A 3D Analysis of Plating Strategies in Mandibular Reconstruction: A Randomized Control Pilot Study.

OBJECTIVE(S): The purpose of this study was to compare computer-assisted mandibular plating to conventional plating using quantitative metrics. METHODS: Patients scheduled to undergo mandibular reconstruction were randomized to three-dimensional modelling for preoperative plate bending or intraoperative freehand bending. Preoperative and postoperative head and neck computed tomography scans were obtained to generate computer models of the reconstruction. The overall plate surface contact area, mean plate-to-bone distance, degree of conformance, and position of the condylar head within the glenoid fossa between pre- and post-operative scans were calculated. RESULTS: Twenty patients were included with a mean age of 57.8 years (standard deviation [SD] = 13.6). The mean follow-up time was 9.8 months (range = 1.6-22.3). Reconstruction was performed with fibular (25%) or scapular free flaps (75%). The percentage of surface contact between the reconstructive plate and mandible was improved with three-dimensional models compared to freehand bending (93.9 ± 7.7% vs. 78.0 ± 19.9%, p = 0.04). There was improved overall plate-to-bone distance (3D model: 0.7 ± 0.31 mm vs. conventional: 1.3 ± 0.8 mm, p = 0.06). Total intraoperative time was non-significantly decreased with the use of a model (3D model: 726.5 ± 89.1 min vs. conventional: 757.3 ± 84.1 min, p = 0.44). There were no differences in condylar head position or postoperative complications. CONCLUSION: Computer-assisted mandibular plating can be used to improve the accuracy of plate contouring. LEVEL OF EVIDENCE: 2 Laryngoscope, 134:2182-2186, 2024.

An interactive augmented reality software for facial reconstructive surgeries.

BACKGROUND AND OBJECTIVE: Surgical trainees need a lot of training and practice before being able to operate independently. The current approach of surgical education mainly involves didactic teaching and psychomotor training through physical models or real tissue. Due to the unavailability of physical resources and lack of objective ways of evaluation, there is a demand for developing alternative training methods for surgeons. In this paper, we present an application that provides additional training opportunities to surgical trainees in the field of facial reconstructive surgeries. METHODS: We built a mobile augmented reality application that helps the user to visualize important concepts and experiment with different surgical plans for facial reconstructive surgeries. The application can overlay relaxed skin tension lines on a live video input or a patient's photo, which serve as bases for aligning a skin flap. A surgical trainee can interactively compare different skin flap design choices with estimated final scars on a photo of a patient. Data collection capability is also added to the application, and we performed a Monte Carlo experiment with simulated users (five classes of 100 users each) as an example of objectively measuring user performance. RESULTS: The application can overlay relaxed skin tension lines on a patient's face in real time on a modern mobile device. Accurate overlays were achieved in over 91% as well as 84% and 88% out of 263 generated face images, depending on the method. Visual comparisons of the three overlay methods are presented on sample faces from different population groups. From the Monte Carlo experiment, we see that user actions in each class follow a normal distribution with a distinct set of parameters. CONCLUSIONS: This application can serve as a basis for teaching surgical trainees the fundamentals of different facial reconstructive procedures, especially concepts related to relaxed skin tension lines and skin flaps. It can objectively evaluate the performance of surgical trainees in a course. This setup focuses on illustrating the relationship between the orientation of skin flaps and relaxed skin tension lines, which is a prerequisite of minimizing scarring in patients in addition to good surgical techniques.

Cigarette smoking cessation, duration of smoking abstinence, and head and neck squamous cell carcinoma prognosis.

