Bare Bone Research Articles

A rhinopithecus swarm optimization algorithm for complex optimization problem

This paper introduces a novel meta-heuristic algorithm named Rhinopithecus Swarm Optimization (RSO) to address optimization problems, particularly those involving high dimensions. The proposed algorithm is inspired by the social behaviors of different groups within the rhinopithecus swarm. RSO categorizes the swarm into mature, adolescent, and infancy individuals. Due to this division of labor, each category of individuals employs unique search methods, including vertical migration, concerted search, and mimicry. To evaluate the effectiveness of RSO, we conducted experiments using the CEC2017 test set and three constrained engineering problems. Each function in the test set was independently executed 36 times. Additionally, we used the Wilcoxon signed-rank test and the Friedman test to analyze the performance of RSO compared to eight well-known optimization algorithms: Dung Beetle Optimizer (DBO), Beluga Whale Optimization (BWO), Salp Swarm Algorithm (SSA), African Vultures Optimization Algorithm (AVOA), Whale Optimization Algorithm (WOA), Atomic Retrospective Learning Bare Bone Particle Swarm Optimization (ARBBPSO), Artificial Gorilla Troops Optimizer (GTO), and Harris Hawks Optimization (HHO). The results indicate that RSO exhibited outstanding performance on the CEC2017 test set for both 30 and 100 dimension. Moreover, RSO ranked first in both dimensions, surpassing the mean rank of the second-ranked algorithms by 7.69% and 42.85%, respectively. Across the three classical engineering design problems, RSO consistently achieves the best results. Overall, it can be concluded that RSO is particularly effective for solving high-dimensional optimization problems.

Case Report ‘Layer of Hope’: Managing Large Surface Wounds on Frontal Bare Bone in a Challenging Patient

This was a case of an elderly gentleman with large bleeding basal cell carcinoma occupying almost three quarter of the forehead managed with adjunct usage of integra acellular dermal regeneration template after lesion’s wide local excision despite challenged with patient’s newly diagnosed bicytopenia to rule out haematological malignancy. Standard management of tissue reconstruction with purely living tissue (split skin grafting) has higher risk of graft rejection due to bare bone as wound bed. This limits the neo-graft ability to achieve optimal potential of imbibition and inosculation. Thus, dermal matrix usage makes split skin grafting difficult wound bed has higher chance of surviving and hence shortens healing time and reduces hospital stay.

Optimal design of automatic generation control based on BBPSO-tuned PI for a restructured environment

ABSTRACT This paper intends to model an AGC regulator for a restructured environment using Bare Bone Particle Swarm Optimization (BBPSO). The gain-controlled Proportional–Integral (PI) Controller is designed here to enhance the performance of the BBPSO algorithm along with Gaussian distribution. The practical difficulty in handling the area control error to zero is the sudden variations in load. In practice, the tremendous contribution of deregulation in the power sector causes volatility in frequency and tie-line power deviations. To ensure the robustness of the proposed controller, three different cases of power system transactions have been considered. The performance has been validated by comparing it with Real Coded Genetic Algorithm-tuned PI controller (RCGA-PI) and Differential Evolutionary Algorithm-tuned PI controller (DE-PI) for the five area Thermal-Thermal generation test system. Moreover, the dynamic performance of an extensive range of demands and disturbances of all areas like settling time and overshoot against parametric precariousness has been done on the proposed test system.

The Benefits of Using Platelet-rich Plasma with Dermal Substitutes for Extremity Posttraumatic Skin Defects: A Short-term Outcome.

