Postoperative Mechanomodulation Decreases T-Junction Dehiscence After Reduction Mammaplasty: Early Scar Analysis From a Randomized Controlled Trial

Abstract Background Soft tissue and cutaneous tension is an important contributor to complicated wound healing and poor scar cosmesis after surgery and its mitigation is a key consideration in aesthetic and reconstructive procedures. Objectives The study objective was to assess the efficacy of the force modulating tissue bridge (FMTB) (“Brijjit”, Brijjit Medical Inc., Atlanta, GA) in reducing mechanical tension on postoperative wounds. Methods A prospective, single-center, randomized, within-subject clinical trial was conducted to evaluate wound healing and nascent scar formation after 8 weeks of postoperative wound support with the FMTB. Patients received standard of care (SOC) subcuticular closure on the vertical incision of 1 breast and experimental closure with the FMTB on the contralateral incision after Wise-pattern reduction mammaplasty. Three-dimensional wound analysis and rates of T-junction dehiscence were evaluated by clinical assessment at 2, 4, 6, and 8 weeks postsurgery. Results Thirty-four patients (n = 68 breasts) completed 8 weeks of postoperative FMTB application. There was a reduced rate of T-junction wound dehiscence in FMTB breasts (n = 1) vs SOC breasts (n = 11) (P < .01). The mean vertical incision wound area during the intervention period was significantly decreased in the FMTB breast (1.5 cm2) vs the SOC breast (2.1 cm2) (P < .01) and was significantly lower at 2-, 4-, and 8-week follow-up (P < .01). Only the closure method was significantly associated with variations in Week 8 wound area (P < .01) after linear regression modeling. Conclusions FMTBs decrease nascent scar dimensions and reduce the occurrence of wound dehiscence. This study provides evidence that the use of continuous mechanomodulation significantly reduces postoperative wound complications after skin closure. Level of Evidence: 2


Level of Evidence: 2
Editorial Decision date: August 10, 2023; online publish-ahead-of-print August 22, 2023.Mechanical and tensile forces play an important role in postoperative wound healing. 1,2Plastic surgeons are trained to mitigate tensile forces in aesthetic and reconstructive procedures, incising skin along Langer's lines 3,4 or optimizing fascial and soft tissue closure. 5In the last few decades, hallmark preclinical studies have outlined the clinical effects of mechanomodulation, demonstrating that the translation of mechanical forces into chemokine-regulated inflammatory pathways induces fibrosis. 2These forces can become aberrantly upregulated, leading to pathologic scar formation such as keloid or hypertrophic scarring.Modulating these mechanical forces significantly reduces scar formation and decreases the propensity for pathologic scars in vitro and in vivo. 1,6][8][9] The relationship between mechanical tension and wound healing is circular.Mechanical stress both encourages dermal tissue remodeling and is a key contributor to the gradual increase in the tensile strength of the nascent scar after injury. 10,11In the first weeks of healing after surgery, a new matrix of collagen and extracellular matrix proteins reorganizes in response to injury and yields 50% and 80% of the tensile strength of unwounded skin by 4 and 6 weeks after surgery, respectively. 12This gain in the scar's tensile strength is driven by a response to tension, and studies have shown the absence of mechanical stress impairs normal wound healing pathways.Conversely, aberrant or excessive mechanical tension on healing wounds can lead to dehiscence or chronicity in the short term and pathologic scarring in the long term.Thus, strategies or adjuncts to attenuate cutaneous tension play an important role in decreasing wound complications as well. 13hen tissues are reapproximated after surgical incisions, tensile strength is concentrated at the interface between suture and tissue. 14As absorbable sutures typically begin to lose strength around 2 weeks after surgery, this tension is transferred to the wound itself, correlating with the time point at which wound dehiscence is first observed. 11,15Thus, decreasing tissue strain postoperatively with cutaneous application of force modulating tissue bridges (FMTBs) potentially mitigates this translation of tensile forces and better supports postoperative wound healing.
The FMTB ("Brijjit", Brijjit Inc., Atlanta, GA) is a novel, FDA-approved device for wound closure and support.The device is applied externally and perpendicular to a wound or incision, decreasing cutaneous tension through a process known as "mechanomodulation." 16Its biomechanical efficacy was first described in 2018 by Kazmer and Eaves. 17The authors found that FMTBs significantly decreased transverse tissue strain in computer-generated modeling compared with the standard-of-care (SOC) closure technique which utilizes sutures.According to their analysis, the compressive stresses at the tissue-suture interface were 4000 mmHg, while those at the tissue-FMTB interface were 20 mmHg. 17n this study, we report clinical findings on postoperative wound healing and early scar formation from a randomized controlled trial in which the FMTB is used to offload mechanical tension on postoperative incisions.Taking Wise-pattern reduction mammaplasties as a clinical and surgical model, we used objective endpoints to demonstrate the efficacy in mitigating wound healing complications and supporting nascent scar formation.

