0.517 for complication analysis).
Statistical significance was defined by a p-value <0.05.All statistical analyses were carried out using IBM SPSS 26.0 software (IBM Corp., Armonk, NY, USA).

| Demographics of patient characteristics
Table 1 shows the patients' demographic information.The average age of the patients was 66.4 ± 2.0, with a male-to-female ratio of 33:25.
Table 2 shows the defect and operation characteristics of patients.
Sixty-one nasolabial perforator flaps were used for 58 patients with 61 defects as 3 patients presented bilateral defects.Most defects were caused by tumors, especially basal cell carcinoma (BCC).A single nasal subunit was involved in 32 (52.5%) defects, whereas 29 (47.5%)defects involved more than one subunit.Most defects (94.8%) were unilateral.The defect size ranged from 6.5 × 5.5 mm 2 to 40 × 70 mm 2 , with a median length of 23.5 mm and width of 16 mm.

Location of perforating vessels (per defect)
The mandibular line to the lower edge of the nasal alar The lower edge of the nasal alar line to the pupil 58 (95.The immediate postoperative scores, including blood supply and esthetics scores, of the nasolabial perforator flap are listed in Table 4. The consistency of the scores was assessed by the intraclass correlation coefficient, and both scores were in agreement between the three evaluators.The mean scores of the blood supply, esthetics, and overall effect were 4.01 out of 5 points, 3.71 out of 5 points, and 7.72 out of 10 points, respectively.Then, 24 (40.7%)patients were classified into the excellent group (Figure 4), while the other 35 (59.3%) were into the good group; none were assigned to the poor group.

| Risk factors of postoperative complications and re-operations
The results of the multivariable analysis of the correlation between flap ischemia and risk factors, including BMI, diabetes, and smoking history, are presented in Table 5 (Univariate analysis results were in Table S1).No significant correlation was detected in the current study.
The results of the multivariable analysis of the correlation between re-operation and risk factors are presented in Table 6 (Univariate analysis results were in Table S2).

| DISCUSS ION
The most common cause of nasal defects is BCC and these defects can be reconstructed with multiple flaps.Compared to the frequently-used forehead flap, the nasolabial flap provides the skin with similar color, texture, and pigmentation to the defect area.
Moreover, the donor site of the flap has better esthetic results because of the natural nasolabial groove caused by aging. 5The forehead flap has a higher flap loss rate (11%) and revision rate (58%), and usually, more than one revision surgery is required. 6However, the postoperative complications and re-operation rates are lower with the nasolabial flap than the traditional flap,  expanded the range the nasolabial flap can repair and provided a basis for the reconstruction of complex defects involving multiple subunits.0][11] Perforators with surrounding connective tissue were preserved while harvesting the perforator flaps, including some drainage veins, which guaranteed the blood supply of the flap and reduced the rate of complications. 4 Only one case had irreversible ischemic necrosis of the flap in our study, while all others survived.
Moreover, nasolabial perforator flaps are thin, which reduces the swelling, increasing the possibility of primary reconstruction.
About 89.6% of patients have undergone 0 or only 1 revision surgery in this study.
Distal circulation provides the blood supply of the perforator flap (Figure 5).Type A accounts for 77.8% of the facial arteries. 12A previous anatomy study on 20 facial arteries reported that each has six perforators with a mean length and diameter of 17.6 ± 1.9 mm and 0.91 ± 0.2 mm, respectively. 13Several studies have revealed the gathering area of the facial perforator.Qassemyar et al. found that the area of highest perforating density was located 1.5 cm lateral to the oral conjoined level with a diameter of 1 cm. 14Color Doppler ultrasound is predominantly used in clinical practice to locate the perforators, which can be accurate for vessels with >0.5 mm diameter and the surrounding structure.Infrared thermography has been used for perforator location in other large perforator flap reconstructions 15 ; however, it is not sufficiently accurate in small-to-moderate facial  flaps.Contrast-enhanced B-flow can precisely obtain the supra fascial course of the perforators, thus improving the safety of flap harvesting. 16e facial subunits in the repair of defects were first proposed in 1954 by Gonzalez et al, 17 which provides a basis for using different natures of the skin for flap selection.Burget et al. 18 divided the nose into nine subunits: nasal dorsum, bilateral lateral nasal walls, nasal tip, nasal columella, bilateral nasal lobules, and bilateral soft triangles.Based on this, a general principle of a flap application is as follows: using subunits as repair units rather than defect areas when the defect is more than 50% of the subunit, and concealing the incision line under the subunit edge for a better esthetic result.
A nasolabial perforator flap can be used for the small-to-moderate nasal defect under the facial esthetic subunit principle.In the current study, reconstruction of nasal ala (30) and sidewall ( 16) is most frequently used for nasolabial perforator flap, while the other nasal esthetic subunits are also covered.
The thick skin in the nasal ala has limited activity.The nasolabial perforator flap and forehead flap are used regularly for imitation by plastic surgeons to achieve the goal of "like-with-like."Given the difficulty of ala repair as it is time-and energy-consuming, secondary surgery is commonly used in clinical practice.However, secondary surgery prolongs the treatment period and has a high complication rate. 19The application of a nasolabial perforator flap makes primary surgery available.About 65.5% of defects in this study have The common postoperative complications of perforator flaps include venous congestion and partial necrosis, 22 and the former occurred in 4.9% of flaps in the present study.One of the venous congestive flaps progressed to necrosis, which could be attributed to the perforator damage, and finally, a secondary skin graft was performed for repair.A meta-analysis reported that age ≥60 years, smoking, diabetes, and radiotherapy are the risk factors associated with complications in flap reconstruction. 22Herein, we did not find any risk factors for complications due to the low complication rate   For all patients who undergo surgery with a nasolabial perforator flap, it is suggested that the changes in flap color and temperature should be kept under close observation.Using vasoactive drugs or relieving venous obstruction needs to be conducted at once, in case of the flap arterial supply or venous reflux is blocked.

