Pure skin perforator flap direct elevation above the subdermal plane using preoperative ultra-high frequency ultrasound planning: A proof of concept

Designing Perforator Flaps Using Ultrasound

Microsurgeons have today the freedom of the "chosen flap," as opposed to the "flap of choice," but the preoperative knowledge of the microanatomy of each patient is mandatory. The need for preoperative evaluation of the perforators, not only in terms of position, but also for dimensions, flow, and relationship with the surrounding structures became essential and allows more personalized reconstruction, less invasiveness, more safety and finally increase microsurgeon creativity.

The Past, Present, and Future of Perforator Flaps in Head and Neck Surgery

A perforator is a vessel that travels through muscle and perfuses the skin. Perforator flaps require intramuscular dissection and can be used as pedicled or free flap. With improved understanding of microvasculature, they can be tailored to have multiple skin paddles, multiple components, or shaped to conform to any defect. Reliable perforator flap-based reconstruction is a meticulous microvascular technique, ultimately allowing the surgeon to harvest any flap in a freestyle fashion and transplant to any recipient vessel. New technologies improve the safety and reproducibility of this type of reconstruction.

Subdermal dissection technique for pure skin SCIA and ALT perforator flaps in burns and trauma defects: Clinical experience

BACKGROUND

The pure skin perforator (PSP) flap is gaining popularity for its remarkable thinness. The subdermal dissection technique was recently introduced, allowing for a quicker elevation of a PSP flap. In this report, we present our two-year experience utilizing subdermal dissection for harvesting PSP flaps.

METHODS

All patients who had undergone PSP flap reconstruction at our hospital from February 2021 to February 2023 were included. Demographic data, intraoperative variables, flap characteristics, and postoperative outcomes were collected. Surgical planning involved locating the perforator using ultrasound and harvesting the flap using the subdermal dissection technique.

RESULTS

A total of 26 PSP flap reconstructions were conducted on 24 patients aged between 15 and 86 years. The flaps were based on perforators issuing from the superficial circumflex iliac artery in 24 cases, and from the descending branch of the lateral circumflex femoral artery in 2 cases. Flap sizes ranged from 3 × 1.5 cm to 19 × 6 cm, with a mean thickness of 3.48 mm. The average time for flap harvest was 131.92 min. Postoperatively, we observed four cases of partial necrosis, 1 total flap loss, and 2 instances of vascular thrombosis at the anastomosis site. The flaps exhibited good pliability without contracture, and no debulking procedures were required during the follow-up period (minimum 6 months, range 6-24; mean 9.4615).

CONCLUSION

The subdermal dissection technique is a safe and efficient approach for elevating PSP flaps. Our initial experience with this technique has been encouraging, and it currently serves as our preferred reconstructive option for defects requiring thin reconstruction.

Evolution and Application of Ultrasound for Flap Planning in Upper Extremity Reconstruction

Accurate preoperative localization of dominant perforators provides crucial information about their location and diameter, leading to reduced surgical time, improved flap viability, and decreased complications. Ultrasound has increased in popularity in recent years, with the advantages of providing reproducible, accurate, cost-effective, and real-time information while reducing radiation exposure. Precise preoperative mapping of perforators allows for rapid and safe elevation of suprafascial, thin, and superthin flaps. This review focuses on the role of ultrasound as a tool for preoperative flap planning in the upper extremities.

Planes for Perforator/Skin Flap Elevation-Definition, Classification, and Techniques

BACKGROUND

 Elevation in different layers achieving thin flaps are becoming relatively common practice for perforator flaps. Although postreconstruction debulking achieves pleasing aesthetic results and is widely practiced, customized approach during elevation to achieve the ideal thickness will increase efficiency while achieving the best possible aesthetic outcome. Multiple planes for elevation have been reported along with different techniques but it is quite confusing and may lack correspondence to the innate anatomy of the skin and subcutaneous tissue.

METHODS

 This article reviews the different planes of elevation and aims to clarify the definition and classification in accordance to anatomy and present the pros and cons of elevation based on the different layers and provide technical tips for elevation.

RESULTS

 Five different planes of elevation for perforator flaps are identified: subfascial, suprafacial, superthin, ultrathin, and subdermal (pure skin) layers based on experience, literature, and anatomy.

CONCLUSION

 These planes all have their unique properties and challenges. Understanding the benefits and limits along with the technical aspect will allow the surgeon to better apply the perforator flaps.

