Through the hierarchical system, the ankle joint is the most vulnerable to subject measurement error. Leg length has the greatest effect on all joints as a percentage of measurement error. When compared to the errors previously found through inter-laboratory measurements, the impact of subject measurements is minimal, and researchers should rather focus on marker placement. Finally, we showed that code modifications can be performed to include improved hip, knee, and ankle joint centre estimations suggested in the existing literature. The pyCGM code is provided in open source format and available at https://github.com/cadop/pyCGM.The conventional gait model (CGM) is a widely used biomechanical model which has been validated over many years. The CGM relies on retro-reflective markers placed along anatomical landmarks, a static calibration pose, and subject measurements as inputs for joint angle calculations. While past literature has shown the possible errors caused by improper marker placement, studies on the effects of inaccurate subject measurements are lacking. Moreover, as many laboratories rely on the commercial version of the CGM, released as the Plug-in Gait , integrating improvements into the CGM code is not easily accomplished. This paper introduces a Python implementation for the CGM, referred to as pyCGM, which is an open-source, easily modifiable, cross platform, and high performance computational implementation. The aims of pyCGM are to (1) reproduce joint kinematic outputs from the Vicon CGM and (2) be implemented in a parallel approach to allow integration on a high performance computer. The aims of this paper are to (1) demonstrate that pyCGM can systematically and efficiently examine the effect of subject measurements on joint angles and (2) be updated to include new calculation methods suggested in the literature. The results show that the calculated joint angles from pyCGM agree with Vicon CGM outputs, with a maximum lower body joint angle difference of less than 10 Human locomotion has been a central theme of biomechanics research for centuries  As a direct kinematic and hierarchal method, a proximal origin’s frame definition influences more distal segments , 14. ForPrevious work has shown that subject measurement error can propagate to joint kinematic quantities . In the Computational power has been continuously increasing for decades . ThroughIn the case of kinematic analysis, recording motions at high sampling rates over long periods of time can result in a significant amount of data to be processed, suggesting an important use-case for HPC and parallelization solutions. For example, a study on the effect of high heels on gait, in which 10 subjects walked at 5 cadences with 3 different heel heights, resulted a total of 150 trials to be analyzed . For anaCurrently, open source biomechanics tools such as OpenSim  and BTK The basis of this paper is an open source Python script for the CGM, referred to as pyCGM . First, The pyCGM code can be run through either a command line or by directly calling the functions. Data can be passed to the joint angle calculations directly or by functions loading files which store data as a python dictionary. The process for calculating a dynamic trial is detailed in Files are loaded or data is created in section B, with an argument passing the number of cores to use for calculations. Subject measurements can be loaded through a.VSK file (Vicon Skeleton), which may contain either subject measurements or subject measurements and corresponding static calibration information. Joint angles of a static trial can be obtained by using the same file for the dynamic trial. In section C, the static offsets are calculated when this information is missing. Static offsets rely on the computation of the CGM for each frame of the static trial and averaging the results at the end. Once the subject measurements and offsets are known, the frames of the dynamic trial are divided evenly among the number of cores defined and the data is distributed.kw. As such, this joint center is directly dependent on the subject measurement. Implementation of this formula in pyCGM can be seen in the sample code shown in One of the key aspects to the CGM is estimating a joint center using subject measurements and virtual markers. While this method has been explained for the hip in , the autWhile pyCGM has followed the methods defined in the literature, one significant difference is implemented in the calculation of joint angles. While Kadaba  defined The CGM has three main parts: a static trial, dynamic trial, and subject measurements. While a static calibration is required, the calculated values act as constants in the calculations. This independence is important for the parallelization efficiency and scalability of the system. The process requiring an average or other calculation over all frames can be seen in n increase in frames can be mitigated with an n increase in processors, with an overhead consistent with the communication algorithm.While both While access to HPC is increasing, the use of multi-core desktop computers is nearly ubiquitous, and as such, methods for parallelizing the CGM are applicable on these platforms as well. For simple cross-platform testing, the python multiprocessing module was used for parallel processing of dynamic trials . The oriSimilar to the method for desktop parallelization, a single dynamic trial can be distributed among multiple nodes on an HPC. In this method, an initial processor (rank 0) is responsible for loading and distributing data . Rank 0 Calculation of multiple trials or, in the case of this research, multiple iterations of a single dynamic trial can be done by either passing data using MPI or by relying on the IO luster system. In For analyzing the computational performance of a parallel system on large motion capture data, a file containing 59,993 frames was recorded at 100 Hz in Vicon Nexus  using the 35 marker set. This trial is used purely as a method for checking parallelization efficiency and space complexity, and not used for the subject measurement analysis.To analyze the effect of subject measurement on joint kinematics, the sample data distributed on Vicon Nexus systems was used for its wide availability and unbiased marker positioning. This dataset includes, among others, a static trial with 275 frames, a range of motion (ROM) trial with 2,076 frames, and complete subject measurements stored in a.VSK file, all three of which are used in this research. The trials contain two additional markers on each arm, UPA and FRM; however, these markers are not used in the calculations. The ROM file was selected for analysis, as it allows for a thorough understanding of the influence of subject measurements throughout different motions that may be calculated by the CGM. For example, hip flexion that occurs during a sitting motion would not appear during a typical gait cycle. While most of the data was complete, the squat and bending motion of the ROM had occluded markers which were gap-filled within the Vicon Nexus software. The ROM file data was categorized into the individual movements for analysis. The data displayed in the Results includes a squat motion, front leg raise, and a side leg raise.Saving the results is done with the numpy compressed format NPZ. The advantage of the NPZ format over C3D format is the fast data IO and extremely simple programming methods. Keywords are used to determine which of the joint angles are to be saved in the file to reduce unnecessary time and space in the saving process. In the case of this research, the joint angles for only the lower body are saved in the NPZ format. Table 1n number of possible subject measurement values to the power of r number of measurements, denoted by nr. Sampling of the values was done in three steps.There are 6 subject measurements related to distance that affect the joint angle calculations of the lower body: ASIS to trochanter distance (AT), inter ASIS distance (IAD), leg length (LL), knee width (KW), ankle width (AW), and sole delta. While LL, KW, and AW are required inputs for the CGM, the AT and IAD can either be input manually or calculated automatically from marker positions, and sole delta can be set to 0. As the former three are required in all situations, the current analysis is focused on these parameters. To demonstrate the HPC performance of numerous dynamic trials, various permutations of these 5 measurements are calculated. Permutations with repetitions are calculated by the 3 combinations.Intervals of 0.5 from -5 to 5 are generated for LL, KW, and AW, resulting in 213 combinations.A large range from +/- 0 to 80 for LL, KW, and AW with increments doubling for 93 combinations involving AT and IAD were used for the computational performance experiment, but not used for data analysis.An additional 9Excluding duplicates from each range, such as all measurements being 0.The total number of these combinations results in 10,685 unique dynamic trials being calculated. Both the analysis and computational times for calculating these files are detailed in the Results section.Experiments were done on two platforms using Python 2.7. First, the python multiprocessing module was implemented on a laptop running Windows 7 64-bit with a quad core Intel i7-4700MQ processor at 2.4 GHZ, and 16 GB of RAM. This laptop was also used for the timing experiments to compare against Vicon Nexus 1.8. For the HPC experiment a Cray XC30 supercomputer was used (Referred to as Darter). Each node consists of two 2.6GHz Intel 8-core XEON E5-2600 CPUs and 32GB of RAM, with hyper-threading disabled.