BACKGROUND: Tobacco use is a major risk factor for developing head and neck squamous cell carcinoma (HNSCC). However, the prognostic associations with smoking cessation are limited. The authors assessed whether smoking cessation and increased duration of abstinence were associated with improved overall (OS) and HNSCC-specific survival. METHODS: Clinicodemographic and smoking data from patients with HNSCC at Princess Margaret Cancer Center (2006-2019) were prospectively collected. Multivariable Cox and Fine and Gray competing-risk models were used to assess the impact of smoking cessation and duration of abstinence on overall mortality and HNSCC-specific/noncancer mortality, respectively. RESULTS: Among 2482 patients who had HNSCC, former smokers (adjusted hazard ratio [aHR], 0.71; 95% CI, 0.58-0.87; p = .001; N = 841) had a reduced risk of overall mortality compared with current smokers (N = 931). Compared with current smokers, former smokers who quit >10 years before diagnosis (long-term abstinence; n = 615) had the most improved OS (aHR, 0.72; 95% CI, 0.56-0.93; p = .001). The 5-year actuarial rates of HNSCC-specific and noncancer deaths were 16.8% and 9.4%, respectively. Former smokers (aHR, 0.71; 95% CI, 0.54-0.95; p = .019) had reduced HNSCC-specific mortality compared with current smokers, but there was no difference in noncancer mortality. Abstinence for >10 years was associated with decreased HNSCC-specific death compared with current smoking (aHR, 0.64; 95% CI, 0.46-0.91; p = .012). Smoking cessation with a longer duration of quitting was significantly associated with reduced overall and HNSCC-specific mortality in patients who received primary radiation. CONCLUSIONS: Smoking cessation before the time of diagnosis reduced overall mortality and cancer-specific mortality among patients with HNSCC, but no difference was observed in noncancer mortality. Long-term abstinence (>10 pack-years) had a significant OS and HNSCC-specific survival benefit.

Cross-legged modification for medial sural artery perforator flap harvest.

When thin and pliable free tissue is needed, the medial sural artery perforator (MSAP) flap provides an excellent option with minimal donor site morbidity. However, among its pitfalls include difficult patient positioning and surgeon ergonomics throughout the harvest. We describe a novel positioning technique that may significantly improve surgeon ergonomics and ease of MSAP flap harvest. A cross-legged modification may eliminate many of the issues associated with the classic frog-leg position. While the patient is cross-legged, the surgeon is afforded a normal field of view that is closer to their body, while simultaneously providing support to the lateral side of the gastrocnemius muscle. This pictorial essay describes this positioning technique and subsequent harvest. By incorporating a more ergonomic cross-legged position during flap elevation, many of thedrawbacks of the MSAP flap could be eliminated.

Factors predicting pharyngocutaneous fistula in patients after salvage laryngectomy for laryngeal malignancy - A multicenter collaborative cohort study.

OBJECTIVES: Pharyngocutaneous fistula (PCF) is a major morbidity of salvage total laryngectomy (TL). Understanding the factors predicting PCF is fundamental to managing laryngeal cancer. We aim to assess factors associated with PCF following salvage TL in a multicenter, international retrospective cohort study of academic centers in the US and Canada. RESULTS: In total, 550 patients post-salvage TL were identified (mean [SD; range] age, 64 [10.4; 32-90] years; 465 [85 %] male and 84 [15 %] female) between 2000 and 2014. Rate of PCF was 23 % (n = 127) with median time to PCF of 2.9 weeks. Surgical management of PCF was required in 43 % (n = 54) while 57 % (n = 73) required wound care alone. Rates of PCF differed by primary treatment modality [radiation, 20 % (n = 76); chemoradiation, 27 % (n = 40); not available (n = 6)] and use of vascularized tissue in pharyngeal closure [free/regional flap, 18 % (n = 25); no vascularized tissue/primary closure, 24 % (n = 98); not available (n = 4)]. There was no statistically significant association between PCF and treatment with chemoradiation (HR, 1.32; 95 % CI, 0.91-1.93, p = 0.14) or lack of vascularized tissue reconstruction (HR, 1.41, 95 % CI 0.91-2.18, p = 0.12). Significant association between PCF and advanced stage (T3 or T4), positive margin, close margin (<5mm), lymphovascular invasion and pre-operative tracheostomy were identified on univariable analysis. Positive surgical margin (HR, 1.91; 95 % CI, 1.11 to 3.29) was the only significant association on multivariable analysis. CONCLUSION: We highlight positive surgical margin as the only variable significantly associated with increased risk of PCF following salvage TL on multivariable analysis in a large cohort across several major head and neck oncology centers.

Parametric Multi-Scale Modeling of the Zygomaticus Major and Minor: Implications for Facial Reanimation.

