Assessment of the Electrolyte Heterogeneity of Tissues in Mandibular Bone-Infiltrating Head and Neck Cancer Using Laser-Induced Breakdown Spectroscopy.

Laser-induced breakdown spectroscopy (LIBS) was recently introduced as a rapid bone analysis technique in bone-infiltrating head and neck cancers. Research efforts on laser surgery systems with controlled tissue feedback are currently limited to animal specimens and the use of nontumorous tissues. Accordingly, this study aimed to characterize the electrolyte composition of tissues in human mandibular bone-infiltrating head and neck cancer. Mandible cross-sections from 12 patients with bone-invasive head and neck cancers were natively investigated with LIBS. Representative LIBS spectra (n = 3049) of the inferior alveolar nerve, fibrosis, tumor stroma, and cell-rich tumor areas were acquired and histologically validated. Tissue-specific differences in the LIBS spectra were determined by receiver operating characteristics analysis and visualized by principal component analysis. The electrolyte emission values of calcium (Ca) and potassium (K) significantly (p < 0.0001) differed in fibrosis, nerve tissue, tumor stroma, and cell-rich tumor areas. Based on the intracellular detection of Ca and K, LIBS ensures the discrimination between the inferior alveolar nerve and cell-rich tumor tissue with a sensitivity of ≥95.2% and a specificity of ≥87.2%. The heterogeneity of electrolyte emission values within tumorous and nontumorous tissue areas enables LIBS-based tissue recognition in mandibular bone-infiltrating head and neck cancer.

Optical Three-Dimensional Imaging for Objective Evaluation of the Donor Site after Anterolateral Thigh Flap Surgery.

Background: The high volume of the fasciomyocutaneous anterolateral thigh flaps (ALT) is suitable for the reconstruction of pronounced soft tissue defects. At the same time, harvesting ALT results in a drastic change in thigh shape. Here, we present an optical three-dimensional imaging method for thigh comparison, which can be an objective and reproducible method for evaluating donor sites after ALT harvesting. Methods: In total, 128 thighs were scanned with an optical three-dimensional scanner, Vectra XT ®. Sixty-eight non-operated right and left thighs were compared and served as a control. Sixty thighs were scanned in the ALT group. The average surface area deviations, thigh volume, thigh circumference, and flap ratio to thigh circumference were calculated. The results were correlated with Δthigh circumference and Δvolume of the unoperated thighs of the control group. Results: No significant difference between the thigh volumes of the right and left thighs was found in the control group. Removal of an ALT flap showed a significant (p < 0.007) volume reduction compared to unoperated thighs (2.7 ± 0.8 L and 3.3 ± 0.9 L, respectively). Flap area correlated strongly with the Δthigh circumference (r = 0.66, p < 0.001) and Δvolume (r = 0.68, p < 0.001). Strong correlations were observed between flap ratio and thigh circumference with Δhigh circumference (r = 0.57, p < 0.001) and Δvolume (r = 0.46, p < 0.05). Conclusions: Optical three-dimensional imaging provides an objective and reproducible tool for detecting changes in thigh morphology volume differences after ALT harvesting.

Influence of microvascular mandibular bony reconstruction on the posterior airway space: A retrospective cohort study.

INTRODUCTION: The posterior airway space (PAS) is a common site of passive obstructions with high morbidity. Surgical changes to the craniomandibular system may affect the PAS. Data regarding the effects of mandibular reconstruction using vascularized bone flaps on PAS are insufficient. This retrospective cohort study aimed to investigate changes in PAS after mandibular reconstruction. MATERIALS AND METHODS: Pre- and post-reconstructive computed tomography scans of 40 patients undergoing segmental mandibulectomy and mandibular reconstruction with deep circumflex iliac artery or fibula flaps were analyzed. Absolute differences in PAS geometry and relative trends of PAS volume changes were compared within the study population and between subgroups formed according to the extent of resection, timing and type of reconstruction, and presence of pre-reconstructive radiotherapy. RESULTS: Irradiated patients were characterized by an increase in PAS volume after reconstruction. Absolute differences in total PAS volume after reconstruction were significantly different (p = 0.024) compared to non-irradiated patients. Reconstruction of central mandible segments resulted in decrease of the cross-sectional PAS areas. Absolute differences in middle cross-sectional PAS area after reconstruction were significantly different (p = 0.039) compared to non-central reconstructions. Patients who received radiotherapy were less likely to show a total PAS volume reduction after reconstruction (OR: 0.147; p = 0.007), with values adjusted for gender, age, body mass index, timing and type of reconstruction, and transplant length. CONCLUSIONS: Mandibular reconstruction causes changes in PAS geometry. Specifically, reconstructions of central mandibular segments can lead to a reduction in the cross-sectional areas of PAS, and mandibular reconstructions in irradiated sites may cause an increase in PAS volume.