-5 degrees.The dynamic ROM trial joint kinematic outputs from pyCGM and Vicon’s CGM implentation were compared . The resThe first experiment comparing the computational performance of the pyCGM against Vicon’s CGM implementation in Nexus v1.8 is on a consumer-based four-core laptop. As Nexus calculates both kinetics and kinematics, it is not possible to compare exact computational speed differences against pyCGM. However, the results give a frame of reference for practical computation times on any multi-core consumer computer when kinetic calculations are not required. Scalability on the HPC of the multiple core approach to the CGM can be seen in To calculate multiple variations of a dynamic trial, an experiment with both 800 and 1,600 cores was conducted using the method explained in Three key aspects of the relationship between subject measurement error and joint angle error were analyzed. First, the maximum joint angle error of a +/- 2.5% and +/- 5% error in leg length (LL), +/- 5% and +/- 10% in knee width (KW), and +/- 10% and +/- 20% in ankle width (AW) measurements during various motions from the ROM trial was found. The subject measurement percentage error corresponds to the errors found from inter-laboratory testing in . Second,As the CGM is based on a hierarchy of relative joints, the subject measurements influence the joint angles in this hierarchy. As such, the modification of LL affects all joints, while the modification of AW will only have a direct effect on the ankle frame, with an indirect effect of the knee kinematics. For both squat and ankle rotation motions extracted from the ROM file, The irregular effect of subject measurements on joint angles is due in part to both the calculation method  and the Finally, by analyzing the 9,965 combinations of LL, KW, and AW, the most affected joint and axis can be found. Through the hierarchal system, the largest angle error of all combinations occurrs most often in the ankle joint . The fraThe large difference in the most common joint axis angles between right and left sides shows that the initial frame orientation and definition greatly influences the resulting errors from subject measurements.The code style of pyCGM was developed to be straight forward to understand and modify. Beyond the utility of being cross platform without modification there are no pointers or objects used in the calculation. Subject measurements are stored in a dictionary and are easily referred to throughout the code.Improvement of the original CGM hip joint center location estimations  were impIt is also possible to determine the knee joint center locations using the method proposed by Stief . In the This paper presents experimental data for high performance computing of the CGM used for calculating joint kinematics. It demonstrates three methods; specifically, the use of HPC for a single large file of motion capture data by distributing frames to be calculated on separate cores and across nodes, and the distribution of frames across cores on a consumer grade desktop, was investigated. Second, large calculations were performed on a single dataset to derive valuable information about the model, such as the case of subject measurement errors, through the distribution of data across cores.While many alternatives and modified versions of the CGM exist, this paper focuses on Vicon’s CGM implementation via the plug-in-gait modeler distributed in Vicon Nexus software  due to tThe choice to implement the CGM in Python was made primarily due to the portability between operating systems and the wide acceptance of Python for scripting purposes in the scientific community . The intAs much of the data reported in the literature is focused on the lower body (due to a focus on gait), this paper focused on the lower body. While the upper body has been developed in pyCGM and is included in the computational time, the lack of data relating to marker placement and skin deformation of the upper body makes it difficult to compare the significance of subject measurement errors.There was a strong agreement between pyCGM and Vicon CGM joint kinematic outputs, confirming a correct implementation of the CGM. Small differences observed may be due to numerical implementation differences or rounding differences. Importantly, in the Vicon CGM, the method used to compute the knee and ankle joint center is unclear; however, here, an exact formulation based on the Rodrigues rotation formula  is preseThe non-optimized Direct Kinematic (DK) method allows for a frame-by-frame calculation for joint kinematics and, as such, provides an opportunity for easy HPC implementation to assist in the kinematic processing. Similarly, the portability and modularity provided by pyCGM allows researchers to quickly modify the parameters of the model and distribute workloads of either frame-by-frame or trial-to-trial calculations to an HPC. These calculation times are dramatically improved by moving from a classical desktop setup to an HPC, as detailed in the results section.As a stand-alone compiled program, comparison against Nexus also demonstrates the real speed benefit of parallelization as the interpreted python code is significantly faster than the compiled code of Nexus. At the same time, under utilizing the parallelized methods by reducing the number of cores used has an adverse effect on computation time. While the HPC is orders of magnitude faster than Nexus when using multiple nodes, the use of only 1 core shows significantly slower processing times. This is attributed to the lower clock speed of processors containing large numbers of cores.However, challenges exist for the type of large databases of motion capture data that can fully take advantage of HPC. The first is the need to improve the ability to track people in an efficient way. While devices such as the Microsoft Kinect may allow for cheaper 3D reconstructions, a more relevant advancement would be the replacement of reflective markers and infrared cameras with a regular RGB camera with tracking markers, such as QR tags, that can be easily implemented on-site in a variety of cases while taking advantage of the research already done on joint landmark kinematic calculations. In the laboratory, more robust gap-filling and auto-labeling technology using the current motion capture systems would also greatly improve the efficiency and bring the use of HPC to a more common audience.The primary, or axis of most importance during an analysis, such as knee flexion during a squat motion, is central to understanding the importance of subject measurements. As seen in the experimental data, during a squat motion the flexion axis in both left and right knee axis were almost never the source of the largest error. As such, while subject measurements have an effect on joint angles, hip and knee flexion are the least affected and may still provide the most valid results. The percentages of error displayed in While accurate subject measurements are required for the CGM, the importance of these measurements should be considered within the context of other possible sources of angle error. In , 10 mm oPast work has shown that rather than completely new models, modifications to existing models provide familiarity and improved accuracy. In , the kneThe numerous studies for validating the results during gait, the wide usage, and the deep understanding of the model  remain iSince the creation of the original CGM, new methods for computing joint kinematics have been introduced, with the most relevant works modifying the CGM to be used with kinematic fitting and optimizations. C-motion Visual 3D offers a version of the CGM that uses optimization methods through inverse kinematics . LikewisBeyond the work presented here, there is a need for new computational models to take into account spatial and time complexity, as these are directly related to the impact and implementation possibilities throughout the biomedical industry and other fields. Real-time algorithms for single subject analysis have been developed, which creates implications for clinician-patient interaction . When coApplications for computation of large databases of motion capture data extend from biomechanics and robotics to other, less obviously related fields, such as architecture. In architecture, understanding human movement and movement abilities is important for design and necessary in order to move from prescriptive to performative design criteria . In geneFinally, further work involving subject measurements in the CGM can shed light on how significant other measurements beyond leg length, knee width, and ankle width are. This may also lead to the ability for subject measurements to be derived directly from marker locations during the static calibration, which would remove the need for storing patient specific data while maintaining a reasonable margin of error.S1 FigFor the knee joint center, the calculation is from the thigh marker (a), hip joint center (b), and knee marker (c). The intent is to find the plane in which all markers lay, with half the knee width (kw) being used in the calculation.(TIF)Click here for additional data file.S2 FigThe python code provides comparison between the mathematics and code that is easy to read and understand. The function receives three marker positions and half of the knee width measurement. The return value is the cartesian location of the calculated joint center. Ease of understanding the code is an important aspect of pyCGM, and as such, the steps are divided clearly so that users can both understand and modify the code to suit their needs.(TIF)Click here for additional data file.S3 FigMotion capture data of a sitting motion in which the Knee bends to 90 degrees. While this function was intended for use in gaits that would not commonly have a 90 degree flexion, the widespread use of the CGM includes researchers using it for purposes beyond typical gait.(TIF)Click here for additional data file.S1 Equation(PDF)Click here for additional data file.S1 TableThe Sum column is the sum of the times required for each step in the calculation process. The Total column is the recorded start to finish time, with the difference shown in the last column. This difference includes communication time between cores and nodes, as can be seen from the increased difference when the calculation moved from 1 node to 2 nodes.(PDF)Click here for additional data file.S2 TableThe average, maximum, and minimum times for each core to complete the calculations are shown. Additionally, the longest time for any core to complete all calculations is shown. Loading data was all done on the initial core. Saving the results, dynamic trial calculation, and static trial calculation times are from every core. The sum of these calculations and the total time recorded from the first node differ mostly due to data transfer between nodes.(PDF)Click here for additional data file.S1 File(ZIP)Click here for additional data file.S2 File(XLSX)Click here for additional data file.