Perforator Mapping and Clinical Experience with the Superthin Profunda Artery Perforator Flap for Reconstruction in the Upper and Lower Extremity

INTRODUCTION

Thin skin flaps have gained popularity for extremity reconstruction. However, the use of the profunda artery perforator (PAP) flap has not been explored as much. With its concealed donor site on the medial thigh and bulk, the PAP has become popular for reconstruction in the breast, head, and neck. The thickness of the subfascial PAP flap is decreased through elevation on the thin or superthin plane, making it more suitable for extremity reconstruction.

METHODS

A consecutive series of 28 patients with 29 flaps who received a thin or superthin single perforator PAP flap for upper or lower extremity reconstruction was reviewed. Our technique for preoperative localization of the dominant perforator using computed tomography angiography (CTA) and color duplex ultrasonography (CDU) is described.

RESULTS

Flap success rate was 93.1%. Mean flap artery diameter, vein diameter, area, and thickness were 1.7 + 0.4 mm, 2.2 + 0.4 mm, 157.3 + 52.1 cm², and 0.7 + 0.2 cm, respectively. Skin thickness at the suprafascial bifurcation point of a dominant "T" perforator measured on preoperative CTA correlated with actual intraoperative flap thickness. Patient body mass index did not correlate with flap thickness.

CONCLUSIONS

The thin and superthin PAP flap has multiple favorable characteristics, making it suitable for extremity reconstruction, and it has become the workhorse skin flap in our institution. Conventional low-frequency CDU together with CTA can be used effectively to map the dominant perforator preoperatively, allowing accurate flap design and rapid flap harvest.

LEVEL OF EVIDENCE

Therapeutic Level IV.

Lymphatic Tissue Transfer: Ultrasound-Guided Description and Preoperative Planning of Vascularised Lymph Nodes, Lymphatic Units, and Lymphatic Vessels Transfers

Background: The modern concept of lymphatic transfer includes vascularised lymph node transfer (VLNT), lymphatic vessels transfer (lymph interpositional flap transfer, LIFT) and lymphatic system transfer (vascularised lymph nodes and afferent lymphatics, LYST). The aim of this paper was to report our experience with different types of lymphatic transfer. Patients and Method: From June 2016 to June 2020, 30 consecutive patients affected by extremity lymphedema and 15 patients affected by post-traumatic lower extremity soft tissue defects, underwent lymphatic transfer (VLNT, LYST or LIFT). All cases were preoperatively evaluated by both high frequency and ultra-high frequency ultrasound. Flap features were recorded, as well as qualitative and quantitative outcomes at 1 year postoperative. Results: The mean postoperative lymphedema index reduction was 7.2 ± 5.7 for upper extremity and 20.7 ± 7.1 for lower extremity. No dismission of compression garments occurred, 12 patients (26%) referred more stable results of physical treatment and 1 case showed a 1-class compression reduction. All the LIFTs aimed as preventive did not develop post-traumatic lymphedema. In all cases of distal placement of VLNT and/or LYST, patients were dissatisfied with the aesthetic appearance of reconstruction, while no donor site scar disappointment was referred. Conclusion: When LVA is not feasible, LTT may represent a valid treatment option. This report was aimed at comprehensively describing and assessing how different lymphatic tissue transfer modalities may fulfil the different reconstructive needs of lymphedema patients.

Using Duplex Ultrasound for Recipient Vessel Selection

INTRODUCTION

 Among the many factors involved in reconstructive microsurgery, identifying a good recipient vessel is one of the key elements leading to a successful result.

MATERIAL AND METHOD

 Multiple modalities have been used to identify recipient vessels from simple palpation of axial arteries to hand-held Doppler, duplex ultrasound, computed tomography angiograms, and other advanced techniques. Although these various modalities bring their own unique advantages, using the duplex ultrasound can provide far superior and real-time information based on the anatomy and physiology of the recipient vessel.

RESULT

 Duplex ultrasound is a valuable and powerful tool for reconstructive surgeons who are interested in performing microsurgery or supermicrosurgery.

CONCLUSION

 As we enter the era of individualized/customized reconstruction using superthin flaps, perforator-to-perforator anastomosis, and supermicrosurgery, understanding and becoming versatile with duplex ultrasound will be critical especially in choosing recipient vessels.