Predictive factors and repetition numbers for intraoperative additional resection of initially involved soft tissue resection margins in oral squamous cell carcinoma: a retrospective study.

BACKGROUND: Intraoperative additional resection (IAR) of initially microscopically involved soft tissue resection margins negatively impacts tumor recurrence in oral squamous cell carcinoma (OSCC). Increasing the selected initial macroscopic resection margin distance beyond the tumor tissue may help prevent IAR; however, the existence of predictive factors for IAR and IAR repetition numbers remains unclear. This study aimed to identify predictive factors for IAR and to evaluate the IAR repetition numbers in soft tissue for surgically treated OSCC. METHODS: A cohort of 197 patients surgically treated for OSCC between 2008 and 2019 was retrospectively reviewed (44 patients with IAR and 153 patients without IAR). Clinical parameters (tumor location, midline involvement, clinical T-status, time between staging imaging and surgery, bone resection, monopolar use, and reconstruction flap size) and histopathological parameters (pathologic T-status [pT-status], grading, vascular invasion, and lymphatic invasion) of the two groups were compared. RESULTS: Patients with and without IAR differed in their histopathological parameters, such as pT-status above 2 (47.7% vs. 28.1%, p = 0.014) and lymphatic invasion (13.6% vs. 4.6%, p = 0.033); however, their clinical parameters were similar (all p > 0.05). Only pT-status above 2 was predictive for IAR in a multivariable regression analysis (odds ratio 2.062 [confidence interval 1.008-4.221], p = 0.048). The IAR repetition numbers varied from zero to two (zero = 84.4%, one = 11.4%, and two = 2.3%). CONCLUSIONS: Only postoperative available pT-status was identified as a predictive factor for IAR, underscoring the importance of improving preoperative or intraoperative tumor visualization in OSCC before selecting the initial macroscopic resection margin distance to avoid IAR.

Influence of perioperative blood pressure regulation on postoperative delirium in patients undergoing head and neck free flap reconstruction.

BACKGROUND: Postoperative delirium (POD) is a serious complication in patients undergoing microvascular head and neck reconstruction. Whether intraoperative and postoperative blood pressure regulation are risk factors for POD remains unclear. This study aimed to highlight the relationships between intraoperative and postoperative blood pressure regulation and POD in microvascular head and neck reconstruction. METHODS: Data from 433 patients who underwent microvascular head and neck reconstruction at our department of oral and maxillofacial surgery between 2011 and 2019 were retrospectively analyzed. The 55 patients with POD were matched with 55 patients without POD in terms of tracheotomy, flap type, and flap location, and the intraoperative and postoperative systolic and mean blood pressure values were compared between the two groups. RESULTS: Patients with POD showed lower intraoperative and postoperative minimum mean arterial pressure (MAP) values than patients without POD (60.0 mmHg vs. 65.0 mmHg, p < 0.001; and 56.0 mmHg vs. 62.0 mmHg, p < 0.001; respectively). A lower intraoperative minimum MAP value was identified as predictor for POD (odds ratio [OR] 1.246, 95% confidence interval [CI] 1.057-1.472, p = 0.009). The cut-off value for intraoperative MAP for predicting POD was ≤ 62.5 mmHg (area under the curve [AUC] 0.822, 95% CI 0.744-0.900, p < 0.001). CONCLUSIONS: Maintaining a stable intraoperative minimum MAP of > 62.5 mmHg could help to reduce the incidence of POD in microvascular head and neck reconstruction.