Skin injuries are very common. Skin grafting is an ongoing wound management procedure. The artificial dermis, PELNAC, has been considered in the treatment of several acute and chronic skin injuries. Platelet-rich plasma (PRP) is blood plasma with a platelet count higher than the baseline. It is presumed to act in a synergetic pattern to promote the healing of wounds. This study was conducted to assess the potential benefit of adding PRP to PELNAC as adjuvant therapy in treating posttraumatic skin. In this study, adult patients who were admitted to the hospital with extremity traumatic skin and soft tissue defects with exposed bare bone, exposed tendons, or exposed cartilage in the period between October 2019 and March 2021 were allocated to either being managed with dermal substitute (PELNAC) together with PRP (group I) or PELNAC alone (group II). Patients in group I showed a higher mean graft take rate and a lower mean time for neovascularization of the acellular dermal matrix, with a statistically highly significant difference. The Vancouver Scar Scale values showed no significant difference in either group. The PRP-treated group showed statistically significant shorter hospital stays. The addition of PRP to the treatment protocol showed better outcomes in terms of graft take rate, time for neovascularization of acellular dermal matrix, and length of hospital stay, with no side effects. The present study findings emphasize the promising outcome of PRP in addition to the standard treatment of complex wounds to achieve rapid and safe healing.

The Impact of the Nasal Mucosal Flap on Tissue Remodeling After Sinus Bone Drilling in Rabbit Models.

Frontal sinus surgery remained a challenge of restenosis or obliteration of the drainage pathway caused by the scarring and neo-osteogenesis after mucosal stripping and bone drill-out. The pedicled or free nasal mucosal flap is typically used to repair the exposed bone surface to avoid or reduce recurrence. This study aimed to explore the histopathological mechanism of mucosal flaps repairing bare bone after mucosal resection and bone drill-out in the rabbit model. Thirty New Zealand white rabbits were used. Sixteen rabbits were selected as the experimental group, and Staphylococcus aureus was used to establish the CRS model (CRS group). Fourteen healthy rabbits were allocated to the control group (NCRS group). Each group was divided into two subgroups with or without mucosal flap repair (CRS-FLAP, CRS-NFLAP, NCRS-FLAP, and NCRS-NFLAP, respectively). The bony anterior and lateral walls of the maxillary sinus of each rabbit were abraded by the drill. The bare bone was then covered with a flap in FLAP subgroups. Bone remodeling and mucosal morphological changes were observed and compared by histopathological hematoxylin and eosin and Masson staining. In the CRS-NFLAP subgroup, the regenerated epithelium lacked typical structure, accompanied by numerous inflammatory cell infiltration and collagen deposition. Conversely, the inflammatory reaction was mild in the CRS-FLAP subgroup, and there was less collagen deposition. The restored mucosal structure was like the normal mucosa. The epithelium in the NCRS-NFLAP subgroup was partially exfoliated, with few cilia, goblet cells, and glandular structures. Compared with the NCRS-NFLAP subgroup, the CRS-NFLAP subgroup showed significant bone remodeling with enhanced activity of osteoblast and osteoclast cells. Pedicled mucosal flap repair could significantly reduce local mucosal and bone remodeling in a rabbit model of CRS.

A Two-Dimensional K-Shell X-ray Fluorescence (2D-KXRF) Model for Soft Tissue Attenuation Corrections of Strontium Measurements in a Cortical Lamb Bone Sample

Human bones store elements such as calcium, phosphorus, and strontium, and accumulate toxic elements such as lead. In vivo measurements of elemental bone concentration can be done using X-ray fluorescence (XRF) techniques. Monte Carlo (MC) simulations of X-ray interactions were predominantly employed in this field to develop calibration methods that linked XRF measurements to concentrations. A simple and fast two-dimensional K-shell X-ray fluorescence model was developed to compute the KXRF signal of elements in bone and overlying soft tissue samples. The model is an alternative to MC methods and can guide future bone XRF studies. Contours of bone and soft tissue cross sections were elliptical and only KXRF signals from absorption of primary photons were considered. Predictions of the model were compared to Sr KXRF measurements using the bare lamb bone (LB) and the LB with overlying leather. XRF experiments used a small X-ray beam, silicon X-ray detector, and three positioning stages. Linear attenuation coefficients of the leather and LB were measured and used in the model. Measured and model-derived values of the Sr X-rays leather attenuation and Sr Kβ/Kα ratio agreed, but estimated bone Sr concentrations were likely overestimated. Results, approximations, future work directions, and applications were discussed.

An enhanced decision-making framework for predicting future trends of sharing economy.