Technical Aspects of High-Resolution Color-Coded Duplex Sonography for the Design of Perforator Flaps

BACKGROUND

 Technical aspects are of utmost significance for an efficient execution in designing perforator flaps with high-resolution color-coded Duplex sonography (CCDS). The following study evaluates decisive factors for a successful microvessel examination conducted by the microsurgeon.

METHODS

 Technical knowledge presented in this study was based on a series of more than 200 perforator flaps planned with CCDS. Flap reconstructions were performed at the University Hospital Regensburg, Germany, from July 2013 to January 2021. Standard high-resolution ultrasound (US) devices with linear multifrequency transducers of 4 to 18 MHz were used. Modes and device settings were evaluated regarding applicability by microsurgeons. Key steps for safe perforator identification and further optional steps for additional assessment should be discriminated.

RESULTS

 Different US modes including brightness mode (B-mode), color flow (CF), power Doppler (PD), pulse wave (PW), and blood flow (B-Flow) were used. Transducers from 15 MHz and up were favorable to detect microvessels. Knobology of a standard US device regarding buttons, switches, and specific onscreen options with relevance for perforator mapping was subcategorized in four different groups. For qualitative and quantitative evaluation of microvessels, different US modes were tested with respect to their usefulness.Vital elements of the CCDS exam are disaggregated into three key steps for safe perforator identification and three optional steps for further perforator characterization. A standardized protocol for the CCDS exams was applied. Downregulation of pulse-repetition frequency/scale to adapt device sensitivity to slow-flow velocities represented the most important criterion to visualize microvessels.Qualitative microvessel evaluation was performed in B-mode, CCDS, PD mode, and B-Flow mode. Quantitative assessment was executed using PW-mode and CCDS measuring the microvessels' diameter (mm) and flow characteristics. Quantitative information may be obtained using PW-mode and the distance-measuring tool in CF-mode.

CONCLUSION

 Technical aspects with respect to proper device trimming and application decisively impact CCDS-guided perforator vessel identification and evaluation.

Designing Anterolateral Thigh Flap Using Ultrasound

BACKGROUND

 Preoperative knowledge of themicrovascular anatomy of a patientmay improve safetyand efficacy and reduce morbidity. Today, with the advancement in technology, ultrasound can provide minute details of the structures within the body, which makes this technology very helpful in preoperative evaluation of the traditional perforator flaps as well as thin, superthin, and pure skin perforator flaps.

METHODS

 In this article, we will describe the design of one of the most popular perforator flaps, the anterolateral thigh (ALT) flap, using high-frequency and ultrahigh-frequency ultrasound technology.

RESULTS

 Ultrasound technology allows to study preoperatively the ALT donor-site and its microvascular anatomy by using different US modalities in order to provide a virtual surgical plan to the operating surgeon.

CONCLUSION

 Ultrasound technology allow to expand preoperative knowledge of flap microvascular anatomy and its course within the subcutaneous tissue up to and within the dermis, allowing to select the best perforator for the given reconstruction and the plane of elevation for thin, superthin and pure skin perforator flap.

Recent Advances in Ultrasound Technology: Ultra-High Frequency Ultrasound for Reconstructive Supermicrosurgery

BACKGROUND

 Currently, microsurgeons are in the era of supermicrosurgery and perforator flap reconstruction. As these reconstructions frequently utilize vessels that are smaller than a single millimeter, understanding of location of lymphatic vessels and perforator anatomy preoperatively is essential. To change with the times, the role of ultrasound has changed from just an adjunct to primary imaging of the choice in reconstructive supermicrosurgery. Recently, a novel ultrasonographic technique involving the use of ultra-high frequency ultrasound (UHFUS) frequencies has entered the scene, and appears a promising tool in surgical planning.

METHODS

 The literatures on the applications of UHFUS in reconstructive supermicrosurgery were retrieved and reviewed from more than 60 literatures have been published on the surgical applications of UHFUS.

RESULTS

 Nine studies were retrieved from the literature on the applications of UHFUS in reconstructive supermicrosurgery. The articles report both application for lymphatic surgery and perforator flaps.

CONCLUSIONS

 UHFUS application involves an increasing number of reconstructive supermicrosurgery field. UHFUS is a valuable and powerful tool for any reconstructive surgeons who are interested in performing supermicrosurgery.