The role of potassium in depth profiling of the tumor border in bone-invasive oral cancer using laser-induced breakdown spectroscopy (LIBS): a pilot study.

PURPOSE: Microscopic tumor spread beyond the macroscopically visible tumor mass in bone represents a major risk in surgical oncology, where the spatial complexity of bony resection margins cannot be countered with rapid bone analysis techniques. Laser-induced breakdown spectroscopy (LIBS) has recently been introduced as a promising option for rapid bone analysis. The present study aimed to use LIBS-based depth profiling based on electrolyte disturbance tracking to evaluate the detection of microscopic tumor spread in bone. METHODS: After en bloc resection, the tumor-infiltrated mandible section of a patient's segmental mandibulectomy specimen was natively investigated using LIBS. Spectral and electrolytic depth profiles were analyzed across 30 laser shots per laser spot position in healthy bone and at the tumor border. For the histological validation of the lasered positions, the mandibular section was marked with a thin separating disc. RESULTS: Solid calcium (Ca) from hydroxyapatite and soluble Ca from dissolved Ca can be reliably differentiated using LIBS and reflect the natural heterogeneity of healthy bone. Increased potassium (K) emission values in otherwise typically healthy bone spectra are the first spectral signs of tumorous bone invasion. LIBS-based depth profiles at the tumor border region can be used to track tumor-associated changes within the bone with shot accuracy based on the distribution of K. CONCLUSION: Depth profiling using LIBS might enable the detection of microscopic tumor spread in bone. In the future, direct electrolyte tracking using LIBS should be applied to other intraoperative challenges in surgical oncology to advance rapid bone analysis by spectroscopic-optical techniques.

Flap perfusion monitoring with an attached surface probe in microvascular reconstruction of the oral cavity.

OBJECTIVES: Postoperative flap monitoring is essential in oral microvascular reconstruction for timely detection of vascular compromise. This study investigated the use of attached surface probes for the oxygen-2-see (O2C) analysis system (LEA Medizintechnik, Germany) for intraoral flap perfusion monitoring. MATERIALS AND METHODS: The study included 30 patients who underwent oral reconstruction with a microvascular radial-free forearm flap (RFFF) or anterolateral thigh flap (ALTF) between 2020 and 2022. Flap perfusion was measured with attached (3-mm measurement depth) and unattached surface probes (2- and 8-mm measurement depths) for the O2C analysis system at 0, 12, 24, 36, and 48 h postoperatively. Flap perfusion monitoring with attached surface probes was evaluated for cut-off values for flap blood flow, hemoglobin concentration, and hemoglobin oxygen saturation indicative of vascular compromise and for accuracy and concordance with unattached surface probes. RESULTS: Three RFFFs were successfully revised, and one ALTF was unsuccessfully revised. The cut-off values indicative of vascular compromise for flap perfusion monitoring with attached surface probes were for RFFF and ALTF: blood flow < 60 arbitrary units (AU) and < 40AU, hemoglobin concentration > 100AU and > 80AU (both > 10% increase), and hemoglobin oxygen saturation < 40% and < 30%. Flap perfusion monitoring with attached surface probes yielded a 97.1% accuracy and a Cohen's kappa of 0.653 (p < 0.001). CONCLUSIONS: Flap perfusion monitoring with attached surface probes for the O2C analysis system detected vascular compromise accurately and concordantly with unattached surface probes. CLINICAL RELEVANCE: Attached surface probes for the O2C analysis system are a feasible option for intraoral flap perfusion monitoring.

Effect of head-mounted displays on students' acquisition of surgical suturing techniques compared to an e-learning and tutor-led course: a randomized controlled trial.