The Journal of Neuroscience, The cochlear implant (CI) can restore a sense of hearing to deaf people. Although it works well in quiet situations, most CI users still struggle to follow conversations in noisy environments and perceive music. One challenge in CI stimulation is that the brain must resolve and interpret the signal to generate meaningful and goal-oriented hearing. How efficient this process is and how the underlying neuronal circuits respond, or fail to respond, to such input compared with normally transmitted sound is essentially unknown. Understanding these central auditory mechanisms is crucial for the further development of CIs. In a recent study published in Sound travels from its source to the ear, and further on eventually to the brain, through a chain of biological mechanisms that convert vibrations in the air into nerve impulses. In deaf people, the link between sensory hair cells and the auditory nerve in the cochlear is often broken , and the auditory input therefore never reaches the brain. Cochlear implants (CIs) bypass this missing link by directly stimulating the auditory nerve. To date, this approach has restored hearing sensation to >300,000 severely and profoundly deaf people.The Journal of Neuroscience, Present-day design of CIs is based on a bottom-up approach in which the goal is to reproduce normal patterns of neural activity at the auditory periphery. In a recent study published in Callithrix jacchus) is a valuable model of how the human brain processes auditory information: it is a highly vocal, communicative, and social nonhuman primate, and its hearing range and organization of the auditory cortex (AC) are similar to those of humans  and characterized the acoustic features and selectivity of A1 neurons to CI stimulation A, B.First, the authors investigated how efficient a CI is in transmitting information to the AC compared with acoustic stimuli. They recorded 1408 single neurons from the AC and classified them as either acoustic-driven (the neuron responded to tones or bandpass noise) or CI-driven (the neuron responded to electric stimulation of the implant). It is important to highlight that acoustic and CI stimulation are two different quantities , and theOne possible explanation is related to the differences between contralateral and ipsilateral stimulation, with contralateral stimulation typically being much more effective and precise . BecauseA second possible explanation is that the CI has been activated only with a standard stimulation protocol and not a test battery of additional CI pulse variables , which potentially could engage neurons in a more similar way . A third possibility is lack of cortical adaptation to CI stimulation, discussed below.The response of a neuron to pure tones of varying frequency and level, known as its frequency response area (FRA), is a fundamental receptive field measure in the auditory system . NeuronsWhy do neurons with small and selective receptive fields not respond to CI stimulation? Are they simply not activated, or are they suppressed? It is well established that the interaction between inhibition and excitation plays a crucial role in shaping and refining the brain’s representation of sensory stimulus attributes . NonrespThese results provide valuable insight into how CI only partially engages the brain at the level of single neurons. Below, I place the findings into perspective and propose future experiments.The finding that CI-mediated inhibition overwhelms excitation leaves many questions unanswered. Is this misbalance related to the strength of—or the timing between—excitation and inhibition? Which cell types and circuits are involved? Will less inhibition improve efficiency and selectivity of CI stimulation, and eventually improve perception of CI input?To address the first question, one could look at the temporal dynamics of O- and V-unit population responses on CI stimulation as in In the AC, synaptic inhibition is known to be involved in shaping receptive fields, controlling gain, and promoting temporal precision . The oveHearing with a CI takes time and practice, because the auditory system must adapt to reinterpret the new auditory input as meaningful sound . TherefoThe authors found that neurons sharply tuned to frequency and sound level (O-shaped FRAs) are poorly activated by CI stimulation, but whether this is a result of (1) cortical CI-evoked response or (2) lack of plastic changes is difficult to tell. In favor of the first statement, many CI users face challenges hearing in dynamic and noisy environments, which is partially due to limited dynamic range  and a poor ability to discriminate steps in amplitude of a sound . As thesOn the other hand, supporting the second statement, Altogether,


In sports motion analysis, observation is a prerequisite for understanding the quality of motions. This paper introduces a novel approach to detect and segment sports motions using a wearable sensor for supporting systematic observation. The main goal is, for convenient analysis, to automatically provide motion data, which are temporally classified according to the phase definition. For explicit segmentation, a motion model is defined as a sequence of sub-motions with boundary states. A sequence classifier based on deep neural networks is designed to detect sports motions from continuous sensor inputs. The evaluation on two types of motions  verifies that the proposed method is successful for the accurate detection and segmentation of sports motions. By developing a sports motion analysis system using the motion model and the sequence classifier, we show that the proposed method is useful for observation of sports motions by automatically providing relevant motion data for analysis. Analyzing quality of motion is essential for evaluating the performance of athlete’s movements in sports . The anaTechnologies have already been adopted for helping observation of sports motions . Using vVideo-based gesture and action recognition has always been of great concern for many researchers. With the successes in image classification based on deep learning, deep neural networks also seem to be promising for gesture and action recognition as well. Ji, et al.  proposedDepth cameras can provide useful information about human movements represented in 3D space . Zhang eWearable inertial sensors are suitable for recognition of actions  and for In this paper, we propose a novel approach to detect and segment sports motions using a wearable sensor. Our main concern is to support observation of sports motions in analysis tasks by automatically classifying states (or phases) of the recognized motions. The automatic classification is processed on-line from continuous sensor inputs, thus users can get feedback immediately. For explicit segmentation of a motion into phases, a motion model is defined as a sequence of sub-motions with boundary states. A sequence classifier that is based on deep neural networks is designed to detect sports motions from continuous sensor inputs. For evaluation, two types of motions  were collected. The evaluation was carried out with two questions in mind: how well the proposed method detects an occurrence of a motion to be analyzed and how accurately the detected motion is segmented into the pre-defined states. In addition, a sports motion analysis system  based onstart, performing, and end states, respectively.As stated in the introduction, we perceive a sports motion as a sequence of sub-motions or phases. It is similar to state transition models, like left-right models, in HMM-based gesture recognition methods . AlthougThe start and end states imply boundaries of a sub-motion and the performing state is considered as relevant movement. It is assumed that transition between sub-motions is instant so the length of a boundary state is one (each boundary state corresponds to only a single input sample) and the end state of a sub-motion coincides with the start state of the next sub-motion. Consequently, a sports motion undaries . Detection of a motion from continuous sensor inputs is described in a two-step process: (1) motion states corresponding to an input sequence is estimated, and (2) the state pattern of the motion is searched from the sequence of the estimated states.k at the l-th input sample . In theBecause of temporal variances of motions, especially large in sports motions, it is not guaranteed that a whole motion is contained in the input sequence of a fixed length From the accumulated sequence of state probabilities, a motion is detected by searching the pattern of states defined by a motion model. In our implementation, the state pattern (or only boundary states for simplicity) is searched from the end (the most recent state) of the accumulated sequence in reverse direction. The longest common subsequence (LCSS) algorithms  can alsoAs we explicitly defined state boundaries in the motion model, it is straightforward to segment the detected motions. From the accumulated sequence of state probabilities (Equation (6)), temporal indices of boundary states can be found by:To gather motion data for training and evaluation, we used a commercially available wearable sensor . The senAt the same time, two high speed cameras  were recorded for a single performance. As the lengths of the two types of motions were usually shorter than five seconds, recorded data may include irrelevant motions like walking or stepping.A total of 404 soccer kicking motions were recorded with the wearable sensor being attached to the behind of a kicking leg’s ankle b. The moFor two-handed ball throwing, 333 motions were recorded with the sensor on the wrist c. The moThe sequence classifier al RNNs)  are usedal RNNs) . Figure Z-axis (opposite direction of gravity)Acceleration along Magnitude of accelerationMagnitude of angular velocityMagnitude of the first derivative of accelerationMagnitude of the first derivative of angular velocityMagnitude of the second derivative of accelerationMagnitude of the second derivative of angular velocityAngular difference between adjacent acceleration vectorsAngular difference between adjacent angular