METHODS
Our study is a single-center, prospective, randomized controlled trial conducted at a large academic center.The study was approved by the UT Southwestern Medical Center Institutional Review Board.Participants to date include 34 females undergoing bilateral reduction mammaplasty with a modified Wise-pattern resection for treatment of symptomatic macromastia.Procedures were performed by 3 surgeons at a single outpatient surgery center.Inclusion criteria (Table 1) included healthy adult females between 18 and 70 years of age planning to have a bilateral breast reduction with Wise-pattern skin resection to treat symptomatic macromastia.Patients also had to be able to adhere to FMTB therapy and attend biweekly follow-up visits through the 8-week postoperative period and longterm follow-up visits at 3 6, and 12 months following surgery.Exclusion criteria included known allergies or sensitivities to general adhesives or adhesive tape, the use of isotretinoin or systemic steroids within the

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Aesthetic Surgery Journal 43 (12)     previous year, individuals with significant scarring or clinically significant preoperative breast asymmetry, individuals who were malnourished or had a BMI ≥40 kg/m 2 , individuals with a known history of breast cancer or previous radiation therapy, active smokers, or individuals known to have a disorder that negatively affected wound healing.Subjects in this postoperative intervention period analysis were enrolled between October 2021 and April 2023.
Patients were self-controlled by means of a bilateral control vs intervention model: 1 breast underwent final skin closure with absorbable subcuticular sutures and the contralateral breast underwent final skin closure with FMTBs (Figure 1).Patients eligible for the study were prospectively randomly allocated into 2 groups prior to study commencement by a web-based, open-source randomizer. 18Randomization assignments were concealed until just prior to surgery when study investigators provided the assignment to the   circulating and scrub nurses.The surgeon was blinded to the subject's assignment until final skin closure at the end of the procedure.Both breasts underwent dermal closure by the buried, inverted interrupted technique with 3-0 Monocryl suture (Poliglecaprone 25/3-0 Monocryl; Ethicon, Inc., Raritan, NJ).This was followed by application of the FMTB in the experimental breast or the running subcuticular technique with 4-0 Monocryl in the control breast, for final superficial tissue approximation (Figure 2).After intraoperative procedural symmetry was confirmed, final vertical incision closure took place with sutures or FMTBs, depending on assignment.(Video).
Group 1 underwent final skin closure using 4-0 Monocryl for Side 1 (patient right breast) and FMTB for Side 2 (patient left breast).Group 2 underwent final skin closure with FMTB for Side 1 and Poliglecaprone 25 suture for Side 2 (Figures 3, 4).Aside from final skin approximation and closure, the remainder of the tissue closure technique was identical for both breasts, for all incisions (ie, periareolar and inframmary fold).
Patients returned at 2, 4, 6, and 8 weeks after surgery for postoperative wound therapy visits, where incisions were examined, assessments captured, and FMTBs removed and replaced by a study investigator.Subjects received instructions before surgery regarding proper application of FMTBs in case of early accidental device removal between postoperative study visits.On the morning of surgery, patients received their own FMTBs and alcohol prep pads.Instructions for postoperative hygiene were the same as for other patients undergoing reduction mammaplasty at our institution.Showering was permitted starting 48 hours postsurgery, facing away from the shower head, and patting breasts dry with a towel.Patients initiated scar care as recommended by the operating surgeon at 6 weeks postsurgery but were instructed only to treat the medial and lateral inframammary fold incisions to reduce the potential for confounding.Preliminary results are reported according to CONSORT 2010 extension guidelines for within-person randomized trials. 19