BACKGROUND: Although surgical suturing is one of the most important basic skills, many medical school graduates do not acquire sufficient knowledge of it due to its lack of integration into the curriculum or a shortage of tutors. E-learning approaches attempt to address this issue but still rely on the involvement of tutors. Furthermore, the learning experience and visual-spatial ability appear to play a critical role in surgical skill acquisition. Virtual reality head-mounted displays (HMDs) could address this, but the benefits of immersive and stereoscopic learning of surgical suturing techniques are still unclear. MATERIAL AND METHODS: In this multi-arm randomized controlled trial, 150 novices participated. Three teaching modalities were compared: an e-learning course (monoscopic), an HMD-based course (stereoscopic, immersive), both self-directed and a tutor-led course with feedback. Suturing performance was recorded by video camera both before and after course participation (>26 h of video material) and assessed in a blinded fashion using the Objective Structured Assessment of Technical Skills (OSATS) Global Rating Score (GRS). Furthermore, the optical flow of the videos was determined using an algorithm. The number of sutures performed was counted, the visual-spatial ability was measured with the Mental Rotation Test (MRT), and courses were assessed with questionnaires. RESULTS: Students' self-assessment in the HMD-based course was comparable to that of the tutor-led course and significantly better than in the e-learning course ( P =0.003). Course suitability was rated best for the tutor-led course ( x̄ =4.8), followed by the HMD-based ( x̄ =3.6) and e-learning ( x̄ =2.5) courses. The median ΔGRS between courses was comparable ( P =0.15) at 12.4 (95% CI 10.0-12.7) for the e-learning course, 14.1 (95% CI 13.0-15.0) for the HMD-based course, and 12.7 (95% CI 10.3-14.2) for the tutor-led course. However, the ΔGRS was significantly correlated with the number of sutures performed during the training session ( P =0.002), but not with visual-spatial ability ( P =0.615). Optical flow ( R2 =0.15, P <0.001) and the number of sutures performed ( R2 =0.73, P <0.001) can be used as additional measures to GRS. CONCLUSION: The use of HMDs with stereoscopic and immersive video provides advantages in the learning experience and should be preferred over a traditional web application for e-learning. Contrary to expectations, feedback is not necessary for novices to achieve a sufficient level in suturing; only the number of surgical sutures performed during training is a good determinant of competence improvement. Nevertheless, feedback still enhances the learning experience. Therefore, automated assessment as an alternative feedback approach could further improve self-directed learning modalities. As a next step, the data from this study could be used to develop such automated AI-based assessments.

Development of machine learning and multivariable models for predicting blood transfusion in head and neck microvascular reconstruction for risk-stratified patient blood management.

BACKGROUND: Although blood transfusions have adverse consequences for microvascular head and neck reconstruction, they are frequently administered. Pre-identifying patients would allow risk-stratified patient blood management. METHODS: Development of machine learning (ML) and logistic regression (LR) models based on retrospective inclusion of 657 patients from 2011 to 2021. Internal validation and comparison with models from the literature by external validation. Development of a web application and a score chart. RESULTS: Our models achieved an area under the receiver operating characteristic curve (ROC-AUC) of up to 0.825, significantly outperforming LR models from the literature. Preoperative hemoglobin, blood volume, duration of surgery and flap type/size were strong predictors. CONCLUSIONS: The use of additional variables improves the prediction for blood transfusion, while models seems to have good generalizability due to surgical standardization and underlying physiological mechanism. The ML models developed showed comparable predictive performance to an LR model. However, ML models face legal hurdles, whereas score charts based on LR could be used after further validation.

Impacts of vascular comorbidities on free flap perfusion in microvascular head and neck reconstruction.

PURPOSE: Arterial hypertension (AHTN), type 2 diabetes mellitus (DM), and atherosclerotic vascular disease (ASVD) are common vascular comorbidities in patients undergoing reconstruction of the head and neck region with a microvascular free flap. These conditions may affect flap perfusion (microvascular blood flow and tissue oxygenation), which is a prerequisite for flap survival and thus reconstruction success. This study aimed to investigate the impacts of AHTN, DM, and ASVD on flap perfusion. METHODS: Data from 308 patients who underwent successful reconstruction of the head and neck region with radial free forearm flaps, anterolateral thigh flaps, or fibula free flaps between 2011 and 2020 were retrospectively analyzed. Flap perfusion was measured intraoperatively and postoperatively with the O2C tissue oxygen analysis system. Flap blood flow, hemoglobin concentration, and hemoglobin oxygen saturation were compared between patients with and without AHTN, DM, and ASVD. RESULTS: Intraoperative hemoglobin oxygen saturation and postoperative blood flow were lower in patients with ASVD than in patients without ASVD (63.3% vs. 69.5%, p = 0.046; 67.5 arbitrary units [AU] vs. 85.0 AU, p = 0.036; respectively). These differences did not persist in the multivariable analysis (all p > 0.05). No difference was found in intraoperative or postoperative blood flow or hemoglobin oxygen saturation between patients with and without AHTN or DM (all p > 0.05). CONCLUSION: Perfusion of microvascular free flaps used for head and neck reconstruction is not impaired in patients with AHTN, DM, or ASVD. Unrestricted flap perfusion may contribute to the observed successful use of microvascular free flaps in patients with these comorbidities.

