table 1. Overview of the strengths and weaknesses of each flap-assessment technique
Conclusion The primary goal of perioperative assessment is to ensure optimal flap perfusion, minimizing the risk of necrosis or flap loss. Despite technological advancements, direct clinical assessment remains the gold standard [79], emphasizing the importance of trained medical professionals in evaluating skin colour, temperature, turgor, and capillary refill. Our comparative analysis highlighted the strengths and weaknesses of both non-invasive and invasive techniques. Non-invasive methods, such as Acoustic Doppler Sonography (HHD), Near Infrared Spectroscopy (NIRS), Thermal Imaging (TI), and Photoplethysmography (PPG), excel in accessibility and safety. However, they may sacrifice specificity. Invasive techniques, including Contrast-Enhanced Ultrasound (CEUS), Computed Tomography Angiography (CTA), Near-Infrared Fluorescence Angiography with Indocyanine Green (ICG), and Implantable Doppler Probe, offer high accuracy but introduce additional risks or high cost. The choice of assessment technique should be tailored to the specific clinical scenario, considering factors like patient characteristics, procedural requirements, and the surgeon’s expertise. Recommendations for selecting appropriate techniques for different flap types involve weighing the advantages and limitations of each method against the clinical context. Looking ahead, areas for further research and development in flap assessment techniques include refining non-invasive methods for enhanced specificity, dedicated flap assessment systems for NIRS, and exploring novel technologies. The impact of patient preference, clinical setting, and resource availability should be considered when choosing assessment techniques. In essence, navigating the array of flap-assessment tools requires a discerning understanding of their unique attributes. Surgeons must make informed decisions, balancing accuracy, safety, and practicality to ensure successful outcomes in cutaneous reconstructive surgery.

Future perspective

In the realm of reconstructive cutaneous surgery, the future promises an exciting evolution in assessment techniques, with a notable emphasis on the integration of artificial intelligence (AI) and the fusion of current and emerging technologies. As we venture into this era, the convergence of rPPG (remote photoplethysmography) technology, deep learning algorithms, and the principles of ”deep medicine” holds substantial potential for transforming the landscape of flap assessment. Further, these techniques hold great potential to steep the learning curve of young surgeons with bio-feedback techniques to consequently and therefore, improve patient care.

References

1. Simman, R., Wound closure and the reconstructive ladder in plastic surgery. J Am Col Certif Wound Spec, 2009. 1 (1): p. 6-11.
2. Veldhuizen, I.J., et al., Nasal skin reconstruction: Time to rethink the reconstructive ladder? J Plast Reconstr Aesthet Surg, 2022.75 (3): p. 1239-1245.
3. Dragu A, J.J., Bach AD, Horch RE, Prinzipien der Lappenplastiken: Eine Übersicht , in CHAZ . 2008. p. 59-66.
4. Schraven, S.P., et al., Continuous intraoperative perfusion monitoring of free microvascular anastomosed fasciocutaneous flaps using remote photoplethysmography. Sci Rep, 2023. 13 (1): p. 1532.
5. Rozen, W.M., et al., Preoperative imaging for DIEA perforator flaps: a comparative study of computed tomographic angiography and Doppler ultrasound. Plast Reconstr Surg, 2008. 121 (1): p. 9-16.
6. Scott, J.R., et al., Computed tomographic angiography in planning abdomen-based microsurgical breast reconstruction: a comparison with color duplex ultrasound. Plast Reconstr Surg, 2010.125 (2): p. 446-453.
7. Bootz, F., Postoperative Überwachung (Monitoring) , inExpertise Lappenplastiken und Transplantate im Kopf-Hals-Bereich , S.H. Lang, F. Bootz, and S. Remmert, Editors. 2018, Georg Thieme Verlag KG.
8. Whitaker, I.S., et al., Postoperative monitoring of free flaps in autologous breast reconstruction: a multicenter comparison of 398 flaps using clinical monitoring, microdialysis, and the implantable Doppler probe. J Reconstr Microsurg, 2010. 26 (6): p. 409-16.
9. Nagel, S.S., et al., Postoperatives Monitoring freier Muskellappenplastiken mittels perforatorbasierten adipokutanen Monitorinseln: Ökonomie, Versorgungsqualität und Ästhetik.Hand-/Mikro-/Plastische Chirurgie, 2022. 54 (02): p. 139-148.
10. Spiegel, J.H. and J.K. Polat, Microvascular flap reconstruction by otolaryngologists: prevalence, postoperative care, and monitoring techniques. Laryngoscope, 2007. 117 (3): p. 485-90.