Subdermal Dissection for Elevation of Pure Skin Perforator Flaps and Superthin Flaps: The Dermis as a Landmark for the Most Superficial Dissection Plane

BACKGROUND

Pure skin perforator and superthin flaps have been reported and are becoming popular, as they allow one-stage thin skin reconstruction even from a thick donor site. However, currently reported elevation procedures use proximal-to-distal dissection requiring free-style perforator selection and primary thinning procedures. With distal-to-proximal dissection using the dermis as a landmark for dissection plane, it is expected that elevation of pure skin perforator or superthin flaps can be simplified.

METHODS

Patients who underwent pure skin perforator or superthin flap transfers with the subdermal dissection technique were included. Flaps were designed based on location of pure skin perforators visualized on color Doppler ultrasound, and elevated just below the dermis under an operating microscope. Medical charts were reviewed to obtain clinical and intraoperative findings. Characteristics of the patients, flaps, and postoperative courses were evaluated.

RESULTS

Thirty-six flaps were transferred in 34 patients, all of which were elevated as true perforator flaps (superficial circumflex iliac artery perforator flap in 29 cases, other perforator flaps in seven cases). Mean ± SD flap thickness was 2.24 ± 0.77 mm (range, 1.0 to 4.0 mm). Skin flap size ranged from 3.5 × 2 cm to 27 × 8 cm. Time for flap elevation was 27.4 ± 11.6 minutes. All flaps survived without flap atrophy/contracture 6 months after surgery, except for two cases of partial necrosis.

CONCLUSION

The subdermal elevation technique allows straightforward and direct elevation of a pure skin perforator or superthin flap within 30 minutes on average without the necessity of primary thinning.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Role of Ultrahigh Frequency Ultrasound in Evaluating Experimental Flaps

BACKGROUND

 Experimental flap follow-up needs faster, safer, and less invasive techniques that can be easily correlated to clinical procedures. For this reason, we aimed to test the role of ultrahigh frequency ultrasound in follow-up of flap viability. Further on, we aimed to analyze if the chimeric groin flap can be mobilized in a sandwiched position without affecting its vascular supply by twisting its pedicle.

METHODS

 A total of 12 male Wistar rats, split into three groups, were used. Group A (n = 4) had the chimeric groin flap repositioned in a sandwich position on the anterior abdominal wall and underwent ultrahigh frequency ultrasound follow-up at days 10 and 14. Group B (n = 4) also had the flaps sandwiched, however, at day 14 the vascularity of flaps was proven by infusion of nontargeted ultrasound contrast agents, after which flaps were sent for histological analysis. Group C (C1 n = 2, C2 n = 2) was the control group. In C1 the chimeric groin flap was harvested and sent for histology on day 0, acting as a histological benchmark of flap viability, and in C2 the chimeric groin flap was re-sutured in its anatomical position and after 14 days, flaps were harvested and sent for histological analysis, acting as a direct control for Group B.

RESULTS

 Ultrasound showed constant vascular flow in both adipose and skin flaps in the sandwiched position. Microbubble study showed diffuse perfusion within flaps. Ultrasound measurements of flow velocity, flap volume, and percentage of vascularity showed a decrease in flap volume and increase in vascularity over 14 days. Histology showed similar viability in both groups.

CONCLUSION

 Ultrahigh frequency ultrasound may be a valuable tool for postoperative flap assessment, while the chimeric flap can be moved freely in a sandwich position making it suitable for adding tissue substitutes within its components.

Feasibility study of preoperative microvessel evaluation and characterization in perforator flaps using various modes of color-coded duplex sonography (CCDS)

BACKGROUND

Color-coded duplex sonography (CCDS) is useful for perforator flap design showing the highest sensitivity in identifying microvessels. This prospective study evaluates the feasibility of different ultrasound (US) modes applied by the microsurgeon in daily practice suggesting quantifiable reference values.

METHODS

Twenty-four patients aged between 17 and 68 years (mean 43.3 ± 14.2 years) with 18 anterolateral thigh (ALT) and 6 superficial circumflex iliac artery (SCIP) flaps were included. Indications were traumatic (n = 12), infectious (n = 6), ischemic (n = 4), or tumor-associated defects (n = 2). Different US modes were evaluated regarding applicability using multifrequency linear probes (5-15 MHz). Vessels diameter, peak systolic velocity (PSV), end diastolic velocity (EDV), and resistance index (RI) were measured. Preoperative results were correlated to intraoperative findings.