Real-time detection of bone-invasive oral cancer with laser-induced breakdown spectroscopy: A proof-of-principle study.

OBJECTIVES: Intraoperative definition of resection margin status in bone-invasive oral cancer is a fundamental problem in oncologic surgery due to the lack of rapid bone analysis methods. Laser-induced breakdown spectroscopy (LIBS) provides direct measurement with real-time examination of a minimal tissue sample. This proof-of-principle study aimed to evaluate the possibility of distinguishing tumorous and healthy areas with LIBS. MATERIALS AND METHODS: LIBS experiments were executed on native segmental mandibulectomy specimens from 15 patients with bone-invasive oral cancer. Normalized and intensity-matched spectra were compared. Under biological derivation, peak area calculation and principal component analysis (PCA) were applied. The discriminatory power of the PCAs was correlated with the architectural and cytological characteristics of the lasered tumor tissue. Receiver operating characteristics analysis was used to evaluate the performance of LIBS in the real-time detection of bone-invasive cancer. RESULTS: Calcium (Ca), which is high in healthy bone, is replaced by potassium (K) and sodium (Na) in bone-invasive cancer. The degree of stromal induction is significantly correlated with the discriminatory power between healthy and tumorous spectra. In this study, LIBS ensured an overall sensitivity of 95.51% and a specificity of 98.64% via the intracellular detection of K and Na. CONCLUSION: This study demonstrated robust real-time detection of bone-invasive oral cancer with LIBS, which may lay the foundation for establishing LIBS as a rapid bone analysis method. Further development of a LIBS-guided assessment of bone tumor resection margins might reduce the extent of bony resection without compromising oncologic safety.

Advantages of a Training Course for Surgical Planning in Virtual Reality for Oral and Maxillofacial Surgery: Crossover Study.

BACKGROUND: As an integral part of computer-assisted surgery, virtual surgical planning (VSP) leads to significantly better surgery results, such as for oral and maxillofacial reconstruction with microvascular grafts of the fibula or iliac crest. It is performed on a 2D computer desktop screen (DS) based on preoperative medical imaging. However, in this environment, VSP is associated with shortcomings, such as a time-consuming planning process and the requirement of a learning process. Therefore, a virtual reality (VR)-based VSP application has great potential to reduce or even overcome these shortcomings due to the benefits of visuospatial vision, bimanual interaction, and full immersion. However, the efficacy of such a VR environment has not yet been investigated. OBJECTIVE: This study aimed to demonstrate the possible advantages of a VR environment through a substep of VSP, specifically the segmentation of the fibula (calf bone) and os coxae (hip bone), by conducting a training course in both DS and VR environments and comparing the results. METHODS: During the training course, 6 novices were taught how to use a software application in a DS environment (3D Slicer) and in a VR environment (Elucis) for the segmentation of the fibula and os coxae, and they were asked to carry out the maneuvers as accurately and quickly as possible. Overall, 13 fibula and 13 os coxae were segmented for each participant in both methods (VR and DS), resulting in 156 different models (78 fibula and 78 os coxae) per method (VR and DS) and 312 models in total. The individual learning processes in both environments were compared using objective criteria (time and segmentation performance) and self-reported questionnaires. The models resulting from the segmentation were compared mathematically (Hausdorff distance and Dice coefficient) and evaluated by 2 experienced radiologists in a blinded manner. RESULTS: A much faster learning curve was observed for the VR environment than the DS environment (ß=.86 vs ß=.25). This nearly doubled the segmentation speed (cm3/min) by the end of training, leading to a shorter time (P<.001) to reach a qualitative result. However, there was no qualitative difference between the models for VR and DS (P=.99). The VR environment was perceived by participants as more intuitive and less exhausting, and was favored over the DS environment. CONCLUSIONS: The more rapid learning process and the ability to work faster in the VR environment could save time and reduce the VSP workload, providing certain advantages over the DS environment.

