Intraosseous microdialysis for bone free flap monitoring in head and neck reconstructive surgery: A prospective pilot study

Reconstructive flap surgery in head and neck cancer patients: an interdisciplinary view of the challenges encountered by radiation oncologists in postoperative radiotherapy

Background

Major advances have been made in reconstructive surgery in the last decades to reduce morbidity in head and neck cancer. Flaps are now present in 80% of patients with oral cavity cancer to cover anatomic, functional, and cosmetic needs. However, gaps in interdisciplinary innovation transfer from surgery to postoperative radiotherapy (poRT) remain challenging. We aimed to provide an interdisciplinary view of the challenges encountered by radiation oncologists in planning head and neck postoperative radiotherapy.

Methods

A systematic and critical review was conducted to address areas of optimization in surgery and radiology that may be relevant to poRT.

Results

Despite extensive surgical literature on flap techniques and salvage surgery, 13 retrospective series were identified, where flap outcomes were indirectly compared between surgery alone or poRT. These low-evidence studies suggest that radiotherapy accelerates flap atrophy, fibrosis, and osteoradionecrosis and deteriorates functional outcomes. Preliminary evidence suggests that tumor spread occurs at the flap-tissue junction rather than in the flaps. One prospective 15-patient study showed 31.3% vs. 39.2% flap volume reduction without or with poRT. In an international consensus, experts recognized the needs for optimized flap-sparing poRT against flap-related functional deterioration and bone damage. CT, MRI, and PET-CT modalities show potential for the delineation of the junction area between native tissues and flap for flap segmentation and to characterize flap-specific changes quantitatively and correlate them with patterns of relapse or complications.

Conclusion

Flap management in poRT is insufficiently documented, but poRT seems to damage flaps. Current gaps in knowledge underscore the need for prospective flap assessment and interdisciplinary trials investigating flap morbidity minimization by flap-sparing poRT planning.

The Impact of Transfer-Related Ischemia on Free Flap Metabolism and Electrolyte Homeostasis-A New In Vivo Experimental Approach in Pigs

Free flap tissue transfer represents the gold standard for extensive defect reconstruction, although malperfusion due to thrombosis remains the leading risk factor for flap failure. Recent studies indicate an increased immune response and platelet activation in connection with pathologic coagulation. The underlying cellular and molecular mechanisms remain poorly understood, however. The presented study, therefore, aims to investigate if transfer-related ischemia alters intra-flap metabolism and electrolyte concentrations compared to central venous blood after free flap transfer in pigs to establish a novel experimental model. Free transfer of a myocutaneous gracilis flap to the axillary region was conducted in five juvenile male pigs. The flap artery was anastomosed to the axillary artery, and intra-flap venous blood was drained and transfused using a rubber-elastic fixed intravenous catheter. Blood gas analysis was performed to assess the effect of transfer time-induced ischemia on intra-flap electrolyte levels, acid-base balance, and hemoglobin concentrations compared to central venous blood. Time to flap reperfusion was 52 ± 10 min on average, resulting in a continuous pH drop (acidosis) in the flaps' venous blood compared to the central venous system (p = 0.037). Potassium (p = 0.016), sodium (p = 0.003), and chloride (p = 0.007) concentrations were significantly increased, whereas bicarbonate (p = 0.016) and calcium (p = 0.008) significantly decreased within the flap. These observations demonstrate the induction of anaerobic glycolysis and electrolyte displacement resulting in acidosis and hence significant tissue damage already after a short ischemic period, thereby validating the novel animal model for investigating intra-flap metabolism and offering opportunities for exploring various (immuno-) thrombo-hemostatic issues in transplantation surgery.

From bench to bedside - current clinical and translational challenges in fibula free flap reconstruction

Fibula free flaps (FFF) represent a working horse for different reconstructive scenarios in facial surgery. While FFF were initially established for mandible reconstruction, advancements in planning for microsurgical techniques have paved the way toward a broader spectrum of indications, including maxillary defects. Essential factors to improve patient outcomes following FFF include minimal donor site morbidity, adequate bone length, and dual blood supply. Yet, persisting clinical and translational challenges hamper the effectiveness of FFF. In the preoperative phase, virtual surgical planning and artificial intelligence tools carry untapped potential, while the intraoperative role of individualized surgical templates and bioprinted prostheses remains to be summarized. Further, the integration of novel flap monitoring technologies into postoperative patient management has been subject to translational and clinical research efforts. Overall, there is a paucity of studies condensing the body of knowledge on emerging technologies and techniques in FFF surgery. Herein, we aim to review current challenges and solution possibilities in FFF. This line of research may serve as a pocket guide on cutting-edge developments and facilitate future targeted research in FFF.