RESULTS

In the examined patient group with 24 perforator flaps a 100% correlation was seen when comparing perforators detected with CCDS/PD with intraoperative findings using optimized US settings. Sensitivity, PPV, and accuracy of CCDS were 100% respectively. Mean PSV of 16.99 ± 6.07 cm/s, mean EDV of 5.01 ± 1.84 cm/s and RI of 0.7 ± 0.07 were measured in microvessels (PW-mode). CCDS proved to be superior compared to PD in correct diameter assessment showing a mean diameter of 1.65 ± 0.45 mm, compared to PD-mode 1.31 ± 0.24 mm. Mean PSV and EDV were higher in ALT than in SCIP flaps, RI was slightly higher in SCIP flaps (p > .05). There were no significant differences in size of different flaps' perforators (p > .05).

CONCLUSION

CCDS represents a highly valuable tool in the daily practice of free flap reconstructions using optimized low flow US settings and multifrequency linear probes.

Thin and superthin perforator flap elevation based on preoperative planning with ultrahigh-frequency ultrasound

The ability to directly harvest thin and superthin perforator flaps without jeopardizing their vascularity depends on knowledge of the microsurgical vascular anatomy of each perforator within the subcutaneous tissue up to the dermis. In this paper, we report our experience with ultrahigh-frequency ultrasound (UHF-US) in the preoperative planning of thin and superthin flaps. Between May 2017 and September 2018, perforators of seven patients were preoperatively evaluated by both ultrasound (using an 18-MHz linear probe) and UHF-US (using 48- and 70-MHz linear probes). Thin flaps (two cases) and superthin flaps (five cases) were elevated for the reconstruction of head and neck oncologic defects and lower limb traumatic defects. The mean flap size was 6.5×15 cm (range, 5×8 to 7.5×23 cm). No complications occurred, and all flaps survived completely. In all cases, we found 100% agreement between the preoperative UHF-US results and the intraoperative findings. The final reconstructive outcomes were considered satisfactory by both the surgeon and the patients. In conclusion, UHF-US was found to be very useful in the preoperative planning of thin and superthin free flaps, as it allows precise anticipation of very superficial microvascular anatomy. UHF-US may represent the next frontier in thin, superthin, and pure skin perforator flap design.

High-Resolution Ultrasound-Guided Perforator Mapping and Characterization by the Microsurgeon in Lower Limb Reconstruction

BACKGROUND

 Preoperative ultrasound (US)-guided perforator mapping has immensely simplified perforator flap planning. It may be executed by the microsurgeon. Device settings and selection of ultrasound modes are of utmost significance for detection of low-flow microvessels. The following study evaluates different US modes.

METHODS

 A prospective complete data acquisition was performed from July 2018 to June 2019 in a subset of patients who underwent US-guided flap planning. Multifrequency linear transducers were used applying five US modes. Brightness (B)-mode, color flow (CF), power Doppler (PD), pulse wave (PW), and B-flow modes were evaluated regarding applicability by microsurgeons. Peak systolic velocity (PSV), end diastolic velocity (EDV), and resistance index (RI) were chosen to evaluate flow characteristics. US results were correlated to intraoperative findings.

RESULTS

 A total number of eight patients (six males and two females) undergoing anterolateral thigh (ALT) or superficial circumflex iliac artery perforator (SCIP) flap surgery received an extensive standardized US-guided perforator characterization. Qualitative evaluation was performed in B-mode, color-coded duplex sonography (CCDS), PD, and B-flow mode. Quantitative assessment was executed using PW-mode and CCDS measuring the microvessels' diameter (mm) and flow characteristics (PSV, EDV, and RI). CCDS provided a mean diameter of 1.93 mm (range: 1.2-2.8 ± 0.51), a mean systolic peak of 16.9 cm/s (range: 9.9-33.4 ± 7.79), and mean RI of 0.71 (range: 0.55-0.87 ± 0.09) for lower limb perforators. All perforators located with US were verified by intraoperative findings. An optimized, time-effective US mapping algorithm was derived. Qualitative parameters may be evaluated with B-mode, CF, or B-flow. Smallest microvessels may be assessed in PD-mode. Lowering pulse-repetition frequency (PRF)/scale is mandatory to image low-flow microvessels as perforators. Quantitative information may be obtained using PW-mode and the distance-measuring tool in CF-mode. Image and video materials are provided.

CONCLUSION

 CCDS proved to be a powerful tool for preoperative perforator characterization when using a structured approach and mapping algorithm. Different techniques may be applied for specific visualizations and performed by the microsurgeon.