| CON CLUS ION
This study demonstrated that the nasolabial perforator flap could be applied in nasal reconstruction with different nasal subunits with satisfactory esthetic outcomes and fewer complications, and the involvement of more than one nasal subunit was found to be a risk factor of re-operation.The nasolabial perforator flap provides "like with like" nasal skin and the scar on the donor site can be concealed naturally.However, a large number of involved subunits may lead to multiple surgeries for flap trimming in easterners.

AUTH O R CO NTR I B UTI O N S
Hong-Ying Lin analyzed the patients' data and was a major contributor to writing the manuscript.Xi Bu has made contributions to the acquisition of the patients' data.Xin Yang Drew the pictures in the manuscript.Yong-Huan Zhen followed up with the patients and collected photos of the case.Dong Li substantively revised the manuscript.
Zhen-Min Zhao substantively revised the manuscript.Yang An developed the conception of the manuscript and substantively revised it.

E TH I C S S TATEM ENT
All procedures performed in studies involving human participants were in accordance with the ethical standards of Peking University's Third Hospital (IRB00006761-M2022502) and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.

I N FO R M E D CO N S E NT
All participants provided informed consent.

| 631 LIN
et al.Moreover, the donor site of the nasolabial flap can be obscured by the natural groove.Because of the excellent esthetic effect and a high degree of freedom, the nasolabial perforator flap is the right candidate for repairing nasal defects.However, the complications of nasolabial perforator flaps include postoperative congestion or ischemia, and some flaps require secondary debulking or pedicle division surgery.Previous studies have shown that Type 2 diabetes mellitus, elderly age, large flap size, and other factors can affect the blood supply of the flap in plantar reconstruction. 1,2Currently, no studies have focused on identifying the risk factors of complications and secondary surgery with nasolabial perforator flaps in nasal reconstruction.Based on this background, we hypothesize that the occurrence of postoperative complications and re-operation would be affected by several patient factors (e.g., patient age and comorbidities) and surgical factors (e.g., flap size and transfer methods).

F I G U R E 2
Surgical procedures of nasal reconstructions with a nasolabial perforator flap.(A) The tumor or mass was resected with a safe surgical margin leaving a nasal defect.(B) The design and incision of the nasolabial perforator flap according to the defect characteristic.(C) Dissection and exposure of the perforator.(D) The flap was transferred directly to cover the defect.(E) suture of the flap and conceal the scar in the nasolabial groove.F I G U R E 3 The key steps of procedure with nasolabial perforator flap.(A) Excision of granuloma and flap design.(B) Dissection of nasolabial perforator flap as transposition flap.The yellow asterisk (*) indicates the location of perforator.(C) A drainage strip was placed under the flap, and the flap was sutured into the defect with a 6-0 nylon suture.The range of nasolabial perforator flaps was 6 × 14 mm 2 to 30 × 75 mm 2 , with a median length of 40 mm and a width of 19 mm.Three (4.9%) flaps repaired three nasal subunits in the unilateral nasal as follows: (1) dorsum, nasal tip, and nasal columella; (2) soft triangle, nasal base, and upper lip; (3) ala, nasal base, and upper lip.Then, various forms of nasolabial perforator flaps were transferred, including transposition (68.9%), propeller (16.4%), island (11.5%), and V-Y advanced (3.3%) flaps.Most perforators were detected in the line between the lower edge of the alar and the pupil.The mean operation duration was 222.6 ± 16.1 min (including the time of intraoperative frozen pathology), and the maximal reconstruction was performed using local anesthesia.TA B L E 2 Defects and operation characteristics of patients.