Impact of age on microvascular free flap perfusion in head and neck reconstruction.

OBJECTIVE: Aging is associated with structural and functional cardiovascular changes that may affect microvascular free flap perfusion, which is a prerequisite for flap viability and flap success. This study is aimed to investigate the impact of age on flap perfusion. STUDY DESIGN: Intraoperative and postoperative flap perfusion of 348 patients who underwent successful reconstruction with a radial free forearm flap (RFFF), anterolateral thigh flap (ALTF), or fibular free flap (FFF) was retrospectively analyzed and compared between older (>70 years) and younger patients (≤70 years) using the Mann-Whitney test and linear regression models. RESULTS: Intraoperative flap blood flow and hemoglobin concentration (55.5 arbitrary units [AU] vs 69.3 AU, P = .004; 42.5 AU vs 47.3 AU, P = .016, respectively) were reduced in ALTFs in older patients compared with younger patients. These 2 differences did not persist in multivariable testing (P = .097 and P = .323, respectively). No other differences were observed between the older and younger patients in terms of intraoperative and postoperative flap blood flow, hemoglobin concentration, and hemoglobin oxygen saturation in RFFFs, ALTFs, and FFFs (all P > .05). CONCLUSIONS: Age has no impact on microvascular free flap perfusion in RFFFs, ALTFs, and FFFs. This could contribute to the observed equal success of free flaps in older patients.

Tolerable degree of muscle sacrifice when harvesting a vastus lateralis or myocutaneous anterolateral thigh flap.

The myocutaneous anterolateral thigh (ALT) and vastus lateralis (VL) flaps include a large muscle mass and a sufficient vascular pedicle, and they have been used for decades to reconstruct traumatic and acquired defects of the head and neck and extremities. In spite of these benefits, musculoskeletal dysfunction was reported in nearly 1 out of 20 patients at follow-up. It is unclear whether the recently proposed muscle-sparing flap-raising approach could preserve VL muscle function and whether patients at increased risk could benefit from such an approach. Therefore, we performed a predictive dynamic gait simulation based on a biological motion model with gradual weakening of the VL during a self-selected and fast walking speed to determine the compensable degree of VL muscle reduction. Muscle force, joint angle, and joint moment were measured. Our study showed that VL muscle reduction could be compensated up to a certain degree, which could explain the observed incidence of musculoskeletal dysfunction. In elderly or fragile patients, the VL muscle should not be reduced by 50% or more, which could be achieved by muscle-sparing flap-raising of the superficial partition only. In young or athletic patients, a VL muscle reduction of 10%, which corresponds to a muscle cuff, has no relevant effect. Yet, a reduction of more than 30% leads to relevant weakening of the quadriceps. Therefore, in this patient population with the need for a large portion of muscle, alternative flaps should be considered. This study can serve as the first basis for further investigations of human locomotion after flap-raising.

Comparison of [99mTc]Tc-tilmanocept with [99mTc]Tc-sulphur colloids and [99mTc]Tc-albumin colloids for sentinel lymph node detection in patients with cutaneous malignancies of the head.