Study Endpoints
The primary endpoint of the complete study is clinical, objective, and subjective assessments of the vertical incision scar through 12 months after surgery based on the Patient and Observer Scar Assessment Scales (POSASs) and blinded assessment of clinical photographs by trained surgeons.Secondary endpoints of the study include histologic analysis, ultrasonographic measurements of the healing surgical site, measurements of nascent scar ultrastructure and stratum corneum integrity, colorimetry, and nascent scar area and volume, the last of which is the focus of this preliminary report.Per published guidelines, the significance of nascent scar measures was considered to be a level of α(k + 1).
In this study, we define the "vertical incision" as the surgical site and clinical model during the intraoperative and postoperative periods.During the 8-week postoperative wound support and intervention period, we defined the healing incision as a "nascent" or "early" scar for simplicity.

Subject Demographics, Operative Measures, and Safety
Demographic data collected included BMI (kg/m 2 ), age at surgery, race/ethnicity, and smoking status.Additional anthropometric variables were collected through chart review, including: sternal notch-to-nipple distance (cm), degree of ptosis (Grade I-IV), base width (cm), and nipple-to-inframammary fold distance (cm).Lastly, operative measures including anesthesia time, American Society of Anesthesiologists class, and resection weight (g) were recorded.These patient-level and operative variables were measured due to the association of certain variables with postoperative wound complications and morbidity, such as dehiscence and delayed wound healing.Subjects were additionally interviewed at each postoperative follow-up visit and charts were retrospectively reviewed to assess the occurrence of adverse events.

Postoperative Nascent Scar Measurement
Healing of the vertical incision was measured by 3-dimensional (3D) imaging.Advanced wound imaging and analytics were used to measure the vertical incision 2, 4, 6, and 8 weeks postoperatively to track the progression of healing over time (Figure 5).Measurements were taken with an eKare Insight device (eKare Inc., Fairfax, VA) and included healing scar depth (cm), surface area (cm 2 ), and volume (cm 3 ).Ghost overlays and uniform patient positioning were employed to ensure healing incisions were captured from the same position and perspective across follow-up visits.Although the eKare system employs automatic, algorithmic tracings of active wounds, investigators also reapproximated the tracing of incisions if necessary to ensure the accuracy of tracings.The device offers moderate to high levels of intra-and interrater reliability for area and volume and is considered a validated tool for this purpose. 20,21

Clinical Assessment of Nascent Scar Formation and T-junction Healing
Postoperative healing of the vertical incision and T-junction were each assessed clinically.The vertical incision was defined as the treated area undergoing intervention, from the inferior pole of the nipple-areolar complex to the inframammary fold.We defined the T-junction as the immediate trifurcation of the vertical and inframammary fold incisions, measured in cm.Delayed healing at the T-junction was defined at a threshold of clinical significance, ≥1 cm × 1 cm (1 cm 2 )."Early dehiscence" was used to describe wound healing during the 2-to 8-week postoperative period when susceptibility to dehiscence is typically observed.

Statistical Analysis
The secondary endpoint discussed in this preliminary report did not have a predetermined, powered sample size.The sample size calculation for this study was determined by the primary outcome: Observer Scar Assessment Scale Score (POSAS-O).The overall study will enroll 42 patients which will allow us to detect a moderate effect (Cohen's d = 0.5) in scar quality measured by POSAS-O with 80% power, accounting for an estimated 20% loss of patients.The initial power calculation included loss to follow-up, and this analysis was planned once enough patients had been recruited without the lost-to-follow-up inflation.This was decided post hoc given the challenges of performing research during the COVID-19 pandemic.
Statistics were performed by study investigators with GraphPad Prism9 (Graph Pad Software, Boston, MA) and by biostatisticians with R (R Foundation for Statistical Computing, Vienna, Austria) at the UT Southwestern Biomedical Informatics Core Facility.Shapiro-Wilk normality testing confirmed the appropriateness of parametric testing to assess 3D wound metrics; multiple paired t-tests were used to compare nascent scar area, volume, and maximum depth between breasts during the intervention period.The 2-stage step-up method of Benjamini, Krieger, and Yekutieli was employed to identify the potential for false discovery in our 3D measurement analysis, with a desired false discovery rate Q set to 1%.Multivariable linear regression was performed in post hoc analyses to assess the relationship between patient variables and variations.Univariate analysis was completed with analysis of variance and subsequent bootstrapping completed to assess for variables potentially contributing to postoperative wound area.Binomial testing was employed to assess the significance between observed and expected rates of T-junction dehiscence between treatment groups.A P-value <.05 was considered statistically significant.