Diagnostic Accuracy of Microdialysis in Postoperative Flap Monitoring

Postoperative monitoring plays an important role in achieving success in microvascular free tissue transfer. A systematic review was designed to evaluate the clinical outcomes of microdialysis in flap monitoring and a meta-analysis was conducted for diagnostic accuracies. The search terms "microdialysis" and "flap" were used in a PubMed and Scopus search, resulting in 60 and 78 results, respectively. Among 78 titles, 15 articles were excluded. Among 63 abstracts, 43 abstracts were excluded. From 20 full texts, 7 articles were excluded because they did not have sufficient content (ie, the statistical values in question). A systematic review was conducted of the final 13 articles. The overall sensitivity was 97.24% [95% confidence interval (CI)=93.67%-99.10%]. Eleven of the 13 studies showed 100% sensitivity and 2 studies had 2 and 3 false negative results, resulting in sensitivity values of 85.8% and 95.3%. Specificity ranged from 91.89% to 100%, and the overall value was 98.15% (95% CI=96.80%-99.04%). The positive predictive value ranged from 84.62% to 100%, with an overall value of 93.62% (95% CI=89.33%-96.26%). The negative predictive value ranged from 94.44% to 100%, with an overall value of 99.22% (95% CI=98.17%-99.67%). The overall flap success rate (survival rate) was 93.7% (786/839). The lowest flap survival rate was 86.7% and the highest was 100%. Microdialysis provides excellent diagnostic accuracy and enables the early detection of ischemia in postoperative flap monitoring. Although microdialysis is not the most popular choice among surgeons, it should be considered adjacent to conventional clinical monitoring. Cost-effectiveness, availability, and ease of application remain hurdles.

Surgical and demographic predictors of free flap salvage after takeback: A systematic review

BACKGROUND

Microsurgical free tissue transfer (FTT) is a widely employed surgical modality utilized for reconstruction of a broad range of defects, including head and neck, extremity, and breast. Flap survival is reported to be 90%-95%. When FTT fails, salvage procedures aim at establishing reperfusion while limiting ischemia time-with salvage rates between 22% and 67%. There are limited data-driven predictors of successful salvage present in the literature. This systematic review aims to identify predictors of flap salvage.

METHODS

A systematic literature review was conducted per PRISMA guidelines. Articles included in the final analysis were limited to those investigating FTT salvage procedures and included factors impacting outcomes. Cohort and case series (>5 flaps) studies up until March 2021 were included. Chi-square tests and linear regression modeling was completed for analysis.

RESULTS

The patient-specific factors significantly associated with salvage included the absence of hypercoagulability (p < .00001) and no previous salvage attempts (p < .00001). Case-specific factors significantly associated with salvage included trunk/breast flaps (p < .00001), fasciocutaneous/osteocutaneous flaps (p = .006), venous compromise (p < .00001), and shorter time from index procedure to salvage attempt (R = .746). Radiation in the head and neck population was significantly associated with flap salvage failure.

CONCLUSIONS

Given the complexity and challenges surrounding free flap salvage procedures, the goal of this manuscript was to present data helping guide surgical decision-making. Based on our findings, patients without documented hypercoagulability, no previous salvage attempts, fasciocutaneous/osteocutaneous flaps, trunk/breast flaps, and a shorter time interval post-index operation are the best candidates for a salvage attempt.

Continuous Interstitial Glucose Measurement for Flap Venous Occlusion Monitoring in a Diabetic Model

ABSTRACT

Glucose has been used in the monitoring of transplanted flaps. However, few studies have focused on the effect of diabetes on the decrease in flap glucose levels. The purpose of this study was to evaluate the application of continuous interstitial glucose monitoring to detect flap venous occlusion in a diabetic rat model. The flap interstitial glucose level was measured by transcutaneous sensors in the bilateral vertical rectus abdominis myocutaneous flaps of each rat. interstitial glucose values in the bilateral flaps were recorded every 5 minutes after the venous occlusion of 1 flap. Forty-one rats were divided into the control group (n = 13), diabetic group (n = 15, established by the intraperitoneal injection of streptozotocin), and insulin-treated diabetic group (n = 13, systemic glucose well controlled by insulin before surgery). Results indicated that flap interstitial glucose decreased to the lowest level in all flaps with venous occlusion. The time from venous occlusionto the lowest interstitial glucose level was significantlylongerinthe diabetic group than the control group (120.8 ± 5.7 minutes versus 56.5 ± 6.7 min-minutes, P < 0.001), but was similar in the insulin-treated diabetic and control groups (56.5 ± 6.7 minutes versus 56.0 ± 6.6 minutes, P = 0.876). The change in interstitial glucose in both the diabetic and insulin-treated diabetic groups began with a plateau period or a slow decline before decreasing for 49.0 ± 6.4 minutes and 24.4 ± 4.3 min-minutes, respectively. in a diabetic rat model, impaired glucose metabolism prolongs the required monitoring time and dulls the reaction of flap interstitial glucose to venous congestion. Insulin restores the prolonged monitoring time, but not the reaction of flap interstitial glucose. Therefore, care is needed during application of the technique in diabetic patients.