PURPOSE: Sentinel lymph node (SLN) biopsy is a staging procedure in the management of cutaneous malignancies of the head. The ideal radiopharmaceutical is controversial. This study aimed to compare [99mTc]Tc-tilmanocept (TcTM) with [99mTc]Tc-sulphur colloid (TcSC) and [99mTc]Tc-albumin colloid (TcAC) for SLN detection in the head and neck region. METHODS: Data from 62 patients with cutaneous malignancies of the head who were injected with TcTM, TcSC, or TcAC before SLN imaging (SLN-I) and SLN excision (SLN-E) between 2012 and 2021 were retrospectively analysed. SLN-I was performed using planar lymphoscintigraphy and SPECT/CT, and a gamma probe was used for SLN-E. The SLN-I localisation rate (patients with SLNs) and degree (SLN number) and SLN-E relocalisation rate (patients with SLNs) and ratio (SLN number in SLN-E/SLN number in SLN-I) were compared between TcTM, TcSC, and TcAC. RESULTS: TcTM showed similar SLN-I localisation rates for primaries in the anterior and posterior head region compared with TcSC (84.6% vs. 72.4%, p=0.680; both 100.0%) and TcAC (84.6% vs. 75.0%, p=1.000; both 100.0%). The SLN-I localisation degree for TcTM was higher for primaries in the anterior head region and similar for primaries in the posterior head region compared with TcSC (3.2 vs. 2.3, p=0.034; and 1.8 vs. 2.2, p=0.506) and TcAC (3.2 vs. 2.0, p=0.038; and 1.8 vs. 2.7, p=0.329). The SLN-E relocalisation rates and ratios were similar for all. CONCLUSION: On the basis of a limited study design that compared three different tracers in three different patient groups, TcTM showed comparable overall performance to TcSC and TcAC.

Smoking and microvascular free flap perfusion in head and neck reconstruction: radial free forearm flaps and anterolateral thigh flaps.

Head and neck reconstruction with microvascular free flaps is frequently performed in smokers. Smoking causes various alterations in the cardiovascular system. The aim of this study was to investigate the effects of smoking on flap perfusion as a critical factor for flap survival. A total of 370 patients reconstructed with a radial free forearm flap (RFFF) or anterolateral thigh flap (ALTF) in the head and neck region between 2011 and 2020 were retrospectively analyzed. Flap perfusion measurements with the O2C tissue oxygen analysis system were compared between nonsmokers, light smokers (< 20 pack-years), and heavy smokers (≥ 20 pack-years). The blood flow was intraoperatively equal in RFFFs (84.5 AU vs. 84.5 AU; p = 0.900) and increased in ALTFs (80.5 AU vs. 56.5 AU; p = 0.001) and postoperatively increased in RFFFs (114.0 AU vs. 86.0 AU; p = 0.035) and similar in ALTFs (70.5 AU vs. 71.0 AU; p = 0.856) in heavy smokers compared to nonsmokers. The flap survival rate was similar in nonsmokers, light smokers, and heavy smokers (97.3%, 98.4%, and 100.0%). Smoking partially increases rather than decreases microvascular free flap perfusion, which may contribute to similar flap survival rates in smokers and nonsmokers.

Augmented Reality-Based Surgery on the Human Cadaver Using a New Generation of Optical Head-Mounted Displays: Development and Feasibility Study.

BACKGROUND: Although nearly one-third of the world's disease burden requires surgical care, only a small proportion of digital health applications are directly used in the surgical field. In the coming decades, the application of augmented reality (AR) with a new generation of optical-see-through head-mounted displays (OST-HMDs) like the HoloLens (Microsoft Corp) has the potential to bring digital health into the surgical field. However, for the application to be performed on a living person, proof of performance must first be provided due to regulatory requirements. In this regard, cadaver studies could provide initial evidence. OBJECTIVE: The goal of the research was to develop an open-source system for AR-based surgery on human cadavers using freely available technologies. METHODS: We tested our system using an easy-to-understand scenario in which fractured zygomatic arches of the face had to be repositioned with visual and auditory feedback to the investigators using a HoloLens. Results were verified with postoperative imaging and assessed in a blinded fashion by 2 investigators. The developed system and scenario were qualitatively evaluated by consensus interview and individual questionnaires. RESULTS: The development and implementation of our system was feasible and could be realized in the course of a cadaver study. The AR system was found helpful by the investigators for spatial perception in addition to the combination of visual as well as auditory feedback. The surgical end point could be determined metrically as well as by assessment. CONCLUSIONS: The development and application of an AR-based surgical system using freely available technologies to perform OST-HMD-guided surgical procedures in cadavers is feasible. Cadaver studies are suitable for OST-HMD-guided interventions to measure a surgical end point and provide an initial data foundation for future clinical trials. The availability of free systems for researchers could be helpful for a possible translation process from digital health to AR-based surgery using OST-HMDs in the operating theater via cadaver studies.

