INTRODUCTION
Prepectoral breast reconstruction (PBR) has recently gained popularity due to its numerous benefits, including reduced postoperative pain, elimination of animation deformity, and lower rates of capsular contracture when acellular dermal matrix (ADM) coverage is used. Additionally, the procedure requires less operative time and has a reduced risk of bleeding since dissection of the submuscular plane is unnecessary. However, despite these advantages, PBR has a significant limitation related to viability, which depends on adequate perfusion of the mastectomy skin flap and sufficient soft tissue coverage [1].
The P1 method has been developed to address the limitations of the PBR by preventing rippling and improving the contour of the upper pole [2]. Unlike procedures using the submuscular plane, the P1 PBR technique involves covering the upper pole of the implant by dissecting only the superior slip of the pectoralis major muscle. Pittman et al. [2] have classified implant placement in PBR, defining the P1 method as a muscle-sparing prepectoral approach with anterior ADM coverage. This differs from the P0 method, which is a complete prepectoral approach with full ADM wrapping. Although the P1 method offers significant advantages over P0, it requires a longer operative time due to the elevation of the superior pectoralis major muscle slip.
Pectoralis major muscle dissection can be performed using monopolar electrocautery surgery scalpels, such as the Bovie. However, since this method involves electrical current, it can lead to irregular muscle contractions, complicating precise dissection and promoting muscle bleeding [3,4]. This issue raises concerns about postoperative bleeding. During prosthetic breast reconstruction, bleeding may lead to further complications, including capsular contracture or infection. Ultrasonic dissection devices offer a more user-friendly alternative, producing less heat and sealing blood and lymphatic vessels through ultrasonic vibrations [5].
Ultrasonic dissection devices, which do not utilize electrical currents that induce muscle contraction, allow surgeons to manipulate muscles more easily, thereby yielding more precise results [6].
The purpose of this study was to share our experience with using an advanced ultrasonic dissection device, specifically the harmonic scalpel (HS), as opposed to a monopolar electrocautery device in the P1 method, aiming to reduce operative time and bleeding risk.
METHODS
Study design
Patients who underwent PBR from June to September 2021 at our institution were retrospectively reviewed. This study received approval from the Institutional Review Board of Yonsei University Severance Hospital (IRB No. 4-2023-0711). We divided a total of 39 patients into two groups: the P1 group underwent reconstruction using the P1 method with an ultrasonic HS, and the P0 group underwent traditional PBR. All procedures were performed directly on the implant. The exclusion criteria included poorly vascularized mastectomy skin flaps, morbid obesity, immunocompromised status, uncontrolled diabetes mellitus, and tumors involving the chest wall. The superior slip of the pectoralis major muscle was carefully dissected using an HS, which helped control muscle bleeding. The surgical procedure for the P1 method, which utilizes ultrasonic dissection devices, is detailed in Supplementary Video 1. The data collected included patient demographics, type of mastectomy, specimen weight, implant size, ADM type, adjuvant chemotherapy, and postmastectomy radiation therapy. We also compared changes in surgical time between the groups. Surgical outcomes were assessed based on the presence of rippling, capsular contracture (grade III or IV), and animation deformities. We quantified complications such as seroma, hematoma, and mastectomy skin flap necrosis. Patients attended the outpatient clinic approximately 1, 3, and 6 months post-surgery for physical examinations and photography. The operator evaluated factors such as implant edge visibility, superior sunken breast, and implant rippling.
All statistical analyses were conducted using IBM SPSS Statistics for Windows, version 29 (IBM Corp.). We compared the demographic information of two groups—the P1 method with ultrasonic dissection devices and the prepectoral group—using the Fisher exact test for categorical variables and either the Mann-Whitney U test or the independent t-test for continuous variables. For each scale, the median, range, mean, and standard deviation of the scores were reported. Statistical significance was established at P<0.05.