ABSTRACT: Facial paralysis can severely impact functionality and mental health. Facial reanimation surgery can improve facial symmetry and movement. Zygomaticus minor (Zmin) and zygomaticus major (Zmaj) are 2 important perioral muscles, that function to elevate the upper lip, contributing to the formation of a smile. The objective of this study was to analyze the morphology in three-dimensional (3D) and quantify architectural parameters of Zmin and Zmaj. In ten formalin-embalmed specimens, Zmin and Zmaj were serially dissected and digitized at the fiber bundle level. The 2 muscles were modeled in 3D to construct high fidelity models. The 3D models were used to assess muscle morphology and quantify architectural parameters including mean fiber bundle length, physiological cross-sectional area, and line of action. Zygomaticus minor fiber bundles were oriented horizontally or slightly obliquely and had a muscular attachment to the medial modiolus. Zygomaticus minor was found to either have no partitions or medial and lateral partitions. Specimens with partitions were divided into type 1 and type 2. Type 1 consisted of a medial partition with fiber bundles attaching to the zygomatic bone at the inferior margin of the orbit. The type 2 medial partition attached to the lateral margin of the orbit to attach to the zygomatic bone. Zygomaticus major had obliquely oriented fiber bundles with most specimens having inferior and superior partitions attaching to the inferior aspect of the zygomatic bone. Zygomaticus major was found to have a greater mean fiber bundle length and physiological cross-sectional area than Zmin. The direction of the line of action of Zmin and Zmaj was closely related to fiber bundle arrangement. Detailed 3D anatomical understanding of Zmin and Zmaj, at the fiber bundle level, is critical for reconstructive surgeons performing dynamic facial reanimation. This data can be used to assist with selecting the ideal donor site for reconstruction.

Association of Plate Contouring With Hardware Complications Following Mandibular Reconstruction.

OBJECTIVES/HYPOTHESIS: Despite considerable effort being dedicated to contouring reconstruction plates, there remains limited evidence demonstrating an association between contour and reconstructive outcomes. We sought to evaluate whether optimizing mandibular reconstruction plate contouring is associated with reduced postoperative hardware complications. STUDY DESIGN: Retrospective cohort study. METHODS: A cohort study was performed with adult patients (age ≥18 years) who underwent mandibulectomy and osseous free flap reconstruction following oncologic ablation at the University Health Network in Toronto, Canada, between January 1, 2003 and December 31, 2014. Patients with computed tomography scans performed within 1 year of reconstruction were included. Computer-based three-dimensional models were generated and used to calculate the mean plate-to-bone gap (mm). The primary outcome was plate exposure. Secondary outcome included a composite of plate exposure or intraoral dehiscence. Logistic regression models were fitted for each outcome accounting for other patient and surgical characteristics associated with the primary outcome. RESULTS: Ninety-four patients met inclusion criteria, with a mean age of 60.4 (standard deviation [SD] 14.9). The mean follow-up time was 31.4 months (range 3-94). Reconstruction was performed with fibular (57%) and scapular free flaps (43%). In the multivariable model, small mean plate-to-bone gap (<1 mm) was independently associated with 86% reduced odds of plate exposure (odds ratio [OR] 0.12; 95% confidence interval [CI] 0.02-0.55). Mean plate-to-bone gap less than 1 mm was also independently associated with reduced odds of developing a composite of plate exposure or intraoral dehiscence (OR, 0.29; 95%CI, 0.11-0.75). CONCLUSION: Optimizing plate contouring during mandibular reconstruction may decrease the development of postoperative hardware complications. LEVEL OF EVIDENCE: 4 Laryngoscope, 132:61-66, 2022.

Association of Pharyngocutaneous Fistula With Cancer Outcomes in Patients After Laryngectomy: A Multicenter Collaborative Cohort Study.

Importance: Pharyngocutaneous fistula (PCF) results in an inflammatory reaction, but its association with the rate of locoregional and distant control, disease-free survival, and overall survival in laryngeal cancer remains uncertain. Objective: To determine if pharyngocutaneous fistula after salvage laryngectomy is associated with locoregional and distant control, disease-free survival, and/or overall survival. Design, Setting, and Participants: A multicenter collaborative retrospective cohort study conducted at 5 centers in Canada and the US of 550 patients who underwent salvage laryngectomy for recurrent laryngeal cancer from January 1, 2000, to December 31, 2014. The median follow-up time was 5.7 years (range, 0-18 years). Main Outcomes and Measures: Outcomes examined included locoregional and distant control, disease-free survival, and overall survival. Fine and Gray competing risk regression and Cox-proportional hazard regression models were used for outcomes. Competing risks and the Kaplan-Meier methods were used to estimate outcomes at 3 years and 5 years. Results: In all, 550 patients (mean [SD] age, 64 [10.4] years; men, 465 [85%]) met inclusion criteria. Pharyngocutaneous fistula occurred in 127 patients (23%). The difference in locoregional control between the group of patients with PCF (75%) and the non-PCF (72%) group was 3% (95% CI, -6% to 12%). The difference in overall survival between the group with PCF (44%) and the non-PCF group (52%) was 8% (95% CI, -2% to 20%). The difference in disease-free survival between PCF and non-PCF groups was 6% (95% CI, -4% to 16%). In the multivariable model, patients with PCF were at a 2-fold higher rate of distant metastases (hazard ratio, 2.00; 95% CI, 1.22 to 3.27). Distant control was reduced in those with PCF, a 13% (95% CI, 3% to 21%) difference in 5-year distant control. Conclusions and Relevance: This multicenter retrospective cohort study found that development of PCF after salvage laryngectomy is associated with an increased risk for the development of distant metastases.