Dimensions of perforator flaps on the lower leg depending on localization.

INTRODUCTION: The soleus perforator flap and the peroneal perforator flap could be alternatives to the radial forearm flap for head and neck reconstruction. However, their flap dimensions remain unknown. This study aims to determine the dimensions of both flaps and allow preoperative planning for reconstruction based on clinical parameters. MATERIALS & METHODS: Computed tomography records of 296 patients dated from 2009 through 2019 were retrospectively analyzed. Virtual three-dimensional flap models of the soleus perforator flap and peroneal perforator flap were aligned to segmented leg models, and flap thickness and volume were determined. Associations of flap thickness and volume with clinical parameters were evaluated, and a calculation method was derived. RESULTS: The soleus perforator flap had an average thickness of 8.7 mm (4.8 mm) and an average volume of 0.9 cm³ (0.5 cm³) per square centimeter surface area. The peroneal perforator flap had an average thickness of 6.4 mm (3.8 mm) and an average volume of 0.8 cm³ (0.4 cm³) per square centimeter surface area. The soleus perforator flap was thicker and more voluminous than the peroneal perforator flap (both p<0.001). For both flaps, leg circumference was the strongest predictor of flap thickness (ß=0.524, p<0.001 and ß=0.700, p<0.001, respectively) and flap volume (ß=0.535, p<0.001 and ß=0.712, p<0.001, respectively). CONCLUSION: Dimensions of the soleus perforator and the peroneal perforator flaps are similar to those of the radial forearm flap. Preoperative planning of flap dimensions, such as flap thickness and volume, can help the surgeons select the appropriate flap.

Impact of secondary tumor-free resection margins in soft tissue on local, regional, and distant recurrence in R0-resected oral squamous cell carcinoma.

BACKGROUND: The impact of additional soft tissue resection on recurrence of oral squamous cell carcinoma (OSCC) remains controversial. The study aim was to compare recurrence between patients with secondary tumor-free resection margins after intraoperative additional resection (STF-RM) and patients with primary tumor-free resection margins without additional resection (PTF-RM). METHODS: Forty-five patients with STF-RM were matched with patients with PTF-RM according to Union for International Cancer Control stage, tumor location, and treatment modality and compared for local, regional, and distant recurrence. RESULTS: Patients with STF-RM showed lower local and distant control rates compared to patients with PTF-RM (66.2% vs. 82.8%; p = 0.045 and 86.3% vs. 100.0%; p = 0.021). STF-RM was the only predictor of local recurrence accounting for tumor (T) status, nodal (N) status, tumor grade, margin distance, and extracapsular extension (hazard ratio 4.21 [95% confidence interval 1.26-14.04]; p = 0.019). CONCLUSIONS: STF-RM have an adverse impact on local and distant recurrence of OSCC.

Automated PD-L1 Scoring Using Artificial Intelligence in Head and Neck Squamous Cell Carcinoma.

Immune checkpoint inhibitors (ICI) represent a new therapeutic approach in recurrent and metastatic head and neck squamous cell carcinoma (HNSCC). The patient selection for the PD-1/PD-L1 inhibitor therapy is based on the degree of PD-L1 expression in immunohistochemistry reflected by manually determined PD-L1 scores. However, manual scoring shows variability between different investigators and is influenced by cognitive and visual traps and could therefore negatively influence treatment decisions. Automated PD-L1 scoring could facilitate reliable and reproducible results. Our novel approach uses three neural networks sequentially applied for fully automated PD-L1 scoring of all three established PD-L1 scores: tumor proportion score (TPS), combined positive score (CPS) and tumor-infiltrating immune cell score (ICS). Our approach was validated using WSIs of HNSCC cases and compared with manual PD-L1 scoring by human investigators. The inter-rater correlation (ICC) between human and machine was very similar to the human-human correlation. The ICC was slightly higher between human-machine compared to human-human for the CPS and ICS, but a slightly lower for the TPS. Our study provides deeper insights into automated PD-L1 scoring by neural networks and its limitations. This may serve as a basis to improve ICI patient selection in the future.