This work aims to provide a reliable and intelligent prediction model for future trends in sharing economy. Moreover, it presents valuable insights for decision-making and policy development by relevant governmental bodies. Furthermore, the study introduces a predictive system that incorporates an enhanced Harris Hawk Optimization (HHO) algorithm and a K-Nearest Neighbor (KNN) forecasting framework. The method utilizes an improved simulated annealing mechanism and a Gaussian bare bone structure to improve the original HHO, termed SGHHO. To achieve optimal prediction performance and identify essential features, a refined simulated annealing mechanism is employed to mitigate the susceptibility of the original HHO algorithm to local optima. The algorithm employs a mechanism that boosts its global search ability by generating fresh solution sets at a specific likelihood. This mechanism dynamically adjusts the equilibrium between the exploration and exploitation phases, incorporating the Gaussian bare bone strategy. The best classification model (SGHHO-KNN) is developed to mine the key features with the improvement of both strategies. To assess the exceptional efficacy of the SGHHO algorithm, this investigation conducted a series of comparative trials employing the function set of IEEE CEC 2014. The outcomes of these experiments unequivocally demonstrate that the SGHHO algorithm outperforms the original HHO algorithm on 96.7% of the functions, substantiating its remarkable superiority. The algorithm can achieve the optimal value of the function on 67% of the tested functions and significantly outperforms other competing algorithms. In addition, the key features selected by the SGHHO-KNN model in the prediction experiment, including " Form of sharing economy in your region " and " Attitudes to the sharing economy ", are important for predicting the future trends of the sharing economy in this study. The results of the prediction demonstrate that the proposed model achieves an accuracy rate of 99.70% and a specificity rate of 99.38%. Consequently, the SGHHO-KNN model holds great potential as a reliable tool for forecasting the forthcoming trajectory of the sharing economy.

Baricitinib improves bone properties and biomechanics in patients with rheumatoid arthritis - results of the prospective interventional BARE BONE trial.

Rheumatoid arthritis (RA) is characterized by erosive joint damage, deterioration of bone mass and biomechanics. Preclinical evidence suggests a beneficial effect of Janus Kinase inhibition (JAKi) on bone properties, but clinical data are scarce to date. In this study we evaluated the effect of JAKi through baricitinib (BARI) on (i) volumetric bone mineral density (vBMD), bone microstructure, biomechanics, erosion repair and (ii) synovial inflammation in RA patients. Prospective, single-arm, interventional, open-label, single-center phase 4 study in RA patients with pathological bone status and clinical indication of JAKi (BARE BONE trial). Participants received BARI (4mg/day) over 52 weeks. To assess bone properties and synovial inflammation, high-resolution CT scans and Magnetic resonance imaging (MRI) were performed at baseline (BL), at week 24 and 52. Clinical response and safety was monitored. Thirty RA patients were included. BARI significantly improved disease activity (DAS28-ESR: 4.82±0.90 to 2.71±0.83) and synovial inflammation (RAMRIS synovitis score: 5.3 (4.2) to 2.7 (3.5)). We observed a significant improvement in trabecular vBMD with a mean change of 6.11 mgHA/mm3 (95%CI 0.01 to 12.26). Biomechanical properties also improved with mean change from baseline in estimated stiffness of 2.28 kN/mm (95% CI 0.30 to 4.25) and estimated failure load of 98.8 Newtons (95%CI 15.9 to 181.7). The number and size of erosions in the metacarpal joints remained stable. No new safety signals with baricitinib treatment were observed. Bone of RA patients improves with BARI therapy as shown by an increase in trabecular bone mass and an improvement of biomechanical properties.

On the Effects of Different trans and cis Populations in Azobenzene Liquid Crystal Elastomers: A Monte Carlo Investigation.