Perioperative Mortality Risk in Patients Undergoing Transoral Robotic Surgery for T1-T2 Oropharyngeal Squamous Cell Carcinoma: A National Cancer Database Study.

The National Cancer Database is a joint project of the Commission on Cancer of the American College of Surgeons and the American Cancer Society. The American College of Surgeons and the Commission on Cancer have not verified and are not responsible for the analytic or statistical methods used or for the conclusions drawn from these data by the investigators. INTRODUCTION: Transoral robotic surgery (TORS) is well established as initial definitive treatment for early-stage oropharyngeal squamous cell carcinoma (OPSCC) as an alternative to radiation therapy with similar survival rates. While proponents of TORS focus on the reduced morbidity of treatment compared to open procedures, shortened hospital admissions and equivalent survival outcomes to non-surgical treatment, there remain concerns over the risk of mortality within the acute perioperative period. Therefore, we sought to determine the 30-day and 90-day perioperative mortality risk using the National Cancer Database. METHODS: A retrospective cohort analysis was performed for patients diagnosed with pathologic T1/2 OPSCC between January 1, 2010, and December 31, 2016 that underwent primary surgical treatment with TORS and was not restricted by HPV status. The primary outcome was 30-day perioperative mortality. The secondary outcome was 90-day perioperative mortality. Univariable analysis was used to identify variables associated with 30-day perioperative mortality. RESULTS: In total, 4,127 patients (mean [SD; range] age, 59 [9.5; 22-90] years; 3,476 [84%] men and 651 [16%] women) met inclusion criteria. The number of patients with pT1-2 OPSCC undergoing TORS increased three-fold between 2010 (279/4,127; 7%) to 2016 (852/4,127; 21%). The overall 30-day and 90-day perioperative mortality rate for TORS during the study period was 0.6% (23/4,127) and 0.9% (38/4,127), respectively. On univariable analysis (UVA), age≥65 was the only predictor of 30-day perioperative mortality (OR 3.41; 95% CI 1.49-7.81). CONCLUSION: The overall risk of all cause mortality following TORS for early-stage OPSCC remains low. The risk of mortality is higher in elderly patients and should be considered, in addition to previously established risk factors, during patient selection and counselling.

Establishing Orbital Floor Symmetry to Support Mirror Imaging in Computer-Aided Reconstruction of the Orbital Floor.

BACKGROUND: Surgical precision in the reconstruction of the orbital floor is crucial to functional visual and aesthetic outcomes. Increasingly, computer-aided design is being utilized to aid in precise preoperative planning by using the mirror images of the unaffected side. The authors aim to use 3-dimensional (3D) quantitative analysis to establish whether the native orbital floor topography is sufficiently symmetric to support this practice. METHODS: Ten high resolution head and neck computed tomography scans of patients without periorbital pathology were obtained. These were imported into a 3D medical image processing software and segmented to isolate bilateral orbital floors. Each native orbital floor was compared to the mirror image of the contralateral side by conformance map computation. Data collection included measures of 25% and 75% quartile, median, mean, standard deviation, and root-mean-square (RMS). RESULTS: The topographic analysis demonstrated a high degree of topographic conformance with a mean RMS of 0.58 ±â€Š0.37 mm. Further volumetric analysis comparing the total orbital volume between each side also demonstrates a high degree of volumetric symmetry with a mean difference of 0.55 mL (P = 0.30). CONCLUSION: Comparison of the native orbital floor and the mirror image of the contralateral side by conformance map computation and volumetric analysis demonstrated a high degree of morphologic similarity. The native orbital floor topography provides optimal symmetry to support mirror imaging techniques used in orbital floor reconstruction.