velocity vectorsAngular difference between adjacent vectors of the first derivative of accelerationAngular difference between adjacent vectors of the first derivative of angular velocityThe input takes a sequence of 100 feature vectors   as an acFrom the datasets, 80% of the recorded motions  were randomly selected for training. Since the input size of the classifier For the cost function, weighted categorical cross-entropy was used:The classification networks for soccer kicking and two-handed ball throwing were trained using Adam optimizer  with a bDetection and segmentation accuracy of the proposed method was evaluated using the trained networks in the previous section. As test sets, 20% from the datasets, excluding training sets, were used for evaluation . Each motion sample from the test sets was separately fed into the detection and segmentation process as if it were an on-line data stream. Only for successfully detected samples, segmentation errors were measured by comparing the temporal indices of boundary states between the estimated state sequences and the manually labeled data.For soccer kicking, 76 out of 80 samples were successfully detected. For two-handed throwing, 62 out of 66 samples were successfully detected. Except the start and end of motions  shown that the proposed method was successful at detecting and segmenting motions to be analyzed. Also, the sports motion analysis system based on the proposed method was proved to be helpful for sports motion analysis through the tests in real-world conditions.For some motion states (mostly the start and end of a whole motion), segmentation errors were relatively larger than the others. By inspecting datasets and labels, we found that it is mainly caused by either the inconsistency of movements (of the same state) or ambiguity in choosing boundaries between movements with little dynamics (slowly changing motion). So, it will be our next goal to find out ways to detect and segment motions robustly, regardless of irregular movements and labeling errors.In addition, there seem to be alternative approaches, although they are from different domains, which can be applied to motion segmentation. For example, attention  is used


Selection of value chain strategies by development practitioners and value chain participants themselves has been restricted to preset types of upgrading. This paper argues for an extension of the range of strategy solutions to value chains. An empirical application identifies successful strategies for honey value chains in Brazil for 2015–2020. Strategy and performance indicators were selected using the value chain Structure-Conduct-Performance (SCP) framework. Experts’ opinion was elicited in a Delphi for business scenarios, and adaptive conjoint analysis was used to identify strategies for increasing production growth and local value-added. This study identifies important strategies beyond upgrading typologies, and finds that important strategies differ by performance goal and scenario. The value chain SCP allows searching for promising strategies towards performance–the “better deal”–in an integrated way. Development organizations have supported value chain interventions to reduce poverty and increase local chain competitiveness , 2. A crIn this context, the strategic notion of upgrading has been influential: looking for rent-rich opportunities that allow firms to add value to their products through shifts in their capabilities, technologies, and targeted markets. Four types of upgrading were originally identified: product, process, functional, and inter-chain : a) prodComplementarily, the importance of territoriality to value chains has been acknowledged by the global production network (GPN) theory, which also gives more emphasis to actors and relationships in global networks , 26. GPNTo avoid limiting the range of strategic value chain alternatives to upgrading typologies only, this paper uses the value chain Structure-Conduct-Performance (SCP) framework, developed specifically to address value chain strategies . This frConsidering the foregoing discussion, the main objective of this paper is to extend of the range of strategy solutions to value chains beyond upgrading typologies. In the empirical application, likely successful strategies for improving the performance of honey value chain streams are identified using the value chain SCP framework. The remainder of this paper is organized as follows. Section 2 justifies and describes the honey value chain streams chosen for empirical application. Section 3 details the methodology anchored on the value chain SCP framework: the construction of scenarios using a Policy Delphi survey and the conception of strategies using Adaptive Conjoint Analysis with experts. The identification of the most important strategies for each scenario is reported in Section 4, and the discussion of the results and policy conclusions follows in Section 5.The empirical application focuses on three honey value chain streams in the Northeast of Brazil, all in main honey producing areas of the country. Brazil is among the top 10 honey exporters in the world in volume . Two of Among the streams, Picos has the largest honey production , and Santana do Cariri the largest honey export volume (just above 1.0 thousand t/year). The producers are usually small, owning on average between 60 and 100 hives each, and beekeeping is a complementary source of income to crops such as corn, cassava, beans, and to a few livestock such as sheep, goats and cattle. The main local processors either sell bulk honey to the United States and Europe, with the help of international traders sitting in these destinations, or fraction honey to sell in the internal market, with the help of dealers in large cities of the country. Supporting market services in the stream include local technical and managerial assistance, and credit providers. The producers, mostly, sell their honey to the processors that offer the higher prices, in a typical market-based relationship. Special long-term agreements may exist among producers and processors when fair trade and organic certifications are in place. A summary of the figures for the selected streams is presented in These streams have been receiving support from governmental and donor agencies since 2007, with the intent to promote local development and provide guidance to improve competitiveness. Qualitative and quantitative evaluations of the strategies deployed by those value chain streams towards improving their performance between 2007 and 2011 have already been carried out , 39. ThoLooking forward, the strategies in this paper were designed to be deployed between 2015 and 2020, aiming at promoting chain competitiveness and local development. Two economic performance indicators were chosen as targets for the streams: production growth of apiculture products and local value-added per unit of production of apiculture products . Production growth represents the stream’s operational performance, its contribution to the stream’s own competitiveness, whereas local value-added represents the stream’s developmental performance, its contribution to local development. The choice of these indicators was based not only on the diversity of goals that the value chain streams have, but also on the familiarity of the experts with the indicators from a previous analysis .A Policy Delphi survey was applied to identify scenarios for the honey business between 2015 and 2020. The use of scenarios is a powerful tool for strategy development , and theA set of six local experts (two per stream) was identified, which consisted of consultants (two), academics (one), service providers (one), and business people (two) who had been involved with the honey business for at least 10 years. They were informed about the purpose of the study: to lay the foundation for the development of successful strategies for their streams in the next years. All the experts were interviewed between November 2013 and January 2014 by phone, email, or in person, using a structured questionnaire.The experts were first reminded about the structural aspects of the honey business during the 2007–2011 period, through categorized structural indicators   was usedA set of 15 experts was identified, consisting of consultants (three), academics (four), service providers (five), and business people (three), who had been involved with the honey business for at least five years in the two Brazilian states (ten from Ceará and five from Piauí) where the value chain streams are located. This set included the six experts interviewed in the Delphi survey. The experts constituted most of the population (15 out of 27) of knowledgeable people with diverse professional origins who were available. The same experts were consulted during a previous study on the contribution of strategies to past performance .A preliminary list  and u(xij) is its contribution. Interaction effects among the selected strategy levels were assumed to be negligible.The conjoint part-worth model  used in u(xij)’s for each expert separately, using Ordinary Least Squares (OLS) regression. The first type consists of so-called self-explicated ratings of attributes and attribute level desirability. The second type consists of so-called graded paired comparisons for combinations of levels from a limited number (two or three) of strategies. The resulting utilities are later calibrated for use in simulations based on likelihood ratings made by each expert [In ACA, two types of data (see Section 3.2.4) are used to estimate the h expert , 49.The experts were first informed about the structural aspects of the honey business for the period 2007–2011 and about the strategies that most influenced performance during this period, obtained from previous studies ; 39. TheData collection took place during individual face-to-face interviews with the experts between September and December 2014, using a dedicated software (ACA Sawtooth Software version 5.1.0). For each scenario, the experts were asked to rate the contribution of the ACA-generated strategy combinations to each performance indicator. The