11. Gross, J.E. and J.D. Friedman, Soft tissue reconstruction. Monitoring. Orthop Clin North Am, 1993. 24 (3): p. 531-6.
12. Rettinger, G., Chirurgische Anatomie der Haut , inHNO-Operationslehre , G. Rettinger, et al., Editors. 2017, Georg Thieme Verlag KG.
13. I Anatomy, Principles of Facial Surgery, and Coverage of Defects , in Reconstructive Facial Plastic Surgery: A Problem-Solving Manual , H. Weerda, Editor. 2014, Georg Thieme Verlag KG.
14. Lüllmann-Rauch, R., Taschenlehrbuch Histologie . Vol. 3. Auflage. 2009, Stuttgart, New York: Thieme.
15. Al-Qattan, M.M., One Pedicled Superficial Temporal Artery Hair-bearing Flap to Reconstruct Three Different Anatomical Areas of the Burnt Face: A Personal Technique. Ann Plast Surg, 2021. 86 (2): p. 159-161.
16. Tayfur, V., et al., Supraclavicular artery flap. J Craniofac Surg, 2010. 21 (6): p. 1938-40.
17. Kim, H.S., et al., Reconstruction of a Full-thickness Lateral Alar Defect Using a Superiorly Based Folded Nasolabial Flap Without a Cartilage Graft: A Single-stage Operation. J Craniofac Surg, 2021.32 (2): p. e162-e165.
18. Kunert, P., [A simple classification system for all skin flaps]. Handchir Mikrochir Plast Chir, 1995. 27 (3): p. 124-31.
19. Rettinger, G. and O. Guntinas-Lichius, [Not Available].Laryngorhinootologie, 2019. 98 (10): p. 745-750.
20. Berkane, Y., et al., The Autonomization Principle in Vascularized Flaps: An Alternative Strategy for Composite Tissue Scaffold In Vivo Revascularization. Bioengineering (Basel), 2023.10 (12).
21. Ludolph, I., et al., Indocyanine green angiography and the old question of vascular autonomy - Long term changes of microcirculation in microsurgically transplanted free flaps. Clin Hemorheol Microcirc, 2019. 72 (4): p. 421-430.
22. Mehta, A.G., J.J. , axial flaps , in StatPearls . 2024.
23. Pavletic, M.M., Canine axial pattern flaps, using the omocervical, thoracodorsal, and deep circumflex iliac direct cutaneous arteries. Am J Vet Res, 1981. 42 (3): p. 391-406.
24. Lim, J., J. Oh, and S. Eun, Flap reconstruction of soft tissue defect after resecting a huge hemangioma of the nose. Arch Craniofac Surg, 2020. 21 (1): p. 69-72.
25. Lamberty, B.G., The supra-clavicular axial patterned flap. Br J Plast Surg, 1979. 32 (3): p. 207-12.
26. Pallua, N. and B.S. Kim, Pre-expanded Supraclavicular Artery Perforator Flap. Clin Plast Surg, 2017. 44 (1): p. 49-63.
27. Yassin, A.M., et al., Uses of Smartphone Thermal Imaging in Perforator Flaps as a Versatile Intraoperative Tool: The Microsurgeon’s Third Eye. JPRAS Open, 2023. 38 : p. 98-108.
28. Jones, B., Microvascular free tissue transfer. Br Med J (Clin Res Ed), 1984. 288 (6414): p. 345-6.
29. Cheung ME, S.V., Firstenberg MS. , Duplex Ultrasound. . 2022, StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing;.
30. Bigdeli, A.K., A. Momeni, and U. Kneser, Erhöhung der Sicherheit in der mikrochirurgischen Brustrekonstruktion – Technik und Technologie. Hand-/Mikro-/Plastische Chirurgie, 2022. 54 (04): p. 314-325.
31. Malvern, P. Near-infrared (NIR) spectroscopy . 2024; Available from: https://www.malvernpanalytical.com/en/products/technology/spectroscopy/near-infrared-spectroscopy.
32. Barstow, T.J., Understanding near infrared spectroscopy and its application to skeletal muscle research. Journal of Applied Physiology, 2019. 126 (5): p. 1360-1376.
33. Bian, H.Z., C.H. Pek, and J. Hwee, Current evidence on the use of near-infrared spectroscopy for postoperative free flap monitoring: A systematic review. Chinese Journal of Plastic and Reconstructive Surgery, 2022. 4 (4): p. 194-202.
34. Kumbasar, D.E., et al., Monitoring Breast Reconstruction Flaps Using Near-Infrared Spectroscopy Tissue Oximetry. Plast Surg Nurs, 2021. 41 (2): p. 108-111.
35. Lindelauf, A., et al., Near-Infrared Spectroscopy (NIRS) versus Hyperspectral Imaging (HSI) to Detect Flap Failure in Reconstructive Surgery: A Systematic Review. Life (Basel), 2022.12 (1).