RESULTS
Between October 2021 and March 2023, 34 patients (n = 68 breasts) were enrolled in the study and are included in this preliminary analysis of postoperative healing (Figure 6).The

Clinical Assessment of T-junction Healing
Of the 68 breasts in the study, 12 (17.6%)had clinically significant T-junction wound dehiscence ≥1 cm 2 during the 8-week intervention period (Table 5).Of the 12 T-junction wounds, there was an increased rate of T-junction wound dehiscence in SOC breasts (11 breasts, 91.67%) compared with FMTB breasts (1 breast, 8.3%) (Supplemental Figure 1); this difference was statistically significant (P = .006).Matched-pairs testing confirmed there was an association between closure used and the risk of wound dehiscence (P = .009),with an odds ratio of 0.091 (95% CI, 0.002, 0.625) and a number needed to treat of 3 breasts (ie, approximately 2 patients) (Table 6).Of the 12 breasts
As expected, post hoc analysis showed a statistically significant difference between Week 8 vertical incision nascent scar area in the 11 SOC breasts with clinically significant T-junction dehiscence on exam (Supplemental Figure 3A).Moreover, the area of the affected SOC breast area exceeded that of the contralateral FMTB breast by 0.69 cm 2 (95% CI, 0.1571, 1.22 cm 2 ; P = .0087)(Supplemental Figure 3B).

Multivariate Linear Regression
To determine whether nascent scar area was additionally affected by patient-level variables, we constructed a linear regression model to evaluate whether variables including closure, resection weight, sternal notch-to-nipple distance,

Nascent Scar Volume
Overall, mean vertical incision volume (Table 9) was decreased in the FMTB breast (0.1 cm 3 ) compared with the SOC breast (0.2 cm 3 ) during the 8-week intervention period, and this was statistically significant (P = .007)(Supplemental Figure 4).

Nascent Scar Maximum Depth
Similarly, the mean maximum depth (Table 10) of the healing incision was slightly increased in the SOC breast (0.09 cm) compared with the FMTB breast (0.07 cm) but this difference was not statistically significant (P = .08)overall.