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.

Head and neck free-flap salvage

PURPOSE OF REVIEW

To highlight three clinical arenas in which head and neck free-flap compromise is encountered and acted upon: nonoperative, operative and postoperative realms.

RECENT FINDINGS

Time to identification and intervention is paramount to successful free-flap salvage. Surgical microvascular revision remains chief amongst strategies to revert vascular compromise of a free-flap. Adjuncts, such as thrombolytics and systemic anticoagulation have an important role in the complex work of microvascular free tissue care. Venous congestion of free flaps holds favorable for salvage when compared with arterial insufficiency.

SUMMARY

Vascular compromise of head and neck free flaps is a rare and feared event for microvascular surgeons, with successful transfers rates approaching above 95%. Success in salvage is dependent on prompt identification of tissue compromise and timely, directed interventions to re-establish tissue perfusion.

Complication of osteo reconstruction by utilizing free vascularized fibular bone graft

The success of free vascularized fibular bone graft (FVFBG) has accelerated the osteo reconstruction which results from trauma, resection of a tumor or an infectious bone segment, or correction of congenital deformity. But the complication behind should not be overlooked. The failure could necessitate a second surgery, which prolong the rehabilitation period and produce further health cost. Worst, the patients may suffer a permanent impaired ankle function, or a sustained morpho-functional loss on reconstructive area which are hard to save. To provide an overview of the complication related to reconstruction by FVFBG, a narrative review is conducted to identify the complications including their types and rates, the contributing factors, the approaches to measure and the techniques to avoid. Methodologically, by quick research on Pubmed and abstract reading of reviews, we characterize five reconstructive areas where FVFBG were most frequently applied: extremities, mandible, spine, osteonecrosis of femoral head, and penile. Following, the complications on different reconstructive areas are retrieved, studied and presented in five (or more specifically, six) separate sections. By the way, meaningful difference between FVFBG and other bone flap was presented in a few words if necessary. Donor-site morbidities were studied and summarized as a whole. In these literatures, the evidences documented on limb and mandibular reconstruction have the fullest detail, followed by the spine and lastly the penile. In conclusion, FVFBG, though a mature technique, needs further deep and comprehensive study and maybe device-based assistance to achieve better reconstructive effect and minimize donor-site damage.

Intraosseous microdialysis for bone free flap monitoring in head and neck reconstructive surgery: A prospective pilot study

BACKGROUND

Although some researchers have positioned microdialysis catheters in the soft tissue surrounding bone, the results did not accurately reflect bone metabolism. The present study's objective was to establish the feasibility of microdialysis with a catheter positioned directly in bone.

METHODS

Thirty-four patients (19 males, 15 females; median age: 59) were included in a prospective, nonrandomized clinical trial in the Department of Maxillofacial Surgery at Amiens-Picardie University Hospital (Amiens, France). Fibula or iliac crest free flaps were used in reconstructive head and neck surgery (for cancer, osteoradionecrosis, trauma, or ameloblastoma) and monitored with microdialysis catheters positioned in a hole drilled into the bone. Glucose, lactate, pyruvate, and glycerol concentrations were analyzed for 5 days.

RESULTS

All catheters were positioned successfully, and thrombosis did not occur during the monitoring. In two patients, an increase in the lactate concentration and a glucose level close to 0 were associated with signs of flap necrosis, with removal on Days 9 and 50. In viable flaps, the mean glucose level was 2.02 mmol/L, the mean lactate level was 8.36 mmol/L, and the mean lactate/pyruvate ratio was 53. Forty percent of the glucose values were below 1 mmol/L, and 50% of the lactate/pyruvate ratio values were above 50-suggesting a specific metabolic pattern because these values would be considered as alert values in soft tissue.

CONCLUSION

Monitoring bone free flaps with intraosseous microdialysis is feasible. This technique specifically assesses bone viability, and further studies are now necessary to define the alert values in bone.