36. Repez, A., D. Oroszy, and Z.M. Arnez, Continuous postoperative monitoring of cutaneous free flaps using near infrared spectroscopy. J Plast Reconstr Aesthet Surg, 2008. 61 (1): p. 71-7.
37. Ghidini, F., et al., Transcutaneous near-infrared spectroscopy (NIRS) for monitoring kidney and liver allograft perfusion. Int J Clin Pract, 2021. 75 (5): p. e14034.
38. Wisotzky, E., HSI in der diagnostischen und therapeutischen Medizin . 2019: online.
39. Thiem, D.G.E., et al., Hyperspectral analysis for perioperative perfusion monitoring-a clinical feasibility study on free and pedicled flaps. Clin Oral Investig, 2021. 25 (3): p. 933-945.
40. Schulz, T., et al., Diagnostical accuracy of hyperspectral imaging after free flap surgery. J Plast Surg Hand Surg, 2023.58 : p. 48-55.
41. Nischwitz, S.P., et al., Thermal, Hyperspectral, and Laser Doppler Imaging: Non-Invasive Tools for Detection of The Deep Inferior Epigastric Artery Perforators-A Prospective Comparison Study. J Pers Med, 2021. 11 (10).
42. Tattersall, G.J., Infrared thermography: A non-invasive window into thermal physiology. Comp Biochem Physiol A Mol Integr Physiol, 2016. 202 : p. 78-98.
43. Luximon, A., et al., Theory and applications of InfraRed and thermal image analysis in ergonomics research. Frontiers in Computer Science, 2022. 4 .
44. Hallock, G.G., The use of smartphone thermography to more safely unmask and preserve circulation to keystone advancement flaps in the lower extremity. Injury, 2020. 51 Suppl 4 : p. S121-s125.
45. Nischwitz, S.P., H. Luze, and L.P. Kamolz, Thermal imaging via FLIR One - A promising tool in clinical burn care and research. Burns, 2020. 46 (4): p. 988-989.
46. Xue, E.Y., et al., Use of FLIR ONE Smartphone Thermography in Burn Wound Assessment. Ann Plast Surg, 2018. 80 (4 Suppl 4): p. S236-s238.
47. Meyer, A., et al., Thermal imaging for microvascular free tissue transfer monitoring: Feasibility study using a low cost, commercially available mobile phone imaging system. Head Neck, 2020.42 (10): p. 2941-2947.
48. Luze, H., et al., Assessment of Mastectomy Skin Flaps for Immediate Reconstruction with Implants via Thermal Imaging-A Suitable, Personalized Approach? J Pers Med, 2022. 12 (5).
49. Rabbani, M.J., A.Z. Bhatti, and A. Shahzad, Flap Monitoring using Thermal Imaging Camera: A Contactless Method. J Coll Physicians Surg Pak, 2021. 30 (6): p. 703-706.
50. Obinah, M.P.B., M. Nielsen, and L.R. Hölmich, High-end versus Low-end Thermal Imaging for Detection of Arterial Perforators. Plast Reconstr Surg Glob Open, 2020. 8 (10): p. e3175.
51. Weum, S., A. Lott, and L. de Weerd, Detection of Perforators Using Smartphone Thermal Imaging. Plast Reconstr Surg, 2016.138 (5): p. 938e-940e.
52. Xu, W.H., et al., [Application of infrared thermal imaging technology in the design of free anterolateral thigh perforator flap transplantation]. Zhongguo Gu Shang, 2019. 32 (11): p. 1053-1057.
53. Chen, R., et al., Value of a smartphone-compatible thermal imaging camera in the detection of peroneal artery perforators: Comparative study with computed tomography angiography. Head Neck, 2019. 41 (5): p. 1450-1456.
54. Cevik, J., et al., A History of Innovation: Tracing the Evolution of Imaging Modalities for the Preoperative Planning of Microsurgical Breast Reconstruction. J Clin Med, 2023. 12 (16).
55. Hudson, T., et al., The Utility of Smartphone-Based Thermal Imaging in the Management and Monitoring of Microvascular Flap Procedures: A Systematic Review and Meta-Analysis. Ann Plast Surg, 2023. 90 (6S Suppl 4): p. S420-s425.
56. Just, M., et al., Monitoring of microvascular free flaps following oropharyngeal reconstruction using infrared thermography: first clinical experiences. Eur Arch Otorhinolaryngol, 2016.273 (9): p. 2659-67.
57. Cruz-Segura, A., et al., Early Detection of Vascular Obstruction in Microvascular Flaps Using a Thermographic Camera. J Reconstr Microsurg, 2019. 35 (7): p. 541-548.