Quantitative Analysis of Surgical Working Space During Endoscopic Skull Base Surgery.

Objectives Selective dissection of intranasal anatomy may improve visualization and maneuverability at the skull base. We aimed to quantify the dimensions of working space and angles achieved following sequential removal of intranasal structures using an endoscopic transphenoidal approach to the skull base. Methods Cone beam computed tomography scans of four cadaveric heads were obtained for registration of an optical tracking system. Each head was sequentially dissected: (1) sphenoidotomy and limited posterior septectomy, (2) unilateral partial middle turbinectomy, (3) bilateral partial middle turbinectomy, and (4) wide posterior septectomy. The maximal craniocaudal and mediolateral distance (mm) and angle (degrees) reached were calculated at the sphenoid face and sella. Data were analyzed using descriptive statistics and tests of statistical significance. The significance level was set at p ≤ 0.05. Results A significant improvement in both dimensions of working space was observed with each stage of dissection at the level of the sphenoid face. Maximal working space was achieved following bilateral middle turbinectomy and wide posterior septectomy with a 38 and 29% increase in working space in the mediolateral and craniocaudal dimensions, respectively. The largest stepwise increase in working space was observed with unilateral middle turbinectomy (mediolateral: 24 ± 3 mm and craniocaudal: 20 ± 3 mm). A trend toward improved degrees of visualization was observed with each stage of dissection but was not statistically significant. Conclusion Approaches to the skull base can be enhanced by selective unilateral/bilateral partial middle turbinectomy and posterior septectomy being performed to improve visualization and maximize surgical working freedom.

Analysis of simulated mandibular reconstruction using a segmental mirroring technique.

PURPOSE: When deforming pathology limits intraoperative plating of the mandible, three-dimensional (3D) models can be generated by digitally replacing the deformed segment of bone with an inverted segment from the contralateral unaffected mandible to adapt a reconstruction plate. The purpose of this study was to use 3D conformance analysis to evaluate the degree of accuracy of this "segmental mirroring" technique. METHODS: Using a pre-existing melanoma database (January 1, 2005-September 20, 2015), high-resolution computed tomography (CT) scans of the head and neck were obtained from patients without evidence of bony disease or defects involving the mandible. Using 3D software (Mimics, Materialise, Leuven, Belgium), each mandible was segmented based on four defect classes (Ic, II, IIc and III) of the Brown et al. (2016) classification system. An inverted, or "mirrored", image of each segment was digitally created and manually co-registered with the corresponding contralateral segment of the mandible. Conformance analysis was performed by calculating the root-mean-square (RMS) conformance distance and through evaluating 3D generated conformance maps. The primary outcome was degree of conformance. Data were analyzed using descriptive statistics and tests of statistical significance. The significance level was set at a p-value less than or equal to .05. RESULTS: A high degree of conformance (mean RMS < 1 mm) was observed when comparing all classes of simulated reconstruction. The closest conformance was observed for class III simulated reconstructions (mean RMS: 0.4 ± 0.2 mm). Inclusion of the condyle resulted in a reduced mean RMS conformance (class II: 0.5 ± 0.3 mm vs class IIc: 0.7 ± 0.5 mm; p = 0.01). There was no significant difference between RMS conformance distances when comparing side of simulated reconstruction. Evaluation of 3D mapping demonstrated reduced conformance with simulated reconstruction of the condyle and coronoid process. CONCLUSION: The segmental mirroring technique can be used reliably to generate highly accurate three-dimensional models that may assist with mandibular reconstruction in circumstances where bony deformity limits intraoperative adaptation of a reconstruction plate. This technique is less accurate where pathology involves the mandibular condyle and, to a lesser degree, the coronoid process.

Orbital Floor Reconstruction: 3-Dimensional Analysis Shows Comparable Morphology of Scapular and Iliac Crest Bone Grafts.

