Quantifying the Limitations of Clinical and Technology-based Flap Monitoring Strategies using a Systematic Thematic Analysis

The future of free flap monitoring by laser continuous doppler flowmetry: A prospective assessment in consecutive 71 patients

Objective

This study evaluated the effectiveness of laser Doppler flowmetry (LDF) in detecting perfusion disturbances during microvascular free tissue transfer.

Methods

Conducted at a single centre from December 2020 to September 2022, this prospective study involved 71 patients mainly undergoing head and neck free flap reconstructions, using the Pocket LDF™ for continuous perfusion monitoring.

Results

Out of the 71 cases, data from 69 cases were analysed after excluding those with significant noise or sensor detachment. Blood flow disturbances were observed in 9 cases (13.0 %), with 5 of these cases with a history of surgery or radiation in the same area. There were 5 cases of ischaemia, 4 of which occurred during monitoring. There were 4 cases of venous congestion, with 1 occurring during monitoring. Re-operation was necessary in 8 cases (11.6 %), involving flap replacements, vascular re-anastomoses and hematoma evacuation. Complete flap necrosis occurred in 5 cases (7.2 %) and partial necrosis occurred in 3 cases (4.3 %). The LDF device demonstrated the ability to identify perfusion issues hours before the clinical symptoms manifested, suggesting its potential for early intervention. However, challenges included maintaining continuous monitoring immediately post-surgery and during patient transfers.

Conclusion

LDF is a valuable, non-invasive tool for early detection of perfusion disturbances in free flap procedures. It provides continuous, real-time feedback on microcirculation, facilitating timely interventions. Despite its benefits, enhancements in sensor adhesion and wireless technology are needed to improve monitoring reliability. Further studies are recommended to refine LDF usage and validate its efficacy in various clinical settings.

Application of pedicled supraclavicular flaps in hypopharyngectomy with preservation of laryngeal function

OBJECTIVE

To evaluate the efficacy of pedicled supraclavicular flaps in hypopharyngectomy reconstruction, with a focus on preserving laryngeal function.

METHODS

From August 2019 to June 2022, 14 patients with primary hypopharyngeal carcinoma who met the inclusion and exclusion criteria and underwent the repair of hypopharyngeal defects using pedicled supraclavicular flaps were included retrospectively. Relevant clinical evaluation indicators include patient characteristics, defect sizes, flap sizes, flap harvesting time, postoperative hospital stay, postoperative complications, recurrence, and survival outcomes.

RESULTS

Among the 14 patients, pyriform sinus carcinoma (n = 10) and posterior hypopharyngeal wall carcinoma (n = 4) were present, with stages T2 (n = 7), T3 (n = 4), T4 (n = 3), N0 (n = 3), N1 (n = 1), and N2 (n = 10). The average defect size was 7.0 (4.0-12.6) cm in the longitudinal diameter and 4.1 (2.8-7.5) cm in the transverse diameter. The mean flap size was 8.4 (5.0-14.0) cm in length and 6.5 (4.0-9.0) cm in width. The mean time for flap harvesting was 37.0 (29.0-51.0) min. The mean postoperative hospital stay was 24.0 (12.0-48.0) days. The mean follow-up period was 20.3 (4.0-47.0) months, and one of the 14 patients was lost during follow-up. Short-term postoperative complications included partial flap necrosis (n = 1), subcutaneous hematoma at the donor site (n = 1), and pharyngeal fistula (n = 4). Long-term complications encompassed pharyngoesophageal anastomotic stenosis (n = 2) and shoulder elevation dysfunction (n = 2). Tumor recurrence occurred in 3 patients. 1 patient succumbed to massive hemorrhage resulting from neck infection due to pharyngeal fistula during chemoradiotherapy. 2 patients succumbed to tumor-related causes. The gastric tube was removed in 13 patients, and the tracheal tube was extracted in 10 patients.

CONCLUSION

The supraclavicular flap offers a promising alternative for reconstruction during hypopharyngectomy with preservation of laryngeal function. It can be utilized to reshape the morphology of the pyriform fossa, aryepiglottic wall, and laryngeal cavity, thereby restoring the functionality of the laryngopharynx.

Imaging Photoplethysmography (iPPG) in Head and Neck Reconstructive Surgery: A Novel Technique for Noninvasive Flap Perfusion Monitoring

BACKGROUND

Evaluate imaging photoplethysmography (iPPG) as a novel noninvasive technique to assess flap perfusion in head and neck free flap reconstructive (FFR) surgeries.