events in each scenario were kept in front of the expert during the ACA process. The procedure was pre-tested with five of the experts to find the best way of acquainting the experts with the ACA task. The individual characteristics of the respondents were not expected to influence their opinion and were therefore not investigated. The size of the sample was also too small to relate the experts’ characteristics to differences in utility estimates.The ACA questionnaire contained four sections for each performance indicator and scenario. In the so-called self-explicated phase of the interview, entailing Sections I and II, the experts were first asked to rate their preference for each strategy level on a scale from 1 (least preferred) to 7 (most preferred) . Subsequently, they were asked to rate, for each strategy, the importance of the differences between the most-preferred and the least-preferred levels on a scale from 1 (not important) to 7 (extremely important) . In Section III, experts were asked to indicate to what extent they prefer one combination of levels from two or three different strategies over another combination . Pairs of partial profiles were to some extent selected by ACA based on the expert’s ratings in the first two sections. In this graded paired comparison (Section III), each respondent saw pairs of partial profiles and rated them on a scale from 1  to 9  .2) from these regressions [In ACA’s Section IV, respondents were asked to rate the likelihoods that each of five combinations of six strategy levels would give maximum performance on a scale from 0 (definitely would not contribute) to 100 (definitely would contribute). The respondents’ estimate of maximum performance was elicited by asking for the maximum performance indicator value that they consider reasonable for 2015–2020 period, as a percentage of the past value  for all streams, on average. Percentages of past indicators were used because it was expected to be more difficult, even for the experts, to provide answers about future performance in absolute values. The reference to a maximum possible value was included to maintain the original set-up of ACA’s Section IV, in which a scale with more objective anchors is typically used. Section IV ratings were used for re-scaling (by means of OLS regression) the more or less arbitrarily scaled Section I/II/III contributions to logit transformed likelihood ratings . The intressions . In addiressions .Relative strategy importances were derived from the ACA-estimated individual utilities for each performance indicator in each of the three scenarios. That is, for each strategy, the difference between the utility of the most preferred and the least preferred level was expressed in terms of percentages , 54. TheNo experts dropped out during the Delphi study, which was concluded with a total of 16 relevant events distributed in three non-overlapping 2015–2020 scenarios for the honey business. Each event was placed in only one of the scenarios. The Delphi was concluded after two rounds, with an agreement of at least two thirds of the experts about the placing of an event in a scenario . This leFor the production growth indicator, the mean strategy-level utilities and the relative strategy importances were calculated for each scenario see . For insThe preferences for the strategy levels changed across the scenarios for production growth, however the most preferred level was generally stable across the scenarios. The only exception was the number of HACCP honey houses per 100 beekeepers. Having one HACCP honey house unit per 100 beekeepers was the preferred level in the pessimistic scenario but became less preferred than two HACCP honey house units per 100 beekeepers in the realistic and optimistic scenarios. The differences in the utilities of the levels for this strategy in each of the scenarios was large, meaning that the experts had similar views about the effects of the strategy levels: in scenarios with growing demand and qualified competition, having more certified capacity would contribute more to production growth. In eight of the remaining strategies, the utility of the preferred level increased as the scenario shifted from pessimistic to optimistic.For each scenario, the most important strategies for production growth were also identified . In the For the local value-added indicator, the mean strategy-level utilities and the relative strategy importances were also calculated for each scenario see . For insChanges in the preferences for strategy levels were also observed across the scenarios for local value-added. For four strategies, these changes were such that a strategy level was no longer preferred . The difference in the utilities of the second-most preferred and the most preferred strategy level was small for each scenario. For example, exporting 50% of the processed volume was the preferred strategy level in the realistic scenario (with utility 0.107), compared to the 75% strategy level (with utility 0.091) and the 100% strategy level (with utility -0.119). The difference in utilities of the 50% and 75% levels was small in the realistic scenario. This means that the experts were not completely sure about the difference in the effects of the two most-preferred strategy levels in the realistic scenario. In the optimistic scenario, the 50% strategy level was clearly preferred, with utility 0.218 versus utility -0.031 for the 50% level and utility -0.098 for the 100% strategy level. This pattern of perceptions among experts contributed to none of these four strategies being among the most important in any of the scenarios.For each scenario, the most important strategies for local value-added were also identified . In the Comparing the results of the two performance indicators, it is noteworthy that none of the top three strategies for production growth were among the top three for local value-added. As long as performance goals are not the same, it is expected that the strategies to reach them may also be different. Furthermore, consistency among experts was lower for local value-added than for production growth in all scenarios, as the experts were less familiar with the local value-added indicator.2 from the OLS regressions of the Section IV likelihood ratings on the Section I/II/III combined utilities was around 0.80, showing the high internal validity of the individual-level utilities in all scenarios. The intraclass correlation coefficient of utilities was also high, above 90% in all scenarios, expressing a strong agreement across experts in all scenarios  were considered relevant in the pessimistic scenario only. However, should this less likely event occur, these strategies should be considered. This shows how the results can be used to find appropriate strategies if an unlikely event occurs. A new conjoint study involving new scenarios may therefore not always be necessary to identify the importance of a specific strategy should an unlikely event occur.In addition to the significant events that shape the structure of the honey business in each scenario, feedbacks from the performance of the streams to conduct and to structure are expected. In a 5-year planning horizon, however, the effects of those feedbacks at the national or world level are not expected due to the small size of the selected streams. At the local level, however, feedback effects may be relevant and should be monitored by the chain participants as the streams implement and evaluate their strategies.Although the three honey streams in this study are located relatively close to each other and the group of strategies is the same across the streams, there may be relevant differences in their strategy levels in practice. For instance, it is much easier for the Santana do Cariri stream to sell a higher percentage of its production as monofloral honey then its counterparts due to the existence of a well-defined blossoming season for a clear honey-source flower .Once the most important strategies have been identified, it is still necessary to check for the alignment of those strategies with each other towards the prioritized performance goal . AlignmeAs a corollary to the results of this study, common upgrading strategies, such as those relying on product differentiation, are not the most recommended to all performance goals. Promising strategies are also frequently influenced by business scenarios. The influence of the dynamics of the business environment on promising strategies is revealed not only by changes in their importances across scenarios but also by comparison with past successful strategies.  showed, There are also strategies that rate among the top three in terms of their perceived contribution to performance in all three scenarios. These strategies are the so-called robust strategies, for which usefulness does not depend on the scenario. This is the case for ‘complimentary colony feeding’ for production growth, and ‘certification of honey as organic’ and ‘certification of honey as fair trade’ for local value-added. The common characteristic of these strategies is that they fit the traditional patterns of process (productivity improvements) and product (product differentiation) upgrading . This reThe use of upgrading typologies for value chain strategies, however, should be further discussed. The two types of upgrading, product and process, for which examples of robust strategies were found in this study both relate to established upgrading forms studied in the economics of innovation . These tIt is clear that the definition of upgrading would have to be expanded to include strategies that could possibly contribute to specific value chain stream goals in any business scenario. This finding supports the argument that upgrading should be viewed as searching for a “better deal” , to be pIn fact, extending the SCP framework to value chains brought three innovations to the value chain strategy literature: the integrated assessment of value chains provided by the relations between structure, conduct and performance; the explicit embeddedness in the territory where the segment of the value chain (the stream) is