We investigate main-chain liquid crystal elastomers (LCEs) formed by photoresponsive azobenzene units with different populations of trans and cis conformers (from fully trans to fully cis). We study their macroscopic properties as well as their molecular organization using extensive Monte Carlo simulations of a simple coarse-grained model where the trans and cis conformers are represented by soft-core biaxial Gay-Berne particles with size and interaction energy parameters obtained by fitting a bare bone azobenzene moiety represented at atomistic level. We find that increasing the fraction of cis conformers, as could be obtained by near-UV irradiation, shifts the nematic-isotropic transition to a lower temperature, consistently with experiment, while generating internal stress in a clamped sample. An analysis of pair distributions shows that the immediate surroundings of a bent cis molecule are slightly less dense and more orientationally disordered in comparison with that of a trans conformer. Comparing nematic and smectic LCEs, actuation in the smectic phase proved less effective, disrupting the smectic layers to some extent but preserving orientational order of the azobenzene moieties.

Mucosal flaps prevent neo-osteogenesis after frontal drill-out procedures: A computer-assisted study.

Although several mucosal flap techniques have been reported to improve the outcomes in Draf IIb and Draf III procedures, there is scant knowledge on frontal ostium neo-osteogenesis after reconstruction with mucosa flap. This study evaluates the potential benefits of mucosa flaps on frontal ostium neo-osteogenesis after frontal sinus drill-out procedures. Forty-three patients who underwent extended Draf IIb and Draf III were enrolled. Among them, 20 patients had frontal neo-ostium (FNO) reconstructed by mucosal flap (group A), and 23 patients did not have neo-ostium reconstruction (group B). The cross-sectional area of FNO, frontonasal bone, and the amount of frontal neo-osteogenesis (FNOG) were measured with OsiriX®. In addition, the Global Osteitis Scoring Scale (GOSS), Lund-Mackay score (LMS), and Lund-Kennedy score (LKS) were also evaluated. At one year postoperatively, the remaining neo-ostium area was significantly larger in group A (p = .001), and group A had significantly less FNOG (p < .05). The month 12 postoperative GOSS score was significantly decreased in group A. In contrast, it slightly increased in group B. Both the average LKS and LMS were significantly reduced in groups A and B at month 12 postoperatively. Still, the average LKS of group A significantly decreased than that of group B at month 12 postoperatively. Coverage of the bare frontal bone with the mucosal flap could prevent excessive neo-osteogenesis and keep the neo-ostium open widely. 2b.

Use of a Synthetic Dermal Matrix for Reconstruction of 55 Patients with Nongraftable Wounds and Management of Complications.

The aim of this study was to investigate the role of a completely synthetic dermal matrix (Biodegradable Temporizing Matrix [BTM]) for staged reconstruction of complex wounds. The authors defined complex wounds as wounds not amenable to reconstruction with skin grafting alone due to an inherent avascularity such as the presence of bare bone, tendinous, or neural structures. A retrospective review of a prospectively maintained database of complex wounds as defined above was carried out. Fifty-five patients were identified who underwent staged BTM and autologous skin graft reconstruction for complex wounds affecting a wide variety of patient demographics, treatment indications, and body sites. Wound etiology included burn injury and nonburn-related trauma such as degloving injury or infective complications. Caveats relating to the successful application of staged dermal matrix reconstruction, techniques, tips, prevention, and management of complications are outlined. This large consecutive case series demonstrates the integral role dermal substitutes play in providing biological wound cover for avascular wound beds which may otherwise require complex distant flap or free tissue transfer for reconstruction. Staged synthetic dermal matrix reconstruction has proven robustness in the face of unfavorable wounds compared with nonsynthetic dermal matrices, physiologically covering avascular structures, allowing for early graft take, expediting rehabilitation, and mobilization with good scar cosmesis and limited contracture formation.