METHODS

Intraoperative iPPG was performed in 17 patients undergoing FFR surgery. Imaging consisted of a 30-s video from which perfusion maps were extracted, providing detailed information about blood flow and pulsatility in the flap microvasculature. During each procedure, iPPG acquisitions were acquired representing distinct perfusion conditions of the flap (fully perfused/ischemic/reperfused). When possible, postoperative measurements were performed to assess flap recovery during the critical time period (3 days) and long-term follow-up (30 days).

RESULTS

Perfusion maps, displaying iPPG amplitude and delay times, correlated strongly (p < 0.001) with the perfusion status of the tissue. One case of postoperative thrombosis, leading to flap failure, was identified with iPPG. After surgical revision in this case, flap perfusion was restored and confirmed by iPPG. Postoperative follow-up imaging allowed for objective visualization of flap recovery short term (3 days) and up to 30 days after the surgical procedure.

CONCLUSIONS

This study shows that iPPG is suitable for objective and noninvasive assessment of flap perfusion in head and neck FFR surgery. In addition, postoperative monitoring shows potential for assessing flap perfusion in patients with increased risk of postoperative complications.

Development of an Automated Free Flap Monitoring System Based on Artificial Intelligence

Importance

Meticulous postoperative flap monitoring is essential for preventing flap failure and achieving optimal results in free flap operations, for which physical examination has remained the criterion standard. Despite the high reliability of physical examination, the requirement of excessive use of clinician time has been considered a main drawback.

Objective

To develop an automated free flap monitoring system using artificial intelligence (AI), minimizing human involvement while maintaining efficiency.

Design, Setting, and Participants

In this prognostic study, the designed system involves a smartphone camera installed in a location with optimal flap visibility to capture photographs at regular intervals. The automated program identifies the flap area, checks for notable abnormalities in its appearance, and notifies medical staff if abnormalities are detected. Implementation requires 2 AI-based models: a segmentation model for automatic flap recognition in photographs and a grading model for evaluating the perfusion status of the identified flap. To develop this system, flap photographs captured for monitoring were collected from patients who underwent free flap-based reconstruction from March 1, 2020, to August 31, 2023. After the 2 models were developed, they were integrated to construct the system, which was applied in a clinical setting in November 2023.

Exposure

Conducting the developed automated AI-based flap monitoring system.

Main Outcomes and Measures

Accuracy of the developed models and feasibility of clinical application of the system.

Results

Photographs were obtained from 305 patients (median age, 62 years [range, 8-86 years]; 178 [58.4%] were male). Based on 2068 photographs, the FS-net program (a customized model) was developed for flap segmentation, demonstrating a mean (SD) Dice similarity coefficient of 0.970 (0.001) with 5-fold cross-validation. For the flap grading system, 11 112 photographs from the 305 patients were used, encompassing 10 115 photographs with normal features and 997 with abnormal features. Tested on 5506 photographs, the DenseNet121 model demonstrated the highest performance with an area under the receiver operating characteristic curve of 0.960 (95% CI, 0.951-0.969). The sensitivity for detecting venous insufficiency was 97.5% and for arterial insufficiency was 92.8%. When applied to 10 patients, the system successfully conducted 143 automated monitoring sessions without significant issues.

Conclusions and Relevance

The findings of this study suggest that a novel automated system may enable efficient flap monitoring with minimal use of clinician time. It may be anticipated to serve as an effective surveillance tool for postoperative free flap monitoring. Further studies are required to verify its reliability.

Continuous Monitoring of Buried Free Bone Flap Microcirculation Using a Near-Infrared Spectroscopy System

SUMMARY

Postoperative evaluation of free flaps remains a challenging task. The current accepted standard for diagnosis of vascular compromise remains clinical observation. In recent years, near-infrared spectroscopy (NIRS) has been widely used as a noninvasive objective monitoring tool for postoperative evaluation of soft-tissue flaps. However, methods for monitoring bone flaps remain inadequate. In this study, NIRS was applied for the first time to monitor free buried bone flaps that were used for mandibular reconstruction. The penetrating property of NIRS was used to measure the tissue oxygenation index (TOI) of deep tissues, which reflected the microcirculatory status of the tissues. Changes in TOI values were monitored continuously in 59 cases of free bone flaps up to 72 hours after surgery. Five cases of vascular compromise were noted by clinical observation. Two fibula flaps were total failures, one of which showed a sharp decrease in TOI value to 45% in a short period of time; the other showed a continual gradual decrease to 55%. The observed sudden (<50%) and continuous (>10%) decreases in TOI values suggest that more attention should be paid to revision surgical procedures. The authors conclude that NIRS holds promise as an objective and valid method for clinical evaluation of buried bone flaps.