located; and the value chain stream  itself as the unit of analysis. The value chain SCP framework takes into account the concepts of governance and value distribution from GVC theory in its conduct categories. Moreover, the framework incorporates, from GPN theory, the concept of territorial embeddedness in its unit of analysis and in its structural categories, and the notion of competing geographies in its unit of analysis. Therefore, the value chain SCP framework combines the strengths  of leadiA priori, the implementation sequence of the strategies, nonetheless, depends on the degree of the contribution of the strategies to performance, rather than on the types of the strategies. This contrasts with the GVC theory, which expects a regular trajectory of strategy adoption, starting from process upgrading, to product, then to functional, and finally, to inter-chain upgrading [The application of the value chain SCP framework in distinct configurations of structure, conduct and performance also reveals that some traditional strategy upgrading types may be more adequate just towards certain performance goals. If the goal, for instance, is to increase local value-added, product upgrading strategies may be more appropriate. pgrading . Howeverpgrading , and notIn that regard, the value chain SCP framework assumes the adoption of a certain set of strategies by a stream, to be expressed as a combination of the strategies adopted by all firms in that stream. In practice, it is possible that firms in the same step of the stream follow very different, conflicting sets of strategies. Depending on the characteristics of the stream , those differences in the firms’ strategy sets may not be sustainable, because the stream capabilities and resources would be stretched too thin. In any case, the value chain SCP framework allows for those differences within the streams, as stream strategies can be expressed in percentages of adoption of a certain strategy . In practice, it is also possible that firms in different steps of the same stream engage in strategies that are beneficial to one, and at the expenses of the others. Adopting conflicting, divergent strategies  may not This study focused on the strategies that can be pursued by the value chains to improve their competitiveness and promote local development, moving beyond upgrading typologies. The value chain SCP framework is expected to be valuable for future research in the following areas: application of the value chain SCP framework to identify strategies for other value chain streams, identification of strategies for value chain streams to achieve socio-environmental goals in addition to economic goals, and the identification of structural limitations that deserve to be targeted by value chain development interventions.S1 Appendix(DOCX)Click here for additional data file.S2 Appendix(DOCX)Click here for additional data file.S1 Table(XLSX)Click here for additional data file.S2 Table(DOCX)Click here for additional data file.S3 Table(XLSX)Click here for additional data file.S4 Table(DOCX)Click here for additional data file.S5 Table(XLSX)Click here for additional data file.S6 Table(DOCX)Click here for additional data file.S7 Table(XLSX)Click here for additional data file.S8 Table(DOCX)Click here for additional data file.S9 Table(XLSX)Click here for additional data file.S10 Table(DOCX)Click here for additional data file.S11 Table(XLSX)Click here for additional data file.S12 Table(DOCX)Click here for additional data file.


The purpose of this study was to compare the effects of galvanic vestibular stimulation (GVS) on postural control for participants of different physical activity status (i.e. active and non-active). Two groups of participants were recruited: one group of participants who regularly practised sports activities , and one group of participants who did not practise physical and/or sports activities . They were compared in a reference condition  and four vestibular manipulation condition  lasting 20 seconds. The centre of foot pressure displacement velocities were compared between the two groups. The main results indicate that the regular practice of sports activities counteracts postural control disruption caused by GVS. The active group demonstrated better postural control than the non-active group when subjected to higher vestibular manipulation. The active group may have developed their ability to reduce the influence of inaccurate vestibular signals. The active participants could identify the relevant sensory input, thought a better central integration, which enables them to switch faster between sensory inputs. The vestibular system encodes self-motion information by detecting the position and the motion of the head in space (i.e. angular and linear accelerations), which contributes to the control of eyes movements and stabilisation of the gaze, the perception of body orientation, the control of posture and balance –4. The cWhen vestibular afferents are altered the CNS triggers mechanisms to compensate the alteration . VestibuIn a context where vestibular system is disrupted, postural control can be impaired . When a Galvanic vestibular stimulation (GVS) has been widely used as a sensory manipulation to alter vestibular afferents signal in order to understand how an individual counteracts the postural effects of the artificial vestibular stimuli ,36,37. TNumerous studies had analysed GVS effects on postural control in healthy or pathological participants ,41–47, oConcerning GVS, Balter et al.  showed tRegarding physical activity status, in order to take the analysis of postural behaviour in the context of GVS one step further, different current intensities and polarities should be studied. The aim was thus to compare the effects of GVS, with different intensities and polarities, on postural control for participants of different physical activity status. It would be interesting to choose an intensity slightly lower than Maitre et al.   and seventeen participants who did not practise sport (non-active group) were recruited. Age and anthropometrical data are presented in 2 target, 1.5 m in front of them at the height of their eyes.Participants were instructed to stand up  on a force plateform  with their eyes open fixed on a 4 cmThey underwent five conditions, each lasting 20 seconds and separated by 2 minutes. To avoid the training effect between the different conditions, one trial was carried out to adapt the participants to the exercise prior to recording. They were tested in a reference condition  and four sensory manipulation conditions. The main objective of these sensory manipulation conditions was to alter the vestibular information by means of GVS, which induces an asymmetry of vestibular activity .A transmastoïdal GVS was delivered by a constant-current stimulator  through two disposable electrodes . The electrodes were placed over each mastoid process, for a bilateral bipolar design. To avoid any local noxious sensation, an anaesthetic gel was applied onto each mastoid process. Participants were measured in two current intensities and two different polarity conditions for each current intensity:○GVS-R : an anode placed on the right mastoid process and a cathode placed on the left mastoid process.○GVS-L : an anode placed on the left mastoid process and a cathode placed on the right mastoid process.To avoid initial transients and anticipation behaviour recording at the onset of the sensory disturbance, each sensory manipulation was set up in a range of 5 seconds before the recording of postural sway data. The sensory stimulation was maintained throughout the entire duration of the data recording.X velocity (mm.s-1) and on the anterior-posterior axis in COPY velocity (mm.s-1). The absolute increases between REF and the other conditions were calculated for all the parameters:Posturowin software  calculated the centre of foot pressure (COP) displacement parameters that characterise the postural behaviour. We use the COP velocity since it has been considered the measure with the highest reliability among trials ,61. The Statistical analyses were performed with R statistical software. Age and anthropometrical data were compared using the non-parametric Wilcoxon-Mann-Whitney test to determine if there were differences between the two groups. The Friedman analysis of variance was performed to determine whether there were differences between the reference condition (REF) and the other conditions concerning all the parameters describing body sways. When significant treatment effect occurred, the pairwise Wilcoxon-Mann-Whitney post-hoc analyses with Holm-Bonferroni correction were used to test the difference among medians. The non-parametric Wilcoxon-Mann-Whitney test was also performed to determine if there were differences between the two groups concerning all the parameters describing body sways. Results were considered significant at the level of 5%.Means and standard deviations are presented with the medians in Tables Age and Anthropometrical data results indicated no difference between the two groups concerning age, height, weight and foot size .X and the COPY velocity increased for the 3 mA-R and the 3 mA-L conditions for the non-active group compared with the initial reference condition (REF). In addition, the COPX and the COPY velocities increased significantly more for the non-active group than the active group only for the 3 mA-R condition . The main results indicated that GVS altered postural control for the non-active group but not for the active group Tables  and 3. TThe aim of this study was to compare postural behaviour to different GVS intensities and polarities between active participants and non-active participants. Our hypothesis was confirmed since the results indicate that the main difference between the two groups of participants arise from the highest GVS intensity. The main differences between the two groups appeared when the anode was placed on the right mastoid process and the cathode was placed on the left mastoid process (i.e. GVS-R design). Moreover, the regular practice of sports activities counteracts postural control