3. 2 |
Postoperative outcome of flapsTable 3 presents the postoperative outcome of flaps in this study.Herein, three (4.9%)flaps suffered from venous congestion, and only one of them accepted skin grafting because of progressing to necrosis, whereas the remaining two eventually survived without surgical intervention.Only one ischemia flap (1.6%) was gradually alleviated with dressing and observation.Subsequently, 20 (34.5%) patients underwent re-operation for trimming or pedicle division.
The current model showed that the patient had more than one nasal subunit of involvement (p = 0.004, odds ratio [OR] = 0.131, 0.032-0.532),and the defects involved more than one nasal subunit (p = 0.002, OR = 0.129, 0.036-0.461)are the risk factor for re-operation, with statistical significance.However, no significant correlation was established between age, BMI, diabetes, defect length, flap length, and re-operation in this study.

7 TA B L E 3 4
and the nasolabial flap surgery can be performed under local anesthesia.Therefore, the nasolabial flap is recommended for the elderly or patients with underlying diseases.Compared to the traditional nasolabial flap, the nasolabial perforator flap has several advantages.First, the nasolabial perforator flap is large in size.In previous studies, the width of the nasolabial perforator flap is 2-4 cm, 8 suitable for the reconstruction of small-to-moderate defects.In the current study, a 40 × 80 mm 2 flap was prepared for repairing nasal ala and soft triangles with a good blood supply.Second, the perforator flap has more radians of rotation.The arc of rotation maximum reached 180°, which Postoperative outcomes of patients or defects.Immediate postoperative scores of esthetics and blood supply of the nasolabial perforator flap.
For nasolabial perforator flaps, 75% of the perforators are obtained from the facial artery.The main trunk of the facial artery has a regular trend.Nakajima et al. divided the facial artery into three main types based on the course of branches; among these,

F I G U R E 4
A 62-year-old male presented a pyogenic granuloma on the right nasal sidewall.(A, B): A defect of 7 × 12 mm 2 (less than 50% of the subunit).(C, D): Appearance on the first postoperative day.(E, F): Appearance after a 60-month follow-up period.TA B L E 5 Logistic regression analysis for risk factors associated with flap ischemia.
undergone primary reconstruction with a satisfactory postoperative esthetic result, and no complications were noted.The skin of the sidewall is thin but thickens as it transitions to the cheek.The local flap, including transposition, bilobed, and glabellar flap, is a frequently used approach.Although the nasolabial flap is not the first choice in the reconstruction of the sidewall, it was applied because most patients included in this study were elderly with a large defect, and the tissue volume of the local flap is too limited to repair.The loose and thin skin of the elderly helps to hide the postoperative scars in the nasolabial groove.The most common way of flap transfer is the transposition flap (68.9%).Chang et al. reported a strategy for choosing the transfer method.The study suggested that the transposition flap should be chosen when the diameter of the defect is >3 or <3 cm but near the nasolabial groove; otherwise, the V-Y flap should be chosen.20The transposition flap can distribute the tension of the skin.In this study, complications occurred in two cases of propeller flap and two cases of island flap, which might be related to an overly thin flap and narrow perforator base.21

( 6 .
6%).The localization of perforating vessels may be a potential risk factor associated with poor blood supply, and in our study, we use an ultrasonic Doppler blood flow detector before every operation to get the precise locations of vessels.Additional cases should be included in future investigations to explore the risk factors associated with complications in the nasolabial perforator flaps in a large sample size.Hitherto, only a few studies have focused on the factors associated with multiple surgeries in flap transplantation.The current study found that the involvement of more than one nasal subunit TA B L E 6 Logistic regression analysis for risk factors associated with re-operation.

F I G U R E 5
Blood supply of the perforator flap.| 637 LIN et al.is a risk factor, indicating a complicated flap design.Various nasal subunits need varied skin thicknesses; hence, plastic surgeons may retain thicker subcutaneous tissue in the primary flap harvest for safety, and re-operation would be performed for trimming.Western people have thinner skin, and a single subunit defect can achieve excellent results in primary operation without a remarkable scar.Because of the racial difference, easterners are likely to leave obvious scar hyperplasia around the flap.The thick skin of the nasal and nasolabial area requires repeated trimming after the first surgery, including keloplasty and flap thinning.Nevertheless, the present study has some limitations.First, the postoperative outcomes were measured with immediate photos, while the intraday blood flow could not predict whether the flap would be ischemic later accurately.Flap survival requires continuous dynamic observation and may even require indocyanine green fluorescence.Second, a few other relevant factors that may have an impact on complications or re-operation have not been included in this study, such as radiotherapy history, chemotherapy history, and anemia.However, because of the limitation of the retrospective study, these data have not been collected.A prospective study involving a prolonged follow-up period and a large sample size may provide an in-depth insight into the esthetic outcomes and their risk factors.Furthermore, the evaluation of esthetic results is based on the subjective ratings of plastic surgeons.Although scoring details are provided for standardization, an objective evaluation is still lacking.Thus, preoperative and postoperative 3D follow-up photos can be utilized for measurement in future studies.

Characteristics a p-value OR OR 95% CI Lower Upper
a Only variables with p < 0.05 in the univariate analysis were included in the multivariable analysis.