DISCUSSION
This study provides significant clinical evidence that postoperative mechanomodulation to effectively reduces the incidence of wound complications and the size of healing incisions postoperatively.We hypothesize that, in addition to the benefits of offloading mechanical forces externally, the FMTB helps to maintain adequate perfusion to the distalmost aspects of the lateral and medial flaps, reducing rates of T-junction wound dehiscence during the postoperative period.This difference was further characterized by 3D imaging analysis of the treatment site, which established statistically significant reductions in nascent scar area, depth, and volume in vertical incisions closed with the FMTB.Although mechanical stress can induce the formation of pathologic scars, it is also important for normal wound healing. 22Studies have shown that the tensile strength of tissue after cutaneous injury is linked to the mechanical strength it endures during the wound healing process. 22Cremers et al found that nonsplinted excisional wounds closed more quickly than splinted wounds. 23They concluded that the removal of mechanical stress delays wound closure 3.3 times in comparison to wounds exposed to mechanical stress. 23Other studies have shown that mechanical forces are important for postoperative collagen deposition, neoangiogenesis, and fibroblast migration. 24he importance of mechanical stress and loading is the molecular basis of, for example, early mobilization after joint surgery. 11Thus, an ideal mechanomodulatory device to support postoperative wound healing might attenuate incisional tension to reduce the risk of complications without completely removing mechanical stress.
Mechanomodulation additionally plays a role in wound healing; innovation and novel techniques to improve postoperative wound outcomes are also warranted, especially in aesthetic surgery where wound morbidity can predict scar cosmesis.One device, the Zipline (Zipline Medical, Inc., Styrker Corporation, Kalamazoo, MI), approximates skin edges after surgery and offsets skin tension. 25ike the FMTB, it can also be used as an alternative to superficial sutures and is positioned immediately after surgery.7][28] A 2020 metaanalysis comparing the Zipline to suture closure found a decreased rate of skin/soft tissue infection and decreased incision closure time but did not find a significant difference in rates of dehiscence. 25Additionally, the study did not involve patients undergoing breast surgery.
Other hypothesized contributors to incisional dehiscence besides excess mechanical stress include variations in surgical technique and low relative perfusion at the healing site. 29Because patients in this study were selfcontrolled, we considered the role of the surgeon's technique to be negligible.Additionally, the unmasking of randomization only occurred after approximation and closure of the deep tissue layers, when final dermal closure was to begin.The role of perfusion, however, has been described as a contributor to early wound dehiscence in elective cosmetic and body contouring procedures. 29or example, a recent study showed rates of clinically meaningful wound dehiscence were higher in a breasts undergoing standard dressing after Wise-pattern reduction mammaplasty compared with those receiving closed incisional negative-pressure therapy for 6 days after surgery. 29imilar to our study, 15 incidences of wound dehiscence, the authors found 14 (93%) occurred in breasts undergoing SOC dressing, while 1 (7%) occurred in a breast treated postoperatively with closed incisional negative-pressure therapy; however, this study was not self-controlled. 29As studies have shown that negative-pressure wound therapy supports cutaneous microcirculation and perfusion after injury, the reduced rate of dehiscence in this study is particularly interesting. 30,31However, Cochrane reviews assessing negative-pressure therapy across surgical subspecialties have shown a low level of evidence for postoperative wound healing. 32,33Distal flap edges are at risk for   Only closure-type was significantly associated with variations in nascent scar area by the end of the intervention period (P = .0059).
epidermolysis or necrosis in breast surgery due to their relative distance from the pedicle or random-pattern blood supply, [34][35][36] and the resulting poor tissue quality can cause dehiscence. 37Sutures also have the potential to contribute to relative tissue ischemia. 38iven the myriad variables which influence wound healing and scar formation-ie, genetics, environment, nutrition, anatomic location-within-subject controls allowed objective comparison of wound healing and scar quality between breasts in the context of the individual patient.The reduction mammaplasty was chosen as the clinical model due to the frequency of the procedure, the relative ease of experimental device application, the ability for bilateral assessment of experimental closure and control, and because the vertical incision was a surgical site of relatively uncomplicated healing.
The area, volume, and depth of healing incisions closed by FMTBs were significantly decreased overall compared with SOC closure during the postoperative intervention period.The omnipresence of early T-junction dehiscence during the postoperative period presents a vexing challenge for plastic surgeons. 39Overall, our decreased rate of wound dehiscence in the FMTB breast (1.47%) marks a significant statistical and clinical departure from rates reported in the literature. 40Additionally, after adjusting for other patient variables, we found only closure significantly affected variations in the area of healing incisions.1][42][43][44][45] A recent retrospective study identified a relationship between BMI and wound healing greater than 2 months. 46The reduced rates of dehiscence and smaller nascent scar areas observed with this device after controlling for key variables, including race, resection weight, BMI, and ptosis, suggest its clinical efficacy.Additionally, with a calculated number needed to treat of 3 breasts, 2 patients treated with incisions closed with FMTBs would prevent the occurrence of 1 dehisced incision, indicating the potential to significantly support clinical outcomes in this patient population.
Our study is not without limitations.First, as visits took place during the COVID-19 pandemic, patients were only able to attend Week 4 and Week 6 visits virtually, where they were clinically examined remotely and were supervised in the removal and replacement of FMTBs.This upheld patient autonomy and comfort.At these time points, if patients attended virtually, 3D measurement data were not collected.Thus, we report findings from those patients able to attend all 4 visits during the 8-week intervention period.Second, a brief learning curve is required to use the FMTB effectively.Patients worked with investigators to gain familiarity with the device during initial screening visits in a hands-on practice session.Each subject received multiple packs prior to surgery with which they could practice or use to teach loved ones potentially helping with postoperative care.Additionally, the nascent scar depth data calculated from the eKare data have lower inter-and intrarater reliability compared with nascent scar area and volume measurements, according to published reports.The data