PURPOSE: Current nonvascular osseous reconstructive options for reconstruction of the orbital floor after maxillectomy include options such as scapular tip and iliac crest bone grafts. The aim of this study was to determine whether these donor sites were morphologically comparable with the orbital floor. MATERIALS AND METHODS: A retrospective cross-sectional study design was selected. By use of a pre-existing melanoma database (January 1, 2005, through September 20, 2015), computed tomography scans of the head, neck, thorax, and pelvis were obtained from patients without evidence of bony metastases. With the use of 3-dimensional software (Mimics; Materialise, Leuven, Belgium), grafts from the scapulae and iliac crests, the predictor variables, were digitally harvested, co-registered with the orbital floors bilaterally, and analyzed. The primary outcome was conformance. Data were analyzed using descriptive statistics and tests of statistical significance. The significance level was set at P<.05. RESULTS: The study sample included 10 patients (6 men and 4 women; mean age, 55 ± 18 years). Close conformance was observed when we analyzed the morphology of the orbital floor to the scapular (2.23 ± 0.31 mm) and iliac crest (2.13 ± 0.30 mm) bone grafts, with no significant difference between sites. Conformance mapping showed maximum conformance centrally (scapula, 0.001 ± 0.001 mm; iliac crest, 0.001 ± 0.001 mm), with decreased morphologic similarity peripherally (scapula, 6.09 ± 0.94 mm; iliac crest, 5.74 ± 0.88 mm). There was no significant difference in conformance between sides of graft harvest. CONCLUSIONS: When considering nonvascularized bone grafts for reconstruction of the orbital floor, both the scapula and iliac crest offer nearly complete conformance to the orbital floor structure and represent reasonable reconstructive options.

Evaluation of clinically relevant landmarks of the marginal mandibular branch of the facial nerve: A three-dimensional study with application to avoiding facial nerve palsy.

Injury to the marginal mandibular branch of the facial nerve (MMN) during surgery often results in poor functional and cosmetic outcomes. A line two finger breadths or 2 cm inferior to the border of the mandible is commonly used in planning neck incisions to avoid injury to the MMN. The purpose was to compare the two finger breadth/2 cm landmarks in predicting MMN course, and their accuracy/reliability. Thirty-one cadaveric specimens were scanned to obtain 3D surface topography (FARO® scanner). Four independent raters pinned the inferior border of the mandible and a two finger breadth line and 2cm line below. The location of each pin was digitized (Microscribe™). A preauricular flap was raised, and MMN branches were digitized and modelled (Geomagic®/Maya®) enabling quantification of the accuracy of these landmarks. The location of the two-finger breadth line was variable, spanning 25-51 mm below the inferior border of the mandible (ICC = 0.10). The most inferior MMN branch did not pass below the two-finger breadth line in any specimen, but a narrow clearance zone (≤5 mm) was found in two. In contrast, in 7/31 specimens, the most inferior MMN branch coursed below the 2 cm line and would be at risk of injury. It was concluded that an incision two finger breadths below the inferior border of the mandible could provide safer access than the 2 cm line. After an incision has been placed using the two finger-breadth landmark, caution must be exercised during dissection as branches of the MMN may lie only a few millimeters superior to the incision.

Clinically relevant landmarks of the frontotemporal branch of the facial nerve: a three-dimensional study.

The frontotemporal branch of the facial nerve (FTN) is vulnerable during craniofacial surgeries due to its superficial course and variable distribution. Surface landmarks that correlate with the underlying course of the FTN can assist in surgical planning. Estimates of the course of FTN commonly rely on Pitanguy's line (PL), which utilizes variable soft-tissue landmarks. The purpose of this study was to evaluate palpable surface landmarks to predict the course and distribution of FTN using 3D modeling. Fifteen half-heads were used. In five formalin-embalmed specimens, surface topography was obtained using a FARO® scanner and landmarks corresponding to PL, porion, supraorbital notch, frontozygomatic and zygomaticotemporal sutures, and supraorbitomeatal line (SOML) and infraorbitomeatal line (IOML) were demarcated/digitized using a Microscribe™ digitizer. A preauricular flap was raised, and branches of FTN were isolated and digitized. The data were reconstructed into 3D models (Geomagic®/Maya®) to quantify landmarks. In 10 Thiel-embalmed specimens, four independent raters identified/palpated and pinned the frontozygomatic and zygomaticotemporal sutures and PL. Data were collected and analyzed using the same protocol as in the first part of the study. Landmarking of PL was inconsistent between raters and not representative of FTN distribution. The easily identifiable surface landmarks defined in this study, a line 12 mm anterior to the porion along the SOML and IOML and a line joining the zygomaticotemporal and frontozygomatic sutures, comprehensively captured the distribution of FTN. The raters found a mean of 21 ± 2 branches between the lines out of a total of 22 ± 2 branches. These landmarks may be used clinically to avoid injury to FTN.