Correlation analysis of femoral tunnel angle and medial collateral ligament injury in posterior cruciate ligament single-bundle reconstruction

To investigate whether the outlet of the femoral tunnel will cause iatrogenic injury to the medial collateral ligament (MCL) during posterior cruciate ligament reconstruction (PCLR) and estimate the safe angle of femoral tunnel placement. Thirteen formaldehyde-soaked human knee joint specimens were used, 8 from men and 5 from women; the donors' age ranged from 49 to 71 years, with an average of 61 years. First, the medial part of the femur was carefully dissected to clearly expose the region of the MCL course and attachment on the femoral medial aspect and to outline the anterior margin of the region with a marked line. The marked line divided the medial femoral condyle into an area with an MCL course and a bare bone area which is regarded relatively safe for no MCL course. Then, the posterior cruciate ligament (PCL) was cut to identify the femoral attachment of the PCL. After the knee joint was fixed at a 120° flexion angle, the process of femoral tunnel preparation for the PCL single-bundle reconstruction was simulated. The inside-out technique was used to drill the femoral tunnel from the PCL femoral footprint inside the knee joint with an orientation to exit the medial condyle of the femur, and the combination angle of the two planes, the axial plane and the coronal plane, was adapted to the process of drilling femoral tunnels at different orientations. The following 15 angle combinations were used in the study: 0°/30°, 0°/45°, 0°/60°, 15°/30°, 15°/45°, 15°/60°, 30°/30°, 30°/45°, 30°/60°, 45°/30°, 45°/45°, 45°/60°, 60°/30°, 60°/45°, 60°/60° (axial/coronal). The positional relationship between the femoral tunnel outlet on the femoral medial condyle and the marked line was used to verify whether the tunnel drilling angle was a risk factor for MCL injury or not, and whether the shortest distance between the femoral exit center and the marked line was affected by the various angle combinations. Furthermore, the safe orientation of the femoral tunnel placement would estimated. When creating the femoral tunnel for PCLR, there was a risk of damage to the MCL caused by the tunnel outlet, and the incidence was from 0 to 100%; when the drilling angle of the axial plane was 0° and 15°, the incidence of MCL damage was from 69.23% to 100%. There was a significant difference in the incidence of MCL damage among femoral tunnels of 15 angle combinations ( χ 2=148.195, P<0.001). By comparison between groups, it was found that when drilling femoral tunnels at 5 combinations of 45°/45°, 45°/60°, 60°/30°, 60°/45°, and 60°/60° (axial/coronal), the shortest distances between the tunnel exit and the marked line were significantly different than 0°/45°, 0°/60°, 15°/45°, 15°/60°, and 30°/30° (axial/coronal) ( P<0.05). Additionally, after comparing the median of the shortest distance with other groups, the outlets generated by these 5 angles were farther from the marked line and the posterior MCL. The creation of the femoral tunnel in PCLR can cause iatrogenic MCL injury, and the risk is affected by the tunnel angle. To reduce the risk of iatrogenic injury, angle combinations of 45°/45°, 45°/60°, 60°/30°, 60°/45°, and 60°/60° (axial/coronal) are recommended for preparing the femoral tunnel in PCLR.

Reverse sural flap for anteromedial ankle and dorsal foot soft-tissue defect following an injury: A case report

Foot and ankle soft-tissue defects constitute a real challenge to reconstructive surgeons because of restricted local soft tissue availability. We report a 28 years old male with a significant soft-tissue defect on the left anteromedial ankle and dorsal foot. A 28 years old male with soft-tissue necrosis on the left anteromedial ankle and dorsal foot, as well as second - fourth metatarsal fractures with gangrene of the first - third phalanx, presented to our hospital 14 days after a traffic accident. He underwent debridement and amputation of the gangrenous fingers. In the second operation, a pin fixation of the metatarsal fractures and the reverse sural flap was performed. The donor site was covered with a split-thickness skin graft. The wounds began to improve significantly on the tenth day after the surgery, and his wounds were gone entirely in the third week. The pins were removed eight weeks after the surgery with the fractures healed. Skin grafts are easy and quick to cover open wounds but cannot be applied to cover bare tendons or bone. Local flaps of the distal third of the lower extremity have a limited range of motion and arc of rotation. Free flaps are an acceptable but complex reconstructive surgery that requires long operative time, special instruments, and microsurgical training and are expensive. The reverse sural flap was considered feasible in reconstructing patients with soft-tissue defects of the distal leg, ankle, and foot, especially in resource constraint scenarios.