58. Mironenko, Y., et al., Remote Photoplethysmography: Rarely Considered Factors. 2020 IEEE/CVF Conference on Computer Vision and Pattern Recognition Workshops (CVPRW), 2020: p. 1197-1206.
59. Wukitsch, M.W., et al., Pulse oximetry: analysis of theory, technology, and practice. J Clin Monit, 1988. 4 (4): p. 290-301.
60. Wang, W., S. Stuijk, and G. de Haan, Unsupervised Subject Detection via Remote PPG. IEEE Trans Biomed Eng, 2015. 62 (11): p. 2629-37.
61. Wang, W., S. Stuijk, and G. de Haan, A Novel Algorithm for Remote Photoplethysmography: Spatial Subspace Rotation. IEEE Trans Biomed Eng, 2016. 63 (9): p. 1974-1984.
62. Hammer, A., et al., Camera-based assessment of cutaneous perfusion strength in a clinical setting. Physiol Meas, 2022.43 (2).
63. Karthik, S., J. Joseph, and M. Sivaprakasam, A study on the use of PPG in quantifying circulatory disruptions. Annu Int Conf IEEE Eng Med Biol Soc, 2014. 2014 : p. 1739-42.
64. Chubb, D., W.M. Rozen, and M.W. Ashton, Early survival of a compromised fasciocutaneous flap without pedicle revision: monitoring with photoplethysmography. Microsurgery, 2010. 30 (6): p. 462-5.
65. Dietrich, C.F., et al., How to perform Contrast-Enhanced Ultrasound (CEUS). Ultrasound Int Open, 2018. 4 (1): p. E2-e15.
66. Baliyan, V., et al., Vascular computed tomography angiography technique and indications. Cardiovasc Diagn Ther, 2019.9 (Suppl 1): p. S14-s27.
67. Goncalves, L.N., et al., Perfusion Parameters in Near-Infrared Fluorescence Imaging with Indocyanine Green: A Systematic Review of the Literature. Life (Basel), 2021. 11 (5).
68. Smit, J.M., et al., Intraoperative evaluation of perfusion in free flap surgery: A systematic review and meta-analysis. Microsurgery, 2018. 38 (7): p. 804-818.
69. Lee, B.T., et al., Intraoperative near-infrared fluorescence imaging in perforator flap reconstruction: current research and early clinical experience. J Reconstr Microsurg, 2010. 26 (1): p. 59-65.
70. Tange, F.P., et al., Near-infrared fluorescence angiography with indocyanine green for perfusion assessment of DIEP and msTRAM flaps: A Dutch multicenter randomized controlled trial. Contemp Clin Trials Commun, 2023. 33 : p. 101128.
71. Manning-Geist, B.L., et al., Assessment of wound perfusion with near-infrared angiography: A prospective feasibility study.Gynecol Oncol Rep, 2022. 40 : p. 100940.
72. Matsui, A., et al., Predictive capability of near-infrared fluorescence angiography in submental perforator flap survival. Plast Reconstr Surg, 2010. 126 (5): p. 1518-1527.
73. Lohman, R.F., et al., An Analysis of Current Techniques Used for Intraoperative Flap Evaluation. Ann Plast Surg, 2015.75 (6): p. 679-85.
74. Swartz, W.M., et al., Direct monitoring of microvascular anastomoses with the 20-MHz ultrasonic Doppler probe: an experimental and clinical study. Plast Reconstr Surg, 1988. 81 (2): p. 149-61.
75. Guillemaud, J.P., et al., The Implantable Cook-Swartz Doppler Probe for Postoperative Monitoring in Head and Neck Free Flap Reconstruction. Archives of Otolaryngology–Head & Neck Surgery, 2008.134 (7): p. 729-734.
76. Oliver, D.W., et al., The Cook-Swartz venous Doppler probe for the post-operative monitoring of free tissue transfers in the United Kingdom: a preliminary report. Br J Plast Surg, 2005. 58 (3): p. 366-70.
77. Paprottka, F.J., et al., Cook-Swartz Doppler Probe Surveillance for Free Flaps-Defining Pros and Cons. Surg J (N Y), 2020.6 (1): p. e42-e46.
78. Frost, M.W., et al., Direct comparison of postoperative monitoring of free flaps with microdialysis, implantable cook-swartz Doppler probe, and clinical monitoring in 20 consecutive patients.Microsurgery, 2015. 35 (4): p. 262-71.
79. Thoenissen, P., et al., Hyperspectral Imaging Allows Evaluation of Free Flaps in Craniomaxillofacial Reconstruction. J Craniofac Surg, 2023. 34 (3): p. e212-e216.