Surgical technique
For patients who underwent total mastectomy, indocyanine green was administered intravenously at a dosage of 0.1 mg/kg to assess the perfusion of the mastectomy skin flap using Fluobeam (Fluoptics). Clinicians checked for adequate perfusion by looking for signs of venous congestion or ischemia. If good perfusion of the mastectomy skin flap was confirmed, direct implant insertion using the P1 method was planned. Patients who transitioned to an implant after an initial tissue expander insertion did not undergo evaluation with Fluoptics, as their mastectomy skin flap was considered stabilized.
The level of dissection was planned to reach the P1 plane at the superior bundle of the pectoralis major muscle. According to Pittman et al. [2], this level is approximately 2 cm caudal to the clavicle, and the partial thickness of the muscle was elevated to prevent animation deformities. The pectoralis muscle slip was grasped and dissected from medial to lateral, parallel to the muscle fibers, using a HS. Care was taken to avoid damaging the thoracoacromial neurovascular bundle. Once the dissection at the P1 plane was complete, an implant of appropriate volume was selected based on the preoperative 3D volume measurements and the weight of the breast tissue postmastectomy (Figs. 1, 2). The chosen implant was either fully encased in ADM or wrapped anteriorly and partially on the posterior side. Prior to implant insertion into the breast pocket, the area was irrigated with antibiotic-mixed saline and re-sterilized using betadine to prevent infection. The implant was then placed into the breast pocket, with the superior portion covered by the elevated pectoralis major muscle slip, which was anchored to the muscle using Vicryl #3-0 (Fig. 3). Finally, bleeding was meticulously controlled using a HS, a drainage tube was placed, and the incision was closed in layers.
RESULTS
During the study period, 17 breasts underwent P1 direct-to-implant (DTI) reconstruction, while 22 breasts underwent P0 DTI reconstruction. The P1 DTI method was performed after August 2021, whereas P0 DTI was performed before this time. Five patients underwent bilateral reconstruction, and 34 underwent unilateral reconstruction. Patient characteristics are detailed in Table 1. The median age at the time of reconstruction was 52.0 years (range, 28–73 years) in the P1 group and 48.5 years (range, 30–70 years) in the P0 group. The average follow-up duration was 259.18 days for the P1 group and 334.72 days for the P0 group. There was no significant difference in postmastectomy radiotherapy between the two groups, with three cases in the P1 group and six in the P0 group. The demographics of the patients were similar across both groups.
Three types of ADMs were utilized in the study: CGCryoDerm, DermACELL, and MegaDerm (Fig. 4). The average weight of the mastectomy specimens was 422.06 g in the P1 group and 285.95 g in the P0 group, with no significant difference observed between the two (P>0.05). The average implant sizes were 318.82 cc in the P1 group and 315.23 cc in the P0 group. Although the average operation time was longer in the P1 group than in the P0 group (104.35 minutes vs. 90.05 minutes), this difference was not statistically significant (P=0.095) (Table 2).
Supplementary Video 1 shows the P1 technique, demonstrating the absence of muscle movement during the elevation of the pectoralis major muscle slip. This allows for a more comfortable and precise operation with reduced bleeding.
The aesthetic outcomes were generally favorable, with no instances of animation deformity observed in either group. Ripping occurred in 23.5% (4 out of 17) of the P1 group and 36.4% (8 out of 22) in the P0 group (P=0.389). None of the patients in the P1 group experienced capsular contracture, whereas 9.1% of the patients in the P0 group developed grade >III capsular contracture (Table 3). However, none of these outcomes reached statistical significance.
Postoperative complications were evaluated based on the occurrence of hematoma, seroma, infection, and the necessity for minor or major reoperations. Minor reoperations were confined to revision surgery addressing partial skin necrosis. Major reoperations encompassed both implant explantation and implant replacement. In the P1 group, only one patient developed a seroma, which did not necessitate surgical drainage. Additionally, another patient in the P1 group required minor revision surgery for partial skin necrosis following a nipple-sparing mastectomy and DTI reconstruction. In contrast, no patients in the P0 group experienced seroma or underwent minor revision surgery. There were no instances of postoperative hematoma, infection, implant exchange, or implant explantation in either group.