Influence of graphene oxide and carbon nanotubes on physicochemical properties of bone cements

The influences of graphene oxide (GO) and carboxyl functionalized multi-wall carbon nanotubes (f-MWCNTs) on mechanical and biological performances bone cements used as the bone substitute are investigated. The bioresorbable and bioceramics were prepared of calcium sulfate diydrate, tetra calcium phosphate and dicalcium phosphate dihydrate is fabricated by a solid-state high temperature process. Then the bioceramic is mixed with carboxymethyl cellulose, gelatin and nanocarbons. The addition of 0.5 wt% f-MWCNT and 1 wt% GO is found to increase the compressive strength of the resultant nanocomposite by %50 and %55, respectively, in comparison to that of the bare bone cement. 1 wt% GO incorporated bone substitutes had the optimum mechanical properties which had compressive modulus and compressive strength of 1.9 ± 0.3 and 35.8 ± 0.5 MPa, respectively. Moreover, GO is found to be more effective than f-MWCNT in stabilizing pH. The degradation rate of the bone cement is stabilized through GO incorporation but increased by incorporating f-MWCNT. Bone substitutes up to 1 wt% nanocarbons exhibit biocompatibility and MC3T3-E1 pre-osteoblasts were mineralized after 14 days of cell culture. The results demonstrate that the physicochemical properties of the nanocomposites are significantly affected by the concentration and surface properties of nanocarbons.

ReLU-FCM trained by quasi-oppositional bare bone imperialist competition algorithm for predicting employment rate.

Fuzzy cognitive maps (FCMs) are a powerful tool for system modeling, which can be used for static and dynamic analysis. However, traditional FCMs are usually learned by gradient-based methods, and the adopted sigmoid nonlinear activation function frequently causes gradient saturation. These two shortcomings set a limit on the modeling accuracy. To overcome those problems, we propose in this paper a new FCM with two improvements. First, the rectified linear unit (ReLu) activation function is adopted to replace the sigmoid function. Second, a newly proposed quasi-oppositional bare bone imperialist competition algorithm (QBBICA) is used to learn the FCM. The improved FCM is used to predict the employment rate of graduates from Liren College, Yanshan University. Experimental results show that the improved FCM is effective in employment rate prediction.

Target Filter Tracking Algorithm Based on IABBSCA-IMM

Aiming at the problem that the probability transition matrix is set by prior information and the filtering parameters are fixed in the traditional interactive multimodel (IMM) algorithm, which leads to the model probability lag in the switching process and the low filtering and tracking accuracy, an interactive multimodel filter tracking (IABBSCA-IMM) algorithm with improved parameter adaptive and bare bone sine cosine optimization is proposed. First, the Markov probability transition matrix is dynamically adjusted and limited conditions are added through the parameter adaptation method; then, the filtering parameters Q and R are optimized by the bare bones sine cosine algorithm (BBSCA); finally, three motion models of CV (uniform velocity motion), CA (uniform acceleration motion), and CT (uniform velocity turning motion) are used to conduct filtering and tracking experiments on the target. The simulation results show that, compared with the IMM algorithm, the AMP-IMM algorithm, the IASCA-IMM algorithm, and the IABBSCA-IMM algorithm proposed in this study have the smallest position and velocity root mean square error (RMSE) in the X and Y directions, and the accuracy is better.

Retinoblastoma: A New Technique for Orbital Exenteration

Purpose and Design: Having to remove an invasive Retinoblastoma one aims to avoid an unstable orbital cover after removing the periosteum and when an usual skin graft procedure might not assure the stable support of an ocular prostheses. Methods: Based on de-doubling the lids (skin, tarsus and conjunctiva) as well as moderately freeing the peri-orbital tissues, followed by suturing together the conjunctiva of both lids, Results: purpose and design obtained. Conclusion: A reliable and stable orbital skin cover to support any prostheses Extraperiosteal orbital contents removal is considered essential to avoid a new recurrence when orbital exenteration is required. A new technique for orbital exenteration is described aiming to avoid one unstable free graft on the bare orbital bone that does not usually support the required postoperative aesthetic orbital prostheses.