Superb Microvascular Imaging at Evaluation of Nonvisible Buried De-epitelized Flap Vascularization in Breast Reconstruction

OBJECTIVE

Superb microvascular imaging is a Doppler technique that increases the visibility of small vessels and gives quantitative information about tissue blood supply by measuring the vascular index. In this study, it is aimed to evaluate the long-term and postradiotherapy changes in blood flow of buried de-epitelized flaps in breast reconstruction by using the quantitative values obtained through superb microvascular imaging.

MATERIALS AND METHODS

Retrospective review of the 14 patients who underwent nipple-sparing breastconserving surgery and immediately breast reconstruction with a de-epitelized extended latissimus dorsi flap was done. In order to demonstrate the effect of radiotherapy on flaps microvascular circulation, patients were evaluated using superb microvascular imaging postoperative first week, first month, and postradiotherapy first week and sixth month. The normal distribution of the data was evaluated with the Shapiro-Wilk test. Paired samples t-test was used for comparisons.

RESULTS

According to the paired samples t-tests, postoperative first week mean vascular index was higher than postoperative first month and postradiotherapy first week (P < .05). Besides, postradiotherapy first week mean vascular index was higher than postoperative first month and also than postradiotherapy sixth month (P < .05).

CONCLUSION

Radiotherapy can affect the results of breast reconstruction by endothelial and fibrotic injury. In this study, the changes in the microvascular circulation of the latissimus dorsi flap were discussed and found to increase at postoperative and postradiotherapy early period related to inflammation and not decreased significantly at long-term follow-up after radiotherapy.

Diagnostical accuracy of hyperspectral imaging after free flap surgery

Microsurgical free-tissue transfer has been a safe option for tissue reconstruction. This study aimed to analyze the diagnostic accuracy of hyperspectral imaging (HSI) after free-tissue transfer surgery. From January 2017 to October 2019, 42 consecutive free-flap surgeries were performed, and their outcomes were analyzed via HSI. Clinical examination of free-flap perfusion was initially performed. Clinical examination findings were subsequently compared with those of HSI. Potential venous congestion with subsequent necrosis was defined as a tissue hemoglobin index of ≥53%. Student's t-test was used to compare the results of the analysis. The evaluation of sensitivity and specificity for flap failure detection was time dependent using the Fisher's exact test. A p-value of ≤0.05 was considered statistically significant. Microsurgical tissue transfer success rate was 84%. Seven patients presented with venous congestion that caused total flap necrosis. Overall, 124 assessments were made. HSI accurately identified 12 out of 19 pathological images: four as false positive and seven as false negative. The sensitivity and specificity of HSI were 57 and 94%, respectively, compared to those of clinical examination that were 28 and 100%, respectively, within 24 h following tissue transfer. The sensitivity and specificity of HSI were 63 and 96%, respectively, compared to those of clinical examination that were 63 and 100%, respectively, within the first 72 h. A tissue hemoglobin index of ≥53% could predict venous congestion after free-flap surgery. HSI demonstrated higher sensitivity than clinical examination within the first 24 h; however, it was not superior compared to clinical findings within 72 h.

Role of Lactate Measurement in Flap Monitoring: An Useful Adjunct

Background  Detection of vascular compromise in flap is often a challenging task for reconstructive surgeons. A timely salvage procedure depends on objectivity and reliability of postoperative flap monitoring. This study determined if flap capillary lactate helps in prediction of flap viability in first 48 postoperative hours of surgery. Methods  We conducted this study on all flaps with accessible skin paddle where capillary lactate values were assessed along with clinical observation to check viability of flap at 0, 1, 6, 12, 24 and 48 hours of surgery. The data was statistically analyzed for significance and area under the receiver operating characteristic curve was used for calculating cutoff value for lactate. Results  Out of a total of 30 patients included in this study, 25 were males and the mean age was 45.03 years. Fifteen patients underwent free flap and rest pedicled. Highly significant association of role of clinical observation in the outcome of flap was found. The average of lactate values for survived and distally ischemic flap was 5.32 ± 1.91 and 8.38 ± 1.81, respectively, which was highly significant. The cutoff value of lactate below which all flaps survived was found to be 6.09 mmol/L. Conclusion  Flap capillary lactate measurement is an easy, quick, cost-effective, and objective tool for checking viability of flaps.

Free flaps monitoring by Laser-Doppler Flowmetry in head and neck surgery

Objective

Early recognition of free flap vascular impairment is essential for flap salvage attempts. Several methods for surveillance of post-operative flaps are available. Among these, we have extensively used Laser-Doppler Perfusion Flowmetry (LDF) monitoring. We report our experience on this topic and illustrate the advantages and weak points.