DISCUSSION
Pittman et al. [2] initially introduced the P1-based PBR, which offers several advantages over the complete prepectoral plane, including minimized upper pole rippling and enhanced visibility of the implant edges. When compared to the submuscular plane using an ADM sling, this approach reduces both operative time and postoperative pain, and it eliminates the occurrence of animation deformity caused by muscle contraction. However, when compared to the P0 prepectoral plane, P1-based PBR requires a longer operative time and demands greater surgical skill to prevent injury to the neurovascular bundle during the elevation of the muscle slip.
To overcome the limitations of the P1 method, we incorporated ultrasonic dissection devices as effective tools for elevating the pectoralis major muscle during implant-based breast reconstruction. These devices convert high-frequency ultrasonic waves into mechanical energy [7]. When compared to electrocautery, harmonic dissection offers multiple benefits, including reduced scar formation relative to traditional blades, minimal collateral thermal damage to surrounding tissues, no smoke production (though a transient mist may occur), no stimulation or damage to motor nerves in the axilla, and suitability for use in patients with pacemakers [8]. HS is extensively employed for efficient tissue resection and hemostasis in procedures such as colon surgery, laparoscopic cholecystectomy, and thyroid operations. In the pectoralis major myocutaneous flap group, there was a significant reduction in operative time, blood loss, drainage volume, and morbidity compared to the electrocautery group [9]. Another study found that using ultrasonic dissection devices during capsulectomy resulted in lower total drainage volumes and shorter drainage times than those seen with monopolar cautery [10]. Burdette et al. [11] demonstrated that HS could serve as an alternative to electrocautery devices, offering benefits such as decreased time for resection or hemostasis, reduced serous drainage, and less postoperative pain. Given the proven effectiveness of HS, we have applied this technology to the P1 method for PBR.
Different from the surgical procedure described by Pittman et al., we aimed to maximize the coverage of the implant [12]. Various methods for wrapping the implant with ADM in PBR have been published, yet standardization remains elusive. We utilized square or rectangular ADM to cover the implant as extensively as possible. Due to the limited availability of ADM, only the anterior and partial posterior sides of the larger prostheses could be wrapped. When sufficient ADM was available to fully encase the implant, we employed either a square-shaped ADM or a technique involving two overlapping rectangular ADMs (Fig. 4) [6,13].
The two surgical tools appeared to have no effect on the rates of capsular contracture or rippling. Additionally, there were no instances of hematoma in either the P1 with HS or the P0 groups. The operative time was slightly shorter in the P0 group, although the difference was not statistically significant (104.35 minutes in the P1 group vs. 90.05 minutes in the P0 group, P=0.095). We hypothesize that the longer surgical time in the P1 group was due to the dissection of the superior slip of the pectoralis muscle, a procedure not performed in the P0 group. Furthermore, the lack of a statistically significant difference in average operative times between the two groups may still be noteworthy. While the use of HS increases costs, we believe the benefits outweigh these because reimbursement by National health insurance is possible. This not only alleviates the financial burden on cancer patients but also allows the surgeon to operate with greater convenience and accurately.
In conclusion, P1-based PBR offers several advantages over traditional PBR techniques, including reduced upper pole rippling and enhanced visibility of the implant edges. However, it may lead to increased surgical time due to muscle elevation, as well as potential complications such as muscle bleeding, involuntary muscle movements from nerve stimulation, and neurovascular injury. Our experience has shown that using ultrasonic dissection devices to elevate the superior pectoralis muscle slip can mitigate these drawbacks. Future research should evaluate the aesthetic outcomes, complications, and operative times in a larger cohort and compare them with results obtained using an electrocautery device.
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