disruption of GVS for all current intensities and polarities. The physically active group demonstrated better postural control than the non-active group for the more intense vestibular manipulationX and the COPY velocities increased significantly more for the non-active group than the active group at 3 mA (for GVS-R and GVS-L). One can suggest that GVS had less effect on postural control for the active group than the non-active group thanks to their vestibular system adaptation and/or habituation capabilities to the stimulus and their ability to reweight sensory information. In this study, the most disruptive postural effects of GVS involve the highest GVS intensity which require important compensatory postural mechanisms in order to withstand the stimulation. Unlike the lowest intensity, the highest GVS intensity evidenced different postural abilities. Hence, it would exist a minimal GVS intensity to highlight different postural abilities between individuals which would be largely depends on the individuals’ postural skills.In the present study the COPThe active group likely took advantage from their experience of vestibular stimulation  to decrease the GVS effects on postural control. It has been shown that the repetition of the situation that provoke vestibular perturbation have been successfully used to alleviate disorienting effects of the situation  . Sports The CNS interprets bipolar GVS signal as a real head movement (i.e. head rotation) in space arising from an unplanned body movement . The balThe better postural performance achieved by the active group compared to the non-active group could also be linked to the ability of members of the active group to take advantage of other available sensory information. The active group may have developed better use of the non-disrupted sensory afferents  than the non-active group in the context of vestibular illusion. The active group was able to counteract GVS effects on postural control. No significant difference was found between the reference condition and the GVS conditions for the active group. Inversely, the non-active group was not able to counteract the influence of the 3 mA GVS effects on postural control. In the present study, we have to take into account the availability of the visual sensory system. Visual afferents are crucial elements, which enable the influence of vestibular stimulation to be reduced ,63,64. MAlthough visual information has greater influence than vestibular information during a visuo-vestibular conflict, the CNS may privilege an additional appropriate input in order to overcome the sensory conflict . It has X and COPY velocities between the two groups, at the 3 mA current intensity, exist only for the GVS design anode placed on the right mastoid process and cathode placed on the left mastoid process (i.e. GVS-R). This result might be linked to a more important postural effect of the GVS-R than the GVS-L. Different magnitude effects of GVS, depending on the electrode polarities, have been observed [It is interesting to note that the major differences of the COPobserved . These aobserved . Otherwiobserved –34. Quarobserved  have sugAnother intriguing result indicates that there is no difference between the active group and the non-active group in the reference condition. This result is not supported by the literature. Previous studies have demonstrated that, in general, sports practitioners sway less than control participants in unperturbed stance . The active group was composed of individuals who practise sport at regional or national level, which indicates an important difference of level when compared to the non-active group. They practise sports that strongly stimulate the vestibular system. It may be that, with experience, the active participants develop their ability to reduce the influence of inaccurate vestibular signals on postural regulation. The repeated vestibular stimulation induced by the regular practice of physical activity may have reduced the GVS effect on postural control. In addition, it could be that the active participants switch faster between sensory inputs, which suggests that they have better central integration and ability to identify the most relevant sensory input . Such a S1 Data(XLSX)Click here for additional data file.


Food impaction after impacted mandibular third molar extraction is a serious problem that should not be ignored. Incomplete suturing of the distal incision in the conventional method is the main cause of food impaction and delayed wound healing. The present study introduces a novel suture and drainage technology that requires hermetic suturing of the distal incision and rubber drainage for buccal drainage. 76 patients with horizontally/mesially impacted third molars  were enrolled in this prospective study. An impacted tooth on one side of each patient was extracted by occlusal drainage using the conventional method, whereas the other side tooth was extracted by buccal drainage using the novel method. The differences in wound healing, facial swelling, bleeding and dry socket between the two sides of each patient were compared postoperatively, and the trends for patient selection of the surgical method were also compared. The results indicated that buccal drainage had obvious advantages in wound healing and reduced the risk of postoperative bleeding, and most patients preferred this technique; there were no significant differences in postoperative facial swelling or pain. Thus, buccal drainage can solve the problem of long-term food impaction induced by traditional incision postoperatively and is worthy of clinical promotion. Impaction is also a potential cause of odontogenic cysts and tumours. Therefore, mandibular third molars are often extracted. Among the many types of mandibular third molar impaction, horizontally and mesioangularly impacted teeth are the most difficult to extract, regardless of the exceptional cases3. Complications may occur after extraction. Permanent nerve damage and serious infections are the most severe complications, but the rate of such complications is low5. Pain, trismus, dry socket and swelling are the most common postoperative complaints and influence the patients’ quality of life in the days6.Impacted teeth are most commonly found among mandibular third molars and lead to clinical diseases including pericoronitis, damage to adjacent teeth and temporomandibular disorders7. The wound should not be sutured too firmly, and the turning point of the incision, which is adjacent to the distal side of the second molar, is often left without stitching, setting up a drainage system through the occlusal surface between the distal side of the second molar and the mesial side of the primary third molar8. Many experts believe that the creation of such a drainage pathway for inflammatory exudates helps to reduce facial swelling, pain and other postoperative complications10. The main drawback of sutureless techniques is that wound healing may be delayed. In addition, there may be a high potential for the formation of a wedge gap in relation to the adjacent second molar, which may cause food impaction8. We also found that patients treated with such a drain system often complain that they are unwilling to chew with the affected side because of concerns that food will enter the extraction socket. The disto-occlusal region with this type of drainage system takes much longer to heal than does the maxilla, and patients are extremely uncomfortable11. Actually, food more easily gets into the mandibular extraction wound under gravity, compared with the maxillary wounds. Thus, food impaction is a serious clinical problem after the mandibular impacted third molar extraction, except for pain, trismus, dry socket and other common postoperative complaints, and is worthy of attention. However, few publications refer to this situation, and doctors seldom discuss how to solve this problem.Suturing is necessary during the extraction of impacted mandibular third molars and is aimed at recovering the soft tissues for better healing. Furthermore, suturing reduces postoperative bleeding and narrows the extraction socket, which can prevent food from entering into it and protect the blood clotsConsequently, we propose a new set of suture and drainage methods, named buccal drainage. The aim of the study is that such a method can solve the long standing problem of food impaction and delayed wound healing and does not increase the risk of relevant postoperative complications.To address the research purpose, a prospective study was conducted. Patients with horizontal/mesioangular impacted mandibular third molars who visited the Department of Stomatology of Tongji Hospital from 2014.08 to 2016.08 were included in this study.Inclusion criteria: ① The molars were horizontally/mesioangularly impacted on both sides, and all teeth were partially or completely covered by mucosa; ② The region, size and resistance distribution of the bilaterally impacted molars were similar; ③ The patients were in good medical condition, without local inflammation; ④ All patients were treated with the traditional method on one side and the new technique on the other side; ⑤ All patients had complete medical records and follow-up records, and they could clearly remember the relevant complications after the tooth extraction. ⑥ This is a double blind study with the patients have no knowledge at which site is which.Our study was approved by the Ethics Committee of Huazhong University of Science and Technology, and all of the patients signed informed consent forms. All methods were performed in accordance with the relevant guidelines and regulations.All patients received one-time block anaesthesia in the inferior alveolar nerve, lingual nerve and buccal nerve using a 2% lidocaine hydrochloride  anaesthetic solution. Terminal infiltration of the buccal fold and distal incision region was also performed using primacaine with adrenaline.One surgeon operated on all cases. All patients had their impacted molars on one side extracted with the traditional method, and after 1~4 weeks, they had their impacted molars on the other