Figure 1 .
Figure 1.Force modulating tissue bridge applicator and device.

Figure 2 .
Figure 2. Subject randomization and group allocation workflow.Patients were self-controlled to account for innate differences in wound healing and scar quality.FMTB, force modulating tissue bridge; SOC, standard of care.Figure created using Biorender.com.

Figure 3 .
Figure 3. Force modulating tissue bridge placement along vertical incision of 27-year-old female patient after Wise-pattern reduction mammaplasty.Following inverted interrupted dermal closure with 3-0 Monocryl (Ethicon, Raritan, NJ) along the vertical incision, force modulating tissue bridges were applied for final tissue approximation and superficial closure on the experimental breast.

Figure 4 .
Figure 4.A 27-year-old female patient undergoing Wise-pattern reduction mammaplasty with stand-of-care closure shown.In the control breast, inverted interrupted dermal closure was completed with 3-0 Monocryl (Ethicon, Raritan, NJ) suture along the vertical incision.Afterward, 4-0 running subcuticular Monocryl sutures were used for final tissue approximation and superficial closure on the contralateral incision, serving as a within-subject control.

Figure 6 .
Figure 6.Flow diagram of clinical trial.34 patients were included in our preliminary analysis.FMTB, force modulating tissue bridge.Figure created with Biorender.com.

Figure 7 .
Figure 7. Clinical assessment of the vertical incision of a 35-year-old female patient during the postoperative intervention period.(A) Force modulating tissue bridge breast at 2-week follow-up and (B) at 4-week follow-up.(C) Standard-of-care breast at 2-week follow-up and (D) at 4-week follow-up.

Figure 8 .Figure
Figure 8. Clinical assessment of the vertical incision of a 34-year-old female patient during the postoperative intervention period.(A) Standard-of-care breast at 2-week follow-up and (B) at 4-week follow-up.(C) Force modulating tissue bridge breast at 2-week follow-up and (D) at 4-week follow-up.

Figure 10 .
Figure 10.eKare analysis of a vertical incision in a 55-year-old female.(A) Interface for three-dimensional measurement of a vertical incision closed with an FMTB.Metrics included in our analysis included nascent scar area, volume, and maximum depth during the 8-week postoperative intervention period.(B) Interface for three-dimensional imaging analysis of a vertical incision closed according to SOC.Metrics for FMTB and SOC breasts were recorded biweekly and analyzed by paired parametric testing.FMTB, force modulating tissue bridge; SOC, standard of care.

Table 1 .
Study Inclusion and Exclusion Criteria

Table 2 .
Demographic Variables Between Treatment Allocation Groups

Table 3 :
Anthropometric Measures and Resection Weight of Treatment and Control Breasts FMTB, force modulating tissue bridge; SEM, standard error of the mean; SOC, standard of care.

Table 4 .
Study Follow-up During 8-week Intervention Period

Table 5 .
Contingency Table Illustrating Breasts With Clinically Significant T-junction Dehiscence According to the Type of Dermal Closure Used

Table 7 .
Nascent Scar Area During the 8-week Postoperative Wound Support and Intervention Period

Table 8 .
Multivariate Linear Regression Results, Assessing Relationship Between Predictor Variables and Area at the End of the 2-Month Intervention Period

Table 9 .
Mean Vertical Incision Volume During the Postoperative Intervention Period

Table 10 .
Mean Maximum Depth of Nascent Scar Depth During the Postoperative Intervention Period for FMTN Treatment and SOC Closure Breasts FMTB, force modulating tissue bridge; SEM, standard error of the mean; SOC, standard of care.