Methods

Over seven years, 110 consecutive free flaps for head and neck reconstruction were monitored using the Periflux System 5000^® (Perimed AB, Järfälla, Sweden). In addition to maximum and minimum peaks, a pattern called vasomotion can be detected. Monitoring time lasted from 3 to 7 days, 24/24 h.

Results

Six of 110 (5.5%) cases of vascular problems were detected and clinically confirmed. In 5 cases, venous thrombosis was present: 4 patients were successfully treated. In 1 case, both arterial and venous thrombosis occurred. Flowmetry data always showed a more or less sudden disappearance of vasomotion.

Conclusions

LDF is a highly sensible, specific and reliable method. It is easy to use and interpret at low cost. Remote monitoring could also be developed.

Comparison of Hyperspectral Imaging and Microvascular Doppler for Perfusion Monitoring of Free Flaps in an In Vivo Rodent Model

To reduce microvascular free flap failure (MFF), monitoring is crucial for the early detection of malperfusion and allows timely salvage. Therefore, the aim of this study was to evaluate hyperspectral imaging (HSI) in comparison to micro-Doppler sonography (MDS) to monitor MFF perfusion in an in vivo rodent model. Bilateral groin flaps were raised on 20 Sprague−Dawley rats. The femoral artery was transected on the trial side and re-anastomosed. Flaps and anastomoses were assessed before, during, and after the period of ischemia every ten minutes for overall 60 min using HSI and MDS. The contralateral sides’ flaps served as controls. Tissue-oxygenation saturation (StO2), near-infrared perfusion index (NPI), hemoglobin (THI), and water distribution (TWI) were assessed by HSI, while blood flow was assessed by MDS. HSI correlates with the MDS signal in the case of sufficient and completely interrupted perfusion. HSI was able to validly and reproducibly detect tissue perfusion status using StO2 and NPI. After 40 min, flap perfusion decreased due to the general aggravation of hemodynamic circulatory situation, which resulted in a significant drop of StO2 (p < 0.005) and NPI (p < 0.005), whereas the Doppler signal remained unchanged. In accordance, HSI might be suitable to detect MFF general complications in an early stage and further decrease MFF failure rates, whereas MDS may only be used for direct complications at the anastomose site.

Fingerstall-type Tissue Oximetry Reduced Anxiety of Nurses in Postoperative Nursing Monitoring of Free Flaps

Postoperative free flap monitoring is essential for immediately detecting obstruction of anastomosed vessels with successive recovery surgery for salvaging flaps. We performed postoperative nursing monitoring using handheld Doppler sonography, but nurses reported feeling anxious with this approach and demanded a clear-cut evaluation method. Therefore, we implemented monitoring with the fingerstall-type tissue oximeter Toccare, a noninvasive device that enables easy flap checking by simply touching the flap with a probe.

New Approach to the Old Challenge of Free Flap Monitoring-Hyperspectral Imaging Outperforms Clinical Assessment by Earlier Detection of Perfusion Failure

In reconstructive surgery, free flap failure, especially in complex osteocutaneous reconstructions, represents a significant clinical burden. Therefore, the aim of the presented study was to assess hyperspectral imaging (HSI) for monitoring of free flaps compared to clinical monitoring. In a prospective, non-randomized clinical study, patients with free flap reconstruction of the oro-maxillofacial-complex were included. Monitoring was assessed clinically and by using hyperspectral imaging (TIVITA™ Tissue-System, DiaspectiveVision GmbH, Pepelow, Germany) to determine tissue-oxygen-saturation [StO₂], near-infrared-perfusion-index [NPI], distribution of haemoglobin [THI] and water [TWI], and variance to an adjacent reference area (Δreference). A total of 54 primary and 11 secondary reconstructions were performed including fasciocutaneous and osteocutaneous flaps. Re-exploration was performed in 19 cases. A total of seven complete flap failures occurred, resulting in a 63% salvage rate. Mean time from flap inset to decision making for re-exploration based on clinical assessment was 23.1 ± 21.9 vs. 18.2 ± 19.4 h by the appearance of hyperspectral criteria indicating impaired perfusion (StO₂ ≤ 32% OR StO₂Δreference > −38% OR NPI ≤ 32.9 OR NPIΔreference ≥ −13.4%) resulting in a difference of 4.8 ± 5 h (p < 0.001). HSI seems able to detect perfusion compromise significantly earlier than clinical monitoring. These findings provide an interpretation aid for clinicians to simplify postoperative flap monitoring.