Research on the visual image-based complexity perception method of autonomous navigation scenes for unmanned surface vehicles

To solve the long-tail problem and improve the testing efficiency for autonomous navigation systems of unmanned surface vehicles (USVs), a visual image-based navigation scene complexity perception method is proposed. In this paper, we intend to accurately construct a mathematical model between navigation scene complexity and visual features from the analysis and processing of image textures. First, the typical complex elements are summarized, and the navigation scenes are divided into four levels according to whether they contain these typical elements. Second, the textural features are extracted using the gray level cogeneration matrix (GLCM) and Tamura coarseness, which are applied to construct the feature vectors of the navigation scenes. Furthermore, a novel paired bare bone particle swarm clustering (PBBPSC) method is proposed to classify the levels of complexity, and the exact value of the navigation scene complexity is calculated using the clustering result and an interval mapping method. By comparing different methods on the classical and self-collected datasets, the experimental results show that our proposed complexity perception method can not only better describe the level of complexity of navigation scenes but also obtain more accurate complexity values.

A hybrid registration method using the mandibular bone surface for electromagnetic navigation in mandibular surgery.

To utilize navigated mandibular (reconstructive) surgery, accurate registration of the preoperative CT scan with the actual patient in the operating room (OR) is required. In this phantom study, the feasibility of a noninvasive hybrid registration method is assessed. This method consists of a point registration with anatomic landmarks for initialization and a surface registration using the bare mandibular bone surface for optimization. Three mandible phantoms with reference notches on two osteotomy planes were 3D printed. An electromagnetic tracking system in combination with 3D Slicer software was used for navigation. Different configurations, i.e., different surface point areas and number and configuration of surface points, were tested with a dentate phantom (A) in a metal-free environment. To simulate the intraoperative environment and different anatomies, the registration procedure was also performed with an OR bed using the dentate phantom and two (partially) edentulous phantoms with atypical anatomy (B and C). The accuracy of the registration was calculated using the notches on the osteotomy planes and was expressed as the target registration error (TRE). TRE values of less than 2.0mm were considered as clinically acceptable. In all experiments, the mean TRE was less than 2.0mm. No differences were found using different surface point areas or number or configurations of surface points. Registration accuracy in the simulated intraoperative setting was-mean (SD)-0.96 (0.22), 0.93 (0.26), and 1.50 (0.28) mm for phantom A, phantom B, and phantom C. Hybrid registration is a noninvasive method that requires only a small area of the bare mandibular bone surface to obtain high accuracy in phantom setting. Future studies should test this method in clinical setting during actual surgery.

350 Cross Over Septal Flap Technique for Choanal Atresia Surgery: Two Centre Series with Outcomes

Abstract Introduction Choanal atresia (CA) is a congenital obstruction of the posterior nasal aperture due to nasal cavity canalisation failure. Endoscopic endonasal surgery has led to successful CA repair and fewer complications compared to open surgery. We describe our surgical technique that uses septal mucosal flaps without need for stenting or subsequent intubation. Method A multicentre retrospective review of patients who underwent surgery using the cross over septal technique. Patient demographics and outcomes were recorded. Flap design: bilateral vertical septal mucosa incisions are performed on either side of the posterior third of the septum to form two mucoperiosteal flaps. The posterior vomer and atretic plates are removed. One flap is pedicled superiorly and rotated over the bare sphenoid rostral bone. The contralateral flap is pedicled inferiorly and rotated to cover exposed bone of nasal cavity floor. Lateral nasal wall mucosal integrity is maintained. This technique is used both for unilateral and bilateral atresia. Results Twelve patients from 2013 to 2020 were included. Age range was 0.07-50 years, male to female ratio of 1:5. Ten patients had unilateral CA, two had bilateral. Nine had bony CA, the remainder mixed. 5 patients (mean age 2.8 years) underwent second-look endoscopy under sedation an average 36 days following primary surgery. Conclusions The cross over technique for CA has low morbidity and 100% success in our multicentre series. Use of mucoperiosteal flaps to cover the exposed bone, removal of vomer and minimal instrumentation to the lateral nasal wall are the best ways to avoid postoperative stenosis.