side extracted with the new method. All of the incisions were designed as a triangular flap.The mesio-buccal incision started from the mesio-buccal or disto-buccal axial angles of the adjacent tooth and was at a 45° angle with the gingival margin. The incision moved downward and forward but did not surpass the bottom of the transitional channel. The distal incision started from the middle point of the second molar’s distal gingival margin and extended postero-laterally. The incision did not deviate to the lingual side and was long enough to expose the buccal and distal bone surfaces after flap surgery. Then, the molar mesioangular dental crowns were split with dental high-speed turbine handpieces. In suturing, we ordinarily placed one stitch in the mesio-buccal incision and another stitch in the distal incision, and we added one more stitch in both regions if necessary. The mesio-occlusal region of the third molar was left unstitched for drainage Fig. .Figure 1The mesio-buccal incision started from the disto-buccal aspect of the second molar region, and not the mesio-buccal region of the adjacent tooth, for successful drainage. Its distal incision was equal to that in the traditional method. In suturing, we first firmly stitched the distal incision with at least two stitches. The strip emerged from the buccal incision, which was only sewed for 1~2 stitches on two sides to fix the strip  to conduct a chi-square test. The data were statistically significant when P < 0.05. Because of the special design in this research, we compared the differences in the ratios of the patients’ preferences between the new method and the conventional method among different postoperative complications and surgical types.In total, 76 individuals were included in this study. Their age varied between 19 and 35 years, with an average of 25.6 years. The number of impacted mandibular third molars in these patients was 152.The new method had obvious advantages in wound healing. Seventy-two teeth were firmly stitched in the occlusal surface 1 week after the operation, and 4 teeth were not quite firmly stitched because of certain reasons, including suturing problems. All wounds treated with the new method healed 1 month after the operation. The distal parts of the second molar on the control sides showed wedged gaps of different sizes after 1 month postoperatively; only a few of them healed completely, and some of them still had not healed even half a year after the operation.Regarding postoperative facial swelling, 57 of the patients showed no differences between the two sides; the ratio was 57/76. Eleven of them believed the traditional incisions were better, with less facial swelling, whereas 8 patients preferred the new method. The differences in the ratio of facial swelling between the new method and the conventional method were not significant (P > 0.05).Regarding postoperative bleeding, no patients exhibited massive haemorrhage after the operation. Twenty patients said they bled less with the new method, and 4 patients supported the traditional method. Fifty-two patients found no differences between the two methods. The differences in the ratio of bleeding between the new method and the conventional method showed obvious statistical significance (P < 0.001).Only 2 patients exhibited suspected dry socket on the control side after the operation and recovered quickly after appropriate treatment. As to trismus, all of the patients had nearly normal opening mouth after 7 days. None of the patients suffered nerve injury and evident pain in this study.Finally, 68 patients supported the new method and were concerned about food residues in the distal part of the traditional incisions and feelings of discomfort. Four patients found no differences between the two methods, and only 4 patients preferred the traditional method. The results are shown in Fig. 8. This situation occurs because the traditional drainage system is placed in the disto-occlusal region of the second molar, which causes an incompletely healed wedged gap for a long period. Food impaction disappears only when the wound is completely healed. Food impaction is simply a clinical manifestation of incomplete wound healing, especially with respect to the disto-occlusal incision. In our study, we transferred the drainage channel from the occlusal surface to the buccal surface, which improved the healing effect of the disto-occlusal incision and prevented food from entering. In this way the chewing function on the affected side could recover as soon as possible, and the patients felt comfortable after the operations, without experiencing food impaction.There are many types of complications after impacted tooth extraction, including the commonly known bleeding, infection, nerve injury and dry socket. Furthermore, patients can feel quite uncomfortable postoperatively, and they dare not use the affected side to chew, due to concerns regarding food entering the extraction woundet al. confirmed that the triangular flap design is associated with patients consuming the least painkillers2. Thus, we adopted the triangular flap for each impacted molar extraction, which was also widely used clinically. The traditional method drains from the gap on the distal region of the second molar, and the draining effect is good because the gap is usually wide. The most concerning problem of the new method is postoperative swelling, and we found no difference during clinical observations. We believe that is because of the advantage of the drainage posture. The drainage strip is placed under the dental crown, and such a posture is good for effective drainage under gravity and make ups the shortage of the drainage gap compared with the traditional method. Specially, the buccal incision of the new method must be performed in the distal region of the second molar, preferably clinging to the extraction wound, which can maximum the drainage effect. If the buccal incision is not placed in the distal region of the adjacent molar, then a portion of the drainage strip will cling to the buccal bone surface of the mandible, which will lengthen the drainage distance, narrow the drainage space, and reduce the drainage effect.There are many styles of flap design in the removal of impacted mandibular third molars; however, there are very few specific data available from the literature regarding postoperative flap-related discomfort. Grossi et al. reported lower swelling in the group with a partial closure of the wound compared with complete closure of the wound, and they did not find differences regarding trismus or pain8. Maria et al. found a lower level of postoperative variables in the group with a secondary closure, as well as a greater level of oedema and the presence of haematomas in the group with a complete closure12. Such research confirms that a drain is imported in impacted tooth extraction and that completely suturing the incision without a suitable drainage pathway should not be adopted clinically, which was the same as our clinical experience. However, some researchers have evaluated the role of the suture technique in relation to postoperative complications and concluded that there are no significant differences between complete closure and a one-knot in the corner of the buccal incision of the triangular flap, which uses the buccal relief incision for drainage without a drain strip13. Many experts have confirmed that the use of a drain strip can reduce postoperative facial swelling and has no effect on pain or trismus16. Because the gap between the buccal flap and bone surface is extremely narrow even though the buccal incision was partially sutured when there was no use of a drain strip, we believe the partial suturing of the buccal-relieving incision had no evident effect on swelling compared with completely suturing, which can also explain the results we mentioned above. The core of our research was to change the drainage pathway from the occlusal surface to the buccal surface using a drain strip, which can create an adequate gap between the buccal flap and the bone surface for drainage.Relevant clinical research already exists. Bello The new method showed better haemostasis than did the traditional method because of the firm occlusal suture. Four patients preferred the traditional method, and we believe that was because their incisions extended to the bottom of the vestibular groove and the extraction difficulty of the control side was obviously greater, as impacted molars on two different sides do not always present in a similar fashion. The buccal incisions were not firmly sutured and therefore bled much, which reminds us that we should not make too-long buccal incisions, which are not allowed to surpass the bottom of the vestibular groove.6. By using the new method, we can maximally protect the blood clot and prevent external irritants with a firmly occlusal suture. We believe that the new method can reduce the incidence of dry socket compared with the traditional method in large samples.Regarding dry socket, we did not find a significant difference between the two methods because of the limited number of cases. At present, we must reduce the surgery trauma, protect the blood clot, maintain oral hygiene and provide full rest postoperatively, to prevent dry socketAccording to our study, most patients were willing to use the new method. Only 4 patients held an adverse opinion. The inexperience of the doctor in using the new method was the main reason for patients who opposed the new method, and these patients also believed that the new method took too much longer to place the drainage strip compared with the traditional method, and the traditional incisions also healed well for a period of time. In the future, we need to find the most appropriate drainage device to reduce the operating time and improve the clinical result.Above all, the new method can solve the problem of a long-standing wedged gap in the disto-occlusal region of the second molar, make patients feel better, and reduce the incidence of postoperative bleeding and dry socket. Therefore, this technique is worthy of clinical promotion.